Shift control system for automatic transmission

Claim 2

In an automatic transmission for a vehicle having a speed changing gear unit and frictionally engaging means for accomplishing the selective engagement of the gears in the speed changing gear unit, an automatic shift control system comprising: a hydraulic actuating circuit including a shift valve for distributing the working fluid to said frictionally engaging means for controlling said frictionally engaging means; means for generating an engine torque responsive signal; means for generating a vehicle speed resPonsive signal; a first shift point computing circuit for computing one of said two signals or computing the relation between said two signals; a second shift point computing circuit having a gradient operating circuit and controlled by a gradient responsive signal generated by said gradient operating circuit; and a circuit for delivering an electrical output signal in response to the application of one of the outputs from said two computing circuits so as to actuate said shift valve.

Claim 3

In an automatic transmission for a vehicle having a speed changing gear unit and frictionally engaging means for accomplishing the selective meshing engagement of the gears in the speed changing gear unit, an automatic shift control system comprising: a hydraulic actuating circuit including a manual valve and a shift valve for distributing the working fluid to said frictionally engaging means for controlling said frictionally engaging means; means for generating an engine torque responsive signal; means for generating a vehicle speed responsive signal; a first shift point computing circuit for generating a signal when the relation between said two signals satisfies a predetermined condition; a second shift point computing circuit including a gradient operating circuit for generating a signal when said engine torque responsive signal, said vehicle speed responsive signal and the rate of variation of said vehicle speed responsive signal satisfy predetermined conditions, an operating circuit for generating a signal when said engine torque responsive signal and said vehicle speed responsive signal satisfy other predetermined conditions, and a bistable memory circuit for continuously generating an output signal in response to the application of an input signal to one of input terminals thereof and continuously inhibiting the delivery of the output signal in response to the application of an input signal to the other input terminal thereof so that the output signal can be continuously delivered from said bistable memory circuit in response to the application of the output signal from said gradient operating circuit to one of said input terminals of said bistable memory circuit and the delivery of the output signal from said bistable memory circuit is continuously inhibited when the output signal from said operating circuit is applied to the other input terminal of said bistable memory circuit; and an OR circuit for delivering an output signal when one of the output signals from said first and second shift point computing circuits is applied thereto so as to actuate said shift valve.

Claim 4

In an automatic transmission for a vehicle having a speed changing gear unit and frictionally engaging means for accomplishing the selective meshing engagement of the gears in the speed changing gear unit, an automatic shift control system comprising: a hydraulic actuating circuit including a manual valve and a shift valve for distributing the working fluid to said frictionally engaging means for controlling said frictionally engaging means; means for generating an engine torque responsive signal; means for generating a vehicle speed responsive signal; a first shift point computing circuit for generating a signal when the relation between said two signals satisfies a predetermined condition; a second shift point computing circuit including a gradient operating circuit for generating a signal when said engine torque responsive signal, said vehicle speed responsive signal and the rate of variation of said vehicle speed responsive signal satisfy predetermined conditions, an operating circuit for generating a signal when said engine torque responsive signal and said vehicle speed responsive signal satisfy other predetermined conditions, and a bistable memory circuit for continuously generating an output signal in response to the application of an input signal to one of input terminals thereof and continuously inhibiting the delivery of the output signal in response to the application of an input signal to the other input terminal thereof so that the output signal can be continuously delivered from said bistable memory circuit in response to the application of the output signal from said gradient operating circuit to one of said input terminals of said bistable memory circuit and the delivery of the output signal from said bistable memory circuit is continuously inhibited when the output signal from said operating circuit is applied to the other input terminal of said bistable memory circuit; and an OR circuit for delivering an output signal when one of the output signals from said first and second shift point computing circuits is applied thereto so as to actuate said shift valve.

Claim 5

In an automatic transmission for a vehicle having a speed changing gear unit, frictionally engaging means for accomplishing the selective engagement of the gears of said speed changing gear unit, and control means connected operatively to said frictionally engaging means for actuating said frictionally engaging means, an automatic shift control system comprising: a manual valve having a first position for establishing a relatively high forward driving ratio and a second position for establishing a relatively low forward driving ratio; a shift valve disposed in a communication passage between said shift region setting valve and said frictionally engaging means for selectively actuating said frictionally engaging means; biasing means engaging one end of said shift valve for biasing said shift valve in a direction giving the high forward driving ratio; solenoid means engaging the other end of said shift valve for urging said shift valve in the other direction giving the low forward driving ratio in response to the supply of current thereto; shift signal control means determining the supply of the current and the interruption of the current supplied to said solenoid means depending on the running conditions of the vehicle so as to vary the said shift valve in the corresponding direction; and switch means disconnectably connecting an electrical power source with said shift signal control means so that, in the closed posItion of said switch means in the first position of said manual valve, said shift signal control means actuates said shift valve to give the high forward driving ratio as well as the low forward driving ratio, while in the open position of said switch means, said shift signal control means is unable to carry out its control operation and said biasing means for said shift valve solely gives the high forward driving ratio.

Claim 6

In an automatic transmission for a vehicle having a speed changing gear unit, frictionally engaging means for accomplishing the selective engagement of the gears of said speed changing gear unit, and control means connected operatively to said frictionally engaging means for actuating said frictionally engaging means, an automatic shift control system comprising: a manual valve having a first position for establishing a relatively high forward driving ratio and a second position for establishing a relatively low forward driving ratio; a shift valve disposed in a communication passage between said shift region setting valve and said frictionally engaging means for selectively actuating said frictionally engaging means; biasing means engaging one end of said shift valve for biasing said shift valve in a direction giving the high forward driving ratio; solenoid means engaging the other end of said shift valve for urging said shift valve in the other direction giving the low forward driving ratio in response to the supply of current thereto; shift signal control means determining the supply of the current and the interruption of the current supplied to said solenoid means depending on the running conditions of the vehicle so as to vary the said shift valve in the corresponding direction; and switch means disconnectably connecting an electrical power source with said shift signal control means so that, in the closed posItion of said switch means in the first position of said manual valve, said shift signal control means actuates said shift valve to give the high forward driving ratio as well as the low forward driving ratio, while in the open position of said switch means, said shift signal control means is unable to carry out its control operation and said biasing means for said shift valve solely gives the high forward driving ratio.

Claim 7

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven member, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including shift valve means for selectively distributing fluid pressure from said source to said servos so as to change a gear ratio; solenoid means for operating said shift valve means; a source of voltage; means for generating a vehicle speed responsive signal; means for generating a throttle position responsive signal; a first shift point computing circuit including a differential amplifier for comparing said vehicle speed responsive signal and said throttle position responsive signal with each other and generating an output signal when the relation between said both signals satisfies a predetermined condition; a second shift point computing circuit including an operating circuit, a gradient operating circuit and a bistable memory circuit, said operating circuit setting said vehicle speed responsive signal and said throttle position responsive signal therein and generating an output signal when said signals satisfy a predetermined condition, said gradient operating circuit having a circuit for differentiating said vehicle speed responsive signal to compute an acceleration of the vehicle, setting said throttle position responsive signal, said vehicle speed responsive signal and a vehicle acceleration signal therein and generating an output signal when said signals satisfy a predetermined condition, and said bistable memory circuit being connected to receive the output signals of said operating circuit and said gradient operating circuit to establish a stable on-off state of output according to the states of said input signals; and an OR circuit connected to receive the output signals of said differential amplifier and said bistable memory circuit for generating an output signal of a logical sum of said input signals, the output of said OR circuit controlling energization of said solenoid means, whereby a gear ratio is changed according to the driven shaft responsive signal, the throttle position responsive signal and an acceleration of the vehicle.

Claim 8

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven member, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including shift valve means for selectively distributing fluid pressure from said source to said servos so as to change a gear ratio; solenoid means for operating said shift valve means; a source of voltage; means for generating a vehicle speed responsive signal; means for generating a throttle position responsive signal; a first shift point computing circuit including a differential amplifier for comparing said vehicle speed responsive signal and said throttle position responsive signal with each other and generating an output signal when the relation between said both signals satisfies a predetermined condition; a second shift point computing circuit including an operating circuit, a gradient operating circuit and a bistable memory circuit, said operating circuit setting said vehicle speed responsive signal and said throttle position responsive signal therein and generating an output signal when said signals satisfy a predetermined condition, said gradient operating circuit having a circuit for differentiating said vehicle speed responsive signal to compute an acceleration of the vehicle, setting said throttle position responsive signal, said vehicle speed responsive signal and a vehicle acceleration signal therein and generating an output signal when said signals satisfy a predetermined condition, and said bistable memory circuit being connected to receive the output signals of said operating circuit and said gradient operating circuit to establish a stable on-off state of output according to the states of said input signals; and an OR circuit connected to receive the output signals of said differential amplifier and said bistable memory circuit for generating an output signal of a logical sum of said input signals, the output of said OR circuit controlling energization of said solenoid means, whereby a gear ratio is changed according to the driven shaft responsive signal, the throttle position responsive signal and an acceleration of the vehicle.

Claim 9

An automatic shift control system as defined in claim 4, wherein said operating circuit comprises: a first throttle position setting operating circuit including reference voltage means connected to receive the throttle position responsive signal from a variable resistor and to conduct when the level of said signal exceeds that of the reference voltage; a first driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal from a frequency-DC voltage conversion circuit and to conduct when the level of said signal exceeds that of the reference voltage; and a first AND circuit connected to receive the output signals of said first throttle position setting operating circuit and said first driven shaft speed setting operating circuit for giving a logical product of said both input signals.

Claim 10

An automatic shift control system as defined in claim 4, wherein said gradient operating circuit comprises: a second throttle position setting operating circuit including reference voltage means coNnected to receive the throttle position responsive signal from a variable resistor and to conduct when the level of said signal exceeds that of the reference voltage; a second driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal and to conduct when the level of said signal exceeds that of the reference voltage; a low-pass filter connected to receive the driven shaft speed responsive signal for absorbing high frequency components of said speed signal; a differentiator connected with an output of said low-pass filter for differentiating the driven shaft speed responsive signal having an improved waveform, the output signal of said differentiator representing a differentiated value of the speed responsive signal or a signal representative of the vehicle acceleration; an acceleration setting operating circuit including reference voltage means and adapted to be energized when the acceleration signal exceeds a reference voltage; a delay circuit for receiving the output signal of said acceleration setting operating circuit and generating an output signal when the duration of the input signal is longer than a predetermined period of time; and a second AND circuit connected to receive the output signals of said second throttle position setting operating circuit, said second driven shaft speed setting operating circuit and said delay circuit for giving a logical product of said input signals.

Claim 11

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven member, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including shift valve means for selective distributing fluid pressure from said source to said servos so as to change a gear ratio; solenoid means for operating said shift valve means; a source of voltage; a variable resistor cooperating with a throttle valve to provide a voltage which varies with changes of the throttle position; a tachogenerator connected to a dirven shaft for producing an AC voltage which varies with the speed of the driven shaft; a frequency DC voltage conversion circuit connected to the tachogenerator for converting the AC voltage into a DC voltage so as to develop a signal voltage proportional to the speed of the driven shaft; a potentiometer for modifying the signal voltage proportional to the speed of the driven shaft; switching contacts arranged to be operated by a switching relay for alternately connecting one of the frequency-DC voltage conversion circuit and the potentiometer; a differential amplifier connected to receive a throttle position responsive signal from said variable resistor and a driven shaft speed responsive signal from said switching contacts for comparing the throttle position responsive signal with the driven shaft speed responsive signal, said switching relay being connected to an output lead of said differential amplifier; a first throttle position setting operating circuit including reference voltage means connected to receive the throttle position responsive signal from said variable resistor and to conduct when the level of said signal exceeds that of the reference voltage; a first driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal from said frequency-DC voltage conversion circuit and to conduct when the level of said signal exceeds that of the reference voltage; a first AND circuit connected to receive the output signals of said first throttle position setting operating circuit and said first driven shaft speed setting operAting circuit for giving a logical product of said both input signals; a second driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal and to conduct when the level of said signal exceeds that of the reference voltage; a low-pass filter connected to receive the drive shaft speed responsive signal for absorbing high frequency components of the driven shaft speed responsive signal; a differentiator connected with an output of said low-pass filter for differentiating the driven shaft speed responsive signal having an improved waveform, the output of said differentiator representing a differentiated value of the driven shaft speed responsive signal or a signal representative of the vehicle acceleration; an acceleration setting operating circuit including reference voltage means and adapted to be energized when the acceleration signal exceeds the reference voltage; a delay circuit for receiving the output signal of said acceleration setting operating circuit and generating an output signal when the duration of the input signal is longer than a predetermined period of time; a second AND circuit connected to receive the output signals of said second throttle position setting operating circuit, said second driven shaft speed setting operating circuit and said delay circuit for giving a logical product of said input signals; a bistable memory circuit connected to receive the output signals of the first AND circuit and the second AND circuit for establishing a stable on-off state of output according to the states of said input signals; and an OR circuit connected to receive the output signals of said differential amplifier and said bistable memory circuit for giving a logical sum of said both input signals, the output of said OR circuit controlling energization of said solenoid means, whereby a gear ratio is changed according to a change of an output siganl resulting from comparison between the driven shaft speed responsive signal and the throttle position responsive signal and also according to a change of an output signal resulting from comparison between a differentiated value of the driven shaft speed responsive signal, or a vehicle acceleration, and a reference vehicle acceleration.

Claim 12

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven member, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including shift valve means for selective distributing fluid pressure from said source to said servos so as to change a gear ratio; solenoid means for operating said shift valve means; a source of voltage; a variable resistor cooperating with a throttle valve to provide a voltage which varies with changes of the throttle position; a tachogenerator connected to a dirven shaft for producing an AC voltage which varies with the speed of the driven shaft; a frequency DC voltage conversion circuit connected to the tachogenerator for converting the AC voltage into a DC voltage so as to develop a signal voltage proportional to the speed of the driven shaft; a potentiometer for modifying the signal voltage proportional to the speed of the driven shaft; switching contacts arranged to be operated by a switching relay for alternately connecting one of the frequency-DC voltage conversion circuit and the potentiometer; a differential amplifier connected to receive a throttle position responsive signal from said variable resistor and a driven shaft speed responsive signal from said switching contacts for comparing the throttle position responsive signal with the driven shaft speed responsive signal, said switching relay being connected to an output lead of said differential amplifier; a first throttle position setting operating circuit including reference voltage means connected to receive the throttle position responsive signal from said variable resistor and to conduct when the level of said signal exceeds that of the reference voltage; a first driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal from said frequency-DC voltage conversion circuit and to conduct when the level of said signal exceeds that of the reference voltage; a first AND circuit connected to receive the output signals of said first throttle position setting operating circuit and said first driven shaft speed setting operAting circuit for giving a logical product of said both input signals; a second driven shaft speed setting operating circuit including reference voltage means connected to receive the driven shaft speed responsive signal and to conduct when the level of said signal exceeds that of the reference voltage; a low-pass filter connected to receive the drive shaft speed responsive signal for absorbing high frequency components of the driven shaft speed responsive signal; a differentiator connected with an output of said low-pass filter for differentiating the driven shaft speed responsive signal having an improved waveform, the output of said differentiator representing a differentiated value of the driven shaft speed responsive signal or a signal representative of the vehicle acceleration; an acceleration setting operating circuit including reference voltage means and adapted to be energized when the acceleration signal exceeds the reference voltage; a delay circuit for receiving the output signal of said acceleration setting operating circuit and generating an output signal when the duration of the input signal is longer than a predetermined period of time; a second AND circuit connected to receive the output signals of said second throttle position setting operating circuit, said second driven shaft speed setting operating circuit and said delay circuit for giving a logical product of said input signals; a bistable memory circuit connected to receive the output signals of the first AND circuit and the second AND circuit for establishing a stable on-off state of output according to the states of said input signals; and an OR circuit connected to receive the output signals of said differential amplifier and said bistable memory circuit for giving a logical sum of said both input signals, the output of said OR circuit controlling energization of said solenoid means, whereby a gear ratio is changed according to a change of an output siganl resulting from comparison between the driven shaft speed responsive signal and the throttle position responsive signal and also according to a change of an output signal resulting from comparison between a differentiated value of the driven shaft speed responsive signal, or a vehicle acceleration, and a reference vehicle acceleration.

Claim 13

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven emmber, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including a manual valve having a first position for establishing a relatively high forward speed ratio and a second position for establishing a relatively low forward speed ratio, a shift valve disposed in a communication passage between said manual valve and said servos for selectively supplying fluid pressure to said servos to change a gear ratio, spring means for biasing said shift valve in a direction establishing the high forward speed ratio, and solenoid means for urging said shift valve in the other direction establishing the low foraard speed ratio by overcoming the biasing force of said spring means when said manual shift valve is in said first position, said shift valve being biased by said spring means in the direction to establish the low forward speed ratio when said manual valve is in second position; a source of voltage; shift signal control circuits including means for generating a throttle position responsive signal voltage, means for generating a vehicle speed responsive signal voltage, a differential amplifier connected to receive the throttle position responsive signal voltage and to receive the vehicle speed responsive signal voltage for comparing said boTh signal voltages to generate an output signal by turning conductive when the throttle position responsive signal voltage is higher than the vehicle speed responsive signal voltage, and an amplifier for amplifying the output signal of said differential amplifier to energize solenoid means; and switch means disconnectably connecting said source of voltage with said shift signal control circuits, whereby when said switch means is in a closed position, the first position of said manual valve establishes the low forward speed ratio upon energization of said solenoid means by said shift signal control circuit and establishes the high forward speed ratio upon deenergization of the same, while when said switch means is in an open position, said shift signal control circuits do not operate and said solenoid means is in a deenergized state, whereas the first position of said manual valve establishes the high forward dpseed ratio and the second position thereof establishes the low forward speed ratio.

Claim 14

In an automatic transmission for a vehicle having a throttle controlled engine, a driven member, a fluid pressure source connected to and driven by said engine, gear means having gear elements which define plural torque delivery paths between said engine and said driven emmber, and fluid pressure operated servos for controlling relative motion of the gear elements of said gear means to change a gear ratio, an automatic shift control system comprising: hydraulic actuating circuits for interconnecting said servos and said pressure source including a manual valve having a first position for establishing a relatively high forward speed ratio and a second position for establishing a relatively low forward speed ratio, a shift valve disposed in a communication passage between said manual valve and said servos for selectively supplying fluid pressure to said servos to change a gear ratio, spring means for biasing said shift valve in a direction establishing the high forward speed ratio, and solenoid means for urging said shift valve in the other direction establishing the low foraard speed ratio by overcoming the biasing force of said spring means when said manual shift valve is in said first position, said shift valve being biased by said spring means in the direction to establish the low forward speed ratio when said manual valve is in second position; a source of voltage; shift signal control circuits including means for generating a throttle position responsive signal voltage, means for generating a vehicle speed responsive signal voltage, a differential amplifier connected to receive the throttle position responsive signal voltage and to receive the vehicle speed responsive signal voltage for comparing said boTh signal voltages to generate an output signal by turning conductive when the throttle position responsive signal voltage is higher than the vehicle speed responsive signal voltage, and an amplifier for amplifying the output signal of said differential amplifier to energize solenoid means; and switch means disconnectably connecting said source of voltage with said shift signal control circuits, whereby when said switch means is in a closed position, the first position of said manual valve establishes the low forward speed ratio upon energization of said solenoid means by said shift signal control circuit and establishes the high forward speed ratio upon deenergization of the same, while when said switch means is in an open position, said shift signal control circuits do not operate and said solenoid means is in a deenergized state, whereas the first position of said manual valve establishes the high forward dpseed ratio and the second position thereof establishes the low forward speed ratio.

Claim 15

An improved shift control for use in a vehicle having an engine and automatic transmission including a gear change unit capable of being selectively established in any one of a plurality of forward driving gear ratios, including at least respective lower and higher speed gear ratios, when shifted thereinto, said shift control comprising: load indicating means responsive to operational load characteristics of said vehicle for producing outputs indicative of variations of said load characteristics; first shift point computing means responsively coupled to said load indicating means for operative coupling to said gear change unit to establish a change from said lower to higher gear ratio when said output indicates a certain load characteristic; and second shift point computing means including a gradient operating circuit responsively coupled to said load indicating means for operative coupling to said gear change unit to establish a change from said higher to lower gear ratio when an output thereof indicates a certain load characteristic co-relative to a gradient exceeding a selected amount.

Claim 16

An improved shift control for use in a vehicle having an engine and automatic transmission including a gear change unit capable of being selectively established in any one of a plurality of forward driving gear ratios, including at least respective lower and higher speed gear ratios, when shifted thereinto, said shift control comprising: load indicating means responsive to operational load characteristics of said vehicle for producing outputs indicative of variations of said load characteristics; first shift point computing means responsively coupled to said load indicating means for operative coupling to said gear change unit to establish a change from said lower to higher gear ratio when said output indicates a certain load characteristic; and second shift point computing means including a gradient operating circuit responsively coupled to said load indicating means for operative coupling to said gear change unit to establish a change from said higher to lower gear ratio when an output thereof indicates a certain load characteristic co-relative to a gradient exceeding a selected amount.

Claim 17

A shift control system as in claim 9, wherein said load indicating means includes: vehicle speed and engine load responsive means; and means for coupling said responsive means to said vehicle for producing respective outputs indicative of vehicle speed and engine load.

Claim 18

An improved shift control system for use in a vehicle having an engine and automatic transmission including a gear change unit capable of being selectively established in any one of a plurality of forward driving gear ratios, including at least respective lower and higher speed gear ratios, when shifted thereinto, said shift control system comprising: automatic transmission shifting means for automatically shifting said transmission from one to another of said driving gear ratios based upon certain vehicle conditions; gradient responsive means for producing a given electrical output signal indicative of gradients exceeding a selected amount in accordance with operational load characteristics of the vehicle correlative to gradient; and means operatively coupled to said gradient responsive means and said automatic shifting means for causing said transmission, when it has been automatically shifted into said higher gear ratio by said shifting means, to be automatically shifted down from said higher to said lower gear ratio when said given electrical output occurs due to said selected amount of gradient being exceeded.

Claim 19

An improved shift control system for use in a vehicle having an engine and automatic transmission including a gear change unit capable of being selectively established in any one of a plurality of forward driving gear ratios, including at least respective lower and higher speed gear ratios, when shifted thereinto, said shift control system comprising: automatic transmission shifting means for automatically shifting said transmission from one to another of said driving gear ratios based upon certain vehicle conditions; gradient responsive means for producing a given electrical output signal indicative of gradients exceeding a selected amount in accordance with operational load characteristics of the vehicle correlative to gradient; and means operatively coupled to said gradient responsive means and said automatic shifting means for causing said transmission, when it has been automatically shifted into said higher gear ratio by said shifting means, to be automatically shifted down from said higher to said lower gear ratio when said given electrical output occurs due to said selected amount of gradient being exceeded.

Claim 20

An improved electrical shift control system for use in a vehicle of the type driven by an engine having an automatic transmission system including a speed change gear unit coupled to said transmission for selectively accomplishing shifting said speed change gear unit as between a plurality of gear ratios including at least lower and higher gear ratios, and a hydrauilc actuation circuit for controlling said speed change gear unit including distributor valVe means for selectively distributing a source of actuating fluid under pressure thereto, and an electrical shift control system for controlling the operation of said distributor valve means and hence the shift as between said gear ratios, said improved electrical shift control system comprising: vehicle responsive means including engine load responsive means and vehicle speed responsive means for producing output signals indicative of the respective conditions of said load and speed responsive means; first shift point computing means responsively coupled to said vehicle responsive means for producing selected outputs in response to the occurrence of respective relationships of said output signals for selectively activating said distributor valve means for shifting said gear unit as between said higher and lower ratios in accordance with said respective output signals; second shift point computing means responsively coupled to the vehicle responsive means and including a gradient operating circuit for producing an output indicative of gradients exceeding a selected amount in accordance with operational load characteristics of the vehicle correlative to said gradient; and means including circuit means responsively coupled to said gradient circuit for operatively controlling said distributor valve means in accordance with said gradient circuit output thereby modifying the shifting of said vehicle upon the encounter of gradients exceeding the selected amount.

Claim 21

An improved electrical shift control system for use in a vehicle of the type driven by an engine having an automatic transmission system including a speed change gear unit coupled to said transmission for selectively accomplishing shifting said speed change gear unit as between a plurality of gear ratios including at least lower and higher gear ratios, and a hydrauilc actuation circuit for controlling said speed change gear unit including distributor valVe means for selectively distributing a source of actuating fluid under pressure thereto, and an electrical shift control system for controlling the operation of said distributor valve means and hence the shift as between said gear ratios, said improved electrical shift control system comprising: vehicle responsive means including engine load responsive means and vehicle speed responsive means for producing output signals indicative of the respective conditions of said load and speed responsive means; first shift point computing means responsively coupled to said vehicle responsive means for producing selected outputs in response to the occurrence of respective relationships of said output signals for selectively activating said distributor valve means for shifting said gear unit as between said higher and lower ratios in accordance with said respective output signals; second shift point computing means responsively coupled to the vehicle responsive means and including a gradient operating circuit for producing an output indicative of gradients exceeding a selected amount in accordance with operational load characteristics of the vehicle correlative to said gradient; and means including circuit means responsively coupled to said gradient circuit for operatively controlling said distributor valve means in accordance with said gradient circuit output thereby modifying the shifting of said vehicle upon the encounter of gradients exceeding the selected amount.

Claim 22

An improved shift control system as in claim 12, wherein said circuit means is coupled to said first shift point computing means output and the output of said gradient circuit for delivering respective signals to said distributor valve means and comprises: bistable memory means, having two stable states, and responsively coupled to said gradient circuit for producing an output in one of its stable states in response to the output thereof indicative of the gradient exceeding the selected amount for activating said distributor valve, and producing no output in its other stable state in response to the gradient circuit output indicative of the gradient less than the minimum amount, and OR circuit means responsive to said bistable means and said first shift point computing means for activating said distributor valve to effect shifting of said gear unit in accordance with the presence or absence of an output of said OR means.

Claim 23

An improved shift control system as in claim 12 wherein said engine is throttle controlled and said load responsive means includes: means responsive to the degree of actuation of said throttle for establishing a signal indicative thereof.

Claim 24

An improved shift control system as in claim 12, wherein said vehicle speed responsive means includes: a generator coupled to the outout of the transmission and driven thereby for producing a variable output in accordance with the rotational speed thereof, indicative of vehicle speed.

Claim 25

An improved shift control system as in claim 12, for use with the said transmission system when the gear unit is shiftable between at least low, medium, and high gear ratios, the latter two being said lower and higher ratios, and said distributor valve means includes first and second distributor valves, said shift control system further including a third shift point computing means responsively coupled to said vehicle responsive means for providing outputs to control said first distributor valve, the combined outputs of said first and second shift point computing means being operable to control said second distributing valve.

Claim 26

An improved shift control system as in claim 16 wherein said second shift point computing circuit means further includes: second means responsive to the vehicle responsive means for producing selected outputs in response to the occurrence of respective different relationships thereof for effecting gear engagements different from those provided by said first distributor valve.

Claim 27

An improved shift controL system as in claim 17 further including: bistable circuit means having two stable states and responsively coupled to said gradient circuit for producing an output in one of its stable states in response to the output thereof indicative of the gradient exceeding said selected amount for activating said second distributor valve and producing no output in its other state in response to the gradient circuit output indicative of less than the selected amount, and OR circuit means responsive to said bistable means and said second shift point computing means for activating said second distributor valve to effect shifting of said gear unit in accordance with the presence or absence of an output of said OR means.

Claim 28

An improved shift control system as in claim 12, wherein said gradient response operating circuit includes: means responsively coupled to said vehicle responsive means for producing a first output upon the occurrence of a vehicle speed less than a selected minimum, an engine load greater than a selected maximum, said output being indicative of a road inclination greater than a selected degree and for further producing a second output in response to a respective engine load and vehicle speed respectively less than and greater than selected amounts for indicating level road conditions.

Claim 29

An improved shift control system as in claim 19 wherein said engine is throttle controlled and said load responsive means includes: means responsive to the degree of actuation of said throttle for establishing a signal indicative thereof and accelerometer means responsive to said speed responsive means for producing an output indicative of vehicle acceleration.

Claim 30

An improved shift control system as in claim 20 wherein said gradient responsive operating circuit means includes: first AND circuit means responsive to selected outputs of said vehicle responsive means including the vehicle speed response means, the accelerometer means, and the throttle responsive means, for producing an output for activating said bistable means to its first condition, and second AND circuit means responsive to selected outputs of said vehicle response means including the vehicle speed and throttle responsive means for activating said bistable means to its second condition.

Claim 31

An improved shift control system as in claim 21 further including OR circuit means coupled to said bistable means output and the second shift point computing means for producing an output when either of said means is producing its selected output for activating said distributor valve means.

Claim 32

An improved shift control system as in claim 20 wherein said first and second shift point computing means each include: shift point operating means responsive to said vehicle responsive means including the throttle degree responsive means and the vehicle speed detector for delivering an output in response to selected relationships of the signals therefrom.

Claim 33

An improved shift control system as in claim 23, wherein said shift point computing means each further include: means responsively coupled to said vehicle speed detector output, for providing a modulated version thereof, selection means for controlling the input of said shift point computing means for coupling the modulated version of said vehicle speed output thereto in response to the output of said shift point operating means, said modulated version of said vehicle speed output being attenuated so as to provide hystersis to said shift point computing means.

Claim 34

An improved shift control system as in claim 24, wherein shift point computing circuit includes a comparator for sensing the relative magntidues of the throttle position detector output and the vehicle speed detector output and producing its output in accordance with a preset relation.

Claim 35

an improved shift control system as in claim 12 further including a manual shift valve for distributing said fluid; and switch means for coupling an electrical power source to said control means, operAtively coupled to said shift valve for rendering said electrical control system inoperative to effect said automatic shifting of said gear unit when said manual shift valve is moved from an automatic to a manual mode.