Electric motor assisted power steering device

Claim 2

A control circuit (16) for an electrical power steering device of an automotive vehicle, comprising torque sensor means (1) for sensing a steering torque applied to a steering shaft to the vehicle by an operator, computation means (3) for generating a signal for controlling the direction and magnitude of power steering to be applied in response to the steering torque; characterised in that a separate additional direction determination means (17) is provided for duplicating determination of direction of the applied steering torque, and gating means (20a, 20b) for enabling control of the power steering only when both the separate additional direction determination means and the computation means indicate that the steering torque is in the same direction.

Claim 3

An electric motor assisted power steering device for an automotive vehicle which includes a steering wheel operated by an operator of the vehicle, at least one steered wheel, and a steering shaft operatively coupling the steering wheel to the steered wheel, said power steering device comprising: an electric motor capable of being turned in a first and a second direction by a supply of a current in a first and a second direction, respectively, said electric motor being operatively coupled to the steering shaft to provide an auxiliary torque to a right and a left direction by rotating in said and second direction, respectively; torque sensor means for detecting a steering torque of the steering shaft applied by the operator of the vehicle via the steering wheel; computation means, including a microcomputer coupled to an output of said torque sensor, for determining a direction of said auxiliary torque corresponding to said steering torque of the steering shaft applied by the operator, and for determining an amount of the auxiliary torque provided by said electric motor to the steering shaft, wherein said computation means outputs a first right direction signal when said steering torque applied by the operator is to the right direction and a first left direction signal when said steering torque is to the left direction; direction determiner circuit means, coupled to an output of said torque sensor means, for determining a direction of said auxiliary torque corresponding to said steering torque of the steering shaft applied by the operator, wherein said direction determiner circuit means outputs a second right direction signal when said steering torque is to the right direction and a second left direction signal when said steering torque is to the left direction; first logical product means, having a first and a second input coupled to an output of said computation means and an output of said direction determiner circuit means, respectively, for computing and outputting a logical product of said first and second right direction signals; second logical product means, having a first and a second input coupled to an output of said computation means and an output of said direction determiner circuit means, respectively, for computing and outputting a logical product of said first and second left direction signals; and motor current control means, coupled to outputs of said first and second logical product means and an output of said compution means, for controlling a current supplied to said electric motor to an amount corresponding to said amount of auxiliary torque determined by said computation means, wherein said motor current control means control a direction of current supplied to said electric motor to said first direction in response to an output from said first logical product means and to said second direction in response to an output from said second logical product means.

Claim 4

An electric motor assisted power steering device for an automotive vehicle which includes a steering wheel operated by an operator of the vehicle, at least one steered wheel, and a steering shaft operatively coupling the steering wheel to the steered wheel, said power steering device comprising: an electric motor capable of being turned in a first and a second direction by a supply of a current in a first and a second direction, respectively, said electric motor being operatively coupled to the steering shaft to provide an auxiliary torque to a right and a left direction by rotating in said and second direction, respectively; torque sensor means for detecting a steering torque of the steering shaft applied by the operator of the vehicle via the steering wheel; computation means, including a microcomputer coupled to an output of said torque sensor, for determining a direction of said auxiliary torque corresponding to said steering torque of the steering shaft applied by the operator, and for determining an amount of the auxiliary torque provided by said electric motor to the steering shaft, wherein said computation means outputs a first right direction signal when said steering torque applied by the operator is to the right direction and a first left direction signal when said steering torque is to the left direction; direction determiner circuit means, coupled to an output of said torque sensor means, for determining a direction of said auxiliary torque corresponding to said steering torque of the steering shaft applied by the operator, wherein said direction determiner circuit means outputs a second right direction signal when said steering torque is to the right direction and a second left direction signal when said steering torque is to the left direction; first logical product means, having a first and a second input coupled to an output of said computation means and an output of said direction determiner circuit means, respectively, for computing and outputting a logical product of said first and second right direction signals; second logical product means, having a first and a second input coupled to an output of said computation means and an output of said direction determiner circuit means, respectively, for computing and outputting a logical product of said first and second left direction signals; and motor current control means, coupled to outputs of said first and second logical product means and an output of said compution means, for controlling a current supplied to said electric motor to an amount corresponding to said amount of auxiliary torque determined by said computation means, wherein said motor current control means control a direction of current supplied to said electric motor to said first direction in response to an output from said first logical product means and to said second direction in response to an output from said second logical product means.

Claim 5

An electric motor assisted power steering device as claimed in claim 2, wherein: said torque sensor means outputs a voltage signal a level of which varies substantially in linear relationship with said steering torque of the steering shaft; and said direction determiner circuit means comprises an analog circuit which includes: first comparator means for comparing said level of the voltage signal of said torque sensor means with a first reference voltage level, said first comparator means outputting a signal when said level of the voltage signal exceeds said first reference voltage level; and second comparator means for comparing said level of the voltage signal of said torque sensor means with a second reference voltage level which is lower than said first reference voltage level, said second comparator means outputting a signal when said level of the voltage signal is below said second reference voltage level; wherein the output signals of said first and second comparator means constitute said second right and left direction signals outputted from said direction determiner circuit means.

Claim 6

An electric motor assisted type power steering device as claimed in claim 3, wherein said first and second reference voltages are selected at upper and lower end points, respectively, of a non-­sensitive region of the voltage signal of said torque sensor means in which said electric motor is not to be supplied with a current from said motor current control means.

Claim 7

An electric motor assisted power steering device as claimed in claim 3, wherein said analog circuit of said direction determiner circuit means further comprises a voltage divider consisting of a serial connection of a first, a second, and a third resistor coupled across a constant voltage source and a ground voltage, a junction point between said first and second resistor outputting said first reference voltage level and a junction point between said second and third resistors outputting said second reference voltage level, said first comparator means having a first input coupled to an output of said torque sensor means and a second input coupled to a junction point between said first and second resistors of said voltage divider, and said second comparator means having a first input coupled to an output of said torque sensor means and a second input coupled to a junction point between said second and third resistors of said voltage divider.

Claim 8

An electric motor assisted power steering device as claimed in any one of the claims 2 through 5, wherein said torque sensor means outputs a first and a second output signal each corresponding to the detected steering torque, said first output signal being supplied to said computation means and said second ouput signal being supplied to said direction determiner circuit means.

Claim 9

An electric motor assisted power steering device as claimed in claim 2, wherein said motor current control means comprises: pulse width modulation means, coupled to an output of said computation means, for mudulating a pulse width of a pulse train in accordance with the amount of the auxiliary steering torque determined by said computation means; and means, coupled to said pulse width moculation means, for controlling an on-time of the current supplied to said electric motor in response to a variation of the pulse width of said pulse train.

Claim 10

An electric motor assisted power steering device substantially and hereinbefore described with reference to Figures 5 and 6 or Figure 7 of the accompanying drawings.

Claim 11

An electric motor assisted power steering device substantially and hereinbefore described with reference to Figures 5 and 6 or Figure 7 of the accompanying drawings.