Hydraulic system for controlling a gearbox

Claim 2

In a hydraulic control system for actuating a plurality of fluid pressure actuated devices for engaging different gear ratios of gearbox of an engine, comprising a tank containing control fluid, a pump drawing fluid from the tank and having an outlet, a control fluid line connected to the pump outlet, a pressure regulating valve connected to the line for regulating the value of the line fluid pressure, the line forming part of a circuit comprising: a change gear valve for connection to means for automatically operating the change gear valve, the change gear valve having a plurality of operative positions and being capable, depending on its operative position, of putting said line pressure in communication with a selected one of two of said devices, a first of said two devices being for engaging, upon actuation by said line pressure, a given ratio of the gearbox and a second of said two devices being for engaging, upon actuation by said line pressure, a ratio of the gearbox corresponding to the next higher ratio relative to said given ratio; a main relay valve interposed between the change gear valve and said first device, said relay valve comprising a slide member which is axially movable between a first position and a second position and has opposed faces, means for subjecting one of said faces to line pressure actuating said second device, when the change gear valve puts said line pressure in communication with said second device, and urging the slide member to said second position, means co-operative with the slide member for putting said line pressure in communication with and actuating said first device in said first position of the slide member and for interrupting communication of said line pressure with said first device in said second position of the slide member, and means for returning the slide member to said first position when said second device is not actuated and said line pressure is not exerted on said one face of the slide member; the provision in said hydraulic system of fluid Pressure means for applying to the slide member of the main relay valve an axial modulating force which is a function of the torque of the engine and the running speed of the engine, whereby, when changing under torque from said higher ratio to said given ratio, the time for displacing the slide member from said second position to said first position when the change gear valve stops the communication of the second device with said line pressure is adapted to the instantaneous torque of the engine and the instantaneous running speed of the engine.

Claim 3

In a hydraulic control system for actuating a plurality of fluid pressure actuated devices for engaging different gear ratios of a gearbox of an engine, comprising a tank containing control fluid, a pump drawing fluid from the tank and having an outlet, a control fluid line connected to the pump outlet, a pressure regulating valve connected to the line for regulating the value of the line fluid pressure, the line forming part of a circuit comprising: a change gear valve for connection to means for automatically operating the change gear valve, the change gear valve having a plurality of operative positions and being capable, depending on its operative position, of putting said line pressure in communication with a selected one of two of said devices, a first of said two devices being for engaging, upon actuation by said line pressure, a given ratio of the gearbox and a second of said two devices being for engaging, upon actuation by said line pressure, a ratio of the gearbox corresponding to the next higher ratio relative to said given ratio; a main relay valve interposed between the change gear valve and said first device, said relay valve comprising a slide member which is axially movable between a first position and a second position and has opposed faces, means for subjecting one of said faces to line pressure actuating said second device, when the change gear valve puts said line pressure in communication with said second device, and urging the slide member to said second position, means co-operative with the slide member for putting said line pressure in communication with and actuating said first device in said first position of the slide member and for interrupting communication of said line pressure with said first device in said second position of the slide member, and means for returning the slide member to said first position when said second device is not actuated and said line pressure is not exerted on said one face of the slide member; the provision in said hydraulic system of means supplying a fluid having a first pressure proportional to the running speed of the engine, means supplying a fluid having a second pressure proportional to the torque of the engine, a modulating valve connected to said line so as to be supplied with fluid at said line pressure and furnishing a modulated pressure from said line pressure, means for applying the modulated pressure to the slide member of the main relay valve so as to produce an axial modulating force on the slide member, the modulating valve comprising a slide member and means for subjecting the slide member of the modulating valve to two opposed pressures corresponding to said first pressure and said second pressure, whereby, when changing under torque from said higher ratio to siad given ratio, the time for displacing the slide member of the relay valve from said second position to said first position when the change gear valve stops the communication of the second device with said line pressure is adapted to the instantaneous torque of the engine and the instantaneous running speed of the engine.

Claim 4

In a hydraulic control system for actuating a plurality of fluid pressure actuated devices for engaging different gear ratios of a gearbox of an engine, comprising a tank containing control fluid, a pump drawing fluid from the tank and having an outlet, a control fluid line connected to the pump outlet, a pressure regulating valve connected to the line for regulating the value of the line fluid pressure, the line forming part of a circuit comprising: a change gear valve for connection to means for automatically operating the change gear valve, the change gear valve having a plurality of operative positions and being capable, depending on its operative position, of putting said line pressure in communication with a selected one of two of said devices, a first of said two devices being for engaging, upon actuation by said line pressure, a given ratio of the gearbox and a second of said two devices being for engaging, upon actuation by said line pressure, a ratio of the gearbox corresponding to the next higher ratio relative to said given ratio; a main relay valve interposed between the change gear valve and said first device, said relay valve comprising a slide member which is axially movable between a first position and a second position and has opposed faces, means for subjecting one of said faces to line pressure actuating said second device, when the change gear valve puts said line pressure in communication with said second device, and urging the slide member to said second position, means co-operative with the slide member for putting said line pressure in communication with and actuating said first device in said first position of the slide member and for interrupting communication of said line pressure with said first device in said second position of the slide member, and means for returning the slide member to said first position when said second device is not actuated and said line pressure is not exerted on said one face of the slide member; the provision in said hydraulic system of means supplying a fluid having a first pressure proportional to the running speed of the engine, means supplying a fluid having a second pressure proportional to the torque of the engine, a modulating valve connected to said line so as to be supplied with fluid at said line pressure and furnishing a modulated pressure from said line pressure, means for applying the modulated pressure to the slide member of the main relay valve so as to produce an axial modulating force on the slide member, the modulating valve comprising a slide member and means for subjecting the slide member of the modulating valve to two opposed pressures corresponding to said first pressure and said second pressure, whereby, when changing under torque from said higher ratio to siad given ratio, the time for displacing the slide member of the relay valve from said second position to said first position when the change gear valve stops the communication of the second device with said line pressure is adapted to the instantaneous torque of the engine and the instantaneous running speed of the engine.

Claim 5

In a hydraulic control system for actuating a plurality of fluid pressure actuated devices for engaging different gear ratios of a gearbox of an engine, comprising a tank containing control fluid, a pump drawing fluid from the tank and having an outlet, a control fluid line connected to the pump outlet, a pressure regulating valve connected to the line for regulating tHe value of the line fluid pressure, the line forming part of a circuit comprising: a change gear valve for connection to means for automatically operating the change gear valve, the change gear valve having a plurality of operative positions and being capable, depending on its operative position, of putting said line pressure in communication with a selected one of two of said devices, a first of said two devices being for engaging, upon actuation by said line pressure, a given ratio of the gearbox and a second of said two devices being for engaging, upon actuation by said line pressure, a ratio of the gearbox corresponding to the next higher ratio relative to said given ratio; a main relay valve interposed between the change gear valve and said first device, said relay valve comprising a slide member which is axially movable between a first position and a second position and has opposed faces, means for subjecting one of said faces to line pressure actuating said second device, when the change gear valve puts said line pressure in communication with said second device, and urging the slide member to said second position, means co-operative with the slide member for putting said line pressure in communication with and actuating said first device in said first position of the slide member and for interrupting communication of said line pressure with said first device in said second position of the slide member, and means for returning the slide member to said first position when said second device is not actuated and said line pressure is not exerted on said one face of the slide member; the provision in said hydraulic system of means supplying a fluid having a first pressure proportional to the running speed of the engine, means supplying a fluid having a second pressure proportional to the torque of the engine, means for subjecting the slide member, in the course of changing under torque from said higher ratio to said given ratio, to two opposed forces which correspond to respectively said first pressure and said second pressure, means being provided for suppressing the effect of said first pressure and second pressure in respect of conditions of operation of the system other than the conditions of changing under torque.

Claim 6

In a hydraulic control system for actuating a plurality of fluid pressure actuated devices for engaging different gear ratios of a gearbox of an engine, comprising a tank containing control fluid, a pump drawing fluid from the tank and having an outlet, a control fluid line connected to the pump outlet, a pressure regulating valve connected to the line for regulating tHe value of the line fluid pressure, the line forming part of a circuit comprising: a change gear valve for connection to means for automatically operating the change gear valve, the change gear valve having a plurality of operative positions and being capable, depending on its operative position, of putting said line pressure in communication with a selected one of two of said devices, a first of said two devices being for engaging, upon actuation by said line pressure, a given ratio of the gearbox and a second of said two devices being for engaging, upon actuation by said line pressure, a ratio of the gearbox corresponding to the next higher ratio relative to said given ratio; a main relay valve interposed between the change gear valve and said first device, said relay valve comprising a slide member which is axially movable between a first position and a second position and has opposed faces, means for subjecting one of said faces to line pressure actuating said second device, when the change gear valve puts said line pressure in communication with said second device, and urging the slide member to said second position, means co-operative with the slide member for putting said line pressure in communication with and actuating said first device in said first position of the slide member and for interrupting communication of said line pressure with said first device in said second position of the slide member, and means for returning the slide member to said first position when said second device is not actuated and said line pressure is not exerted on said one face of the slide member; the provision in said hydraulic system of means supplying a fluid having a first pressure proportional to the running speed of the engine, means supplying a fluid having a second pressure proportional to the torque of the engine, means for subjecting the slide member, in the course of changing under torque from said higher ratio to said given ratio, to two opposed forces which correspond to respectively said first pressure and said second pressure, means being provided for suppressing the effect of said first pressure and second pressure in respect of conditions of operation of the system other than the conditions of changing under torque.

Claim 7

A control system as claimed in claim 3, wherein the pressure regulating valve comprises a first chamber and means for selectively putting the chamber under pressure and connecting the first chamber to the tank according to the ratio engaged in the gearbox, the slide member of the main relay valve partly defines a second chamber and means are provided for connecting the first chamber to the second chamber.

Claim 8

A control system as claimed in claim 3, wherein the slide member of the main relay valve comprises a first radial face subjected to the action of said first pressure and a second radial face which faces in the opposite direction to the first radial face and has an area equal to the area of the first face and subjected to the action of said first pressure in respect of conditions of operation of the system other than the conditions of changing under torque from said higher ratio to said given ratio.

Claim 9

A control system as claimed in claim 3, wherein the pressure proportional to the running speed is the line pressure.

Claim 10

A control system as claimed in claim 6, wherein the pressure regulating valve comprises a chamber, means for selectively putting the chamber under pressure and connecting the chamber to the tank, depending on the ratio engaged in the gearbox, a piston slidably mounted in the chamber, a relatively stiff spring interposed between the slide member of the pressure regulating valve and the piston so as to introduce a static condition of regulation, when the chamber is under pressure, and vary the line pressure as a function of the running speed of the engine.

Claim 11

A control system as claimed in claim 3, comprising a pilot valve associated with the engine to supply a pilot fluid pressure which varies with the torque of tHe engine and corresponds to said pressure proportional to the torque.

Claim 12

A control system as claimed in claim 2, wherein the pressure proportional to the running speed is the line pressure.

Claim 13

A control system as claimed in claim 9, wherein the pressure regulating valve comprises a chamber, means for selectively putting the chamber under pressure and connecting the chamber to the tank, depending on the ratio engaged in the gearbox, a piston slidably mounted in the chamber, a relatively stiff spring interposed between the slide member of the pressure regulating valve and the piston so as to introduce a static condition of regulation, when the chamber is under pressure, and vary the line pressure as a function of the running speed of the engine.

Claim 14

A control system as claimed in claim 2 comprising a pilot valve assocated with the engine to supply a pilot fluid pressure which varies with the torque of the engine and corresponds to said pressure proportional to the torque.