Hydraulic control device for belt-and-pulley type continuously variable transmission for a vehicle

• US 4,967,621 A
• Filed: 12/04/1989
• Issued: 11/06/1990
• Est. Priority Date: 08/21/1987
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Soga, Yoshinobu, Sugaya, Masami, Okawa, Susumu, Kouno, Katsumi
• Primary Examiner(s): Wright, Dirk
• Application Number:
  US07/443,845
• Time in Patent Office: 337 Days
• Field of Search: 74/866, 74/867, 74/868, 74/869
• US Class Current: 477/49
• CPC Class Codes: B60W 10/04 including control of propulsion units
• CPC Class Codes: B60W 10/101 Infinitely variable gearings
• CPC Class Codes: B60W 30/18 Propelling the vehicle
• CPC Class Codes: B60W 30/1819 Propulsion control with control means using analogue circuits, relays or mechanical links
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F16H 47/065 the mechanical gearing being of the friction or endless flexible member type
• CPC Class Codes: F16H 61/66 specially adapted for continuously variable gearings control of exclusively fluid gearing F16H61/38
• CPC Class Codes: F16H 61/66259 using electrical or electronical sensing or control means

Abstract

A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for a motor vehicle which has two variable-diameter pulleys connected by a belt, and two hydraulic actuators for changing effective diameters of the pulleys. The hydraulic control device includes a first and a second pressure regulating valve for adjusting a pressure of a fluid supplied from a hydraulic power source, respectively to a first line pressure and a second line pressure lower than the first line pressure, and a CVT shift control valve device for controlling a speed ratio of the transmission. The valve device includes a shift-direction switching directional control valve and a shift-speed control flow control valve. The directional control valve is operable between a first position in which one of the hydraulic actuators communicates with a first pressure line having the first line pressure, while the other actuator communicates with an atmosphere or a second pressure line having a second line pressure, and a second position in which the above-indicated one actuator communicates with the atmosphere or second pressure line while the other actuator communicates with the first pressure line. The flow control valve controls rates of flows of the fluid to and from the actuators, in response to an operation of the directional control valve.

Claims

1. A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for an automotive vehicle which includes a first and second rotating shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a transmission belt connecting the pair of pulleys, and a pair of hydraulic actuators for changing effective diameters of the variable-diameter pulleys, said hydraulic control device comprising:

a first and a second pressure regulating valve for adjusting a pressure of a working fluid supplied from a hydraulic power source, respectively to a first line pressure and a second line pressure which is lower than said first line pressure;

a first pressure line having said first line pressure;

a second pressure line having said second line pressure;

a CVT shift control valve device for controlling a speed ratio of said continuously variable transmission, said CVT shift control valve device including a shift-direction switching directional control valve and a shift-speed control flow control valve;

said directional control valve being operable between a second position in which a first of said pair of hydraulic actuators communicates with said first pressure line, while a second of said pair of hydraulic actuators communicates with said second pressure line, and a first position in which said first hydraulic actuator communicates with an atmosphere while said second hydraulic actuator communicates with said first pressure line; and

said flow control valve controlling a rate of supply flow of the fluid into one of said first and said second hydraulic actuator and a rate of discharge flow of the fluid from the other of said second and first hydraulic actuators, in response to an operation of said directional control valve.

2. A hydraulic control device according to claim 1, wherein said directional control valve includes a spool valve having a valve spool axially movable between opposite stroke ends thereof which correspond to said first and second positions, said directional control valve further including a solenoid valve for controlling a pilot pressure applied to one of opposite axial ends of said valve spool and thereby moving said valve spool.

3. A hydraulic control device according to claim 1, wherein said flow control valve includes a spool valve having a valve spool axially movable between opposite stroke ends thereof, to control said rate of supply flow of the fluid into said one or other hydraulic actuator or said rate of discharge flow of the fluid from said other or one hydraulic actuator, said flow control valve further including a solenoid valve for controlling a pilot pressure applied to one of opposite axial ends of said valve spool and thereby moving said valve spool.

4. A hydraulic control device according to claim 1, further comprising a switch valve connected to a first hydraulic actuator of said pair of hydraulic actuators which is provided on said first rotating shaft, and to said second pressure line, said switch valve applying to said first pressure regulating valve one of a pressure in said first hydraulic actuator and said second line pressure, which one pressure is higher than the other,

and wherein

said first pressure regulating valve regulating said first line pressure such that said first line pressure is nigher than the pressure received from said switch valve, by a predetermined amount.

5. A hydraulic control device according to claim 4, wherein said first pressure regulating valve includes:

a valve spool for connecting said first pressure line selectively to a third pressure line or a suction line, to thereby release the fluid from said first pressure line; and

a spring for biasing said valve spool toward a closed position thereof, said valve spool having a first pressure receiving surface which receives said first line pressure to bias said valve spool toward an open position thereof, a second pressure receiving surface which receives said pressure supplied from said switch valve to bias said valve spool toward said closed position, and a third pressure receiving surface which receives a throttle pressure representative of an opening angle of a throttle valve of the vehicle, to bias said valve spool toward said closed position.

6. A hydraulic control device according to claim 4, wherein said switch valve includes a valve spool which is axially movable between a first position thereof for applying the pressure in said first hydraulic actuator to said first pressure regulating valve, and a second position thereof for applying said second line pressure to said first pressure regulating valve, said valve spool having a first pressure receiving surface which receives said pressure in said first hydraulic actuator to bias said valve spool toward said first position thereof, and a second pressure receiving surface which receives said second line pressure to bias said valve spool toward said second position thereof.

7. A hydraulic control device according to claim 6, wherein said switch valve further includes a spring for biasing said valve spool toward said second position thereof.

8. A hydraulic control device according to claim 1, further comprising a speed-ratio sensing valve for sensing an actual speed ratio of said continuously variable transmission and generating a speed-ratio pressure representative of said actual speed ratio, and a limit valve for limiting an increase in said speed-ratio pressure, and wherein

said second pressure regulating valve consists of a hydraulically operated pressure regulating valve which regulates said second line pressure, based on said speed-ratio pressure.

9. A hydraulic control device according to claim 8, wherein said limit valve limits said increase in said speed-ratio pressure, in relation to a currently required output of an engine of the vehicle.

10. A hydraulic control device according to claim 9, wherein said limit valve changes an upper limit of said speed-ratio pressure, based on a throttle pressure representative of an opening angle of a throttle valve of said engine.

11. A hydraulic control device according to claim 10, wherein said limit valve includes a valve spool for selective connection and disconnection of a fluid passage communicating with said speed ratio sensing valve, to and from a drain, and further includes a spring for biasing said valve spool toward a closed position thereof, a thrust based on said speed-ratio pressure acting on said valve spool in a direction toward an open positon thereof, while a thrust based on said throttle pressure acting on said valve spool in a direction toward said closed position thereof, said valve spool being moved toward said open position to thereby limit said increase in said speed-ratio pressure, when the thrust based on said speed-ratio pressure exceeds a sum of the thrust based on said throttle pressure and a thrust of said spring.

12. A hydraulic control device according to claim 1, wherein said pair of hydraulic actuators consist of a first and a second hydraulic actuator provided on said first and second rotating shafts, respectively, and said directional control valve comprises a first spool valve which is operable between a first position in which the fluid in said first pressure line is fed into said first hydraulic actuator while the fluid in said second hydraulic actuator is discharged into said second pressure line, and a second position in which the fluid in said first pressure line is fed into said second hydraulic actuator while the fluid in said first hydraulic actuator is discharged into said atmosphere, and wherein

said flow control valve comprises a second spool valve which has a first operating position in which the supply and discharge flows of the fluid into and from said first and second hydraulic actuators which are selected by said first spool valve are not restricted, a second operating position in which said supply and discharge flows are restricted, and a third position intermediate between said first and second positions,

said hydraulic control device further comprising:

a first solenoid which is turned on to place said first spool valve in said first position for increasing the speed ratio of the continuously variable transmission, and which is turned off to place the first spool valve in said second position for decreasing said speed ratio, and

a second solenoid which is turned on to place said second spool valve in said first position for increasing a rate of change of said speed ratio, and which is turned off to place said second spool valve in said second position for decreasing said rate of change of said speed ratio.

13. A hydraulic control device according to claim 12, wherein said CVT shift control valve device further comprises:

a first solenoid valve which includes said first solenoid, and which produces a pilot pressure which is applied to a valve spool of said first spool valve to place the first spool valve in said second position when said first solenoid is off; and

a second solenoid valve which includes said second solenoid, and which produces a pilot pressure which is applied to a valve spool of said second spool valve to place the second spool valve in said second position when said second solenoid is off.

14. A hydraulic control device according to claim 1, further comprising:

a by-pass passage which connects one of said pair of hydraulic actuators and said second pressure line and which includes a restrictor; and

a check valve provided in said by-pass passage, said check valve permitting a flow of the fluid through said by-pass passage in a direction toward said one hydraulic actuator while inhibiting a flow of the fluid through said by-pass passage in a direction toward said second pressure line.

15. A hydraulic control device according to claim 1, wherein said flow control valve includes a valve housing having a cylindrical bore and a plurality of ports formed therein, and a valve spool slidably received in said cylindrical bore for controlling said rates of supply and discharge flows of the fluid, said valve spool including a plurality of lands for opening and closing said ports, one of said valve housing and each of said lands having at least one cutout for permitting a gradual change in said rates of supply and discharge flows of the fluid through said ports as said valve spool is axially moved.

16. A hydraulic control device according to claim 15, wherein said at least one cutout is selected from a group consisting of a tapered end portion of said each land, at least one V-shaped notch formed in said each land, and a stepped cutout formed in said each land.

17. A hydraulic control device according to claim 15, wherein said at least one cutout is selected from a group consisting of at least one tapered notch, at least one V-shaped notch and a stepped cutout which are formed in a portion of an inner circumferential surface of said cylindrical bore which slidably engages said each land.

18. A hydraulic control device according to claim 1, wherein the fluid in said first pressure line is fed into said one hydraulic actuator and the fluid in said other hydraulic actuator is discharged into said second pressure line, while a third pressure line is provided for purposes which include lubrication of a power transmitting system which includes said continuously variable transmission, said second pressure line being provided downstream of said first pressure line, said third pressure line being provided downstream of said first pressure line and in parallel with said second pressure line, said third pressure line having a third line pressure, said hydraulic control device further comprising:

a third pressure regulating valve for establishing said third line pressure such that said third line pressure is lower than said first line pressure.

19. A hydraulic control device according to claim 18, wherein said first pressure regulating valve consists of a pressure relief type pressure regulating valve which releases the fluid from said first pressure line into said third pressure line, and said second pressure regulating valve consists of a pressure reducing type pressure regulating valve which reduces said first line pressure to said second line pressure, said third pressure regulating valve consisting of a pressure relief type pressure regulating valve which releases the fluid from said third pressure line into a drain.

20. A hydraulic control device according to claim 18, wherein said first pressure regulating valve adjusts said first line pressure, based on a pressure which represents a currently required output of the vehicle, and a higher one of said second line pressure and a pressure in a first hydraulic actuator of said pair of hydraulic actuators which is provided on said first rotating shaft, such that said pair of hydraulic actuators have a thrust ratio that permits an actual speed ratio of said continuously variable transmission to coincide with a determined target speed ratio.

21. A hydraulic control device according to claim 18, wherein said second pressure regulating valve adjusts said second line pressure, based on a currently required output of the vehicle and a speed ratio of the continuously variable transmission, such that said transmission belt has a minimum tension required to transmit a torque that is required to provide said currently required output.

22. A hydraulic control device according to claim 21, wherein said second pressure regulating valve consists of a hydraulically operated pressure regulating valve which adjusts said second line pressure, based on a pressure representative of said currently required output of the vehicle and a pressure representative of the speed ratio of the continuously variable transmission.

23. A hydraulic control device according to claim 21, wherein said second pressure regulating valve consists of a pressure regulating servo valve which is electrically controlled based on a signal representative of said currently required output of the vehicle and a signal representataive of the speed ratio of the continuously variable transmission.

24. A hydraulic control device according to claim 18, wherein said third pressure regulating valve operates to maintain said third line pressure at a predetermined constant level.

25. A hydraulic control device according to claim 1, wherein said first pressure regulating valve includes a valve spool which is movable in a pressure-increasing direction to increase said first line pressure, and in a pressure-decreasing direction to decrease said first line pressure, said valve spool having a first pressure receiving surface which receives said first line pressure to produce a first thrust for biasing said valve spool in said pressure-decreasing direction, and a second pressure receiving surface which receives a highest one of pressures in said pair of hydraulic actuators and said second line pressure, to produce a second thrust for biasing said valve spool in said pressure-increasing direction.

26. A hydraulic control device according to claim 25, wherein said first pressure regulating valve further has a third pressure receiving surface which receives a pressure representative of a currently required output of an engine of the vehicle, to produce a third thrust for biasing said valve spool in said pressure-increasing direction, said first pressure regulating valve further including a return spring for producing a fourth thrust for biasing said valve spool in said pressure-increasing direction, said first line pressure being determined by an equilibrium position of said valve spool in which said first thrust is balanced with a sum of said second, third and fourth thrusts.

27. A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for an automotive vehicle which includes a first and a second rotating shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a transmission belt connecting the pair of pulleys, and a pair of hydraulic actuators for changing effective diameters of the variable-diameter pulleys, a first line pressure and a second line pressure being applied to one and the other of said pair of hydraulic actuators, respectively, so as to control a speed ratio of said continuously variable transmission, said hydraulic control device comprising:

a first pressure line having said first line pressure;

a second pressure line having said second line pressure;

a switch valve connected to a first hydraulic actuator of said pair of hydraulic actuators which is provided on said first rotating shaft, and to said second pressure line, said switch valve generating as an output pressure thereof a higher one of a pressure in said first hydraulic actuator and said second line pressure; and

a first pressure regulating valve for adjusting said first line pressure such that said first line pressure is higher than said output pressure by a predetermined amount.

28. A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for an automotive vehicle which includes a first and a second rotating shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a transmission belt connecting the pair of pulleys, and a pair of hydraulic actuators for changing effective diameters of the variable-diameter pulleys, a first line pressure and a second line pressure being applied to one and the other of said pair of hydraulic actuators, respectively, so as to control a speed ratio of said continuously variable transmission, said hydraulic control device comprising:

a first pressure line having said first line pressure;

a second pressure line having said second line pressure, for establishing an optimum tension of said transmission belt;

a speed-ratio sensing valve for sensing an actual speed ratio of said continuously variable transmission and generating a speed-ratio pressure representative of said actual speed ratio;

a hydraulically operated pressure regulating valve for regulating said second line pressure, based on said speed-ratio pressure, such that said second line pressure decreases with an increase in said actual speed ratio of said transmission; and

a limit valve for limiting an increase in said speed-ratio pressure of said speed-ratio sensing valve, so that a decrease in said second line pressure is limited when said actual speed ratio of said transmission exceeds a predetermined limit.

29. A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for an automotive vehicle which includes a first and a second rotating shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a transmission belt connecting the pair of pulleys, and a pair of hydraulic actuators for changing effective diameters of the variable-diameter pulleys, a working fluid in a first pressure line being fed into one of said pair of actuators and the fluid in the other hydraulic actuator being discharged into a second pressure line, while a third pressure line is provided for purposes which include lubrication of a power transmission system which includes said continuously variable transmission, said hydraulic control device comprising:

a first pressure regulating valve for regulating a first line pressure which is applied to said one hydraulic actuator through said first pressure line;

a second pressure regulating valve provided downstream of said first pressure regulating valve, said second pressure regulating valve regulating a second line pressure in said second pressure line, for establishing an optimum tension of said transmission belt, based on an actual speed ratio of said continuously variable transmission and a required amount of torque transmitted by said transmission, such that said second line pressure is lower than said first line pressure and decreases with a decrease in said required amount of torque; and

a third pressure regulating valve provided downstream of said first pressure regulating valve and in parallel with said second pressure regulating valve, said third pressure regulating valve regulating a third line pressure in said third pressure line such that said third line pressure is lower than said first line pressure.

30. A hydraulic control device for controlling a belt-and-pulley type continuously variable transmission for an automotive vehicle which includes a first and a second rotating shaft, a pair of variable-diameter pulleys provided on the first and second shafts, respectively, a transmission belt connecting the pair of pulleys, and a pair of hydraulic actuators for changing effective diameters of the variable-diameter pulleys, said hydraulic control device comprising:

a first pressure line having a first line pressure;

a second pressure line having a second line pressure;

a CVT shift control valve device for controlling a speed ratio of said continuously variable transmission, such that a working fluid in said first pressure line is fed into one of said pair of hydraulic actuators while the fluid in the other hydraulic actuator is discharged into said second pressure line;

a pressure regulating valve including a valve spool which is movable in a pressure-increasing direction to increase said first line pressure, and in a pressure-decreasing direction to decrease said first line pressure; and

said valve spool having a first pressure receiving surface which receives said first line pressure to produce a first thrust for biasing said valve spool in said pressure-decreasing direction, and a second pressure receiving surface which receives a highest one of a pressure in said one of the hydraulic actuators and said second line pressure, to produce a second thrust for biasing said valve spool in said pressure-increasing direction, said second pressure receiving surface having an area smaller than that of said first pressure receiving surface.