JPH0678785B2 - Hydraulic control device for V-belt type continuously variable transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a V-belt type continuously variable transmission, and more particularly to a device for controlling a gear ratio when reversing.

Conventional technology and its problems Conventionally, in a V-belt type continuously variable transmission, a drive side pulley is provided with a hydraulic chamber for controlling a gear ratio, and a driven pulley is provided with a hydraulic chamber for imparting belt tension in which a line pressure is introduced. There is known a hydraulic control device in which the hydraulic pressure in the gear ratio control hydraulic chamber is controlled by a reduction ratio control valve to perform continuously variable gear shifting (Japanese Patent Laid-Open No. 59-62761).

In the case of the above hydraulic control device, the line pressure is supplied from the manual valve to the speed reduction ratio control valve during forward movement such as in the D and L ranges, and the manual valve shuts off the line pressure oil passage to the speed reduction ratio control valve during reverse movement. Therefore, the line pressure is not guided to the reduction ratio control valve. In other words, the hydraulic pressure in the gear ratio control hydraulic chamber is always drained during reverse, and the line pressure is guided only to the belt tension imparting hydraulic chamber, so the gear ratio of the continuously variable transmission is independent of the operation of the reduction ratio control valve. The minimum speed ratio (maximum reduction ratio) is maintained. Therefore, even if the electromagnetic valve of the reduction ratio control valve malfunctions, the gear ratio during reverse is always maintained at the minimum speed ratio, and fail-safe can be realized.

On the other hand, a V-belt type continuously variable transmission in which a hydraulic chamber for controlling the gear ratio is provided on the driven pulley and a thrust load device for applying belt tension to the drive pulley is also known, which is the reverse of the above-described configuration, is also known ( JP-A-61-10149). In this case, the maximum hydraulic pressure (eg line pressure) must be supplied to the hydraulic chamber of the driven pulley in order to always maintain the minimum speed ratio when reversing, so deceleration with a manual valve as in the above hydraulic control device. The method of shutting off the line pressure supply to the ratio control valve cannot be adopted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a V-belt type continuously variable transmission in which a driven side pulley is provided with a hydraulic chamber for controlling a gear ratio, and a pulley control valve at the time of backward movement. SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic control device for a V-belt type continuously variable transmission which is always maintained at the lowest speed ratio regardless of the above operation.

In order to achieve the above object, the present invention provides a driven side pulley with a hydraulic chamber for gear ratio control, and a pulley control valve for regulating the line pressure to the hydraulic chamber and outputting it as control hydraulic pressure. V
In the belt type continuously variable transmission, the pulley control valve is connected to a first input port through which the line pressure is always guided and a second output port of a manual valve through which hydraulic pressure is output when retreating and draining at other times. There is an input port and an output port connected to the hydraulic chamber, the output port is provided at an intermediate position between the first input port and the second input port, and the spool of the pulley control valve has the output port and the first port. The first input port or the second input port is selectively connected to each other.

That is, since the line pressure is guided to both the first input port and the second input port when retracting, the line pressure is always output from the output port regardless of the operating position of the pulley control valve, and the V-belt type The transmission is always maintained at the lowest speed ratio.

Description of Embodiments FIG. 1 shows an example in which the present invention is applied to a V-belt type continuously variable transmission with a direct coupling mechanism.
It is composed of a continuously variable transmission 30, a driven shaft 41, a starting clutch 60, a forward / reverse switching mechanism 63, a differential device 80 and an output shaft 82.

The crankshaft 10 of the engine is connected to the right end of the input shaft 13 via a flywheel 11 and a torsional damper 12 for absorbing torque fluctuations of the engine. An oil pump 14 driven by 13 is arranged. A clutch drum 16 of a wet direct coupling clutch 15 is spline-fitted to an intermediate portion of the input shaft 13, and a clutch hub 17 is coupled to a direct coupling drive gear 18 rotatably supported on the input shaft 13. Direct coupling clutch
Reference numeral 15 is for connecting the direct drive gear 18 to the input shaft 13 at the time of direct drive, but the continuously variable transmission 30 and the start clutch 60 are provided.
Also serves as an emergency start clutch when the car breaks down. Input shaft
An external gear 19 is integrally formed at the left end of 13, and the external gear 19 meshes with an internal gear 20 fixed to a drive shaft 31 of a continuously variable transmission 30 to reduce the driving force of the input shaft 13. It is decelerated and transmitted to the drive shaft 31.

The continuously variable transmission 30 includes a drive side pulley 32 provided on a drive shaft 31.
And a driven pulley 42 provided on the driven shaft 41, and a rubber or resin endless V-belt 54 frictionally driven between the pulleys. The drive-side pulley 32 has a fixed sheave 33 fixed to the drive shaft 31 and a movable sheave 34 that is movable in the axial direction and the rotation direction, and is provided with a torque cam device 35 for thrust generation provided behind the movable sheave 34 and a compression device. The spring 36 and the movable sheave 34 apply a thrust force required for torque transmission. The torque cam device 35 rolls a cam roller 40 between a cam surface 38 provided on the back surface of the movable sheave 34 and a cam surface 39 provided on the right side of a torque cam flange 37 fixed to the left end of the drive shaft 31. It is arranged as possible and generates thrust proportional to the input torque. The torque cam device 35 is arranged in a space formed by the cylinders 34a, 37a integrally projecting from the movable sheave 34 and the torque cam flange 37, in order to reduce wear of the cam roller 40 and the cam surfaces 38, 39 in this space. Lubricating oil such as grease is enclosed.

The driven pulley 42 also has a fixed sheave 43 fixed to the left end of the driven shaft 41 and a movable sheave 44 that is movable only in the axial direction by a ball spline 45, and a cylinder 46 is fixed behind the movable sheave 44. ing. A piston 47 fixed to the driven shaft 41 is slidably arranged inside the cylinder 46. One chamber partitioned by the piston 47 is a hydraulic chamber 48 for gear ratio control, and the other chamber is It is a sub-chamber 49 for canceling the centrifugal hydraulic pressure generated in the hydraulic chamber 48.
Supply and discharge of hydraulic oil to and from the hydraulic chamber 48 is performed via a hydraulic oil passage 50 provided at the shaft center of the driven shaft 41, and supply and discharge of lubricating oil to and from the sub chamber 49 is performed outside the hydraulic oil passage 50. It is performed through the formed lubricating oil passage 51. The hydraulic oil leaking from the hydraulic chamber 48 through the ball spline 45 is returned to the lubricating oil passage 51 through the drain oil passage 52 formed in the driven shaft 41, and the sub chamber 49 and the outside are separated by the diaphragm 53. Since it is sealed, there is no risk of oil leakage to the outside.

A wet starting clutch 60 is provided at the right end of the driven shaft 41. The clutch drum 61 of the starting clutch 60 is a driven shaft.
The clutch hub 62 is spline-fitted to 41, and the clutch hub 62 is connected to the spline hub 64 of the forward / reverse switching mechanism 63. The starting clutch 60 is always engaged when the vehicle is driven by the belt, is always disconnected when the vehicle is directly connected, and is gradually engaged by finely controlling the clutch hydraulic pressure when the vehicle is started. Above spline hub
A forward gear 65 and a reverse gear 66 are rotatably provided on both sides of 64, and one of the gears is connected to the spline hub 64 by a switching sleeve 67. An idle shaft 68 arranged in parallel with the driven shaft 41 is integrally formed with a reverse idle gear 69 that meshes with the reverse gear 66 and another reverse idle gear 70. The reduction shaft 71 is also arranged in parallel with the driven shaft 41, and a reduction gear 72 and a final reduction gear 73, which are integrally formed, are rotatably supported on the reduction shaft 71. The reduction gear 72 simultaneously meshes with the direct drive gear 18, the forward gear 65, and the reverse idle gear 70, and also serves as a direct drive gear. Final reduction gear
The numeral 73 meshes with the ring gear 81 of the differential device 80 to transmit the power to the output shaft 82.

The above-mentioned components are covered by the cases 1 and 2 and the cover 3, and in particular, the continuously variable transmission 30 is separated from the clutches 15 and 60 and the gear mechanism by the partition wall 2a of the case 2,
It communicates with the atmosphere through an air hole (not shown) provided in the. The cooling fins 55 are integrally formed behind the drive-side pulley 32 and the driven-side pulley 42 to enhance the air cooling effect.

In the V-belt type continuously variable transmission having the above structure, the direct coupling clutch 15, the direct coupling drive gear 18, the reduction gear 72, the final reduction gear 73, and the differential device 80 form a direct coupling drive path. Gear 20, continuously variable transmission 30, starting clutch 60,
The forward drive gear 65, the reduction gear 72, the final reduction gear 73, and the differential device 80 form a belt drive path (during forward movement). Then, the input shaft 13 and the output shaft 82 in the direct drive path
The direct transmission ratio between them is set to be substantially equal to the maximum speed ratio between the input shaft 13 and the output shaft 82 in the belt drive path.

FIG. 2 shows a hydraulic control device for controlling the driven pulley 42, the starting clutch 60 and the direct coupling clutch 15,
Is the first pressure regulating valve, 110 is the second pressure regulating valve, 120 is a manual valve,
130 is a forward / reverse switching valve, 140 is a forward / reverse switching piston, 150 is a pulley control valve, 160 is a clutch control valve, 170 is a controller including a microcomputer, 171 is a solenoid valve for pulley control, 172 is a solenoid valve for start control , 173 are solenoid valves for direct connection control.

The discharge hydraulic pressure of the oil pump 14 is guided to the right end port 101 and the intermediate port 102 of the first pressure regulating valve 100, and the right end port 10
The oil pressure of 1 causes the spool 103 to move to the left against the spring 104, and when the land 103a of the spool 103 reaches the position shown in the drawing, the intermediate port 102 and the drain port 105 communicate with each other, and the oil is supplied to the oil pump 14. It is returned to the suction side. Therefore, the spool 103 is balanced at this position, and the discharge hydraulic pressure of the oil pump 14 is adjusted to a predetermined line pressure P _L. The port 107 is a lubricating port for supplying lubricating oil to the input shaft 13 and the driven shaft 41. The signal oil pressure from the pulley control solenoid valve 171 or the output oil pressure from the port 159 of the pulley control valve 150 is selectively introduced into the input oil chamber 108 provided with the spring 104. For example, when the signal hydraulic pressure P ₁ of the solenoid valve 171 is introduced to the input oil chamber 108, the first pressure regulating valve 100 calculates the line pressure P _L by the signal hydraulic pressure P ₁ and the spring load S of the spring 104 as follows. Adjust the oil pressure to match the sum of ₁ .

P _L × A ₁ = P ₁ × A ₂ + S ₁ (1) In the above formula, A ₁ is the land 103b, 10 on the right side of the spool 103.
The difference in pressure receiving area of 3c, A ₂ is the pressure receiving area of the left land 103d.

Further, from the port 159 of the pulley control valve 150 to the input oil chamber 108, the oil pressure P ₀ (equal to the output oil pressure of the second pressure regulating valve 110 described later)
Is introduced, the first pressure regulating valve 100 regulates the line pressure P _L to a hydraulic pressure balanced with the sum of the hydraulic pressure P ₀ and the spring load S ₁ of the spring 104 as shown in the following equation.

P _L × A ₁ = P ₀ × A ₂ + S ₁ (2) When the hydraulic pressure P ₀ is applied to the input oil chamber 108, the hydraulic pressure P ₀ acts on the right end chamber 153 of the pulley control valve 150. In order to delay the above, an orifice 109 is provided between the pulley control solenoid valve 171 and the input oil chamber 108.

The second pressure regulating valve 110 has a spool 112 biased to the left by a spring 111, and the right end chamber 113 accommodating the spring 11 and the ports 114, 115 are drained. The line pressure regulated by the first pressure regulating valve 100 is guided to the input port 116, and the output port 117 communicates with the left end chamber 118 via the communication hole 112a provided inside the spool 112. Therefore, the hydraulic pressure P ₀ output from the output port 117 is regulated to a constant pressure balanced only by the spring load S ₂ of the spring 111 as shown in the following equation.

P ₀ × A ₃ = S ₂ (3) In the above expression, A ₃ is the pressure receiving area of the left land 112 b of the spool 112. The output hydraulic pressure P ₀ is input to the port 158 of the pulley control valve 150 and the solenoid valves 171 and 172.

The manual valve 120 works in conjunction with the shift lever to select P, R, N, D, L
It has a spool 121 which is operated at each position of, and by this spool 121, two output ports from an input port 122
The oil passage is selectively switched to 123,124. For example, in the D range, port 12 as shown
The line pressure is output from 3, and the port 124 is drained.
The L range is similar to the D range, and in the R range, the port 123 is drained and the line pressure is output from the port 124 as shown by the broken line. Further, in the P range, the land 121a closes the input port 122, and in the N range, the land 121a, 121b blocks the input port 122 from the output ports 123, 124, so that any output port is drained.

The forward / reverse switching valve 130 has a spool 132 biased to the right by a spring 131, and a left end portion of the spool 132 is engaged with a fork 133 for operating the switching sleeve 67 so as to be relatively movable by a predetermined stroke. is doing. The forward / reverse switching valve 130 is provided with four ports 134 to 137,
The line pressure is introduced into the ports 134 and 135 from the manual valve 120 at the time of retreat. The output port, port 136, is connected to the port 163 of the clutch control valve 160.
A line pressure is introduced to the 137 from the manual valve 120 when moving forward. In FIG. 2, the upper half of the forward / reverse switching valve 130 is in the backward direction and the lower half is in the forward direction.
It is output via 136, and when retreating, the line pressure is applied to port 13
It is output via 5,136. The spool 132 is a fork
Since it is accurately positioned in the forward and backward positions in conjunction with 133, each land on the spool 132 and ports 134-137
It is designed so that the positional relationship between and does not get out of order. For example, since the fork 133 is moving to the left when moving forward,
The snap ring 138 fixed to the end of the spool 132 is positioned by abutting against the fork 133 by the spring force of the spring 131, and when retracting, the fork 133 moves to the right as shown by the broken line, so that the right end port 134 Due to the acting line pressure, the stepped portion 132a of the spool 132 is positioned at a position where it comes into contact with the fork 133.

The forward / reverse switching piston 140 has a piston member 143 movable by hydraulic pressure acting on the left and right oil chambers 141, 142, and a fork shaft 144 for operating the fork 133 is connected to the piston member 143. A spring 145 for urging the piston member 143 toward the forward position is provided in the right chamber 142.
Is arranged in the right chamber 142, and the line pressure is guided from the output port 123 of the manual valve 120 to the left chamber 141 when the vehicle moves forward.
A line pressure is introduced from the output port 124 at the time of backward movement. The upper half of FIG. 2 shows the backward movement and the lower half shows the forward movement. The right chamber 142 in which the spring 145 is arranged is connected to the outside oil through a one-way valve 146, and when the R range is switched to the N or P range, the spring 145 moves the piston member 143 to the forward position. The operating time when operating is shortened.

The pulley control valve 150 has a spool 152 biased to the left by a spring 151, and a signal hydraulic pressure P ₁ is guided from a pulley control solenoid valve 171 to a right end chamber 153 accommodating the spring 151. Pulley control valve 150 has 6 ports 154--15
9, the port 154 (second input port) is connected to the output port 124 of the manual valve 120, the ports 155 (output port) and 156 are connected to the hydraulic chamber 48 of the driven pulley 42, and the port 157. (First input port) is always line pressure P _L
Has been led. Further, a constant pressure P ₀ is always guided to the port 158 from the second pressure regulating valve 110, and the port 159 is connected to the input oil chamber 108 of the first pressure regulating valve 100 as described above.

The position of the pulley control valve 150 shown in FIG. 2 indicates a normal speed change, and since the port 154 is drained, the pulley control oil pressure P ₂ guided to the port 156 is the solenoid valve 171 guided to the right end chamber 153. Is balanced with the sum of the signal hydraulic pressure P ₁ and the spring pressure S _3, and the pulley control hydraulic pressure P ₂ at this time is given by the following equation.

P ₂ × A ₄ = P ₁ × A ₅ + S ₃ (4) In the above formula, A ₄ is the left side land 152a, 152b of the spool 152.
The difference in pressure receiving area of, A ₅ is pressure-receiving area of the right land 152c of the spool 152, S ₃ is a spring load of the spring 151.

Further, FIG. 3 shows a signal hydraulic pressure P ₁ introduced from the solenoid valve 171 to the right end chamber 153, especially during a transitional period when the gear ratio of the continuously variable transmission 30 changes.
Shows the pulley control valve 150 at the moment when the signal pressure P ₁ becomes zero, the internal pressure of the hydraulic chamber 48 of the driven pulley 42 does not immediately decrease, so the pulley guided to the port 156 is shown. The control hydraulic pressure overcomes the spring load and moves the spool 152 to the right end position. At this time, the constant pressure P ₀ regulated by the second pressure regulating valve 110 is output to the input oil chamber 108 of the first pressure regulating valve 100 via the ports 158 and 159, so that the line pressure rapidly increases as shown in the equation (2). It can be prevented from falling.

Further, FIG. 4 shows the pulley control valve 150 when the speed ratio of the continuously variable transmission 30 is maintained at the minimum speed ratio, and the signal hydraulic pressure P ₁ guided to the right end chamber 153 is maximum (equal to P ₀ ). Therefore, the spool 152 is stopped at the left end position, and the line pressure is directly output to the hydraulic chamber 48 via the ports 157 and 155.

Further, when the solenoid valve 171 is operating normally even when retreating, the state shown in FIG. 4 is obtained, but when retreating, not only the port 157 but also the port 154, the output port 124 of the manual valve 120 is output.
Since the line pressure is introduced from the position of the spool 152, even if the solenoid valve 171 malfunctions and the signal oil pressure P ₁ becomes zero (state of FIG. 3) or an intermediate value (state of FIG. 2). Regardless of the line pressure, the line pressure is output from the port 155 to the hydraulic chamber 48 and is always maintained at the lowest speed ratio. Therefore, a reliable fail-safe can be realized.

The clutch control valve 160 has a total of seven ports 161-167, and a spool 168 for switching these ports is arranged in a state of being biased to the left by a spring 169. Directly control solenoid valve 173 to hydraulic pressure P ₅
Is input to the port 163 and the forward / reverse switching valve 130
Line pressure P _L is introduced from port 136 of. Port 164
Is connected to the starting clutch 60, ports 165 and 166 are drain ports, and port 167 is connected to the direct coupling clutch 15. Further, the signal hydraulic pressure P ₃ is guided from the start control solenoid valve 172 to the right end chamber 160a in which the spring 169 is arranged, and the left end chamber 160b facing the right end chamber 160a is provided with a communication hole 168a formed inside the spool 168. And communicates with the port 164 connected to the starting clutch 60.

The upper half of FIG. 2 of the clutch control valve 160 shows the belt drive. When the belt is driven, the direct coupling control solenoid valve 173 is OFF and the start control solenoid valve 172 is ON or the duty control is being performed. Is the start control solenoid valve
The hydraulic pressure P ₄ balanced with the signal hydraulic pressure P _{3 of} 172 and the spring load S ₄ of the spring 169 is output, while the direct coupling clutch 15 is disengaged.

P ₄ × A ₆ = P ₃ × A ₇ + S ₄ (5) In the above formula, A ₆ is the pressure receiving area of the left end portion 168b of the spool 168, and A ₇ is the pressure receiving area of the right side land 168c of the spool 168.

Also, the lower half of the clutch control valve 160 in FIG. 2 shows the direct connection drive, and the start control solenoid valve 172 is OFF and the direct connection control solenoid valve is in the OFF state.
Since 173 is ON, the spool 163 moves to the right end position by the output hydraulic pressure P ₅ (equal to the line pressure P _L ) of the direct coupling control solenoid valve 173 guided to the port 162. As a result, the output hydraulic pressure P ₅ of the direct coupling control solenoid valve 173 is directly output to the direct coupling clutch 173 via the ports 161, 167, and the direct coupling clutch 1
5 coupled, while port 164 connected to the starting clutch 60
And the drain port 165 are in communication, so the starting clutch 60
Is cut off.

The engine speed, vehicle speed, starting clutch input speed, shift position signal, throttle opening, engine water temperature, brake signal, etc. are input to the controller 170. By comparing these signals with prestored data, , The duty control signal is output to the solenoid valves 171-173. As the solenoid valves 171-173, it is possible to use a general needle type solenoid valve.
A 3-port valve having a ball-shaped valve element may be used as described in Japanese Patent Publication No. 60-175884. The duty ratio input to each solenoid valve 171-173 is D ₁ , respectively.
Assuming D ₂ and D ₃ , the output hydraulic pressures P ₁ , P ₃ and P ₅ are as follows.

P ₁ = P ₀ × D ₁ (6) P ₃ = P ₀ × D ₂ (7) P ₅ = P _L × D ₃ (8) By the above output hydraulic pressures P ₁ , P ₃ , and P ₅ , Gear change control, start control, and direct connection control are executed.

Other Embodiments FIG. 5 shows another embodiment of the pulley control valve, in which the spring
A signal hydraulic pressure P ₁ is input from a solenoid valve 171 to a chamber 183 facing the chamber 182 in which the 181 is arranged. The line pressure is constantly guided to the port 184 (first input port), the port 185 is connected to the output port 124 of the manual valve 120, and the port 186 is connected to the hydraulic chamber 48. Further, inside the spool 187, a communication hole 18 for communicating the port 186 with the left end chamber 182 is formed.
7a is formed. In this case, unlike formula (4),
The output oil pressure P ₂ is balanced with the difference between the signal oil pressure P ₁ of the solenoid valve 171 and the spring pressure S ₅ as in the following equation.

P ₂ × B ₁ = P ₁ × B ₂ −S ₅ (9) In the above equation, B ₁ is the pressure receiving area of the left side land 187b of the spool 187, B ₂ is the pressure receiving area of the right side land 187c of the spool 187, S ₅ Is the spring load of the spring 181. Even in this case, since the line pressure is guided to the port 185 when retreating,
The line pressure is output from the output port 186 regardless of the signal oil pressure P ₁ and is always maintained at the lowest speed ratio. Further, when the solenoid valve 171 is turned off during forward traveling, even if there is some residual pressure in the signal hydraulic pressure P ₁ , the output hydraulic pressure P ₂ is completely set to zero () by setting the spring pressure S ₅ appropriately. Drain), and there is also an advantage that shifting to a high speed ratio is easy.

Further, the present invention is not limited to the one in which the torque cam device 35 for applying the belt tension corresponding to the input torque is provided to the drive side pulley 32, and a hydraulic chamber in which a conventionally known line pressure is introduced instead of the torque cam device is provided. It may be provided.

As is apparent from the above description, according to the present invention, in the V-belt type continuously variable transmission in which the driven pulley is provided with the hydraulic chamber for controlling the gear ratio, the line pressure is always guided to the pulley control valve. A first input port, a second input port to which the line pressure is guided only when retreating and a drain at other times, and an output port communicating with the hydraulic chamber in the middle of these input ports are provided, and the spool is connected to the output port. Since the first input port or the second input port is selectively made to communicate with each other, the line pressure is output from the output port regardless of the position of the spool at the time of retreat, and the minimum speed ratio can always be maintained.

[Brief description of drawings]

FIG. 1 is an overall structural view of an example of a V-belt type continuously variable transmission according to the present invention, FIG. 2 is a circuit diagram of a hydraulic control device, FIG.
FIG. 4 is an operation diagram of the pulley control valve at the time of speed change and at the lowest speed ratio, and FIG. 5 is an operation diagram of another embodiment of the pulley control valve. 13 ... Input shaft, 15 ... Direct coupling clutch, 30 ... Continuously variable transmission, 32
Drive pulley, 35 Torque cam device 42 Driven pulley 48 Hydraulic chamber 54 V belt 60 Start clutch 82
... Output shaft, 100 ... First pressure regulating valve, 110 ... Second pressure regulating valve, 120 ...
Manual valve, 124 ... Output port, 130 ... Forward / reverse switching valve,
140 ... Forward / reverse switching piston, 150 ... Pulley control valve, 152 ...
Spool, 154 ... Second input port, 155 ... Output port, 15
7 ... 1st input port, 160 ... Clutch control valve, 170 ... Controller, 171 ... Pulley control solenoid valve, 172 ... Start control solenoid valve, 173 ... Direct connection control solenoid valve.

Claims (1)

[Claims] 1. A V-belt type continuously variable transmission in which a driven-side pulley is provided with a hydraulic chamber for controlling a gear ratio, and a pulley control valve for regulating a line pressure to the hydraulic chamber and outputting it as control hydraulic pressure is provided. The pulley control valve is the first to which the line pressure is constantly guided.
It has an input port, a second input port connected to the output port of a manual valve that outputs hydraulic pressure when retreating and is drained at other times, and an output port connected to the hydraulic chamber. A V-belt which is provided at an intermediate position between the first input port and the second input port, and in which a spool of the pulley control valve selectively connects the output port with the first input port or the second input port. Hydraulic control system for a continuously variable transmission.