JP2781230B2 - Hydraulic control device for continuously variable transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a hydraulic control device in a continuously variable transmission, and more particularly, to a countermeasure for abnormal hydraulic control.

(Prior Art) Conventionally, as a hydraulic control device of a continuously variable transmission, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-4958, a drive pulley and a driven pulley having a variable effective radius, A belt wound between the two pulleys, and a speed ratio control valve and a line pressure adjusting valve are provided. And continuously controlling the speed ratio to variably control the speed ratio, supplying the line pressure to the hydraulic cylinder of the driven pulley by the line pressure adjusting valve, and adjusting the magnitude of the supplied line pressure to adjust the line pressure. 2. Description of the Related Art There is known an apparatus in which the tension of a belt is controlled to suppress or prevent slippage of the rotation of the belt.

(Problems to be Solved by the Invention) By the way, in order to adjust the effective radius of the driving pulley and to control the gear ratio variably, the pressing force of the hydraulic cylinder of the driving pulley is set to a value larger than the pressing force of the hydraulic cylinder of the driven pulley. Must be set to Therefore, in general, by setting the pressure receiving area of the hydraulic cylinder of the drive pulley to be larger than the pressure receiving area of the hydraulic cylinder of the driven pulley, the control hydraulic pressure generated by the speed ratio control valve has a pressure value lower than the line pressure. However, the pressing force of the hydraulic cylinder of the drive pulley is increased by the large pressure receiving area.

However, in this case, if the configuration of the speed ratio control valve is such that the control oil pressure is generated by reducing the line pressure, when the line pressure reaches a maximum pressure value that can be taken according to the engine operating state, or Under the situation where the line pressure was forcibly controlled to the maximum pressure value due to the failure of the adjusting valve and measures were taken to prevent damage due to belt slippage, the gear ratio control valve was further stuck in the fully open state and failed. In the event of an abnormality in the hydraulic control fixed at the end of the stroke, the line pressure of the maximum pressure is supplied to the hydraulic cylinder of the drive pulley without being reduced, and as a result, Due to the large pressure receiving area as described above, an extremely large force acts by the supply of the maximum line pressure. As a result, damage to the hydraulic cylinder of the drive pulley
In order to prevent breakage and ensure the reliability of the equipment, there is a disadvantage in that the rigidity of the hydraulic cylinder needs to be increased more than necessary in advance.

Therefore, for example, it is conceivable to arrange a relief valve that regulates the maximum line pressure on the upstream side of the speed ratio control valve. However, in this idea, the belt tension is secured because the maximum line pressure itself becomes low. However, there is a drawback that the belt may be rotated and slipped, resulting in damage, and inability to operate.

The present invention has been made in view of such a point, and an object of the present invention is to provide a hydraulic control system without unnecessarily increasing the rigidity of a hydraulic cylinder of a drive pulley and without causing damage due to belt slippage. It is an object of the present invention to improve the reliability by enabling safe operation to be continued even in an abnormal situation.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the maximum line pressure is not regulated, but the maximum hydraulic pressure applied to the hydraulic cylinder of the drive pulley is regulated.

That is, a specific solution of the present invention is to provide a driving pulley and a driven pulley configured to change the effective radius by supplying and discharging the hydraulic pressure to and from the hydraulic cylinder, and a belt wound between the pulleys. At the same time, the pressure receiving area of the hydraulic cylinder of the driving pulley is set larger than the pressure receiving area of the hydraulic cylinder of the driven pulley. Further, a gear ratio with an orifice for variably adjusting a gear ratio by controlling a working pressure acting on a hydraulic cylinder of the drive pulley in a working pressure supply passage communicating with a hydraulic cylinder of the drive pulley and supplying a line pressure. A control valve is provided. And, when the operating pressure acting on the hydraulic cylinder of the drive pulley is at the maximum line pressure at the minimum gear ratio, the minimum gear ratio is set on the hydraulic cylinder side of the drive pulley of the gear ratio control valve in the operating pressure supply passage. When the pressure value exceeds the pressure value that can be formed, a relief valve that relieves oil acting on the hydraulic cylinder of the drive pulley is arranged.

(Operation) With the above configuration, according to the present invention, when the gear ratio is changed to the minimum side, the gear ratio control valve with the orifice reduces the line pressure by the throttle function inside the valve, compared to the orifice provided therein. . Then, the degree of reduction of the line pressure by the speed ratio control valve is reduced, and the operating pressure supplied to the hydraulic cylinder of the drive pulley is increased, and this operating pressure is increased by the oil chamber having a large pressure receiving area of the hydraulic cylinder of the drive pulley. Therefore, the pressing force of the hydraulic cylinder of the driving pulley becomes stronger than the pressing force of the hydraulic cylinder of the driven pulley. As a result, the effective radius of the driving pulley increases and the effective radius of the driven pulley decreases, so that the speed ratio is controlled to the minimum side.

Now, when the line pressure reaches the maximum value, for example, in the event of an abnormality in hydraulic control in which the gear ratio control valve fails in a fully opened state, the line pressure is not reduced by this gear ratio control valve, so that the oil of the maximum line pressure is driven. Introduced into the hydraulic cylinder of the pulley. In this case, conventionally, there is no oil flow in a situation where the effective radius of the drive pulley is fixed to the maximum, so that the pressure before and after the orifice of the transmission ratio control valve is equal, and the hydraulic pressure is applied to the hydraulic cylinder of the drive pulley. Is a situation in which the maximum line pressure acts and an extremely large force always acts on the hydraulic cylinder.In the present invention, oil of the maximum line pressure is relieved by a relief valve, and the maximum pressure is reduced by the relief valve. Since the operation pressure is regulated by the set relief pressure, an abnormal increase in the operating pressure is prevented, so that the rigidity of the hydraulic cylinder of the driving pulley is unnecessarily increased.

In addition, the set relief pressure of the relief valve is a pressure value at which the operating pressure of the hydraulic cylinder of the driving pulley is maximum when the hydraulic control is normal, that is, the effective radius of the driving pulley at the maximum line pressure at which a large belt tension is required. Since the pressure value is set to a value exceeding the pressure value that can form the minimum speed ratio at the minimum speed ratio at which the minimum speed ratio should be maximized, the formation of the minimum speed ratio during normal hydraulic control is not hindered.

Further, since the relief valve is located on the hydraulic cylinder side of the drive pulley of the speed ratio control valve, even if the oil is relieved, the orifice of the speed ratio control valve restricts the upstream side of the speed ratio control valve. The line pressure of the belt maintains its value. As a result, the adjustment control of the tension of the belt using this line pressure is performed well, and the belt does not slip and does not damage.

(Effect of the Invention) As described above, according to the hydraulic control device for a continuously variable transmission of the present invention, in a situation where an unnecessarily high operating pressure acts on the hydraulic cylinder of the drive pulley, the line pressure is increased. While securing, the oil acting on the hydraulic cylinder of the drive pulley was relieved and the maximum pressure was regulated, so the rigidity of the hydraulic cylinder of the drive pulley was not increased unnecessarily, and the gear ratio control valve was fully opened. Even in the event of a failure or an abnormality of the hydraulic control fixed at the stroke end, a favorable power transmission state without slippage in the rotation of the belt can be ensured, and reliability can be improved.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First
The figure shows the entire structure of the continuously variable transmission. The continuously variable transmission shown in FIG. 1 includes a torque converter 2 connected to an output shaft 11 of an engine 1, a forward / reverse switching mechanism 3, a continuously variable transmission mechanism 4, a speed reduction mechanism 5, and a differential mechanism 6. It is configured.

The torque converter 2 includes a pump cover 21 coupled to the engine output shaft 11, a pump impeller 22 fixed to one side of the pump cover 21 and rotating integrally with the engine output shaft 11, and a pump impeller 22. A turbine runner 23 rotatably provided inside the pump cover 21 so as to face the turbine runner 23, and the turbine runner 23 and the pump impeller.
And a stator 24 interposed between the stator 24 and the
And a turbine shaft 25 fixed to the turbine runner 23. The stator 24 is connected to the transmission case 7 via a one-way clutch 26 and a stator shaft 27. A lock-up piston 28 slidably mounted on the turbine shaft 25 is provided between the turbine runner 23 and the pump cover 21, and a lock-up fastening chamber 29a formed on both sides of the lock-up piston 28 is locked up. By introducing and discharging the hydraulic pressure to and from the open chamber 29b, the lock-up piston 28 and the pump cover 21 are fastened and released.

The forward / reverse switching mechanism 3 includes a carrier 31, pinion gears 32, 32 supported by the carrier 31, a sun gear 34 spline-coupled to a primary shaft 411 of a continuously variable transmission mechanism 4, which will be described later, and meshes with the pinion gear 32, and a pinion gear And a ring gear 35 meshing with the ring gear 32.
Are spline-coupled to the turbine shaft 25 of the torque converter 2. A forward clutch 36 is provided between the ring gear 35 and the carrier 31 for intermittent connection between the ring gear 35 and the carrier 31. The carrier 31 is selectively fixed to the transmission case 7 between the carrier 31 and the transmission case 7. A reverse brake 37 is provided. With this configuration, when the forward clutch 36 is engaged and the reverse brake 37 is released, the ring gear 35 and the carrier 31 are integrally connected to rotate, and the rotation of the turbine shaft 25 is directly While transmitting to the shaft 411, when the reverse brake 37 is engaged and the forward clutch 36 is released, the carrier 31
Is fixed to the case 7 so that it cannot rotate, the rotation of the ring gear 35 is transmitted to the sun gear 34 via the pinion gears 32, and the rotation of the turbine shaft 25 is reversed to be transmitted to the primary shaft 411 of the continuously variable transmission mechanism 4. Has been made. When both the forward clutch 36 and the reverse brake 37 are released, the primary shaft 41 of the continuously variable
The driving force of the engine is not transmitted to 1 (neutral and parking states).

The continuously variable transmission mechanism 4 includes a primary pulley 41 as a driving pulley, a secondary pulley 42 as a driven pulley, and a V-belt 43 wound between the pulleys 41 and 42.

The primary pulley 41 includes a primary shaft 411 arranged coaxially with the turbine shaft 25, a fixed cone plate 412 fixed to the primary shaft 411, and a primary shaft 411 arranged facing the fixed cone plate 412. And a movable conical plate 413 slidably supported. When the movable conical plate 413 moves, the holding position of the V-belt 43 changes, and the effective pitch diameter (effective radius) changes. That is, when the movable conical plate 413 approaches the fixed conical plate 412, the effective pitch diameter becomes large,
When 3 is separated from the fixed conical plate 412, the effective pitch diameter becomes smaller.

Further, the secondary pulley 42 has basically the same configuration as the primary pulley 41 described above. That is, it has a secondary shaft 421 arranged in parallel with the primary shaft 411, a fixed conical plate 422 fixed to the secondary shaft 421, and a movable conical plate 423 slidably supported.
The effective pitch diameter changes with the movement of 23.

Hydraulic cylinders 414 and 424 for sliding the respective movable conical plates 413 and 423 are provided at the backs of the respective movable conical plates 413 and 423 in the respective pulleys 41 and 42. Hydraulic pressure is introduced and discharged to the hydraulic cylinder 414 of the primary pulley 41 to change the gear ratio between the two pulleys 41 and 42, and the tension of the V-belt 43 is always appropriately maintained in the hydraulic cylinder 424 of the secondary pulley 42 Hydraulic pressure is introduced and discharged in order to achieve this. Then, when hydraulic pressure is introduced into the hydraulic cylinder 414 of the primary pulley 41, the clamping position of the V-belt 43 in the primary pulley 41 moves outward, and the effective pitch diameter of the primary pulley 41 increases. The holding position of the V-belt 43 on the secondary pulley 42 moves inward, and the secondary pulley 42
Effective pitch diameter becomes smaller, and the gear ratio between the primary shaft 411 and the secondary shaft 421 becomes smaller (in the speed increasing direction).
Change. Conversely, when the hydraulic pressure is discharged from the hydraulic cylinder 414, the effective pitch diameter of the primary pulley 41 decreases, and the effective pitch diameter of the secondary pulley 42 increases.
The transmission gear ratio changes greatly (in the deceleration direction).

The configuration of the hydraulic cylinder 414 of the primary pulley 41 will be specifically described. The hydraulic cylinder 414 includes a first oil chamber 14a formed on the back of the movable conical plate 413, and a movable conical plate 413.
A movable piston 14c for pressing a rear end of a member 14b connected to an outer end of the movable piston 14c;
An oil chamber 14d is provided, and hydraulic pressure is supplied to the first oil chamber 14a and the second oil chamber 14d to move the movable conical plate 413 rightward in FIG.

On the other hand, similarly to the above, the configuration of the hydraulic cylinder 424 of the secondary pulley 42 includes a first oil chamber 15a formed on the back of the movable conical plate 423 and a member 15 connected to the outer end of the movable conical plate 423.
b, a movable piston 15c for pressing the rear end, a second oil chamber 15d formed on the back of the movable piston 15c, and a spring 15e compressed in the second oil chamber 15d to bias the movable piston 15c.
In this configuration, hydraulic pressure is supplied to the first oil chamber 15a and the second oil chamber 15d to move the movable conical plate 423 to the left in FIG.

The total pressure receiving area of the first hydraulic chamber 14a and the second hydraulic chamber 14d of the hydraulic cylinder 414 of the primary pulley 41 is equal to the first hydraulic chamber 15a and the second hydraulic chamber of the hydraulic cylinder 424 of the secondary pulley 42.
The area is set to more than twice the total pressure receiving area of 15d.

The speed reduction mechanism 5 and the differential mechanism 6 have a known structure, and transmit the rotation of the secondary shaft 421 to the axle 61.

Next, the lock-up piston 28 of the torque converter 2 in the above-described continuously variable transmission, the forward clutch 36 and the reverse brake 37 of the forward / reverse switching mechanism 3, the primary pulley 41 and the secondary pulley 42 of the continuously variable transmission 4 A hydraulic circuit for controlling each operation of the above will be described with reference to FIG.

The hydraulic circuit shown in FIG. 1 has an oil pump 81 driven by the engine 1. The hydraulic oil discharged from the oil pump 81 is first adjusted to a predetermined line pressure by a line pressure adjusting valve 82, and then supplied to a hydraulic cylinder 424 of the secondary pulley 42 via a line 101, Finally, it is supplied to a hydraulic cylinder 414 of the primary pulley 41 via a line 102 branched from the main pulley 41.

The line pressure adjusting valve 82 has a spool 820 composed of a main spool 821 and a sub spool 822 arranged in series. The main spool 821 and the sub spool 822 constituting the spool 820 are provided at one end of the main spool 821 with the sub spool 82.
It is connected so that one end of 2 is in contact. The other end of the sub spool 822 has a large-diameter portion having a cross-sectional area larger than the contact area with the main spool 821 (cross-sectional area of the connection portion).
822a is provided. At a position corresponding to the center of the main spool 821, a pressure adjusting port 823 through which the discharge oil from the oil pump 81 is guided, and a drain port 824 communicating with the suction side of the oil pump 81 are provided. In the figure, the left side shuts off the connection between the pressure adjustment port 823 and the drain port 824, and the main spool 821 shifts to the right side in the figure, shuts off the connection between the pressure adjustment port 823 and the drain port 824. When the 821 is shifted to the right side in the figure, communication between the pressure adjustment port 823 and the drain port 824 is established. A first pilot chamber 825 is formed at a position corresponding to a connection portion between the main spool 821 and the sub spool 822, and a spring 826 for urging the main spool 821 to the left in the drawing is interposed in the first pilot chamber 825. Have been. A second pilot chamber 827 communicating with the first pilot chamber 825 is formed in the large diameter portion 822a of the sub spool 822. The first pilot chamber 825 and the second pilot chamber 827 have a reducing valve 83 while branching from the line 102 and passing through the line 103.
Accordingly, the hydraulic oil reduced to a predetermined pressure is introduced as the pilot pressure adjusted by the first duty solenoid valve 91 while passing through the pilot passage 103a. And this pilot pressure is
While acting in the same direction as the urging force, the hydraulic pressure in the line 101 acts on the other end of the main spool 821 so as to oppose the urging force and the pilot pressure. Pressure adjustment port 823 and drain port 824
The line pressure is reduced to the first by communicating and blocking
The duty solenoid valve 91 is controlled to a value corresponding to a pilot pressure adjusted by the duty solenoid valve 91.

The line pressure adjusted as described above is controlled to change in accordance with the engine operating state, and the primary pulley 41
When the input torque is large, the line pressure is controlled to be high so as to prevent slippage of the rotation of the belt 43 in that case,
The maximum line pressure is, for example, 30 kg / cm ² .

The line 102, that is, the line as the working pressure supply passage through which the line pressure is supplied by communicating with the oil chambers 14a and 14d of the hydraulic cylinder 414 of the primary pulley 41, has an orifice 85a.
A gear ratio control valve 85 is provided. The speed ratio control valve 85 includes a spool 851, a spring 852 for urging the spool 851 rightward in the figure, a line pressure port 853 connected to an upstream portion of the line 102, a drain port 854, and a spring 852. Shift valve opened on installation side via line 104
It has a reverse port 855 connected to 87 and a pilot chamber 856 formed on the opposite side of the spring 852 installation side to introduce pilot pressure. The pilot chamber 856 is connected via a pitot valve 86 to a second duty solenoid valve 92 and a pitot pressure generating means 90 for generating a pitot pressure having a pressure corresponding to the rotation speed of the engine 1. Therefore,
The pitot pressure generated by the pitot pressure generating means 90 and the pressure adjusted by the second duty solenoid valve 92 can be selectively introduced as pilot pressure into the pilot chamber 856 by the pitot valve 86. Even when the solenoid valve 92 fails, the pitot pressure can be introduced from the pitot pressure generating means 90 to the pilot chamber 856 as the pilot pressure.

The gear ratio control valve 85 is operated at the time of forward movement (shift valve
87 is in the D, 2, 1 shift position), the hydraulic pressure is drained from the reverse port 855 via the shift valve 87, and the pilot pressure introduced into the pilot chamber 856 and the spring pressure The spool 851 moves due to the force relationship with the biasing force, and the line pressure port 853 and the drain port 85
4 is selectively communicated with the hydraulic cylinder 414 of the primary pulley 41. In this way, by controlling the supply and discharge of the hydraulic pressure to and from the hydraulic cylinder 414 of the primary pulley 41 according to the pilot pressure introduced into the pilot chamber 856 during forward movement, the hydraulic cylinder 414 of the primary pulley 41 is actuated. By controlling the operating pressure, the speed ratio between the primary pulley 41 and the secondary pulley 42 of the continuously variable transmission mechanism 4 is variably adjusted.

On the other hand, when the vehicle is moving backward (when the shift valve 87 is in the R shift position), hydraulic pressure (operating pressure described later) is introduced from the reverse port 855, and the operating pressure pushes the spool 851 to the right side in the drawing. Fixed in state. Therefore, at the time of reverse, the hydraulic cylinder 41 of the primary pulley 41
4 and the drain port 854 are always in communication, and the gear ratio is fixedly held at the maximum gear ratio.

It should be noted that even during neutral and parking when the driving force of the engine 1 is not transmitted to the axle 61 by the forward / reverse switching mechanism 3 (when the shift valve 87 is in each of the N and P shift positions),
It will be in the same state as when traveling backward.

The hydraulic cylinder 414 of the primary pulley 41
The line 102 communicating with the downstream side of the speed ratio control valve 85,
That is, the relief valve 100 is arranged on the hydraulic cylinder 414 side of the primary pulley 41. When the operating pressure acting on the oil chambers 14a, 14d of the hydraulic cylinder 414 of the primary pulley 41 is equal to or higher than the set relief pressure, the relief valve 100
The oil in the downstream of the gear ratio control valve 85 is relieved.
And the set relief pressure is that the line pressure is the maximum pressure (30
kg / cm ² ), the pressure value is set to a value slightly higher than the pressure value necessary and sufficient to form the minimum gear ratio for maximizing the effective pitch diameter of the primary pulley 41, that is, 15 kg / cm ² . I have.

The hydraulic oil regulated by the line pressure regulating valve 82 is:
In addition to the line 101, it is also transmitted to a line 105. Line 105
Is supplied to the line 106 and the line 107 after being adjusted to a predetermined operating pressure by the operating pressure adjusting valve 88.

The operating pressure adjusting valve 88 includes a spool 881, a pilot chamber 882 formed at one end of the spool 881, a spring 883 interposed in the pilot chamber 882, and a first pressure adjusting port 884 connected to the line 105. , A second pressure adjustment port 885 connected to the line 107, and a drain port 886. The pilot chamber 882 is connected to the first duty solenoid valve 91 via the pilot passage 103a.
For this reason, the working oil regulated by the first duty solenoid valve 91 is introduced into the pilot chamber 882 as pilot pressure. Then, while this pilot pressure acts in the same direction as the urging force of the spring 883, the hydraulic pressure in the line 105 acts on the other end of the spool 881 so as to oppose the urging force and the pilot pressure. The spool 881 moves depending on the relationship, and the communication between the first and second pressure adjusting ports 884, 885 and the drain port 886 is interrupted, so that the operating pressure of the forward clutch 36 and the reverse brake 37 reduces the first duty solenoid valve. 91
The pressure is controlled to a value corresponding to the pilot pressure adjusted.

The hydraulic oil supplied to the line 106 is supplied to the shift valve 87.
When the shift valve 87 is at the shift position of D, 2, 1 and is supplied to the hydraulic chamber 36a of the forward clutch 36 of the forward / reverse switching mechanism 3 via the line 109, and when the shift valve 87 is at the shift position of R, it is supplied via the line 108. In addition, it is supplied to the hydraulic chamber 37a of the reversing brake 37 of the forward / reverse switching mechanism 3 and to the reverse port 855 of the speed ratio control valve 85 via the line 104. On the other hand, the forward clutch 36 of the forward / reverse switching mechanism 3
When the shift valve 87 is at the R, N, P shift position, the hydraulic oil in the hydraulic chambers 36a, 37a of the reverse brake 37
It is designed to be discharged through 09,108. Therefore,
The forward clutch 36 and the reverse brake 37 of the forward / reverse switching mechanism 3 are engaged and released in accordance with the shift position of the shift valve 87, and as described above, are continuously variable at the R, N, P shift positions. The speed ratio of the speed change mechanism 4 is fixedly held at the maximum speed ratio.

The hydraulic oil supplied to the line 107 is supplied to the lock-up fastening chamber 29a or the lock-up release chamber 29b of the torque converter 2 through the lock-up control valve 89.
It is supplied to. The lock-up control valve 89 is configured such that the operation of the spool 891 is controlled by the pilot pressure adjusted by the third duty solenoid valve 93. Then, when the pilot pressure decreases, the spool 891 moves to the right in the drawing, the hydraulic oil is supplied from the line 107 to the lock-up fastening chamber 29a, and the hydraulic oil in the lock-up release chamber 29b is discharged. When the pilot pressure increases, the spool 891 moves to the left in the drawing, and the line 107
, The hydraulic oil is supplied to the lock-up release chamber 29b, and the hydraulic oil in the lock-up fastening chamber 29a is drained.

94 indicates that the first duty solenoid valve 91 is ON.
An accumulator valve for preventing the pilot pressure of the pilot passage 103a from pulsating when turned off, 95 and 96 are accumulators for alleviating shock when the forward clutch 36 and the reverse brake 37 are engaged, and 97 is a relief valve. is there. Reference numeral 98 denotes a pressure-holding valve that keeps a predetermined low constant pressure when draining the pressure oil in the hydraulic cylinder 414 of the primary pulley 41.

FIG. 3 shows an electric control circuit of the above-described continuously variable transmission. In this figure, a control unit 110 incorporating a microcomputer and the like includes a shift position signal from a shift position sensor 111 for detecting a shift position (D, 1, 2, R, N, P) operated by a driver; A primary pulley rotation speed signal from a primary rotation speed sensor 112 for detecting the rotation speed np of the primary shaft 411; a secondary pulley rotation speed signal from a secondary rotation speed sensor 113 for detecting the rotation speed ns of the secondary shaft 421; , A throttle valve opening signal from a throttle opening sensor 114 for detecting the throttle valve opening TVO, an engine speed signal from an engine speed sensor 115 for detecting the engine speed Ne, and a turbine of the torque converter 2. A turbine speed signal from a turbine speed sensor 116 that detects the speed Nt of the shaft 25 is input.

The control unit 110 controls the duty of the first to third duty solenoid valves 91, 92, 93 based on these input signals, whereby the line pressure adjusting valve 82, the operating pressure adjusting valve 88, the speed ratio control valve Each pilot pressure introduced to the lock valve 85 and the lock-up control valve 89 is adjusted.

Therefore, in the above embodiment, when the engine 1 is operating, the duty control of the first duty solenoid valve 91 is performed according to the operating state, whereby the pilot pressure introduced into the line pressure adjusting valve 82 is adjusted,
The line pressure may reach the maximum value of 30 kg / cm ² so that the belt 43 of the continuously variable transmission mechanism 4 obtains an appropriate tension without slippage of rotation. Further, the line pressure may be forcibly controlled to the maximum value of 30 kg / cm ² due to the failure of the line pressure adjusting valve 82.

In this case, when the speed ratio control valve 85 is operating normally, the duty control of the second duty solenoid valve 92 is performed so that the target speed ratio is achieved, and the pilot pressure generated by this control is applied to the speed ratio control valve 85. As a result, the above-mentioned maximum line pressure is reduced by the speed ratio control valve 85 by the throttle action of the valve itself, and becomes a predetermined operating pressure, so that the first oil chamber 14a of the hydraulic cylinder 414 of the primary pulley 41 becomes And the second oil chamber 14d, where a pressing force of a value obtained by multiplying the operating pressure by the total pressure receiving area of both oil chambers acts on the movable conical plate 413. On the other hand, the maximum line pressure adjusted by the line pressure adjustment valve 82 remains at that value, and the first and second oil chambers 15a, 15d of the hydraulic cylinder 424 of the secondary pulley 42 remain at that value.
Here, a pressing force of a value obtained by multiplying the maximum line pressure by the total pressure receiving area of the two oil chambers acts on the movable conical plate 423. Here, the pressing force on the primary pulley 41 is 30 kg / cm ² because the total pressure receiving area of the hydraulic cylinder 414 is set to be more than twice the total pressure receiving area of the hydraulic cylinder 424 of the secondary pulley 42. Even when the maximum line pressure is reduced to a half value of 15 kg / cm ² by the transmission ratio control valve 85 to form the minimum transmission ratio, the pressing force on the primary pulley 41 has a larger force. As a result, the effective pitch diameter of the primary pulley 41 increases, and the effective pitch diameter of the secondary pulley 42 decreases, and a minimum speed ratio can be obtained. In this case, since the set relief pressure of the relief valve 100 is a value slightly exceeding 15 kg / cm ² , it is not operating.

On the other hand, when the gear ratio control valve 85 is stuck in the fully opened state or when the hydraulic control fixed at the stroke end is abnormal, the maximum line pressure is reduced by the hydraulic cylinder of the primary pulley 41.
Although the oil pressure chamber 414 is about to be introduced into the oil chambers 14a and 14d, the relief valve 100 is operated to release the oil downstream of the speed ratio control valve 85 in the line 102 to the tank. Relief pressure. Therefore, it is possible to prevent the rigidity of the hydraulic cylinder 414 of the primary pulley 41 from being increased more than necessary.

In addition, when the above hydraulic control is abnormal, the relief valve 10
Since oil is relieved on the downstream side of the speed ratio control valve 85 by 0, on the upstream side of the speed ratio control valve 85 of the line 102, the line pressure is reduced by the throttle action of the orifice 85a of the speed ratio control valve 85. Since the belt is held at the maximum value of 30 kg / cm ² , the belt 43 of the continuously variable transmission mechanism 4 transmits power with an appropriate tension without slipping, so that the reliability in the event of an abnormality in the hydraulic control is ensured well. be able to.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a specific configuration diagram of a continuously variable transmission, FIG. 2 is a hydraulic control circuit diagram, and FIG. 3 is a block diagram showing an electric control system. 41: Primary pulley (drive pulley), 41: Hydraulic cylinder, 42: Secondary pulley (driven pulley), 43:
... belt, 85 ... gear ratio control valve, 85a ... orifice, 1
00 ... relief valve, 102 ... line (operating pressure supply passage)

Claims (1)

(57) [Claims] A drive pulley and a driven pulley configured to change an effective radius by supply and discharge of a hydraulic pressure to and from a hydraulic cylinder, and a belt wound between the two pulleys; Is set larger than the pressure receiving area of the hydraulic cylinder of the driven pulley, and acts on the hydraulic cylinder of the driving pulley in the working pressure supply passage communicating with the hydraulic cylinder of the driving pulley and supplying the line pressure. In a hydraulic control device for a continuously variable transmission provided with a speed ratio control valve with an orifice for controlling a working pressure to variably adjust a speed ratio, a hydraulic cylinder side of a drive pulley of the speed ratio control valve of the working pressure supply passage is provided. The operating pressure acting on the hydraulic cylinder of the drive pulley exceeds the pressure value at which the minimum speed ratio can be formed at the maximum line pressure at the minimum speed ratio. Can, CVT hydraulic pressure control device, characterized in that the relief valve to relieve the oil acting on the hydraulic cylinder of the drive pulley is disposed.