JPH0814345A - Hydraulic control device for continuously variable transmission - Google Patents

Abstract

PURPOSE:To make line pressure lower than the drain pressure of a line pressure regulating valve under normal conditions so as to improve fuel consumption by switching the set pressure of a clutch relief valve. CONSTITUTION:Line pressure is constantly supplied to the pilot port 102b of the line pressure regulating valve 102 of a hydraulic control device for a continuously variable transmission having a hydraulic power transmission 12 equipped with a lockup mechanism, and the line pressure is selectively supplied to the pilot port 102c of the line pressure regulating valve 102 only when the drain pressure of a line pressure/clutch pressure switching valve 120 is high. Since the drain pressure of the line pressure/clutch pressure switching valve 120 is supplied also to the pilot port 122e of a clutch relieve valve 122, the set pressure of the clutch relief valve 122 is switched in two steps, and the line pressure in the region of a low line pressure characteristic where the pulley ratio is high under normal conditions is reduced for enhanced fuel consumption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuously variable transmission having a clutch relief valve whose drain pressure of a line pressure regulating valve is used as a source pressure so that the line pressure regulating range can be expanded to obtain a desired line pressure. The present invention relates to a hydraulic control device capable of adjusting pressure.

[0002]

As a conventional example of a continuously variable transmission, for example,
There is one described in Japanese Patent Application Laid-Open No. 61-105353 previously proposed by the applicant of the present application. This conventional example is configured as a belt type continuously variable transmission that controls the input / output gear ratio by changing the contact point radius between the belt and the pulley and changing the pulley ratio. Is controlled to variably control the width of the pulley groove formed between the movable pulley piece (movable conical member) and the fixed pulley piece (fixed conical member) to feedback control the gear ratio.

The movable pulley piece (movable conical member) is made into a piston, and a predetermined hydraulic pressure is applied to its cylinder chamber, and the hydraulic pressure intervenes between the pulley pieces (both conical members) for rotational movement. The belt that holds
Even if the transmitted rotational driving force (torque) fluctuates, the width of the pulley groove does not change. Further, in the cylinder chamber of the movable pulley piece (movable conical member) of the drive pulley and the driven pulley, for example, at the reference line pressure,
The hydraulic pressure added with the throttle pressure according to the throttle opening,
It is supplied as line pressure after being adjusted by the line pressure adjusting valve, and the clamping force that does not cause the belt to slip is applied to both driven pulleys of both pulley pieces of the driven pulley according to the rotational driving force transmitted from the driving side to the driven side. It is supposed to occur in the meantime.

The spool of the line pressure regulating valve is connected to a rod moved by the rotation angle control of a step motor via a lever, and the lever is connected to a movable pulley piece (movable conical member) of a drive pulley. Are also connected. When the rod moves in accordance with the rotation of the step motor, the lever rotates in the direction opposite to the moving direction of the rod to move the movable pulley piece (movable conical member) of the drive pulley, which causes the line pressure regulating valve. The spool is moved, and the line pressure is adjusted in accordance with the rotational driving force applied to the belt so as to apply a gripping force so that the belt does not slip. At that time, the line pressure adjusted as described above is also supplied to the drive pulley via the shift control valve, and the spool of the shift control valve is connected to the lever, so that the rotation of the step motor is changed as described above. Accordingly, the lever moves while rotating relative to the movable pulley piece (movable conical member) of the drive pulley, thereby moving the spool of the shift control valve.

By the way, in a continuously variable transmission having a clutch relief valve using the drain pressure of the line pressure regulating valve as a source pressure, the characteristic of the line pressure regulated by the line pressure regulating valve (line pressure-pulley ratio characteristic). Is a high pressure line pressure characteristic and a low pressure line pressure characteristic, as shown in FIG.
Switching to stages is required. Such a line pressure characteristic is obtained by, for example, guiding the gear ratio specific pressure and the line pressure to the spool of the line pressure regulating valve from the same direction, and hydraulic pressure (in this case, the drain pressure of the line pressure ON / OFF solenoid valve; The built-in drain port is closed when the switch is off and the drain pressure is high. When the switch is on, the built-in drain port is open and the drain pressure is almost 0). ON / O
When the FF solenoid valve is OFF, the high pressure line pressure characteristic is obtained, and at the time of stall, the line pressure ON / OFF solenoid valve is turned ON so that the low pressure line pressure characteristic is obtained.

[0006]

In the continuously variable transmission of the above-mentioned conventional example, the set pressure (clutch pressure) of the clutch relief valve, which is based on the drain pressure of the line pressure regulating valve, is used for so-called racing select operation. In order to prevent clutch slippage and belt slippage in the accompanying stall state, it is necessary to set the pressure to a predetermined value (clutch pressure; 10 kgf / cm ² in FIG. 6) or more. In this case, even if an attempt is made to obtain the reduced low-pressure line pressure characteristic, the clutch relief valve uses the drain pressure of the line pressure regulator, which is lower than the line pressure, as the original pressure. In the above, the pressure cannot be reduced below the predetermined value, the fuel consumption is deteriorated, and the pressure adjustment range of the line pressure is narrowed.

An object of the present invention is to solve the above-mentioned problems by using the drain pressure from the line pressure switching valve for the pressure regulation of the clutch relief valve, which uses the drain pressure of the line pressure regulator as the source pressure. .

[0008]

To this end, the structure of claim 1 of the present invention is a hydraulic control device for a continuously variable transmission having a clutch relief valve whose source pressure is the drain pressure of a line pressure regulating valve. A valve means for switching the set pressure of the clutch relief valve is provided.

In the above, one O is used as the valve means.
An N / OFF solenoid valve is used, and the line pressure regulating valve is regulated by the ON / OFF solenoid valve, and the clutch relief valve is regulated by adjusting the number of ON / OFF solenoid valves. It is preferable to reduce the cost to reduce the cost.

In the above, ON / OFF of the solenoid valve
The OFF switching is preferably controlled in accordance with the magnitude of the clutch input torque in order to realize the low-pressure line pressure characteristic that is reduced in the stall state by applying the pressure adjusting action of the clutch relief valve.

In the above description, the magnitude of the clutch input torque is determined based on whether or not the lockup state is established. It is possible to realize the reduced low-pressure line pressure characteristic in the non-lockup state in the normal state and the pulley ratio. It is preferable to improve fuel efficiency in the HIGH side region.

In the above, the line pressure regulating valve is adapted to regulate the pressure by the signal relating to the engine torque and the signal relating to the gear ratio, which is usually the case when the reduced low pressure line pressure characteristic is not locked up. It is sometimes realized to improve fuel efficiency in the HIGH side region of the pulley ratio.

[0013]

According to the first aspect of the present invention, the line pressure is regulated in the continuously variable transmission having the clutch relief valve whose source pressure is the drain pressure of the line pressure regulating valve which is lower than the line pressure. In this case, since the valve means for switching the set pressure of the clutch relief valve is provided, when the valve means is normally turned OFF to have the high-pressure line pressure characteristic shown in FIG. 6, the valve means is turned OFF during stall. ON
By switching to, the low-pressure line pressure characteristic of FIG. 5 can be obtained. In this low pressure line pressure characteristic, the lower limit value is lower than a predetermined value (clutch pressure; for example, 10 kgf / cm ² in the above conventional example) determined by the line pressure lower limit value of the above high pressure line pressure characteristic ( For example, 6kgf / cm ² )
The drain pressure of the line pressure regulating valve that has become this low value becomes the source pressure of the clutch relief valve. Therefore, the fuel consumption is improved as desired and the pressure adjustment range of the line pressure is expanded.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a skeleton diagram showing a power transmission mechanism used in a hydraulic control device for a continuously variable transmission according to a first embodiment of the present invention. In the figure, 10 is an engine, and its output shaft 10a
A torque converter 12, which is a fluid transmission device, is connected to. The torque converter 12 has a lockup mechanism, and can mechanically connect or disconnect the pump impeller 12b on the input side and the turbine liner 12c on the output side by controlling the hydraulic pressure in the lockup oil chamber 12a. it can. The output side of the torque converter 12 is connected to the rotary shaft 13. The rotating shaft 13 is connected to the forward / reverse switching mechanism 15. The forward / reverse switching mechanism 15 is
It has a planetary gear mechanism 17, a forward clutch 40, and a reverse brake 50.

The planetary gear mechanism 17 includes a sun gear 19 and a sun gear 19.
The pinion carrier 25 includes two pinion gears 21 and 23, and an internal gear 27. The two pinion gears 21 and 23 mesh with each other, the pinion gear 21 meshes with the sun gear 19, and the pinion gear 23 meshes with the internal gear 27. The sun gear 19 is connected so as to always rotate integrally with the rotary shaft 13. The pinion carrier 25 can be connected to the rotating shaft 13 by a forward clutch 40. Further, the internal gear 27 can be fixed to the stationary portion by the reverse brake 50. The pinion carrier 25 is connected to the drive shaft 14 arranged on the outer periphery of the rotary shaft 13, and the drive shaft 14 is provided with a drive pulley 16.

The drive pulley 16 has a fixed conical plate 18 which rotates integrally with the drive shaft 14 and a hydraulic cone which is arranged facing the fixed conical plate 18 to form a V-shaped pulley groove and which acts on the drive pulley cylinder chamber 20. And a movable conical plate 22 that is movable in the axial direction of the drive shaft 14.
The drive pulley cylinder chamber 20 includes the chambers 20a and 2a.
Driven pulley cylinder chamber 3 which will be described later.
It has twice the pressure receiving area as 2. Drive pulley 16 is V
A belt 24 is drivingly connected to a driven pulley 26.

The driven pulley 26 is provided on the driven shaft 28 and rotates fixedly with the driven shaft 28, and a fixed conical plate 30 is disposed so as to face the fixed conical plate 30 to form a V-shaped pulley groove. A movable conical plate 34 movable in the axial direction of the driven shaft 28 by the hydraulic pressure acting on the cylinder chamber 32.
It consists of and. The drive pulley 16, the V belt 24 and the driven pulley 26 constitute a V belt type continuously variable transmission mechanism 29. A drive gear 46 is attached to the driven shaft 28.
Are fixed, and the drive gear 46 meshes with the idler gear 48 on the idler shaft 52. The pinion gear 54 provided on the idler shaft 52 always meshes with the final gear 44. The final gear 44 includes a differential device 56.
A pair of pinion gears 58 and 60 constituting the above are attached, and a pair of side gears 62 and 64 mesh with the pinion gears 58 and 60.
2 and 64 are connected to output shafts 66 and 68, respectively.

In the power transmission mechanism as described above, the engine 10
The rotational force input from the output shaft 10a of the motor is transmitted through the torque converter 12 and the rotary shaft 13 to the forward / reverse switching mechanism 15
Is transmitted to Here, when the forward clutch 40 is engaged (when the reverse brake 50 is released), the rotational force of the rotary shaft 13 remains in the same rotational direction via the planetary gear mechanism 17 that is in the integrally rotating state. 14 is transmitted to
When the forward clutch 40 is disengaged (the reverse brake 50 is engaged), the planetary gear mechanism 17 acts to rotate the rotary shaft 13
Is transmitted to the drive shaft 14 in a state where the rotation direction is reversed. The rotational force of the drive shaft 14 is the drive pulley 16, V
Belt 24, driven pulley 26, driven shaft 28, drive gear 4
6, the idler gear 48, the idler shaft 52, the pinion gear 54, and the final gear 44 are transmitted to the differential device 56, which causes the output shafts 66 and 68 to rotate in the forward or reverse direction. The forward clutch 40
When both the reverse brake 50 and the reverse brake 50 are released, the power transmission mechanism is in the neutral state.

During the power transmission as described above, the movable conical plate 22 of the drive pulley 16 and the movable conical plate 34 of the driven pulley 26 are moved in the axial direction to change the contact position radius with the V belt 24. The rotation ratio between the drive pulley 16 and the driven pulley 26 can be changed. For example, while increasing the width of the V-shaped pulley groove of the drive pulley 16,
When the width of the V-shaped pulley groove of the driven pulley 26 is reduced,
The contact position radius of the V belt on the drive pulley 16 side becomes small, and the contact position radius of the V belt on the driven pulley 26 side becomes large, so that a large gear ratio (pulley ratio) is obtained. On the other hand, when the movable conical plates 22 and 34 are moved in the opposite directions, a small gear ratio is obtained contrary to the above.

Next, the hydraulic control device for the continuously variable transmission of this embodiment will be described. The hydraulic control device of this embodiment is shown in FIG.
As shown in, the oil pump 101, the line pressure regulating valve 1
02, manual valve 104, shift control valve 106, step motor 108, shift specific pressure valve 110, shift operating mechanism 11
2. Pressure modifier valve 116, constant pressure regulating valve 118, line pressure / clutch pressure switching valve 120, clutch relief valve 122, torque converter relief valve 12
4, lockup control valve 126, lockup switching valve 128, clutch control switching valve 129, shift command valve 15
It consists of 0 etc. Regarding each of the above components,
Only the part relating to the operation of the present invention will be described, and the description of the other parts will be omitted (a hydraulic control device similar to P11 to P19 of Japanese Patent Application No. 6-47564, which is a prior application by the present applicant). Is shown, see it).

The oil pump 101 sucks the oil in the tank 130 through the strainer 131 and discharges it into the oil passage 132. The hydraulic oil discharged to the oil passage 132 is supplied to the ports 102a and 102b of the line pressure regulating valve 102 and also to the port 116d of the pressure modifier valve 116, so that the line pressure regulating valve 102 has a predetermined line pressure characteristic. Is adjusted to the line pressure. The adjusted line pressure is supplied to the driven pulley cylinder chamber 32 and the port 106a of the shift control valve 106, respectively.

The pressure modifier valve 116 has a port 116a communicating with the pilot port 102c of the line pressure regulating valve 102, and a pilot port 116b supplied with the output pressure of the line pressure / clutch pressure switching valve 120 as pilot pressure. A drain port 116c communicating with the tank 130 and an input port 116d communicating with the pilot port 102b of the line pressure regulating valve 102.
A spool 116g having two lands, and a return spring 116h for biasing the spool 116g toward the pilot port 116b side. When the pilot pressure of the pilot port 116b is almost zero, the port 1
16a and the drain port 116c are in communication with each other, but the spool 116g increases as the pilot pressure increases.
Moves upward in the drawing to establish communication between the ports 116a and 116d.

The constant pressure regulating valve 118 is the line pressure regulating valve 1
The input port 11 communicated with the output port 102d of 02.
8a, an output port 118b, a pilot port 118d supplied with the output pressure of the output port 118b as a pilot pressure via a filter 118c, and a tank 130.
And a spool 118h having two lands, and a return spring 118i for biasing the spool 118h toward the pilot port 118d. The constant pressure regulating valve 118 is operated by the well-known pilot pressure regulating action of the spring 118i.
The constant hydraulic pressure corresponding to the urging force of the line pressure / clutch pressure switching valve 1 is adjusted via the output port 118b.
20, the lockup switching valve 128 and the clutch control switching valve 129.

The line pressure / clutch pressure switching valve 120 is
The input port 120a is communicated with the output port 118b of the constant pressure regulating valve 118, and the output port 120b is connected to the pilot port 116 of the pressure modifier valve 116.
b and the pilot port 122e of the clutch relief valve 122. In this line pressure / clutch pressure switching valve 120, the built-in drain port is normally closed and the modifier control pressure is output from the output port 120b to bring both the line pressure and the clutch pressure into a high pressure state.
When a drive current is supplied from the shift control device 300 (FIG. 3), the built-in drain port is opened and the output port 12
The modifier control pressure output from 0b becomes almost 0, and the line pressure and the clutch pressure are switched to a low pressure state.

The lockup switching valve 128 has an input port 128a at the output port 11 of the constant pressure regulating valve 118.
8b, and the output port 128b is connected to the shift command valve 15
0 input port 150a. In the lockup switching valve, the built-in drain port is normally opened to put the torque converter in a non-lockup state, and when the drive current is supplied from the shift control device 300, the built-in drain port is closed. , And outputs the lockup control pressure P _LU from the output port 128b. Although the lockup switching valve 128 is provided independently in this embodiment, it may be shared with the line pressure / clutch pressure switching valve 120.

The clutch control switching valve 129 has an input port 129a connected to the output port 11 of the constant pressure regulating valve 118.
8b, and the output port 129b is connected to the pilot ports 140h and 142h of the reverse brake control valve 140 and the forward clutch control valve 142. In the clutch control switching valve 129, the built-in drain port is normally opened to engage the clutch, and the shift control device 30 is operated during creep control or anti-skid control.
When a drive current is supplied from 0, the built-in drain port is closed and the clutch control pressure P _CC is output from the output port 129b.

The line pressure regulating valve 102 has an input port 102a and a pilot port 102c formed in a large diameter hole.
And an output port 102d, a pilot port 102e formed in a medium diameter hole portion communicating with the large diameter hole portion, a pilot port 102b formed in a small diameter hole portion communicating with the medium diameter hole portion, and the small diameter hole portion. A pilot port 102f formed in an oversized hole communicating with the hole, and a spool 102s having four lands corresponding to the holes,
A spool 102s is formed by a return spring 102t that biases the spool 102s toward the pilot port 102f side, and the spool 102s is moved left and right by the thrust balance between the pilot pressure supplied to each pilot port 102b, 102c, 102e and 102f and the pressure receiving area. The opening area between the port 102a and the output port 102d is adjusted to adjust the line pressure. Note that the pilot port 102b to which the line pressure is directly supplied and the pilot port 102c to which the line pressure is supplied via the pressure modifier valve 116 are configured to have different opening areas.

The clutch relief valve 122 has an input port 122a and an output port 122 formed in a large diameter hole.
d, a pilot port 122e formed in the medium diameter hole portion communicating with the large diameter hole portion, a pilot port 122c formed in the small diameter hole portion communicating with the medium diameter hole portion, and Spool 122 having three lands that fit together
k and this spool 122k to the pilot port 122
It is composed of a return spring 122m biased to the c side. Here, the input port 122a is the line pressure regulating valve 10
2 is directly connected to the output port 102d, the pilot port 122e is connected to the output port 120b of the line pressure / clutch pressure switching valve 120 and the pilot port 116b of the pressure modifier valve 116, and the pilot port 122c is connected to the oil passage 136. The output port 12 is connected to the pilot port 126j of the lockup control valve 126 and to the pilot port 102e of the line pressure regulating valve 102 via the oil passage 137.
2d communicates with the input port 124a of the torque converter relief valve 124.

The transmission specific pressure valve 110 has an input port 110.
a, an output port 110b, a drain port 110c, pilot ports 110d and 110e, a spool 110h having three lands, and a spool 1 inserted between the spool 110h and a spring stop sliding rod 110i.
It is provided with a return spring 110j that biases 10h toward the pilot port 110d side. Gear ratio valve 11
0 is connected to the input port 118a of the constant pressure regulating valve 118, the output port 110b is connected to the pilot port 102f of the line pressure regulating valve 102 and its own pilot port 110d, and the pilot port 110e is regulated. It communicates with the pilot port 118d of the pressure valve 118. In the transmission specific pressure valve 110, when the gap between the V-shaped pulley grooves of the drive pulley 16 is small, the spring stop sliding rod 110i is located at the upper position in the drawing, so the urging force of the return spring 110j is reduced and the output port The pilot pressure output from 110b becomes small, and the line pressure of the oil passage 132 regulated by the line pressure regulating valve 102 becomes small. From this state, as the V-shaped pulley groove interval of the drive pulley 16 increases, the spring Since the stop sliding rod 110i gradually moves downward, the biasing force of the return spring 110j increases, the pilot pressure output from the output port 110b gradually increases, and the line pressure in the oil passage 132 gradually increases. To do.

Next, the shift control device for the continuously variable transmission of this embodiment will be described. Shift control device 300 of the present embodiment
Are waveform shapers 308, 309, 3 as shown in FIG.
22 and an A / D converter 310 are connected to the input interface 311 and a CPU (Central Processing Unit) 313 provided between the input interface 311 and the output interface 316 and interconnected by an address bus 319 and a data bus 320. It comprises a ROM (Read Only Memory) 314 and a RAM (Random Access Memory) 315, a reference pulse generator 312 connected to the CPU 313, and a correction circuit 400. The input interface of the shift control device 300 includes a waveform shaper 30.
8, 309, 322, A / D converter 310, engine speed sensor 301, vehicle speed sensor 302, turbine speed sensor 305, throttle opening sensor 303
Are respectively connected, the shift position switch 304, the engine cooling water temperature sensor 306, and the brake sensor 307 are directly connected, the rotation speed detection sensor 401 is connected to the correction circuit 400, and the output interface 3
A motor drive circuit 317, a line pressure / clutch pressure switching valve 120, a lockup switching valve 128, and a clutch control switching valve 129 are connected to each of the sixteen (for details of the shift control device 300, refer to the above-mentioned Japanese Patent Application No. Hei. 6-47
Pp. 564-P21).

This shift control device 300 includes a step motor 108, a line pressure / clutch pressure switching valve 120, a lockup switching valve 128, and a clutch control switching valve 1.
29, etc., and executes normal shift control and the like by executing a control program (not shown) based on the input signals from the above-mentioned sensors, and by executing the control program of FIG. Line pressure of the present invention /
Performs clutch pressure switching control.

FIG. 4 is a flow chart showing a control program for the line pressure / clutch pressure switching control which is repeatedly executed at predetermined intervals by the regular interruption. First, in step 501 of FIG. 4, the clutch input torque T _in is compared with a predetermined value T _0, and if YES _in T _in > T ₀ , control proceeds to step 502, and if NO _in T _in ≦ T _0. Control proceeds to step 503. In this embodiment, the determination of the presence or absence of lockup is used to determine the magnitude of the clutch input torque. A lockup signal (for example, the vehicle speed at the time of switching between non-lockup / lockup, 10 km /
A lockup signal is output when h is exceeded), but other signals that indicate that the clutch input torque changes abruptly due to non-lockup / lockup switching are also used. Good.

In step 502, a pressure increase command is issued by turning off the line pressure / clutch pressure switching valve 120, thereby switching the line pressure characteristic to the high pressure line pressure characteristic shown in FIG. On the other hand, in step 503, a pressure reduction command is issued by turning on the line pressure / clutch pressure switching valve 120,
Thereby, the line pressure characteristic is switched to the low-pressure line pressure characteristic shown in FIG. Specifically, the line pressure characteristic is switched by supplying a drive current from the shift control device 300 to turn on or off the line pressure / clutch pressure switching valve 120.
By doing. At that time, in steps 502 and 503, the shift control device 300 corresponds to the valve means for switching the set pressure of the clutch relief valve 122.

Next, the operation of this embodiment will be described with reference to FIG. At the time of the stall in which the pressure increase command is issued, the drain pressure of the line pressure / clutch pressure switching valve 120 guided to the pilot port 122e of the clutch relief valve 122 increases, and in that case, the high pressure line pressure characteristic of FIG. The clutch relief valve 122 is set so as to be equal to the high pressure line pressure characteristic of the conventional example of No. 6. In this setting, the drain pressure of the line pressure / clutch pressure switching valve 120 is substantially zero during the normal time when the pressure reduction command is issued.
Therefore, the low pressure line pressure characteristic as shown in the figure is obtained by the pressure regulating action of the clutch relief valve 122 using the drain pressure of the line pressure regulating valve 102 as the original pressure. This low-pressure line pressure characteristic is that the line pressure at the maximum pulley ratio HIGH is 10 kgf / cm ² to 6 kg of the conventional example.
The pressure is reduced to f / cm ² , and the line pressure adjustment range is expanded as compared with the conventional example. Therefore, the drain pressure of the line pressure regulating valve 102 is 10 kgf / cm at the time of stall.
² and 6 kgf / cm ² at the normal time can be switched to two stages, and fuel consumption can be improved as desired.

When the drain pressure of the line pressure regulating valve 102 is 10 kgf / cm ² , the line pressure itself is high because it is in the stall state (for example, 46 kgf / cm ^{2 at} the minimum pulley ratio LOW). Therefore, there is no problem as the line pressure adjusting characteristic.

In this embodiment, the line pressure / clutch pressure switching valve 120, the lockup switching valve 128, and the ON / OFF switching valve are used as the clutch control switching valve, but instead, the shift control device 300 is used. It is also possible to use a duty valve whose duty is controlled based on a command from.

[0037]

As described above, the structure of claim 1 of the present invention is applied to a continuously variable transmission having a clutch relief valve whose source pressure is the drain pressure of the line pressure regulating valve, which is lower than the line pressure. When the pressure is regulated, the valve means for switching the set pressure of the clutch relief valve is provided. Therefore, when the valve means is normally turned off, for example, and the high-pressure line pressure characteristic shown in FIG. By switching the means from OFF to ON, the low pressure line pressure characteristic of FIG. 5 can be obtained. In this low-pressure line pressure characteristic, the lower limit value thereof is a predetermined value (clutch pressure;
For example, in the above-mentioned conventional example, it can be set to a value lower than 10 kgf / cm ² (for example, 6 kgf / cm ² ), and the drain pressure of the line pressure regulating valve, which has become this lower value, becomes the source of the clutch relief valve. It becomes pressure. Therefore, the fuel consumption is improved as desired and the pressure adjustment range of the line pressure is expanded.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing a power transmission mechanism used in a hydraulic control device for a continuously variable transmission according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a hydraulic control device according to a first embodiment.

FIG. 3 is a diagram illustrating a configuration of a shift control device according to a first embodiment.

FIG. 4 is a flowchart showing a control program for line pressure / clutch pressure switching control executed by the shift control device in the first embodiment.

FIG. 5 is a diagram illustrating high pressure line pressure characteristics and low pressure line pressure characteristics in the first embodiment.

FIG. 6 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 engine 12 fluid transmission device (torque converter) 13 rotary shaft 14 drive shaft 16 drive pulley 17 planetary gear mechanism 24 V belt 26 driven pulley 29 continuously variable transmission mechanism 102 line pressure regulating valve 108 step motor 110 speed change specific pressure valve 116 pressure modifier Valve 118 Constant pressure regulating valve 120 Line pressure / clutch pressure switching valve 122 Clutch relief valve 128 Lockup switching valve 129 Clutch control switching valve 300 Shift control device 301 Throttle opening sensor 302 Vehicle speed sensor

Claims (5)

[Claims] 1. A hydraulic control device for a continuously variable transmission having a clutch relief valve using the drain pressure of a line pressure regulating valve as a source pressure, comprising valve means for switching a set pressure of the clutch relief valve. A characteristic hydraulic control device for a continuously variable transmission. 2. An ON / OFF solenoid valve is used as the valve means, and the line pressure regulator valve is regulated by the ON / OFF solenoid valve and the clutch relief valve is regulated. The hydraulic control device for a continuously variable transmission according to claim 1, wherein: 3. The hydraulic control device for a continuously variable transmission according to claim 2, wherein ON / OFF switching of the solenoid valve is controlled according to a magnitude of a clutch input torque. 4. The hydraulic control device for a continuously variable transmission according to claim 3, wherein the magnitude of the clutch input torque is determined based on whether or not it is in a lockup state. 5. The continuously variable transmission according to claim 1, wherein the line pressure regulating valve regulates pressure by a signal relating to an engine torque and a signal relating to a gear ratio. Hydraulic control device.