JPH03189473A - Hydraulically actuated transmission - Google Patents

Abstract

PURPOSE:To reduce any driving loss of pumps on the whole by providing two pumps consisting of an operating pressure pump for supplying operating pressure to hydraulic actuators and a control pressure pump for supplying control pressure to control valve. CONSTITUTION:There are provided with two pumps, that is, a large capacity operating pressure pump 81 for supplying oil to obtain operating pressure to be fed to the hydraulic cylinders 414, 424 of a primary and a secondary pulleys, and a control pressure pump 150 for supplying oil to obtain control pressure acting upon control valves 82, 85, 88, 89. With this constitution, in the circumstances where only low operating pressure is required to be fed to the hydraulic cylinders 414, 424, the pressure of a large quantity of oil fed from the large capacity operating pressure pump 81 can be controlled to this low operating pressure. Accordingly, even though a driving loss on the small capacity control pressure pump 150 is increased by that portion, the driving loss of the pumps on the whole can be reduced because of reduced driving loss of the large capacity operating pressure pump 81 by a large degree.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a hydraulically operated transmission equipped with a hydraulic actuator, and particularly relates to measures for reducing driving loss of an oil pump.

(Prior Art) Conventionally, this type of hydraulically operated transmission has a hydraulic actuator for electronic control, which is operated by being supplied with operating pressure, and an operation that is supplied to the hydraulic actuator by the action of control pressure. a control valve that controls the magnitude of the pressure;
and an electromagnetic solenoid that controls the magnitude of the control pressure applied to the control valve.

By the way, in the hydraulically operated transmission as mentioned above,
For example, as disclosed in Japanese Unexamined Patent Application Publication No. 62-4958, it is equipped with a large-capacity ura pump that supplies oil to obtain the working pressure to be supplied to the hydraulic actuator, and a part of the oil supplied from this oil pump is provided. Part of the oil is used as oil to obtain the control pressure applied to the control valve, and a part of this oil is reduced to a predetermined constant pressure by a pressure reducing valve, and this oil pressure is used as the control source pressure for obtaining the control pressure.

(Problem to be Solved by the Invention) However, in the case where the oil from one oil pump is shared for both operating pressure and control pressure as in the conventional case, the present inventors have investigated the operating situation. After careful experimentation and investigation, it was discovered that there are the following drawbacks. In other words, in order to reliably transmit power without slippage regardless of the size of the transmitted torque, the magnitude of the operating pressure supplied to the hydraulic actuator needs to be varied over a wide range from high pressure to low pressure. In many cases, this is sufficient.

On the other hand, the control source pressure that is reduced by the pressure reducing valve in order to obtain the control pressure that is applied to the control valve needs to be a predetermined constant pressure that is sufficient to obtain the above-mentioned high operating pressure. Therefore, in a situation where a sufficiently low pressure value is sufficient as the operating pressure to be supplied to the hydraulic actuator, this low operating pressure often becomes a pressure value lower than the control source pressure. In such a case, the large amount of oil supplied from the large capacity oil pump, although it would normally be sufficient to have a low operating pressure,
It was found that the pressure is controlled to a high value necessary to obtain the control source pressure with a pressure reducing valve, and as a result, the drive loss of the large capacity oil pump increases as the high pressure oil is supplied.

The present invention has been made based on knowledge of the above facts, and an object of the present invention is to reduce the drive loss of the oil pump in the above-mentioned hydraulically operated transmission.

(Means for Solving the Problems) In order to achieve the above object, the present invention separately provides a pump for supplying the oil necessary to obtain the control pressure applied to the control valve.

In other words, the specific solution of the present invention is a hydraulically actuated transmission as described above, that is, a hydraulic actuator that is operated by being supplied with operating pressure, and a large amount of operating pressure that is supplied to the hydraulic actuator by the action of control pressure. It is assumed that the present invention is equipped with a control valve that controls the magnitude of the control pressure, and an electromagnetic solenoid that controls the magnitude of the control pressure applied to the control valve. Two pumps are provided: a working pressure pump that supplies oil to obtain the working pressure to be supplied to the hydraulic actuator, and a control pressure pump that supplies oil to obtain the control pressure that acts on the control valve. It is structured as follows.

(Function) With the above configuration, in the present invention, a small-capacity control pressure pump is separately provided in order to obtain the control pressure to be applied to the control valve, so that a situation where a low operating pressure is sufficient to supply the hydraulic actuator is achieved. In this case, the pressure of a large amount of water supplied from a large-capacity working pressure pump can be controlled to this low working pressure. As a result, although the driving loss of the small-capacity control pressure pump increases accordingly, the driving loss of the large-capacity working pressure pump is greatly reduced, so that the driving loss of the pump as a whole is reduced.

(Effects of the Invention) As explained above, according to the hydraulically operated transmission of the present invention, a small-capacity control pressure pump is provided separately from a large-capacity operating pressure pump. In a situation where a low pressure is sufficient, the pressure of the oil supplied from the large-capacity working pressure pump can be set to this low working pressure, and the driving loss of the entire pump can be effectively reduced.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a continuously variable transmission.

The continuously variable transmission shown in the figure basically includes a torque converter 2 connected to the output shaft 11 of the 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 the pump impeller 22. a turbine launch 23 rotatably provided inside the pump cover 21 so as to face the turbine runner 23;
The stator 24 has a stator 24 that is interposed between the pump impeller 22 and the pump impeller 22 to increase torque, and a turbine shaft 25 that is fixed to the turbine launch 23. The stator 24
is connected to the transmission case 7 via a one-way clutch 26 and a stator shaft 27. A turbine shaft 2 is provided between the turbine launch 23 and the pump cover 21.
A lock-up piston 28 is slidably attached to the lock-up piston 28, and hydraulic pressure is introduced into and discharged from a lock-up engagement chamber 29a and a lock-up opening chamber 29b formed on both sides of the lock-up piston 28. The piston 28 and the pump cover 21 are connected and opened.

The forward/reverse switching mechanism 3 is comprised of a single-binion type planetary gear mechanism for compactness.

In other words, the carrier 31, the pinion gears 32 and 32 supported by the carrier 31, and the continuously variable transmission mechanism 4 to be described later.
A sun gear 34 that is spline-coupled to the primary shaft 411 and meshes with the pinion gear 32;
a ring gear 35 meshing with the ring gear 3;
5 is connected to the turbine shaft 25 of the torque converter 2 by a spline. Further, a forward clutch 36 is provided between the ring gear 35 and the carrier 31 to connect and disconnect them, and a forward clutch 36 is provided between the carrier 31 and the transmission case 7 to selectively fix the carrier 31 to the transmission case 7. A reverse brake 37 is provided. With this configuration, the forward clutch 36 is engaged and the reverse brake 3
In the case of the forward range with 7 open, the ring gear 35 and the carrier 31 are rotationally connected, so that the rotation of the turbine shaft 25 is directly transmitted to the primary shaft 411 of the continuously variable transmission mechanism 4. On the other hand, in the case of reverse range in which the reverse brake 37 is engaged and the forward clutch 36 is released, the carrier 31 is fixed to the case 7 in a non-rotatable manner, so that the rotation of the ring gear 35 is controlled via the pinion gear 32... to the sun gear 34 and the turbine shaft 2.
5 is transmitted to the primary shaft 411 of the continuously variable transmission mechanism 4 while being reversed. Further, when both the forward clutch 36 and the reverse brake 37 are released, the turbine shaft 2
5 to the neutral and parking state) in which the driving force of the engine is no longer transmitted to the primary shaft 411 of the continuously variable transmission mechanism 4.

Further, the continuously variable transmission mechanism 4 includes a primary pulley 41,
Secondary pulley 42 and these pulleys 41 . ．． 42
It is composed of a V-belt 43 wrapped around the belt.

The primary pulley 41 includes a primary shaft 411 disposed coaxially with the turbine shaft 25, a fixed conical plate 412 fixed to the primary shaft 411, and a fixed conical plate 412 disposed opposite to the fixed conical plate 412 and attached to the primary shaft 411. It has a movable conical plate 413 that is slidably supported. When the movable conical plate 413 moves, the clamping position of the V-belt 43 changes, and the effective pitch diameter changes. That is, when the movable conical plate 413 approaches the fixed conical plate 412, the effective pitch diameter increases, and when the movable conical plate 413 moves away from the fixed conical plate 412, the effective pitch diameter decreases.

Further, the secondary pulley 42 basically has the same configuration as the primary pulley 41 described above.

That is, it has a secondary shaft 421 arranged parallel to 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 is changed.

Each movable conical plate 413 in each of these pulleys 41, 42
, 423 are provided with movable conical plates 413, 4, respectively.
Hydraulic cylinders 414 and 424 for sliding the 23 are provided. Hydraulic cylinder 4 of primary pulley 41
14, hydraulic pressure is introduced and discharged to change the gear ratio between both pulleys 41 and 42, and the secondary pulley 42
Hydraulic pressure is introduced into and discharged from the hydraulic cylinder 424 in order to maintain the tension of the V-belt 43 at an appropriate value. When hydraulic pressure is introduced into the hydraulic cylinder 414 of the primary pulley 41, the primary pulley 4
The clamping position of the V-belt 43 in the secondary pulley 42 moves to the outside and the effective pitch diameter of the primary pulley 41 increases.
2 becomes smaller, and the primary shaft 41
1 and the secondary shaft 421 changes to a small value (in the direction of speed increase). Conversely, when the hydraulic pressure is discharged from the hydraulic cylinder 414, the effective pitch diameter of the primary pulley 41 becomes smaller and the effective pitch diameter of the secondary pulley 42 becomes larger, and the gear ratio between the primary shaft 411 and the secondary shaft 421 becomes larger. (in the direction of deceleration).

To specifically explain the configuration of the hydraulic cylinder 414 of the primary pulley 41, the hydraulic cylinder 414 is connected to a first oil chamber 14a formed on the back surface of the movable conical plate 413 and an outer end of the movable conical plate 413. A movable piston 14c that presses the rear end of the member 14b, and the movable piston 14c.
and a second oil chamber 14d formed on the back surface of the first oil chamber 1.
4a and the second chamber 14d to move the movable conical plate 4.
13 in the right direction in FIG.

On the other hand, the configuration of the hydraulic cylinder 424 of the secondary pulley 42 is similar to that described above, including the first oil chamber 15a formed on the back surface of the movable conical plate 423, and the rear end of the member 15b connected to the outer end of the movable conical plate 423. A movable piston 15c that presses the
and a second oil chamber 1 formed on the back surface of the movable piston 15c.
5d, and a spring 15e that is compressed in the second oil chamber 15d and biases the movable piston 15c, and supplies hydraulic pressure to the first oil chamber 15a and the second oil chamber 15d to move the movable conical plate 423. This is a configuration in which it is moved to the left in FIG.

The hydraulic cylinder 41 of the primary pulley 41
The total pressure receiving area of the first oil chamber 14a and the second oil chamber 14d of
The area is set to be approximately twice the total pressure receiving area of the oil chamber 15a and the second oil chamber 15d.

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

Next, the torque converter 2 in the above-mentioned continuously variable transmission
, the forward clutch 36 and reverse brake 37 of the forward/reverse switching mechanism 3, and the primary pulley 41 and secondary pulley 4 of the continuously variable transmission mechanism 4.
The hydraulic circuit that controls each operation of the 2 and 2 will be explained based on FIG. 2.

The hydraulic circuit shown in the figure includes a large-capacity working pressure oil pump 81 driven by the engine 1.

The oil supplied from the oil pump 81 is first adjusted to a predetermined line pressure in the line pressure regulating valve 82, and then supplied as operating pressure to the hydraulic cylinder 424 of the secondary pulley 42 as a hydraulic actuator via the line 101. At the same time, line 1 branched from line 101
02, the pressure is finally supplied as working pressure to the hydraulic cylinder 414 of the primary pulley 41 as a hydraulic actuator.

The line pressure regulating valve 82 has a spool 8 composed of a main spool 821 and a sub spool 822 arranged in series.
It has 20. A main spool 821 and a sub-spool 822 constituting the spool 820 are connected such that one end of the sub-spool 822 is brought into contact with one end of the main spool 821. The other end of the sub spool 822! This is the contact area with the main spool 821 (cross-sectional area of the connecting part)
A large diameter portion 822a having a larger cross-sectional area is provided. At a position corresponding to the center of the main spool 821,
a pressure regulating port 823 to which the pond from the oil pump 81 is guided;
Drain port 8 communicating with the suction side of the oil pump 81
24 is provided, and when the main spool 821 moves to the left side in the figure, the pressure regulation port 823 and the drain port 824 are cut off, and when the main spool 821 moves to the right side in the figure, the pressure regulation port 823 and the drain port 824 are disconnected. When the main spool 821 moves to the right side in the figure, the pressure regulating port 823 and the drain port 824 are communicated with each other.

A first pilot chamber 825 is formed at a position corresponding to the connecting portion between the main spool 821 and the sub-spool 822, and a spring 826 that biases the main spool 821 to the left in the figure is interposed in the first pilot chamber 825. has been done.

Further, 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. These first pilot chamber 825 and second pilot chamber 827 are supplied with a control source pressure reduced to a predetermined constant pressure by a reducing valve 83, which will be described later, from a line 103 through a pilot passage 103a. A control pressure whose magnitude is adjusted by the first duty solenoid valve 91 is applied. While this control pressure acts in the same direction as the biasing force of the spring 826, the hydraulic pressure in the line 101 acts on the other end of the main spool 821 to counteract the biasing force and control pressure. The spool 820 moves according to the force relationship and communicates and disconnects the pressure regulating port 823 and the drain port 824, so that the line pressure responds to the control pressure whose magnitude is controlled by the first duty solenoid valve 91. It is controlled by the value set.

A gear ratio control valve 85 as a control valve is provided in the line 102, that is, a line communicating with the oil chambers 14a, 14d of the hydraulic cylinder 414 of the primary pulley 41 and supplying line pressure. The gear ratio control valve 85 includes a spool 851, a spring 852 that biases the spool 851 rightward in the figure, a line pressure port 853 connected to the upstream side of the line 102, and a drain boat 8.
54 and a line 104 opening on the side where the spring 852 is installed.
Reverse port 85 connected to shift valve 87 via
5, and a pilot chamber 856 formed on the opposite side of the spring 852 installation side and to which control pressure acts. The pilot chamber 856 is connected via the pitot valve 86 to a second duty solenoid valve 92 as an electromagnetic solenoid and to a pitot pressure generating means 90 that generates a pitot pressure corresponding to the rotational speed of the engine 1. There is. Therefore,
The pitot pressure generated by the pitot pressure generating means 90 and the control pressure whose magnitude is controlled by the second duty solenoid valve 92 can be selectively applied to the pilot chamber 856 by the pitot valve 86. Even when the second duty solenoid valve 92 fails, the pitot pressure can be introduced from the pitot pressure generating means 9o into the pilot chamber 856 as a control pressure.

When the gear ratio control valve 85 is moving forward (when the shift valve 87 is in any of the shift positions 2.1), hydraulic pressure is drained from the reverse port 855 through the shift valve 87. Therefore, the spool 851 moves due to the force relationship between the control pressure acting on the pilot chamber 856 and the biasing force of the spring 852, and the line pressure boat 853 and the drain boat 854 selectively communicate with the hydraulic cylinder 414 of the primary pulley 41. will be done.

In this way, when moving forward, the pilot chamber 856
By controlling the supply and discharge of hydraulic pressure to the hydraulic cylinder 414 of the primary pulley 4 according to the control pressure acting on the primary pulley 4,
The magnitude of the operating pressure acting on the hydraulic cylinder 414 of the primary pulley 41 is controlled to variably adjust the gear ratio of the continuously variable transmission.

On the other hand, when traveling in reverse (when the shift valve 87 is in the R shift position), hydraulic pressure (operating pressure to be described later) is introduced from the reverse port 855, and this operating pressure causes the spool 851 to
is fixed in a state where it is pressed to the right side in the figure. Therefore, when traveling in reverse, the oil in the hydraulic cylinder 414 of the primary pulley 41 is drained from the drain boat 854 via the pressure holding valve 98, which will be described later, thereby minimizing the effective radius of the primary pulley 41 and increasing the gear ratio to the maximum gear ratio. It is configured to be fixed and held in this state.

In addition, even in neutral and parking states (when the shift valve 87 is in the N and P shift positions), where the driving force of the engine 1 is not transmitted to the axle 61 by the forward/reverse switching mechanism 3, the same state as in reverse occurs. .

The oil of the operating pressure pump 81 whose pressure is regulated by the line pressure regulating valve 82 is supplied to the line 101 as well as to the inlet 105 . The oil supplied to the line 105 is controlled to a predetermined working pressure by the working pressure regulating valve 88 as a control valve, and then the oil supplied to the line 106 and the line 10
7.

The operating pressure regulating valve 88 includes a spool 881, a pilot chamber 882 formed at one end of the spool 881,
A spring 883 interposed in this pilot chamber 882
, a first pressure regulation boat 884 connected to line 105, and a second pressure regulation port 885 connected to line 107,
It has a drain port 886. Pilot room 88
2 is connected to the first duty solenoid valve 91 via a pilot passage 103a. Therefore, a control pressure whose magnitude is controlled by the first duty solenoid valve 91 acts on the pilot chamber 882. Then, this control pressure is applied to the spring 8.
83 acts in the same direction as the urging force, while the hydraulic pressure in the line 105 acts on the other end of the spool 881 to counteract the urging force and control pressure, and the spool 881 moves due to these force relationships. First and second pressure regulating ports 884
．． 885 and the drain port 886, the magnitude of the operating pressure supplied to the forward clutch 36 and the reverse brake 37 as a hydraulic actuator is reduced to the first duty solenoid valve as an electromagnetic solenoid. The control pressure is controlled to a value corresponding to the magnitude of the control pressure controlled at 91.

The oil of the operating pressure pump 81 supplied to the line 106 is supplied to the shift valve 87, and when the shift position is 2.1, the oil is supplied to the hydraulic chamber 36a of the forward clutch 36 of the forward/reverse switching mechanism 3 via the line 109. supplied, shift valve 87
When is in the R shift position, it is supplied to the hydraulic chamber 37a of the reverse brake 37 of the forward/reverse switching mechanism 3 via line 108, and is also supplied to the reverse port 855 of the gear ratio control valve 85 via line 104. It looks like this. On the other hand, the hydraulic oil in each hydraulic chamber 36a, 37a of the forward clutch 36 and reverse brake 37 of the forward/reverse switching mechanism 3 is discharged through the lines 109, 108 when the shift valve 87 is in the RlNP shift position. It has become so. Therefore, the forward clutch 3 of the forward/reverse switching mechanism 3
6 and the reverse brake 37 are engaged and released according to the shift position of the shift valve 87, and as described above, the gear ratio of the continuously variable transmission mechanism 4 reaches the maximum speed at the R, N, and P shift positions. The ratio is kept fixed.

Also, the working pressure pump 8 supplied to the line 107
The oil of No. 1 is supplied to the lockup engagement chamber 29g or the lockup release chamber 29b of the torque converter 2 via eight lockup control valves serving as control valves. The lock-up control valve 89 is configured such that the operation of the spool 891 is controlled by a control pressure whose magnitude is controlled by a third duty solenoid valve 93 as an electromagnetic solenoid. When the control pressure becomes lower, the spool 891 moves to the right in the figure, and hydraulic oil is supplied from the line 107 to the lockup engagement chamber 29a, and the hydraulic oil in the lockup opening chamber 29b is drained. On the other hand, as the control pressure increases, the spool 891
moves to the left in the figure, hydraulic oil is supplied from the line 107 to the self-lockup opening chamber 29b, and hydraulic oil in the lockup engagement chamber 29a is drained.

The three duty solenoid valves 91, 92 and 93 as the electromagnetic solenoids are connected to the line 103.
The line 103 is connected to @I for obtaining suppression.
A reducing valve 83 that generates J source pressure is connected. The reducing valve 83 is supplied with oil via a line 151 from a small-capacity control pressure pump 150 that is provided separately from the operating pressure oil pump 81 for human body 2, and is also supplied with oil through a line 151. Pressure (that is, control source pressure) acts on the left end of the spool 83a in the figure, and a biasing force (for example, 5 kg/cd) of the spring 83b acts on the right end of the spool 83a. The spool 83a moves left and right depending on the force relationship between the control source pressure of the line 103 and the biasing force of the spring 83b, and when the control source pressure is lower, the line 103 is connected to the line 151 of the control pressure pump 150. When the control source pressure is higher, the line 103 is connected to the drain port 83.
c Connect to lower the control source pressure, repeat the above operation,
The control source pressure is generated from the oil supplied from the control pressure pump 150, and the line pressure adjustment valve 82° gear ratio control valve 85
1 Working pressure adjustment valve 88 and lock-up control valve 8
It is configured to obtain a control pressure to be applied to 9.

As shown in FIG. 1, the specific arrangement position of the large-capacity working pressure pump 81 is above the turbine shaft 25 of the partition wall 154 between the torque converter 2 and the forward/reverse switching mechanism 3; The control pressure pump 150 is located below the turbine shaft 25 on the partition wall 154 .

The configuration of the two pumps 81, 150 is as shown in FIG. In other words, a member 15 connected to the pump impeller 22 of the torque converter 2 and rotating integrally therewith is located outside the turbine shaft 25 at a portion where the partition wall 154 is located.
A gear 156 is formed at the gear 15 (see FIG. 1).
6, the gear 81a of the operating pressure pump 81 and the gear 150a of the control pressure pump 150 mesh with each other. and,
When the gear 156 is rotationally driven by the engine 1, the gears 81a and 150a of both pumps 81 and 150 are rotationally driven, so that the oil introduced from the oil inlet port 157 is pumped, and each oil is Supply passages 81b and 150
It is configured to send the oil to the outside from the oil supply port 81C2150C via the oil supply port 81C2150C.

In addition, in FIG. 2, 94 is the pilot passage 103a when the first duty solenoid valve 91 is turned OFF.
95 and 96 are accumulators that cushion shocks when the forward clutch 36 and reverse brake 37 are engaged, respectively. 97 is a relief valve. Also,
Reference numeral 98 denotes a pressure retention valve, and when draining the pressure oil in the hydraulic cylinder 414 of the primary pulley 41, the pressure retention valve 98 does not drain all of the pressure oil, but drains the pressure oil to the extent that no pressing force is generated. The function is to leave oil in the hydraulic cylinder 414 and ensure responsiveness in increasing the oil pressure during the next oil supply.

Further, FIG. 4 shows an electric control circuit of the above-mentioned continuously variable transmission. In this figure, a control unit 110 containing a microcomputer etc. has a shift position (D) operated by the driver.

1.2. Shift position sensor 11 that detects R, N, P)
1, the primary pulley rotation speed signal from the primary rotation speed sensor 112 that detects the rotation speed np of the primary shaft 411, and the secondary pulley rotation speed signal from the secondary rotation speed sensor 113 that detects the rotation speed ns of the secondary shaft 421. Throttle opening sensor 1 that detects the boolean rotation speed signal and the throttle valve opening TVO of the engine 1
14, an engine rotation speed signal from an engine rotation speed sensor 115 that detects the rotation speed Ne of the engine 1, and a turbine rotation speed sensor that detects the rotation speed Nt of the turbine shaft 25 of the torque converter 2. 11
The turbine rotation speed signal from 6 is input.

Based on these input signals, the control unit 110 duty-controls the first to third duty solenoid valves 91, 92, and 93 as the electromagnetic solenoids, thereby controlling the line pressure regulating valve 82 as a control valve. , the operating pressure regulating valve 88, the gear ratio control valve 85, and the lock-up control valve 89.

Therefore, in the embodiment described above, when the transmission torque acting on the belt 43 of the continuously variable transmission mechanism 4 changes depending on the operating state of the engine 1, the line pressure regulating valve 82 is operated to prevent rotational slippage of the belt 43. The magnitude of the control pressure applied to is controlled by the first duty solenoid valve 91, whereby the line pressure of oil supplied from the operating pressure pump 81 is adjusted by the line pressure regulating valve 82, and this line pressure is Secondary pulley 4 as working pressure
2 hydraulic cylinder 424 first and second oil chambers 15a, 1
5d. As a result, when the line pressure is controlled to be high, the pressing force of the secondary pulley 42 increases, and the tension of the belt 43 increases.

In that case, the tension required for the belt 43, that is, the operating pressure applied to the hydraulic cylinder 424 of the secondary pulley 42 (
As shown in Fig. 5, the smaller the gear ratio and the higher the speed, the lower the control source pressure P of the line 103 is, especially when the transmitted torque is small, over almost the entire range of the gear ratio.
o (5kg/cd) (i.e. reducing valve 83
(pressure value generated at a constant pressure), 1 to 2 kg/
In many cases, the pressure value is cj. and,
In such a situation, the above control source pressure P o (5 kg
/cj) is generated by the oil of the pump 150 dedicated to control pressure, so the oil pressure of the pump 81 for operating pressure (
line pressure) to the above control source pressure P as before.

There is no need to control it as high as (5 kg/cd),
It is sufficient to control the pressure to the minimum necessary pressure value at that time of 1 to 2 kg/c/. As a result, as shown in Fig. 6 under a constant engine speed, the small capacity control pressure pump 1
Although the pump loss increases by 50, the pump loss of the large-capacity working pressure pump 81 can be reduced to less than the conventional pump loss (in the case of small transmission torque) shown by the broken line in the same figure, so the pump loss as a whole can be reduced. This makes it possible to improve engine output and fuel efficiency.

In the above embodiment, the present invention is applied to a continuously variable transmission, but the present invention is not limited to this, and can of course be similarly applied to an automatic transmission with three or four gears.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 shows a specific configuration of a continuously variable transmission, FIG. 2 shows a hydraulic control circuit, and FIG. 3 shows a specific configuration of an operating pressure pump and a control pressure pump. 4 is a block diagram showing the electrical control system, and FIGS. 5 and 6 are operation explanatory diagrams. 41...Primary pulley (hydraulic actuator),
414... Hydraulic cylinder, 42... Secondary pulley (hydraulic actuator), 424... Hydraulic cylinder, 81... Working pressure pump, 82... Line pressure regulating valve (control valve), 85... Gear ratio control valve (control valve), 91... first duty solenoid valve (electromagnetic solenoid), 92... second duty solenoid valve (electromagnetic solenoid), 150... pump for control pressure. 2 others Figure 3

Claims (1)

[Claims] (1) A hydraulic actuator that operates when operating pressure is supplied, a control valve that controls the magnitude of the operating pressure supplied to the hydraulic actuator through the action of control pressure, and a control valve that controls the magnitude of the control pressure that is applied to the control valve. an electromagnetic solenoid for controlling the hydraulic actuator, an operating pressure pump for supplying oil for obtaining operating pressure to be supplied to the hydraulic actuator, and a control pressure pump for supplying oil for obtaining control pressure to be applied to the control valve; A hydraulically operated transmission characterized by comprising: