JPH0338517Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a line pressure control device for a continuously variable transmission.

(B) Prior Art A conventional line pressure control device for a continuously variable transmission is disclosed in, for example, Japanese Patent Laid-Open No. 140129/1983. The line pressure control device of this continuously variable transmission is configured to regulate line pressure in accordance with engine load (throttle pressure) and gear ratio. Therefore, when the engine load and gear ratio are constant, the line pressure is always the same regardless of other operating conditions.

(c) Problems that the invention aims to solve However, in the conventional line pressure control device for continuously variable transmissions as described above, it is difficult to maintain the optimum line pressure in all cases according to changing operating conditions. However, there is a problem in that the line pressure must be set higher than necessary. In other words, when the engine rotational speed (i.e., the rotational speed of the drive pulley) is increasing, torque corresponding to the rotational moment of the flywheel, drive pulley, and other rotating members is absorbed in order to accelerate them, and the continuously variable transmission The torque transmitted through is reduced. Therefore, in this case, the required line pressure will be lower than the line pressure required when the rotational speed is constant. Conversely, when the engine speed is decreasing, the transmitted torque increases due to the energy stored in rotating members such as the flywheel, so the required line pressure is lower than that required when the engine speed is constant. higher than the pressure. In this way, the required line pressure fluctuates with changes in engine speed, but conventionally the line pressure has been adjusted to prevent a shortage of line pressure even when the required line pressure is the highest. is set high to give some leeway. Therefore, under normal operating conditions, the line pressure is higher than necessary, increasing the oil pump loss, reducing the transmission efficiency of the V-belt, and further reducing the durability of the V-belt. The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention solves the above problems by increasing or decreasing the line pressure from the reference value in accordance with the direction of change in the rotational speed of the drive pulley. That is, when the line pressure control device for a continuously variable transmission according to the present invention detects an increase in the rotational speed of the drive pulley, it applies a signal pressure to the line pressure regulating valve to reduce the line pressure, thereby reducing the rotational speed of the drive pulley. The line pressure changing means is provided for applying a signal pressure to the line pressure regulating valve to increase the line pressure when detected.

(E) Effect When the rotational speed of the drive pulley increases, the line pressure changing means applies a signal pressure to the line pressure regulating valve to lower the regulating value. As a result, the line pressure regulated by the line pressure regulating valve is lower than the reference state. On the other hand, when the engine speed decreases, the line pressure increases, contrary to the above. When the rotational speed of the drive pulley is constant, the line pressure changing means does not operate, and the line pressure is maintained at the reference state.

(F) Example (First Example) FIG. 2 shows a power transmission mechanism of a continuously variable transmission.
In this continuously variable transmission, the rotation of the input shaft 2 is controlled by the drive pulley 6, the V-belt 50, and the driven pulley 5 by engaging the forward clutch 4 or the reverse clutch 24.
1, etc. to the output shafts 76 and 78. This continuously variable transmission includes an input shaft 2, a forward clutch 4, a drive pulley 6, a drive shaft 8, an oil pump 10, a drive gear 12, a driven gear 14, a rotary groove 16, an oil reservoir 18, a pitot tube 20, and a subshaft. 2
2. Reverse clutch 24, gears 26, 28, 3
0, 32 and 34, piston chambers 36 and 38, fixed conical plate 40, drive pulley cylinder chamber 42, movable conical plate 44, rotating groove 46, oil pool 47,
Pitot tube 48, V belt 50, driven pulley 51,
Driven shaft 52, fixed conical plate 54, driven pulley cylinder chamber 56, spring 57, movable conical plate 5
8, gear 60, ring gear 62, differential case 6
4, pinion gears 66 and 68, differential device 70,
Side gears 72 and 74 and output shafts 76 and 7
8, but a detailed explanation of these will be omitted. Regarding the structure of the parts whose explanations are omitted, please refer to the Japanese Unexamined Patent Application Publication No.
59-75840 "Control device for hydraulic automatic clutch".

FIG. 1 shows a hydraulic control device for a continuously variable transmission.
The hydraulic control device for this continuously variable transmission includes an oil pump 10, a line pressure regulating valve 102, and a manual valve 10.
4, speed change control valve 106, clutch complete engagement control valve 108, speed change motor (step motor) 110,
Shift control mechanism 112, throttle valve 114, starting valve 116, start adjustment valve 118, maximum gear ratio holding valve 120, reverse inhibitor valve 1
22, a lubricating valve 124, a tank 130, an accumulator 900, etc., which are connected to each other as shown in the figure, and a forward clutch 4.
, the piston chamber 38 of the retraction clutch 24, the driving pulley cylinder chamber 42, the driven pulley cylinder chamber 56, and the pitot tubes 20 and 48. A detailed explanation of valves and the like other than the accumulator 900 and the like that are directly related to the present invention will be omitted. It should be noted that the parts whose explanation is omitted are described in the above-mentioned Japanese Patent Application Laid-Open No. 75840/1983.

This hydraulic control device is provided with an accumulator 900 which is a line pressure changing means. The accumulator 900 is composed of a piston 902 and a spring 904. An oil chamber 906 of the accumulator communicates with an oil passage 908. Oil road 90
8 communicates with the port 146a of the line pressure regulating valve 102. In addition, the oil passage 908 has an orifice 91
0 to the oil passage 214. Oil road 2
14 is supplied with hydraulic pressure corresponding to the engine rotation speed from a pitot tube 20. The oil passage 214 communicates with the port 146f of the line pressure regulating valve 102. The difference in area between the land 148b and the land 148a of the line pressure regulating valve 102 is made equal to the area of the end surface of the land 148e.

Next, the operation of this embodiment will be explained.

First, when the engine speed is constant, the oil pressure supplied from the pitot tube 20 to the oil passage 214 is constant. The oil pressure of the oil passage 214 is controlled by the orifice 910.
It is also supplied to oil passage 908 via. Oil road 9
Due to the hydraulic pressure acting on the oil chamber 906 from 08, the piston 902 of the accumulator 900 is stopped at a position where the spring 904 is compressed by a predetermined amount. The oil pressure in the oil passage 214 acts on the port 146f of the line pressure regulating valve 102, while the oil pressure in the oil passage 908 acts on the port 146a. The oil pressures of port 146f and port 146a are equal, and the pressure-receiving area of spool 148 is also the same, and both oil pressures act on spool 148 in opposite directions, so both forces cancel each other out, and spool 148 has the same pressure-receiving area. The forces involved do not act. That is,
The line pressure is regulated to a predetermined pressure regardless of the engine speed.

When the engine speed increases from this state,
The oil pressure in the oil passage 214 increases. Therefore, the oil pressure acting on the port 146f immediately increases. However, the oil pressure in the oil passage 908 does not rise immediately because of the accumulator 900. That is, the oil passage 21
4 to the oil passage 908 through the orifice 910, the increase in the oil pressure in the oil passage 908 is caused by the relaxation effect of the accumulator, that is, the action in which the piston 902 compresses the spring 904 and moves in response to the rise in oil pressure. is delayed. Therefore,
The oil pressure at the port 146a of the line pressure regulating valve 102 is lower than the oil pressure at the port 146f. Therefore, a force acting to the left in FIG. 1 acts on the spool 148, and the line pressure regulated by the line pressure regulating valve 102 is lower than that of the port 146f and port 146a compared to the steady case described above. The value will be lower by the difference in oil pressure. As a result, when the engine speed increases, the line pressure becomes lower than the steady reference state.

Conversely, when the engine rotation speed decreases, the oil pressure in the oil passage 214 decreases. As a result, the oil pressure at the port 146f of the line pressure regulating valve 102 immediately decreases. However, the oil pressure in the oil passage 908 is such that the piston 902 of the accumulator 900
Since it moves by the force of 04 and pushes out the oil, it does not decrease immediately. For this reason, the line pressure regulating valve 10
The oil pressure of the second port 146a is higher than the oil pressure of the port 146f. As a result, contrary to the above case, the line pressure regulated by the line pressure regulating valve 102 becomes a high value.

After all, when the engine speed increases, the line pressure becomes high, and conversely, when the engine speed decreases, the line pressure becomes low. This results in
It is possible to obtain line pressure characteristics that correspond to fluctuations in transmitted torque based on the moment of inertia of a flywheel, etc. Therefore, the line pressure can be set to the minimum necessary value not only when the engine speed is constant but also when the engine speed fluctuates, reducing oil pump loss and reducing V
It is possible to improve the transmission efficiency of the belt and further improve its durability.

(Second example) FIG. 3 shows a second embodiment of the present invention.

This second embodiment uses a solenoid valve 950 to obtain the same effect as the first embodiment. Regarding this second embodiment, only the parts directly related to the present invention will be explained, and
Explanation of the same contents as those described in Publication No.-140129 will be omitted. solenoid valve 95
0 is capable of controlling the opening and closing of the oil passage 952 communicating with the port 146a of the line pressure regulating valve 102 according to the amount of energization. The oil passage 952 is connected via an orifice 954 to an oil passage 164 to which a constant oil pressure is supplied. The solenoid valve 950 is controlled by a control device 300 composed of a microcomputer or the like based on a control routine as shown in FIG. The control routine shown in FIG. 4 is executed by periodically interrupting the control routine shown in the above-mentioned Japanese Patent Laid-Open No. 59-140129, which controls the clutch at the time of starting and controls the gear ratio. It is processed. First, read the current engine speed N(t) (step 960), then calculate the difference ΔN between this N(t) and the engine speed N(t-1) stored in step 968 of the previous routine. calculate. (ibid. 962). Next, the duty ratio is searched based on this ΔN (see 9
64). The duty ratio is set to be proportional to ΔN, and the duty ratio when ΔN is 0 is set to 50%. Next, a predetermined current is output based on the retrieved duty ratio (see 96
6), then set the current engine rotation speed N(t) to N
(t-1) (968) and return. This ensures that a constant current is always supplied to the solenoid valve 95 when the engine speed is not changing.
0, and the solenoid valve 950 is supplied to the oil passage 952.
Maintain the oil pressure at a constant level. As a result, the line pressure regulated by the line pressure regulating valve 102 becomes the reference state. When the engine speed increases from this state, ΔN becomes a positive value, and the duty ratio becomes
Increase by more than 50%. This causes the solenoid valve 9
The current supplied to 50 increases, and the oil pressure in oil passage 952 increases. For this reason, the line pressure regulating valve 102
The hydraulic pressure acting on the port 146a increases compared to the reference state, and the line pressure increases. Conversely, when the engine speed decreases, the duty ratio becomes smaller than 50%, and the line pressure decreases, contrary to the above. That is, the same effect as in the first embodiment can be obtained.

(g) Effects of the invention As explained above, according to the invention, the line pressure is adjusted according to the direction of change in engine speed, so the line pressure can always be set to the minimum necessary value. This reduces oil pump loss and improves V-belt transmission efficiency.
Furthermore, the durability of the V-belt can be improved.

[Brief explanation of the drawing]

Fig. 1 shows the first embodiment of the invention, Fig. 2 shows the power transmission mechanism of a continuously variable transmission, Fig. 3 shows the second embodiment of the invention, and Fig. 4 shows the power transmission mechanism of the continuously variable transmission. It is a figure which shows the control routine of 2nd Example. 102... Line pressure regulating valve, 900... Accumulator, 950... Solenoid valve.

Claims (1)

[Claim for Utility Model Registration] Line pressure control of a continuously variable transmission in which the gear ratio between the driving pulley and the driven pulley is determined according to the ratio of the oil pressure in the cylinder chamber of the driving pulley and the oil pressure in the cylinder chamber of the driven pulley. When the device detects an increase in the rotational speed of the drive pulley, it applies a signal pressure to the line pressure regulating valve to reduce the line pressure, and when it detects a decrease in the rotational speed of the drive pulley, it applies a signal pressure to the line pressure regulating valve to reduce the line pressure. 1. A line pressure control device for a continuously variable transmission, comprising a line pressure changing means for applying a signal pressure that increases the line pressure.