JPH0348380B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a line pressure control device for a transmission.

(B) Prior Art A conventional line pressure control device for a transmission is disclosed in, for example, Japanese Patent Application Laid-open No. 77155/1983. In this transmission line pressure control device, line pressure is regulated in accordance with throttle pressure (and gear ratio), and throttle pressure is controlled based on engine intake pipe negative pressure. That is, the throttle pressure is set to decrease as the engine intake pipe negative pressure increases. However, the line pressure is not allowed to fall below a predetermined minimum value.
That is, once the line pressure decreases to a predetermined minimum value, it is thereafter maintained at the minimum value even if the engine intake pipe negative pressure increases. An example of such hydraulic characteristics is shown in FIG.

(c) Problems to be Solved by the Invention The line pressure characteristics obtained by the conventional transmission line pressure control device are set as shown in FIG. 10 for the following reasons. In other words, the engine torque varies depending on the engine intake pipe negative pressure.
It changes as shown by the solid line in the figure. Negative pressure 0 (in addition,
When using a turbocharger, maximum torque is achieved at a predetermined positive pressure value), and maximum torque is achieved at a predetermined negative pressure, e.g.
The torque becomes 0 at 400mmHg, and the negative pressure increases further in the engine braking state (reverse drive state). Even under engine braking conditions, the capacity of clutches, pulleys, etc. of transmissions such as automatic transmissions and continuously variable transmissions is required to accommodate the reverse driving force.
As shown by the broken line in the figure, it is necessary to secure a capacity that can transmit a value obtained by turning the negative part of the engine torque to the positive side. Therefore, the line pressure characteristics are set high so that the torque indicated by the broken line can be transmitted even in a region where the negative pressure in the engine intake pipe is large. Therefore, when the negative pressure is around 400 mmHg, the throttle pressure and the line pressure regulated accordingly are higher than necessary. This area is used during steady driving and is the area that is used the longest, but if the line pressure is higher than necessary in this area, oil pump loss increases and transmission efficiency decreases. This is a major cause of this. This has a particularly large effect in the case of a V-belt continuously variable transmission in which transmission efficiency is greatly affected by line pressure. The present invention aims to solve the above problems.

(d) Means for solving the problems The present invention provides throttle pressure and line pressure characteristics that approximate the required torque characteristics by using two diaphragms with opposite characteristics. Solve the above problems. That is, the transmission line pressure control device according to the present invention has the following features:
A first diaphragm whose pushing force toward the throttle valve decreases as the intake pipe negative pressure increases (that is, the degree of vacuum increases); and a first diaphragm provided between the first diaphragm and the spool of the throttle valve. a second diaphragm whose pushing force toward the throttle valve increases as engine intake pipe negative pressure increases; and a second rod provided between the second diaphragm and the spool of the throttle valve. , the first diaphragm has the characteristic of applying a force to the spool of the throttle valve via the first rod when the negative pressure in the engine intake pipe is below a first predetermined value, and the second diaphragm has the characteristic of applying force to the spool of the throttle valve through the first rod. When the negative pressure is equal to or higher than a second predetermined value, a force is applied to the spool of the throttle valve via the second rod. It is also possible to provide a spring that constantly exerts a force on the spool of the throttle valve.

(E) Effect When the engine intake pipe negative pressure is equal to or higher than the first predetermined value (here, the first predetermined value = the second predetermined value), the force of the first diaphragm is applied to the throttle via the first rod. The throttle pressure, which acts on the spool of the valve and is regulated thereby, decreases as the engine intake pipe negative pressure increases. When the negative pressure is at the first predetermined value (=second predetermined value), the throttle pressure becomes zero. Next, when the engine intake pipe negative pressure exceeds a first predetermined value, the force from the first diaphragm no longer acts, and the force from the second diaphragm acts via the second rod. As a result, the throttle pressure increases as the engine intake pipe negative pressure increases. As a result, throttle pressure characteristics as shown in FIG. 4 can be obtained. If the line pressure is adjusted using this throttle pressure, the line pressure characteristics will be as shown in FIG. 5, for example. If a spring is provided that always applies a force to the spool of the throttle valve, the throttle pressure will not fall below a predetermined value corresponding to the force of the spring, so that the throttle pressure characteristics shown in FIG. 9 can be obtained. In addition, if the first predetermined value is smaller than the second predetermined value, the throttle pressure characteristic will be as shown in FIG. 7, for example, and the corresponding line pressure characteristic will be as shown in FIG. 8. Also, the pressure receiving area of the first diaphragm and the second
By making the pressure receiving area of the diaphragm different, the slopes of the throttle pressure lines around the first predetermined value and the second predetermined value can be made different from each other.

(F) Example (First Example) FIG. 1 shows a first example of the present invention. This line pressure control device includes a vacuum diaphragm unit 10, a throttle valve 12, and a line pressure regulating valve 1.
It has 4. The vacuum diaphragm unit 10 has two diaphragms in the casing 16, that is, a first diaphragm 18 and a second diaphragm 20. It is divided into three chambers, a chamber 24 and an atmospheric pressure chamber 26. 1st
Negative pressure chamber 22 and second negative pressure chamber 24 are connected to the engine intake pipe via piping 28. Atmospheric pressure chamber 2
6 is released to the atmosphere. First diaphragm 1
8 is subjected to a downward force in FIG. 1 by a first spring 30. Further, an upward force is applied to the second diaphragm 20 in FIG. 1 by a spring 32. The vacuum diaphragm unit 10 has a metal fitting 3 integrated with the casing 16.
4 is attached to the valve body 36 at the position where the throttle valve 12 is provided. The throttle valve 12 is comprised of a spool 40 fitted into the valve hole 38. Valve hole 3
8 is provided with five ports 38a to 38e. Ports 38a and 38c communicate with an oil passage 42 which is a throttle pressure circuit, and port 38b
is in communication with the line pressure oil passage 44, and the port 38
d and port 38e are drain ports. The spool 40 is connected to the port 38 in the pressure regulating position shown in FIG.
By draining a portion of the oil supplied from port 38d to port 38d, the oil pressure in port 38a, that is, the oil pressure in oil passage 42, is regulated so as to balance the force acting on spool 40 from above in FIG. Spool 40 and vacuum diaphragm unit 1
A first rod 46 is provided between the spool 40 and the second diaphragm 18.
A hollow second rod 4 is provided between the diaphragm 20 and the diaphragm 20.
8 is provided. The second rod 48 is integrally connected to the second diaphragm 20, for example by adhesive, and is connected to the casing 16.
A sealing member 50 is provided between the second negative pressure chamber 24 and the second negative pressure chamber 24 to maintain an airtight state. The line pressure regulating valve 14 is a well-known pressure regulating valve that regulates the oil discharged from the oil pump 52 (line pressure in the oil passage 44) according to the throttle pressure supplied from the oil passage 42 to the port 54 and the force of the spring 56. .

Next, the operation of this embodiment will be explained. Negative pressure in the engine intake pipe is relatively low (close to atmospheric pressure)
In this case, since the pressure difference between the second negative pressure chamber 24 and the atmospheric pressure chamber 26 is small, the first
The force based on this pressure difference that acts downward in the figure is small, and the second diaphragm 20
It is in a state where it is pushed upward by. Therefore, the second rod 48 is separated from the spool 40 and exerts no force on the spool 40, as shown enlarged in FIG. On the other hand, since the pressure difference between the first negative pressure chamber 22 and the atmospheric pressure chamber 26 is also small, the first
The upward force in the figure is smaller than the force of the first spring 30, and the first diaphragm 18 is pushed downward by the first spring 30.
This pushing force is inversely proportional to the applied negative pressure. The pushing force acting on the first diaphragm 18 is transmitted to the spool 40 via the first rod 46 as shown in FIG. Since the throttle valve 12 regulates the oil pressure in the oil passage 42, that is, the throttle pressure, in accordance with the force acting on the spool 40 from the first rod 46, the throttle pressure is a negative pressure as shown in the part indicated by the symbol a in FIG. It gradually decreases as it increases. When the negative pressure reaches a first predetermined value (400 mmHg in the example shown in FIG. 4), the force acting on the spool 40 from the first rod 46 becomes zero, and the throttle pressure also becomes zero. On the other hand, when the negative pressure reaches a second predetermined value (=first predetermined value), a force based on the pressure difference that acts downward on the second diaphragm 20 is applied to the spring 3.
When the negative pressure exceeds a second predetermined value, the second rod 48 comes into contact with the spool 40 and begins to apply a pushing force, as shown in FIG. On the other hand,
As the first diaphragm 18 moves upward in FIG. 1 due to an increase in the pressure difference acting on the first diaphragm 18, the first rod 46 is in a state in which no force is applied to the spool 40, as shown in FIG. Become.
The force transmitted from the second diaphragm 20 to the spool 40 via the second rod 48 increases as the negative pressure increases. Therefore, the throttle valve 12
The throttle pressure in the oil passage 42, which is regulated by the engine pressure, also increases in accordance with the increase in engine intake pipe negative pressure. That is, it becomes as shown by the symbol b in FIG. in the end,
The throttle pressure in the oil passage 42 obtained by the vacuum diaphragm unit 10 and the throttle valve 12 has characteristics as shown in FIG. The throttle pressure in the oil passage 42 acts on the port 54 of the line pressure regulating valve 14, and the line pressure regulating valve 14 regulates the line pressure in the oil passage 44 according to the force caused by this throttle pressure and the force exerted by the spring 56. The pressure has characteristics as shown in FIG. 5, for example. The line pressure characteristics shown in FIG. 5 correspond to the theoretically required torque transmission capacity. As a result, the line pressure becomes appropriate over the entire engine intake pipe negative pressure range, eliminating unnecessary high pressure areas, reducing loss in the oil pump 52, and in the case of a V-belt continuously variable transmission, the transmission Increased efficiency.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention. This second
In this embodiment, a spring 60 is added to the first embodiment shown in FIG. 1, and a first diaphragm 18 is added.
The first predetermined value at which the pushing force of the second diaphragm 20 becomes 0 is set as a negative pressure value smaller than the second predetermined value at which the pushing force of the second diaphragm 20 becomes 0.
This is similar to the example. The spring 60 always exerts a force on the spool 40 in a downward direction in FIG. 6, that is, in a direction opposite to the throttle pressure of the port 38a. As a result, a constant throttle pressure can be obtained in a region where neither the first diaphragm 18 nor the second diaphragm 20 is applying force to the spool 40 (that is, between the first predetermined value and the second predetermined value). become (7th
(The part indicated by the symbol c in the figure). As a result, the throttle pressure characteristics as shown in FIG. 7 and the line pressure characteristics as shown in FIG. 8 can be obtained. This eighth
The line pressure characteristics shown in the figure also approximate the required torque characteristics shown in FIG. Therefore, the same effects as in the first embodiment can be obtained. Note that this second
In the embodiment, if the first predetermined value is equal to the second predetermined value, the throttle pressure characteristic will be as shown in FIG.

(G) Effects of the Invention As explained above, according to the present invention, the throttle valve is controlled by combining two diaphragms whose pushing force change characteristics with respect to changes in negative pressure are opposite to each other. Throttle pressure and line pressure that decrease and then increase as engine intake pipe negative pressure increases can be obtained, and appropriate line pressure characteristics can be achieved in accordance with the required torque. This reduces oil pump loss and improves transmission efficiency in the case of a V-belt continuously variable transmission, resulting in a highly efficient transmission.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the first embodiment of the present invention, Fig. 2 is an enlarged view showing the state of the first and second rods when the negative pressure is small, and Fig. 3 is a diagram showing the state of the first and second rods when the negative pressure is large. FIG. 4 is a diagram showing the throttle pressure characteristics obtained by the first embodiment. FIG. 5 is a diagram showing the line pressure obtained by the first embodiment. FIG. 6 is a diagram showing the second embodiment of the present invention, FIG. 7 is a diagram showing the throttle pressure characteristics obtained by the second embodiment, and FIG. 8 is a diagram showing the throttle pressure characteristics obtained by the second embodiment. FIG. 9 is a diagram showing another throttle pressure characteristic obtained by the second embodiment. FIG. 10 is a diagram showing engine torque characteristics and conventional line pressure characteristics. be. 12... Throttle valve, 14... Line pressure regulating valve, 18... First diaphragm, 20... Second diaphragm, 22... First negative pressure chamber, 24... Second
Negative pressure chamber, 40...spool, 46...first rod, 48...second rod, 60...spring.

Claims (1)

[Scope of Claims] 1. Line pressure control of a transmission having a throttle valve that is in a pressure regulating state at a predetermined spool position and outputs throttle pressure, and a line pressure regulating valve that regulates line pressure in accordance with the throttle pressure. The device includes: a first diaphragm whose pushing force toward the throttle valve decreases as intake pipe negative pressure increases;
A first rod provided between the first diaphragm and the spool of the throttle valve, a second diaphragm whose pushing force toward the throttle valve increases as the engine intake pipe negative pressure increases, and the second diaphragm. a second rod provided between the first diaphragm and the spool of the throttle valve; The second diaphragm is characterized in that it applies a force to the spool of the throttle valve via the second rod only when the engine intake pipe negative pressure is equal to or higher than a second predetermined value. Transmission line pressure control device. 2. The line pressure control device for a transmission according to claim 1, further comprising a spring that always applies a force in the direction of increasing the pressure regulation value to the spool of the throttle valve.