JPH0750602Y2 - Hydraulic servo device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a hydraulic servo device for engaging and disengaging a predetermined friction element of an automatic transmission.

(Prior Art) In recent years, electronic control has been implemented in automatic transmissions mounted on automobiles, and automatic shifting of an optimum pattern is performed based on the vehicle speed or load state detected by various sensors to improve acceleration performance and I try to improve the economy. Along with this, a hydraulic servo device that engages and disengages friction elements of an automatic transmission is required to gradually operate friction elements such as a shift clutch and a brake at optimum timing to promote smooth gear shifting. .

A conventional hydraulic servo device of this type is, for example, Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent Publication No. 20855. This one is designed to engage and release a predetermined friction element by selectively supplying hydraulic pressure. As shown in FIG.
A piston 3 for biasing operation is housed in a cylinder 2 formed in the housing 1, and a servo chamber 4 is defined in the cylinder 2. Further, a one-way valve 5 capable of introducing outside air from the outside of the servo chamber 4 to the housing 1 above the servo chamber 4 is mounted, and the hydraulic pressure in the servo chamber 4 is equal to or less than a predetermined value. The valve 5 is designed to open when the pressure drops to 0. The valve 5 includes a valve seat plug 6 fitted in a housing 1 and a spherical valve body 7 that is loosely inserted into the valve seat plug 6 to open and close a valve seat portion 6a of the valve seat plug 6.
And a gap S for ventilation that communicates with the servo chamber 4 and the outside thereof is formed between the housing 1 and the valve seat plug 6. The gap S allows the air compressed in the upper part of the servo chamber 4 to be ventilated to the outside air when the hydraulic pressure of the servo chamber 4 rises above a predetermined value and the valve 5 is closed. Is designed to prevent the oil liquid from leaking when the torque rises.
It is designed to mitigate the rise in oil pressure inside.

(Problems to be solved by the invention) However, in such a conventional hydraulic servo device, the shift timing is influenced by the size of the gap S formed between the housing 1 and the valve seat plug 6. Since the ventilation amount is determined when the pressure in the servo chamber 4 is high, it is difficult to suppress the leakage of the oil liquid while actually securing the appropriate ventilation amount at this time. In other words, in order to secure both an appropriate amount of ventilation and the prevention of leakage of oil liquid, it is necessary to make the channel length longer than the cross-sectional area of the gap S to form a choke. There is a problem that such a ventilation path cannot be formed between the valve seat plug 6 into which the valve 7 is loosely inserted and the housing 1. For this reason, for example, if the cross-sectional area of the gap S is set to be small in order to prevent the leakage of the oil liquid, even if the liquid level in the servo chamber 4 begins to drop when the hydraulic pressure in the servo chamber 4 is released, the inside of the servo chamber 4 will be reduced. Compressed air is difficult to be discharged through the gap S, and it is necessary to additionally discharge the oil liquid by the amount of expansion of the air remaining in the servo chamber 4. Therefore, as shown in FIG. The fall of the pressure in the chamber 4 was delayed, resulting in a time lag, and it was not possible to promote the optimum shift.

(Object of the Invention) Therefore, the present invention is optimized by forming a ventilation path with a thin shaft-shaped shaft member and a case, and making the ventilation path a choke with an optimum path length according to the axial length of the shaft member. The purpose is to ensure an appropriate amount of ventilation to promote a proper gear shift and to prevent leakage of oil liquid.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is a hydraulic servo device that engages and disengages a predetermined friction element of an automatic transmission, the case being substantially horizontal in the case. And a piston that is slidably stored in the direction and that defines a pressure chamber with the case,
A system that is provided above the predetermined friction element and that fastens or releases the predetermined friction element by the movement of the piston that receives the pressure of the pressure chamber, and a system that is provided above the stem and that is outside the pressure chamber. A ventilation passage formed in the case to allow ventilation, a shaft insertion hole extending in the moving direction of the piston and opening to the upper side of the pressure chamber, and the shaft insertion. A tubular member having a small diameter thin shaft inserted into the hole and having a diameter larger than that of the thin shaft, and defining a predetermined gap with the shaft insertion hole; It is characterized in that the path length of the ventilation path can be appropriately set according to the axial length of the shaft member.

(Operation) In the present invention, the ventilation passage is formed by the shaft insertion hole that extends in the moving direction of the piston and opens to the upper side of the pressure chamber, and the shaft member that is inserted into the shaft insertion hole with a predetermined gap. It is formed in a tubular shape, and the path length of the tubular ventilation path is appropriately set according to the axial length of the shaft member. Therefore, the ventilation path becomes a choke with an optimum path length, an appropriate amount of ventilation for promoting an optimum gear shift is secured, and leakage of oil liquid is reliably prevented.
In addition, since the shaft member has a small diameter thin shaft inserted into the shaft insertion hole, the shaft member can be reliably positioned in the shaft insertion hole in the axial direction, and the shaft member has a fixed length. By varying the shaft member with respect to the thin shaft with respect to the insertion hole, the path length of the ventilation path can be easily set. further,
A stem is provided on top of a given friction element,
Since the ventilation passage is provided above the stem, the shaft insertion hole does not interfere with the friction element, and the length of the shaft insertion hole can be sufficiently secured, which is formed by the shaft member and the shaft insertion hole. It is possible to widen the adjustment width of the length of the tubular ventilation passage. On the other hand, when the stem is provided below the predetermined friction element, the distance between the shaft insertion hole located above the stem and the friction element becomes short, and the shaft insertion hole and the friction element interfere with each other. However, the length of the shaft insertion hole cannot be sufficiently secured, and the adjustment width of the air passage cannot be widened.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

1 and 2 are views showing a first embodiment of a hydraulic servo device according to the present invention.

First, the configuration will be described. In FIG. 1, 11 is a predetermined friction element of an automatic transmission (not shown in detail), for example, a band brake, and the band brake 11 has a band 11B and a brake drum 11D. The band brake 11 is used as a reaction force element of a front planetary gear and a rear planetary gear (not shown), and is released at the first and third speeds of the D range, which is the running range of the automatic transmission,
The sun gear, etc. of the front planetary gear that is fastened at the 2nd and 4th speeds and connected to the brake drum 11D is fixed. The band brake 11 includes a hydraulic servo device as an example.
12 is mounted, and the hydraulic servo device 12 can selectively be hydraulically supplied to engage and release the band brake 11 as described later.

The hydraulic servo device 12 is housed in the case 13 and the case 13 so as to be slidable in a substantially horizontal direction, and defines a release side pressure chamber 14 and a fastening side pressure chamber 15 together with the case 13.
And a second piston 19 that divides the engagement side pressure chamber 15 into a second speed chamber 17 and a fourth speed chamber 18, and is provided above the band brake 11D so that the first piston 16 and the second piston 19 can be stopped. The inserted stem 21, the first return spring 22 that is compressed between the case 13 and the first piston 16, and the first piston
A second return spring compressed between the 16 and the second piston 19.
It has 23 mag. The case 13 includes a part of the automatic transmission case C and a pair of cylinder members 24 and 25. An anchor end pin 26 is fixed to the automatic transmission case C coaxially with the stem 21. The stem 21 and the anchor end pin 26 are engaged with the band struts 11a and 11b attached to the both ends of the band 11B at their respective opposing tips, and when the stem 21 approaches and separates from the anchor end pin 26, the band 11B. Is fastened to and released from the brake drum 11D.

The release side pressure chamber 14 is supplied with the release side hydraulic pressure through an oil passage (not shown) formed in the automatic transmission case C. The release side hydraulic pressure is, for example, a third speed pressure circuit such as a 2-3 shift valve (not shown). From the 3rd and 4th speed. The hydraulic pressure on the engaging side is supplied to the second speed pressure chamber 17 through an oil passage (not shown) formed in the automatic transmission case C, and the hydraulic pressure on the engaging side is, for example, a 1-2 shift valve not shown. It is supplied from the second speed pressure circuit at the second to fourth speeds. The 4th speed pressure chamber 18 has 4
The hydraulic pressure (4th speed) on the engagement side is supplied from the speed circuit through the oil passage 25a and the like. The first return spring 22 and the second return spring 23 are connected to the first piston 16 and the second return spring 23.
The piston 19 is constantly biased toward the release side, and the first piston
The 16 and the second piston 19 receive these urging forces and the hydraulic pressure corresponding to the pressure receiving areas by the above-mentioned hydraulic pressures to move the stem 21 toward and away from the anchor end pin 26. That is, the stem 21 engages and releases the band brake 11 by the movement of the first piston 16 and the second piston 19 which receive the pressure of the release side pressure chamber 14, the second speed pressure chamber 17 and the fourth speed pressure chamber 18. ing.

On the other hand, the automatic transmission case C is provided with a communication hole 31 for communicating the release side pressure chamber 14 with the outside of the release side pressure chamber 14, and the communication hole 31 extends in the moving direction of the first piston 16. And is opened to the uppermost side of the release side pressure chamber 14, and is formed above the stem 12 and includes a shaft insertion hole 32 and an opening hole 33 opened to the brake drum 11D side and connected to the shaft insertion hole 32. . A thin shaft 34 having a slit or the like formed at the end on the release side pressure chamber 14 side is provided in the shaft insertion hole 32, and a cylindrical ventilation path 35 is formed by the thin shaft 34 and the shaft insertion hole 32. Has been done.
Specifically, the thin shaft 34 is formed in a stepped shape in the middle part and has two different diameters, and the slightly large diameter insertion portion 34a on the thin shaft 34 side.
The (shaft member) is inserted into the shaft insertion hole 32 with a small predetermined gap, so that the ventilation path 35 having a longer path length than the cross-sectional area is formed. In addition, the air passage 35 is formed by the insertion portion 34a of the thin shaft 34.
The path length of the ventilation path 35 can be set as appropriate by using the thin shaft 34 having the path length according to the length (axial length) of the insertion section 34a and the insertion section 34a having different lengths. Then, as described above, when the first piston 16 moves to the fastening side or the releasing side of the band brake 11, the air compressed in the releasing side pressure chamber 14 passes through the ventilation passage 35 and is outside the releasing side pressure chamber 14. When the oil liquid supplied into the release side pressure chamber 14 reaches the ventilation passage 35 while being aerated to the ventilation passage 35 due to the viscosity of the oil liquid.
A pressure drop is promoted in the vicinity of the opening of 35 to prevent the oil liquid from leaking to the outside. That is, the air passage 35
Can be vented from the release side pressure chamber 14 to the outside of the release side pressure chamber 14.

In FIG. 1, reference numeral 36 denotes a bowl-shaped plug that prevents the thin shaft 34 from coming off, and the plug 36 is fitted into the shaft insertion hole 32 so as to engage with the slit 37 of the thin shaft 34 and allow ventilation. Has been done. Further, in the figure, various seal members are attached to the outer peripheral portions of the first piston 16, the second piston 19, and the cylinder members 24 and 25.

Next, the operation will be described.

First, when the automatic transmission is switched from the non-traveling range to the traveling range, for example, the D range, the operation of various friction elements is promoted according to the vehicle speed or the load state, and the required automatic transmission is performed.

In this state, if the automatic shift is performed from the first speed to the second speed, for example, the hydraulic pressure (second speed pressure) on the engagement side is supplied to the second speed pressure chamber 17 from the 1-2 shift valve or the like, and the second speed pressure chamber is supplied. The first piston 16 gradually moves forward against the urging force of the first return spring 22 and the like so that the first piston 16 presses the stem 21 in response to the increase in the hydraulic pressure of 17 while promoting the ventilation through the ventilation passage 35. Band brake 11 is engaged. Next, assuming that the automatic speed is changed from the second speed to the third speed as the vehicle speed increases, etc., with the hydraulic pressure on the engagement side supplied to the second speed pressure chamber 17, the 2-3 shift valve or the like releases the pressure chamber on the release side. The hydraulic pressure on the release side (third speed pressure) is supplied to 14. At this time, the air in the release side pressure chamber 14 is
The first piston 16 receives the oil pressure of the release side pressure chamber 14 and the second speed pressure chamber 17 due to the difference in the pressure receiving area of the first piston 16 after being ventilated through 35 and the liquid level in the release side pressure chamber 14 rising. Is gradually retracted, and the band brake 11 is gradually released. It should be noted that a relatively small hydraulic pressure applied to the second piston 19 is applied to the stem 21 when shifting to the fourth speed.
Therefore, a smooth shift is promoted during the above shift.

On the other hand, if the speed is changed from the third speed to the first speed as the vehicle speed decreases, the second speed (engagement) pressure and the third speed (release) pressure decrease as time t elapses, as shown in FIG. At this time, when the liquid level in the release-side pressure chamber 14 decreases, the ventilation passage 35 is a choke with an optimum path length, so that an appropriate amount of ventilation is promoted through the ventilation passage 35. Therefore, it is possible to prevent the third speed pressure from falling rapidly as shown by the broken line, and to prevent the band brake 11 from being released by the stem 21 with a large time lag as in the conventional case, and to promote smooth gear shifting at optimum timing. .

Further, even when the oil liquid in the release side pressure chamber 14 reaches the ventilation passage 35 during each of the above shifts, the pressure drop in the ventilation passage 35 as a choke is large due to the viscosity of the oil liquid. It is prevented from leaking to the outside.

As described above, in the present embodiment, the thin shaft 34 is inserted into the shaft insertion hole 32 to form the ventilation passage 35 as a choke, and the optimum passage length of the ventilation passage 35 is set according to the length of the insertion portion 34a. Because you can
It is possible to secure an appropriate amount of ventilation for promoting the optimum gear shift and to reliably prevent the oil liquid from leaking to the outside. Further, since the insertion portion 34a is formed in the small diameter thin shaft 34 inserted in the shaft insertion hole 32, the insertion portion 34a in the shaft insertion hole 32 is formed.
In addition to being able to reliably position the
By changing the insertion portion 34a with respect to the thin shaft 34 with respect to the shaft insertion hole 32 having a constant length, the path length of the ventilation path 35 can be easily set.

Further, since the stem 21 is provided above the band brake 11D and the ventilation path 35 is provided above the stem 21, the shaft insertion hole 32 is prevented from interfering with the band brake 11D, and the shaft insertion is prevented. The length of the hole 32 can be sufficiently secured, and the adjustment width of the path length of the cylindrical ventilation path 35 formed by the insertion hole 34a and the shaft insertion hole 32 can be widened.

3 and 4 are views showing a second embodiment of the present invention. In this embodiment, a position below the ventilation passage 15 of the first embodiment, that is, a position spaced downward from the top of the release side pressure chamber 14 is shown. In the airway
There are 45.

In FIG. 3, a ventilation path 45 is provided with a shaft insertion hole 42 which is a portion of the communication hole 41 formed in the automatic transmission case C on the release side pressure chamber 14 side and a thin shaft inserted into the shaft insertion hole 42. Thin shaft similar to 34
It is formed in a tubular shape by the insertion portion 44a of 44. Also in this embodiment, since the ventilation passage 45 as the choke is provided, the time lag is eliminated as shown in FIG.
It is possible to obtain the same effect as that of the embodiment, and moreover, by always leaving a predetermined amount or more of air above the release side pressure chamber 14, the action as an accumulator for the first piston 1 can be exhibited.

(Effects) According to the present invention, the air passage extends in the moving direction of the piston and is opened to the upper side of the pressure chamber, and the shaft member inserted in the shaft insertion hole with a predetermined gap. Since it is formed in a tubular shape by and the path length of the tubular ventilation path can be appropriately set according to the axial length of the shaft member, the ventilation path is a choke with an optimal path length, and an optimal gear shift is performed. It is possible to secure an appropriate amount of ventilation for urging and surely prevent the oil liquid from leaking. Further, since the shaft member has the small diameter thin shaft inserted into the shaft insertion hole, the shaft member can be reliably positioned in the shaft insertion hole in the axial direction and has a constant length. By changing the shaft member with respect to the thin shaft with respect to the shaft insertion hole, the path length of the ventilation path can be easily set. Furthermore, since the stem is provided above the predetermined friction element and the ventilation path is provided above the stem,
The shaft insertion hole can be prevented from interfering with the friction element, and the length of the shaft insertion hole can be secured sufficiently. The path length of the cylindrical ventilation path formed by the shaft member and the shaft insertion hole. The adjustment range of can be widened.

[Brief description of drawings]

1 and 2 are views showing a first embodiment of a hydraulic servo device according to the present invention. FIG. 1 is a sectional view thereof, FIG. 2 is an operation characteristic diagram showing its action, and FIGS. FIG. 3 is a view showing a second embodiment of a hydraulic servo device according to the present invention, FIG. 3 is a sectional view thereof, FIG. 4 is an operation characteristic diagram showing its action, and FIGS. 5 and 6 show a conventional hydraulic servo device. FIG. 5 is a sectional view, and FIG. 6 is an operation characteristic diagram for explaining the problem. 11 …… Band brake (friction element), 12 …… Hydraulic servo device, 13 …… Case, 14 …… Release side pressure chamber (pressure chamber),
16 …… First piston (piston), 21 …… Stem, 33,
34 …… Narrow shaft, 32,42 …… Shaft insertion hole, 34a, 44a …… Insertion part (shaft member), 35,45 …… Ventilation passage.

Claims (1)

[Scope of utility model registration request] 1. A hydraulic servo device for engaging and releasing a predetermined friction element of an automatic transmission, which is housed in a case and slidably in a substantially horizontal direction in the case to define a pressure chamber together with the case. A piston and a stem that is provided above the predetermined friction element and that fastens or releases the predetermined friction element by the movement of the piston that receives the pressure of the pressure chamber, and a stem that is provided above the stem and that moves from the pressure chamber to the pressure chamber. A vent passage formed in the case so as to be able to ventilate to the outside, the vent passage extending in the moving direction of the piston, and a shaft insertion hole opened to the upper side of the pressure chamber, A shaft member having a small diameter small shaft inserted into the shaft insertion hole and having a diameter larger than the small shaft, and forming a predetermined gap between the shaft insertion hole and the shaft member; The length of the tubular ventilation passage is set to the shaft length of the shaft member. Flip and hydraulic servo device being characterized in that to enable appropriately set.