JPH03376A - Band brake servo device of automatic transmission - Google Patents

Abstract

PURPOSE:To reduce shift shock and oil pump loss by disposing an electromagnetic solenoid valve for communicating and intercepting between a draft chamber and an engaging side oil pressure chamber in the draft chamber. CONSTITUTION:The rear part of a piston 22 is fitted to the inside of an inner housing 29 in such a manner as to be capable of sliding to form an engaging side first oil pressure chamber 30 and an engaging side second oil chamber 31. A cover 33 is mounted in a position, backward of the inner housing 29, of a cylinder 21 to form a draft chamber 34 between the cover and the inner housing 29. The draft chamber 34 is communicated to a drain and the atmosphere, and an electromagnetic solenoid valve 40 for communicating and intercepting between the draft chamber 34 and the engaging side second oil pressure chamber 31 is disposed in the draft chamber 54. Hence, shift shock and oil pump loss can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a servo device for operating a band brake of an automatic transmission.

(Prior Art) A conventional band brake servo device for an automatic transmission is shown in FIG. This conventional band brake servo device has an engagement side hydraulic chamber 4 formed between a cover 2 fixed to the rear part of a cylinder 1 and a piston 3.
By introducing pressure oil from an oil passage (not shown) inside, the piston 3 is slid toward the forward side against the spring 5, thereby urging the plunger 6 toward the forward side via the spring 7 and causing it to protrude. By pressing the brake band 8 onto the brake drum 9, the rotation of the brake drum 9 is stopped. Note that lO in Fig. 8 is a ventilation chamber for allowing the piston 3 to slide.

When releasing the brake, the engagement side hydraulic chamber 4 is connected to the drain, and pressure oil is introduced into the release side hydraulic chamber 11 between the piston 3 and the cylinder 1 to slide the piston 3 toward the backward side. Brake band 8 by plunger 6
The pressure bond between the brake drum 9 and the brake drum 9 is released. An example of a band brake servo device for a conventional automatic transmission as described above is the Utility Model Application No. 80-9933.
There is one described in Publication No. 6.

Figure 3 shows an example in which the band brake servo device described above is used as a servo device for the second brake B1 of an automatic transmission with three forward speeds.The engagement of each gear stage of this automatic transmission is as follows. As shown in the table below.

In the automatic transmission described above, upshifting from second speed to third speed is performed by turning off second brake B1 and turning on direct clutch C2. This is because smoother control can be achieved by performing 2-3 speed upshift control using a one-way clutch, but using a one-way clutch is disadvantageous in terms of cost and weight.

That is, during forward driving with forward clutch C1 turned on, the line pressure is changed to second brake B1.
is introduced into the engagement side hydraulic chamber 4 of the band brake servo device to turn on the second brake B1, thereby setting the second speed state. Then, from this second speed state, line pressure is supplied to the direct clutch C2 to turn it on, and at the same time, the line pressure is introduced into the release side hydraulic chamber 11 of the band brake servo device and the engagement side hydraulic chamber 4 is connected to the drain. Then, turn off the second brake B1 and perform an upshift to 3rd gear. At this time, by timing the on/off of direct clutch C2 and second brake B1, upshift control similar to that when using a one-way clutch is performed.

In addition, Figure 4 shows 3 of the hydraulic control circuit of the automatic transmission in Figure 3.
It shows the speed state, and 12 in the figure 1 is the B1 servo device,
13 is a pressure regulator valve, 14 is a manual valve, 15 is a 1-2 shift valve, 113 is a 2
-3 shift valve, 17 is a low coast modulator valve, 18 is an accumulator for Bl, and 19 is an accumulator for C1.

(Problem to be solved by the invention) However, in an automatic transmission using a conventional band brake servo device as described above, when a one-way clutch is used, the one-way clutch itself is sensitive to torque and accurate timing control is not possible. However, it is necessary to perform timing control by controlling the lap amount of the second brake B1 and the direct clutch C2. That is, 2-3
When the quick upshift is a power-on upshift, the second brake B1 and the direct clutch C2 must overlap slightly, whereas when the quick upshift is a power-off shift, it is necessary to almost underlap. Here, overlap refers to a state in which both brake B1 and clutch C2 are engaged, and underlap refers to a state in which a neutral state exists between when brake B1 is turned off and clutch C2 is turned on. In order to control the amount of overlap in this way, conventionally, the amount of overlap when upshifting from 2nd to 3rd gear power is set at full throttle is determined, and the amount of overlap is determined when the band brake servo device shown in Fig. 2 engages and releases the hydraulic chamber 4. A predetermined pressure receiving area difference was set between the side hydraulic chamber 11 and the side hydraulic chamber 11. However, since hydraulic pressure is introduced into the engagement-side hydraulic chamber 4 of the band brake servo device in the 2nd speed state and the brake B1 is engaged, a large pressure receiving area must be provided to prevent the brake band of the brake B1 from slipping. However, if this value is set too large, the servo diameter becomes too large and it cannot be configured in practice.On the other hand, if the pressure receiving area of the engagement side hydraulic chamber is set small to reduce the servo diameter, the line pressure during 2nd gear will increase. This has the drawback of increasing the shift shock at the time of 1->2 upshift.

Also, in the conventional case, this was done to ensure underlap during power-off and upshifts.

The line pressure at the time of shifting was controlled to be small using a throttle valve, etc., but when performing such hydraulic control, considering the shift shock reduction when upshifting from 1st to 2nd gear, the line pressure when shifting to 2nd and 3rd gears is reduced. A dilemma has arisen in that the shift shock becomes worse, and if the reduction of shift shock during upshift from 2nd to 3rd gear is considered, the shift shock during upshift from 1st to 2nd gear becomes worse. If an attempt is made to reduce both shift shocks, there is a problem in that the hydraulic control circuit becomes complicated due to the addition of orifice control valves, timing valves, and the like.

The present invention has been made in order to eliminate the drawbacks of the conventional band brake servo device for an automatic transmission. In other words, it is easy to control hydraulic pressure to reduce shift shock in automatic transmissions.

Further, it is an object of the present invention to provide a band brake servo device which can use a conventional valve body as is without causing an increase in the size of the device, and has a simple structure at low cost.

(Means for Achieving the Object) In order to achieve the above object, the present invention includes a piston that slides integrally with a plunger that biases the band brake in a cylinder, and engages with both sides of the piston. In the band brake servo device, a side hydraulic chamber and a release side hydraulic chamber are formed, and the band brake is engaged and disengaged by sliding a piston by introducing pressure oil into the engagement side hydraulic chamber or the release side hydraulic chamber. Install the inner housing at the rear of the cylinder piston.

The rear part of the piston is slidably fitted inside this inner housing, and a first hydraulic chamber on the engagement side is surrounded by the inner wall of the cylinder, the piston, and the inner housing, and a first hydraulic chamber on the engagement side is surrounded by the inner wall surface of the inner housing and the rear wall surface of the piston. A second hydraulic chamber on the engagement side is formed.

Pressure oil from the outside is supplied to the first hydraulic chamber on the engaging side, and the first hydraulic chamber on the engaging side and the second hydraulic chamber on the engaging side are communicated through an orifice, and a cover is installed at the rear of the inner housing of the cylinder. is attached to form a ventilation chamber between the inner housing and the ventilation chamber is communicated with the drain and the atmosphere, and communication between the ventilation chamber and the second hydraulic chamber on the engaging side is established or interrupted within the ventilation chamber. It is characterized by the installation of an electromagnetic solenoid valve.

(Function) The band brake servo device of the automatic transmission described above operates when the magnetic solenoid valve is de-energized or energized to cut off communication between the second hydraulic chamber on the engaging side and the ventilation chamber. When pressure oil is introduced into the hydraulic chamber, the piston moves to the first position on the engagement side.
The band brake is energized by the hydraulic pressure in the hydraulic chamber and the second hydraulic chamber to move forward toward the engagement side and engage the band brake. In addition, when the electromagnetic solenoid valve is energized or de-energized to communicate the second hydraulic chamber on the engagement side and the ventilation chamber, the first hydraulic pressure chamber on the engagement side is
When pressure oil is introduced into the hydraulic chamber, the second hydraulic chamber on the engaging side is connected to the drain via the ventilation chamber, so no hydraulic pressure is generated in the second hydraulic chamber, and the hydraulic pressure in the first hydraulic chamber on the engaging side is Since only the orifice acts on the piston,
The band brake can be engaged with a smaller force than in the case described above.

Therefore, by turning on and off the electromagnetic solenoid valve, for example, in the case of a power-on upshift, the band brake is engaged with a large force due to the hydraulic pressure in both the first hydraulic chamber and the second hydraulic chamber on the engagement side, and the band brake is engaged when the power is turned off. In the case of an upshift, by controlling the pand brake to be engaged with a small force generated only by the hydraulic pressure in the first hydraulic chamber on the engagement side,
Furthermore, by controlling the timing of engagement of other engagement elements, it is possible to reduce shift shock and oil pump loss.

In addition, when releasing the band brake by introducing pressure oil into the release side hydraulic chamber of the band brake servo device and urging the piston toward the release side, the electromagnetic solenoid valve is controlled on/off or duty-controlled. By controlling the discharge speed of pressure oil from the hydraulic chamber, the speed and timing of releasing the band brake can be finely adjusted.

(Example) Hereinafter, the present invention will be described in further detail based on an example shown in two drawings.

FIG. 1 shows an embodiment of a band brake servo device according to the present invention, in which a piston 2 is installed in a cylinder 21.
2 are slidably fitted together.

A release hydraulic chamber 23 is formed between the piston 22 and the inner wall of the cylinder. And this release side hydraulic chamber 2
3, a first spring 24 is interposed between the piston 22 and the inner wall of the cylinder to bias the piston 22 toward the release side (left side in the drawing).

The rear end of the plunger 25 is passed through the center of the piston 22 and is prevented from falling out by a snap ring 26.
Plate 27 locked to a step formed in the center of 5
A second spring 28 is interposed between the piston 22 and the piston 22, and urges the plunger 25 in the forward direction (rightward in the drawing). The tip of the plunger 25 penetrates the outer wall of the cylinder and is engaged with an engagement fitting 8a of a brake band 8 wrapped around the outer circumferential surface of the brake drum 9.

The above configuration is almost the same as that of a conventional servo device.

An inner housing 29 is non-slidably fitted behind the piston 22 in the cylinder 21, and the piston 22 is fitted into the cylinder portion formed inside the inner housing 29.
The rear part of the is slidably fitted. An engagement-side first hydraulic chamber 30 is formed between the flange portion 22a of the piston 22 and the front end portion of the inner housing 29 on the outer peripheral side of the rear portion of the piston. An engagement-side second hydraulic chamber 31 is formed therebetween.

Further, a hole 22b is formed in the rear part of the piston 22 to communicate the first hydraulic chamber 30 on the engagement side and the second hydraulic chamber 31.
A plug 32 with an orifice is attached to the hydraulic chamber side end of this hole 22b.
is attached, and pressure oil is supplied into the first hydraulic chamber 30 on the engagement side from an oil passage (not shown) formed on the outer wall of the cylinder 21 through the hole 22b and the orifice of the plug 32. It is designed to be introduced into the second hydraulic chamber 31 on the mating side.

Furthermore, a cover 33 is fixed to the rear of the inner housing 29 of the cylinder 21, and a ventilation chamber 34 is formed between the cover 33 and the inner housing 29. In this ventilation chamber 34, an electromagnetic solenoid valve 40 is installed inside the cover 33, and a ball valve 40 is installed inside the cover 33.
1 opens and closes a communication hole 42 passing through the engagement side second hydraulic chamber 31 and the ventilation chamber 34. This electromagnetic solenoid valve 4o.

In the de-energized state, the plunger 43 is biased by the spring 44 to press the ball valve 41 and the communication hole 42 is closed; in the energized state, the plunger 43 presses the ball valve 41.
is slid against the spring 44, the pressure on the ball valve 41 is released, and the communication hole 42 is opened.

Note that the two ventilation chambers 34 are connected to the atmosphere and a drain through holes 21a formed in the outer wall of the cylinder 21.

Next, operate the band brake servo device mentioned above.

An explanation will be given by taking as an example a case in which it is used in the automatic transmission shown in FIGS. 3 and 4.

As can be seen from the table above, when running in second speed, it is necessary to engage the second brake B1, and at this time the electromagnetic solenoid valve 40 is kept in a non-energized state. In this state, the communication hole 42 of the electromagnetic solenoid valve 4o is blocked by the ball valve 41.

The piston 22 is urged toward the forward side (the engagement side) by the hydraulic pressure in the first hydraulic chamber 30 and the second hydraulic chamber 31 on the engagement side, and the pressure receiving area of the piston 22 increases, so that the band torque capacity of the second brake B1 increases. is increased, and because of this, the line pressure at this time may be low, so the oil bomb broth is reduced.

Further, during the 1st-2nd speed upshift, the electromagnetic solenoid valve 40 is de-energized in the case of a power-on upshift, and the electromagnetic solenoid valve 40 is energized in the case of a power-off upshift. Therefore, when powering on and upshifting, the electromagnetic solenoid valve 4
Since the communication hole 42 of 0 is blocked, the hydraulic pressure in the first hydraulic chamber 30 on the engagement side and the hole 22b and the plug 32 with an orifice are
The piston 22 is urged toward the engagement side with a large pressure by the hydraulic pressure introduced into the engagement side second hydraulic chamber 31 via the hydraulic pressure. In addition, in the case of power-off/upshift, the communication hole 42 of the electromagnetic solenoid valve 40 is opened and the pressure oil in the second hydraulic chamber 31 on the engagement side is discharged to the drain via the ventilation chamber 34. The piston 22 is urged only by the hydraulic pressure in the side first hydraulic chamber 30. Note that in the energized state of the electromagnetic solenoid valve 40 , even if the second engagement side hydraulic chamber 31 is connected to the drain, the oil pressure in the first engagement side hydraulic chamber 30 is maintained by the orifice of the plug 32 .

As described above, by controlling the on/off state of the electromagnetic solenoid valve 40, it is possible to set the effective pressure receiving area of the piston 22 corresponding to the upshift state.
This makes it possible to reduce shift shock during upshifts.

Further, in the case of an intermediate state between a power-on upshift and a power-off upshift, more detailed shift control is possible by controlling the duty frII of the 'W1 magnetic solenoid valve 40 on/off.

Furthermore, when upshifting from 2nd to 3rd speed, pressure oil is introduced into the release side hydraulic chamber 23 of the band brake servo device, and into the engagement side first hydraulic chamber 30 and second hydraulic chamber. By stopping the introduction of pressure oil to 3I, the engagement of the second brake B1 is released. At this time, if the electromagnetic solenoid valve 40 is energized, the pressure oil in the second hydraulic chamber 31 on the engagement side is transferred to the communication hole 42. Since it is also discharged from the ventilation chamber 34 through the air, the speed at which the second brake Bl is disengaged becomes faster. Therefore, in this case as well, by controlling the on/off of the electromagnetic solenoid valve 40 in the power-on upshift or the power-off upshift, the timing with the engagement of the direct clutch C2 is determined, and the gear is shifted. It becomes possible to reduce the shock.

In addition, in the case of downshifting from 3rd to 2nd speed, it is necessary to engage the second brake B1 slowly when the vehicle speed is high, and conversely to do it quickly when the vehicle speed is low. By controlling the on/off state of 40, fine timing control can be performed and shift shocks can be reduced.

Although the case where the band brake servo device according to the present invention is used in the automatic transmissions shown in FIGS. 3 and 4 has been described above, the same applies to the case where it is used in other automatic transmissions.

Further, in the above embodiment, an electromagnetic solenoid valve is used that cuts off communication between the ventilation chamber and the second hydraulic chamber on the engaging side when the power is not supplied, but an electromagnetic solenoid valve that operates in the opposite manner may also be used. .

(Effects of the Invention) As described above, the present invention adjusts the timing of engagement and disengagement of the band brake and the magnitude of the force at the time of engagement, depending on the state at the time of gear shifting. whether it is a shift between gears, an upshift or a downshift, or an upshift with power on.
It can be finely controlled in response to various conditions such as upshifting or power-off upshifting, and can greatly contribute to reducing shift shock and oil pump loss.

In addition, the conventional valve body can be used as is, and there is no risk of increasing the size of the device.

A low-cost servo device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an embodiment of the present invention, Fig. 2 is a side sectional view showing a conventional example, Fig. 3 is a skeleton diagram showing one row of gear trains of an automatic transmission, and Fig. 4 is a sectional view showing a conventional example. FIG. 4 is a hydraulic control circuit diagram of the automatic transmission shown in FIG. 3; 8... Brake band 21... Cylinder 23... Release side hydraulic chamber 29... Inner housing 30... Engagement side first hydraulic chamber 31... Engagement side second hydraulic chamber 32...・Plug with orifice 33...Cover 34...Vent chamber 40...
・Electromagnetic solenoid valve 41...Ball valve 42...Communication hole 9...
Brake drum 22... Piston 25... Plunger Applicant Aisin Seiki Co., Ltd. Agent Patent attorney Asahi Kato Figure 2

Claims (1)

[Claims] A piston that slides integrally with a plunger that biases the band brake is fitted into the cylinder, and an engagement-side hydraulic chamber and a release-side hydraulic chamber are formed on both sides of this piston. In a band brake servo device that engages and disengages a band brake by sliding a piston by introducing pressure oil into a side hydraulic chamber, an inner housing is attached to the rear of the piston of the cylinder, and the piston is mounted inside the inner housing. A first hydraulic chamber on the engagement side whose rear portions are slidably fitted and surrounded by the inner wall of the cylinder, the piston, and the inner housing, and a second hydraulic chamber on the engagement side surrounded by the inner wall surface of the inner housing and the rear wall surface of the piston. The pressure oil from the outside is supplied to the first hydraulic chamber on the engagement side, and the first hydraulic chamber on the engagement side and the second hydraulic chamber on the engagement side are communicated via an orifice, and the pressure oil is supplied to the first hydraulic chamber on the engagement side and the second hydraulic chamber on the engagement side through an orifice. A cover is attached to the rear position to form a ventilation chamber between the inner housing, the ventilation chamber is communicated with the drain and the atmosphere, and the ventilation chamber and the second hydraulic chamber on the engagement side are communicated with each other within the ventilation chamber. A band brake servo device for an automatic transmission, which is characterized by having an electromagnetic solenoid valve that switches on and off.