JPH0126420B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a creep prevention device for an automatic transmission for a vehicle.

(Prior art) For vehicles equipped with automatic transmissions that have fluid couplings such as torque converters, it is common practice to set the gear shift lever to the drive position while the vehicle is stopped with the engine running at idle, such as when waiting at a traffic light at an intersection. If this happens, a so-called creep phenomenon occurs in which the vehicle attempts to move forward against the driver's will due to the drag torque of the fluid coupling. This creep phenomenon is undesirable from the viewpoint of improving fuel efficiency because it imposes a drag torque load on the engine during idling operation. Therefore, during such idling, the transmission is automatically put into a neutral state (neutral state) to cut off power transmission between the engine and the wheels,
As a result, it is desirable to reduce the opening degree of the engine throttle valve by the amount that the drag torque load is reduced, thereby improving fuel efficiency.

For this reason, creep prevention devices have been known that keep the transmission capacity of the starting friction engagement element (low gear clutch) at almost zero during idling, but there are generally two types of creep prevention devices. That is,
One type bypasses the pressure oil supplied to the starting frictional engagement element to the pressure oil tank without passing through the starting frictional engagement element, and the other type dams the pressure oil supply line to supply pressure to the starting frictional engagement element. This is a type that limits oil supply.

(Problem to be Solved by the Invention) There is no problem with the former bypass type, but in the latter dam type creep prevention device, the starting friction engagement element changes the power from the power cutoff state for creep prevention. In order to prevent an unpleasant shock when starting due to the time delay before returning to the transmission state, during idling, the hydraulic pressure of the hydraulic servo of the starting frictional engagement element is controlled by the return spring built into it. The time delay is shortened by applying preload to a level that is approximately in balance with the biasing force. However, this preload acts as residual pressure when switching the shift lever of an automatic transmission from the drive position to the neutral position or reverse position, resulting in poor switching response.
This tendency is particularly remarkable in cold weather.

The present invention has been made in view of the above circumstances, and has an extremely simple configuration that shortens the time delay until the starting frictional engagement element returns from the power cutoff state for creep prevention to the power transmission state, and starts the vehicle. Although it can prevent unpleasant shocks at times,
An object of the present invention is to provide a creep prevention device for an automatic transmission for a vehicle that has good responsiveness when switching a shift lever from a drive position to a neutral position or a reverse position.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an index representing the output of the engine, which is interposed in the communication oil passage that communicates the hydraulic source and the hydraulic servo of the starting friction engagement element. A hydraulic control device that operates based on a throttle pressure corresponding to the magnitude of the hydraulic pressure, an engine rotational speed signal, and a brake signal to control the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value. By controlling this to substantially zero, creep of the vehicle is prevented, and furthermore, by storing a predetermined preload force in the hydraulic servo when the engine is idling, the starting frictional engagement element changes from the power cut-off state to the power state. In a creep prevention device for a vehicle automatic transmission which is configured to shorten the time delay until returning to a transmission state, a bypass oil path that bypasses the hydraulic control device is interposed in the communication oil path, and the bypass oil A one-way valve is interposed in the roadway to allow hydraulic oil to flow from the starting frictional engagement element to the hydraulic source side, and when the shift lever of the vehicle is switched from the drive position to the neutral position or the reverse position. Preferably, the preload force stored in the hydraulic servo is released to the hydraulic pressure source via the bypass oil passage.

(Function) When the shift lever is switched from the drive position to the neutral or reverse position, the preload force stored in the hydraulic servo of the starting friction engagement element is released to the manual valve side, and the automatic transmission is shifted from the drive position to the neutral position. Switching to the position or the retreat position is performed with good responsiveness.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows a schematic configuration of a drive system of a vehicle equipped with an automatic transmission with four forward speeds and one rear speed to which the present invention is applied.
A known automatic transmission A that combines a torque converter (fluid coupling) T and a gear transmission M having first to fourth speed clutches _C1 to _C4 is connected to the automatic transmission A, and the output of the automatic transmission A is as follows. The power is transmitted to the drive wheels W, W' via the differential Df. In addition,
The first speed clutch _C1 becomes a frictional engagement element for starting.

Figure 2 shows the configuration of the hydraulic control circuit of the automatic transmission A, in which P is a hydraulic pump (hydraulic source), its suction port is connected to the hydraulic tank R, and its discharge port is the hydraulic oil path 2. is connected to regulator valve Vr through. The outlet of the regulator valve Vr is connected to the torque converter T via an oil line 3, and the surplus hydraulic pressure of the regulator valve Vr is transferred to the torque converter T.
to prevent cavitation by pressurizing the inside. regulator valve
Hydraulic oil path 2 regulated to a predetermined pressure by Vr
The oil pressure becomes the line pressure Pl. An oil passage 4 branched from the hydraulic oil passage 2 is connected to a shift lever (not shown), and a manual valve Vm is connected to a shift lever (not shown).
The manual valve Vm has a neutral position, a drive position, and a reverse position, and when in the drive position, communicates the oil passage 4 with the output oil passage 5 of the manual valve Vm. Hydraulic oil path 2
A throttle valve Vt and a governor valve Vg are connected to the first pilot oil passage 6, and the throttle valve Vt outputs a throttle pressure Pt proportional to the amount of depression of the accelerator pedal as an index representative of the output of the engine E.
Output to. Governor valve Vg outputs governor pressure Pg proportional to vehicle speed to second pilot oil passage 7. The output oil passage 5 of the manual valve Vm is connected to the 1st-2nd speed shift valve V ₁ , and the communication oil passage 8 on one side (manual valve Vm side) branched from the output oil passage 5 is connected to a hydraulic control device and a hydraulic control device to be described later. The other (first gear clutch C ₁
(hydraulic servo 9 side) via the connecting oil passage 8'
It is connected to the hydraulic servo 9 of the speed clutch _C1 .

The 1st-2nd speed shift valve V ₁ is connected to the 2nd-3rd speed shift valve V ₂ via an oil passage 11 having a throttle 10.
The speed-3rd speed shift valve V ₂ shifts to the 3rd speed through the oil passage 12.
They are respectively connected to the 4-speed shift valve _V3 . 2nd speed-
The 3rd speed shift valve _V2 is connected to the hydraulic servo 14 of the 2nd speed clutch _C2 via an oil path 13, and the 3rd-4th speed shift valve _V3 is connected to the hydraulic servo of the 3rd speed clutch _C3 via an oil path 15. 16 and oil passage 17, respectively, to a hydraulic servo 18 of the fourth speed clutch _C4 .
A return spring (not shown) is installed in each of the first to fourth speed clutches C ₁ to _{C 4} . The first to fourth speed clutches C ₁ to _{C 4} are engaged when hydraulic pressure is introduced into each hydraulic servo 9, 14, 16, and 18, and are engaged when the hydraulic pressure is discharged. The engagement is released by the spring force of the return spring. The shift valves V ₁ to _{V 3} are connected to the first pilot oil passage 6 and the second pilot oil passage 7,
Throttle pressure Pt and governor pressure Pg act on both ends of the valve bodies (not shown) of each shift valve _V1 to _V3 , and the first
A switching operation is performed from the switching position to the second switching position.

The creep prevention device according to the present invention includes a hydraulic control device 19. This hydraulic control device 19 operates based on a throttle pressure Pt corresponding to the magnitude of an index representative of the output of the engine E, a rotation speed signal of the engine E, and a brake signal to control the first speed clutch.
The hydraulic pressure acting on the hydraulic servo 9 of _C1 is controlled from substantially zero to a predetermined value. The hydraulic control device 19 includes a spool valve 20 interposed between one communication oil passage 8 and the other communication oil passage 8', and a solenoid valve 21 that drives the spool valve 20. The spool 20 includes a spool valve body (hereinafter simply referred to as a valve body) 22 which is disposed slidably in the axial direction within a valve hole 21a of a valve casing valve 21, and a spool valve body (hereinafter simply referred to as a valve body) 22, which is disposed in a valve hole 21a of a valve casing valve 21, and a spool valve body (hereinafter simply referred to as a valve body) 22, which is disposed in a valve hole 21a of a valve casing valve 21. 1 Pilot hydraulic chamber (spring chamber)
23, a second pilot hydraulic chamber 24 facing the other end surface 22b of the valve body 22, and a first pilot hydraulic chamber 23.
The valve body 22 is arranged in the second pilot hydraulic chamber 2.
It is provided with a spring 25 that biases toward the 4 side.
The pressure receiving area of the valve body 22 facing the first pilot hydraulic chamber 23 is set to be larger than the pressure receiving area facing the second pilot hydraulic chamber 24. Further, an annular groove 26 is formed on the outer periphery of the valve body 22, and when the valve body 22 moves toward the second pilot hydraulic chamber 24, one communication oil passage 8 and the other communication oil passage 8' are connected to each other. The valve body 22 communicates with the first pilot hydraulic chamber 2.
When moving to the third side, the other communicating oil passage 8' is communicated with the oil drain port 27 of the valve casing 21. The annular groove 26 is connected to the first pilot via a small passage 28 provided on the one end surface 22a side of the valve body 22 and a first one-way valve 29 that allows hydraulic fluid to flow to the first pilot hydraulic chamber 23 side. It can communicate with the hydraulic chamber 23 and also communicates with the second pilot hydraulic chamber 24 via a second small diameter passage 30, a large diameter passage 31, and a communication passage 32 provided on the other end surface 22b side of the valve body 22. .

In addition, the spring force of the spring 25 is the same as that of the first gear clutch.
The pressure Pe (engagement pressure of the first gear clutch C ₁ ) is set to approximately correspond to the spring force of the return spring (not shown) installed in C ₁ , or the pressure P ₀ is set slightly lower than this. .

Furthermore, one communication oil passage 8 and the other communication oil passage 8'
A bypass oil passage 34 that bypasses the spool valve 20 of the hydraulic control device 19 is connected to the bypass oil passage 34, and the bypass oil passage 34 is connected to one connecting oil passage 8 side (manual valve Vm side), that is, to the hydraulic pump P side. A second one-way valve 35 is interposed to allow the flow of hydraulic oil.

The solenoid valve 21 includes a solenoid 36 and a valve body 38 made of an armature that opens and closes a port 37 that communicates between the first pilot hydraulic chamber 23 of the spool valve 20 and a first pilot pressure passage 40 to be described later.
and a spring 39 that urges the valve body 38 in the valve closing direction. In this embodiment, when the two conditions that the brake pedal of the vehicle is depressed and the rotational speed of the engine E is equal to or lower than a reference value are satisfied, the solenoid 36 is energized, which opens the valve body 38 and closes the port. 37 is opened, and the first pilot hydraulic chamber 23 and the first throttle pressure passage 40 are opened.
There is communication between the two. Further, when either one of the above two conditions is not satisfied, the solenoid 36 is demagnetized, thereby closing the valve body 38 and opening the port 3.
7 is closed, and the first pilot hydraulic chamber 23 and the first
and the throttle pressure passage 40.

The opening pressure of the solenoid valve 21 is set so as to maintain the pressure in the first pilot hydraulic chamber 23 at a predetermined pressure ΔP ₀ when the solenoid 36 is not energized. That is, by appropriately setting the spring force of the spring 39 and the diameter d of the port 37, when the pressure in the first pilot hydraulic chamber 23 exceeds the predetermined pressure △ _P0 , the valve opens at an opening corresponding to the excess. The body 38 opens the port 37 and maintains the pressure in the first pilot hydraulic chamber 23 at a predetermined pressure ΔP ₀ .

The input side of the first throttle pressure passage 40 is connected to a second throttle pressure passage 41 branching from the first pilot oil passage 6 of the throttle valve Vt via a delay valve 50, which will be described later. Third pilot pressure passage 4 branching from passage 6
2 and a third one-way valve 43. Further, the first throttle pressure passage 40 is connected to the first pilot hydraulic chamber 23 of the spool valve 20 by a branch passage 45 which branches from this and has a fourth one-way valve 44 interposed therein. 2
When the first solenoid 36 is energized or demagnetized, the throttle pressure Pt is introduced into the first pilot hydraulic chamber 23 through either the port 37 or the branch passage 45.

The operation of the brake pedal and the rotation speed of the engine E are detected, and the solenoid valve 2 is activated based on the detection signal.
The outputs of the brake detector 46 and the engine speed detector 47 for controlling the
and is input to the solenoid 36 via the transistor 49. The brake detector 46 is, for example, a stop lamp switch, and is configured to output a high-level signal when the brake pedal is depressed. The engine rotation speed detector 47 is
For example, it is configured to count the interval between ignition pulses of engine E and output a high-level signal when the engine speed is below a reference value.

The delay valve 50 includes a valve casing 51, a spool valve body (hereinafter simply referred to as a valve body) 52 that is slidably fitted in the valve hole 51a of the valve casing 51 in the axial direction, and The pilot hydraulic chamber 53 faces one end, and the valve body 52 is connected to the pilot hydraulic chamber 5.
A spring 54 biasing the valve body 5 toward the
An annular groove 55 is formed on the outer periphery of 2. The pilot oil pressure chamber 53 is connected to the second throttle pressure passage 41 via the fifth one-way valve 56, and is also connected to the third throttle pressure passage 42 branching from the first pilot oil passage 6 of the throttle valve Vt. The two apertures 57 communicate with each other. The valve body 52 receives the throttle pressure Pt acting on the pilot hydraulic chamber 53.
When the pressure is less than the reference pressure Ps set by the spring force of the spring 54, the spring force of the spring 54 deviates toward the pilot hydraulic chamber 53 side, and the first and second throttle pressure passages 40 pass through the annular groove 55. ,41
When a throttle pressure Pt higher than the reference pressure Ps acts on the pilot hydraulic chamber 53, it moves to the right in the figure against the spring force of the spring 54, and
The second throttle pressure passages 40 and 41 are cut off.

In addition, the second throttle pressure passage 41 has a switching valve that opens in the fully automatic shift range (D ₄ range) of the automatic transmission A's 4 forward gears and closes in other ranges in conjunction with the manual valve Vm. A valve 58 is interposed to prevent vehicle creep only when the shift lever is in the drive position.

Next, the operation of the bypass prevention device having the above configuration will be explained.

When the vehicle is running steadily, the outputs of the brake detector 46 and the engine speed detector 47 are at a low level, and the solenoid 36 of the solenoid valve 21 is demagnetized. On the other hand, the throttle pressure Pt corresponding to the amount of depression of the accelerator pedal (not shown) of the vehicle is the second,
When the throttle pressure Pt exceeds the reference pressure Ps, the valve body 52 of the delay valve 50 is deviated to the right in the figure, and the delay valve 50 is The valve is closed, and the first,
The second throttle pressure passages 40 and 41 are cut off. At this time, if the solenoid 36 of the solenoid valve 21 is demagnetized, the first
Pressure oil in the pilot hydraulic chamber 23 is maintained. On the other hand, a part of the line pressure Pl of the output oil passage 5 flows through the first small diameter passage 28, one-way valve 29, second small diameter passage 30, large diameter passage 31, and communication passage 32 of the valve body 22 of the spool valve 20. the first pilot hydraulic chamber 23 through each
and the second pilot hydraulic chamber 24 , and the valve body 22 is introduced into the second pilot hydraulic chamber 24 due to the difference in pressure receiving area between its both end faces and the spring force of the spring 25 .
The connecting oil passages 8 and 8' communicate with each other through the annular groove 26. As a result, the line pressure Pl is supplied to the hydraulic servo 9 of the first speed clutch _C1 ,
The first gear clutch _C1 is positively engaged.

Here, assume that the accelerator pedal is released and the brake pedal is depressed in order to stop the vehicle. The throttle pressure Pt decreases as the accelerator pedal is released. However, the hydraulic pressure higher than the reference pressure Ps acting on the pilot hydraulic chamber 53 of the delay valve 50 is caused by the second throttle 5.
7 to the third throttle pressure passage 42, the delay valve 50 remains closed for a while and then opens. The delay function of the delay valve 50 prevents a shock that occurs when the accelerator pedal is suddenly returned from a depressed state. Next, when the engine rotation speed becomes equal to or lower than the reference rotation speed, the output signal of the engine rotation speed detector 47 becomes high level. On the other hand, since the brake detector 46 has already output a high level signal due to the depression of the brake pedal, the solenoid 81 of the solenoid valve 21
is excited, and its valve body 38 opens the port 37.

At this time, the valve body 52 of the delay valve 50 has already returned to the pilot hydraulic chamber 53 side, and the first and second
The throttle pressure passages 40 and 41 are communicated with each other. Therefore, the pressure oil in the first pilot hydraulic chamber 23 of the spool valve 20 is transferred to the port 37 and the first and second pilot hydraulic chambers.
It escapes to the low pressure side through the throttle pressure passages 40 and 41, and the pressure in the first pilot hydraulic chamber 23 decreases. Therefore, the valve body 22 of the spool valve 20 is moved into the first pilot hydraulic chamber 24 by the hydraulic pressure acting on the second pilot hydraulic chamber 24.
The valve body 2 is deviated toward the pilot hydraulic chamber 23 side.
The communicating oil passages 8 and 8', which were communicated through the two annular grooves 26, are cut off, and the hydraulic servo 9 of the first speed clutch _C1 is isolated from the hydraulic power source. Here, the first
The hydraulic servo 9 of the speed clutch C ₁ has a communication oil passage 8,
Line pressure Pl supplied when 8' was in communication
remains, this hydraulic pressure acts on the second pilot hydraulic chamber 24 and compresses the spring 25,
Further, the valve body 22 is deviated toward the first pilot oil pressure chamber 23 to communicate the annular groove 26 with the oil drain port 27, and a part of the oil pressure is released to the oil drain port 27.
The internal pressure of the hydraulic servo 9 is adjusted to the set pressure of the spring 25, that is, the first speed clutch, by the pressure regulating action of the spool valve 20 in accordance with the mutual balancing force between the hydraulic pressure remaining in the hydraulic servo 9 and the spring force of the spring 25. C ₁
(solid line in FIG. 3), which is slightly lower than the engagement pressure Pe (broken line V in FIG. ₃ ). Therefore, the first speed clutch _C1 is disengaged, and the vehicle is prevented from creeping when the engine speed is below the reference speed and the brake pedal is depressed.

Next, when the brake pedal is released in order to start the vehicle, the output signal of the brake detector 46 becomes low level, the solenoid 81 of the solenoid valve 21 is demagnetized, and the valve body 38 is moved to the port 37 by the spring force of the spring 39. occlude. At this time, if the accelerator pedal is not depressed, the throttle pressure Pt is below the reference pressure Ps, so the delay valve 50 is open, and the hydraulic pressure in the first pilot hydraulic chamber 23 is transferred to the port 37, the first throttle Pressure passage 40, annular groove 5 of valve body 52 of delay valve 50
5. The pressure escapes to the low pressure side via the second throttle pressure passage 41 and the switching control valve 58, and the pressure in the first pilot hydraulic chamber 23 of the spool valve 20 is controlled to the predetermined pressure ΔP ₀ described above. As a result, spool valve 2
0 means that the spring force of the spring 25 is exactly the predetermined pressure △P ₀
The internal pressure of the hydraulic servo 9 of the first gear clutch _C1 becomes the set pressure.
It will be increased from P ₀ to (P ₀ +△P ₀ ) (solid line in Figure 3). Due to this increase in the predetermined pressure ΔP ₀ , the ineffective stroke when the hydraulic servo 9 of the first speed clutch C ₁ is engaged is completely eliminated. In this way, the invalid stroke can be removed and the vehicle can be reliably brought into a creep state.Moreover, since the pressure change from the set pressure P ₀ increases by a small amount of the predetermined pressure △P ₀ , the brake pedal The shock when the pedal is released is minimized.

Next, when the accelerator pedal is depressed, a throttle pressure Pt corresponding to the amount of depression is generated. When this pressure is lower than the reference pressure Ps, the delay valve 50 is opened, and the throttle pressure Pt is transferred to the second throttle pressure passage 41. , the first pilot hydraulic chamber 23 of the spool valve 20 via the delay valve 50, the first throttle pressure passage 40, the branch passage 45 and the one-way valve 44.
supplied to Therefore, the valve body 2 of the spool valve 20
2 gradually deviates toward the first pilot hydraulic chamber 24 as the throttle pressure Pt increases, and the annular groove 26 of the valve body 22 gradually communicates between the communication oil passages 8 and 8'. Therefore, the pressure in the hydraulic servo 9 of the first gear clutch _C1 increases at an inclination angle with respect to the passage of unit time determined by the area difference between both end surfaces of the valve body 22 of the spool valve 20 and the depression speed of the accelerator pedal. It rises along the line (solid line in Figure 3).

When the throttle pressure Pt exceeds the reference pressure Ps, the delay valve 50 closes and the first and second throttle pressure passages 4
As a result, the spool valve 2
The oil pressure in the first pilot oil pressure chamber 23 at 0 has no place to escape, and flows from the connecting oil passage 8 to the annular groove 26 of the valve body 22.
The hydraulic pressure supplied to the valve body 22 is applied to both end surfaces of the valve body 22 at equal pressure. Therefore, the valve body 22 of the spool valve 20
is completely deviated toward the second pilot hydraulic chamber 24 due to the difference in the pressure receiving areas of both end faces and the spring pressure of the spring 25, and is connected to the communication oil passage 8, via the annular groove 26.
Completely communicate between 8'. As a result, the internal pressure of the hydraulic servo 9 of the _first speed clutch C1 is
line pressure Pl (solid line in Figure 3),
The first speed clutch _C1 is reliably engaged and has the maximum transmission capacity.

By the way, the above-mentioned creep prevention device applies a preload force to the hydraulic servo 9 of the first speed clutch _C1 that is slightly lower than the spring pressure of the return spring of the first speed clutch _C1 when the vehicle is stopped and the engine E is in an idling state. P ₀ is stored, and when the next vehicle is started, the accelerator pedal is pressed to add a pressure of △P ₀ that compensates for the invalid stroke of the first gear clutch C ₁ to the preload force P ₀ . However, when the vehicle is stopped, the vehicle is prevented from creeping, and when the vehicle is started, the first speed clutch _C1 is engaged without delay to prevent an unpleasant shock when the vehicle is started. However, when switching the shift lever from the drive position to the neutral position or the reverse position, in the past, an escape path for the preload force P ₀ stored in the hydraulic servo 9 of the first gear clutch C ₁ is not secured. Since this preload force P ₀ acts as a residual pressure at the time of switching, the responsiveness at the time of switching was poor.

In the device of the present invention, the bypass oil passage 34 is connected to the other communication oil passage 8' connected to the hydraulic servo 9 of the first speed clutch _C1 and the line pressure Pl connected to the manual valve Vm connected to the shift lever. A one-way valve 35 that bypasses the hydraulic control device 19 and connects to one of the communication oil passages 8 passing through the bypass oil passage 34, and that allows hydraulic oil to flow toward the one communication oil passage 8 in the intermediate portion of the bypass oil passage 34. Therefore, when switching the shift lever from the drive position to the neutral position or the reverse position, the preload force P ₀ is immediately transferred from the bypass oil passage 34 to the manual valve via the communication oil passages 8, 8' and the output oil passage 5. The automatic transmission A
Switching from the drive position to the neutral position or the reverse position is performed with good responsiveness.

(Effects of the Invention) As described above, according to the present invention, the magnitude of the index representative of the output of the engine is It operates based on the corresponding throttle pressure, engine speed signal and brake signal,
A hydraulic control device that controls the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value, which prevents vehicle creep by controlling the hydraulic pressure to substantially zero, and further prevents creep of the vehicle when the engine is idling. In a creep prevention device for an automatic transmission for a vehicle, which shortens the time delay until the starting friction engagement element returns from a power cutoff state to a power transmission state by storing a predetermined preload force in a hydraulic servo. , a bypass oil passage that bypasses the hydraulic control device is interposed in the communication oil passage, and a bypass oil passage that allows hydraulic oil to flow from the starting frictional engagement element toward the hydraulic pressure source side. A directional valve is installed, and when the shift lever of the vehicle is switched from a drive position to a neutral position or a reverse position, the preload force stored in the hydraulic servo is released to the hydraulic pressure source side via the bypass oil passage. It is characterized in that it is made to be

Therefore, when the vehicle is stopped and the engine is in an idling state, the preload force stored in the starting friction engagement element in preparation for the next start is immediately transferred to the oil drain path on the hydraulic source side through the bypass passage. This allows the automatic transmission to switch from the drive position to the neutral position or the reverse position with good responsiveness even in cold weather when the hydraulic fluid has high viscosity.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and Fig. 1 is a configuration diagram of a drive system of a vehicle equipped with an automatic transmission with four forward speeds and one reverse speed to which the present invention is applied, and Fig. 2 is a diagram showing an embodiment of the present invention. FIG. 3 is a block diagram of the hydraulic control circuit of the automatic transmission, and FIG. 3 is a diagram showing the operating characteristics of the creep prevention device of the present invention. 19... Hydraulic control device, 20... Spool valve,
21...Solenoid valve, 34...Bypass oil path,
35...One-way valve, E...Engine, A...Automatic transmission, _C1 ...1st speed clutch (frictional engagement element for starting).

Claims (1)

[Scope of Claims] 1. Throttle pressure and engine rotational speed that are interposed in a communication oil passage that communicates the hydraulic pressure source and the hydraulic servo of the starting friction engagement element and that are representative of the engine output and that correspond to the size of the index. A hydraulic control device that operates based on a signal and a brake signal to control the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value, and prevents vehicle creep by controlling the hydraulic pressure to substantially zero. Furthermore, by storing a predetermined preload force in the hydraulic servo during engine idling, the time delay until the starting friction engagement element returns from a power cutoff state to a power transmission state is shortened. In the creep prevention device for an automatic transmission for a vehicle, the communicating oil passage is provided with a bypass oil passage that bypasses the hydraulic control device, and the oil pressure is supplied from the starting friction engagement element to the bypass oil passage. A one-way valve that allows hydraulic oil to flow to the source side is installed, and when the shift lever of the vehicle is switched from the drive position to the neutral position or the reverse position, the hydraulic oil is supplied to the hydraulic servo via the bypass oil path. A creep prevention device for an automatic transmission for a vehicle, characterized in that the stored preload force is released to the hydraulic pressure source side. 2. The hydraulic control device includes a spool valve and a solenoid valve that drives the spool valve, and when moving in one direction, the spool valve connects the hydraulic pressure source side and the hydraulic servo to move in the other direction. a valve body that communicates the hydraulic servo and the oil drain port during movement;
The solenoid valve is energized when the brake pedal of the vehicle is depressed and the engine speed is below a reference value, and is demagnetized at other times. a solenoid, and a valve body that communicates between the spring chamber of the spool valve and the throttle pressure passage when the solenoid is energized, and blocks the spring chamber and the throttle pressure passage when the solenoid is demagnetized. A creep prevention device for a variable transmission for a vehicle as set forth in claim 1, comprising: 3. The automatic transmission for a vehicle according to claim 1, wherein the index representing the output of the engine is a throttle pressure proportional to the amount of depression of the access pedal and a governor pressure proportional to the vehicle speed. Anti-creep device.