JPH0125940B2 - - 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, a creep prevention device is conventionally known in which the transmission capacity of the starting friction engagement element (low speed clutch) is maintained at almost zero during idling operation.

It is known that such a creep prevention device also reduces vibrations during idling, and its effect is particularly remarkable in front-wheel drive vehicles (FF vehicles).

This type of anti-creep device smoothly resumes power transmission when starting, and especially when it is necessary to move the vehicle in a very narrow space, such as when parallel parking, it is proportional to the slight amount of throttle pedal operation. It is desirable that the clutch be in a half-engaged state, but on the other hand, once the clutch has been engaged in a half-engaged state, such as when starting when there is no car in front of the car, it is best to fully engage the clutch. In order to improve the durability of the clutch, it is necessary to prevent unnecessary slippage of the clutch.

In addition, for vehicles equipped with creep prevention devices,
Immediately after depressing the accelerator pedal, if you suddenly return the throttle pedal to the idle position, torque is applied to the entire engine and transmission, the mount rubber is strongly twisted, and this swing suddenly stops. to be removed,
The energy stored in the mount rubber is released all at once, resulting in an unpleasant shock. To avoid this, it is effective to provide a delay function that allows the creep state to continue for a short time even after the throttle pedal is released until the engine speed drops completely.

Therefore, the present applicant first controlled the engagement force of the clutch in proportion to the stroke at the initial stage when the stroke of the throttle pedal was less than a predetermined value,
A creep prevention device (Japanese Patent Application No. 178499/1983) that controls the engagement force of the clutch to its designed maximum value regardless of the stroke when the stroke exceeds a predetermined value;
We also proposed a creep prevention device (Japanese Patent Application No. 145808/1982) which has a delay function that continues the creep state for a short period of time until the engine speed drops to the idle speed even after the throttle pedal is released.

(Problem to be Solved by the Invention) However, in the case of the former creep prevention device, a switching valve for opening and closing the feedback oil passage is interposed in the feedback system of the hydraulic control device for creep prevention (creep prevention valve). Therefore, when the two valves, i.e., the creep prevention valve and the switching valve, are installed far apart from each other, two oil passages are required for each valve, which is a major design constraint. It was hot. In addition, in the case of the latter creep prevention device, if the delay function operates under any operating conditions of the system, for example, the shift lever may be moved to the neutral position (N range).
There is a problem in that it is not possible to eliminate the shift shock that occurs when shifting from the front position to the forward position, for example, the fourth speed position ( _D4 range).

The present invention has been made in view of the above circumstances, and it not only simplifies the oil passage but also has a delay function, and furthermore, the present invention quickly enters the creep prevention state without delaying the shifting of the shift lever. To provide a creep prevention device for an automatic transmission for a vehicle, which performs a delay operation only when the throttle pedal is depressed.

(Means for solving the problem) In order to achieve the above object, the present invention includes:
Based on the throttle pressure, engine rotation speed signal, and brake signal, which are interposed in a connecting oil path that connects the hydraulic source and the hydraulic servo of the starting friction engagement element, and which correspond to the magnitude of an index representative of the engine output. a hydraulic control device that operates to control the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value;
In the creep prevention device for a vehicle automatic transmission, which is capable of preventing creep in a vehicle by controlling the oil pressure to substantially zero, the creep prevention device is installed in a throttle pressure passage and is configured to control the throttle pressure using the throttle pressure as an operating pressure. A switching valve is provided that closes the throttle pressure passage when the pressure exceeds a set pressure, and a one-way valve is provided in the operating pressure introduction path of the switching valve, and a throttle is provided in the operating pressure outlet path. As a result, the valve opening operation is characterized by causing a delay in following the change in the throttle pressure compared to the valve closing operation.

(Function) Since a switching valve is provided between the connecting point of the communication oil path and the branch oil path and the engine output detection means, it is not necessary to install a hydraulic control device (creep prevention valve) on the surface of the transmission case. Even if this occurs, the switching valve can be installed in the control circuit within the transmission, eliminating the need to provide an extra oil passage and increasing the degree of freedom in design.

In addition, the switching valve has a one-sided throttle and performs a delay action only when the valve is opened _.
Normally, there is no throttle pressure when shifting to the range), so the switching valve is open, and the hydraulic control device immediately closes the connecting oil passage.
Since the starting frictional engagement element is not engaged, there is no shock.

(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 reverse 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 passage 3 having a throttle 60.
The excess hydraulic pressure of the regulator valve Vr is guided to the torque converter T to pressurize the inside thereof and prevent cavitation.
The oil pressure in the hydraulic oil passage 2, which is regulated to a predetermined pressure by the regulator valve Vr, becomes the line pressure Pl. An oil passage 4 branched from the hydraulic oil passage 2 is connected to a manual valve Vm 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. A throttle valve (engine output detection means) Vt and a governor valve Vg are connected to the hydraulic oil path 2, and the throttle valve Vt has a first throttle valve Pt proportional to the amount of depression of the accelerator pedal as an index representative of the output of the engine E. Output to pilot oil line 6. Governor valve Vg outputs governor pressure Pg proportional to vehicle speed to second pilot oil passage 7. manual valve
The output oil passage 5 of Vm is connected to the 1st-2nd speed shift valve V ₁ , and the communication oil passage 8 on one side (on the manual valve Vm side) branched from the output oil passage 5 is connected to a hydraulic control device and the other (manual valve Vm side), which will be described later. The first speed clutch C _{1 is}
is connected to the hydraulic servo 9.

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 V ₂ is connected to the hydraulic servo valve 14 of the 2nd speed clutch C ₂ via an oil path 13, and the 3rd-4th speed shift valve V ₃ is connected to the hydraulic pressure of the 3rd speed clutch C ₃ through an oil path 15. They are connected to a hydraulic servo 18 of the fourth speed clutch _C4 via a servo 16 and an oil passage 17, respectively.
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 valve bodies (not shown) of each shift valve _V1 to _V3 , and the first
A switching operation is performed from switching position 1 to a 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 valve 20 includes a spool valve body (hereinafter simply referred to as a valve body) 22 which is disposed slidably in the axial direction in a valve hole 21a of a valve casing 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 21, and a first end face 22a of which faces the spool valve body 22. 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 diameter passage 28 provided on the one end surface 22a side of the valve body 22 and a first one-way valve 29 that allows the flow of hydraulic oil 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. .

Note that the spring force of the spring 25 is the same as that of the first gear clutch.
Return spring installed in C ₁ (not shown)
The pressure Pe (first gear clutch C ₁
engagement pressure) or a slightly lower pressure P ₀
is set to .

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 throttle 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 ΔP ₀ , the valve body opens at an opening corresponding to the excess. 38 is port 3
7 to maintain 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 throttle 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.

A brake detector 46 that detects whether the depression of the brake pedal is released and an engine rotation speed detector 47 that detects the rotation speed of the engine E are provided, and each output signal of each of these detectors 46 and 47 is provided. However, the AND circuit 48 and the transistor 49
The signal is inputted to the solenoid 36 via the solenoid valve 21 to control the solenoid valve 21. 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 speed detector 47 is configured to count, for example, the interval between ignition pulses of the engine E, and output a high-level signal when the engine speed is below a reference value.

The delay valve 50 includes a switching valve 51 and a single-effect throttle 52 attached thereto. The switching valve 51 includes a valve casing 51a, a spool valve body (hereinafter simply referred to as a valve body) 51b fitted in a valve hole of the valve casing 51a so as to be slidable in the axial direction, and a part of the valve body 51b. A pilot hydraulic chamber 53 facing the end face,
The valve body 51 includes a spring 54 that urges the valve body 51b toward the pilot hydraulic chamber 53, and an annular groove 55 is formed in the outer periphery of the valve body 51. Pilot hydraulic chamber 5
3 is connected to the second throttle pressure passage 41 via the fifth one-way valve 56, and the throttle valve
It is communicated via a second throttle 57 with a third throttle pressure passage 42 branching from the first pilot oil passage 6 of Vt. The valve body 52 is the pilot hydraulic chamber 5
The throttle pressure Pt acting on the spring 54
When the pressure is lower than the standard pressure Ps set by the spring force of the spring 54, the pilot hydraulic chamber 5 is
3 side, the valve becomes open, and the first and second throttle pressure passages 40 and 41 are communicated through the annular groove 55, and a throttle pressure Pt higher than the reference pressure Ps acts on the pilot hydraulic chamber 53. Toki Spring 5
The valve moves to the right in the figure against the spring force of 4 and becomes closed, and the first and second throttle pressure passages 40, 4
1.

The single-effect throttle 52 is composed of a second throttle 57 and a fifth one-way valve 56, and the single-effect throttle 52 allows the switching valve 51 to exhibit the above-mentioned index when it is open compared to when it is closed. There is now a delay in following changes in (fluid pressure). That is, when the throttle pressure Pt exceeds the reference pressure Ps, the throttle pressure Pt is introduced into the pilot hydraulic chamber 53 via both the one-way valve 56 and the throttle 57, so that the valve body 52 is closed without delay. becomes. On the other hand, when the throttle pressure Pt is less than the reference value Ps, the hydraulic pressure in the pilot hydraulic chamber 53 flows out only through the throttle 57, which creates resistance to the opening operation of the valve body 52, so that the throttle pressure Pt Even after processing is completed, the valve is kept closed for a while, and a delayed operation is performed. The one-way valve 56 and the throttle 57 are integrated into the switching valve 51.

The switching control valve 58 installed in the second throttle pressure passage 41 is opened only in the 4th speed _D4 range of the automatic transmission A in conjunction with the manual valve Vm, and is closed in other ranges. By doing so, the vehicle is prevented from creeping only in the fourth gear range of the shift lever.

Next, the operation of the creep prevention device having the above structure 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 surfaces 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 acting on the pilot hydraulic chamber 53 of the delay valve 50 is discharged to the third throttle pressure passage 42 only through the second throttle 57 and is discharged to the valve body 52.
Since resistance is provided to the valve opening operation of the delay valve 50
The valve remains closed for a while and then opens. The delay function of the delay valve 50 during the valve opening operation 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.
Then, due to the pressure regulating action of the spool valve 20 according to the mutual balancing force between the hydraulic pressure remaining in the hydraulic servo 9 and the spring force of the spalling 25, the internal pressure of the hydraulic servo 9 is adjusted to the set pressure of the spring 25, that is, the first speed clutch. C ₁
The engagement pressure (clutch pressure) Pe (broken line V in FIG. 3) is maintained at a pressure P ₀ (solid line in FIG. 3) that is slightly lower than that of the clutch 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, since the accelerator pedal is not depressed, the throttle pressure Pt is below the reference pressure Ps, and the delay valve 5
0 is open, and the first pilot hydraulic chamber 23
The oil pressure in
The pressure inside the first pilot hydraulic chamber 23 of the spool valve 20 is controlled to the predetermined pressure ΔP ₀ described above. As a result, the spool valve 20 becomes just as the spring force of the spring 25 becomes stronger by an amount corresponding to the predetermined pressure ΔP ₀ , and the first speed clutch
The internal pressure of the hydraulic servo 9 of _C1 changes from the set pressure P ₀ to (P ₀ +
ΔP ₀ ) (dotted chain line in FIG. 3). This predetermined pressure ΔP ₀ is a small value that only causes creep with respect to the torque when the engine is idling, and the increase in the predetermined pressure ΔP ₀ of this small value increases the oil pressure of the first gear clutch C ₁ . Servo 9
The ineffective stroke when 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 _P0 increases by a small amount of the predetermined pressure _ΔP0 , the brake pedal The shock when the pedal is released is minimized. The pressure Pe indicated by the broken line V in Figure 3
indicates the engagement pressure at which the return spring of the piston of the hydraulic servo 9 of the first speed clutch _C1 is balanced with the internal pressure, and if the internal pressure is higher than this pressure Pe, creep will occur, and if it is lower, no creep will occur.

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 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 throttle pressure Pt is introduced into the pilot hydraulic chamber 53 through both the one-way valve 56 and the throttle 57, so that there is no delay compared to the valve opening operation. The valve body 52 closes, the delay valve 50 closes, and the first and second throttle pressure passages 40 and 41 are cut off. As a result, the oil pressure in the first pilot hydraulic chamber 23 of the spool valve 20 is reduced. There is no place to escape, and the hydraulic pressure supplied from the connecting oil passage 8 to the annular groove 26 of 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 pressure receiving areas between the two end faces and the spring pressure of the spring 25, and is connected to the communication oil passage through the annular groove 26. 8 and 8' are completely communicated. As a result, the internal pressure of the hydraulic servo 9 of _the first speed clutch C1 is increased to the line pressure Pl of one of the communication oil passages 8 (solid line in Fig. 3), and the first speed clutch _C1
are securely engaged and have the maximum transmission capacity.

Further, since the delay valve 50 performs a delay action only when the valve is opened, the
Since the throttle pressure Pt is normally zero when shifting to the speed _D4 range, the delay valve 50 is open, and therefore the hydraulic control device 19 immediately switches between the first speed clutch _C1 and the hydraulic source. Connecting oil road 8 between
8' to prevent engagement of clutch _C1 , thereby preventing shift shock.

(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,
An automatic transmission for a vehicle, which is a hydraulic control device that controls the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value, and is capable of preventing vehicle creep by controlling the hydraulic pressure to substantially zero. In the creep prevention device, a switching valve is provided in the throttle pressure passage and closes to close the throttle pressure passage when the throttle pressure exceeds a set pressure using the throttle pressure as the operating pressure, and the switching valve By interposing a one-way valve in the operating pressure introduction path of the valve and a throttle in the operating pressure output path, the valve opening operation has a delay in following the change in the throttle pressure compared to the valve closing operation. This feature is characterized in that it allows the user to

Therefore, there is no need to provide an extra oil passage, and the degree of freedom in design can be greatly increased, reducing costs and improving ease of assembly.

Further, the switching valve is provided with a single-effect throttle that causes a delay in following changes in the fluid pressure when the valve is opened compared to when the valve is closed, so that it has a delay function, and the switching valve has a delay function. The system quickly transitions to the creep prevention state without performing a delay operation, and the delay operation is performed only when the accelerator pedal is depressed, thereby reducing fluctuations in engine rotation when the accelerator pedal is suddenly released. In addition, it is possible to prevent a shock caused by the shift lever from the neutral position to the forward position.

[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. 8, 8'...Connection oil path, 9...Hydraulic servo, 1
9...Hydraulic control device, E...Engine, A...Automatic transmission, P...Hydraulic power source, _C1 ...1st speed clutch (friction engagement element for starting), 41, 42...Oil path,
43... Throttle, 51... Switching valve, 52... Single-effect throttle, 57... Second throttle.

Claims (1)

[Claims] 1 Throttle pressure, engine rotation speed signal, and brake signal that are interposed in a connecting oil path that connects the hydraulic source and the hydraulic servo of the starting friction engagement element, and that correspond to the magnitude of an index representative of the engine output. a hydraulic control device that operates based on the hydraulic pressure and controls the hydraulic pressure acting on the hydraulic servo from substantially zero to a predetermined value, and is capable of preventing vehicle creep by controlling the hydraulic pressure to substantially zero. In a creep prevention device for an automatic transmission for a vehicle, the switch is installed in a throttle pressure passage and closes the throttle pressure passage when the throttle pressure exceeds a set pressure using the throttle pressure as an operating pressure. By providing a one-way valve in the operating pressure introduction path and a throttle in the operating pressure output path of the switching valve, the valve opening operation is more sensitive to the change in the throttle pressure than the valve closing operation. A creep prevention device for an automatic transmission for a vehicle, characterized in that it causes a follow-up delay.