JPH0213187B2 - - 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).

In order for the anti-creep device to operate, it is necessary to detect that the engine is in an idle state, and for this purpose, in addition to the throttle valve or throttle pedal of the engine being in the idle position, the vehicle speed or engine rotational speed is also a criterion. It is necessary to detect that the value is below the value. In addition to this, in order to avoid even the slightest loss of ease when starting on a slope, it is desirable to detect whether or not the brake is operating, and to use this detection result as the operating condition for the creep prevention mechanism. As such a detection method, an electrical detection method is adopted so as not to impair the reliability of the existing brake side. Since this method requires electrical input, the method of recovering creep when the brake is released has to be an on-off operation, which has the disadvantage of causing a large shock when the brake is released and the vehicle starts moving. be. To solve this problem, it is effective to gradually increase the pressure by controlling the duty ratio of the solenoid valve when re-engaging the clutch after releasing the brake. (Japanese Patent Application No. 57-144142).

However, this device is very expensive because it uses a computer, and has problems such as pulses during duty control exciting minute vibrations.

Furthermore, as the engine throttle valve transitions from the idle position to the open position,
For example, the present applicant has proposed a creep prevention device in which the clutch is re-engaged by throttle pressure or the like (Japanese Patent Application No. 1983-60362).

(Problem to be Solved by the Invention) In this way, in a system that re-engages the clutch by receiving commands from two control systems, it is difficult to re-engage the clutch when the brake is released and the vehicle is started. There is no need to increase the transmission capacity of the clutch to its maximum value, and the throttle valve opening at that time is at the idle position. In other words, it is possible to prevent a shock when the brake is released and the vehicle starts moving. According to this idea, the re-engagement of the clutch when the brake pedal is released and the vehicle starts is extremely light, and even without the above-mentioned duty ratio control, the shock when the brake is released and the vehicle starts is greatly reduced. This will be improved.

The present invention has been made in view of the above circumstances, and is a starting device in which the hydraulic pressure of a hydraulic servo is controlled to engage and disengage based on three signals: a brake detection signal, a throttle pressure detection signal, and an engine output detection signal. By reducing the transmission capacity of the friction engagement element to substantially zero when the brake pedal is depressed when both the throttle pressure and engine speed are equivalent to idle, the fuel efficiency is reduced by preventing creep. Economic efficiency improves. Additionally, when the brake pedal is released when both the throttle pressure and the engine speed are equivalent to idling, the brake pedal should be re-engaged by increasing the pressure just enough to cause creep compared to the idling torque. Accordingly, an object of the present invention is to provide a creep prevention device for an automatic transmission for a vehicle, which can eliminate a shock when the brake pedal is released and the vehicle starts moving.

(Means for Solving the Problems) In order to achieve the above object, the present invention operates on a hydraulic servo of a starting friction engagement element that is connected to a hydraulic pressure source of a vehicle automatic transmission via a communication oil passage. A creep prevention device for an automatic transmission for a vehicle that is capable of preventing creep in a vehicle by controlling hydraulic pressure with a hydraulic control device based on a throttle pressure, an engine speed, and a brake signal. The device includes a spool valve interposed in the communication oil passage, and a solenoid valve that opens and closes the spool valve. When the signal is turned on, the spool valve is opened by the solenoid valve, thereby reducing the oil pressure to substantially zero to prevent the creep, and causing the engine rotation speed and the engine rotation speed to When the brake signal is turned off by releasing the depression of the brake pedal at a value equivalent to idling, the starting friction engagement element is activated by closing the spool valve with the solenoid valve. The hydraulic pressure can be controlled so that the transmission capacity of the engine is small enough to cause creep with respect to the torque during idling.

(Function) When the brake pedal is depressed when both the throttle pressure and engine speed are equivalent to idle, the oil pressure of the hydraulic servo of the starting friction engagement element becomes substantially zero, causing creep. By preventing this, fuel economy is improved. Also,
When the brake pedal is released when both the throttle pressure and engine speed are equivalent to idling, the hydraulic pressure of the hydraulic servo of the starting friction engagement element creeps with respect to the torque at idling. Since the pressure increases only by a small amount, there is no shock when you release the brake pedal and start moving.

(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 first controls 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 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 _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 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 20a interposed between one communication oil passage 8 and the other communication oil passage 8', and a solenoid valve 20b that drives the spool valve 20a. The spool valve 20a has a valve hole 21 in the valve casing 21.
a spool valve body (hereinafter simply referred to as a valve body) 22 disposed so as to be slidable in the axial direction within a;
A first pilot hydraulic chamber (spring chamber) 23 facing one end surface 22a, a second pilot hydraulic chamber 24 facing the other end surface 22b of the valve body 22, and It is provided with a spring 25 that urges the second pilot hydraulic chamber 24 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. In addition, valve body 2
An annular groove 26 is formed on the outer periphery of the annular groove 2.
6 communicates between one communication oil passage 8 and the other communication oil passage 8' when the valve body 22 moves to the second pilot hydraulic chamber 24 side, and the valve body 22 moves to the first pilot hydraulic chamber 23 side. When moving, the other connecting oil passage 8'
communicates with the oil drain port 27 of the valve casing 21. The annular groove 26 connects a small diameter passage 28 provided on the one end surface 22a side of the valve body 22 and the first pilot hydraulic chamber 23.
A first one-way valve 2 that allows hydraulic oil to flow to the side.
It can communicate with the first pilot hydraulic chamber 23 through It communicates with the hydraulic chamber 24.

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 Po
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 20a 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 20b includes a solenoid 36, a valve body 38 made of an armature that opens and closes a port 37 communicating with the first pilot hydraulic chamber 23 of the spool valve 20a, and a first throttle pressure passage 40, which will be described later. The valve is provided with a spring 39 that biases the valve 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 was opened and the first
The pilot hydraulic chamber 23 and the first throttle pressure passage 40 communicate with each other. Further, when either one of the two conditions is not satisfied, the solenoid 36
is demagnetized, whereby the valve body 38 closes, the port 37 is closed, and the first pilot hydraulic chamber 23 and the first throttle pressure passage 40 are cut off.

The opening pressure of the solenoid valve 20b is set so as to maintain the pressure in the first pilot hydraulic chamber 23 at a predetermined pressure ΔPo 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 ΔPo, the valve body 38 opens at an opening degree corresponding to the excess amount. opens the port 37 and maintains the pressure in the first pilot hydraulic chamber 23 at a predetermined pressure ΔPo.

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 branched from the first throttle pressure passage 40, and is connected to the first throttle pressure passage 45 of the spool valve 20a through a branch passage 45 in which a fourth one-way valve 44 is interposed.
Connected to the pilot hydraulic chamber 23, the throttle pressure Pt is introduced into the first pilot hydraulic chamber 23 through either the port 37 or the branch passage 45 when the solenoid 36 of the solenoid valve 20b is energized or demagnetized. I'm starting to do that.

Brake detector (brake detection means) that detects whether or not the brake pedal has been released
46 and an engine rotation speed detector (engine rotation speed detection means) 47 for detecting the rotation speed of the engine E, and each output signal of each of these detectors 46 and 47 is sent to an AND circuit 48 and a transistor 4.
9 to the solenoid 36 to control the solenoid valve 20b. Brake detector 46
For example, a stop lamp switch is used,
It is configured to output a high-level signal when the brake pedal is depressed. The engine speed detector 47 is configured to, for example, count the interval between ignition pulses of the engine E and output a high-level signal when the engine speed is below a reference value (idling state).

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 oil pressure in the pilot hydraulic chamber 53 is reduced to the throttle 57.
Since it flows out only through the valve, there is resistance to the valve opening operation of the valve body 52, so even after the throttle pressure Pt has been processed, the valve is kept in the closed state for a while.
A delay 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 normally, 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 20b is demagnetized. On the other hand, a throttle pressure Pt corresponding to the amount of depression of an accelerator pedal (not shown) of the vehicle is supplied to the second and third throttle pressure passages 41 and 42, but if this throttle pressure Pt exceeds the reference pressure Ps, the throttle pressure Pt is delayed. The valve body 52 of the valve 50 is deviated to the right in the figure, so that the delay valve 50 is closed, and the first and second throttle pressure passages 40 and 41 are cut off. At this time, if the solenoid 36 of the solenoid valve 20b is demagnetized, the spool valve 20
The pressure oil in the first pilot hydraulic chamber 23 of a is maintained. On the other hand, a part of the line pressure Pl of the output oil passage 5 is transferred to the first small diameter passage 28 of the valve body 22 of the spool valve 20a.
The oil is introduced into the first pilot hydraulic chamber 23 and the second pilot hydraulic chamber 24 through the one-way valve 29, the second small diameter passage 30, the large diameter passage 31, and the communication passage 32, respectively, and the valve body 22 receives pressure on both end surfaces thereof. Due to the difference in area and the spring force of the spring 25, the pilot hydraulic pressure chamber 24 is deviated toward the second pilot hydraulic chamber 24, and the communication oil passages 8 and 8' are communicated via the annular groove 26. As a result, the line pressure Pl is supplied to the hydraulic servo 9 of the first gear clutch _C1 , and the first gear clutch _C1 is reliably 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 transferred to the valve body 52.
Since resistance is given 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 speed becomes below the reference speed (idling state), the output signal of the engine speed detector 47 becomes high level. On the other hand, brake detector 4
Since solenoid valve 6 has already output a high level signal due to depression of the brake pedal, solenoid valve 2
The solenoid 81 of 0b is energized, and its valve body 3
8 opens 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 20a escapes to the low pressure side via the port 37 and the first and second throttle pressure passages 40, 41, and the pressure in the first pilot hydraulic chamber 23 decreases. decreases. For this reason, the valve body 22 of the spool valve 20a is biased toward the first pilot hydraulic chamber 23 by the hydraulic pressure acting on the second pilot hydraulic chamber 24, and is communicated with the first pilot hydraulic chamber 23 through the annular groove 26 of the valve body 22. The communication oil passages 8 and 8' are cut off, and the hydraulic servo 9 of the first speed clutch _C1 is isolated from the hydraulic power source. here,
Since the line pressure Pl that was supplied when the communication oil passages 8 and 8' were in communication remains in the hydraulic servo 9 of the first speed clutch _C1 , this oil pressure acts on the second pilot hydraulic chamber 24. to compress the spring 25, and then move the valve body 22 into the first pilot hydraulic chamber 23.
By deflecting it to the side, the annular groove 26 is communicated with the oil drain port 27, and a part of the hydraulic pressure is released to the oil drain port 27. Then, 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 20a according to the mutual balancing force between the hydraulic pressure remaining in the hydraulic servo 9 and the spring force of the spring 25. The engagement pressure (clutch pressure) Pe (broken line V in Figure 3) of C ₁ is maintained at a pressure Po that is slightly lower (3rd clutch pressure).
solid line in the figure). Therefore, the first speed clutch _C1 is disengaged, and the vehicle is prevented from creeping when the engine speed is below the reference speed (idling state) and the brake pedal is depressed.

Next, when the engine speed is below the reference speed (idling state) and the brake pedal is released in order to start the vehicle at time To in FIG. 3, the output signal of the brake detector 46 becomes low level, and the solenoid valve The solenoid 81 of 20b is demagnetized, and its valve body 38 closes the port 37 by the force of the spring 39. At this time, since the accelerator pedal is not depressed, the throttle pressure Pt is below the reference pressure Ps, and the delay valve 50
is opened, and the hydraulic pressure in the first pilot hydraulic chamber 23 is transferred to the port 37 and the first throttle pressure passage 4.
0, the pressure inside the first pilot hydraulic chamber 23 of the spool valve 20a is the same as that described above. It is controlled to a predetermined pressure ΔPo. As a result, the spool valve 20a becomes as strong as the spring force of the spring 25 corresponding to the predetermined pressure ΔPo, and the internal pressure of the hydraulic servo 9 of the first speed clutch _C1 changes from the set pressure Po to (Po
+ΔPo) (solid line in Figure 3). This predetermined pressure ΔPo is a small value that only causes creep with respect to the torque when the engine is idling, and the hydraulic servo 9 of the first speed clutch _C1 is The ineffective stroke when engaged is completely eliminated. In this way, the invalid stroke can be removed and the vehicle can be brought into a creep state without fail.Moreover, since the pressure change from the set pressure Po increases by a small amount of the predetermined pressure ΔPo, it is possible to reduce the pressure on the brake pedal. The shock when releasing and starting is minimized. The pressure Pe indicated by the broken line V in Fig. 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 occurs. Creep does not occur if the temperature is low.

Next, when the accelerator pedal is depressed at time _T1 in Fig. 3, the engine speed becomes equal to or higher than the reference rotation speed, and a throttle pressure Pt corresponding to the amount of depression is generated, and when this pressure is less than the reference pressure Ps, the engine is delayed. The valve 50 is open, and the throttle pressure Pt is applied to the second throttle pressure passage 41, the delay valve 50, the first throttle pressure passage 40, and the branch passage 4.
5 and a one-way valve 44 to the first pilot hydraulic chamber 23 of the spool valve 20a. Therefore, the valve body 22 of the spool valve 20a is controlled by the throttle pressure.
As Pt increases, it is gradually deviated toward the first pilot hydraulic chamber 24, and the annular groove 26 of the valve body 22 gradually communicates between the communicating oil passages 8, 8'. Therefore, the pressure of the hydraulic servo 9 of the first speed clutch _C1 increases at an inclination angle with respect to the passage of unit time determined by the area difference between the both end surfaces of the valve body 22 of the spool valve 20a and the depression speed of the accelerator pedal. It rises along the line (solid line in Figure 3).

Then, when the throttle pressure Pt exceeds the reference pressure Ps at time T ₂ in Fig. 3, the throttle pressure
By introducing Pt into the pilot hydraulic chamber 53 through both the one-way valve 56 and the throttle 57,
The valve body 52 closes without delay compared to the valve opening operation, the delay valve 50 closes, and the first and second throttle pressure passages 40 and 41 are cut off. As a result, the spool valve The oil pressure in the first pilot oil pressure chamber 23 has no place to escape, and the oil pressure flows from the connecting oil passage 8 to the valve body 22.
The hydraulic pressure supplied to the annular groove 26 of the valve body 22
Equal pressure is applied to both end faces of. Therefore, the valve body 22 of the spool valve is opened to the second pilot hydraulic chamber 2 due to the difference in the pressure receiving area between the two end faces and the spring pressure of the spring 25.
The connecting oil passages 8 and 8' are completely deviated to the 4 side, and the communication oil passages 8 and 8' are completely communicated through the annular groove 26. 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 Figure 3), and the first speed clutch _C1 is reliably engaged. It has 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 oil pressure acting on the hydraulic servo of the starting friction engagement element, which is connected to the oil pressure source of the automatic transmission for vehicles via the communication oil passage, is transferred to the throttle. In a creep prevention device for an automatic transmission for a vehicle, the creep prevention device for a vehicle automatic transmission is capable of preventing creep in a vehicle by controlling it with a hydraulic control device based on pressure, engine speed, and a brake signal. The engine includes a spool valve interposed in a communication oil passage and a solenoid valve that opens and closes the spool valve, and the brake signal is turned on when the brake pedal is depressed when the throttle pressure and engine speed are both equivalent to idle. By opening the spool valve with the solenoid valve, the oil pressure is reduced to substantially zero to prevent the creep, and the engine speed and the engine speed are both equivalent to idle. When the brake signal is turned off by releasing the depression of the brake pedal, the solenoid valve closes the spool valve, thereby increasing the transmission capacity of the starting friction engagement element. The present invention is characterized in that the hydraulic pressure can be controlled to a value that is small enough to cause creep with respect to torque during idling.

Therefore, with a simple configuration, it is possible to improve fuel economy when the throttle pressure and engine speed are equivalent to idling and the vehicle is stopped by depressing the brake pedal, and it is also possible to improve fuel economy when the vehicle is stopped by depressing the brake pedal. It is possible to prevent a shock when the vehicle is released and the vehicle starts moving.

[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, 20a...Spool valve, 2
0b... Solenoid valve, E... Engine, A...
Automatic transmission, P... Hydraulic power source, C ₁ ... First speed clutch (frictional engagement element for starting), 41, 42... Oil path, 46... Brake detector (brake detection means), 47... Engine speed detector (engine speed detection means).

Claims (1)

[Claims] 1 A hydraulic control device controls the hydraulic pressure acting on the hydraulic servo of the starting friction engagement element, which is connected to the hydraulic source of the vehicle automatic transmission via a communication oil passage, based on the throttle pressure, engine speed, and brake signal. In the creep prevention device for a vehicle automatic transmission, which is capable of preventing creep in a vehicle by controlling and a solenoid valve that is driven to open and close, and when the throttle pressure and engine speed are both equivalent to idle and the brake signal is turned on by depressing the brake pedal, the solenoid valve opens the spool valve. Particularly, the oil pressure is reduced to substantially zero to prevent the creep, and the brake pedal is released when the engine rotation speed and the engine rotation speed are both equivalent to idle, thereby reducing the brake pedal pressure. When the signal is turned off, by closing the spool valve using the solenoid valve, the transmission capacity of the starting frictional engagement element is reduced to a value that is small enough to cause creep with respect to the torque during idling. A creep prevention device for an automatic transmission for a vehicle, characterized in that it is configured to be able to control the oil pressure as follows.