JPH07174216A - Oil pressure control device for automatic transmission - Google Patents

Abstract

PURPOSE:To prevent an engine stall due to the unbalance of oil at the time of sudden braking. CONSTITUTION:In the oil pressure control device of an automatic transmission provided with an automatic transmission (b) having a torque converter (a) capable of locking-up, a line pressure actuator (c) for forming line pressure, and a line pressure controlling means (e) for controlling the operation of the line pressure actuator (c) in order to form line pressure according to input from a travel condition detecting means (d), an exposure condition detecting means (f) is provided which detects a condition wherein the inlet port of an oil strainer on the suction side of an oil pump is exposed from an oil surface. The line pressure controlling means (e) is made so as to be exposure-time-controlled, wherein line pressure is increased, during detecting a condition where the inlet port is exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for controlling the line pressure of an automatic transmission.

[0002]

2. Description of the Related Art In an automatic transmission, oil in an oil pan is sucked from an inlet of an oil strainer to generate hydraulic pressure by an oil pump, and the oil is supplied to each part in the automatic transmission.

By the way, when the oil in the oil pan is biased and the suction port of the oil strainer is exposed above the oil surface to suck air during sudden braking, the oil pump cannot discharge the required hydraulic pressure. . Therefore, there is known a structure in which a baffle plate is provided in an oil pan in order to prevent the deviation of the oil (see Japanese Utility Model Laid-Open No. 1-160110).

[0004]

However, in the prior art of providing the above-mentioned baffle plate, in order to completely prevent the deviation of the oil, the baffle plate completely covers the gap between the valve body and the inner wall of the oil pan. Although it has to be formed in a shape, it is impossible in reality to have such a structure, so that it was not possible to completely prevent the oil strainer from being exposed on the oil surface.

Therefore, when the oil is deviated when the vehicle is suddenly braked, the oil strainer may eventually be exposed on the oil surface, in which case the line pressure decreases. By the way, at the time of braking, if the torque converter is in the lockup state immediately before that, the release pressure is supplied to the lockup piston to release the lockup state.At this time, as described above, the suction of the oil strainer When the mouth is exposed to the air and the line pressure drops, the release pressure becomes insufficient and becomes lower than the apply pressure for engaging the lockup piston, and the lockup state cannot be released. There was a problem that an engine stall might occur.

FIG. 12 is a line for forming acceleration in the longitudinal direction of the vehicle body (hereinafter referred to as longitudinal G), release pressure P _R , apply pressure P _A , engine speed Ne, and line pressure when sudden braking is performed from the accelerated state. In the time chart showing the change of the duty ratio Du of the signal for controlling the pressure solenoid,
When the accelerator is opened at the time of a and acceleration is started, and then the sudden braking is performed at the time of 0b, the release pressure P _R becomes lower than the apply pressure P _A in the region indicated by 0c in the figure, and the engine speed It can be seen that the fall of Ne is large (shown by 0d). By the way, in the figure, the duty ratio Du shows the ratio of the OFF time of the output to the line pressure solenoid, and the higher this ratio, the higher the line pressure.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to prevent engine stall due to deviation of oil during sudden braking.

[0008]

In order to achieve the above-mentioned object, the present invention enables the input element and the output element to be directly connected by the lock-up means as shown in the claim correspondence diagram of FIG. An automatic transmission b having a simple torque converter a, a line pressure actuator c for adjusting the operating hydraulic pressure discharged from the oil pump of the automatic transmission b to form a line pressure, and an input from the running state detection means d. In a hydraulic control device for an automatic transmission, which includes a line pressure control means (e) for controlling the operation of a line pressure actuator (c) so as to form a line pressure according to a running state, the oil strainer on the suction side of the oil pump. An exposure state detecting means f for detecting a state in which the suction port is exposed from the oil surface is provided, and the line pressure control means e is used to detect the state in which the suction port is exposed. While out, and configured to perform exposure time control to increase the line pressure.

The state in which the suction port of the oil strainer detected by the exposed state detecting means f is exposed from the oil surface is not limited to the state in which the suction port is actually exposed, but also the running state in which the suction port is likely to be exposed. It includes the operating state,
For example, the exposure state detecting means f includes a braking detecting means for detecting that a braking operation has been performed, and an output shaft rotational speed detecting means for detecting an output shaft rotational speed of the automatic transmission, and outputs during the braking operation. A configuration may be adopted in which it is determined that the vehicle is in a traveling state in which the suction port is exposed when the shaft rotation speed is reduced to less than a predetermined rotation speed. Alternatively, the exposed state detection means f includes a pressure sensor that detects the suction hydraulic pressure of the suction port of the oil strainer, and the detection hydraulic pressure of the pressure sensor has dropped below a set value, so that the suction port is actually It may be configured to determine that it is in an exposed state. Alternatively, the exposure state detecting means f includes a vehicle speed detecting means for detecting a vehicle speed, calculates a deceleration of the vehicle from the vehicle speed, and when the deceleration is larger than a set value, a running state in which the suction port is exposed. It may be configured to determine that

[0010]

When the oil in the oil pan is offset due to a sudden deceleration by performing a braking operation and the suction port of the oil strainer is exposed above the oil surface, the exposed state detecting means f
Detects the state, and thereby the line pressure control means e controls the operation of the line pressure actuator c so as to increase the line pressure.

Therefore, even if the suction port is exposed and the discharge pressure of the oil pump is lowered when the release pressure is supplied to the lock-up means in order to release the lock-up of the torque converter a in response to the braking operation, By the above-described control for increasing the line pressure, the line pressure does not decrease as much as the decrease in the discharge pressure of the oil pump, and the release pressure can be secured and the lockup of the torque converter can be released.

In the apparatus according to the second aspect of the present invention, the exposure state detecting means f, when the braking operation is detected by the braking detecting means, the output shaft rotational speed detected by the output shaft rotational speed detecting means is less than the predetermined rotational speed. It is determined that the vehicle is in a running state where the suction port of the oil strainer is exposed and the engine stalls due to the decrease.

Further, in the apparatus according to the third aspect, the exposure state detection means f actually causes the suction port of the oil strainer to actually operate when the detection hydraulic pressure of the pressure sensor for detecting the suction hydraulic pressure of the oil strainer falls below a set value. It is determined that the suction hydraulic pressure is lowered by being exposed on the oil surface.

Further, in the apparatus according to the fourth aspect, the exposure state detecting means f calculates the deceleration from the vehicle speed detected by the vehicle speed detecting means, and when the deceleration is larger than the set value, suction of the oil strainer. It is determined that the vehicle is in a running state (brake state) where the mouth is exposed.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is an overall view showing a shift control device to which the hydraulic control device for an automatic transmission according to the first embodiment of the present invention is applied. In the figure, 1 is an A / T control unit for controlling the operation of the automatic transmission AT. The A / T control unit 1 includes an idle switch 2, a full throttle switch 3, a throttle sensor 4, an engine speed sensor 5 The inhibitor switch 6, the temperature sensor 7, the vehicle speed sensor 8 and the brake switch 9 are connected, and signals are exchanged with the ECCS control unit 10 that controls the drive of the engine E. The A / T control unit 1 shifts according to a preset shift schedule (see FIG. 3) according to vehicle speed and throttle opening based on inputs from the sensors 2 to 9 and the ECCS control unit 10. The drive of the solenoids A and B, the overrun clutch solenoid 11, the lockup solenoid 12, and the line pressure solenoid 13 is controlled to engage or release a friction engagement element such as a clutch or a brake (not shown) in the automatic transmission AT to move forward. 4th speed (4th speed is overdrive) / reverse 1st speed is controlled. The vehicle speed sensor 8 is actually the automatic transmission A.
The output shaft rotation speed N of T is detected, and the output shaft rotation speed N is converted into the vehicle speed in the A / T control unit 1.

As shown in FIG. 4, the automatic transmission AT is provided with a control valve 22 at the bottom of a transmission case 21 and an oil pan 23 covering the control valve 22. A suction port 24 a of the oil strainer 24 is opened inside the oil pan 23. 2 in the figure
5 is the oil level.

Further, the automatic transmission AT is provided with a torque converter 31 as shown in FIG. 5, and the torque converter 31 has a lockup for directly connecting the engine E side and the automatic transmission AT side. A piston 32 is provided. The lock-up piston 32 is switched between a lock-up state and a lock-up released state by a hydraulic pressure difference between the first chamber 32a and the second chamber 32b defined by the lock-up piston 32, that is, the first
The line pressure P _L is supplied to and discharged from the chamber 32a via the torque converter relief valve 33, while the second chamber 32b is discharged.
Through the torque converter relief valve 33 and the lockup control valve 34.
_L is supplied and discharged, and a hydraulic pressure difference is generated between the chambers 32a and 32b based on the operation of the lockup control valve 34. The figure shows the lockup piston 32.
Shows the locked-up state in which is fastened.

The A / T control unit 1 performs shift control based on the shift schedule shown in FIG. 3 by the main routine, but controls the line pressure P _{L in} the subroutine. That is, the line pressure P _L
Is controlled by controlling the duty ratio of the line pressure solenoid 13. The duty ratio Du is made proportional to the throttle pressure as shown in FIG.
In the case of the present embodiment, a signal indicating the throttle opening obtained from the throttle sensor 4 is used as the throttle pressure. The duty ratio Du indicates the proportion of OFF time, and the higher the proportion of OFF time (= duty ratio), the higher the line pressure.

Further, the A / T control unit 1 performs a line pressure control during braking (corresponding to the exposure time control in the claims) in addition to the above-described normal line pressure control. This control is shown in FIG. The flowchart will be described.

First, in step S1, a signal is read from the brake switch 9, and then in step S2,
It is determined whether or not the brake operation is performed. If YES, the process proceeds to step S3, and if NO, the process returns to step S1.

In step S3, the output shaft speed N is read from the signal obtained from the vehicle speed sensor 8 and the throttle opening θ is obtained from the signal obtained from the throttle sensor 4.
Is read, and thereafter, in step S4, the throttle opening θ is set to 0 and the output shaft speed N is set to a low set value N _0.
(This set value N ₀ is, for example, 500 rpm, which indicates immediately before the vehicle is stopped.) It is determined whether or not the value has decreased below, and if YES, the process proceeds to step S5, and if NO, the process returns to step S1.

In step S5, the line pressure solenoid 1
The duty ratio Du of the control signal output to 3 is set to a predetermined high duty ratio HDu (for example, about 80%). As a result, the line pressure P _L becomes the set pressure P close to the maximum pressure.
Rise to _Hi .

In step S6, the vehicle speed V detected by the vehicle speed sensor 8 is read, and then in step S7,
It is determined whether or not the vehicle speed V has dropped to ₀ km / h (V ₀ ), the process proceeds to step S8 if YES, and step S5 if NO.
Return to.

In step S8, time measurement is started,
In step S9, it is determined whether or not the measurement time T has reached the set time T ₀ (for example, about 5 seconds), the process proceeds to step 10 if YES, and step 9 is repeated if NO.

In step S10, the process for returning to the control of the duty ratio Du by the above-mentioned normal line pressure control is performed, and the one flow of the line pressure control during braking is completed.

Next, the operation of the embodiment will be described with reference to the time chart of FIG. In the figure, t1 indicates a section in which the braking operation is performed. At the start time t2 of this section, the throttle opening θ becomes 0 and the brake switch 9 becomes ON in response to the braking operation of releasing the foot from the accelerator and stepping on the brake pedal. Then, by the normal line pressure control, the line pressure P _L is reduced in response to the throttle opening becoming 0.

After that, when the output shaft rotational speed N is reduced to the set rotational speed N ₀ by the braking operation (at time t3 in the figure), the line pressure control during braking is started, the duty ratio is increased to HDu, and the line pressure P is increased. _L is increased to the set pressure P _Hi (steps S1 → S2 → S3 → S4 → S5).

Then, when the vehicle speed V becomes 0 (at time t4 in the figure) and the set time T ₀ elapses (at time t5 in the figure), the above line pressure P _L is set to the set pressure P.
End the control to raise to _Hi and return to normal line pressure control. In this example, at this time point t5, the throttle opening θ remains 0, so the line pressure P _L is controlled to a low pressure.

As described above, when the output shaft speed N is reduced during braking, the line pressure P _L is controlled to be increased. Therefore, if the sudden braking causes the oil in the oil pan 23 to shift to one side, the oil strainer is displaced. Even if the suction port 24a of 24 is exposed from the oil surface 25 and the discharge pressure of the oil pump decreases,
By performing control to increase the line pressure P _L to the set pressure P _Hi , the line pressure P _L rises to a certain degree (the discharge pressure of the oil pump decreases, so the line pressure P _L does not rise to the set pressure P _Hi ). This ensures the required release pressure P _R.

FIG. 9 shows the results of an experiment in which hydraulic pressure control is performed by the device of this embodiment. In the same way as the experiment of the conventional example of FIG. 12, a case where sudden braking is performed immediately after acceleration in the section t10 is shown. At this time, the suction port 24 of the oil strainer 24
It is assumed that a is exposed on the oil surface 25. Then, even if the suction port 24a may be exposed on the oil surface 25 as a result of performing the control for increasing the duty ratio Du at the time point t11 in the figure by the braking line pressure control, as compared with the related art. As a result, the release pressure P _R is prevented from decreasing, and the release pressure P _R never drops below the apply pressure P _A. Therefore, the lockup of the torque converter is released, the drop in the engine speed Ne at the time of t12 becomes small, and the risk of engine stall disappears.

Next, the second embodiment will be described.

As shown in FIG. 10, this second embodiment apparatus is an example in which the pressure sensor 14 is provided in the vicinity of the suction port 24a of the oil strainer 24 and is connected to the A / T control unit 1. A temperature sensor 7 is provided on the lower surface of the control valve 22 as illustrated.

FIG. 11 shows the control flow of the line pressure control during braking of the second embodiment device. In step S11,
From the pressure sensor 14 to the suction port 24 of the oil strainer 24
The hydraulic pressure P _{OI in} the vicinity of “a” is read in, and then step S12
Then, it is determined whether or not the oil pressure P _OI is less than a predetermined pressure P ₀ close to the atmospheric pressure, and if YES, the process proceeds to step S13 to perform control to increase the duty ratio Du to the set value HDu, and N
If O, the process returns to step S11.

Therefore, when the oil is deviated in the oil pan 23 and the suction port 24a is exposed on the oil surface 25 (in this case, it is not limited during braking), the line pressure P _L is controlled to increase, and the oil pressure is increased. A decrease in the line pressure P _L due to a decrease in pump discharge pressure is suppressed. Therefore, at the time of braking, similarly to the first embodiment, even if the suction port 24a is exposed on the oil surface 25, control is performed to increase the line pressure P _L ,
By preventing the release pressure P _R from lowering than the apply pressure P _{A, the} lockup of the torque converter can be released and the engine stall can be prevented.

Although the embodiment has been described above, the specific structure is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the present invention.

For example, as a control condition for increasing the line pressure P _L , step S4 (FIG. 7) of the control flow of the first embodiment is used.
Instead of the above), the deceleration of the vehicle is calculated by the signal obtained from the vehicle speed sensor 8 and it is determined whether or not this deceleration exceeds a set value of 9.8 m / S ² or less. Good. That is, the exposure of the suction port 24a is determined by determining whether or not the deceleration that causes the deviation of the oil such that the suction port 24a is exposed on the oil surface 25 in the oil pan 23 has occurred. is there.

Similarly, as a control condition for increasing the line pressure P _L , step S12 of the control flow of the second embodiment is performed.
Instead of (see FIG. 11), the oil temperature detected by the temperature sensor 7 is
For example, it may be determined whether or not the temperature is below a set value of 80 ° C. or lower. That is, when the oil is biased so that the suction port 24a is exposed on the oil surface 25 in the oil pan 23, the oil surface 25 causes the temperature sensor 7 to move.
When the oil temperature is not detected and the detected temperature becomes low, the deviation of the oil (exposure of the suction port 24a) is determined.

Further, the line pressure increase control may be performed by combining the control conditions described above and the same control conditions in the first and second embodiments.

Further, in the first embodiment, when the control condition is satisfied, the duty ratio Du of the signal output to the line pressure solenoid 13 is immediately increased and the line pressure P _L is turned ON / O.
Although the FF is increased, the duty ratio Du may be controlled to increase the line pressure P _L with an inclination as shown by the chain double-dashed line in FIG. 7.

Further, in parallel with performing the above-mentioned line pressure control, the engagement pressure of a friction engagement element (for example, a forward clutch) to be engaged during forward movement is released to cause slippage in this portion, or the engine. The rotation speed may be automatically increased to increase the discharge pressure of the oil pump.

[0041]

As described above, in the present invention, the exposure state detecting means for detecting the state in which the suction port of the oil strainer on the suction side of the oil pump is exposed from the oil surface is provided,
Since the line pressure control means is configured to perform the exposure time control for increasing the line pressure while the exposure state detection means detects the state where the suction port is exposed, the oil in the oil pan is deviated to one side during braking. Even if the suction port of the strainer is exposed on the oil surface and the discharge pressure of the oil pump drops, the line pressure control means controls the operation of the line pressure actuator so as to increase the line pressure. It does not decrease as much as the discharge pressure of the oil pump. Therefore, the release pressure supplied to the lock-up means for releasing the lock-up of the torque converter in response to the braking operation is kept higher than the apply pressure, and the release pressure is reduced so that the lock-up state cannot be released. The effect of preventing engine stall due to is obtained.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a hydraulic control device for an automatic transmission according to the present invention.

FIG. 2 is an overall view showing a hydraulic control device for an automatic transmission according to a first embodiment of the present invention.

FIG. 3 is a shift schedule of the first embodiment device.

FIG. 4 is a cross-sectional view showing the main parts of the first embodiment device.

FIG. 5 is a configuration explanatory view showing a main part of the first embodiment device.

FIG. 6 is a line pressure characteristic diagram when performing normal line pressure control of the first embodiment device.

FIG. 7 is a flowchart showing a braking line pressure control of the first embodiment device.

FIG. 8 is a time chart showing an operation example of the first embodiment device.

FIG. 9 is a time chart showing a braking experiment result of the first embodiment device.

FIG. 10 is a sectional view showing a main part of a hydraulic control device for an automatic transmission according to a second embodiment.

FIG. 11 is a flowchart showing a braking line pressure control of the second embodiment device.

FIG. 12 is a time chart showing a result of a braking test according to a conventional technique.

[Explanation of symbols]

 a torque converter b automatic transmission c line pressure actuator d running state detection means e line pressure control means f exposure state detection means

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area F16H 59:68

Claims (4)

[Claims] 1. An automatic transmission having a torque converter capable of directly connecting an input element and an output element by a lockup means, and adjusting working hydraulic pressure discharged from an oil pump of the automatic transmission. Automatic transmission including a line pressure actuator that forms a line pressure, and a line pressure control unit that controls the operation of the line pressure actuator to form a line pressure according to a running state based on an input from the running state detection unit In the hydraulic control device, the exposure state detecting means for detecting a state in which the suction port of the oil strainer on the suction side of the oil pump is exposed from the oil surface is provided, and the line pressure control means includes the exposure state detecting means. A hydraulic control device for an automatic transmission, characterized in that it is configured to perform an exposure control for increasing the line pressure while detecting a state in which the vehicle is exposed. 2. The exposure operation detecting means includes a braking detection means for detecting that a braking operation has been performed, and an output shaft rotation speed detecting means for detecting an output shaft rotation speed of the automatic transmission. The configuration is such that it is determined that the suction port is in a state of being exposed when the output shaft rotation speed is lowered below a predetermined rotation speed.
A hydraulic control device for the automatic transmission described. 3. The exposed state detecting means includes a pressure sensor for detecting a suction hydraulic pressure of a suction port of the oil strainer, and the suction hydraulic pressure of the pressure sensor is lower than a set value, so that the suction port is closed. The hydraulic control device for an automatic transmission according to claim 1, wherein the hydraulic control device is configured to determine that the vehicle is exposed. 4. The exposure state detecting means includes a vehicle speed detecting means for detecting a vehicle speed, calculates a vehicle deceleration from the vehicle speed, and exposes the suction port when the deceleration is larger than a set value. The hydraulic control device for an automatic transmission according to claim 1, wherein the hydraulic control device is configured to determine that the vehicle is in a state.