JPH1163196A - Hydraulic control device in automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure responsiveness of clutch oil pressure by carrying out pre- charging corresponding to a demand from an initial speed change time after an engine is started, in a hydraulic control of an automatic transmission for carrying out pre-charging when a clutch is fastened. SOLUTION: Just after an ignition switch is turned on (S1), a time when an engine is stopped is estimated (S2). When a clutch is fastened firstly (S3, S4), a pre-charging rate is decided according to an engine stop time to be estimated (S5), a large pre-charging rate is applied when the engine stop time is long, and necessary invalid stroke is carried out even if there is drain of oil from a piping during stopping the engine.

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 an automatic transmission, and more particularly, to a hydraulic control device configured to precharge hydraulic oil when a frictional engagement element such as a clutch is engaged.

[0002]

2. Description of the Related Art Conventionally, in automatic transmissions for vehicles,
There is known a configuration in which the hydraulic oil is precharged when a frictional engagement element such as a clutch is engaged to ensure the responsiveness of the hydraulic pressure (Japanese Patent Application Laid-Open Nos. Hei 6-11032 and Hei 6-11028). JP, JP-A-8-3341
No. 71, etc.).

Generally, a gap is formed between the piston and the clutch plate so that the piston and the clutch plate do not come into contact with each other when the clutch is disengaged and dragging occurs. You need to move it by a minute. Therefore, before the fastening operation, the hydraulic oil is filled in the friction engagement element so as to stroke just before the contact, and the hydraulic oil supply for filling the gap between the piston and the clutch plate is performed. It is called precharge.

[0004]

However, if the engine is stopped and left for a long time, oil in the pipe of the automatic transmission will be drained. The demand for the precharge amount is different from that at the time of the middle fastening. However, conventionally, since the drainage of the oil while the engine is stopped is not taken into account, the stroke cannot be made to the position immediately before the contact by precharge at the time of the first engagement after the engine is started, and the response of the clutch hydraulic pressure after that However, there has been such a problem that the engagement timing deviates from the optimal timing, causing a shift shock (see FIG. 10).

The present invention has been made in view of the above-mentioned problems, and it is possible to reliably fill a gap by precharging even with an initial fastening after the engine has been left for a long time. Accordingly, it is an object of the present invention to provide a hydraulic control device for an automatic transmission that can ensure responsiveness of the subsequent engagement hydraulic pressure.

[0006]

According to a first aspect of the present invention, there is provided a hydraulic control device for an automatic transmission for precharging hydraulic oil when a friction engagement element is engaged. Is configured to change the precharge control amount according to the engine stop time when the fastening operation is the first operation after the engine is started.

With this configuration, when the engine is first engaged after the engine is started, the control amount of the precharge is changed depending on the engine stop time, and when the engine stop time is long and the oil drain from the pipe is large, the precharge is controlled. Increase the amount (time and / or fastening pressure indication). In the invention according to claim 2, the control amount of the precharge is changed based on the engine stop time and the oil temperature.

According to this configuration, the precharge at the time of the first engagement after the engine is started is changed according to the oil temperature at that time together with the engine stop time. Even if the engine stop time is the same, when the oil temperature is high, the hydraulic oil quickly flows into the friction engagement element and the required precharge time is shortened. Determined based on temperature.

According to the third aspect of the present invention, the engine stop time is estimated based on the oil temperature when the ignition switch is turned off and the oil temperature when the ignition switch is turned on. According to such a configuration, a change in the oil temperature when the engine is stopped can be known from the oil temperature when the ignition switch is turned off (when the engine is stopped) and the oil temperature when the ignition switch is turned on (when the engine is restarted). The longer the engine stop time, the greater the oil temperature drops during that time, so that the engine stop time can be estimated from the oil temperature change during the engine stop.

According to a fourth aspect of the present invention, the engine stop time is estimated based on a charge / discharge state of a charge / discharge circuit. According to this configuration, for example, if the capacitor is charged during the operation of the engine and the discharge is performed after the engine is stopped (ignition switch OFF), the discharge proceeds according to the elapsed time from the stop of the engine. Stop time can be estimated.

[0011]

According to the first aspect of the present invention, even if the engine is left for a long time and the oil in the pipe is drained, the precharge amount is appropriately set to ensure the first fastening after starting. There is an effect that the hydraulic oil can be filled and the response of the subsequent hydraulic pressure can be ensured.

According to the second aspect of the present invention, the precharge amount is determined in consideration of the oil temperature together with the engine stop time, so that the flow rate of the hydraulic oil into the friction engagement element varies depending on the oil temperature. In addition, there is an effect that appropriate filling of the working oil can be performed. According to the invention described in claim 3, there is an effect that the stop time of the engine can be estimated with a simple configuration based on the change in the oil temperature.

According to the fourth aspect of the present invention, there is an effect that the stop time of the engine can be accurately estimated by using the charge / discharge circuit.

[0014]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing an automatic transmission for a vehicle to which a hydraulic control device according to the present invention is applied. The output torque of an engine 1 mounted on a vehicle (not shown) is supplied to a drive wheel via an automatic transmission 2. Is transmitted to

The automatic transmission 2 has a structure in which gear shifting is performed by controlling the supply of operating hydraulic pressure to frictional engagement elements such as clutches and brakes by a solenoid valve unit 3. In this configuration, a shift (so-called clutch-to-clutch shift) in which the two frictional engagement elements are simultaneously engaged and released without using a one-way clutch is performed (see FIG. 2).

More specifically, as shown in FIG. 3, the automatic transmission 2 is configured to input the output torque of the engine via a torque converter T / C.
3, a rear planetary gear set 84 and a reverse clutch R / C, a high clutch H / C,
Band brake B / B, low & reverse brake L & R
/ B, a forward clutch FWD / C. In FIG. 3, 81 indicates an input shaft of the transmission, 82 indicates an output shaft of the transmission, Ne indicates an engine rotation speed, Nt indicates a turbine rotation speed, and No indicates an output shaft rotation speed.

In the above configuration, as shown in FIG. 4, the reverse clutch R / C, high clutch H / C, band brake B / B, low & reverse brake L & R /
B, a shift is performed in accordance with a combination of engagement and disengagement of the forward clutch FWD / C. For example, at the time of an upshift from the third speed to the fourth speed, release of the forward clutch FWD / C and engagement of the band brake B / B are performed. Will be performed simultaneously.

Each solenoid valve of the solenoid valve unit 3 is controlled by a control unit 4 having a built-in microcomputer. In the engagement control of a friction engagement element such as a clutch, hydraulic oil is precharged by The gap between the clutch plate and the piston is filled in advance. That is, when a shift request that requires the engagement operation of a friction engagement element such as a clutch occurs,
First, after performing a precharge and causing the friction engagement element to perform an invalid stroke immediately before contact, the operating oil pressure is maintained at a critical pressure just before the engagement force is generated, and thereafter, the engagement of the friction engagement element is performed at a predetermined timing. The operation hydraulic pressure is controlled so as to proceed.

The state of the precharge control will be described with reference to the flowchart of FIG. In the flowchart of FIG. 5, first, in step 1 (indicated as S1 in the figure, the same applies hereinafter), it is determined whether or not the ignition switch has just been turned on. , Engine stop time (estimate the time from the previous ignition switch OFF to the current ignition switch ON).

The method for estimating the engine stop time in step 2 will be described later. In step 3, it is determined whether or not there is a shift request. If there is a shift request, the process proceeds to step 4. In step 4, it is determined for each friction engagement element whether or not it is the first shift. That is, it is determined for each friction engagement element whether or not the friction engagement element such as a clutch is in the first engagement control after the engine is started.
In detail, since drainage of oil from inside the pipe while the engine is stopped poses a problem, it may be configured to determine whether supply of hydraulic oil is first for each pipe.

If it is determined in step 4 that it is the time of the first engagement control, the process proceeds to step 5, and the control amount of precharge is determined according to the engine stop time estimated in step 2. Here, the longer the engine stop time, the longer the precharge time and / or the higher the pre-charge command pressure. If the engine stop time is long, a large amount of oil in the piping will be drained during that time, and the amount of oil required during the initial engagement control after the engine starts will increase accordingly. The precharge control amount (time and / or command pressure) is changed to increase the amount.

If the oil temperature is high, the oil is quickly filled into the friction engagement element. Therefore, when the control amount of the precharge is changed according to the engine stop time, as shown in FIG. Even when the engine stop time is the same, it is preferable to shorten the precharge time (decrease the instruction pressure) as the oil temperature at that time is higher. On the other hand, when it is determined in step 4 that it is not the time of the first engagement control, the process proceeds to step 6, where a normal precharge control amount is set. The normal precharge control amount is a control amount suitable for a state in which the pipe is filled with an expected amount of oil in a released state, and is a control amount that is not affected by engine stop time. May be changed according to the oil temperature.

In step 7, based on the precharge control amount determined in step 5 or 6, the energization of the solenoid for controlling the supply of the hydraulic pressure to the friction engagement element is controlled. As described above, if the control amount of the precharge is changed in accordance with the engine stop time, even if the engine is stopped for a long time and the oil in the pipe is drained, the pre-charge corresponding to the drain is sufficient. Charging can be performed, and responsiveness of the clutch hydraulic pressure control thereafter can be ensured.

The engine stop time is strictly preferably a period during which the supply of hydraulic oil from the release of the frictional engagement element to the re-engagement of the frictional engagement element is stopped. Since there is no drain that causes a large change in the required precharge during operation, it is necessary and sufficient to determine the precharge amount according to the engine stop time.

The estimation of the engine stop time in step 2 is based on the fact that, in the case of a system having an oil temperature sensor, the oil temperature detected by the oil temperature sensor when the ignition switch is turned off is stored, and the oil temperature is detected when the ignition switch is turned on. This can be performed based on the oil temperature detected by the sensor and the stored oil temperature when the ignition switch was previously turned off.

That is, the engine stop time is estimated based on how much the oil temperature has dropped between the time when the ignition switch was turned off and the time when it was turned on. As shown in FIG. It is presumed that the shorter the oil temperature at ON, the shorter the engine stop time was compared to the oil temperature at OFF. Also, even if the oil temperature at ON was the same, the higher the oil temperature at OFF, the more the engine stopped. This is presumed to have been stopped for a long time.

In the case of a system originally provided with an oil temperature sensor, the time can be estimated without increasing the cost. Further, as shown in FIG.
And a charging / discharging circuit including a capacitor C and resistors R1 and R2, and a transistor TR for switching energization of the charging / discharging circuit.
In the N state, the transistor TR is turned on to charge the capacitor C. On the other hand, in the off state of the ignition switch, the transistor TR is turned off.
Then, when the capacitor C is discharged and the ignition switch is turned on, the terminal voltage of the capacitor C is read before the transistor TR is turned on and charging is started. The configuration may be such that the longer the engine stop time is, the longer the engine stop time (see FIG. 9).

As described above, if the engine stop time is estimated based on the charge / discharge state of the charge / discharge circuit,
The engine stop time can be more accurately estimated than a configuration in which the time is estimated based on the oil temperature.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an automatic transmission to which the present invention is applied.

FIG. 2 is a time chart showing a state of hydraulic control during shifting.

FIG. 3 is a configuration diagram showing details of an automatic transmission.

FIG. 4 is a view showing a state of shifting by a combination of engagement states of friction engagement elements in the automatic transmission.

FIG. 5 is a flowchart showing a state of precharge control.

FIG. 6 is a diagram showing characteristics of a precharge amount according to an engine stop time and an oil temperature.

FIG. 7 is a diagram showing characteristics of time estimation based on a key-on oil temperature and a key-off oil temperature.

FIG. 8 is a circuit diagram showing a charge / discharge circuit for performing time estimation.

FIG. 9 is a diagram showing a correlation between a voltage and an engine stop time.

FIG. 10 is a time chart for explaining a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Solenoid valve unit 4 Control unit 83 Front planetary gear set 84 Rear planetary gear set R / C reverse clutch H / C high clutch B / B band brake L & R / B low & reverse brake FWD / C forward clutch

Continued on the front page (72) Inventor Hiroyuki Yuasa 1370 Onna, Atsugi-shi, Kanagawa Prefecture Inside Unisia Gex Co., Ltd.

Claims (4)

[Claims] 1. A hydraulic control device for an automatic transmission for precharging hydraulic oil when engaging a friction engagement element, wherein the engagement operation of the friction engagement element is performed first after the engine is started. A hydraulic control device for an automatic transmission, wherein the control amount of the precharge is changed according to a stop time of an engine. 2. The hydraulic control device for an automatic transmission according to claim 1, wherein the control amount of the precharge is changed based on an engine stop time and an oil temperature. 3. The engine stop time is determined by the oil temperature when the ignition switch is turned off and the ignition switch O
The hydraulic control device for an automatic transmission according to claim 1, wherein the estimation is performed based on an oil temperature at the time of N. 4. The hydraulic control device for an automatic transmission according to claim 1, wherein the stop time of the engine is estimated based on a charge / discharge state of a charge / discharge circuit.