JP4011255B2 - Hydraulic control device for automatic transmission - Google Patents

Description

[0001]
BACKGROUND 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 pressure when a frictional engagement element such as a clutch is engaged.
[0002]
[Prior art]
Conventionally, in an automatic transmission for a vehicle, when a frictional engagement element such as a clutch is fastened, a hydraulic pressure is precharged with respect to the frictional engagement element to prevent an operation delay of the frictional engagement element. Is known (see JP-A-5-106722).
[0003]
[Problems to be solved by the invention]
However, conventionally, when the frictional engagement element to be fastened is a frictional engagement element that has been release-controlled immediately before, there is a possibility that precharge may be performed in a state where the hydraulic pressure is not fully released. The precharge is normally performed on the friction engagement element in a state where the hydraulic pressure has been completely released, and the precharge pressure and the precharge time are set in accordance with such conditions. If precharging is performed in a state where the engine is not turned off, the hydraulic pressure increases excessively due to the precharging, which may cause a large shift shock.
[0004]
The present invention has been made in view of the above problems, and even if precharging is performed in a state where the hydraulic pressure is not fully removed, an excessive increase in the hydraulic pressure can be avoided, so that a shift shock can be prevented. An object of the present invention is to provide a hydraulic control device for an automatic transmission that can be avoided.
[0005]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, there is provided a hydraulic control device for an automatic transmission that precharges hydraulic pressure when the friction engagement element is fastened, and the indicated hydraulic pressure for the friction engagement element is zero in the previous release control. The precharge is corrected and controlled in accordance with the descending speed of the command oil pressure in the process of decreasing to the point and the elapsed time after the command oil pressure becomes zero .
[0006]
According to such a configuration, the actual engagement hydraulic pressure delay changes depending on the change speed when the command oil pressure is decreased toward zero, and the command oil pressure change speed even if the elapsed time after the command oil pressure becomes zero is the same. Are different from each other, the engagement hydraulic pressure of the friction engagement element shows a different value, so that the immediately before the start of precharge depends on the change speed until the command hydraulic pressure becomes zero and the elapsed time after it becomes zero. The engagement hydraulic pressure is estimated, and precharging is performed with characteristics according to the residual pressure at that time.
[0007]
According to a second aspect of the present invention, the higher the descending speed and the shorter the elapsed time, the lower the indicated hydraulic pressure in the precharge and / or the shorter the precharge time.
[0008]
According to this configuration, the longer the elapsed time, the higher the precharge command pressure and the longer the precharge time, while the faster the command pressure drop rate, the same elapsed time in the precharge. Set the indicated pressure lower and the precharge time shorter.
[0009]
【The invention's effect】
According to the first and second aspects of the invention, the residual pressure at the start of precharge can be accurately estimated in response to a change in the delay of the engagement hydraulic pressure due to the change speed of the indicated hydraulic pressure. By correcting the precharge in some cases, there is an effect that the supply of excessive hydraulic pressure can be avoided and the occurrence of shift shock can be prevented.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
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 applied to an output shaft 2 a of the automatic transmission 2. To the driving wheel (not shown).
[0011]
The automatic transmission 2 has a configuration in which a shift is performed by controlling the supply of engagement hydraulic pressure to friction engagement elements such as various clutches and brakes by a solenoid valve unit 3. In the present embodiment, a shift is performed in which the engagement and release of the two friction engagement elements are simultaneously performed by hydraulic control without using the one-way clutch, and as shown in FIG. The engagement hydraulic pressure of the friction engagement element to be fastened is gradually increased while gradually reducing the engagement hydraulic pressure of the friction engagement element to be changed, and the torque is switched from the release side friction engagement element to the fastening side friction engagement element. Is to be done.
[0012]
Specifically, as shown in FIG. 3, the automatic transmission 2 is configured to input engine output torque via a torque converter T / C, and includes a front planetary gear set 83 and a rear planetary gear set 84. In addition, a reverse clutch R / C, a high clutch H / C, a band brake B / B, a low & reverse brake L & R / B, and a forward clutch FWD / C are provided as friction engagement elements. 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.
[0013]
In the above configuration, as shown in FIG. 4, the reverse clutch R / C, the high clutch H / C, the band brake B / B, the low & reverse brake L & R / B, and the forward clutch FWD / C are combined and released. For example, during the upshift from the 3rd speed to the 4th speed, the forward clutch FWD / C is disengaged and the band brake B / B is engaged at the same time.
[0014]
Each solenoid valve of the solenoid valve unit 3 is controlled by a control unit 4 with a built-in microcomputer. In the engagement control of a friction engagement element such as a clutch, the engagement hydraulic pressure is precharged, and the clutch plate It is comprised so that the clearance gap between a piston may be filled beforehand.
[0015]
That is, when a shift request requiring a fastening operation of a frictional engagement element such as a clutch is generated, first, precharging is performed to make the frictional engagement element invalid stroke until just before contact, and then the engagement hydraulic pressure is applied to the engagement force. The critical pressure generated is held at the critical pressure, and then the engagement of the frictional engagement element is performed in synchronization with the release control.
[0016]
Here, the details of the precharge control will be described with reference to the flowchart of FIG. In the flowchart of FIG. 5, first, in step S21, it is determined whether or not the command pressure P of the friction engagement element that has been subjected to the engagement control at the previous shift is 0 (a value corresponding to complete release), and the command pressure P is 0. If not, the process proceeds to step S22, and the timer TMR1 that is incremented by one per unit time is reset to zero.
[0017]
Note that the command pressure P = 0 indicates the complete release control state in the present embodiment. Therefore, when the command pressure P = 0 is not satisfied in the complete release control state, the command pressure P = 0 is a value corresponding to the complete release control state. It may be configured to determine whether or not there is.
[0018]
Further, in step S23, a decrease speed ΔP of the command pressure P in the process in which the command pressure P decreases to 0 is calculated. On the other hand, if it is determined in step S21 that the command pressure P is 0, the process proceeds to step S24, and whether or not to start the engagement control at the current shift with respect to the friction engagement element that has been release-controlled at the previous shift. Determine.
[0019]
When performing the engagement control, the process proceeds to step S25, and a correction coefficient Pα for correcting the basic value of the command pressure in the precharge is set based on a value of a timer TMR2 to be described later and a decrease rate ΔP of the command pressure P. In step S26, the correction coefficient Tα for correcting the basic value of the precharge time is set based on the value of the timer TMR2 and the decrease rate ΔP of the command pressure P. In step S27, the correction coefficient Tα is preliminarily set with the correction coefficients Pα and Tα. The command pressure and the precharge time for charging are determined, and the command pressure of the friction engagement element to be fastened is output.
[0020]
The timer TMR2 is a timer for measuring an elapsed time after the value of the timer TMR1 becomes a predetermined value T1, and the predetermined value T1 is a friction engagement element after the command pressure P becomes 0. Is set in advance as a delay time until the hydraulic pressure in the hydraulic pipe supplying the hydraulic pressure is delayed to zero, and the engagement hydraulic pressure of the friction engagement element is delayed with respect to the hydraulic pressure in the hydraulic pipe. Since it changes to 0, the engagement hydraulic pressure (residual pressure) of the friction engagement element can be estimated from the time after the hydraulic pressure in the hydraulic piping measured by the timer TMR2 becomes zero.
[0021]
As shown in FIGS. 6 and 7 , the correction coefficients Pα and Tα are set such that the longer the measurement time by the timer TMR2, the higher the command pressure in precharge and the longer the precharge time. The higher the pressure drop rate ΔP, the lower the command pressure for precharge and the shorter the precharge time for the same timer TMR2.
[0022]
In the above embodiment, the engagement hydraulic pressure of the friction engagement element is estimated from the command pressure P, and the delay time of the engagement hydraulic pressure of the friction engagement element with respect to the command pressure P is influenced by the change speed of the command pressure P. Therefore, the correction coefficients Pα and Tα are set according to the decrease rate ΔP of the command pressure P together with the timer TMR2.
[0023]
When the speed at which the command pressure P decreases to 0 is high, the actual hydraulic pressure of the friction engagement element is delayed to decrease, and the residual pressure for the same elapsed time is higher than when the speed is slow. Therefore, the higher the speed at which the command pressure P decreases to 0, the lower the command pressure in precharge and the shorter the precharge time.
[0024]
According to the above embodiment, the remaining pressure at the start of precharging can be accurately estimated in response to a change in the delay of the engagement oil pressure due to the change speed of the indicated oil pressure. By correcting this, it is possible to avoid excessive supply of hydraulic pressure, thereby preventing the occurrence of shift shock.
[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 diagram 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 precharge control in the embodiment.
FIG. 6 is a diagram showing characteristics of precharge command pressure in the embodiment.
FIG. 7 is a diagram showing characteristics of precharge time in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Automatic transmission 3 ... Solenoid valve unit 4 ... Control unit 5 ... Hydraulic sensor 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

Claims (2)

A hydraulic control device for an automatic transmission that precharges hydraulic pressure when fastening a friction engagement element,
The precharge is corrected in accordance with the descending speed of the command hydraulic pressure in the process in which the command hydraulic pressure for the friction engagement element decreases to zero in the previous release control and the elapsed time since the command hydraulic pressure becomes zero. hydraulic control apparatus for an automatic transmission and to control. 2. The automatic shift according to claim 1, wherein the higher the descending speed and the shorter the elapsed time, the lower the command hydraulic pressure in the precharge and / or the shorter the precharge time. Hydraulic control device for the machine.