JPH07174224A - Lockup controller for automatic transmission - Google Patents

Abstract

PURPOSE:To prohibit lockup so as to eliminate any harmful effect on an automatic transmission during boasting when a torque converter is hard to be shifted from its converter state to its lockup state on account of a decrease in operation oil quantity. CONSTITUTION:A controller 9 shift-controls an automatic transmission 2 according to throttle opening TH and vehicle speed V via solenoids 6, 7 and also lockup-controls a torque converter 3 via a solenoid 8. The controller 9 also detects coasting based on difference between torque converter input rotation speed Ne and torque converter output rotation speed found by vehicle speed V and gear ratio and prohibits lockup of the torque converter 3 during the coasting, even if a region is converted from the converter region to the lockup region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lockup control device for an automatic transmission mounted on a vehicle.

[0002]

2. Description of the Related Art An automatic transmission has a torque converter for the purpose of improving the fuel efficiency by improving the transmission efficiency, under the condition that the torque increasing function and the torque fluctuation absorbing function by the torque converter are not required. There is a tendency to switch to a lock-up type that can be brought into a directly connected lock-up state.

In the lock-up control of this kind of torque converter, a specific shift is conventionally used, for example, as described in the automatic transmission described in "NISSAN RE4R01A type full range electronic control automatic transmission maintenance manual" issued by the applicant of the present application. For each gear position or each gear position, which one of the lockup region and the converter region is specified by the throttle opening TH (engine load) and the vehicle speed V as shown in FIG. It is common practice to make a determination and place the torque converter in a lockup state in which the input / output elements are directly connected or in a converter state in which the direct connection is released, depending on the result of the determination.

[0004]

However, in such a conventional lock-up control technique, since the torque converter is simply locked up in accordance with the above determination result, it is assumed that the vehicle shifts from acceleration to coasting. Also, since the throttle opening is changed, the converter state of the torque converter is switched to the lockup state, which causes the following problems.

That is, when the vehicle coasts, the throttle valve of the engine tends to be closed, so that the engine speed becomes considerably low. On the other hand, lockup of the torque converter is performed by hydraulic oil from a pump driven by the engine, similar to shift control of the automatic transmission, but during coasting, the amount of hydraulic oil from the pump is also low because the engine speed is low. Few. This small amount of hydraulic oil can maintain the lockup state of the torque converter, but the amount of oil is insufficient to switch the torque converter from the converter state to the lockup state. Difficult to do.

As shown by hatching in FIG. 4, the lockup instability region is a region where the throttle opening is lower than the so-called road load line b which indicates the throttle opening required to maintain this for each vehicle speed. Expressed as

To add the above facts to FIG. 4, point W
When the traveling state in which the throttle opening TH is reduced from X to X is in the lockup region, it is only necessary to keep the lockup state of the torque converter. There is no problem even if the amount of hydraulic oil from the pump decreases as the temperature decreases. However, since the transition from the converter region to the lockup region occurs when the traveling state in which the throttle opening TH is reduced from the point Y to Z is transitioned, it is necessary to switch the torque converter from the converter state to the lockup state. If the engine speed decreases and the amount of hydraulic oil from the pump decreases due to the up-stability region, the state switching of the torque converter becomes uncertain.

This uncertainties keep the gap between the lockup clutch piston and the converter cover to which the piston is pressed in large, and increase the amount of hydraulic oil drained through this gap, resulting in the drainage. The rear lubrication of the automatic transmission, which is covered by the torque converter oil amount excluding the amount, becomes insufficient, and the durability of the automatic transmission is reduced.

According to the present invention, even if there is a region transition from the converter region to the lockup region, the lockup of the torque converter is prohibited during coasting of the vehicle, which is in the above-mentioned lockup unstable region. The purpose is to solve the problem of.

[0010]

To this end, a lockup control device for an automatic transmission according to the present invention is equipped with an automatic transmission having a lockup-capable torque converter in its transmission system, as shown in the concept of FIG. In the vehicle, from the converter area that should not lock up the torque converter, the area transition determination means that determines the area transition to the lockup area that should be locked up, and the coasting detection means that detects the coasting of the vehicle, During the detection of coasting by the means, lockup prohibition means for prohibiting lockup of the torque converter is provided even if the area transition determination means detects the area transition.

[0011]

The torque converter is put into the converter state or put into the lockup state depending on whether the converter region is not to be locked up or the lockup region is to be locked up.

By the way, while the coasting detection means detects the coasting of the vehicle, even if the area shift judging means judges the area shift from the converter area to the lockup area, the torque is locked by the lockup prohibiting means. Disable converter lockup. Therefore, even though it is difficult to switch the torque converter from the converter state to the lockup state because the engine speed becomes considerably low during coasting of the vehicle and the amount of hydraulic oil from the engine-driven pump is small. Forcing this switching operation,
It is possible to avoid stupidity that causes insufficient rear lubrication of the automatic transmission.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows a lockup control device for an automatic transmission according to an embodiment of the present invention. In FIG.
Is an engine and 2 is an automatic transmission. The automatic transmission 2 receives the power of the engine 1 via the torque converter 3,
It is assumed that the input rotation is changed in speed with a gear ratio according to the selected speed and transmitted to the output shaft 4.

In the automatic transmission 2, the shift solenoids 6 and 7 in the control valve 5 are turned on and off.
The selected shift speed is determined by the combination of the above, and the torque converter 3 is set to the converter state or the lockup state by turning on and off the lockup solenoid 8 in the control valve 5.

ON / OFF of shift solenoids 6 and 7,
A controller 9 controls ON and OFF of the lockup solenoid 8 and a signal from an engine rotation sensor 10 for detecting the rotation speed Ne of the engine 1 (input rotation speed of the torque converter 3) Ne. , A signal from a throttle opening sensor 11 for detecting the throttle opening TH of the engine 1 and a signal from a vehicle speed sensor 12 for detecting the rotation speed (vehicle speed V) of the transmission output shaft 4 are input.

Although not shown, the controller 9 performs the following shift control by well-known calculation based on these input information. That is, first, the optimum shift speed for the current driving state is obtained from the throttle opening TH and the vehicle speed V by, for example, a table lookup method, and the shift solenoids 6 and 7 are turned on and off so that the optimum shift speed is selected. To perform a predetermined gear shift.

In addition to such shift control, the controller 9 executes the control program of FIG. 3 to perform lockup control of the torque converter 3 described below. First,
In step 21, the engine throttle opening TH and the vehicle speed V are read. Then, in step 22, whether or not there is a region transition from the converter region to the lockup region due to a change in the operating state from point Y to Z shown in FIG. 4 based on the lockup map consisting of the engine throttle opening TH and the vehicle speed V is determined. To check. If there is no transition to this area, lockup is not performed and control ends.

When it is determined in step 22 that there is a region transition from the converter region to the lockup region, in step 22, the engine revolution speed Ne, which is the input revolution speed of the torque converter 3, is read, and in step 25, the torque converter. The turbine rotation speed Nt which is the output rotation speed of 3 is calculated. In this calculation, the turbine rotation speed Nt is obtained by multiplying the transmission output rotation speed detected by the sensor 12 and the selected shift speed (current gear ratio) which is known from the combination of ON and OFF of the shift solenoids 6 and 7. Ask.

In the next step 26, the slip amount Ne-Nt of the torque converter 3 obtained by the difference between the input / output speeds Ne and Nt of the torque converter 3 is the set slip amount ΔNs corresponding to the load / load line b in FIG. Whether or not it is in the lockup unstable region of FIG. 4 is checked depending on the following. In addition, the inertial running of the vehicle is basically
It can be detected when the slip amount Ne-Nt of the torque converter 3 becomes negative, but in reality, it is necessary to allow a margin in consideration of the operating characteristics and the rotation error of the lockup clutch piston. Needless to say.
If it is not in the lockup unstable region, in step 27, the lockup command is output to the lockup solenoid 8 to cause the torque converter 3 to shift to a region from the converter region to the lockup region, and the lockup state is obtained. To

However, when it is determined in step 26 that the lockup region is in the lockup unstable region of FIG. 4, the control is terminated as it is and the above step 27 is skipped to change the region from the converter region to the lockup region. Despite the shift, the lockup of the torque converter 3 is not performed, and the lockup is substantially prohibited.

Thus, during coasting of the vehicle that has entered the above lockup unstable region, the engine speed becomes considerably low and the amount of hydraulic oil from the pump driven by the engine is small, so the torque converter is locked from the converter state. Although it is difficult to switch to the up state,
By carrying out this switching operation, it is possible to avoid the foolishness of causing insufficient rear lubrication of the automatic transmission.

The above operation is not limited to the case where there is a region transition from the converter region to the lockup region due to the throttle opening decrease from point Y to Z shown in FIG. The same applies when there is a region transition from the converter region to the lockup region due to a gearshift or a gearshift by operating the OD prohibition switch, or when relocking after a temporary lockup is released as a shock countermeasure during a gearshift. The above effects can be achieved.

Basically, the inertial running of the vehicle can be detected when the slip amount Ne-Nt of the torque converter 3 becomes negative, but in reality, the operating characteristics and rotation of the lockup clutch piston are detected. Considering the error,
It goes without saying that it is necessary to have a margin.

As described above, according to the lock-up control device of the present invention, when the vehicle coasts, the torque converter lock-up is performed even if the converter region is shifted to the lock-up region. Since this is prohibited without performing this, the engine speed will be considerably low during coasting of the vehicle and the hydraulic oil from the pump driven by the engine will be small, so the torque converter will be locked up from the converter state. Even though it is difficult to switch to,
It is possible to avoid stupidity that causes insufficient rear lubrication of the automatic transmission.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a lockup control device for an automatic transmission according to the present invention.

FIG. 2 is a system diagram showing an embodiment of a lockup control device of the present invention.

FIG. 3 is a flowchart of a lockup control program executed by the controller in the same example.

FIG. 4 is a diagram showing a lockup region and a lockup unstable region of the torque converter.

[Explanation of symbols]

 1 Engine 2 Automatic Transmission 3 Torque Converter 5 Control Valve 6 Shift Solenoid 7 Shift Solenoid 8 Lockup Solenoid 9 Controller 10 Engine Rotation Sensor 11 Throttle Opening Sensor 12 Vehicle Speed Sensor

Claims (1)

[Claims] 1. In a vehicle equipped with an automatic transmission having a lockup-capable torque converter in a transmission system, a region transition from a converter region where the torque converter should not be locked up to a lockup region where it should be locked up. Area transition determination means for determining, inertial traveling detection means for detecting inertial traveling of the vehicle, and while the inertial traveling is being detected by the means, even if area transition is detected by the area transition determining means, the torque converter is locked. A lock-up control device for an automatic transmission, comprising: a lock-up prohibiting means for prohibiting a lock-up.