JPH03117770A - Speed change controlling device for automatic transmission - Google Patents

Abstract

PURPOSE:To achieve more proper change characteristics by providing a friction coefficient detecting means for detecting the friction coefficient of a road surface, and a reference value changing means for changing a reference value corresponding to the size of the detected friction coefficient. CONSTITUTION:A control unit U basically performs speed change control based on an economy mode, which is changed to a power mode when a throttle opening change ratio DELTATVO showing a change ratio of an engine load gets over a predetermined reference value for achieving speed change control. In this case, by seeing the degree of a vehicle body acceleration relative to the size of a rotation acceleration of a drive wheel, for example, the friction coefficient of a road surface is detected, and two sorts of maps for setting the reference value DELTATVO taking a throttle opening and a vehicle speed for parameters are set based on if the friction coefficient is more than an predetermine threshold value or not. The reference value DELTATVO is therefore changed corresponding to the friction coefficient of the road surface, and the larger the friction coefficient is, the less slipping will occur, or the more sufficient acceleration ability can be obtained, where the reference value DELTATVO becomes smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a shift control device for an automatic transmission that changes shift characteristics as appropriate.

(Prior Art) In recent automatic transmissions, it has become common to have transmission characteristics that can be changed as appropriate. In such automatic transmissions, two shift characteristics are normally prepared in advance, for example, an economy mode shift characteristic and a power mode in which the shift line is set to a higher vehicle speed than the economy mode, and for example, manual selection is possible. Therefore, the speed change control is performed with any desired speed change characteristics.

As mentioned above, among those having a plurality of shift characteristics, there have also been proposed ones in which the shift characteristics are automatically changed according to the engine load. Japanese Patent Publication No. 57-8983 states that while gear change control is normally performed based on the economy mode, when the engine load exceeds a predetermined reference value, for example when the throttle opening is 3/4 or more, the shift control is performed in the power mode. A method for performing speed change control based on the above-mentioned information has been disclosed. That is, when the engine load is above a certain reference value, it is assumed that a large engine output (torque) is required, and the power mode is automatically selected.

Furthermore, Japanese Patent Publication No. 51-22698 proposes a system that switches to power mode when the accelerator is suddenly depressed, that is, when the rate of change in engine load exceeds a predetermined reference value. ing.

(Problem to be Solved by the Invention) However, in the method described in the above publication, the reference value when switching to power mode is set to a certain value, so it is not always possible to select an appropriate shift characteristic. It becomes something you can't get.

To explain this point more specifically, first, when the friction coefficient of the road surface is small, such as during rainy or snowy weather, the driver must be careful when operating the accelerator to avoid slipping. On the other hand, when the power mode is selected, there is an increased chance that the torque applied to the drive wheels will be increased, that is, there will be an increased chance that slip will occur. Therefore, even if the reference value for changing the gear shift line is optimally set for dry roads, the shift line will be changed too sensitively when it snows.
In other words, unnecessary drive torque that is not requested by the driver acts on the drive wheels, making it more likely that slips will occur.

Therefore, it is an object of the present invention to provide more appropriate shift characteristics, based on the premise that the shift line is changed to a higher vehicle speed side when the engine load or the rate of change in the engine load exceeds a predetermined reference value. An object of the present invention is to provide a shift control device for an automatic transmission that can perform the following steps.

(Structure of the Invention) In order to achieve the above-mentioned object, the present invention has the following structure. That is, in an automatic transmission that changes the shift line to a higher vehicle speed side when the engine load or the rate of change in the engine load exceeds a predetermined reference value, the friction coefficient detection means detects the friction coefficient of the road surface. and a reference value changing means for changing the reference value according to the magnitude of the friction coefficient detected by the friction coefficient detecting means.

(Operations and Effects of the Invention) As described above, in the present invention, the reference value for changing the gear shift line is changed according to the coefficient of friction of the road surface, so that the gear shift line can be set more appropriately to meet the driver's will. It is possible to prevent or significantly suppress the possibility that a contrary shift characteristic is automatically selected.

(Example) Examples of the present invention will be described below based on the attached drawings.

In FIG. 1, reference numeral 1 denotes an automatic engine, and the output (torque) of the engine 1 is transmitted to drive wheels (not shown) via an automatic transmission 2. In FIG.

In the embodiment, the automatic transmission 2 includes a lock-up clutch 3.
It is comprised of a torque converter 3 equipped with A, and a multi-speed gear mechanism 4 with four forward speeds and one reverse speed. The automatic transmission 2 is hydraulically operated, and the lock-up clutch 3A is engaged and engaged by switching between energization and demagnetization of a solenoid 5 incorporated in the hydraulic circuit. Further, by changing the combination of excitation and demagnetization of the plurality of solenoids 6 incorporated in the hydraulic circuit, the speed of the multi-speed gear mechanism 4 is changed.

In FIG. 1, U is a control unit for speed change control configured using a microcomputer. Signals from sensors or switches 21 to 24 are input to the control unit U, while signals from the control unit U are inputted to the control unit U. Said solenoid5.
6 is output.

The sensor 21 detects the throttle opening. The sensor 22 detects heavy speed. switch 2
3 is for selecting the speed change characteristic, and in the embodiment, it is a manual operation type, and is used to select the economy mode shown in FIG. 2, the power mode shown in FIG. 3, and the selection of both modes. Four types of selections are made: an automatic (automatic switching) mode, which automatically selects the mode, and a hold mode. In the embodiment, when the economy mode or the power mode is selected by the switch 23, the selected speed change characteristics are fixed and are not changed. Further, as is known, the hold mode is fixed at 3rd speed when in the D range, fixed at 2nd speed when in the 2nd range, and fixed at I speed when in the ■ range. Then, the automatic mode is the object of the present invention,
While the economy mode is normally selected, when the engine load exceeds a predetermined reference value, a switch is made to select the power mode. Note that the present invention can also be applied when the economy mode is selected by the switch 23. The switch 24 detects the friction coefficient of the road surface, that is, the degree of slipperiness of the road surface, and in the embodiment, it is operated manually from the driver's cab. There are various other methods for detecting the friction coefficient of the road surface, such as determining that the friction coefficient of the road surface is small when the wiper switch is activated, or determining the degree of vehicle acceleration relative to the rotational acceleration of the drive shaft. This can be done by looking.

The outline of the control by the control unit U is as follows. First, assuming that the automatic mode is selected by the switch 23, basically the economy mode shown in FIG. 2 can be selected, and the speed change control is performed based on the economy mode.

T to throttle opening change rate, which indicates the rate of change in engine load
When VO exceeds a predetermined reference value, the economy mode is switched to the power mode, and gear shift control is performed based on the power mode.

The above reference value △TVO for switching to the above power mode
is basically determined by a map value set using throttle opening TVO and vehicle speed VSP as parameters. FIGS. 4 and 5 show the tendency of correspondence between ΔTVO as a reference value (map value) and the throttle opening degree and vehicle speed as parameters. Such a reference value ΔTVO
is also changed depending on the coefficient of friction of the road surface. Figure 6 shows the tendency of the TVO to correspond to the friction coefficient of the road surface and the standard value. The value ΔTVO is small.

In this embodiment, when setting the reference value △TVO, a map (reference value There are two types of settings for △TVO settings. Of course, if the throttle opening and vehicle speed are the same, the map value will change to the reference value △ when the friction coefficient of the road surface is large.
The TVO is set to be small.

In the embodiment, after switching to the power mode as described above, the mode is returned to the economy mode after a predetermined period of time has elapsed from the time of switching to the power mode. Note that this predetermined time may be changed depending on the engine load and the like.

Next, the details of the control by the control unit U will be explained in the eighth section.
This will be explained with reference to the flowchart shown in the figure. Note that in the following explanation, P indicates a step.

First, in the PI, signals from the sensors 21 to 24 are read. Next, in P2, it is determined whether the coefficient of friction of the road surface is small. When the determination in P2 is No, the gain α (reference value ΔTVO) for normal use, that is, for dry roads, is read from the map in P3. In P4, the rate of change ΔTVO of the throttle opening is calculated by differentiating the throttle opening (determining the deviation from the previously sampled throttle opening).

At P5, it is determined whether the rate of change ΔTVO calculated at P4 is greater than or equal to the reference value α read at P3. When the determination in P5 is No, the economy mode is selected as the shift characteristic in P6. Further, when the determination in P5 is YES, the power mode is selected in PI. When this power mode is selected, the process waits for a predetermined time to elapse in P8 (power mode continues), and then returns (may proceed to P6).

When the determination in P2 is YES, pH shift processing is performed. This P11100 process is performed when the coefficient of friction of the road surface is small and corresponds to the process of transitioning to P3 in Section 111, so the repeated explanation of "R" will be omitted.However, the above P3
β is used instead of α, which corresponds to α, but this β must be larger than α (see Figure 6).

Although the embodiment has been described above, the engine f''i load itself may be used instead of the rate of change of the engine f1 load as the reference value for switching to the power mode. , it is possible to use only a part of the shift line, for example, only for shifting between 2nd and 3rd speeds.Furthermore, depending on the friction coefficient of road 1, the standard value for changing the shift line may be set to 3 or more levels or It may be changed to a continuously variable type.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of speed change characteristics in economy mode. FIG. 3 is a diagram showing an example of shift characteristics in power mode. FIG. 4 and FIG. 5 are diagrams showing the tendency of correspondence between the throttle opening degree and vehicle speed and the reference value for power mode setting. FIG. 6 is a diagram showing the tendency of correspondence between the coefficient of friction of the road surface and the reference value for setting the power mode. FIG. 7 is a flowchart showing a control example of the present invention. U2 control wholesale unit l: Engine 2: Automatic transmission 3: Torque converter 4: Multi-speed gear mechanism 6: Solenoid (for shifting) 21: Sensor (throttle opening) 22: Sensor (vehicle speed) 23: Switch (shifting characteristics) (For selection) 24: Switch (for road surface friction coefficient) Fig. 2 (Eco/S) Fig. 3 Fig. 4 Fig. TV○ (Suro/Soto 1 and Mυ ship) Fig. 5 SP (1 release) Road surface washing

Claims (1)

[Claims] (1) In an automatic transmission that changes the gear shift line to a higher vehicle speed side when the engine load or the rate of change in the engine load exceeds a predetermined reference value, a friction coefficient detection means for detecting the friction coefficient of the road surface. and a reference value changing means for changing the reference value according to the magnitude of the friction coefficient detected by the friction coefficient detecting means. A shift control device for an automatic transmission, comprising: