JPH05106718A - Shift control method for automatic transmission - Google Patents

Abstract

PURPOSE:To provide a shift control method which can prevent the worsening of riding feeling that accompanies an abrupt down shift of more than three steps, in the case of an automatic transmission which attains plural shift steps by controlling electronically and respectively feed oil pressure to plural friction engagement elements and conducting the selective engagement of these friction elements. CONSTITUTION:In the case of an automatic transmission which attains plural shift steps by controlling electronically and respectively feed oil pressure to plural number of friction engagement elements and conducting the selective engagement of these friction elements, when there occurs a situation in which a down shift of more than three steps from a high speed side shift step to a low speed side shift step is necessary, this down shift is regulated to a down shift of up to two steps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention achieves a plurality of gear stages by electronically controlling the hydraulic pressure supplied to a plurality of friction engagement elements to selectively engage these friction engagement elements. The present invention relates to a shift control method capable of reducing discomfort associated with a large downshift in an automatic transmission.

[0002]

2. Description of the Related Art An automatic transmission for a vehicle is configured so that any rotary element in a gear transmission can be transmitted to a transmission input shaft by selectively supplying or discharging pressure oil to or from a friction engagement element such as a clutch or a brake. And is fixed to the transmission casing so that the gear ratio is automatically switched according to the operating state of the vehicle.

In such an automatic transmission, in order to protect various devices and equipment and maintain a comfortable riding comfort, it is required that a shock during gear shifting is small. Therefore, there has been proposed an automatic transmission intended to reduce shift shock by appropriately electronically controlling the pressure of the pressure oil with respect to the friction engagement element and the supply / discharge timing thereof.

As shown in FIG. 4, which shows a schematic structure of an example of such a conventional automatic transmission, an impeller 14 of a torque converter 13 is integrally connected to a crankshaft 12 of an engine 11. The torque converter 13 includes the impeller 14, the turbine 15, a stator 16 and a one-way clutch 17. The stator 16 includes the one-way clutch 1.
7, the stator 16 rotates in the same direction as the crankshaft 12 by the one-way clutch 17, but the rotation in the opposite direction is not allowed. The torque transmitted to the turbine 15 is applied to the input shaft of the gear transmission (hereinafter, referred to as a transmission input shaft) which is arranged in the rear portion of the torque converter 13 and which achieves four forward gears and one reverse gear. It is transmitted to 19).

This gear transmission has three sets of clutches 2.
0, 21, 22 and two sets of brakes 23, 24, one set of one-way clutch 25, and one set of Ravigneaux type planetary gear mechanism 26. The Ravigneaux type planetary gear mechanism 26 includes a ring gear 27, a long pinion gear 28, a short pinion gear 29, a front sun gear 30, and a rear sun gear 3.
1 and a carrier 32 that rotatably supports the pinion gears 28 and 29 and is rotatably fitted to the transmission input shaft 19.

The ring gear 27 is connected to the transmission output shaft 33, and the front sun gear 30 is connected to the transmission input shaft 1 via the kickdown drum 34 and the front clutch 20.
9, the rear sun gear 31 is further connected to the rear clutch 2
It is connected to the transmission input shaft 19 via 1. The carrier 32 is connected to the transmission case 18 via a low reverse brake 24 and a one-way clutch 25 which are arranged in parallel with each other, and a fourth speed clutch arranged at the rear end of the gear transmission. Transmission input shaft 1 through 22
It is connected to 9. In addition, the kick down drum 34
Is the transmission case 1 by the kick-down brake 23.
The torque passing through the Ravigneaux type planetary gear mechanism 26 is transmitted from the drive gear 35 fixed to the transmission output shaft 33 to the drive shaft side of the drive wheel (not shown).

Each of the clutches 20 to which are friction engagement elements
22 and the brakes 23 and 24 are each configured by a hydraulic device including an engagement piston device or a servo device, and hydraulic control is performed by pressure oil generated by an oil pump 36 connected to the impeller 14 of the torque converter 13. It is designed to be operated via a device.

The detailed structure and operation are described in, for example, Japanese Patent Application Laid-Open No. 58-46248 and Japanese Patent Application Laid-Open No. 58-5427.
This is already well known in Japanese Patent Laid-Open No. 0 or Japanese Patent Application Laid-Open No. 61-31749, etc., and depends on the position selected by the driver of the gear shift lever provided in the driver's seat of the vehicle (not shown) and the operating state of the vehicle. The respective frictional engagement elements are selectively engaged, and various shift speeds are automatically achieved through the hydraulic control device based on a command from an electronic control unit that controls the operating state of the engine 11.

The select pattern by the shift lever is P (parking), R (reverse), N (neutral), D (forward 3 speed automatic shift or forward 4 speed automatic shift), 2 (forward 2 speed automatic shift), It is L (fixed to 1st speed). Then, when an auxiliary switch (not shown) (hereinafter referred to as an overdrive switch) is operated in a state in which the shift lever is set to the D range, it is possible to switch between selection of forward three-speed automatic shift or forward four-speed automatic shift. It has become. How the respective friction engagement elements work when the speed change lever is held in each range of the select pattern is as shown in FIG. 5, and the circles in the figure indicate the hydraulic operation. It shows that they are in the engaged state, but the mark ● indicates that they are engaged only when the L range is selected.

Conventionally, when automatically shifting a vehicle equipped with such an automatic transmission, the traveling speed of the vehicle (hereinafter,
The vehicle speed) and the opening degree of a throttle valve (not shown) that can change the opening degree of the intake passage (not shown) of the engine 11 in conjunction with the depression amount of an accelerator pedal (not shown) (hereinafter referred to as the throttle opening degree). Based on the above, a predetermined gear is read from the map as shown in FIG. 6, and when the upshift line indicated by the solid line or the downshift line indicated by the broken line is crossed in the figure, the frictional engagement element on the engagement side is The hydraulic control valve of the hydraulic control device is driven at a preset duty ratio so that a preset engagement hydraulic pressure is supplied to perform a predetermined gear shift operation.

[0011]

A diagram in which a plurality of shift speeds are achieved by electronically controlling the hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage these friction engagement elements. In the conventional automatic transmission shown in FIGS. 4 to 6, for example, the vehicle speed is medium to low and the throttle opening is small, for example, while the vehicle is traveling at the fourth speed gear indicated by point A in FIG. When the driver depresses to shift the throttle opening to the open side of the point B in FIG. 6, it becomes necessary to downshift to the first gear.

By such a kick down operation,
When a large downshift of three or more gears, such as a downshift from the 4th speed to the 1st speed, is performed, the engine rotation speed becomes 4
Since the engine speed also suddenly rises from 000 rpm to 5000 rpm, the passenger may misunderstand that the engine is in an idling state or a runaway state, which may lead to a significant deterioration in riding feeling.

Such a phenomenon is caused by 5th speed to 2nd speed or 1st speed.
This is also present in vehicles equipped with an automatic transmission with five forward gears that can be downshifted to high speed, and also in vehicles equipped with an automatic transmission that allows manual gear changeover to be selected. Occur.

That is, while the 5th or 4th speed is selected, the select lever of the transmission is operated to forcibly select the 5th to 2nd or 1st speed.
When the first speed is selected from the first speed, the engine rotation speed rapidly increases from 4000 rpm to 5000 rpm all at once. As a result, similarly to the case described above, the occupant misunderstands that the engine is in the idling state. This will lead to a marked deterioration of the ride feeling.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to automatically control the hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage these friction engagement elements to achieve a plurality of shift speeds. It is an object of the present invention to provide a shift control method capable of preventing deterioration of riding feeling due to a sudden downshift of three or more gears in a transmission.

[0016]

A shift control method for an automatic transmission according to the present invention comprises electronically controlling hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage the friction engagement elements. In an automatic transmission that achieves multiple shift speeds, if a downshift of three or more gears from a high-speed gearshift to a low-speed gearshift is required, this downshift is performed by two gearshifts. It is characterized by having been regulated by.

[0017]

[Function] When a situation in which a downshift of three or more gears from a high-speed gear stage to a low-speed gear stage is required due to kick-down operation or manual operation, this downshift operation is restricted to two gears. To be done. In other words, from 5th to 2
Downshift operation is performed from 5th to 3rd, or from 4th to 2nd, even if a downshift from 1st to 1st or 4th to 1st is required. , The engine speed does not suddenly increase.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the shift control method for an automatic transmission according to the present invention is applied to a vehicle equipped with an automatic four-forward transmission shown in FIGS. 4 to 6 will be described below.

In the present embodiment, an arbitrary shift speed can be manually selected by operating the select lever and the overdrive switch. In such a manual mode, the shift position is changed from the 4th speed to the 1st speed. When switched,
Instead of shifting from the 4th speed to the 1st speed, the shift is restricted to a downshift from the 4th speed to the 2nd speed to prevent a significant deterioration in the riding feeling due to a sharp increase in the engine speed.

Therefore, as shown in FIG. 1 showing the control block of the present embodiment, the position of the select lever (not shown) of the automatic transmission is detected to detect the gear position selected in the manual mode described above. Although the inhibitor switch 37 is provided, the fourth gear is detected based on the signal from the overdrive switch 38.

Further, in order to automatically perform the shift operation of the automatic transmission on the basis of the vehicle speed and the throttle opening, the transmission case 18 is provided with an input shaft rotational speed sensor 39 for detecting the rotational speed of the kickdown drum 34. An output shaft rotation speed sensor 40 for detecting the rotation speed of the transmission output shaft 33 is provided, and a throttle opening sensor 41 for detecting the opening of a throttle valve (not shown) is provided.

Then, in the automatic mode, the gear position is set to 4
When it is necessary to switch from the first speed to the first speed, the shift is restricted to the downshift from the fourth speed to the second speed without changing the speed from the fourth speed to the first speed as it is, and the ride feeling due to the rapid increase in the engine rotation speed is suppressed. We are trying to prevent significant deterioration.

That is, the inhibitor switch 37, the overdrive switch 38, and the input shaft rotation speed sensor 3
9 and the detection signals from the output shaft rotation speed sensor 40 and the throttle opening sensor 41 are output to an electronic control unit 42 that controls the operating state of the engine 11, and this electronic control unit 42 determines the gear position of the automatic transmission. Even if the vehicle speed and throttle opening are calculated and a downshift from the 4th speed to the 1st speed is required, the downshift up to the 2nd speed is forcibly restricted and the shift to the 2nd speed is completed. Unless there is a change in the control condition that allows the downshift to the first speed later, the operation of the hydraulic control device 43 of the automatic transmission is controlled so as to maintain the second speed.

As shown in FIG. 2 and FIG. 3 showing the flow of control according to the present embodiment, first, at S1, based on the detection signals from the input shaft rotational speed sensor 39 and the output shaft rotational speed sensor 40, the present Then, the throttle opening is calculated based on the detection signal from the throttle opening sensor 41 in S2. Then, in S3, the vehicle speed is calculated based on the detection signal from the output shaft rotation speed sensor 40, and in the step of S4, the manual mode is selected based on the signals from the inhibitor switch 37 and the overdrive switch 38. Detects the gear position desired by the driver.

After that, whether or not the downshift from the 4th speed to the 1st speed is required in S5, that is, the current shift speed detected in the step of S1 is the 4th speed, and S2 and S3. Whether the shift speed read from the shift map as shown in FIG. 6 is the first speed based on the throttle opening and the vehicle speed detected in step 1, or the first speed gear is selected in the manual mode. Is determined.

In the step S5, the downshift from the 4th speed to the 1st speed is required, that is, the current shift speed is the 4th speed, and the shift speed read from the shift map as shown in FIG. Is determined to be the first speed, or if the first speed is selected in the manual mode, the electronic control unit 42 is operated to downshift to the second speed in S6. Controls the operation of the hydraulic control device 43.

Then, in S7, the throttle opening is calculated again based on the detection signal from the throttle opening sensor 41, and in S8, the vehicle speed is calculated based on the detection signal from the output shaft rotation speed sensor 40. , S9, it is determined whether the upshift line shown by the solid line in the shift map shown in FIG. 6 has been crossed.

If it is determined in step S9 that the operating condition of the vehicle has crossed the upshift line shown by the solid line in the shift map shown in FIG. 6, that is, the shift control condition has changed, the process in step S4 is executed. When the manual mode selected in step is selected, the gear position desired by the driver is set, or when the manual mode is not selected, the throttle opening and the vehicle speed detected in steps S7 and S8 are set. Based on the shift map shown in FIG. 6, the electronic control unit 42 controls the operation of the hydraulic control device 43 in S10 so that the shift speed is set to the gear shift stage.

When it is determined in step S9 that the vehicle operating condition does not cross the upshift line shown by the solid line in the shift map shown in FIG. 6, that is, the shift control condition has not changed, When the manual mode is selected based on the signals from the inhibitor switch 37 and the overdrive switch 38 in S11, the gear position desired by the driver is changed from the desired gear position detected in the step S4. It is determined whether or not there is.

If it is determined in step S11 that the gear position desired by the driver has changed from the desired gear position detected in step S4, that is, if the shift control condition has changed, The electronic control unit 42 controls the operation of the hydraulic control device 43 so that the newly selected driver reaches the desired gear position when the manual mode is selected in step S10.

If it is determined in step S11 that the gear position desired by the driver is the same as the desired gear position detected in step S4, that is, if the gear shift control condition has not changed. Moves to step S6 and 2
The speed change state is maintained as it is.

It should be noted that in the step S5, the speed is changed from the 4th speed to the 1st speed.
Whether or not it is determined that the downshift to the high speed is not necessary, that is, even if the current shift speed is the fourth speed, the shift speed read from the shift map as shown in FIG. 6 is other than the first speed,
If it is determined that the current gear is other than the fourth gear, or if it is determined that the gear other than the first gear is selected in the manual mode even if the current gear is the fourth gear, Since it is not a downshift of more than one gear, the shift operation is performed as it is and the process proceeds to step S2.

In this embodiment, the vehicle equipped with the automatic four-forward transmission is explained. However, the control method of the present invention can be applied to the vehicle equipped with the automatic five-forward transmission. In this case, the shift operation from the 5th speed to the 2nd speed, the 5th speed to the 1st speed, and the 4th speed to the 1st speed, which are downshifts of three or more steps, is prohibited, and the shift operation is changed from the 5th speed to the 3rd speed. Restricted to downshifts up to two speeds such as 4th or 4th speed.

[0034]

According to the shift control method for an automatic transmission of the present invention, when a downshift of three or more gears from a high-speed gear stage to a low-speed gear stage is required, this downshift is performed. Since it is regulated to two stages, there is no significant sudden increase in engine speed that would be mistaken for the engine being in the idling state or runaway state as in the past, and the riding feeling accompanying the downshift is eliminated. It can be held well.

[Brief description of drawings]

FIG. 1 is a control block diagram of an embodiment capable of realizing a shift control method for an automatic transmission according to the present invention.

FIG. 2 is a flowchart showing a control flow of an embodiment of a shift control method for an automatic transmission according to the present invention together with FIG.

FIG. 3 is a flowchart showing a control flow of an embodiment of a shift control method for an automatic transmission according to the present invention together with FIG.

FIG. 4 is a skeleton diagram showing a schematic structure of a forward four-speed automatic transmission.

FIG. 5 is an operation element diagram showing a relationship between an engagement state of each friction engagement element and a shift speed.

FIG. 6 is a shift map showing a setting region of each shift speed set corresponding to a vehicle speed and a throttle opening.

[Explanation of symbols]

11 is an engine, 13 is a torque converter, 15 is a turbine, 19 is a transmission input shaft, 20 is a front clutch, 2
1 is a rear clutch, 22 is a 4-speed clutch, 23 is a kick down brake, 24 is a low reverse brake, 26 is a Ravigneaux type planetary gear mechanism, 33 is a transmission output shaft, 36 is an oil pump, 37 is an inhibitor switch, and 38 is Overdrive switch, 39 is input shaft rotation speed sensor, 40
Is an output shaft rotation speed sensor, 41 is a throttle opening sensor, 42 is an electronic control unit, and 43 is a hydraulic control device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F16H 59:68 8207-3J

Claims (1)

[Claims] 1. An automatic transmission configured to achieve a plurality of shift stages by electronically controlling hydraulic pressures supplied to a plurality of friction engagement elements to selectively engage these friction engagement elements, In a situation where a downshift of three or more gears from a high-speed gear stage to a low-speed gear stage is required, this downshift is restricted to two gears. Shift control method.