JPS621142B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of controlling an automatic transmission for a vehicle.

2. Description of the Related Art Vehicle automatic transmissions that include a gear transmission mechanism that can be switched between a plurality of gear speeds have been proposed in various configurations. Among such automatic transmissions, for example, an automatic transmission that has an overdrive stage in which the input shaft and output shaft of a gear transmission mechanism are directly connected and has a reduction ratio of 1 and an overdrive stage in which the reduction ratio is 1 or less. In this case, the engine brake acts in both the direct gear and the overdrive gear, so the accelerator pedal is released from the engine driven state of the vehicle in the overdrive gear, and the vehicle changes from the engine drive state. If a situation occurs where the gear transmission mechanism is downshifted from the overdrive gear to the direct gear as soon as the engine brake state is entered, the output shaft torque of the automatic transmission will increase from a certain positive value to a large negative value. There is a problem in that the value suddenly changes, causing discomfort to the passengers and at the same time causing a rattling sound in the vehicle's drive system.

SUMMARY OF THE INVENTION It is an object of the present invention to address the above-mentioned problems in conventional automatic transmissions and to provide a method for controlling a vehicle automatic transmission in a manner that solves the problems.

According to the present invention, such an object is achieved by switching between a plurality of gear stages including at least three gear stages, high, medium, and low, in which the reduction ratio increases sequentially from the high speed side to the low speed side. A control method for an automatic transmission for a vehicle including a gear transmission mechanism in which engine braking is applied at a gear position and engine braking is not applied at a lower gear position, and the method includes a plurality of input signals including signals relating to vehicle speed and throttle opening. Based on this, it is determined which gear speed the gear transmission mechanism should be set to at every extremely short cycle time, and when controlling the gear shift of the gear transmission mechanism according to the determination, the throttle opening is When the throttle opening is at or near zero or more, and the gear mechanism is set and operating at the higher gear position, the throttle opening suddenly decreases to or near zero, so that the gear transmission mechanism changes to the higher speed. When it is determined that a downshift should be made to the middle gear, the gear is first downshifted from the higher gear to the lower gear, and after a predetermined set time has elapsed, the gear is upshifted to the middle gear. This is achieved by a control method characterized by:

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the configuration of an apparatus for carrying out the method of controlling an automatic transmission for a vehicle according to the present invention. FIG. 1 schematically shows the configuration of an automatic transmission controlled by the control method of the present invention. This automatic transmission 1 is known per se, and includes an input shaft 2 connected to an output shaft of an engine (not shown), a hydraulic torque converter 3, and an input signal that bypasses the torque converter 3. A direct coupling clutch 4 connects the shaft 2 directly to the output shaft 3a of the torque converter, and a shaft 5 connected to the output shaft 3a of the torque converter is used as an input shaft to give several speed change characteristics to the output shaft 6 to drive the vehicle. It includes a gear transmission mechanism 7 that outputs driving force for driving the wheels.

The gear transmission mechanism 7 includes a carrier 8 connected to the input shaft 5, a planetary pinion 9 carried by the carrier, a gear 10 and a link gear 11 meshing with the planetary pinion, and a link gear 11 provided between the carrier 8 and the sun gear 10. a one-way clutch (F ₀ ) 12, a clutch (C ₀ ) 13 that selectively connects the carrier 8 and the sun gear 10, and a sun gear 10.
It has an overdrive mechanism including a brake (B ₀ ) 14 for selectively fixing the motor to the housing.

The gear transmission mechanism 7 further includes a clutch (C ₁ ) 17 and a clutch (C ₂ ) 18 that selectively connect the intermediate shaft 15 and the sun gear shaft 16 to the ring gear 11, a ring gear 19 connected to the intermediate shaft 15, and a sun gear shaft 16. Sun gear 20 and ring gear 19 connected to
A planetary pinion 22 carried by a carrier 21 meshed between and a sun gear 20 and connected to the output shaft 6, a sun gear 23 connected to the sun gear shaft 16, and a ring gear 2 connected to the output shaft 6.
4. A planetary pinion 25 meshed between the sun gear 23 and the ring gear 24, a carrier 26 supporting the planetary pinion, and a sun gear shaft 16.
a brake (B ₁ ) 27 for selectively fixing the sun gear shaft to the housing via a one-way clutch (F ₁ ) 28; a brake (B ₂ ) 29 for selectively fixing the sun gear shaft to the housing via a one-way clutch (F 1 ) 28; On the other hand, a one-way clutch (F ₂ ) 30 fixes the carrier 26 against rotation in one direction, and a brake (B ₃ ) 3 fixes the carrier 26 selectively to the housing.
1, and includes a transmission device that achieves three forward speeds and one reverse speed.

The direct coupling clutch 4 in the automatic transmission 1 and the clutch and brake in the gear transmission mechanism 7 are selectively supplied with hydraulic pressure by the automatic transmission hydraulic control device 32, or the supplied hydraulic pressure is discharged. This allows the direct coupling clutch to be selectively engaged or released, and to be set between four forward gears, including overdrive, and one reverse gear. . The automatic transmission hydraulic control device 32 is controlled by three solenoids. Of these, the solenoid
The two No. 1 and No. 2 are for controlling the gear transmission mechanism 7, and the gear transmission mechanism that is switched between four forward speeds and one reverse speed, including overdrive, by these two solenoids is the subject of the present invention. This was proposed in Japanese Patent Application No. 55-69110 filed by the same applicant. Solenoid No. 3 is for controlling the direct coupling clutch 4 between engagement and release.

When the automatic transmission hydraulic control device is controlled by a solenoid in this way, it can be controlled by a so-called computer 33, and the vehicle speed,
Based on a large number of information signals representing vehicle operating conditions such as throttle opening, manual shift range, gear position, vehicle running altitude, and engine temperature, the operating conditions that provide the vehicle's optimal operating condition are calculated, and based on that, the automatic The transmission can be controlled.

Figure 2 shows the automatic transmission shown in Figure 1.
2 is a table showing the energization and de-energization of solenoids and the engagement states of friction engagement elements such as clutches and brakes and one-way clutches at each gear stage achieved under various manual shift ranges.
In this list, manual shift range D,
3, L, R, P, and N indicate D range, 3 range, L range, reverse range, parking, and neutral, respectively, and gear stages 1st, 2nd, 3rd, O/D,
Rev indicates the first, second, third, overdrive, and reverse gear positions, respectively. Further in this list, for a solenoid, an O indicates it is energized, an X indicates it is de-energized, and an asterisk indicates that the direct coupling clutch is engaged. Indicates that it is energized at the right time. Furthermore, in the same table, frictional engagement elements are engaged only when marked with a circle, and are disengaged at other locations. Similarly, with respect to one-way clutches, these are engaged only when the engine is running at the locations marked with a triangle, and are released at other locations.

As can be understood from the comparison between Figures 1 and 2, in the gear transmission mechanism shown in Figure 1, when the shift range is set to D range, overdrive and 3rd gear are When the shift range is set to 3, the engine brake is applied, and when the shift range is set to 3, the engine brake is applied when the shift range is set to 3. However, engine braking does not work in first gear.

The gear transmission mechanism 7 and the direct coupling clutch 4 in the automatic transmission 1 are connected to a shift line and a direct coupling clutch switching line expressed by rectangular coordinates of vehicle speed and throttle opening, which are calculated based on input signals by the control computer 33. , respectively, between a plurality of gears and between engagement and disengagement. In controlling an automatic transmission using such a control computer, the shift line for changing gears and the switching line for engaging and disengaging the direct coupling clutch are normally set between the vehicle speed and the throttle opening. Set as a digital relationship. Figures 3 and 4
The figures are diagrams each showing an example of a shift line and a direct clutch switching line in the D range.

In Figure 3, solid lines 1st → 2nd, 2nd → 3rd, 3rd
→O/D is an upshift line from 1st gear to 2nd gear, from 2nd gear to 3rd gear, and from 3rd gear to overdrive, and the broken lines 1st←2nd, 2nd←
3rd and 3rd←O/D are downshift lines from 2nd gear to 1st gear, from 3rd gear to 2nd gear, and from overdrive to 3rd gear, respectively. In Figure 4, the solid line OFF→ON and the broken line OFF← belong to the 3rd.
ON is a switching line where the direct coupling clutch is switched from disengagement to engagement in the 3rd gear state, and a switching line where the direct coupling clutch is switched from engagement to disengagement in the 3rd gear state, respectively, and O/D The solid line OFF→ON and the dashed line OFF←ON are the switching lines where the direct coupling clutch switches from disengagement to engagement in the overdrive state, and the switching line where the direct coupling clutch switches from engagement to disengagement in the overdrive state, respectively. This is the switching line that can be used.

Assume that the manual shift range of the automatic transmission is currently set to the D range, and the vehicle is being driven by the engine with the gear being switched to the overdrive gear. Assume that the accelerator pedal is released from this state and the vehicle transitions from the engine drive state to the engine brake state, and at the same time, the gear position is downshifted from overdrive to third speed. This transition from engine drive to engine brake and the third from overdrive
When downshifts to higher speeds occur simultaneously or very close in time, the output shaft torque changes more rapidly from a positive value to a negative value, as shown in FIG. 5B. Fifth
In the figure, changes in engine speed and changes in servo pressure during such a transition are shown simultaneously in Figures A and C.

FIG. 6 is a flowchart illustrating how the control method according to the present invention is applied to the automatic transmission shown in FIG. 1. First, when control is initiated at the start, all values in the computer 33 are reset to their initial values. Next, data such as shift position, throttle opening, and vehicle speed are read. When data input is completed, it is determined whether the current shift range is the D range, the 3 range, or the L range.

Assume that the shift range is now set to D range. The scanning process then determines whether the gear should be changed below the D range, and when the gear should be changed, sets the gear to be changed. Once the gears have been set, the following steps will be taken:
A determination is made as to whether the condition of D ₁ is achieved.

Condition _D1 is a condition that the gear is downshifted from overdrive to third speed when the throttle opening is at or near zero. When the gear transmission mechanism is shifted in accordance with such conditions, a large sudden change in the output shaft torque from positive to negative occurs as shown in FIG. Therefore, when condition D ₁ is achieved, the next D ₁ command is issued. This _D1 command does not directly downshift the gear from overdrive to 3rd gear, but first downshifts from overdrive to 2nd gear, where engine braking does not apply, and then after a predetermined set time has elapsed. This is a command to upshift to third gear. It takes
When the gear stage is changed in accordance with the _D1 command, the output shaft torque gradually changes stepwise as shown in FIG. 7B, thereby avoiding the occurrence of a large shift shock. FIGS. 7A and 7C show changes in engine speed and servo pressure during such stepwise shifting. As can be understood from FIG. 7C, in this case, the brake _B0 is released and the clutch _C0 is engaged, thereby switching the overdrive mechanism from overdrive to direct coupling, and at the same time, the clutch _C2 is released. As a result, the gear transmission mechanism is once downshifted from the overdrive gear to the second gear, and after a predetermined set time Δt ₁ has elapsed, the clutch C ₂
is re-engaged, causing the gear transmission mechanism to move to the third position.
An upshift to speed is performed.

Returning to Figure 6 again, when the D ₁ command ends,
In the operating state at that time, it is determined whether the direct coupling clutch should be in the engaged state or in the disengaged state, and control is performed to turn the direct coupled clutch on (engaged) or off (released) accordingly. . After these scanning steps, a predetermined output command is issued and the scanning steps are returned to the point before data input. This scanning process is constantly repeated at an extremely short cycle time of about 5 msec, so that the automatic transmission is set at each moment to the optimum switching state for the vehicle's driving conditions at that moment. .

If it is determined in the shift range determination that the 3rd range is selected at that time, scanning is performed according to a scanning process similar to that in the case of the D range. However, in this case, when the gear position is set, _{the D2} determination is performed instead of the D1 determination in the case of the D range.

The _D2 determination is a determination as to whether or not the throttle opening is at or near zero and the conditions for downshifting the gear stage from the third gear to the second gear are achieved. When the shift range is set to 3 ranges, engine braking is applied in both 3rd and 2nd speeds. Therefore, in this case, when the gear shift mechanism is shifted according to the condition _D2 , the output shaft torque changes sharply from a positive value to a negative value, as in the case of a downshift according to the condition _D1 . , an undesirable shift shock occurs in the vehicle. Therefore, if the result of the D ₂ determination is yes, the D ₂ command is issued. This directive is
This is a control command to first downshift from 3rd gear to 1st gear where engine braking is not applied, and then upshift to 2nd gear after a predetermined set time has elapsed. By switching the gears in this way, the output shaft torque changes in small steps in a stepwise manner, similar to the case shown in FIG. Avoided.

The scanning process for controlling the direct coupling clutch after the _D2 command in the 3rd range is the same as in the D range.

If it is determined in the shift range determination that the L range is selected, it is determined whether or not the gear position needs to be changed, and the gear position is set accordingly. This gear position setting is to switch to the first gear regardless of the previous gear position. In the L range, the direct coupling clutch is not engaged and is always set in the released state. In the case of the 3rd range and the L range, an output command is issued at the end of the scanning process up to setting the engagement or release of the direct coupling clutch, and the scanning process is returned to before data input.

Although the present invention has been described in detail with respect to one embodiment above, the present invention is not limited to this embodiment, and various modifications can be made to this embodiment within the scope of the present invention. This will be obvious to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a vehicular automatic transmission and its control device to which the control method according to the present invention is applied, and FIG. A list showing the energized/de-energized and engaged states of the solenoid, frictional engagement device, and one-way clutch to be achieved. FIG. 3 shows an example of the shift line for the gear shifting mechanism of the automatic transmission shown in FIG. 1 in the D range. FIG. 4 is a diagram showing an example of the switching line for the direct coupling clutch of the automatic transmission shown in FIG. 1 in the case of D range, and FIG. 5 is a diagram showing the automatic transmission shown in FIG. 1. The engine rotation speed when a downshift from overdrive to third gear is performed using the conventional control method when the throttle opening is at or near zero in the machine.
Diagram showing changes in output shaft torque and servo pressure, No. 6
The figure is a flowchart showing a control mode when the control method of the present invention is implemented for the automatic transmission shown in Figure 2, and Figure 7 is a flowchart showing the control mode when the automatic transmission shown in Figure 1 is at or near zero throttle opening. FIG. 4 is a diagram showing changes that occur in engine speed, output shaft torque, and servo pressure when the control method of the present invention is implemented when downshifting from overdrive to third speed. 1-automatic transmission, 2-torque converter input shaft, 3-torque converter output shaft, 3a-torque converter, 4-direct clutch, 5-gear transmission mechanism input shaft, 6-gear transmission mechanism output shaft, 7-gear transmission mechanism, 8~carrier, 9~planetary pinion, 10~sun gear, 11~ring gear, 12~
One-way clutch, 13 - clutch, 14 - brake, 15 - intermediate shaft, 16 - sun gear shaft, 1
7, 18 ~ clutch, 19 ~ ring gear, 20 ~
Sun gear, 21~Carrier, 22~Planetary pinion, 23~Sun gear, 24~Ring gear, 2
5 ~ Planetary pinion, 26 ~ Carrier, 27
~Brake, 28~One-way clutch, 29~
Brake, 30 - One-way clutch, 31 - Brake, 32 - Automatic transmission hydraulic control device, 33 -
Control computer.

Claims (1)

[Claims] 1. Switched between a plurality of gears including at least three gears, high, medium, and low, in which the reduction ratio increases sequentially from the high speed side to the low speed side, and engine braking is applied in the middle gears, A control method for an automatic transmission for a vehicle including a gear transmission mechanism in which engine braking does not apply in the low gear position, wherein the control method is performed at every extremely short cycle time based on a plurality of input signals including signals related to vehicle speed and throttle opening. When determining which gear speed the gear transmission mechanism should be set to and controlling the gear change of the gear transmission mechanism according to the judgment, the throttle opening is at or near zero or an opening close to zero; In this case, the gear transmission mechanism is downshifted to the middle gear when the throttle opening suddenly decreases from the state in which the gear transmission is set to the high gear and is in operation to zero or near zero. When it is determined that the gear should be shifted, the high gear is first downshifted to the low gear, and after a predetermined set time has elapsed, the gear is upshifted to the middle gear. .