JP3185550B2 - Control device for automatic transmission for vehicle on downhill road - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for an automatic transmission for a vehicle on a downhill road.

[0002]

2. Description of the Related Art In an automatic transmission for a vehicle, generally,
A shift map is provided which uses vehicle speed and engine load (throttle opening and the like) as parameters, and information on the vehicle speed and engine load at that time during running is applied to this shift map to determine a shift speed to be selected. .

[0003] However, since this shift map is created on the basis of a general level terrain running state, for example, when traveling on a downhill road or an uphill road, it does not always provide an optimum shift speed.

In view of such circumstances, for example, Japanese Patent Publication No. Sho 59
Japanese Patent No. 8698 proposes a technique in which shift maps are separately provided according to the state of a traveling road such as for traveling on a flat road or traveling on an uphill road, and these are appropriately switched and used.

In Japanese Patent Publication No. 59-8698, a reference vehicle acceleration (expected value of running acceleration) on a flat road is obtained in advance by using a throttle opening, a vehicle speed, and the like as parameters. Also disclosed is a technique for comparing the calculated actual vehicle acceleration with the calculated actual vehicle acceleration to determine that the vehicle is traveling on a downhill if the actual acceleration is larger than a reference acceleration by a predetermined value or more, and that the vehicle is traveling on an uphill if the actual acceleration is smaller than the reference acceleration. Have been.

Further, in Japanese Patent Application Laid-Open No. Hei 5-71623, the engine braking force is reduced when it is determined that the vehicle is going downhill, the accelerator is released, and the foot brake is operated. There is disclosed a technique for switching a shift map so that a downshift can be performed to increase the shift map.

[0007]

However, in the conventional example disclosed in Japanese Patent Application Laid-Open No. Hei 5-71623, the condition for downshifting to a low speed stage is determined to be a downhill road as described above with respect to control on a downhill road. , The accelerator is released, and the brake is operated, so if the running condition meets these three conditions, the gear shifts down to the lower gear,
If at least one of them does not match, there is a problem that the downshift is not performed. Therefore, there has been a problem that the downshift by the control may not always match the actual driver's downshift request.

[0008] For example, if the gradient which is a threshold value for determining whether the vehicle is on a downhill road is set to a small value (slowly), the downshift is performed until the downshift is not necessary. The fuel economy deteriorates accordingly, and the noise also increases. Conversely, if the threshold gradient is set to a large value (tight), when the engine brake is really needed, for example, while the driver is stepping on the accelerator until then,
Even if you think that it is too fast at this speed and release the accelerator and operate the foot brake, unless the road is on a large slope that is judged to be "downhill",
It will not enter the downshift control.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and does not require unnecessary downshift control on downhill roads. It is an object of the present invention to provide a control device for a vehicle automatic transmission on a downhill road capable of entering a downshift control even when the vehicle is traveling on a downhill road with a small gradient.

[0010]

According to the present invention, as shown in FIG. 1, the gist thereof is based on a preset basic shift map.
Executing a shift control Te, but in downhill running, when the accelerator <br/> solution Ho且 one foot brake operation is determined the
Forced to low speed regardless of shift control according to basic shift map
Shifting down, a descending control system for an automatic transmission for a vehicle in slope, means for determining descending a slope or running a first road gradient as a threshold, than the first road gradient Means for determining whether or not the vehicle is traveling on a downhill road with a small second road surface gradient as a threshold value, means for determining whether or not a predetermined time has elapsed since the accelerator was released, and Means for forcibly downshifting to a low speed stage when it is determined that the vehicle is traveling on a downhill road with a threshold value and when accelerator release and foot brake operation are detected; Means for forcibly downshifting to a lower gear when it is determined that the vehicle is traveling on a hill, and when it is detected that the accelerator is released and a foot brake operation is performed within the predetermined time after the accelerator is released, Up Problems are those that were resolved.

[0011]

According to the present invention, two types of threshold values for the road surface gradient for judging a downhill road are prepared.

When it is determined that the vehicle is traveling on a descending slope having a relatively large (severe) first road surface gradient as a threshold value, when the accelerator is released and the foot brake operation is detected, the low-speed gear is conventionally used. To shift down.

On the other hand, when it is determined that the vehicle is traveling on a downhill road with the second road surface gradient smaller (slope) than the first road surface gradient as a threshold value, the foot brake is released within a predetermined time after the accelerator is released. Only when operated, will the gear shift down to the lower gear (even with a small road gradient).

That is, when the accelerator is depressed and the accelerator is released and the foot brake is operated within a predetermined time, the driver determines that the vehicle speed is too high as it is. It can be inferred that the state. In such a case, even if the slope of the downhill road is not so steep,
Downshifting to a lower gear where engine braking is more effective can achieve less uncomfortable driving.

On the other hand, according to the present invention, after a predetermined time has elapsed since the accelerator was released, the first
Since the traveling on the downhill road is determined using the (larger) road surface gradient as a threshold value, it is possible to effectively prevent the downshift by the present control from being performed more than necessary.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is an overall schematic diagram of a vehicle automatic transmission (and engine) to which the present invention is applied.

This automatic transmission 2 includes a torque converter section 20, an overdrive mechanism section 40, and an underdrive mechanism section 60 having three forward stages and one reverse stage.

The torque converter section 20 includes a pump 2
1, a turbine 22, a stator 23, and a lock-up clutch 24. The output of the crankshaft 10 of the engine 1 is
Transmit to 0.

The overdrive mechanism 40 includes a sun gear 43, a ring gear 44, a planetary pinion 42,
And a set of planetary gear units consisting of
The rotational state of the planetary gear unit is controlled by a clutch C0, a brake B0, and a one-way clutch F0.

The underdrive mechanism 60 includes two sets of planetary gear units including a common sun gear 61, ring gears 62 and 63, planetary pinions 64 and 65, and carriers 66 and 67. Rotation state, the overdrive mechanism 40 and the output shaft 70
To the clutch C1, C2, brake B1 ~
It is controlled by B3 and one-way clutches F1, F2.

Computer 84 for controlling automatic transmission 2
The throttle sensor 80 detects a throttle opening to reflect the load of the engine 1 or the accelerator opening, a vehicle speed sensor (rotation speed sensor of the output shaft 70) 82 detects a vehicle speed, a parking range, a drive range, and L
A shift position switch 86 that outputs a signal of a shift position selected by a driver such as a range, a foot brake switch 88 that outputs a signal when a foot brake is depressed, and an engine speed sensor 90 that detects an engine speed. , An idle contact switch 92 that outputs the state of the idle contact (on when the accelerator is released, off when the pedal is depressed), selects whether to drive with emphasis on power performance (power pattern) or on fuel efficiency (normal pattern) Pattern select switch 94, a cruise control switch 97 for realizing cruise control (automatic constant vehicle speed running), an overdrive off switch 97 for prohibiting running in overdrive (fourth speed), and the like. Signal is input.

The information from the vehicle speed sensor 82 is also used to determine the actual running acceleration of the vehicle.

The computer 84 first obtains a gear position to be selected according to a preset (similar to the conventional) basic map of throttle opening-vehicle speed using input signals from the respective sensors, switches and the like as parameters. Then, the solenoid valves S 1, S 2, S 3, S 4, etc. in the hydraulic control circuit 98 are driven and controlled so as to achieve the gear stage. As a result, as shown in FIG. 3, the clutches, brakes, and the like are engaged or disengaged, and the four forward speeds (the fourth speed is overdrive) and one reverse speed are achieved.

Here, the computer 84 is shown in FIGS.
According to the control flow as shown in FIG. 6, special control on an uphill or downhill is performed according to the traveling state.

FIG. 4 shows a schematic flow of the special control on this uphill road.

In order to facilitate understanding of the control flow, an outline of this special control will be described first.

<Control on Uphill Road> When it is determined that the vehicle is traveling on an uphill road, it is prohibited to shift down to third speed and then upshift to fourth speed under predetermined conditions. (Even if it is determined on the basic shift map that the upshift should be performed to the fourth speed), the third speed is held.
The main purpose is to secure the power performance and prevent the busy shift.

On an uphill road, the forced downshift from the fourth speed to the third speed is not performed. That is, only when it is determined on the basic shift map that the gear should be shifted down from the fourth gear to the third gear, the gear is shifted down in synchronization with the shift. The reason for this is that if the driver shifts down at an unexpected time while the accelerator pedal is being depressed, the driver may feel uncomfortable.

<Control on a Downhill Road> In the control on a downhill road, two types of thresholds of a relatively large first gradient and a second gradient that is smaller than the first gradient are prepared for the threshold value of the road surface gradient to be determined as "downhill".

When it is determined that the vehicle is going downhill with the first gradient as a threshold value, the following control is executed.

That is, when the vehicle is traveling at the fourth speed, the shift from the fourth speed to the third speed is performed under the conditions of accelerator release and foot brake on. This is a forced downshift that is not synchronized with the shift determination on the basic shift map, but does not give the driver a sense of incongruity because the foot brake is on.

When the vehicle is traveling in the third speed, the vehicle is shifted up to the fourth speed as long as the conditions of the downhill road with a gradient greater than the first gradient, the accelerator release, and the foot brake on condition are maintained. The third gear is held (even if it is determined on the basic shift map that the gear should be shifted up to the fourth gear). Since the first gradient is set to be relatively large, the frequency at which the control relating to the first gradient is executed is reduced as compared with the related art.

On the other hand, the control of the downhill road according to the second gradient is executed as follows.

That is, when the accelerator is depressed, the fourth
If the accelerator is released and the foot brake is operated within a predetermined time from the accelerator release while traveling at the speed,
Assuming that the driver intends to decelerate (even if the gradient is gentle), the driver is forcibly downshifted to the third speed where the engine brake is stronger.

By the way, in the control flow described later, the determination of the downhill road with the second gradient as the threshold is performed only when the vehicle is running at the fourth speed with the accelerator pedal depressed. One of the reasons is that it may not be possible to start the determination of a downhill road after the accelerator is released due to the nature of the condition, and the other is that the vehicle is driven at the fourth speed when the accelerator is depressed. This is because the control (shift down) according to the second gradient is executed only when the control is performed. That is, when the vehicle is traveling at the third speed when the accelerator is depressed and the upshift to the fourth speed is performed with the release of the accelerator, it is possible to return to the third speed again by the control relating to the second gradient. do not do.

The reason is that the control according to the second gradient is executed to shift down again to the third speed until the gear is shifted up to the fourth speed with the release of the accelerator. Thus, when the driver repeatedly depresses, releases, and operates the foot brake on a gentle downhill road, the shift is executed very frequently, and the time required to travel in the third speed (low speed) is accordingly increased. This is because the fuel consumption becomes longer than necessary and the fuel efficiency deteriorates.

Accordingly, for the same purpose, in the case of the control of the downhill road with the second gradient as the threshold value, the control of holding at the third speed is not executed. Therefore, the upshift from the third speed to the fourth speed is freely performed in accordance with the switching in the basic shift map.

Hereinafter, a control flow for executing the above-described ascending and descending slope control will be described with reference to FIG.

When this control flow starts, first,
In step 102, it is determined whether or not a precondition for executing the uphill / downhill control is satisfied.

The prerequisites are, specifically, 1) that the vehicle speed sensor 82 of the automatic transmission is normal, 2) that the shift position switch 86 is in the drive range, 3) the third speed, Or that any one of the fourth gear is outputting. 4) The vehicle speed is equal to or higher than a predetermined value and equal to or lower than a predetermined value, for example, 1
5) The vehicle is in the range of 5 km / h to 125 km / h. 5) The overdrive off switch 97 is off (inactive), that is, the overdrive (fourth speed) is in a state where it can be permitted. 6) The cruise control switch 96 is turned off, specifically, the cruise non-control state is continuously detected for a predetermined time T1 or more.

If any one of these conditions is not satisfied, the routine proceeds to step 124, where each flag is reset to zero. As a result, the control flow of FIG. 4 is substantially ended.

It is to be noted that the condition that the vehicle speed sensor 82 of the automatic transmission is normal in 1) is that if the vehicle speed sensor 82 has failed, the vehicle must go up or down the slope in order to execute this control. This is because the determination itself cannot be made.

In 2) and 3), the third drive range
The condition that one of the speed stage and the fourth speed stage is being output is a condition that this control is executed only for the hold or downshift in the third speed stage and the fourth speed stage of the drive range. That's why.

The condition that the vehicle speed is within the predetermined value in 4) is based on the condition that when the vehicle speed is equal to or lower than the predetermined value (out of the applicable range of the present control), the second speed stage or the first speed stage is set. This is because when the vehicle speed is equal to or higher than a predetermined value, the vehicle should be maintained at the fourth speed to prevent engine overrun.

In 5), the condition that the overdrive off switch is in the non-operating state is set as a condition that the driver is intentionally avoided from traveling in the overdrive (fourth speed), and this condition is not applied. This is because there is no room for executing hold and downshift at the third speed and the fourth speed by control.

The condition that the cruise control is not operated in 6) is based on the condition that, when the cruise control is executed, the gear position is determined by a separate routine in order to keep the vehicle speed constant. Is automatically controlled.

If it is determined in step 102 that all the preconditions are satisfied, the flow proceeds to step 104. In step 104, first, it is determined whether or not a condition for determining an uphill road is satisfied. In this case, a slight hysteresis is provided between when a non-uphill road is determined to be an uphill road and when an uphill road is determined to be a non-uphill road.

More specifically, MOBG ≦ SBG43-KD
When it is determined that the GSF has been established for the predetermined time T2 or longer, it is determined that the vehicle has approached an uphill road from a non-uphill road. On the other hand, MOBG> SBG43−KDGSN is equal to the predetermined time T3.
When it is determined that the above has been established, it is determined that the vehicle has shifted from the uphill road to the non-uphill road.

Here, MOBG indicates the actual acceleration of the vehicle calculated from the output of the vehicle speed sensor (the rotational speed sensor of the output shaft 70 of the automatic transmission) 82, and the SBG 43 indicates the speed of each shift using the throttle opening and the vehicle speed as parameters. Gear (third gear,
The reference vehicle acceleration when traveling on a flat road is mapped in advance for each fourth speed stage. Both may be positive or negative depending on the condition. KDGSF is a predetermined value (positive only) mapped in advance so as to be constant up to the middle vehicle speed and large at a high vehicle speed depending on the vehicle speed, and KDGSN is a select pattern (power pattern, normal pattern) by the pattern select switch 94. ) Is a predetermined value (positive only) mapped in advance so as to increase at a high vehicle speed depending on the vehicle speed.

When the vehicle speed (output shaft rotation speed) is the same, KDGSF> KDGSN (normal)> KDGSN
(Power). The reason why KDGSF is set to be larger than KDGSN is to give hysteresis to the determination, and KDGSF is set to be larger than KDGSN (power).
The reason that the DGSN (normal) is set larger is that it is more difficult to determine that the vehicle has shifted from the uphill road to the non-uphill road in the power pattern than in the normal pattern. In order to keep the state longer. If the third gear is maintained for a longer time, the fuel economy will slightly decrease, but the busy shift will be prevented and the acceleration and the effectiveness of the engine brake will be improved by that much, so that the traveling sensitive to the movement of the accelerator pedal can be performed accordingly. .

When it is determined that the road is an uphill road, the process proceeds to step 106, where the uphill road determination flag F0 is set to 1. On the other hand, when it is determined that the road is not an uphill road, the flow proceeds to step 108. Proceed to the flag F0
Is reset to zero.

In step 110, it is determined whether or not the vehicle is on a downhill road. If it is determined in step 106 that the road is an uphill road, step 110 is bypassed because it is not necessary to determine a downhill road.

The determination of the downhill road is executed in accordance with a control flow as shown in FIG.

That is, when the uphill determination flag F0 is reset to zero in step 108, the flow proceeds to step 1.
The process proceeds to step 10, and in step 200, it is determined whether the idle contact switch 92 is on, that is, whether the accelerator is released.

If it is determined that the idle contact is on, the flow proceeds to step 202 where the SBGE 43 map is searched. The SBGE 43 is a gear stage (third gear).
(First speed, fourth speed), reference vehicle acceleration for downhill road (positive / negative) mapped in advance based on the first road surface gradient (first gradient) depending on the vehicle speed for each select pattern.
That is.

In step 204, it is determined whether the fuel cut (F / C) control of the engine is in operation. If the fuel cut control is in operation, step 2
Go to 06 and reference vehicle acceleration SBGE4 (on map)
A value obtained by subtracting a predetermined value (positive) from 3 is newly defined as a reference vehicle acceleration SBGE43 used in this control. This is because, when the fuel cut control is being performed, the engine brake is more effective, and it is estimated that the actual acceleration of the vehicle is correspondingly reduced.

At step 208, it is determined whether the first downhill road determination flag F1 is zero. If the first downhill road determination flag F1 is 1, that is, if it has been determined that the road is a downhill road having the first slope or more, step 21 is executed.
The actual acceleration MOBG of the vehicle calculated from the output of the vehicle speed sensor 82 proceeds to step 2, and the reference vehicle acceleration SBG for the downhill road relating to the first gradient obtained in step 202 (or 206).
It is determined whether it is shorter than E43 by a predetermined time T4 or more. If it is not smaller, the first downhill road determination flag F
The process proceeds to step 116, but if it is smaller, the process proceeds to step 114, where the first downhill road determination flag F1 is reset to zero, and then proceeds to step 116.

In step 208, the first downhill road determination flag F
When it is determined that 1 is zero, the routine proceeds to step 210, where the actual vehicle acceleration MOBG is set to the reference vehicle acceleration SBGE.
It is determined whether the value is larger than the predetermined time T5 by more than a predetermined time T5. If the value is larger than the predetermined time T5, the first downhill road determination flag F1 is set to 1 in step 112;
Proceed to 6.

According to the above control flow, the determination of the downhill road with the first gradient as the threshold is executed.

On the other hand, if it is determined in step 200 that the idle contact is not on, that is, if it is determined that the accelerator pedal is being depressed, the routine proceeds to step 214, where it is determined whether the current actual gear is the fourth gear. Is determined.
If it is the fourth speed, the program proceeds to step 216, where KD
The EG map is searched. This KDEG is a predetermined value (acceleration: positive only) which is set higher depending on the vehicle speed (output shaft rotation speed) when the vehicle speed is in the high vehicle speed region and in the low vehicle speed region than in the middle vehicle speed region. And, as a result, a second road surface gradient (second
(Gradient).

In step 218, it is determined whether or not the road is determined to be a downhill road when the second gradient is set as a threshold value, that is, whether the value of the second downhill road determination flag F10 should be zero or one. You. Specifically, when the value of the flag F10 is currently zero, MOBG> SBG43 + KDEG + KD
If GE is not less than the predetermined time T6, the process proceeds to step 220.
The flag F10 is set to 1. When the current flag F10 is 1, MOBG ≦ SBG43 + KD
When the EG is equal to or longer than the predetermined time T7, step 222 is executed.
The flag F10 is reset to zero. Where SBG
As described above, reference numeral 43 denotes a reference vehicle acceleration on a flat road (and for an uphill road) constituted by parameters of both the throttle opening and the vehicle speed, and KDGE is a predetermined value (only positive) for giving hysteresis. is there.

On the other hand, if it is determined in step 214 that the current speed is not the fourth speed, that is, it is the third speed, the process proceeds directly to step 222, where the second downhill road determination flag F10 is set to zero. Is reset to

The first in step 110
The processing of the downhill road determination flag F1 is always reset to zero when it is determined that the idle contact is off (regardless of the value of the second downhill road determination flag F10).

The reason why the determination of the downhill road relating to the second gradient is performed only when the idle contact is off and the vehicle is running at the fourth speed is as described above.

Returning to FIG. 4, step 1 is thus performed.
When it reaches 16, it is determined here whether the climbing control start condition is satisfied. Specifically, 1) the foot brake switch 88 is off (the brake is not depressed), 2) the idle contact switch 92 is off (the accelerator is depressed), and 3) the third speed based on the basic shift map. The power-on downshift (downshift when the accelerator is depressed) is satisfied, or one of the outputs of the third speed stage after the determination is satisfied is satisfied. 4) The condition that the uphill road determination flag F0 is 1 When all of the conditions have been satisfied, it is determined that the ascending control start condition has been satisfied, and the routine proceeds to step 118, where the fourth speed position inhibition request flag F2 for the ascending road is set to 1. If any of the conditions 1) to 4), which are the conditions for starting the hill-climbing control, are not satisfied, step 118 is bypassed.

In the above 3), the determination of the power-on downshift to the third speed or the output of the third speed based on the basic shift map is one of the conditions for starting the uphill control, as described above. While the vehicle is traveling in the speed range, the control is executed (when the driver does not intend) to change from the fourth speed stage to the third speed stage.
This is to prevent a downshift to the first gear. That is, in the uphill control, the downshift from the fourth speed to the third speed is not actively performed, and only the upshift from the third speed to the fourth speed is prevented.

On the other hand, at step 120, it is determined whether or not the condition for starting downhill control is satisfied. FIG. 6 shows a specific control flow of step 120.

That is, first, at step 300, it is determined whether or not the idle contact switch 92 is on.
When the idle contact switch 92 is not on, that is, when the accelerator is being depressed, the routine proceeds to step 301, where the value of the elapsed time t is reset to zero.

In step 300, the idle contact switch 9
When 2 changes from off to on, substantial counting up of the elapsed time t 1 is started, and it is determined in step 302 whether or not the elapsed time t 1 since the idle contact switch 92 was turned on is smaller than a predetermined time t0. You. Since it is initially determined to be small, the flow proceeds to step 304, where it is determined whether the second downhill road determination flag F10 set in step 220 or 222 described above is 1. When the flag F10 is 1, the routine proceeds to step 306, where it is determined whether or not the foot brake switch 88 is turned on, that is, whether or not the foot brake is depressed. Flag F
When 10 is zero, the process once proceeds to step 312 to check the value of the first downhill determination flag F1, and only when F1 = 1, proceeds to step 306 to determine whether or not the foot brake is depressed. Is determined. When the foot brake is depressed, at step 122 the fourth
The gear inhibition request flag F3 is set to 1.

When it is determined that the elapsed time t after the idle contact is turned on has reached the predetermined time t0, the routine proceeds to step 310, where the second downhill road determination flag F10 is determined.
Is reset to zero.

When it is determined in step 306 that the foot brake has not been depressed, the fourth-speed-gear prohibition request flag F3 for a downhill road is not set to 1 at any time.

Returning to the control flow of FIG.

When the process reaches step 126 in this way,
Thereafter, actual processing is performed based on the value of each flag.
First, at step 126, it is determined whether or not the uphill determination flag F0 is zero. In step 128, it is determined whether the fourth-speed-gear prohibition request flag F2 for the uphill road is "1".

If it is determined that the fourth-speed-gear prohibition request flag F2 for the uphill road is 1 even though the uphill road determination flag F0 is zero, the routine proceeds to step 130, where it is reset at a predetermined time. It is determined whether or not the uphill control return timer to be counted up has expired. If it has been completed, the fourth-speed uphill prohibition request flag F2 for ascending is reset to zero in step 132, but if it has not been completed, the process proceeds to step 142, where the fourth-speed upright prohibition request flag F2 for ascending is reset. The value is checked, and if the value is 1, the fourth speed is prohibited in step 146.

On the other hand, when it is determined that the uphill determination flag F0 is not zero, or even when it is determined that the flag F0 is zero, it is determined that the fourth speed position inhibition request flag F2 for the uphill is not 1. If so, the process proceeds to step 134.

In step 134, the value of the first downhill road determination flag F1 is determined. In step 136, it is determined whether or not the fourth-speed-gear prohibition request flag F3 for the downhill road is "1". When it is determined that the fourth-speed-stage-prohibition request flag F3 for the downhill road is 1 even though the first downhill-road determination flag F1 is zero, the routine proceeds to step 138, where the countdown is reset and counted up from a predetermined time. It is determined whether or not the descending slope control return timer has expired, and if so, in step 140, the fourth-speed-stage-prohibition request flag F3 for the descending slope is reset to zero.

However, the first downhill road determination flag F1
Is not zero, or even if it is zero, the fourth
If the gear-stage prohibition request flag F3 is not 1 or if it is determined that the downhill control return timer has not expired, the routine proceeds to step 142 (144), where the fourth speed for uphill or downhill roads is entered. If one of the gear inhibition request flags F2 and F3 is 1, the fourth gear is inhibited in step 146. If both are zero, the control flow ends without prohibiting the fourth speed.

By the control flow as described above, the control of the ascending / descending road as described above is realized before the concrete description of the control flow.

According to this embodiment, as described above, the basic threshold value for determining a downhill road can be set to a relatively large value, and as a result, the control for shifting down to a lower gear than necessary can be performed. Is prevented from being executed,
If the foot brake is operated within a predetermined time from the time when the accelerator is released, it is considered that the driver wants rapid deceleration, and even if the vehicle is traveling on a relatively small road gradient, It is possible to surely shift down. As a result, the true deceleration request of the driver can be reflected in the shift control more than before, and the driving feeling can be improved accordingly.

In this embodiment, only the downshift from the fourth speed to the third speed is performed for the control relating to the second gradient, and the hold control for the third speed is performed according to the second gradient. Although this is not performed, the present invention does not prohibit the control related to the second gradient from performing the hold control of the third speed.

[0082]

As described above, according to the present invention, it is possible to prevent the "downshift control on a downhill road" from being performed more than necessary, and to prevent the driver from suddenly decelerating. Even when it is determined that the vehicle is traveling on a relatively gentle road gradient, "shift down control on a downhill road" is executed, so that both improvement in fuel efficiency and reflection of a driver's deceleration request can be achieved. become.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a skeleton diagram of an automatic transmission for a vehicle to which the present invention is applied;

FIG. 3 is a diagram showing an operation state of the friction engagement device of the automatic transmission.

FIG. 4 is a flowchart showing a control flow executed in the embodiment.

FIG. 5 is a flowchart showing details of step 110 in FIG. 4;

FIG. 6 is a flowchart showing details of step 120 in FIG. 4;

[Explanation of symbols]

 80 ... Throttle sensor 82 ... Vehicle speed sensor (output shaft speed sensor) 84 ... Computer 86 ... Shift position switch 88 ... Foot brake switch 92 ... Idle contact switch 94 ... Pattern select switch MOGB ... Real vehicle acceleration SGB43 ... (on a flat road) ) Reference vehicle acceleration SBGE43 ... Reference vehicle acceleration (on a downhill road)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshiharu Harada 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-5-71623 (JP, A) JP-A-5-106714 (JP, A) JP-A-5-340469 (JP, A) JP-A-5-231522 (JP, A) JP-A-2-102059 (JP, U) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) F16H 61/00-61/24

Claims (1)

(57) [Claims] 1. According to a preset basic shift map.
It executes the shift control during the downhill running, the accelerator solution
Said groups when Ho且 one foot brake operation is detected
Forcibly <br/> downshifting regardless low speed stage shift control according to the shift map, descending a control system for an automatic transmission for a vehicle in hill, traveling downhill road the first road gradient as the threshold Means for determining whether or not the vehicle is running, means for determining whether or not the vehicle is traveling on a downhill road using a second road surface gradient smaller than the first road surface gradient as a threshold value, and a predetermined time since the accelerator is released. Means for judging whether or not the time has elapsed; and when it is determined that the vehicle is traveling on a downhill road with the first road surface gradient as a threshold value, and when it is detected that the accelerator is released and the foot brake operation is performed, the vehicle is forcibly switched to the low speed stage . Means for shifting down to, and when it is determined that the vehicle is traveling on a downhill road with the second road surface gradient as a threshold, and when it is detected that the accelerator is released and the foot brake operation is performed within the predetermined time from the accelerator release, At low speed A control device for a vehicle automatic transmission on a downhill road, comprising: means for forcibly shifting down.