JP3296098B2 - 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 Laid-Open Publication No. Hei 5-71623 or Japanese Patent Laid-Open Publication No. Hei 5-71625, when the actual acceleration is larger than a reference acceleration of a flat road by a predetermined value or more, it is determined that the road is a downhill road, and the road is determined to be a downhill road. When the determination is made, a technique is disclosed in which the shift characteristic is switched to shift down to a lower gear to increase the engine braking force.

[0007]

The automatic transmission generally has a lock-up clutch, and controls the lock-up clutch to a fully engaged state, a slidingly engaged state, and a released state in accordance with an operating state. The connection state with the engine is appropriately changed. Structurally, when the lock-up clutch is engaged, the fuel efficiency is improved as compared to when the lock-up clutch is disengaged, and the engine brake is effective.

However, in the conventional control on a downhill road, the "threshold of the road surface gradient" for judging that the vehicle is traveling on a downhill road, that is, the predetermined value is determined based on whether the lock-up clutch is engaged or disengaged. The value was the same regardless of the state.

For this reason, when the threshold value of the road surface gradient for determining that the vehicle is traveling on a downhill is set to an optimum value when the lock-up clutch is released, for example, the lock-up clutch is in the engaged state (completely engaged). (Including both the state and the sliding engagement state), the engine has a considerable amount of engine braking force even at high speeds. Therefore, when downshifting is performed by executing downhill control, the downside is more prominent than the downshift. There was a problem that it might be.

In other words, for example, in a case where the lock-up clutch is engaged in the fourth speed stage and the state shifts to the lock-up release state in the third speed stage by executing downhill road control, the engine brake is increased. There is almost no effect, and not only the shift is performed (it is not necessary), but also the fuel consumption is deteriorated.

On the other hand, in the case where the shift to the state where the lock-up clutch of the third speed is engaged as a result of shifting down by executing the downhill control is performed, the engine brake is applied on many actual downhill roads. It is expected that it will be too large, and in this case (it is not necessary)
The shift is executed, and the fuel consumption is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem.
Provided is a control device for an automatic vehicle transmission on a downhill road, which can more appropriately perform control on a downhill road by considering a release state and can avoid unnecessary downshifting and prevent deterioration of fuel efficiency. The purpose is to:

[0013]

According to the present invention, there is provided a lock-up clutch, means for determining whether or not the vehicle is traveling on a downhill road having a road surface gradient equal to or greater than a predetermined value, and determining that the vehicle is traveling on the downhill road. Means for shifting to a shift characteristic suitable for a downhill road, and means for performing a shift control in accordance with the switched shift characteristic. Means for solving the above-mentioned problems, comprising: means for detecting whether the lock-up clutch is in the disengaged state, and means for setting the predetermined value to a larger value when the lock-up clutch is in the engaged state than in the disengaged state. It is.

Further, the present invention provides a means for estimating the engaged / disengaged state of the lock-up clutch after the shift characteristic has been switched, and a method for estimating the predetermined value set in the engaged state of the lock-up clutch by the estimation result. Means for increasing the value when the engaged state is estimated compared to when the disengaged state is estimated, thereby solving the above-mentioned problem.

[0015]

According to the present invention, the threshold value of the gradient (determination gradient of the downhill road: corresponding to the predetermined value) used as a reference for determining whether or not the vehicle is traveling on a downhill road is determined based on whether the lock-up clutch is engaged or released. It is changed and set depending on.

More specifically, the threshold value of the gradient is set to be larger when the lock-up clutch is in the engaged state than in the released state. As a result, when the lock-up clutch is engaged, the vehicle is determined to be “downhill” for the first time when the vehicle is traveling on a downhill with a larger (severe) road surface gradient. (Shift down control) can be prevented from being executed more than necessary.

The predetermined value (threshold of the road surface gradient) set when the lock-up clutch is in the engaged state is estimated by estimating the engaged / disengaged state of the lock-up clutch after the shift characteristic is switched (after the downshift). According to the result, when the engagement state is estimated after the switching, the value is set to a larger value than when the release state is estimated, so that the downhill road can be determined more accurately.

That is, when it is expected that the lock-up clutch will be brought into the engaged state after the shift-down, the engine braking force after the shift-down is expected to be excessive, and the road surface gradient is considerably large (severe). Unless it is a downhill road, the downside of downshifting is likely to be greater. In contrast,
If it is estimated that the lock-up clutch will be released after downshifting, an increase in engine brake can be expected (not so large), so that there is a merit of downshifting even on a gentler downhill road. it is conceivable that. Therefore, more accurate downhill road control can be realized by changing the threshold value for downhill road determination according to the estimation result of the engaged / disengaged state of the lockup clutch after downshifting.

The gradient for determining a downhill road is as follows:
As in the embodiment described later, “the expected acceleration corresponding to the gradient” may be used, and this may be used as the reference acceleration to compare the actual acceleration calculated from the output of the vehicle speed sensor or the like to determine the downhill road. Further, in the case of a vehicle equipped with a vehicle inclination angle sensor, the gradient itself may be used more directly as a threshold value. In the case of the present invention, in any case, the “gradient” itself, which is a reference for determination, is changed depending on the engagement state of the lock-up clutch.

[0020]

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.

The 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 lock-up clutch 24 is switched between an engaged state and a released state by a computer 84, which will be described later, according to a vehicle speed-throttle opening degree map in a known manner.

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.

A computer 84 for controlling the automatic transmission 2
Includes a throttle sensor 80 for detecting a throttle opening (corresponding to an accelerator opening) for reflecting the load of the engine 1, a vehicle speed sensor (a rotation speed sensor of the output shaft 70) 82 for detecting a vehicle speed, a parking range, and a drive. range,
A shift position switch 86 for outputting a signal of a shift position selected by the driver in the L range, a foot brake switch 88 for outputting a signal when a foot brake is depressed, and an engine speed sensor for detecting an engine speed. 90, an idle contact switch 92 for outputting the state of an idle contact (ON when the accelerator is released, OFF when the pedal is depressed), whether to drive with emphasis on power performance (power pattern) or on fuel efficiency (normal pattern) For various controls such as a pattern select switch 94 to be selected, a cruise control switch 97 for implementing cruise control (automatic constant vehicle speed traveling), an overdrive off switch 97 for inhibiting traveling in the overdrive (fourth speed), and the like. 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 uses the input signals from the respective sensors, switches, and the like as parameters, and firstly selects and selects the gear position to be selected according to a preset (similar to the conventional) basic map of throttle opening-vehicle speed. The engaged / released state of the lock-up clutch 24 to be operated is determined. Then, the solenoid valves S 1, S 2, S 3, S 4, etc. in the hydraulic control circuit 98 are driven and controlled so that the gear stage and the lock-up clutch are engaged / disengaged. As a result, as shown in FIG. 3, the clutches, brakes, and the like are engaged or disengaged, and the forward four speeds (the fourth speed is overdrive) and the reverse one speed are achieved, and the lock-up clutch is engaged. 24 engagement or disengagement is achieved.

Here, the computer 84 is shown in FIG.
According to a control flow as shown in FIG. 1, 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 the uphill or downhill.

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, under predetermined conditions, it is prohibited to shift down to third speed and then upshift to fourth speed. (Even if it is determined on the basic shift map that the shift up to the fourth speed should be performed), 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 executed. 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.

The return of the uphill control is performed immediately in principle when the conditions of the uphill control are not satisfied. However, when only the condition of the uphill road is not satisfied, the return is performed after a predetermined return timer has elapsed.

<Control on a Downhill Road> In the control on a downhill road, the threshold value (predetermined value) of the road surface gradient for determining that the vehicle is a "downhill road" is a relatively large first gradient and a second gradient smaller than the first gradient. Be prepared. Further, in the case of the first gradient, this is changed and set depending on the engaged / disengaged state of the lock-up clutch. That is, the lock-up clutch 2
The first gradient itself is set to be a larger value when 4 is in the engaged state than in the released state. Further, when the lock-up clutch is in the engaged state, if the shift-down is performed, the state of the lock-up clutch 24 after the down-shift should be the engaged state or the released state. It is predicted and estimated whether the state is the state, and the first gradient is set to be larger when the engagement state is estimated than when the release state is estimated.

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

That is, when the vehicle is traveling in the fourth speed, the gear is shifted down from the fourth speed to the third speed 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 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.

The first gradient is such that when the lock-up clutch 24 is released, the lock-up clutch 2
4 is engaged, but is in a state to be released when downshifting, when the lock-up clutch 24 is in engagement, and is in a state to be engaged after downshifting. Since the values are sequentially set to be larger, the frequency at which the control related to the first gradient is executed in this order is reduced.

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 a threshold is made only when the vehicle is running at the fourth speed with the accelerator depressed. One of the reasons is that it may not be possible to make a decision on 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, the second speed is established.
The control for the gradient does not return to the third speed again. The reason is that with the release of the accelerator,
If the control related to the second gradient is executed to shift down again to the third speed until such time as shifting up to the speed, the driver can depress, release, and release the accelerator on a gentle downhill road. If the brake operation is repeated,
This is because the shift is executed very frequently, and the traveling time in the third speed (low speed) is unnecessarily long, and the fuel efficiency is deteriorated.

The return of the downhill control is immediately performed in principle when the condition of the downhill control is not satisfied. However, when only the condition of the downhill road is not satisfied when other conditions are satisfied, a predetermined return is performed. This is performed after the timer elapses.

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 a condition that the vehicle speed is equal to or lower than the predetermined value (outside the applicable range of the present control). 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-operation state is set as a condition that the driver is intentionally avoided from traveling in the overdrive (fourth speed), and that the overdrive off switch is not operated. 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 being 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.

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 each speed change 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 becomes 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 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.

At 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 according to 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 roads (positive or 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 or not the lock-up clutch 24 is engaged. If the lock-up clutch 24 is in the disengaged state, the process jumps to step 208. If it is determined that the lock-up clutch 24 is in the engaged condition, the process proceeds to step 205, and if the gear is currently downshifted from the fourth speed to the third speed. It is determined whether the lock-up clutch 24 is in the running state in which the lock-up clutch 24 is to be engaged or in the released state.

When it is determined that the lock-up clutch is in a running state in which the lock-up clutch should be released after a downshift, a value obtained by adding a predetermined value 1 to the reference vehicle acceleration SBGE43 (on the map) is a reference used in this downhill control. It is newly defined as the vehicle acceleration SBGE43. When it is determined that the vehicle is in a running state in which the lock-up clutch should be engaged after downshifting, a value obtained by adding a predetermined value 2 to the reference vehicle acceleration SBGE43 (on the map) is a reference used in this downhill control. It is newly defined as the vehicle acceleration SBGE43. Here, the predetermined value 1 <the predetermined value 2.

By the operations in steps 204 to 207, the reference vehicle acceleration SBGE 43 to be compared with the actual acceleration MOBG of the vehicle is increased or decreased according to the state of the lock-up clutch 24, and as a result, it is determined that the vehicle is on a downhill road. The threshold value of the first gradient is that the lock-up clutch 24 is in the disengaged state and the lock-up clutch 24 is in the engaged state. The state corresponds to three states, that is, a running state in which the engaged state should be maintained even if the downshift is performed, and the state is changed and set from small to large.

When the lock-up clutch 24 is detected to be in the disengaged state, the engagement state after the downshift is not determined. It is usually not possible to switch to the state.

In 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.
2 and the actual acceleration MOBG of the vehicle calculated from the output of the vehicle speed sensor 82 is smaller than the reference vehicle acceleration SBGE43 for the downhill road relating to the first gradient obtained in step 202 (or 206 or 207) by a predetermined time T4 or more. Is determined. If it is not smaller, the process proceeds to step 116 as it is (the first downhill determination flag F1 remains 1), but if it is smaller, the process proceeds to step 114, and after the first downhill determination flag F1 is reset to zero, the process proceeds to step 116. move on.

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.

With the above control flow, the determination of the downhill road with the first gradient as the threshold value (considering the engagement state of the lock-up clutch 24) 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 or not 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. The KDEG is a predetermined value (acceleration: positive only) that is set higher in the high vehicle speed range and the low vehicle speed range than in the middle vehicle speed range depending on the vehicle speed (output shaft rotation speed). And as a result the first
It is mapped so as to correspond to a second road surface gradient (second gradient) smaller (slower) than the gradient.

At 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 directly proceeds to step 222, where the second downhill road determination flag F10 is set to zero. Is reset to

Note that 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, in step 120, it is determined whether or not the condition for starting downhill control is satisfied.

Specifically, 1) the idle contact switch 92 is turned on (the accelerator is released), 2) the foot brake switch 88 is turned on (the brake is depressed), and 3) the first downhill road determination flag. When all the conditions that F1 is 1 are satisfied, or 4) The foot brake switch 88 is turned on (the brake is depressed). 5) It is within a predetermined time t0 after the idle contact switch 92 is turned on. 6) When all of the conditions for setting the second downhill road determination flag F10 to 1 are satisfied, it is determined that the downhill control start condition is satisfied, and the routine proceeds to step 122, where the fourth speed position inhibition request flag F3 for the downhill road is set. Set to 1.

If the condition for starting the descent is not satisfied, step 122 is bypassed. Therefore, at this time, the fourth-speed-gear prohibition request flag F3 for the downhill road is not set to 1.

In this way, when step 126 is reached,
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 the reset / restart operation is started 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-gear-prohibition request flag F2 for ascending is reset to zero in step 132.
Proceeding to step 142, the value of the fourth-speed upshift prohibition request flag F2 for ascending is again checked. If this value is 1, the fourth speed is prohibited at 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 inhibition prohibition request flag F2 for the uphill is not 1. If so, the process proceeds to step 134.

At 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 (first gradient), and as a result, the speed of the low speed Control can be prevented from being executed, and when 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, Even when the vehicle is traveling on a road having an extremely small road surface gradient (second gradient), it is possible to surely shift down to a low gear. 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.

Further, according to this embodiment, it is estimated that the first gradient is substantially in the disengaged state after the lock-up clutch is disengaged and the lock-up clutch is engaged but shifted down. In the three driving states, namely, the driving state in which the lock-up clutch is engaged and the driving state in which the lock-up clutch is assumed to be in the engaged state even after downshifting, the state is set so that the state is sequentially changed from small to large. As a result, the effect of increasing the engine brake is conspicuously found as a result of downshifting by executing the downhill control, and when it is considered that there is no particular problem, the first gradient that is set to be the gentlest is used. A downhill road is determined as the threshold value. Next, although the effect of increasing the engine brake from the current state is slight, the engine If it is determined that the state does not become too effective, a downhill road is determined using the first gradient set slightly larger than this as a threshold, and further downshifting is performed by executing downhill control. If there is a concern that the vehicle may become too effective, a downhill road is determined with the largest gradient set as the first threshold (entering downhill road control only when the vehicle is traveling on a fairly steep road surface gradient). Will be able to do it.

Accordingly, the advantages and disadvantages of executing the downhill control are purposefully compared and considered, thereby preventing the busy shift and the deterioration of the fuel economy, and enabling the downhill control to be started immediately when necessary. .

[0089]

As described above, according to the present invention, it is possible to effectively prevent the "downshift control on a downhill road" from being performed more than necessary, so that the fuel efficiency is not deteriorated and the Thus, it is possible to obtain an effect that traveling with sufficient engine brake can be realized.

[Brief description of the drawings]

FIG. 1 is a flowchart showing details of step 110 in FIG.

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.

[Explanation of symbols]

 Reference numeral 24: Lock-up clutch 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: Actual vehicle acceleration SGB43 ... Reference vehicle acceleration (on flat road) SBGE43 ... Reference vehicle acceleration (on 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-5-149424 (JP, A) JP-A-3-117774 (JP, A) JP-A-63-203439 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16H 61/00-61/24

Claims (2)

(57) [Claims] A lock-up clutch, means for judging whether or not the vehicle is traveling on a downhill road with a road surface gradient of a predetermined value or more, and a shift suitable for the downhill road when it is determined that the vehicle is traveling on the downhill road A control device for controlling the automatic transmission for downhill roads, comprising: means for detecting whether the lock-up clutch is engaged or disengaged. Means for setting the predetermined value to a larger value when the lock-up clutch is in the engaged state than when the lock-up clutch is in the released state, and a control device for an automatic transmission for a vehicle on a downhill road, characterized by comprising: 2. The system according to claim 1, further comprising: means for estimating an engaged / disengaged state of the lock-up clutch after the shift characteristic is switched; and a predetermined value set in the engaged state of the lock-up clutch. Means for setting a larger value when the engaged state is estimated than when the disengaged state is estimated according to the estimation result, and a control device for an automatic transmission for a vehicle on a downhill road, comprising: