JP3102278B2 - 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]

Generally, when the above-described downhill control is performed and the vehicle is driven downshifting to a low speed stage on a downhill road, the engine speed becomes higher than when traveling at a high speed stage, and the fuel consumption is reduced. Tends to worsen. This tendency is further strengthened when the threshold value of the road surface gradient for determining a downhill road is reduced to facilitate downhill control.

[0008] However, if the threshold value of the road surface gradient is simply set to a large value, it is necessary to enter the downhill control unless the road is a steep downhill road, and the downhill control does not function effectively.

On the other hand, for example, the execution of downhill control
If the gear is downshifted from third gear to third gear,
If the shift down shifts to a fuel cut region (which was previously a fuel injection region), fuel efficiency would be rather improved.

[0010] However, Japanese Patent Application Laid-Open No. 5-71623 discloses the above.
In the conventional example of Japanese Patent Application Laid-Open No. 5-71625 or Japanese Patent Application Laid-Open No. 5-71625, the "threshold of the road surface gradient" for determining that the vehicle is traveling on a downhill is always the same value under all traveling conditions. No consideration was given to

The present invention has been made to solve such a conventional problem, and the running state in which the downhill control is executed partially overlaps with the running state in which the engine fuel cut control is executed. It is an object of the present invention to provide a control device for an automatic transmission for a vehicle on a downhill road capable of making the above-described downhill control function more effectively while preventing deterioration of fuel efficiency as much as possible.

[0012]

SUMMARY OF THE INVENTION The present invention comprises means for determining whether or not the vehicle is traveling on a downhill road having a road surface gradient equal to or higher than a predetermined value. Means for shifting down to a low speed gear suitable for a downhill road from a high speed gear to a low gear suitable for a downhill road. Means for detecting whether or not the operating state is a driving state in which the engine is in a fuel cut region; and, if the engine is in a driving state in which the engine operating state is in a fuel cut region when downshifting, And means for setting the predetermined value of the road surface gradient to be small, thereby achieving the object.

[0013]

According to the present invention, a threshold value of a gradient which is a reference for determining whether or not the vehicle is traveling on a downhill road (a determination gradient of a downhill road:
(Corresponding to the predetermined value) is changed and set depending on whether or not the vehicle is in a running state in which fuel cut control of the engine is executed when the vehicle is shifted to the low gear.

FIG. 1 shows the vehicle speed on the abscissa, the downhill grade determination gradient in the upper part, and the fuel cut area (ON part) in the third and fourth gears in the lower part. In the figure, the portion A indicated by an arrow is outside the fuel cut region at the fourth speed, but is within the fuel cut region at the third speed, and corresponds to a region in which fuel efficiency is improved by downshifting. . A portion B is a region where fuel cut is not executed at the fourth speed stage or the third speed stage (a region where fuel efficiency is deteriorated due to an increase in gear ratio due to downshifting).
The portion C corresponds to a region where fuel cut is performed at both the fourth speed stage and the third speed stage (a region where fuel efficiency is neither improved nor deteriorated).

In the present invention, at least in the area of the part A where the fuel efficiency is improved, the downhill road determination gradient is set to be gentler than the area of the part B where the fuel efficiency is deteriorated. For this reason, in the area of the portion A, it is easier to shift down to the third speed, and as a result, fuel efficiency can be improved by the fuel cut executed.

Further, in the portion B which is out of the fuel cut region at the third speed, the value of the descending slope determination gradient is (A
Since it is set to a larger value than when the fuel cut is not expected, it is difficult to shift down when fuel efficiency cannot be expected to be improved by fuel cut, and deterioration of fuel efficiency (due to increase in gear ratio) can be prevented.

Note that, in a portion C in FIG.
Since both the fourth speed are in the fuel cut region, as shown by the dotted line in FIG. Therefore, the present invention does not require that part C is intentionally matched with part A. That is, for example, in a high vehicle speed range, the downhill road determination gradient is usually set as shown by a dotted line in the figure, and especially when there is another situation where it is desired to prevent an unnecessary downshift, a large value as shown by a solid line. It may be configured freely, such as by setting.

In addition, since the fuel cut region of the engine is generally set (under the condition of fully closing the accelerator) depending on the shift speed and the vehicle speed, the above description has been made using these parameters. In the present invention, the threshold value of the gradient is changed depending on whether or not the vehicle is in the fuel cut state (not the vehicle speed). For example, the fuel cut area is changed for some reason,
When the fuel cut is prohibited, the threshold value should basically be changed in conjunction therewith. However, the present invention does not always require that such a change in the area be completely strictly linked in actual implementation.

In the present invention, the threshold value for determining a downhill road is set to a larger value for a portion where fuel consumption is considered to be degraded due to downshifting because the fuel cut is not performed in the region where fuel cut is not performed. , It is difficult to determine that the gradient has exceeded the threshold value, the frequency of speed change is reduced (busy shift is avoided), and the downshift more than necessary is effectively prevented. Can be.

The gradient (threshold value) for determining a descending slope is determined by "acceleration corresponding to the gradient" as in the embodiment described later.
May be used as a reference acceleration, and may be compared with an actual acceleration calculated from an output of a vehicle speed sensor or the like to determine a downhill road, or may be provided with a vehicle inclination sensor. May naturally use the gradient itself directly as the threshold. In the case of the present invention, in any case, the "gradient" itself, which is the reference for determination, is changed depending on whether or not the fuel cut state is set.

[0021]

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 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 that outputs the state of the 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 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 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 FIG.
According to the control flow as shown in FIG. 5, 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>

If it is determined that the vehicle is traveling on an uphill road, shifting to the third speed and then shifting to the fourth speed under a predetermined condition is prohibited. The third gear is held (even if it is determined above that the gear should be shifted up to the fourth gear). 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 Downhill Road>

In the control on a downhill road, two kinds of thresholds (predetermined value) of the road surface gradient for determining “downhill road” are prepared: a first gradient that is relatively large and a second gradient that is smaller than the first gradient. Further, both the first gradient and the second gradient depend on whether or not the vehicle is in the fuel cut state after downshifting, so that the tendency shown in FIG. 1 is obtained. Change or set depending on the corresponding vehicle speed. That is, in the high vehicle speed region C and the low vehicle speed region B, the first gradient and the second gradient themselves are set to have larger values than the middle vehicle speed region in FIG. 1A, respectively, and more fine-grained control is performed. Things.

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 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 at the third speed, the shift-up to the fourth speed is prohibited as long as the condition of the descending slope and the accelerator release that is greater than the first gradient continues to be satisfied. The third gear is held (even if it is determined on the basic gear shift map that the gear should be shifted up to the fourth gear).
Since the first gradient is set relatively large, this first gradient
The frequency at which the control related to the 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 with a gentle second slope), the driver is forcibly downshifted to the third speed, where engine braking 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 to the third speed again until such time as shifting up to the fourth speed due to 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.

Therefore, 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 the 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.

In 4), the condition that the vehicle speed is within the predetermined value 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 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 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 to the non-uphill during the power pattern than during the normal pattern, and accordingly, the third speed is accordingly increased. 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 accelerator pedal movement 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.

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 a 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).
(Gear, fourth gear) and a reference vehicle acceleration corrected for a slope threshold for a downhill road that is pre-mapped based on a first road surface slope (first slope) depending on the vehicle speed for each select pattern. (With positive or negative).

That is, the manner in which the SBGE 43 depends on the vehicle speed is not limited to the dependence that the predicted acceleration (based on a flat road) becomes small because the running resistance increases when the vehicle speed is high. 1, that is, the vehicle speed in the portions B and C in FIG. 1 is higher than that in the portion A (in which the vehicle is in the fuel cut state by being shifted down to the third speed). The first gradient itself depends on the consideration so that it becomes tight. This makes it easier to determine that the vehicle is on a downhill road when the vehicle is in the vehicle speed range shown in FIG. 1A (it is easier to shift down to the third speed in the vehicle speed range shown in FIG. 1A), thereby improving fuel efficiency by performing fuel cut. .

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.
Then, it is determined whether 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 by a predetermined time T4 or more. You. If it is not small, keep it as it is (the first downhill road determination flag F1 remains 1)
The process proceeds to step 116, but when it is smaller, the process proceeds to step 114, where the first downhill determination flag F1 is reset to zero, and then 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. As described above, the first gradient itself has a characteristic depending on whether or not the fuel cut state is established at the third speed stage as shown in FIG. 1 (specifically, the vehicle speed).

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 depends on the vehicle speed (output shaft rotation speed) and has the same meaning as the threshold value of the first gradient, and the vehicle speed is in a high vehicle speed region and a low vehicle speed region corresponding to portions B and C in FIG. Is a predetermined value (acceleration: positive only) that is set to be greater than when the vehicle is in the middle vehicle speed range corresponding to the portion A, and as a result, the second road surface gradient (second (Gradient).

As described above, SBGE43 or KD
By making the EG a map based on the vehicle speed or the output shaft speed in consideration of the purpose shown in FIG. 1, the gradient serving as the threshold value for the determination of the downhill road is intended in the present invention (shift to the third speed). (If the fuel cuts when it goes down, lower it).

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 routine proceeds directly 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 related 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. Is satisfied, or one of the outputs of the third speed stage after the determination is satisfied, and 4) the ascending 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-stage-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 counts up from a predetermined time. It is determined whether or not the uphill control return timer has expired. If the processing has been completed, the fourth-speed upshift prohibition request flag F2 for climbing is reset to zero in step 132.
Proceeding to 42, the value of the fourth-speed fourth-speed-prohibition request flag F2 for ascending is confirmed again, and when this 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 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". If 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 count is incremented from a predetermined time. It is determined whether or not the downhill control return timer has expired. If the timer has expired, at step 140, the fourth shift stage prohibition request flag F3 for the downhill road is determined.
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). Control can be prevented from being executed, and when the foot brake is operated within a predetermined time after the accelerator is released, it is considered that the driver wants rapid deceleration, Even when the vehicle is traveling on a road with a very small road surface gradient (second gradient), it is possible to surely shift down to a low gear. As a result,
The driver's true deceleration request can be reflected in the shift control more than before, and the driving feeling can be improved accordingly.

Further, according to this embodiment, as described above, the first gradient and the second gradient are used when the vehicle is traveling in the region where fuel cut is to be performed at the third speed, which is indicated by A in FIG. Is set to a value smaller than that of the other regions, it is easy to shift down to the third speed, and fuel efficiency can be improved by executing fuel cut. Also, FIG.
In sections B and C, the gradient is set to a larger value. Therefore, even if the downshift is not expected to improve fuel efficiency, especially when the fuel cut is not expected, it is difficult to downshift, and the occurrence of a busy shift and Deterioration of fuel efficiency due to an increase in gear ratio can be prevented.

[0087]

As described above, according to the present invention, it is possible to effectively prevent the "downshift control on a downhill road" from being executed more than necessary while preventing the fuel efficiency from being lowered in the downhill control. Therefore, it is possible to obtain an effect that traveling with less discomfort can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a set gradient for downhill road determination according to 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;

[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)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16H 59/00-61/12 F16H 61/16-61/24 F16H 63/40-63/48 B60K 41/00-41 / 28 F02D 29/00-29/06 F02D 41/00-41/40

Claims (1)

(57) [Claims] A means for judging whether or not the vehicle is traveling on a downhill road with a road surface gradient equal to or higher than a predetermined value; Means for downshifting to an automatic transmission for a vehicle on a downhill road, wherein when the downshift from the high speed stage to a low speed stage suitable for the downhill road, the engine operating state is in an engine fuel cut region. Means for detecting whether or not the vehicle is in a running state. A control device for an automatic transmission for a vehicle on a downhill road, comprising: