JPH0874983A - Controller for automatic transmission for vehicle in downhill road - Google Patents

Abstract

PURPOSE: To prevent excess downshift control in the downhill road from being performed by preventing fuel consumption from being deteriorated in downhill control. CONSTITUTION: A threshold value of the downhill road judging gradient is set to smaller if the engine operating state is the traveling state where it is in the engine fuel cut range, in comparison with the state where the engine operating state is not the traveling state, when the gear is downshifted from the high speed stage to the low speed stage suitable for the downhill road in downhill road traveling. Thereby, improvement of fuel consumption by fuel cut is easily achieved, and downshifting is made difficult to be performed when the fuel cut is not performed after downshifting, and deterioration of fuel consumption (caused by increase of the gear ratio) is prevented, and excess downshifting is prevented.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, in automatic transmissions for vehicles,
A gear shift map having vehicle speed and engine load (throttle opening degree, etc.) as parameters is provided, and the gear stage to be selected is determined by applying the information of the vehicle speed and engine load at that time during traveling to this gear shift map. .

However, since this shift map is created on the basis of a general flatland traveling state, it does not always give an optimum shift speed when traveling on a downhill road or an uphill road, for example.

In view of such circumstances, for example, Japanese Patent Publication Sho 59
Japanese Unexamined Patent Publication No. -8698 proposes a technique of separately providing a shift map according to a state of a traveling road such as traveling on a flat road and traveling on an uphill road, and appropriately switching these maps for use.

In this Japanese Patent Publication No. 59-8698, a reference vehicle acceleration (expected value of running acceleration) on a flat road is obtained in advance using parameters such as throttle opening and vehicle speed, and the reference vehicle acceleration and the vehicle speed are used. Also disclosed is a technique for comparing the calculated actual vehicle acceleration and determining that the actual acceleration is running on a downhill road when the actual acceleration is greater than a reference acceleration by a predetermined value or more, and the vehicle is traveling on an uphill road when the actual acceleration is smaller than the reference acceleration. Has been done.

Furthermore, in JP-A-5-71623 or JP-A-5-71625, when the actual acceleration is larger than the 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 a downhill road. A technique is disclosed in which when the determination is made, the shift characteristic is switched and the engine braking force is increased by downshifting to a lower speed.

[0007]

Generally, when the above-mentioned downhill control is carried out and the vehicle travels down a downhill road to a lower speed stage, the engine speed becomes higher than when traveling at a high speed stage, resulting in higher fuel consumption. Tends to get worse. This tendency becomes even stronger when the threshold value of the road surface slope for determining the downhill road is made small to facilitate the downhill control.

However, if the threshold value of the road surface gradient is simply set to a large value, the downhill control cannot be entered unless the road is a steep downhill road, and the downhill control does not function effectively.

On the other hand, for example, by executing downhill control, the fourth
If downshifting from third gear to third gear,
If the shift down shifts to the fuel cut region (which has been the fuel injection region until then), it is considered that the fuel economy is rather improved.

However, the above-mentioned Japanese Patent Laid-Open No. 5-71623
In the conventional examples such as Japanese Patent Laid-Open No. 5-71625 and Japanese Patent Laid-Open No. 5-71625, the "threshold of road surface gradient" for determining that the vehicle is traveling on a downhill road is always the same value under all traveling conditions. No consideration was given.

The present invention has been made to solve such a conventional problem. The running state in which the downhill control is executed partially overlaps with the running state in which the fuel cut control of the engine 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, which allows the above-described downhill control to function more effectively while preventing deterioration of fuel consumption as much as possible.

[0012]

SUMMARY OF THE INVENTION The present invention provides a means for determining whether or not a vehicle is traveling on a downhill road having a road surface gradient of a predetermined value or more, and a high speed step when it is determined that the vehicle is traveling on the downhill road. From the high speed stage to a low speed stage suitable for the downhill road, the control device for the automatic transmission for a vehicle on the downhill road, comprising: A means for detecting whether or not the operating condition is in the engine fuel cut region, and when the engine operating condition is in the fuel cut region when downshifting, as compared to the case where it is not. And a means for setting a predetermined value of the road surface gradient to be small, thereby achieving the above object.

[0013]

According to the present invention, the gradient threshold value (decision gradient for downhill road: which is a reference when judging whether or not the vehicle is traveling on a downhill road:
(Corresponding to the predetermined value) is changed / set according to whether or not the vehicle is in a traveling state in which the fuel cut control of the engine is executed when the vehicle is shifted to the low speed stage.

FIG. 1 shows the vehicle speed on the horizontal axis, the descending slope determination gradient in the upper part, and the fuel cut region (ON part) in the third and fourth speeds in the lower part. In the figure, the portion A indicated by the arrow is outside the fuel cut region at the fourth speed, but is inside the fuel cut region at the third speed, and corresponds to a region where the fuel economy is improved by downshifting. . Further, in the portion B, a region where fuel cut is not executed in both the fourth speed and the third speed (a region in which fuel consumption is deteriorated due to an increase in gear ratio due to downshift),
The portion C corresponds to a region where fuel cut is executed (a region where fuel efficiency is neither improved nor deteriorated) in both the fourth speed and the third speed.

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

Further, in the portion B which is out of the fuel cut region at the third speed, the value of the downhill road determination gradient is (A
Since it is set to a larger value (than the parts), it is difficult to downshift (when the gear ratio is increased) and it is possible to prevent deterioration of fuel efficiency when improvement in fuel efficiency due to fuel cut cannot be expected.

In the portion C of FIG. 1, the third speed,
Since both the fourth speed is in the fuel cut region, as shown by the dotted line in FIG. 1, even if the descending slope determination gradient has the same value as that of the section A, the fuel consumption does not deteriorate. Therefore, in the present invention, it is not required to intentionally match the C portion with the A portion. That is, for example, in the high vehicle speed range, the downhill road determination gradient is normally set as shown by the dotted line in the figure, and if there are other circumstances where it is desired to prevent unnecessarily downshifting, a large value like the solid line is set. It may be freely configured such as setting.

Further, the fuel cut region of the engine is generally set (under the condition that the accelerator is fully closed) depending on the shift speed and the vehicle speed. The present invention changes the threshold value of the gradient depending on whether the fuel cut state (not the vehicle speed) is reached. Therefore, for example, the fuel cut area is changed for some reason,
When the fuel cut is prohibited, the threshold value should be basically changed in conjunction with the change. However, the present invention does not necessarily require complete strict interlocking with such changes in the area in actual implementation.

In the present invention, the threshold value for downhill road determination is set to a larger value for a portion where fuel economy is likely to deteriorate due to downshifting because it is in an area where fuel cut is not executed. , It becomes difficult to judge that the gradient exceeds the threshold value, the frequency of gear shift is reduced (a busy shift is avoided), and it is possible to effectively prevent unnecessary downshifting. You can

As the gradient (threshold value) for judging the downhill road, "acceleration equivalent to the gradient" as in the embodiment described later.
May be used as the reference acceleration and compared with the actual acceleration calculated from the output of the vehicle speed sensor or the like to determine the downhill road, or in a vehicle equipped with a vehicle inclination angle sensor. May naturally use the gradient itself as a threshold. In the case of the present invention, in any case, the "gradient" itself, which is the criterion for determination, is changed depending on whether or not the fuel cut state is established.

[0021]

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

FIG. 2 is an overall schematic view 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 are well-known, and the output of the crankshaft 10 of the engine 1 is supplied to the overdrive mechanism unit 4.
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 gears consisting of a carrier 41,
The rotation state of this planetary gear device is controlled by a clutch C0, a brake B0, and a one-way clutch F0.

The underdrive mechanism section 60 is provided with two sets of planetary gear units consisting of 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
The connection state with the clutches C1, C2, the brake B1 ~
It is controlled by B3 and one-way clutches F1 and F2.

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 (rotation speed sensor of the output shaft 70) 82 for detecting a vehicle speed, a parking range, a drive. range,
A shift position switch 86 that outputs a signal of a shift position selected by the driver such as the L range, a foot brake switch 88 that outputs a signal when the foot brake is stepped on, an engine speed sensor that detects the 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 travel with emphasis on fuel efficiency (normal pattern) For various controls such as a pattern select switch 94 to be selected, a cruise control switch 97 for realizing cruise control (automatic constant vehicle speed travel), and an overdrive off switch 97 for prohibiting travel at overdrive (4th speed). Signal is being input.

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

The computer 84 uses the input signals from the respective sensors, switches, etc. as parameters to determine the gear position to be selected first according to a preset (similar to conventional) basic shift map of throttle opening-vehicle speed. Then, the solenoid valves S1, S2, S3, S4, etc. in the hydraulic control circuit 98 are driven and controlled so that the shift speed is achieved. As a result, as shown in FIG. 3, the respective clutches, brakes, etc. are engaged or released, and four forward gears (the fourth gear is overdrive) and one reverse gear are achieved.

Here, the computer 84 is shown in FIG.
According to the control flow as shown in FIG. 5, the special control on the uphill / downhill road is performed according to the traveling state.

FIG. 4 shows a schematic flow of the special control on the ascending / descending slope road.

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

<Control on an uphill road>

When it is determined that the vehicle is traveling on an uphill road, it is prohibited to shift down to the third speed and then up to the fourth speed under a predetermined condition. The third gear is held even if it is determined above that the fourth gear should be shifted up. The main purpose is to secure power performance and prevent busy shift.

In the case of an uphill road, the forced downshift from the fourth gear to the third gear is not executed. That is, only when it is determined on the basic shift map that the downshift from the fourth speed to the third speed should be performed, the downshift is performed in synchronization with it. The reason is that there is a risk of discomfort if a downshift is executed at a time when the driver does not expect while the vehicle is stepping on the accelerator.

<Control on Downhill Road>

In the control on the downhill road, two types of threshold values (predetermined values) of the road surface gradient for determining the "downhill road" are prepared: a relatively large first gradient and a smaller second gradient. Further, both the first gradient and the second gradient have the tendency shown in FIG. 1, and depending on whether or not each of them is in a traveling state in which a fuel cut state is obtained after downshifting, specifically, Change or set depending on the corresponding vehicle speed. That is, in the high vehicle speed range C and the low vehicle speed range B, the first slope and the second slope themselves are set to have larger values than those in the medium speed range of FIG. 1A, and more detailed control is performed. It is a thing.

When it is determined that the vehicle is a "downhill road" 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 downshifted 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 the driver does not feel uncomfortable because the foot brake is on.

Further, when the vehicle is traveling at the third speed, it is prohibited to shift up to the fourth speed as long as the condition for releasing the accelerator and releasing the downhill road having a slope greater than the first slope is satisfied. 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 relatively large, this first
The frequency with which the control related to the gradient is executed is reduced as compared with the conventional case.

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

That is, when the accelerator is depressed, the fourth
When the accelerator is released and the foot brake is operated within a predetermined time after the accelerator is released while traveling at a high speed,
Assuming that the driver intends to decelerate (even with a gentle second gradient), the engine is forcibly downshifted to the third speed with stronger engine braking.

By the way, in the control flow described later, the downhill road is determined with the second gradient as the threshold value only when the accelerator pedal is depressed and the vehicle is traveling in the fourth gear. This is because, because of the nature of the conditions, it may not be enough to start the downhill road judgment after the accelerator is released, and the other is that the vehicle runs at the fourth speed when the accelerator is depressed. This is because the control (shift down) related to the second gradient is executed only when the above-mentioned situation has occurred. That is, when the vehicle is traveling in the third gear when the accelerator is depressed and the gear is upshifted to the fourth gear when the accelerator is released, it is not possible to return to the third gear again by the control according to the second gradient. do not do.

The reason for this is that the control relating to the second gradient is executed and the shift down to the third speed is performed again until the fourth speed is upshifted with the release of the accelerator. In this case, when the driver repeatedly depresses the accelerator, releases the pedal, and repeatedly operates the foot brake on a gentle downhill road, the gear shift is executed very frequently, and the time for traveling in the third speed (low speed) is increased. This is because it becomes longer than necessary and fuel efficiency deteriorates.

Therefore, for the same reason, in the case of the downhill road control with the second gradient as the threshold value, the control of holding at the third speed is not executed. Therefore, upshifting from the third speed stage to the fourth speed stage can be carried out freely as the basic shift map is changed.

The control flow for executing the above-described uphill / downhill control will be described below with reference to FIG.

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

Specifically, the preconditions are: 1) the vehicle speed sensor 82 of the automatic transmission is normal, 2) the shift position switch 86 is in the drive range, 3) the third speed, Alternatively, one of the fourth speed stages is outputting, 4) the vehicle speed is equal to or higher than a predetermined value and equal to or lower than the predetermined value, for example, 1
Within the range of 5 km / h to 125 km / h, 5) Overdrive off switch 97 is off (non-acting), that is, overdrive (4th speed) is in a permissible state, 6) The cruise control switch 96 is off, and 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.

In 1), the condition that the vehicle speed sensor 82 of the automatic transmission is normal is that the vehicle speed sensor 82 fails, and if the vehicle speed sensor 82 fails, it is an essential climbing and descending slope for executing this control. This is because the judgment itself cannot be made.

2) The third drive range in 3)
The condition that either the first speed or the fourth speed is being output is that the present control is executed only for holding or downshifting in the third speed and the fourth speed of the drive range. This is because.

In 4), the condition that the vehicle speed is within the predetermined value is that the second speed or the first speed is outside the applicable range of this control when the vehicle speed is below the predetermined value. This is because when the vehicle is in a state where the vehicle should enter and when the vehicle speed is equal to or higher than the predetermined value, the vehicle should be maintained at the fourth speed to prevent overrun of the engine.

In 5), the condition that the overdrive off switch is in the non-acting state is set as a condition when the driver intentionally avoids traveling in the overdrive (4th speed). This is because there is no room for holding or downshifting in the third speed and the fourth speed by the control.

In 6), the condition that the cruise control is in the non-acting condition is that the cruise control is executed. Is automatically controlled.

When 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 the uphill road determination condition is satisfied. In this case, some hysteresis is provided between when the non-uphill road is determined to be an uphill road and when the 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 a predetermined time T2 or more, it is determined that the vehicle is approaching an uphill road from a non-uphill road. On the other hand, when MOBG> SBG43-KDGSN, the predetermined time T3
When it is determined that the above conditions are satisfied, it is determined that the vehicle has changed from an uphill road to a non-uphill road.

Here, MOBG represents the actual acceleration of the vehicle calculated from the output of the vehicle speed sensor (the rotation speed sensor of the output shaft 70 of the automatic transmission) 82, and the SBG 43 represents each shift using the throttle opening and the vehicle speed as parameters. Gear (3rd gear,
4 shows the reference vehicle acceleration during flat road traveling, which is mapped in advance for each fourth speed stage. Depending on both conditions, it may be positive or negative. Further, KDGSF is a predetermined value (only positive) which is previously mapped so as to be constant up to a medium vehicle speed depending on the vehicle speed and increase at a high vehicle speed, and KDGSN is a select pattern (power pattern, normal pattern) by the pattern select switch 94. ) Is also a predetermined value (only positive) that is previously mapped so as to increase at a high vehicle speed depending on the vehicle speed.

When the vehicle speed (output shaft speed) is the same, KDGSF> KDGSN (normal)> KDGSN
It is set to be (power). The reason why KDGSF is set larger than KDGSN is to give a hysteresis to the judgment, and KDGSF is set to K rather than KDGSN (power).
The DGSN (normal) is set to be larger because it is more difficult to judge that the uphill road has changed to the non-uphill road in the power pattern than in the normal pattern. This is because the state of is maintained for a long time. If the third speed is maintained for a longer period of time, the fuel economy will be slightly reduced, but the busy shift will be prevented and the acceleration and engine braking effectiveness will be improved accordingly, allowing the driver to travel more sensitive to the movement of the accelerator pedal. .

When it is determined that the vehicle is an uphill road by the determination of such conditions, the routine 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 vehicle is not an uphill road, the routine proceeds to step 108. Go to the flag F0
Is reset to zero.

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

The downhill road determination is specifically executed according to a control flow as shown in FIG.

That is, when the uphill road determination flag F0 is reset to zero in step 108, the flow proceeds to step 1
10, the routine proceeds to step 200, where it is determined in step 200 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, flow proceeds to step 202 where the SBGE 43 map is searched. SBGE43 is a gear position (3rd
(Speed stage, fourth speed stage), depending on the vehicle speed for each select pattern, the reference vehicle acceleration for which the slope threshold value has been corrected for the downhill road, which is mapped in advance using the first road surface slope (first slope) as a reference. (There are positive and negative).

That is, the way the SBGE 43 depends on the vehicle speed is not limited to the dependence that the predicted acceleration is small (on a flat road) because the running resistance becomes large only at a high vehicle speed. As shown in FIG. 1, that is, when the vehicle speed is in the parts B and C of FIG. 1 is more than in the part A (when the vehicle is in the fuel cut state by being downshifted to the third gear). The first gradient itself is made to be so tight that it is dependent. This makes it easier to determine that the vehicle is in the vehicle speed range of FIG. 1A as a downhill road (it is easy to shift down to the third speed in the vehicle speed range of this section A), and it is possible to improve fuel efficiency by implementing fuel cut. .

At step 208, it is judged if the first downhill road judgment flag F1 is zero. When the first downhill road determination flag F1 is 1, that is, when it has been determined that the road is a downhill road having the first slope or more, step 21
Then, it is judged whether the actual vehicle acceleration MOBG calculated from the output of the vehicle speed sensor 82 is smaller than the reference vehicle acceleration SBGE43 for the downhill road according to the first slope obtained in step 202 by a predetermined time T4 or more. It If it is not smaller, it is as it is (the first downhill road determination flag F1 remains 1)
If it is smaller, the routine proceeds to step 114, where the first downhill road determination flag F1 is reset to zero, and then the routine 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 the reference vehicle acceleration SBGE.
43, it is judged whether or not it is longer than the predetermined time T5 or more. If it is larger, the first downhill road determination flag F1 is set to 1 in step 112, and if it is not larger, it remains at step 11
Proceed to 6.

Through the above control flow, the determination of the downhill road with the first gradient as the threshold value is executed. As described above, the first gradient itself has a characteristic that depends on whether or not the fuel cut state is set at the third speed as shown in FIG. 1 (specifically, vehicle speed).

On the other hand, when it is determined in step 200 that the idle contact is not on, that is, when 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 speed is the fourth speed. Is determined.
If it is the 4th speed, proceed to step 216 and perform KD.
The EG's map is searched. This KDEG is in the high vehicle speed range and the low vehicle speed range corresponding to the parts B and C in FIG. 1 depending on the vehicle speed (the number of rotations of the output shaft) and for the same purpose as the threshold value of the first gradient. Is a predetermined value (acceleration: positive only) set larger than that in the middle vehicle speed range corresponding to the section A, and as a result, the second road gradient (second) smaller (slower) than the first gradient (second) It is mapped so as to correspond to (gradient).

In this way, SBGE43 or KD
By considering EG as a map based on the vehicle speed or the output shaft speed in consideration of the meaning shown in FIG. 1, the gradient as the threshold value for the determination of the downhill road is intended in the present invention (shift to the third speed stage). It can be set low if the fuel is cut when it goes down).

In step 218, it is determined whether or not it is determined to be a downhill road when the second gradient is used as a threshold value, that is, whether the value of the second downhill road determination flag F10 should be zero or one. It Specifically, when the value of the flag F10 is currently zero, MOBG> SBG43 + KDEG + KD
If GE is satisfied for a predetermined time T6 or more, step 220
The flag F10 is set to 1. When the current flag F10 is 1, MOBG≤SBG43 + KD
When EG is established for a predetermined time T7 or more, step 222
Then, the flag F10 is reset to zero. Where SBG
As described above, 43 is the reference vehicle acceleration on a flat road (and for an uphill road) that is configured by both parameters of 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 gear is not the fourth gear, that is, the third gear, the routine proceeds directly to step 222, where the second downhill road determination flag F10 is zero. Is reset to.

The first step 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 made only when the idle contact is off and the vehicle is traveling at the fourth speed is as described above.

Returning to FIG. 4, step 1 is performed in this manner.
When it reaches 16, it is judged here whether or not the slope 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) to the third gear according to the basic shift map. The condition that the power-on downshift (downshift when the accelerator is depressed) judgment is satisfied, or one of the third speed outputs after the judgment is satisfied, 4) The uphill road determination flag F0 is 1. When all the conditions are satisfied, it is judged that the condition for starting the uphill control is satisfied, and the routine proceeds to step 118, where the fourth speed stage prohibition request flag F2 for the uphill road is set to 1. If any of the climbing control start conditions 1) to 4) is 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 after that based on the basic shift map is used as one of the conditions for starting the uphill control, as described above. By executing this control while traveling in the speed stage (when the driver does not intend), the fourth gear position to the third gear position
This is to prevent downshifting to a higher speed. That is, in the uphill control, the positive shift down from the fourth speed to the third speed is not performed, and only the shift up from the third speed to the fourth speed is prevented.

On the other hand, in step 120, it is judged whether or not the downhill control start condition is satisfied.

Specifically, 1) the idle contact switch 92 is on (the accelerator is released), 2) the foot brake switch 88 is on (the brake is stepped on), 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), and 5) the idle contact switch 92 is turned on within a predetermined time t0. 6) When all the conditions for the second downhill road determination flag F10 to be 1 are satisfied, it is determined that the downhill control start condition is satisfied, and the routine proceeds to step 122, where the fourth downhill speed prohibition request flag F3 for downhill road is set. Set to 1.

If the downhill start condition is not satisfied, step 122 is bypassed. Therefore, at this time, the fourth speed stage prohibition request flag F3 for downhill road is not set to "1".

When step 126 is reached in this way,
After that, the actual processing is performed based on the value of each flag.
First, at step 126, it is judged if the uphill judgment flag F0 is zero. Further, at step 128, it is judged whether or not the fourth speed step prohibition request flag F2 for the uphill road is 1.

When the uphill road determination flag F0 is zero but it is determined that the fourth speed stage prohibition request flag F2 for uphill road is 1, the routine proceeds to step 130, where the count is counted up from a predetermined time. It is determined whether or not the uphill control return timer has expired. If it has been completed, the fourth speed prohibition request flag F2 for climbing is reset to zero in step 132, but if it has not been completed, step 1
The program proceeds to 42 and again checks the value of the fourth speed gear prohibition request flag F2 for climbing, and when it is 1, the fourth speed gear is prohibited in step 146.

On the other hand, when it is judged that the uphill judgment flag F0 is not zero, or even if it is judged that the flag F0 is zero, it is judged that the fourth speed prohibition request flag F2 for uphill is not one. If so, the process proceeds to step 134.

At step 134, the value of the first downhill road determination flag F1 is determined. Further, at step 136, it is judged if the fourth downshifting prohibition request flag F3 for downhill is 1 or not. When it is judged that the fourth downhill speed prohibition request flag F3 for downhill road is 1 even though the first downhill road determination flag F1 is zero, the routine proceeds to step 138, where the counting is started from a predetermined time. It is determined whether or not the downhill control return timer has expired, and if it has expired, in step 140, the fourth downshifting stage prohibition request flag F3 for downhill roads.
Is reset to zero.

However, the first descending slope determination flag F1
Is not zero, or even if it is zero
When the speed prohibition request flag F3 is not 1, and when 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 If either one of the speed prohibition request flags F2 and F3 is 1, the fourth speed is prohibited 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 slope road as described before the concrete description of the control flow is realized.

According to this embodiment, as described above, the basic threshold value for determining the downhill road can be set to a relatively large value (first slope), and as a result, the low speed stage is unnecessarily required. It is possible to prevent the control of downshifting to be executed at the same time, and when the foot brake is operated within a predetermined time from the time when the accelerator is released, consider that the driver wants sudden deceleration and Even if the vehicle is traveling on a road having a relatively small road gradient (second gradient), it is possible to reliably shift down to a low speed stage. 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, as described above, when the first gradient and the second gradient are traveling in the fuel cut region at the third speed indicated by A in FIG. Is set to a value smaller than the other regions, it is easy to downshift to the third speed, and fuel efficiency can be improved by implementing fuel cut. Moreover, FIG.
In sections B and C, since the gradient is set to a larger value, it is difficult to shift down even if the fuel economy is not improved due to the fuel cut even if the downshift is performed. It is possible to prevent deterioration of fuel efficiency due to an increase in gear ratio.

[0087]

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

[Brief description of drawings]

FIG. 1 is a diagram showing a set slope for downhill road determination according to the present invention.

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

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

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

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

[Explanation of symbols]

 80 ... Throttle sensor 82 ... Vehicle speed sensor (output shaft rotation 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 ... (On flat road ) Reference vehicle acceleration SBGE43 ... Reference vehicle acceleration (on a downhill road)

Claims (1)

[Claims] 1. Means for determining whether or not a vehicle is traveling on a downhill having a road surface gradient of a predetermined value or more, and, when it is determined that the vehicle is traveling on the downhill, a high speed stage to a low speed stage suitable for the downhill road. In a control device for an automatic transmission for a vehicle on a downhill equipped with a means for downshifting to, the engine operating state becomes an engine fuel cut region when downshifting from the high speed stage to a low speed stage suitable for the downhill road. Means for detecting whether or not the vehicle is in a running state, and when the engine operating state is in the fuel cut region when downshifting, the predetermined value of the road surface gradient is set in comparison with the case where it is not. A control device for an automatic transmission for a vehicle on a downhill road, comprising: means for setting a small value.