JPH0828696A - Control device of automatic transmission for vehicle on downhill road - Google Patents

Abstract

PURPOSE:To realize the downhill road control appropriate for the road surface friction coefficient, and secure the required engine brake by detecting the road surface friction coefficient, and reducing the prescribed value in realizing the transmission control according to the transmission characteristic when the road surface friction coefficient is low compared with when it is high. CONSTITUTION:An automatic transmission 2 switches the transmission characteristic by judging whether or not the vehicle is traveling on the downhill road in a computer 84 to input the output signals from a throttle sensor 80, a vehicle speed sensor 82, a foot brake switch 88, etc. The road surface friction coefficient muis detected in making a judgement whether or not the vehicle is traveling on the downhill road by comparing the actual acceleration of the vehicle with the preset prescribed value, and the prescribed value to judge the downhill road is set to be small when the value mu is small compared with when it is large. This constitution facilitates the judgement that it is the downhill road, and surely realizes the shift down even when the vehicle is traveling on the compressed snowy road with studless tires mounted.

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]

However, the above-mentioned JP-A-5-71623 or JP-A-5-7162.
When it is attempted to determine a downhill road by a method such as the conventional example of Japanese Patent Publication No. 5, etc., for example, when a studless tire, a tire with a chain, etc. are mounted and traveling on a snowy road, etc., the running resistance is There is a problem that the actual acceleration tends to have a smaller value than that when traveling on a normal road because it becomes large. As a result, the road gradient is erroneously determined to be smaller than the actual road gradient, making it difficult to determine the downhill road, and the downshift by downhill control does not function effectively.

In particular, when traveling on a so-called low μ road having a small road friction coefficient μ, the driver demands that the engine brake be effective even if the road surface gradient is smaller than usual, and the problem is more serious. There was a fear that it would be remarkable.

The present invention has been made in order to solve such a conventional problem, and when the road surface friction coefficient is low, the downhill road control corresponding to the low road surface friction coefficient can be executed to ensure the necessary engine braking. An object of the present invention is to provide a control device for an automatic transmission for a vehicle on a downhill road.

[0010]

SUMMARY OF THE INVENTION The present invention is a means for detecting an actual acceleration of a vehicle and a means for judging whether or not the vehicle is a downhill road by comparing the actual acceleration with a predetermined value. And a means for shifting to a shift characteristic suitable for the downhill when it is determined that the vehicle is traveling on the downhill, and performing shift control according to the changed shift characteristic. In the device, means for detecting the road surface friction coefficient, and means for setting the predetermined value according to the road surface friction coefficient, and for reducing the predetermined value when the road surface friction coefficient is low compared to when the road surface friction coefficient is high, The above-mentioned object is achieved.

The present invention also provides a means for determining whether or not the vehicle is traveling on a downhill road having a road surface gradient of a predetermined value or more, and a shift characteristic suitable for the downhill road when it is determined that the vehicle is traveling on the downhill road. In a control device for an automatic transmission for a vehicle on a downhill road, the means for performing a shift control according to the changed shift characteristic, the means for detecting a road surface friction coefficient, and the predetermined value according to the road surface friction coefficient. When the road surface friction coefficient is low and the road surface friction coefficient is high, a means for reducing the predetermined value is provided as compared with a case where the road surface friction coefficient is high.

[0012]

The present invention is based on the premise that it is determined whether or not the vehicle is a downhill road by comparing the actual acceleration of the vehicle with a predetermined value set in advance. This method is used to determine the downhill road as it is. Then, the problem that inevitably occurs is improved so as not to occur. That is, when traveling on a snow-covered road with studless tires, chain-mounted tires, etc., the actual vehicle acceleration decreases due to the increase in running resistance, and as a result, the road gradient that is judged to be a downhill road during normal running However, it solves the problem that it is no longer judged to be a downhill road.

Specifically, when the road surface friction coefficient is detected, and when it is low, the predetermined value for judging the downhill road is set to be smaller than when it is high, and it is determined that the road is a downhill road. Make the judgment easier. As a result, for example, it is possible to surely perform downshift when traveling on a snow-covered road with studless tires, that is, when running resistance is large and acceleration is less likely to occur than when traveling on a normal road surface. Becomes

The road surface friction coefficient is detected by, for example, slip detection from front and rear wheel speed signals from a wheel speed sensor of the antilock brake system, or operation detection and operation history of the antilock brake system and traction control system. This can be performed by detection, and further by detecting the selection of the snow pattern position of the shift pattern selection switch.

On the other hand, the invention of claim 3 is not so passive as to prevent the occurrence of a problem when a downhill road is determined by comparing the actual vehicle acceleration with the reference vehicle acceleration as in claim 1. Instead, the threshold value of the road surface gradient when the road is determined to be a downhill road is lowered more actively in the case of a low μ road. Therefore, in the case of claim 3, the method of detecting a downhill road is not limited, and the invention is also applied to a method of directly detecting a road surface gradient by providing an inclination sensor or the like. You can

According to the third aspect of the present invention, it is possible to determine that the road is a downhill road even on a low μ road even if the road has a gentle slope. Therefore, it is possible to more reliably apply the engine braking.

In the meantime, including the invention of claim 1, when downshifting by downhill control can be further executed on a low μ road, it is uncomfortable for the driver if the downshifting is executed during turning. It may cause vehicle behavior.

According to the second or fourth aspect of the present invention, it is possible to effectively prevent the occurrence of such a problem because the downshift control is prevented from executing downshifting during turning.

[0019]

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 the accelerator opening) for reflecting the load of the engine 1, a vehicle speed sensor (rotational speed sensor of the output shaft 70) 82 for detecting a vehicle speed, a parking range, Shift position switch 8 for outputting a signal of a shift position selected by the driver such as drive range and L range
6. A foot brake switch 88 that outputs a signal when the foot brake is stepped on, an engine speed sensor 90 that detects the engine speed, and an idle that outputs the state of the idle contact point (ON when accelerator is released, OFF when stepped on) A contact switch 92, a pattern select switch 94 for selecting whether to drive with emphasis on power performance (power pattern) or travel with emphasis on fuel efficiency (normal pattern), and cruise control (automatic constant vehicle speed travel) Signals for various controls such as the cruise control switch 97 and the overdrive off switch 97 for prohibiting traveling in overdrive (4th speed) are 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 stage to be selected first according to a preset (similar to the 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 performs special control on the uphill / downhill road according to the traveling state according to the control flow as shown in FIGS.

FIG. 4 shows a schematic flow of the special control on the uphill 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 predetermined conditions. , (Even if it is determined on the basic shift map that the fourth gear should be shifted up), the third gear is held.
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 speed stage to the third speed stage 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 a Downhill Road> In the control on a downhill road, there are two types of the first slope and the second slope which are relatively large in the threshold value (predetermined value) of the road surface slope for determining the “downhill road”. Be prepared.

This embodiment relates to the embodiments of claims 1 and 2, and the thresholds (first slope and second slope) for judging the downhill road are intended to be changed. However, it is intended to make a correction so as to prevent the first gradient from becoming substantially large as a result when the vehicle runs on a low μ road.

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, the vehicle is shifted up to the fourth speed as long as the conditions of the descending slope having a slope larger than the first slope, the accelerator release, and the foot brake on are continuously satisfied. It is prohibited, and the third speed is held (even if it is determined on the basic shift map that the fourth speed should be shifted up). Since the first gradient is set to be relatively large, the frequency with which the control relating to the first 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, in the state where 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 on a gentle slope), 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 at the fourth speed stage. 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 at the third speed when the accelerator is depressed and the vehicle is upshifted to the fourth speed when the accelerator is released, the second speed
It does not return to the third speed again by the control related to the gradient.

The reason for this is that the control related to the second gradient is executed and the gear is downshifted to the third speed again until the fourth speed is upshifted due to 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 at 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 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, 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 prerequisites 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 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.

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

In 2) and 3), the third drive range
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 less than 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 engine overrun.

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 inactive is that the cruise control is executed, and in order to maintain the vehicle speed constant, a separate gear stage is used in order to keep the vehicle speed constant. 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 with 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 the conditions as described above, 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 the uphill road, the routine proceeds to step 108. Go to the flag F0
Is reset to zero.

At step 110, it is judged whether 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 the 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, then flow proceeds to step 202 where the SBGE 43 map is searched. SBGE43 is a gear position (3rd
Speed, fourth speed), reference vehicle acceleration for downhill roads (positive and negative) that is pre-mapped with the first road surface slope (first slope) as a reference depending on the vehicle speed for each select pattern
And corresponds to the predetermined value in the claims.

At step 203, it is judged whether the road is a low μ road, that is, whether the road surface friction coefficient μ is low. For determining a low μ road, for example, slip detection from front and rear wheel rotation speed signals from a wheel speed sensor of an ABS (antilock brake system), ABS / TRC (traction control system) operation detection, or a low μ road based on operation history is performed. Judgment is possible. Alternatively, when the shift pattern select switch is prepared to select a snow pattern, the determination may be made by detecting the snow pattern.

If it is not the low μ road, it is not necessary to perform the control according to the present invention, so the routine proceeds to step 208. If it is determined that the road is a low μ road, it is determined in the next step 205 whether or not the vehicle is turning.

If the vehicle is not turning, step 207
In, the predetermined value for downhill road determination is reduced so that downshifting is performed even with a gentler slope. Specifically, the value of SBGE43 is replaced with (SBGE43-predetermined value). As a result, when comparing with the actual acceleration, the downhill road determination is performed with a gradient that is gentler by a predetermined value than the SBGE 43 obtained from the map so far.

The predetermined value is determined in consideration of the increase in running resistance when running on a studless tire or a chain-mounted tire. Therefore, if the predetermined value is made to correspond to, for example, the parameter of the SBGE 43 and is mapped depending on the pattern selection and the vehicle speed, the invention of claim 1 can be realized with higher accuracy. In addition to the method of reducing the predetermined value, it is needless to say that a special map of the SBGE 43, which is separately prepared, may be used when it is detected that the road is low and the vehicle is not turning.

On the other hand, when it is detected in step 205 that the vehicle is turning, step 207 is bypassed to proceed to step 208 in order to prevent the behavior of the vehicle from changing due to downshifting during turning. This prevents the driver from being more likely to be downshifted during turning, and can prevent the driver from feeling uncomfortable due to an unexpected downshift, and the invention of claim 2 is embodied.

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
2, the actual vehicle acceleration MOBG calculated from the output of the vehicle speed sensor 82 is the reference vehicle acceleration SBGE4 for the downhill road according to the first slope obtained in step 202 or 207.
It is determined whether it is smaller than 3 by a predetermined time T4 or more.
If it is not smaller (the first downhill determination flag F1 remains 1), the process proceeds to step 116. If it is smaller, the process proceeds to step 114 and the first downhill determination flag F1.
Is reset to zero and the routine proceeds to step 116.

In step 208, the first descending slope 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.

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 gear is the fourth gear. Is determined.
If it is the 4th speed, proceed to step 216 and perform KD.
The EG's map is searched. This KDEG is a predetermined value (acceleration: positive only) set depending on the vehicle speed (output shaft speed), and as a result, the second road gradient (second gradient) smaller (slower) than the first gradient. ) Is mapped to correspond to.

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 established, or one of the third speed outputs after the judgment is established, 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. If it is determined 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 flag F1 becomes zero. It is determined whether or not the downhill control return timer to be counted up has expired, and if it has expired, the fourth downshifting prohibition request flag F3 for downhill road is reset to zero in step 140.

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 it is detected that the vehicle is traveling on a low μ road, the predetermined value for the downhill road determination is reduced, so that the downhill road determination is substantially performed. As a result, it is possible to prevent the road surface gradient for increasing from becoming large, and it is possible to surely perform the downshift. Further, when it is detected that the vehicle is turning, it is possible to prevent a change in vehicle behavior due to an unexpected downshift during turning by not reducing the predetermined value. Therefore, the driver's deceleration request can be more appropriately reflected in the shift control than ever, and the driving feeling can be improved accordingly.

The invention described in claims 3 and 4 can be easily realized by increasing the predetermined value in step 207 to be equal to or larger than the increase in running resistance.

As a result, when the vehicle is traveling on a low μ road, it is possible to enter the downhill control even if the road surface has a gentle road gradient that would not normally be entered in the downhill control. To be able to

[0089]

As described above, according to the present invention, it is possible to surely perform downshifting even while traveling on a low μ road.
It is possible to obtain an effect that traveling with less discomfort can be realized.

[Brief description of drawings]

FIG. 1 is a flow chart showing details of step 110 in FIG.

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.

[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)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiharu Harada 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (4)

[Claims] 1. A means for detecting an actual acceleration of a vehicle, a means for judging whether or not the vehicle is a downhill road by comparing the actual acceleration with a predetermined value set in advance, and a means for driving on the downhill road. If it is determined that there is a shift characteristic suitable for the downhill road, and the gear shift control is performed according to the changed shift characteristic, the control device for the automatic transmission for a vehicle on the downhill road detects the road friction coefficient. And a means for setting the predetermined value in accordance with the road surface friction coefficient and reducing the predetermined value when the road surface friction coefficient is low compared to when the road surface friction coefficient is high, for a vehicle on a downhill road. Control device for automatic transmission. 2. The means according to claim 1, further comprising means for detecting whether or not the vehicle is turning, and when it is detected that the vehicle is turning, the predetermined value is maintained even when the road surface friction coefficient is low. A control device for an automatic transmission for a vehicle on a downhill road, comprising: 3. Means for determining whether or not the vehicle is traveling on a downhill road having a road surface gradient equal to or more than a predetermined value, and when it is determined that the vehicle is traveling on the downhill road, a shift characteristic suitable for the downhill road is changed. A control device for an automatic transmission for a vehicle on a downhill road, comprising: means for performing shift control according to the changed gear characteristic; means for detecting a road surface friction coefficient; and a predetermined value set according to the road surface friction coefficient A control device for an automatic transmission for a vehicle on a downhill road, comprising: means for reducing the predetermined value when the friction coefficient is low as compared to when the friction coefficient is high. 4. The means according to claim 3, further comprising means for detecting whether or not the vehicle is turning, and when it is detected that the vehicle is turning, the predetermined value is maintained even when the road surface friction coefficient is low. A control device for an automatic transmission for a vehicle on a downhill road, comprising: