JP2015040611A - Control device of automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an automatic transmission that actively executes downshift in a running state where moderate uphill roads continue, to cancel slowness feeling of a driver, while avoiding deterioration in drivability and deterioration in fuel consumption on a flat road and the like.SOLUTION: Even though an actual engine torque output rate R is an output rate determination value R0 or more (Yes in a step S8), when a vehicle acceleration G is less than an acceleration determination value G0 (Yes in a step S10), downshift may be delayed to feel a driver slow. When such a running state continues for a determination time T (Yes in a step S12), downshift is forcibly performed even though a target shift stage on a low gear side is not set by original transmission control (a step S14).

Description

  The present invention relates to an automatic transmission control device, and more particularly to an automatic transmission control device capable of quickly downshifting when a gentle uphill road continues.

2. Description of the Related Art In recent years, automatic transmissions that automatically switch gear positions according to the amount of accelerator operation by a driver, vehicle speed, and the like have become widespread not only in passenger cars but also in large vehicles such as trucks and buses. In such an automatic transmission, a target gear position is set based on an accelerator opening and a vehicle speed based on a predetermined shift map during traveling of the vehicle, and the gear position is switched so as to achieve the target gear position.
For example, when the gradual uphill road continues and the vehicle speed gradually decreases and crosses the downshift line on the shift map, the target gear stage is reset to the low gear side value and the downshift is executed. . Even if the vehicle speed does not cross the downshift line, the downshift is executed when the vehicle acceleration turns to the negative side and falls below a preset downshift determination value.

  On the other hand, as in the technique described in Patent Document 1, for example, the target speed change is performed on the condition that a predetermined time has elapsed after the vehicle speed reduction determination is made separately from the downshift based on the shift map. Some shift down is performed by setting the gear to the low gear side.

JP 2010-270883 A

However, the shift control according to the prior art has a problem that the downshift cannot be properly executed when a gentle uphill road continues.
As shown in the time chart of FIG. 3, for example, when a large load truck enters a gentle uphill road (point a in FIG. 3), the driver fully opens the accelerator as the vehicle speed V decreases (FIG. 3). However, the vehicle speed V begins to decrease. However, since the decrease in the vehicle speed V is slow, it takes time for the vehicle speed V to cross the downshift line (corresponding to the downshift determination value in the figure) on the shift map, and the vehicle acceleration that has turned to the negative side It takes time to fall below the shift-down determination value.

Although the figure shows a case where the downshift is approved by the vehicle speed V crossing the downshift line (point c in FIG. 3), it is considerably long from when the driver fully opens the accelerator until the actual downshift is executed. Requires response time. Therefore, although the vehicle does not stall, the downshift is greatly delayed in spite of the full opening of the accelerator, which makes the driver feel uncomfortable and unfavorable in terms of feeling.
Moreover, in the technique of the above-mentioned Patent Document 1, the downshift is executed uniquely after a predetermined time from the determination of the decrease in the vehicle speed V, but this process is performed on the traveling state of the vehicle that is slowly decreasing on the uphill road. It is not a reflection. Therefore, it was difficult to say that the driver's feeling of stickiness could be eliminated.
It is also conceivable to speed up the downshift by changing the setting of the downshift determination value so that the downshift is actively performed. However, with such measures, downshifting is executed only when a slight decrease in vehicle speed or vehicle acceleration occurs on a flat road, resulting in problems in terms of drivability and fuel consumption.

  The present invention has been made to solve such problems, and the purpose of the present invention is to avoid the adverse effects of drivability deterioration and fuel consumption deterioration on flat roads, etc., and a gentle uphill road. The present invention relates to a control device for an automatic transmission capable of eliminating a driver's feeling of shakiness by actively executing a downshift in continuous running conditions.

  In order to achieve the above object, the present invention provides a control device for an automatic transmission that executes a downshift by a downshift control means in accordance with a decrease in vehicle speed. A power transmission determining means for determining that the power from the traveling power source is being transmitted; an output rate calculating means for calculating an actual torque output rate as a ratio of the current torque to the maximum torque of the traveling power source; An output rate in which the actual torque output rate calculated by the output rate calculating unit is set in advance when it is determined that the power transmission is being determined by the acceleration detecting unit that detects the longitudinal acceleration of the vehicle and the power transmission determining unit. When the vehicle acceleration detected by the acceleration detection means is less than the predetermined acceleration determination value continues for the determination time, the shift is reduced. Characterized in that a downshift forcible passed means to pass a forced downshift even when a downshift is not passed by the control means.

When the actual torque output rate is equal to or higher than the output rate determination value, when the vehicle acceleration is less than the acceleration determination value, the shift-down control by the shift-down control means may delay the shift-down and give the driver a feeling of harshness. . If such a driving situation continues for the determination time, even if the downshift is not approved by the downshift control means, the downshift is forcibly approved, and the downshift is executed promptly accordingly. The driver's feeling of stickiness can be eliminated.
On the other hand, when either the requirement regarding the actual torque output rate or the requirement regarding the vehicle acceleration is not satisfied, the forced downshift is not executed, and the downshift is executed at a normal timing by the downshift control means. Therefore, it is possible to avoid, for example, a decrease in drivability on a flat road or a deterioration in fuel consumption.

As another aspect, it includes a rotational speed predicting means for calculating the rotational speed of the traveling power source after the downshift by the downshift forced approval means, and both the requirements regarding the actual torque output rate and the requirements regarding the vehicle acceleration are satisfied. Even if the state continues for the determination time, the shift is performed when it is determined that the rotation speed of the driving power source after the downshift is not maintained within the preset recommended use rotation range based on the calculation result of the rotation speed prediction means. It is desirable to configure a downshift compulsory approving means so as not to pass down.
It is possible to avoid a situation in which the rotational speed of the power source for traveling exceeds the upper limit of the recommended use rotational range due to inappropriate shift down, and thus it is possible to maintain a favorable traveling state of the vehicle.

As another aspect, the vehicle is provided with an accelerator operation amount detection means for detecting an accelerator operation amount by the driver, and a state in which both the requirements for the actual torque output rate and the requirements for the vehicle acceleration are satisfied continues for a determination time. However, it is desirable to configure the downshift compulsory approval unit so that the downshift is not approved when the accelerator operation amount detected by the accelerator operation amount detection unit is less than a predetermined determination value.
Based on the accelerator operation amount, it is possible to determine whether or not the driver is in a situation where it is easy for the driver to feel sticky, and thus it is possible to more accurately determine whether or not the shift is down.

As another aspect, it comprises determination time correction means for correcting the determination time to decrease as the vehicle acceleration detected by the acceleration detection means increases on the negative side, and determination processing based on the determination time after correction by the determination time correction means It is desirable to configure the downshift compulsory approval means so as to execute.
Since the determination time is shortened as the vehicle acceleration is larger on the negative side, downshifting can be performed more quickly, and the driver's feeling of rattling can be more reliably prevented.

As another aspect, the road surface gradient calculating means for calculating the gradient of the road surface on which the vehicle is traveling, and the acceleration judgment value is increased in a positive region as the road surface gradient calculated by the road surface gradient calculating means is larger on the uphill side. It is preferable that the shift down compulsory decision unit is configured so as to perform determination processing based on the acceleration determination value corrected by the determination value correction unit.
Even if the vehicle is gradually accelerating while traveling on a steep uphill road, it may be stalled after that. As the acceleration judgment value is increased as a positive value in accordance with the increase in the road surface gradient, the downshift is approved even if the vehicle acceleration is a positive value on a steep uphill road, that is, a slow acceleration, Vehicle stall can be prevented.

As another aspect, it is desirable to set the acceleration determination value to 0.
When the vehicle acceleration is less than 0, that is, when the vehicle is decelerating, it is determined that the requirements regarding the vehicle acceleration are satisfied.

  According to the present invention, while avoiding the adverse effects of drivability deterioration and fuel consumption deterioration on flat roads, the driver feels positive by performing a downshift actively in a driving situation where gradual uphill roads continue. Can be eliminated.

1 is an overall configuration diagram showing a drive system of a track to which an automatic transmission control device of an embodiment is applied. It is a flowchart which shows the forced downshift control routine which ECU of embodiment performs. It is the time chart which compared the execution condition of the speed-change control when a gentle uphill road continues in the embodiment and the prior art. It is a figure which shows the map for setting determination time based on the vehicle acceleration applied to 2nd Embodiment. It is a figure which shows the map for setting an acceleration determination value based on the road surface gradient applied to 3rd Embodiment.

Hereinafter, an embodiment of a control device for an automatic transmission embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a track drive system to which an automatic transmission control device of this embodiment is applied.
A vehicle is equipped with a diesel engine (travel power source: hereinafter referred to as an engine) 1 as a travel power source. The input shaft 3a of the automatic transmission 3 is connected to the output shaft 1b of the engine 1 via the clutch device 2, and the rotation of the engine 1 is transmitted to the automatic transmission 3 when the clutch device 2 is connected. . The automatic transmission 3 is based on a stepped manual transmission having six forward speeds and one reverse speed. As described below, the automatic transmission 3 includes a clutch device 2 associated with the speed change operation and the speed change. The connection / disconnection operation is automated.

The clutch device 2 is configured as a friction clutch that is connected to the flywheel 4 by press-contacting the clutch plate 5 with a pressure spring 6 and is disconnected by separating the clutch plate 5 from the flywheel 4. A clutch cylinder 8 (actuator) is connected to the clutch plate 5 via an outer lever 7, and an air tank 11 filled with compressed air is connected to the clutch cylinder 8 via an air passage 10 in which an electromagnetic valve 9 is interposed. Yes.
When the electromagnetic valve 9 is opened, compressed air is supplied from the air tank 11 to the clutch cylinder 8 via the air passage 10, and the clutch cylinder 8 is operated to separate the clutch plate 5 from the flywheel 4 via the outer lever 7. The device 2 is switched from the connected state to the disconnected state. On the other hand, when the solenoid valve 9 is closed, the clutch cylinder 8 stops operating due to the stop of the supply of compressed air, so the clutch plate 5 is pressed against the flywheel 4 by the pressure spring 6 and the clutch device 2 is disconnected from the disconnected state. Can be switched to. Thus, the clutch cylinder 8 is actuated according to the opening and closing of the electromagnetic valve 9, and the clutch device 2 can be automatically connected and disconnected.

  The automatic transmission 3 is provided with a gear shift unit 14 for switching the gear position. Although not shown, the gear shift unit 14 includes a plurality of gear-engaging cylinders (actuators) that operate each gear position in the automatic transmission 3 in the gear-engaging direction, and a plurality of gear-release cylinders (actuators) that operate each gear position in the gear-releasing direction. Actuator) and a plurality of solenoid valves for operating each cylinder. The gear shift unit 14 is connected to the above-described air tank 11 via the air passage 12, and compressed air from the air tank 11 is supplied to a corresponding gear engagement cylinder or gear release cylinder according to opening and closing of each electromagnetic valve. As a result, the cylinder is operated to switch the corresponding shift fork, and the shift stage of the automatic transmission 3 is switched accordingly. As described above, the gear-carrying cylinder and the gear-canceling cylinder are operated in accordance with the opening and closing of the electromagnetic valve of the gear shift unit 14, so that the automatic transmission 3 can be automatically shifted.

In the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, an ECU (control unit) equipped with a central processing unit (CPU), a timer counter, etc. 21 is installed, and comprehensive control of the engine 1, the clutch device 2, and the automatic transmission 3 is performed.
On the input side of the ECU 21, an engine rotation speed sensor 22 for detecting the rotation speed Ne of the engine 1, an input shaft rotation speed sensor 23 for detecting the rotation speed Nin of the input shaft 3a of the automatic transmission 3, and a driver's seat are provided. A lever position sensor 24 that detects the operation position of the change lever 13, a shift stroke sensor 25 that detects the shift stroke Gst (representing the gear position) of each shift stage of the automatic transmission 3, and an operation amount θAcc of the accelerator pedal 26. An accelerator sensor 27 to detect (accelerator operation amount detection means), an output shaft rotation speed sensor 28 to detect a rotation speed Nout (proportional to the vehicle speed V) of the output shaft 3b of the automatic transmission 3, and an operation of the foot brake 29 are detected. Brake switch 30, clutch stroke sensor 31 for detecting clutch stroke Cst of clutch device 2, and vehicle Sensors such as an acceleration sensor 32 (acceleration detecting means) for detecting the acceleration G in the longitudinal direction are connected.

  Further, the electromagnetic valve 9 of the clutch device 2 and the electromagnetic valves of the gear shift unit 14 are connected to the output side of the ECU 21, and the fuel injection valve of the engine 1 is connected (not shown). .

  For example, the ECU 21 calculates a fuel injection amount to each cylinder of the engine 1 from a map (not shown) based on the engine rotation speed Ne detected by the engine rotation speed sensor 22 and the accelerator operation amount θAcc detected by the accelerator sensor 27. At the same time, the fuel injection timing is calculated from a map (not shown) based on the engine speed Ne and the fuel injection amount Q. Based on these calculated values, the engine 1 is operated while driving the fuel injection valves of the respective cylinders.

Further, the ECU 21 executes the automatic shift mode when the lever position sensor 24 detects that the change lever 13 is switched to the D range, and the output shaft rotation detected by the accelerator operation amount θAcc and the output shaft rotation speed sensor 28. Based on the speed Nout, a target shift speed is calculated from a shift map (not shown). Then, while opening / closing the electromagnetic valve 9 of the clutch device 2 and operating the clutch device 8 to be connected / disconnected by the clutch cylinder 8, the corresponding electromagnetic valve of the gear shift unit 14 is opened / closed and the corresponding shift is performed by the gear engagement cylinder and the gear release cylinder. Switch fork. As a result, the shift stage of the automatic transmission 3 is switched to the target shift stage, and the vehicle is always driven with an appropriate shift stage.
For example, during traveling on an uphill road, when the output shaft rotational speed Nout (vehicle speed V) gradually decreases and crosses a shift-down line (shift-down determination value) on the shift map, the ECU 21 sets the target gear position to a value on the low gear side. Set down to pass downshift. Further, downshifting is also approved when the vehicle acceleration turns to the negative side and falls below the downshift determination value (shiftdown control means).

  By the way, as described in [Problems to be Solved by the Invention], although the vehicle speed V decreases when a gentle uphill road continues during traveling of the vehicle, the decrease in the vehicle speed is slow. The conventional technique has a problem that the downshift is delayed and gives the driver a sense of rattling. In addition, the technique of Patent Document 1 is not a process that reflects the traveling state of the vehicle at this time, and thus the feeling of rattling cannot be eliminated. Therefore, in the present embodiment, a vehicle traveling condition on a gentle uphill road, more specifically, a traveling condition in which a shift-down delay occurs is determined. In such a case, the vehicle is shifted based on the vehicle speed V or the vehicle acceleration G. Even if down is not approved, measures are taken to force downshift. Hereinafter, a process executed by the ECU 21 for the countermeasure will be described as a first embodiment.

[First Embodiment]
FIG. 2 is a flowchart showing a forced downshift control routine executed by the ECU.
First, in step S2, it is determined whether or not the current automatic transmission 3 is transmitting power (power transmission determining means). When the automatic transmission 3 is executing a shift operation to any one of the gear stages and the driving force from the engine 1 is not transmitted to the driving wheel via the automatic transmission 3 due to the disconnection of the clutch device 2, No A (No) determination is made and the routine is terminated once.
The determination in step S2 aims at accurately determining the vehicle acceleration G in step S10 described later. That is, in step S10, since the determination process is executed based on the vehicle acceleration G when the vehicle is generating the driving force, an appropriate determination process cannot be expected when the automatic transmission 3 is not transmitting power. In order to avoid such a situation, the determination process of step S2 is executed.

  On the other hand, if the determination of Yes (positive) is made in step S2 because the power is being transmitted, the process proceeds to step S4, where it is determined whether or not the accelerator operation amount θacc is greater than or equal to a predetermined accelerator determination value θacc0. For example, if the accelerator determination value θacc0 is 90% and the determination in step S4 is Yes, the accelerator is depressed by the driver in response to a decrease in vehicle speed while the vehicle is traveling on a gentle uphill road. Can be considered. When the determination in step S4 is No, the routine is temporarily terminated.

Further, when the determination in step S4 is Yes, the process proceeds to step S6, and it is determined whether or not the engine speed Ne can be maintained in the green zone even after the upshift. The green zone is a recommended use rotation range desirable in terms of output of the engine 1, fuel consumption, and noise. For example, when the D range is selected, automatic gear shifting is executed so as to keep the engine rotational speed Ne within the recommended use rotational range. Even when the manual range is selected, the driver performs a gear shifting operation so as to keep the engine rotational speed Ne within the recommended use rotational range. The engine speed Ne after the upshift is calculated based on the current engine speed Ne and the gear ratio between the current gear and the gear after the downshift (rotation speed predicting means).
If the engine speed Ne after the upshift is not maintained in the green zone, that is, if the engine speed Ne exceeds the upper limit of the green zone after the upshift, the determination of No is made in step S6. Exit the routine. If the engine speed Ne is maintained in the green zone even after shifting up, the determination of Yes is made in step S6 and the process proceeds to step S8.

  In step S8, it is determined whether or not the actual engine torque output rate R (actual torque output rate) is greater than or equal to a preset output rate determination value R0. The actual engine torque output rate R is calculated as a ratio of the current engine torque T to the maximum torque Tmax of the engine 1 (= T / Tmax × 100) (output rate calculation means). It means that you are driving nearby. For example, 70% is set as the output rate determination value R0, and when the determination in step S8 is No, it is considered that there is a margin in the engine output, and the routine is temporarily terminated.

  When the determination in step S8 is Yes, the process proceeds to step S10, where it is determined whether or not the vehicle acceleration G detected by the acceleration sensor 32 is less than a preset acceleration determination value G0. In this embodiment, since 0 is set as the acceleration determination value G0, when the vehicle acceleration G is a positive value and the vehicle is even slightly accelerated, the determination of No in step S10 is made and the routine is ended. .

If the vehicle acceleration G is a negative value and the vehicle is decelerating, the determination of Yes is made in step S10 and the process proceeds to step S12. In step S12, it is determined whether or not a predetermined determination time T has elapsed since the conditions in steps S2 to S10 were established. When the determination in step S12 is No, the process returns to step S2, and the processes in steps S2 to S12 are repeated again.
Then, if the determination of step T12 is satisfied and the determination of Yes is made in step S12 when the conditions of steps S2 to 10 are satisfied, the routine is ended in step S14 where downshift is allowed. That is, even if the low gear side target gear position is not set due to the decrease in the vehicle speed V or the vehicle acceleration G in the original shift control, the low gear side target gear position is forcibly set.
In the present embodiment, the ECU 21 when executing the above forced downshift control routine functions as a downshift compulsory approval means. Note that the processes in steps S4 and S6 are not necessarily required, and these processes may be omitted.

FIG. 3 is a time chart comparing the execution state of the shift control when the gradual uphill road is continued between the embodiment and the prior art.
For example, when a truck with a large load enters a gentle uphill (point a in FIG. 3), the driver opens the accelerator fully (point b in FIG. 3) in response to a decrease in the vehicle speed V (point b in FIG. 3). V begins to drop. However, since the decrease in the vehicle speed V is slow, in the related art, a considerably long response time is required until the vehicle speed V crosses the downshift line on the shift map (corresponding to the downshift determination value in the figure) and the downshift is executed. Is required (point c in FIG. 3). Even when the vehicle acceleration G is lower than the shift-down determination value, a long response time is similarly required.

On the other hand, in this embodiment, the downshift is approved when the determination time T elapses (point d in FIG. 3), and the downshift is executed promptly. Therefore, the response time from when the driver fully opens the accelerator to when the downshift is actually executed can be greatly shortened.
FIG. 3 shows a case where the conditions of step S2 are satisfied when the accelerator is fully opened and all the conditions of steps S4 to S10 are simultaneously satisfied and counting of the determination time T is started. There is nothing. For example, the establishment of the condition regarding the green zone in step S6 may be slightly delayed. However, if the determination of Yes is made in step S6 due to a decrease in the engine rotation speed Ne, the determination time T starts counting immediately, and the determination time A shift down is passed immediately after the elapse of T.

As described above, in this embodiment, the actual engine torque output rate R is equal to or greater than the output rate determination value R0 (Yes in step S8), and the vehicle acceleration G is achieved even though the engine 1 is operated near the output limit. Is less than the acceleration determination value G0 and the vehicle is decelerating (Yes in Step S10) for the determination time T (Yes in Step S12), the downshift is forcibly allowed (Step S14).
In such a traveling situation, both the vehicle speed V and the vehicle acceleration G decrease slowly, and a considerable time is required until the vehicle speed V and the vehicle acceleration G fall below the respective shift-down determination values. In other words, it can be considered that the driver feels a sense of inconvenience due to the delay of the downshift. In such a driving situation, even if the target gear position on the low gear side is not set by the original shift control, the target gear position on the low gear side is forcibly set by the approval of the shift down. Accordingly, the downshift is performed promptly, and the driver's feeling of shakiness can be eliminated.

  On the other hand, when any of the conditions in steps S2 to S10 is not satisfied, the forced downshift is not executed, and the downshift is executed at a normal timing based on the downshift determination value by the original shift control. Therefore, it is possible to avoid adverse effects caused by changing the setting of the downshift determination value so that downshifting is positively performed, such as a decrease in drivability on a flat road or a deterioration in fuel consumption.

Further, in step S4, it is added as a condition that the accelerator operation amount θacc is not less than the accelerator determination value θacc0. By adding the condition, it is possible to determine whether or not the driver is in a situation where it is easy for the driver to get tired. As a result, it is possible to more accurately determine whether or not the shift is down.
Further, in step S6, it is added on condition that the engine speed Ne can be maintained in the green zone even after the upshift. By adding the condition, it is possible to avoid a situation in which the engine speed Ne exceeds the upper limit of the green zone due to inappropriate shift down, and thus it is possible to maintain a good vehicle running state.

[Second Embodiment]
Next, a second embodiment in which the present invention is embodied in another control device for the automatic transmission 3 will be described. The difference from the first embodiment is that the determination time T is set according to the vehicle acceleration G. The basic configuration shown in FIG. 1 and the processing of the ECU 21 shown in FIG. It is not different from the form. Therefore, the parts having the same configuration are denoted by the same member numbers, the description thereof is omitted, and differences are mainly described.

FIG. 4 is a diagram showing a map for setting the determination time T based on the vehicle acceleration G.
As shown in this figure, the ECU 21 gradually sets the determination time T to the decreasing side as the vehicle acceleration G becomes a large negative value (the vehicle decelerates rapidly) (determination time correcting means). The more the vehicle is decelerating rapidly despite the accelerator fully open, the more quickly it is necessary to shift down in order to prevent the driver from feeling hungry. According to the present embodiment, the determination time T is shortened as the vehicle acceleration G is larger on the negative side. Therefore, the determination of Yes is made more quickly in step S12 of FIG. (Shift down compulsory approval means). Therefore, compared with the first embodiment, the driver's feeling of rattling can be more reliably prevented.

[Third Embodiment]
Next, a third embodiment in which the present invention is embodied in another control device for the automatic transmission 3 will be described. In contrast to the first embodiment in which the acceleration determination value G0 is set to 0, in the present embodiment, the acceleration determination value G0 is variably set in a positive region in accordance with the road surface gradient θ of the uphill road. It is not different from one embodiment. Therefore, the parts having the same configuration are denoted by the same member numbers, the description thereof is omitted, and differences are mainly described.

FIG. 5 is a diagram showing a map for setting the acceleration determination value G0 based on the road surface gradient θ.
The ECU 21 sequentially calculates the road surface gradient θ when the vehicle is traveling (road surface gradient calculating means). The calculation process of the road surface gradient θ is well known and will not be described in detail. For example, the altitude within a predetermined distance along the traveling direction of the road surface on which the vehicle is traveling is based on, for example, GPS information and map information held by the vehicle. What is necessary is just to obtain | require a difference and to calculate road surface gradient (theta) from these predetermined distance and an altitude difference.
When the ECU 21 determines that the vehicle is traveling on an uphill road based on the road surface gradient θ, the ECU 21 sets an acceleration determination value G0 corresponding to the road surface gradient θ based on the map of FIG. 5 (determination value correction means). . Specifically, the acceleration determination value G0 is set to 0 as in the first embodiment in a region where the road surface gradient θ of the uphill road is relatively gentle. Further, in the region where the road surface gradient θ of the uphill road is equal to or greater than a certain value, the acceleration determination value G0 is gradually set to increase in the positive region as the road surface gradient θ increases.

  Even if the vehicle is gradually accelerating while traveling on a steep uphill road, it may be stalled after that. In such a situation, even if the vehicle acceleration G is a positive value, it is desirable to approve downshifts in advance to prevent stalling. According to the present embodiment, the acceleration determination value G0 is increased as a positive value in accordance with an increase in the road surface gradient θ. Therefore, the vehicle acceleration G is a positive value on a steep uphill road, that is, slowly accelerates. Downshift is also approved (shift down forced approval means). Therefore, in addition to the effect of the first embodiment, another effect that the stall of the vehicle on the steep uphill road can be prevented is also obtained.

This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, although applied to a truck in the above embodiment, the present invention is not limited to this and may be applied to a bus or a passenger car.
Moreover, in the said embodiment, although applied to the automatic transmission 3 based on the normal stepped manual transmission, it is not restricted to this. For example, the present invention may be applied to a so-called dual clutch type automatic transmission having two power transmission systems including an odd-numbered shift stage and an even-numbered shift stage.

1 Engine (Power source for running)
3 Automatic transmission 21 ECU
(Shift down control means, power transmission determination means, rotation speed prediction means, determination time correction means,
(Shift down compulsory approval means, output rate calculation means, road surface gradient calculation means, judgment value correction means)
27 Accelerator sensor (accelerator operation amount detection means)
32 Acceleration sensor (acceleration detection means)

Claims (6)

In a control device for an automatic transmission that performs downshifting by downshifting control means in accordance with a decrease in vehicle speed,
Power transmission determining means for determining that the automatic transmission has finished shifting operation and is transmitting power from the driving power source;
Output rate calculating means for calculating an actual torque output rate as a ratio of the current torque to the maximum torque of the driving power source;
Acceleration detecting means for detecting acceleration in the longitudinal direction of the vehicle;
When it is determined that the power transmission is being determined by the power transmission determination unit, the actual torque output rate calculated by the output rate calculation unit is equal to or greater than a preset output rate determination value, and the acceleration detection unit If the detected vehicle acceleration is less than a preset acceleration determination value and the determination time continues, even if the downshift is not approved by the downshift control means, the downshift is forcibly approved. A control device for an automatic transmission, comprising: a forced down decision means. Rotational speed prediction means for calculating the rotational speed of the traveling power source after the downshift by the downshift forced approval means,
The downshift compulsory approval means is based on the calculation result of the rotational speed prediction means even when the requirement for the actual torque output rate and the requirement for the vehicle acceleration are both satisfied for a determination time. 2. The automatic transmission according to claim 1, wherein the downshift is not approved when it is determined that the rotation speed of the driving power source after the downshift cannot be maintained within a preset recommended use rotation range. Control device. Accelerator operation amount detection means for detecting the accelerator operation amount by the driver,
The downshift compulsory approval means is detected by the accelerator operation amount detection means even when the requirement for the actual torque output rate and the requirement for the vehicle acceleration are both satisfied for a determination time. The control apparatus for an automatic transmission according to claim 1 or 2, wherein the shift down is not approved when the accelerator operation amount is less than a preset determination value. Determination time correction means for correcting the determination time to a decrease side as the vehicle acceleration detected by the acceleration detection means increases to the negative side;
4. The control apparatus for an automatic transmission according to claim 1, wherein the downshift compulsory deciding unit executes a determination process based on a determination time after correction by the determination time correction unit. Road surface gradient calculating means for calculating the gradient of the road surface on which the vehicle is traveling;
A determination value correction unit that corrects the acceleration determination value to the increase side in a positive region as the road gradient calculated by the road surface gradient calculation unit is a larger value on the uphill side,
5. The automatic transmission control device according to claim 1, wherein the downshift compulsory deciding unit executes a determination process based on the acceleration determination value corrected by the determination value correcting unit.   5. The automatic transmission control device according to claim 1, wherein 0 is set as the acceleration determination value.

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