JP2022072200A - Vehicle control device - Google Patents

Abstract

To provide a vehicle control device that can prevent a state where a brake is operated from continuing for a long time during operation support for automatically maintaining an actual vehicle speed at a target vehicle speed.SOLUTION: The vehicle control device, when controlling a gear stage of a stepped transmission to a predetermined gear stage, executing fuel cut of an engine and making a brake generate braking force so that total of braking/driving force by a power train and of braking force by the brake is equal to required braking/driving force, performs downshift from the predetermined gear stage to a downshift rear gear stage, in a case S12 (No) where it can be predicted that braking/driving force by the power train accompanying execution of fuel cut in the downshift rear gear stage downshifted from the predetermined gear stage temporarily and in a case S14 (Yes) where a time during which operation of the brake in the predetermined gear stage continues is a prescribed upper limit time or more.SELECTED DRAWING: Figure 3

Description

The present invention relates to a vehicle control device.

Driving assistive techniques such as ACC (Adaptive Cruise Control), ASL (Adjustable Speed Limiter), and CRC (Cruise Control System) that automatically maintain the actual vehicle speed at the target vehicle speed are known. In such driving support, the control driving force by the power train and the braking force by the brake are controlled in order to maintain the actual vehicle speed at the target vehicle speed. For example, when the vehicle is traveling on a downhill road, the required driving force for maintaining the target vehicle speed is lower than the driving force by the power train when the fuel cut of the engine is performed at a predetermined gear stage. , The brake is operated so that the sum of the control driving force by the power train and the braking force by the brake becomes the required control driving force. If the required driving force is further reduced and it is predicted that the driving force will be lower than the fuel cut force in the gear stage downshifted from the current gear stage, the gear stage will continue the fuel cut. Downshift is taking place.

Japanese Unexamined Patent Publication No. 2020-121679

As mentioned above, while the vehicle is traveling on a downhill road, the brakes continue to operate and the actual vehicle speed is maintained at the target vehicle speed, but the required control driving force is the control driving force due to the fuel cut in the gear stage after downshifting. If it does not decrease below, the brake is activated for a long time without downshifting. This may cause vibration.

Therefore, an object of the present invention is to provide a vehicle control device that suppresses the state in which the brake is operated for a long time during driving support that automatically maintains the actual vehicle speed at the target vehicle speed.

The above object is a vehicle control device that provides driving support for automatically maintaining an actual vehicle speed at a target vehicle speed by controlling a power train including an engine and a stepped transmission and a brake, and is controlled by the power train. The gear stage of the stepped transmission is controlled to a predetermined gear stage to execute the fuel cut of the engine and the control by the brake so that the total of the force and the braking force by the brake becomes the required control driving force. When power is being generated, it is predicted that the driving force of the power train due to the execution of the fuel cut in the gear stage after the downshift that has been downshifted from the predetermined gear stage is lower than the required driving force. If possible, when the time during which the brake operation continues in the predetermined gear stage exceeds the predetermined upper limit time, the downshift from the predetermined gear stage to the gear stage after the downshift is performed. It can be achieved by the vehicle control device.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a vehicle control device that suppresses the state in which the brake is operated for a long time during driving support for maintaining the actual vehicle speed at the target vehicle speed.

FIG. 1 is a functional block diagram of a vehicle according to the present embodiment. FIG. 2 is an example of a flowchart showing control driving force control executed by the vehicle control device. FIG. 3 is an example of a flowchart showing control driving force control executed by the vehicle control device. FIG. 4 is a map that defines an upper limit time corresponding to the braking force. FIG. 5 is an example of a timing chart in which a downshift is executed because the required driving force is lower than the fuel cut driving force after the downshift. FIG. 6 is an example of a timing chart when a downshift is executed when the brake duration exceeds the upper limit time.

[Outline configuration of vehicle]
FIG. 1 is a functional block diagram of a vehicle according to the present embodiment. The vehicle is equipped with a vehicle control device 1, a power train 50, and a brake 60. The power train 50 includes a stepped transmission 51 and an engine 52. The stepped transmission 51 is a stepped automatic transmission in which a plurality of gear stages are selectively switched. For example, one of eight forward speeds, one reverse speed, and neutral is selected, and the speed change of each gear stage is selected. Speed conversion is performed according to the ratio. The engine 52 is an internal combustion engine that uses gasoline or the like as fuel, and is a power source for a vehicle that generates a controlling driving force by burning the fuel.

The vehicle control device 1 includes a required acceleration calculation unit 10, a control driving force control unit 20, a power train control unit 30, and a brake control unit 40. The vehicle control device 1 is an ECU (Electronic Control Unit) having a built-in memory and a microcomputer for storing programs and various maps inside, and the function of the control block is realized by this ECU. The required acceleration calculation unit 10, the control driving force control unit 20, the power train control unit 30, and the brake control unit 40 may be realized by separate ECUs, but their boundaries are not limited thereto. The required acceleration calculation unit 10, the control driving force control unit 20, the power train control unit 30, and the brake control unit 40 may be realized by one or a plurality of ECUs having boundaries different from those in FIG. 1.

The required acceleration calculation unit 10 is provided in a driving support device having a function of realizing and maintaining a target vehicle speed such as ACC. The required acceleration calculation unit 10 sets the target vehicle speed based on the information indicating the vehicle and the surrounding state of the vehicle acquired from the vehicle speed sensor, the camera, etc. and the preset information, and maintains the actual vehicle speed at the target vehicle speed. As the control information of, the required acceleration, which is the acceleration generated in the vehicle, is calculated.

The control driving force control unit 20 receives the above-mentioned required acceleration as a request from the required acceleration calculation unit 10, converts the required acceleration into a force generated in the vehicle, and calculates the required driving force. The required driving force is represented by, for example, a value in which the traveling direction of the vehicle is a positive direction. The required driving force can be calculated, for example, based on the required acceleration and the preset weight of the vehicle. In addition, in the calculation, feedback based on the actual vehicle speed acquired from the vehicle speed sensor or the like, correction based on the inclination of the road surface acquired from various sensors, or the like may be performed. Further, the control drive force control unit 20 requests the power train control unit 30 for a braking force or a control drive force which is a driving force based on the required control drive force, or further requests the brake control unit 40 for a braking force. do.

The power train control unit 30 can control the power train 50 to generate a controlling driving force. When generating braking force, the power train control unit 30 cuts the fuel of the engine 52 according to various states of the power train 50 such as the temperature of the engine 52 and the gear stage of the stepped transmission 51 and the value of the braking force. Can be done.

The power train control unit 30 monitors various states of the power train 50, and based on this, the power train 50 is set in each of the current gear stage of the stepped transmission 51 and the gear stage downshifted from the current gear stage. The fuel cut control driving force, which is the control driving force generated when the fuel cut of the engine 52 is executed, is calculated. Further, the power train control unit 30 determines the control content of the power train 50, such as whether to change the gear stage of the stepped transmission 51 or to perform fuel cut of the engine 52 according to the requested control driving force. And generate a controlling driving force.

The brake control unit 40 controls the brake 60 provided in the vehicle to generate braking force on the wheels.

[Controlling force control]
2 and 3 are examples of a flowchart showing control driving force control executed by the vehicle control device 1. In the flowcharts shown in FIGS. 2 and 3, the driving force generated by the vehicle in order to maintain the target vehicle speed is gradually reduced when the vehicle travels on a downhill road, for example, during driving support such as ACC. In some cases, it is executed repeatedly. First, the flowchart shown in FIG. 2 will be described.

The required acceleration calculation unit 10 calculates the required acceleration as described above (step S1). The control driving force control unit 20 calculates the required control driving force as described above based on the required acceleration (step S2). The power train control unit 30 calculates the fuel cut control driving force in the current gear stage of the stepped transmission 51 (step S3). The fuel cut control driving force is the minimum value of the control driving force of the engine 52 when the fuel cut is executed.

The power train control unit 30 determines whether or not the required driving force is lower than the fuel cut driving force calculated in step S3 (step S4). In the case of Yes in step S4, the brake control unit 40 calculates the brake braking force so that the sum of the fuel cut controlled driving force and the brake braking force becomes the required controlled driving force (step S5). Next, the power train control unit 30 executes a fuel cut on the engine 52, and the brake control unit 40 generates a brake braking force on the brake 60 (step S6). Next, the brake control unit 40, which will be described in detail later, starts counting the duration after the brake braking force is generated in the brake 60 (step S7).

If No in step S4, the powertrain control unit 30 generates a required driving force in the powertrain 50 (step S8). In this case, when the required driving force and the fuel cut driving force are substantially the same, the power train control unit 30 causes the engine 52 to execute the fuel cut, and the required driving force is larger than the fuel cut driving force. The engine 52 is driven by starting fuel injection. In either case, if No in step S4, the brake control unit 40 does not operate the brake 60.

In this way, the control driving force of the vehicle can be made to follow the required control driving force, and the vehicle speed can be maintained at the target vehicle speed.

Next, as shown in FIG. 3, the power train control unit 30 calculates the fuel cut control driving force in the gear stage after downshifting from the current gear stage of the stepped transmission 51 (step S11).

The power train control unit 30 determines whether or not the required control driving force is lower than the value obtained by subtracting the predetermined control drive force α from the fuel cut control drive force in the gear stage after the downshift calculated in step 11. Determination (step S12). Here, the predetermined control driving force α is a value larger than zero, but may be zero. Further, the predetermined control driving force α may be a constant value regardless of the gear stage after the downshift, or may be a different value depending on the gear stage after the downshift. In the case of Yes in step S12, the power train control unit 30 executes the downshift of the gear stage of the stepped transmission 51 (step S13).

If No in step S12, the brake control unit 40 determines whether or not the brake duration for which counting has started in step S7 is equal to or longer than the upper limit time β (step S14). Here, the upper limit time β differs depending on the braking force. FIG. 4 is a map defining the upper limit time β corresponding to the braking force. The horizontal axis shows the braking force [N], and the vertical axis shows the upper limit time β [ms]. In the example of FIG. 4, the upper limit time β is specified to be the longest constant value from 0 to a predetermined value of the brake braking force, and the upper limit time β is specified to be shorter as the brake braking force increases, and then the brake braking force is specified. Even if the value increases, the upper limit time β is defined as the shortest constant value. The upper limit time β is set to a time shorter by a predetermined margin with respect to the time when vibration occurs when the brake braking force is generated in the brake 60 during the execution of the fuel cut. The map of FIG. 4 is acquired in advance by an experiment and stored in the memory of the brake control unit 40. The upper limit time β is not limited to the map of FIG. 4, and may be specified so that the upper limit time β gradually or gradually becomes shorter as the braking force increases, for example. Further, instead of such a map, the upper limit time β may be calculated by an arithmetic expression using the braking force as an argument.

If No in step S14, this control ends. If No is determined in step S4 described above and step S8 is executed, and step S7 is not executed and the brake duration is not counted, No is determined in this step S14.

In the case of Yes in step S14, it is considered that there is a high possibility that vibration is generated due to the continuation of the operation of the brake 60, and the power train control unit 30 causes the stepped transmission 51 to perform a downshift (). Step S13).

Here, when No in step S12, the required driving force is larger than the fuel cut driving force after the downshift, and the required driving force is more predetermined than the fuel cut driving force after the downshift. The case where it is smaller by the value of the control driving force α or less is included. When the required driving force is larger than the fuel cut driving force after the downshift, the engine 52 returns from the fuel cut after the downshift and combustion is started, and the operation of the brake 60 is released. If the required driving force is smaller than the fuel cut driving force after the downshift by a value equal to or less than the predetermined driving force α, the fuel cut is continued after the downshift and the braking force is higher than before the downshift. Is controlled to a small value, and the operation of the brake 60 is continued. In this case, the counting of the brake duration is continued, and the downshift may be performed again based on the upper limit time β corresponding to the brake braking force controlled to a small value again.

As described above, in the case of No in step S12, the fuel cut is continued and the improvement of the fuel consumption is ensured, but the operation of the brake 60 is continued and there is a possibility that vibration is generated due to this. Therefore, in this embodiment, when the braking duration becomes the upper limit time β or more, the downshift is performed to improve the fuel efficiency and suppress the vibration at the same time.

FIG. 5 is an example of a timing chart in which a downshift is executed because the required driving force is lower than the fuel cut driving force after the downshift. FIG. 5 shows changes in the slope of the road on which the vehicle is traveling, the actual vehicle speed, the target vehicle speed, the required driving force, the fuel cut driving force, and the gear stage of the stepped transmission 51. The actual vehicle speed is shown by a solid line, the target vehicle speed is shown by a dotted line, the required driving force is shown by a thick line, and the fuel cut driving force is shown by a thin line.

In the example shown in FIG. 5, at time T0, the road on which the vehicle is traveling becomes a downhill road, and thereafter, the slope representing the positive climb gradually decreases (the slope of the descent increases), and the actual vehicle speed is the target vehicle speed. It shows the case where the required driving force for maintaining is gradually reduced. Although these are represented by constant values in FIG. 5 as an example, they may actually vary depending on the operation of the driving support device and the state of the power train 50. Similar processing is possible even when these values fluctuate.

At time T0, the gear stage of the stepped transmission 51 is controlled to 7th speed as an example. Before time T1, the power train control unit 30 keeps the gear stage of the stepped transmission 51 at the current gear stage (7th speed), and the power train 50 is required to drive without executing the fuel cut of the engine 52. The brake control unit 40 does not generate a braking force on the brake 60 (step S8).

At time T1, the power train control unit 30 executes the fuel cut of the engine 52 while keeping the gear stage of the stepped transmission 51 in the current gear stage (7th speed), and causes the power train 50 to perform the current gear stage (7). The fuel cut control driving force (speed) is generated, and the brake control unit 40 does not generate a braking force on the brake 60 (step S8).

When the required driving force becomes less than or equal to the fuel cut driving force when the gear stage is in 7th gear after the time T1, the power train control unit 30 continues the fuel cut in the engine 52, and the brake control unit 40 brakes. At 60, a braking force corresponding to the difference between the required driving force and the fuel cut driving force of the current gear stage (7th gear) is generated (step S6). In FIG. 5, the hatched region where the required driving force is lower than the fuel cut driving force corresponds to the braking braking force.
The operation of the brake 60 is continued.

After time T2, the required control driving force becomes lower than the value obtained by subtracting the predetermined control drive force α from the fuel cut control drive force when the gear stage is 6th gear (Yes in step S12), and the power train control The unit 30 executes the downshift of the stepped transmission 51 (step S13).

Further, after time T2, the required control driving force is equal to or greater than the value obtained by subtracting the predetermined control drive force α from the fuel cut control drive force of the gear stage (5th speed) downshifted from the current gear stage (6th speed). During that time (No in step S12), the powertrain control unit 30 executes a fuel cut with the engine 52 while keeping the gear stage of the stepped transmission 51 at the current gear stage (6th speed), and executes the fuel cut to the current gear stage (6th speed). The fuel cut control drive force of 6th gear) is generated, and the brake control unit 40 generates a braking force corresponding to the difference between the required control drive force and the fuel cut control drive force of the current gear stage in the brake 60 (step S6). ).

Even after that, when the required driving force gradually decreases, the downshift is repeated in a state where the fuel cut is continuously executed, and the fuel cut and the operation of the brake 60 can be continued.

The powertrain control unit 30 can also calculate the fuel cut control driving force in the gear stages downshifted by two or more stages from the current gear stage, and when the required control drive force suddenly decreases, the fuel cut is cut. The braking force of the brake 60 is generated so that the actual driving force, which is the sum of the fuel-cut driving force generated by the power train 50 and the braking force of the brake 60, matches the required driving force. If possible, the stepped transmission 51 may be downshifted by two or more steps.

FIG. 6 is an example of a timing chart in which a downshift is executed when the brake duration becomes the upper limit time β or more. FIG. 6 shows changes in the slope of the road on which the vehicle is traveling, the actual vehicle speed, the target vehicle speed, the required driving force, the fuel cut driving force, and the gear stage of the stepped transmission 51, as in FIG. ing.

In the example shown in FIG. 6, at time T01, the road on which the vehicle is traveling becomes a downhill road, and thereafter, the slope representing the positive climb gradually decreases (the slope of the descent increases), and the target vehicle speed is achieved. The required driving force of is gradually reduced. At time T01, the gear stage of the stepped transmission 51 is 7th speed as an example. At time T11, the required driving force becomes equal to the fuel cut driving force when the gear stage is in 7th gear. After that, at time T21, the duration from time T11 becomes the upper limit time β, and the power train control unit 30 executes the downshift of the stepped transmission 51. Although these are represented by constant values in FIG. 6 as an example, the same processing can be performed even when these values fluctuate.

For the time T11 and the period from the time T11 to the time T21, the same processing as the period from the time T1 to the time T2 is performed at the time T1 shown in FIG. 5, respectively.

In the vicinity of time T21, unlike the vicinity of time T2 shown in FIG. 5, the gradient is not small. Therefore, at time T21, the required driving force is not lower than the fuel cut driving force after the downshift (No in step S12), but the duration from the time T11 when the brake 60 starts operating is the upper limit. When the time β is exceeded (Yes in step S14), the power train control unit 30 executes the downshift of the stepped transmission 51 (step S13).

Further, since the fuel cut control driving force becomes lower than the required control drive force after the time T21 (No in step S4), the power train control unit 30 restarts the fuel injection in the engine 52 and returns from the fuel cut. The brake control unit 40 does not operate the brake 60 (step S8). As described above, it is possible to suppress the generation of vibration due to the continuous operation of the brake 60 for a long time.

In the above embodiment, the power train control unit 30 determines the control driving force to be generated in the power train 50, but the present invention is not limited to this, and the control drive force control unit 20 determines the control drive force to be generated in the power train 50. You may.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

1 Vehicle control device 10 Required acceleration calculation unit 20 Control driving force control unit 30 Powertrain control unit 40 Brake control unit 50 Powertrain 51 Stepped transmission 52 Engine 60 Brake

Claims (1)

It is a vehicle control device that provides driving support that automatically maintains the actual vehicle speed at the target vehicle speed by controlling the power train including the engine and stepped transmission and the brake.
The fuel cut of the engine is executed by controlling the gear stage of the stepped transmission to a predetermined gear stage so that the sum of the control driving force by the power train and the braking force by the brake becomes the required control driving force. In addition, when the braking force by the brake is generated, the control driving force of the power train by executing the fuel cut in the gear stage after the downshift that is downshifted from the predetermined gear stage is the required control drive. When it can be predicted that the force is lower than the force, the downshifted gear from the predetermined gear stage when the time during which the brake operation is continued in the predetermined gear stage exceeds the predetermined upper limit time. A vehicle control device that downshifts to a gear.

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