Driving force control device

Abstract

The present invention provides a driving force control device, which can control the driving force of a vehicle to an arbitrary value while suppressing the load of the brake. The driving force control device comprises: a required driving force calculation unit, which calculates the required driving force required by the vehicle in a coasting state in which the driver does not operate the accelerator and the brake; a transmission system control unit, which controls the gear ratio of the transmission system based on the required driving force and the driving force achieved by the transmission system in the coasting state; a braking force calculation unit, which calculates the braking force required to achieve the required driving force when the required driving force is smaller than the driving force achieved by the transmission system at the gear ratio set by the transmission system control unit; and a brake control unit, which causes the brake to generate the braking force calculated by the braking force calculation unit.

Description

Technical Field

[0001] The present invention relates to a driving force control device for controlling the driving force of a vehicle. Background Art

[0002] Japanese Patent Application Laid-Open No. 2012-192875 discloses a driving assistance device that performs a constant speed driving control for maintaining a constant vehicle speed when the vehicle is traveling downhill with the brake pedal in an OFF state and the accelerator opening not greater than a predetermined threshold value. In the driving assistance device disclosed in Japanese Patent Application Laid-Open No. 2012-192875, when the total tire braking force calculated based on engine braking and running resistance is insufficient relative to the required braking force required for the vehicle to travel at a set constant speed, the speed change is limited by compensating for the insufficient braking force using the brake, thereby alleviating discomfort caused by torsional vibration or vibration during the constant speed driving control.

[0003] As described in Japanese Patent Application Laid-Open No. 2012-192875, when coasting downhill, if the brakes generate the required braking force without downshifting, the brake effectiveness may be reduced due to a fading phenomenon if the load on the brakes is too large. Summary of the invention

[0004] An object of the present invention is to provide a driving force control device capable of controlling the driving force of a vehicle to an arbitrary value while suppressing the load on a brake.

[0005] A driving force control device according to one embodiment of the present invention is used to control the driving force of a vehicle equipped with a transmission system and a brake, and comprises: a required driving force calculation unit, which calculates the required driving force required by the vehicle in a coasting state in which the driver does not operate the accelerator and the brake; a transmission system control unit, which controls the speed ratio of the transmission system based on the required driving force and the driving force achieved by the transmission system in the coasting state; a braking force calculation unit, which calculates the braking force required to achieve the required driving force when the required driving force is smaller than the driving force achieved by the transmission system at the speed ratio set by the transmission system control unit; and a brake control unit, which causes the brake to generate the braking force calculated by the braking force calculation unit.

[0006] According to one embodiment of the present invention, it is possible to provide a driving force control device that can control the driving force of a vehicle to an arbitrary value while suppressing the load on the brake.

[0007] The above and other objects, features, aspects and effects of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1This is a functional block diagram of a driving force control device according to the embodiment.

[0009] Figure 2 It is used to illustrate Figure 1 A diagram showing an overview of driving force control performed by a driving force control device shown.

[0010] Figure 3 It is shown Figure 1 A flowchart of an example of a control process executed by the driving force control device shown.

[0011] Figure 4 is shown with Figure 3 Flowchart of a portion of a continuous control process. DETAILED DESCRIPTION

[0012] (Overview of one embodiment of the present invention)

[0013] In order to replace the suppression of downshifting as described in Japanese Patent Application Laid-Open No. 2012-192875, it is also considered to control the speed by controlling the transmission. However, in a vehicle equipped with a stepped automatic transmission (AT), since the braking force generated by the AT is discontinuous, it is difficult to keep the vehicle speed constant by controlling the transmission. In addition, when a large braking force is required, there is also a problem that vibration and noise are generated by the increase in engine speed, which makes the user feel irritated.

[0014] A driving force control device according to an embodiment of the present invention changes the transmission ratio in a coasting state in which the driver does not operate the accelerator or the brake, so that the driving force generated by the transmission system increases or decreases according to the required driving force, and the brake generates the missing braking force. By coordinately controlling the transmission ratio and the brake of the transmission system, the desired required driving force can be achieved while reducing the load on the brake.

[0015] The speed ratio of the transmission system can be set to a plurality of predetermined levels, and a specified first threshold and a second threshold are set in each of the plurality of levels, wherein the first threshold is smaller than the driving force achieved by the transmission system, and the second threshold is smaller than the achieved driving force but larger than the first threshold. The transmission system control unit can downshift the speed ratio of the transmission system by one level when the required driving force is smaller than the first threshold, and can upshift the speed ratio of the transmission system by one level when the required driving force is larger than the second threshold.

[0016] According to the above-described configuration, the speed ratio of the powertrain can be appropriately controlled in accordance with the required driving force.

[0017] The required driving force calculation unit may calculate the required driving force based on a deviation between the required acceleration and the actual acceleration.

[0018] According to the above configuration, the responsiveness of the control for realizing the required driving force can be improved.

[0019] (Details of Implementation Method)

[0020] <Composition>

[0021] Figure 1 This is a functional block diagram of a driving force control device according to the embodiment.

[0022] The driving force control device 1 is a device for controlling the driving force of a vehicle having a transmission system 11 and a brake 12, and has a required driving force calculation unit 2, a transmission system control unit 3, a braking force calculation unit 4, and a brake control unit 5. In addition, the transmission system 11 is sometimes also referred to as a drive transmission system. In this embodiment, an example in which the transmission system 11 includes an engine and a stepped automatic transmission (AT) is described, but in a vehicle having a continuously variable transmission (CVT) instead of an AT, when the CTV is used as a stepped transmission, the driving force control device involved in this embodiment can also be applied.

[0023] If it is detected that the vehicle is in a coasting state in which the driver has not performed either accelerator operation or brake operation, the required driving force calculation unit 2 calculates the required driving force Fx* required for the vehicle. The required driving force Fx* can be calculated based on the deviation between the required acceleration Gx* and the actual acceleration measurement value, that is, the actual acceleration Gx. By calculating the required driving force Fx* based on the deviation between the required acceleration Gx* and the actual acceleration Gx, the responsiveness of the driving force control can be improved. Here, the required driving force calculation unit 2 can also calculate the required acceleration Gx* based on the deviation between the requested speed Vx* requested from the driving assistance system and the actual speed measurement value, that is, the actual speed Vx. Alternatively, the required driving force calculation unit 2 can also obtain the required acceleration Gx* calculated by the driving assistance system and the like.

[0024] The transmission system control unit 3 controls the transmission system's gear ratio based on the required driving force Fx* calculated by the required driving force calculation unit 2 and the driving force Fxmin achieved by the transmission system in the coasting state. The driving force Fxmin achieved by the transmission system in the coasting state is the driving force achieved when the accelerator is fully closed at the current gear ratio (gear position) (the minimum driving force at the current gear ratio). In addition, the details of the gear ratio control performed by the transmission system control unit 3 will be described later.

[0025] In the case where the required driving force Fx* calculated by the required driving force calculation unit 2 is smaller than the driving force Fxmin achieved when the accelerator is fully closed at the current speed ratio, the braking force calculation unit 4 calculates the brake braking force Fxbrk required to achieve the required driving force. The brake braking force Fxbrk is represented by the following formula. In the case where the driving force of the vehicle is regarded as the force in the forward direction of the vehicle, the braking force used to brake the vehicle is a negative driving force. In the case where the required driving force Fx* is smaller than the driving force Fxmin achieved when the accelerator is fully closed at the current speed ratio, it is necessary to add the braking force (negative driving force) to the driving force Fxmin achieved when the accelerator is fully closed at the current speed ratio. Therefore, the required driving force Fx* is achieved by causing the brake 12 to generate the brake braking force Fxbrk as the insufficient amount of braking force that the transmission system 11 cannot generate during coasting.

[0026] Fxbrk=Fx*-Fxmin

[0027] The brake control unit 5 controls the brake 12 so that the brake 12 generates the braking force Fxbrk calculated by the braking force calculation unit 4 .

[0028] Figure 2 It is used to illustrate Figure 1 FIG. 1 is a diagram showing an overview of the driving force control performed by the driving force control device shown in FIG. Figure 2 In FIG. 1 , the thick solid line represents the change of the required driving force Fx* over time, the thick long dashed line represents the change of the driving force Fxmin achieved by the transmission system 11 over time, and the thick short dashed line represents the change of the braking force Fxbrk generated by the brake over time. In addition, Figure 2 The sixth gear full-off driving force, the fifth gear full-off driving force, and the fourth gear full-off driving force shown are respectively equivalent to the driving force Fxmin achieved by the transmission system 11 when the accelerator is fully closed at the sixth gear ratio, the fifth gear ratio, and the fourth gear ratio.

[0029] Figure 2 The graph of the required driving force Fx* shows the following example, that is, after the vehicle enters a downhill road, it becomes a coasting state without accelerator operation and brake operation, and the required driving force decreases over time (the required braking force increases) in order to maintain the vehicle speed constant. The transmission control unit 3 performs a downshift to achieve a change in the speed ratio as the required driving force Fx* decreases, so that Figure 2As shown by the thick long dashed line, the driving force generated by the transmission system 11 is reduced (the braking force is increased). However, since the magnitude of the driving force that can be achieved by the speed ratio control of the transmission system 11 is discontinuous, it is difficult to achieve the required driving force only by controlling the transmission system 11 by the transmission system control unit 3. Therefore, in this embodiment, the brake control unit 4 controls the brake 12 in coordination with the control of the transmission system 11 by the transmission system control unit 3, thereby generating Figure 2 As a result, it is possible to generate a required driving force of any value based on the sum of the driving force achieved by the transmission system 11 and the braking force generated by the brake 12.

[0030] The speed ratio control of the transmission system 11 by the transmission system control unit 3 is preferably performed as follows.

[0031] In the case where the speed ratio can be switched in each of the multiple gears, the transmission system control unit 3 sets a first threshold value for downshifting and a second threshold value for upshifting for the value of the required driving force in each gear (speed ratio). The first threshold value can be set, for example, to a value that is reduced by only Fxd compared to the driving force Fxmin achieved by the transmission system 11 when the accelerator is fully closed in each gear. On the other hand, the second threshold value is a value that is smaller by only Fxu than the driving force Fxmin achieved by the transmission system 11 when the accelerator is fully closed in each gear, and is greater than the first threshold value (here, |Fxu|<|Fxd|).

[0032] If the required driving force Fx* becomes a value less than the first threshold value of the current gear, and the state where the required driving force Fx* is less than the first threshold value of the current gear (the state where Fx*<Fxmin-Fxd is satisfied) continues for a predetermined time, the transmission system control unit 3 downshifts the gear of the transmission system 11 by one gear. In addition, if the required driving force Fx* becomes a value greater than the second threshold value of the current gear, and the state where the required driving force Fx* is greater than the second threshold value of the current gear (the state where Fx*>Fxmin-Fxu is satisfied) continues for a predetermined time, the transmission system control unit 3 upshifts the gear of the transmission system 11 by one gear. If downshifting is performed based on the first threshold value, in a situation where the required driving force Fx* decreases over time, such as when driving downhill, the braking force achieved by the transmission control can be used to the maximum extent while downshifting, thereby reducing the load of the brake 12. In addition, if an upshift is performed based on the second threshold, the gear ratio can be switched in advance before the required driving force Fx* exceeds the driving force Fxmin achieved when the accelerator is fully closed in the current gear and the driving force is insufficient, when the required driving force Fx* increases over time for constant speed driving, as when the slope of the downhill slope decreases.

[0033] <Control Processing>

[0034] Below, also refer to Figure 1 , Figure 3 and Figure 4 , the control process of the driving force control device involved in this embodiment is described.

[0035] Figure 3 and Figure 4 It is shown Figure 1 A flowchart of an example of a control process executed by the driving force control device shown. Figure 3 and Figure 4 The control process shown is executed when it is detected that a coasting state has occurred in which the driver has not performed either an accelerator operation or a brake operation.

[0036] Step S1: The required driving force calculation unit 2 calculates the required acceleration Gx*. As described above, the required acceleration Gx* can be calculated based on the deviation between the required speed Vx* requested by the driving assistance system and the actual speed measurement value, that is, the actual speed Vx. In addition, if the required driving force calculation unit 2 can obtain the required acceleration Gx* from the driving assistance system, the processing of step S1 can be omitted. After that, the processing proceeds to step S2.

[0037] Step S2: The required driving force calculation unit 2 calculates the required driving force Fx*. The required driving force Fx* can be calculated based on the deviation between the required acceleration Gx* calculated in step S1 and the actual acceleration Gx, which is the actual acceleration measurement value. Then, the process proceeds to step S3.

[0038] Step S3: The transmission control unit 3 obtains the driving force Fxmin achieved by the transmission 11 when the accelerator is fully closed in the current gear. The transmission control unit 3 can calculate the driving force Fxmin achieved when the accelerator is fully closed in the current gear based on a pre-prepared mapping table or table.

[0039] Step S4: The transmission control unit 3 determines whether the state in which the required driving force Fx* is larger than the driving force Fxmin achieved when the accelerator is fully closed in the current gear position has continued for a predetermined time. The processing of this step S4 is used to determine whether to repeat the coordinated control of the transmission system 11 and the brake 12. If the determination of step S4 is "yes", the processing jumps to step S5, and in other cases, the processing jumps to step S6.

[0040] Step S5: The powertrain control unit 3 turns OFF the flag Flg indicating whether the coordinated control of the powertrain 11 and the brake 12 is being executed. When the flag Flg is ON, it indicates that the coordinated control of the powertrain 11 and the brake 12 is being executed. Then, the process ends.

[0041] Step S6: The powertrain control unit 3 determines whether the flag Flg indicating whether the coordinated control of the powertrain 11 and the brake 12 is being executed is ON. If the determination in step S6 is YES, the process jumps to step S7, otherwise, the process jumps to step S8.

[0042] Step S7: The transmission control unit 3 sets the parameter Sn representing the gear position to the gear position S1 stored after the previous control. When the coordinated control of the transmission system 11 and the brake 12 is in execution, it is possible that the gear position is changed compared to the initial value (the gear position set in the later-described step S8) by downshifting or upshifting in accordance with the value of the required driving force Fx* through the processing of the later-described step S11 or S12. Therefore, in step S7, the gear position S1 stored after the execution of the processing of the later-described steps S10 to S13 is obtained and assigned to Sn. Thereafter, the processing jumps to Figure 4 Step S10 is shown.

[0043] Step S8: The powertrain control unit 3 assigns the current gear position S to the parameter Sn indicating the gear position. Then, the process jumps to step S9.

[0044] Step S9: The transmission control unit 3 turns on the flag Flg indicating whether the coordinated control of the transmission 11 and the brake 12 is being executed. Figure 4 Step S10.

[0045] Step S10: The transmission system control unit 3 determines whether the state where the required driving force Fx* is greater than the first threshold value (Fxmin-Fxd) for downshifting set in the current gear position changes to a state where the required driving force Fx* is less than the first threshold value, and the state where the required driving force Fx* is less than the first threshold value continues for a specified time. In addition, the determination of whether the state where the required driving force Fx* is less than the first threshold value continues for a specified time is to exclude the situation where the state where the required driving force Fx* is greater than the first threshold value and the state where the required driving force Fx* is less than the first threshold value frequently switch in a short period of time, thereby accurately determining the situation where downshifting is required. If the determination in step S10 is "yes", the processing proceeds to step S11, and in other cases, the processing proceeds to step S12.

[0046] Step S11: The transmission control unit 3 shifts down the gear position Sn of the transmission of the transmission 11 by one gear (ie, increases the speed ratio). Thereafter, the process proceeds to step S14.

[0047] Step S12: The transmission system control unit 3 determines whether the state where the required driving force Fx* is less than the second threshold value (Fxmin-Fxu) for upshifting set in the current gear position changes to a state where the required driving force Fx* exceeds the second threshold value, and the state where the required driving force Fx* exceeds the second threshold value continues for a specified time. In addition, the determination of whether the state where the required driving force Fx* exceeds the second threshold value continues for a specified time is to exclude the situation where the state where the required driving force Fx* exceeds the second threshold value and the state where the required driving force Fx* is less than the second threshold value frequently switch in a short period of time, so as to accurately determine the situation where upshifting is required. If the determination in step S12 is "yes", the processing proceeds to step S13, and in other cases, the processing proceeds to step S14.

[0048] Step S13: The transmission control unit 3 shifts the gear position Sn of the transmission of the transmission 11 up one gear (ie, reduces the speed ratio). Thereafter, the process proceeds to step S14.

[0049] Step S14: The powertrain control unit 3 stores the shift position Sn by assigning the parameter S1. Then, the process proceeds to step S15.

[0050] Step S15: The transmission system control unit 3 obtains the driving force Fxmin achieved by the transmission system 11 when the accelerator is fully closed in the current gear. Similar to the process of step S3, the transmission system control unit 3 can calculate the driving force Fxmin achieved when the accelerator is fully closed in the current gear based on a pre-prepared mapping table or table. In addition, if the determination in step S12 is "No" and the gear is not changed, the process of step S15 can also be omitted. Thereafter, the process proceeds to step S16.

[0051] Step S16: The braking force calculation unit 4 calculates the braking force Fxbrk generated by the brake 12 based on the required driving force Fx* and the driving force Fxmin achieved by the transmission system 11 when the accelerator is fully closed in the current gear position obtained in step S15. The braking force Fxbrk can be obtained by the calculation of (Fx*-Fxmin). After that, the process proceeds to step S17.

[0052] Step S17: The brake control unit 5 controls the brake 12 so that the brake 12 generates the braking force Fxbrk calculated in step S16. Figure 3 Step S1.

[0053] <Effects, etc.>

[0054] A driving force control device 1 according to an embodiment of the present invention, in a coasting state where the driver does not operate the accelerator or the brake, changes the speed ratio of the transmission system 11 so that the driving force (braking force) Fxmin generated by the transmission system 11 increases or decreases in accordance with the required driving force Fx*, and uses the brake braking force Fxbrk generated by the brake 12 to compensate for the insufficient braking force, thereby achieving the required driving force Fx*. Compared with the case where the brake 12 is used alone to control the driving force, the load of the brake 12 can be reduced by coordinated control of the speed ratio of the transmission system 11 and the brake 12. In addition, since the brake 12 compensates for the braking force that cannot be achieved by controlling the speed ratio of the transmission system 11 alone, it is possible to suppress torsional vibration and vibration when the speed ratio of the transmission system 11 is changed.

[0055] The present invention can be used as a driving force control device for controlling the driving force of a vehicle.

[0056] The present invention has been described in detail above, but the above description is only an example of the present invention and does not limit the scope of protection of the present invention. Of course, various improvements or modifications can be made without departing from the scope of the present invention.

Claims

1. A control device, mounted on a vehicle, comprising: A receiving unit receives a plurality of accelerations from a driving assistance system; a required driving force calculation unit for calculating a required driving force required by the vehicle in a coasting state in which the driver does not perform an accelerator operation or a brake operation; a transmission system control unit, including a transmission system actuator, which obtains the required driving force and the minimum driving force that can be achieved by the transmission system actuator under the current speed ratio, and controls the speed ratio of the transmission system; and The brake system control unit includes a brake driver, which obtains a braking force required to achieve the required driving force when the required driving force is less than the minimum driving force, and causes the brake to generate the required braking force.

2. A control device, mounted on a vehicle, comprising: a required driving force calculation unit that receives a plurality of requested accelerations from the driving assistance system and calculates a required driving force required by the vehicle in a coasting state in which the driver does not perform an accelerator operation or a brake operation; a transmission system control unit, including a transmission system actuator, which obtains the required driving force and the minimum driving force that can be achieved by the transmission system actuator under the current speed ratio, and controls the speed ratio of the transmission system; and The brake system control unit includes a brake driver, which obtains a braking force required to achieve the required driving force when the required driving force is less than the minimum driving force, and causes the brake to generate the required braking force.

3. A system comprising a control device mounted on a vehicle, a transmission system including a transmission system actuator, and a brake system including a brake actuator, wherein: The control device has: A receiving unit receives a plurality of accelerations from a driving assistance system; a required driving force calculation unit for calculating a required driving force required by the vehicle in a coasting state in which the driver does not perform an accelerator operation or a brake operation; A transmission system control unit, including a transmission system actuator, obtains the required driving force and the minimum driving force that can be achieved by the transmission system actuator under the current speed ratio, and controls the speed ratio of the transmission system; as well as The brake system control unit includes a brake driver, which obtains a braking force required to achieve the required driving force when the required driving force is less than the minimum driving force, and causes the brake to generate the required braking force.

4. A control method, which is executed by a control device mounted on a vehicle, The control method includes: the step of receiving a plurality of accelerations from a driver assistance system; The step of calculating the required driving force required by the vehicle in a coasting state in which the driver does not operate the accelerator or the brake; the step of obtaining the required driving force and the minimum driving force that can be achieved by the transmission system actuator under the current gear ratio by a transmission system control unit of the transmission system actuator, and controlling the gear ratio of the transmission system; as well as When the required driving force is less than the minimum driving force, a brake system control unit including a brake driver obtains a braking force required to achieve the required driving force and causes a brake to generate the required braking force.

5. A vehicle comprising the control device according to claim 1.

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