Control device for a vehicle

Abstract

The present disclosure relates to a control device for a vehicle. A vehicle includes: a motor generator as a drive source; an automatic transmission via which the motor generator is connected with a drive wheel, the automatic transmission being configured to change a speed ratio; and a shift actuator for a driver to operate the speed ratio of the automatic transmission. A control device for a vehicle includes: a motor control section configured to control an output torque of the motor generator; and a shift control section configured to control the speed ratio of the automatic transmission. In a case where the output torque has a negative value, when a downshift is not requested by an operation of the shift actuator, the shift control section prohibits a downshift process of causing the speed ratio of the automatic transmission to downshift, but when a downshift is requested by the operation of the shift actuator, the shift control section allows execution of the downshift process.

Description

Technical Field

[0001] This invention relates to a control device for vehicles. Background Technology

[0002] Japanese Unexamined Patent Application Publication No. 2010-252584 (JP 2010-252584 A) describes a vehicle that includes an internal combustion engine and an automatic transmission. Furthermore, JP 2010-252584 A describes a technology for manufacturing so-called electric vehicles by replacing the vehicle's internal combustion engine with an electric generator as the drive source. Summary of the Invention

[0003] As a control for electric vehicles, a control is known that causes the gear ratio of an automatic transmission to automatically downshift when the vehicle decelerates. Furthermore, a control is known that controls the torque of the electric generator according to the downshifting of the gear ratio, thereby suppressing so-called shift shock, i.e., fluctuations in vehicle acceleration accompanying the downshifting.

[0004] Furthermore, in electric vehicles manufactured using the technology described in JP 2010-252584 A, it is assumed that various electric generators with different performance characteristics (e.g., different types of electric generators, electric generators with different degrees of aging, etc.) are newly attached electric generators. Even when it is necessary to pre-determine how to control the torque of the electric generator to suppress shift shock, it is difficult to determine an appropriate control method in advance until the performance of the electric generator to be installed is determined. Therefore, when electric vehicles are manufactured by replacing their internal combustion engines with electric generators or by replacing their electric generators with new electric generators, it is difficult to suppress shift shock by using the torque of the electric generator.

[0005] A vehicle control device for addressing this problem is a control device for controlling a vehicle including an electric generator, an automatic transmission, and a shift actuator. The electric generator serves as the vehicle's drive source and is connected to the drive wheels via the automatic transmission, which is configured to change gear ratios. The shift actuator is used by the driver to operate the automatic transmission's gear ratios. The control device includes a motor control unit and a shift control unit. The motor control unit is configured to control the output torque of the electric generator. The shift control unit is configured to control the gear ratios of the automatic transmission. When the output torque is zero or negative, the shift control unit prohibits downshifting when no downshift is requested by operating the shift actuator; however, when a downshift is requested by operating the shift actuator, the shift control unit allows the execution of the downshift.

[0006] In the above configuration, when the output torque of the electric generator is zero or negative—that is, when the electric generator does not provide positive acceleration to the vehicle—the automatic transmission will not downshift unless the driver requests a downshift using the shift actuator. Therefore, in this case, no shift shock occurs. However, when the driver requests a downshift using the shift actuator, the automatic transmission downshifts, which may result in a shift shock. However, since the shift shock occurs in response to the driver's request to downshift, the driver is unlikely to experience the discomfort of an unexpected shift shock.

[0007] In the above configuration, the vehicle may include a mechanical braking device configured to brake the drive wheels, and a brake pedal for the driver to operate the braking device. The control unit may include a brake control unit configured to control the braking force of the braking device based on the amount of brake pedal operation. The motor control unit may control the output torque regardless of the amount of brake pedal operation.

[0008] In the above configuration, the amount of brake pedal operation does not affect the regenerative torque of the electric generator, that is, the negative acceleration supplied to the vehicle by the electric generator. Therefore, there will not be a situation where, even if the amount of brake pedal operation is constant, the negative acceleration induced in the vehicle varies due to differences in the performance of the electric generators connected to the vehicle.

[0009] In the above configuration, after downshifting is performed until the downshifting is completed, the motor control unit can perform torque relaxation processing to reduce the absolute value of the output torque compared to the absolute value of the output torque before the downshifting was performed.

[0010] In the above configuration, the torque transmission efficiency via the automatic transmission changes during downshifting. Therefore, when the absolute value of the output torque is large during downshifting, the fluctuation range of the force transmitted from the electric generator to the drive wheels is likely to increase due to the change in torque transmission efficiency. In the above configuration, the absolute value of the electric generator's output torque decreases during downshifting. Therefore, even when the torque transmission efficiency via the automatic transmission changes during downshifting, excessive increases in the fluctuation range of the force transmitted from the electric generator to the drive wheels can be suppressed.

[0011] In the above configuration, when the absolute value of the output torque is equal to or less than a predetermined threshold, the motor control unit can allow the downshifting process to be executed and control the output torque during the torque relaxation process, so that the output torque is zero.

[0012] In the above configuration, even when torque relaxation processing is performed, the fluctuation range of the output torque does not exceed the threshold. Therefore, the vehicle's acceleration will not change, or the vehicle will not vibrate due to excessive fluctuations in the output torque.

[0013] In the above configuration, after the downshifting process is completed, the motor control unit can perform torque recovery processing: controlling the output torque so that the value of the output torque has the same positive or negative sign as the output torque just before the downshifting process was executed, and its absolute value is less than the absolute value of the output torque just before the downshifting process was executed.

[0014] In the above configuration, the automatic transmission's gear ratio changes upon downshifting, making it easier for the electric generator's speed to increase. Therefore, even when the output torque is the same before and after downshifting, the increased generator speed causes fluctuations in the force transmitted from the generator to the drive wheels via the automatic transmission. This makes shift shock more likely during downshifting. In the above configuration, the output torque is lower after downshifting than before. Therefore, even when the generator's speed increases, fluctuations in the force transmitted from the generator to the drive wheels can be suppressed. Thus, shift shock during downshifting can be minimized. Attached Figure Description

[0015] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0016] Figure 1 It is a schematic diagram of the vehicle's configuration;

[0017] Figure 2 This is a flowchart illustrating downshift control; and

[0018] Figure 3 It is a timing diagram that illustrates the changes in the downshift operation signal, the changes in whether the automatic transmission gear is changed, the changes in the operation amount of the acceleration device, the changes in the target driving force for the vehicle, the changes in the speed of the electric generator, and the changes in the output torque of the electric generator. Detailed Implementation

[0019] Indicative configuration of the vehicle

[0020] The following reference Figures 1 to 3 An embodiment is described. First, a schematic configuration of vehicle 100 is described. Note that vehicle 100 is an electric vehicle obtained by modifying a vehicle that includes an internal combustion engine.

[0021] like Figure 1As shown, vehicle 100 includes an electric generator 10, an automatic transmission 30, a differential 41, and multiple drive wheels 42. The electric generator 10 includes an output shaft 11. The output shaft 11 is connected to the automatic transmission 30. Note that the electric generator 10 serves as the drive source for vehicle 100.

[0022] The automatic transmission 30 is a stepped automatic transmission that includes multiple planetary gear mechanisms. The automatic transmission 30 includes an input shaft 31, an output shaft 32, and multiple clutches 33. Note that... Figure 1 The diagram only shows one of the multiple clutches 33.

[0023] The first end of the input shaft 31 is connected to the output shaft 11. The second end of the input shaft 31 is connected to the first end of the output shaft 32 via a clutch 33. The second end of the output shaft 32 is connected to the left and right drive wheels 42 of the vehicle 100 via a differential 41. The clutch 33 can be switched between an engaged and disengaged state by the hydraulic pressure supplied to the clutch 33. More specifically, when the hydraulic pressure supplied to the clutch 33 increases, the clutch 33 switches from a disengaged state to an engaged state. The maximum torque that can be transmitted via the clutch 33 increases with the increase of the hydraulic pressure supplied to the clutch 33. When the hydraulic pressure supplied to the clutch 33 exceeds a given pressure, the input and output sides of the clutch 33 rotate as a unit. When the clutch to be disengaged and the clutch to be engaged among the multiple clutches 33 are changed, the gear position of the automatic transmission 30 is changed. When the gear position of the automatic transmission 30 is changed, the speed ratio of the automatic transmission 30 is changed.

[0024] The vehicle 100 includes an inverter 21, a battery 22, a hydraulic mechanism 50, and multiple braking devices 55.

[0025] Inverter 21 performs power conversion from direct current (DC) to alternating current (AC) between the electric generator 10 and the battery 22, and vice versa. Furthermore, inverter 21 regulates the output torque from the electric generator 10 by adjusting the amount of power transferred between the electric generator 10 and the battery 22. More specifically, when the electric generator 10 is used as a motor, it provides positive output torque to the drive wheels 42 via the automatic transmission 30 and differential 41. Conversely, when the electric generator 10 is used as a generator, it provides negative output torque to the drive wheels 42 via the automatic transmission 30 and differential 41. Therefore, when the electric generator 10 is used as a generator to decelerate the vehicle 100, it can provide regenerative braking force to the vehicle 100 corresponding to the amount of electricity generated by the electric generator 10.

[0026] Each braking device 55 is positioned near its corresponding drive wheel 42. The braking device 55 is a so-called mechanical braking device configured to mechanically brake the drive wheel 42. An example of the braking device 55 is a disc brake.

[0027] The hydraulic mechanism 50 is configured to supply hydraulic pressure to the automatic transmission 30. The hydraulic mechanism 50 operates the engagement and disengagement of each clutch 33 by controlling the hydraulic oil to be supplied to each clutch 33.

[0028] Vehicle 100 includes an accelerator pedal 61, a brake pedal 62, a gear shift lever 63, an upshift switch 66, and a downshift switch 67. Accelerator pedal 61 is used by the driver to accelerate vehicle 100. Brake pedal 62 is used by the driver to operate the braking device 55.

[0029] The gear shift lever 63 is a lever used by the driver to change the driving state of the vehicle 100. The driver performs a shift operation on the gear shift lever 63. Here, the driving state to be changed by the gear shift lever 63 includes parking, neutral, forward, and reverse. When the vehicle 100 is in the parking or neutral driving state, a non-driving gear mode is executed in the automatic transmission 30. When the vehicle 100 is in the forward or reverse driving state, a driving gear mode is executed in the automatic transmission 30.

[0030] Specifically, when the vehicle 100 is in forward motion, ten gears, from "1st" to "10th," can be established in the automatic transmission 30. When a gear in the automatic transmission 30 is changed, the gear ratio of the automatic transmission 30 is set to a gear ratio predetermined for each gear. Here, the gear ratio of the automatic transmission 30 represents a ratio that indicates the number of rotations of the input shaft 31 in one rotation of the output shaft 32. The gear ratio of the automatic transmission 30 decreases as the gear increases.

[0031] Upshift switch 66 is used to operate a so-called upshift, whereby the driver increases the gear of the automatic transmission 30. Note that, as described above, when the gear of the automatic transmission 30 increases, the gear ratio of the automatic transmission 30 decreases. Downshift switch 67 is used to operate a so-called downshift, whereby the driver decreases the gear of the automatic transmission 30. Note that, as described above, when the gear of the automatic transmission 30 decreases, the gear ratio of the automatic transmission 30 increases. In this embodiment, downshift switch 67 is an example of a shift actuator. Note that upshift switch 66 and downshift switch 67 can also be referred to as shift paddles.

[0032] The vehicle 100 includes an acceleration device operation quantity sensor 71, a brake operation quantity sensor 72, a lever position sensor 73, an input-side speed sensor 76, and an output-side speed sensor 77.

[0033] An accelerator operation amount sensor 71 is placed near the accelerator pedal 61. The accelerator operation amount sensor 71 detects the accelerator operation amount ACC as the amount of operation of the accelerator pedal 61 to be operated by the driver.

[0034] A brake operation amount sensor 72 is placed near the brake pedal 62. The brake operation amount sensor 72 detects the brake operation amount BRA as the amount of operation of the brake pedal 62 to be operated by the driver.

[0035] A lever position sensor 73 is placed near the shift lever 63. The lever position sensor 73 detects the lever position LP as the operating position of the shift lever 63 to be operated by the driver.

[0036] An input-side speed sensor 76 is placed near the input shaft 31. The input-side speed sensor 76 detects the input-side speed NIN as the speed of the input shaft 31. An output-side speed sensor 77 is placed near the output shaft 32. The output-side speed sensor 77 detects the output-side speed NOUT as the speed of the output shaft 32.

[0037] Vehicle 100 includes a control unit 80. The control unit 80 receives a signal from the accelerator operation quantity sensor 71 indicating the accelerator operation quantity ACC. The control unit 80 receives a signal from the brake operation quantity sensor 72 indicating the brake operation quantity BRA. The control unit 80 receives a signal from the lever position sensor 73 indicating the lever position LP. The control unit 80 receives a signal from the input-side speed sensor 76 indicating the input-side speed NIN. The control unit 80 receives a signal from the output-side speed sensor 77 indicating the output-side speed NOUT. The control unit 80 receives a signal from the upshift switch 66 indicating the operation of the upshift switch 66. The control unit 80 receives a signal from the downshift switch 67 indicating the operation of the downshift switch 67. Furthermore, the control unit 80 calculates the vehicle speed SP as the speed of vehicle 100 based on the output-side speed NOUT.

[0038] The control device 80 includes a drive force calculation unit 81, a motor control unit 82, a gear shift control unit 83, and a brake control unit 84.

[0039] The drive force calculation unit 81 calculates the target drive force A as the target value of the drive force for driving the vehicle 100. Note that the drive force for driving the vehicle 100 used here refers to the torque of the drive wheel 42. For example, the torque of the drive wheel 42 is calculated by multiplying the output torque of the electric generator 10, the speed ratio of the automatic transmission 30, and the reduction ratio from the output shaft 32 to the drive wheel 42. The drive force calculation unit 81 calculates the target drive force A based on the acceleration device operation amount ACC and the vehicle speed SP. When the drive force calculation unit 81 determines that the driver requests the vehicle 100 to accelerate, the drive force calculation unit 81 calculates the target drive force A as a positive value. For example, at the same vehicle speed SP, as the acceleration device operation amount ACC is larger, the drive force calculation unit 81 calculates a larger value as the target drive force A. Furthermore, when the drive force calculation unit 81 determines that the driver requests the vehicle 100 to decelerate, the drive force calculation unit 81 calculates the target drive force A as a negative value. For example, at the same vehicle speed SP, as the acceleration device operation amount ACC decreases, the drive force calculation unit 81 calculates a smaller value as the target drive force A. Furthermore, for example, at the same acceleration device operation amount ACC, as the vehicle speed SP increases, the drive force calculation unit 81 calculates a smaller value as the target drive force A. In other words, when the acceleration device operation amount ACC is less than a given value, the target drive force A becomes negative, thereby causing the vehicle to decelerate at 100.

[0040] The shift control unit 83 selects a gear for the automatic transmission 30 based on the accelerator operation amount ACC and the vehicle speed SP. A gear ratio mapping associated with the accelerator operation amount ACC and the vehicle speed SP, indicating the gear to be set by the automatic transmission 30, is pre-stored in the shift control unit 83. For example... Figure 1 As shown, in the gear ratio mapping, with the same accelerator pedal operation amount (ACC), a higher gear is selected as the vehicle speed (SP) increases. Furthermore, with the same vehicle speed (SP), a lower gear is selected as the accelerator pedal operation amount (ACC) increases. The shift control unit 83 outputs a control signal to the hydraulic mechanism 50 based on the gear selected for the automatic transmission 30. Then, the shift control unit 83 changes the gear of the automatic transmission 30 by operating the engagement and disengagement states of the clutch 33 via the hydraulic mechanism 50. Therefore, the automatic transmission 30 can automatically change the gear ratio without relying on the driver's operations on the upshift switch 66 and downshift switch 67.

[0041] Furthermore, the shift control unit 83 selects a gear for the automatic transmission 30 based on signals instructing the operation of the upshift switch 66 and downshift switch 67. For example, when the upshift switch 66 is operated by the driver, the shift control unit 83 selects a higher gear as the gear of the automatic transmission 30. Similarly, when the downshift switch 67 is operated by the driver, the shift control unit 83 selects a lower gear as the gear of the automatic transmission 30. The shift control unit 83 outputs a control signal to the hydraulic mechanism 50 according to the gear selected for the automatic transmission 30, thereby changing the gear of the automatic transmission 30 to the selected gear. Therefore, the automatic transmission 30 can also change its gear ratio in response to the driver's operation of the upshift switch 66 and downshift switch 67. Note that the shift control unit 83 selects a gear based on a gear ratio mapping after a given time period has elapsed since the last input signal instructing operation on the upshift switch 66 or downshift switch 67.

[0042] The shift control unit 83 calculates the value obtained by dividing the input-side speed NIN by the output-side speed NOUT. Furthermore, the gear ratio determined for each gear in the automatic transmission 30 is pre-stored in the shift control unit 83. When the difference between the value calculated above and the gear ratio corresponding to the gear to which the automatic transmission 30 is changed is below a specific value, the shift control unit 83 determines that the gear change of the automatic transmission 30 is complete.

[0043] The motor control unit 82 calculates the target output torque B as the target value of the output torque that rotates the output shaft 11 of the electric generator 10. The motor control unit 82 calculates the target output torque B based on the target driving force A and the speed ratio of the automatic transmission 30. In addition, the motor control unit 82 outputs a control signal to the inverter 21 according to the target output torque B, and the motor control unit 82 controls the output torque of the electric generator 10 via the inverter 21.

[0044] Here, when the target driving force A is positive, i.e., when the vehicle 100 is requested to accelerate, the motor control unit 82 calculates a positive value as the target output torque B. In this case, the motor control unit 82 uses the electric generator 10 as a motor.

[0045] Furthermore, when the target driving force A is negative, i.e., when a request is made to decelerate the vehicle 100, the motor control unit 82 calculates a negative value as the target output torque B. In this case, the motor control unit 82 uses the electric generator 10 as a generator.

[0046] Note that the motor control unit 82 does not control the output torque of the electric generator 10 based on the brake operation amount BRA. In other words, the motor control unit 82 controls the output torque of the electric generator 10 without taking the brake operation amount BRA into account.

[0047] The brake control unit 84 controls the braking force of the brake device 55 based on the brake operation amount BRA. More specifically, as the brake operation amount BRA increases, the brake control unit 84 increases the braking force of the brake device 55.

[0048] Note that the control device 80 may be configured as a circuit including one or more processors configured to perform various processes according to a computer program (software). Note that the control device 80 may be configured as one or more special-purpose hardware circuits (e.g., application-specific integrated circuits (ASICs) configured to perform at least some of the various processes) or a combination thereof. The processor includes a CPU and memory (such as RAM or ROM). Program code or commands configured to cause the CPU to perform processes are stored in the memory. This memory, i.e., computer-readable medium, includes all available media accessible to a general-purpose computer or a special-purpose computer.

[0049] Downshift control

[0050] The downshift control to be performed by control device 80 will be described next. Control device 80 repeatedly performs the downshift control after driving begins but before driving ends.

[0051] like Figure 2 As shown, when downshift control begins, the shift control unit 83 executes step S11. In step S11, the shift control unit 83 determines whether the target output torque B is equal to or less than "0". If, in step S11, the shift control unit 83 determines that the target output torque B is greater than "0" (S11: No), the shift control unit 83 ends the current downshift control and executes step S11 again. In this case, the shift control unit 83 can change the gear of the automatic transmission 30 based on the accelerator operation amount ACC, the vehicle speed SP, and the operation of the upshift switch 66 and the downshift switch 67. That is, when the target output torque B is positive, the shift control unit 83 allows the automatic transmission 30 to change gears. Simultaneously, if, in step S11, the shift control unit 83 determines that the target output torque B is equal to or less than "0" (S11: Yes), the shift control unit 83 proceeds to step S12.

[0052] In step S12, the shift control unit 83 determines whether a downshift has been requested by operating the downshift switch 67. If, in step S12, the shift control unit 83 determines that a downshift has not been requested by operating the downshift switch 67 (S12: No), the shift control unit 83 proceeds to step S41. Conversely, if, in step S12, a downshift has been requested by operating the downshift switch 67 (S12: Yes), the shift control unit 83 proceeds to step S13.

[0053] In step S13, the shift control unit 83 determines whether the absolute value of the target output torque B is equal to or less than a threshold. Here, the threshold is determined as follows: More specifically, when downshifting in the vehicle 100, the larger the absolute value of the target output torque B just before downshifting, the greater the fluctuation in the actual output torque of the electric generator 10 caused by downshifting tends to be. Therefore, when designing the vehicle 100, an allowable value for the fluctuation of the output torque of the electric generator 10 caused by downshifting in the vehicle 100 is determined through experiments, etc. The allowable value for the fluctuation range of the output torque of the electric generator 10 is set as the threshold. In step S13, if the shift control unit 83 determines that the absolute value of the target output torque B is greater than the threshold (S13: No), the shift control unit 83 proceeds to step S41. Simultaneously, in step S13, if the shift control unit 83 determines that the absolute value of the target output torque B is equal to or less than the threshold (S13: Yes), the shift control unit 83 proceeds to step S21.

[0054] In step S21, the shift control unit 83 determines that downshifting is permitted. Then, the shift control unit 83 proceeds to step S31. In step S31, the shift control unit 83 executes the downshifting process in the automatic transmission 30. More specifically, the shift control unit 83 outputs a control signal to the hydraulic mechanism 50 to initiate downshifting of the automatic transmission 30 via the hydraulic mechanism 50. Then, the shift control unit 83 proceeds to step S32.

[0055] In step S32, the motor control unit 82 performs torque relaxation processing to reduce the absolute value of the output torque of the electric generator 10 compared to before the downshift processing. More specifically, the motor control unit 82 sets the target output torque B to "0". Then, the motor control unit 82 outputs a control signal to the inverter 21 so that the motor control unit 82 controls the output torque of the electric generator 10 via the inverter 21. As a result, the output torque of the electric generator 10 becomes "0". Afterwards, the motor control unit 82 proceeds to step S33.

[0056] In step S33, the shift control unit 83 determines whether the downshifting process is complete. As already described, the shift control unit 83 determines whether the downshifting process is complete based on the gear ratio of the gear to which the automatic transmission 30 will be changed through the downshifting process, the input side speed NIN, and the output side speed NOUT. In step S33, if the shift control unit 83 determines that the downshifting process is not complete (S33: No), the process of step S33 is repeated. Meanwhile, in step S33, if the shift control unit 83 determines that the downshifting process is complete (S33: Yes), the shift control unit 83 advances the process to step S34. Furthermore, if the shift control unit 83 determines that the downshifting process is complete, the motor control unit 82 performs torque relaxation processing. That is, the motor control unit 82 performs torque relaxation processing after performing the downshifting process but before the downshifting process is completed.

[0057] In step S34, the motor control unit 82 performs torque recovery processing to control the output torque of the electric generator 10, such that the output torque of the electric generator 10 has the same sign as the output torque just before the downshift processing, but its absolute value is less than the absolute value of the output torque just before the downshift processing. As a specific example, suppose the target output torque B just before the downshift processing is "-10". In this case, the motor control unit 82 takes a value whose absolute value is less than "-10", such as "-5", as the target output torque B in the torque recovery processing. Note that the processing in step S34 is executed when a positive determination is made in the processing of step S33. Therefore, the motor control unit 82 performs torque recovery processing after the downshift processing is completed. Afterwards, the motor control unit 82 ends the current downshift control and executes the processing in step S11 again.

[0058] Meanwhile, as described above, in step S13, if the shift control unit 83 determines that the absolute value of the target output torque B is greater than the threshold (S13: No), or if the shift control unit 83 determines that no downshift request has been made by operating the downshift switch 67 (S12: No), the shift control unit 83 will proceed to step S41.

[0059] In step S41, the shift control unit 83 determines that downshifting is prohibited. That is, in this case, downshifting is not performed in the automatic transmission 30. Afterwards, the shift control unit 83 ends the current downshifting control and executes the process of step S11 again.

[0060] Operation of this embodiment

[0061] First, such as Figure 3As shown, before time t11, the accelerator operation amount ACC remains constant at a certain magnitude. Furthermore, from time t11 to time t15, the accelerator operation amount ACC gradually decreases according to the driver's operation of the accelerator pedal 61, and reaches its minimum at time t15.

[0062] like Figure 3 As shown, before time t11, the target driving force A has a positive value because the accelerator operation amount ACC has a certain magnitude. Then, from time t11 to time t15, the target driving force A gradually decreases along with the accelerator operation amount ACC. Furthermore, between time t12 and time t13, and after time t14, the target driving force A has a negative value. That is, during these time periods, the vehicle decelerates by 100%.

[0063] Assume that at time t13 after time t12, the driver operates the downshift switch 67, such as... Figure 3 As shown in the diagram. Furthermore, it is assumed that at this time, the absolute value of the target output torque B of the electric generator 10 is equal to or less than the threshold. Therefore, as... Figure 3 As shown, during the time interval t13 to t14, a downshift is performed in the automatic transmission 30. At this time, as... Figure 3 As shown, during the time intervals t13 to t14, due to torque relaxation processing, the output torque of the electric generator 10 becomes "0". That is, the load on the electric generator 10 connected to the input shaft 31 of the automatic transmission 30 is minimized.

[0064] like Figure 3 As shown, the downshifting process is completed at time t14. Therefore, as... Figure 3 As shown, due to the torque recovery process, the output torque of the electric generator 10 becomes a value that has the same sign as the output torque just before the downshift process was performed, and its absolute value is less than the absolute value of the output torque just before the downshift process was performed.

[0065] Effects of the Implementation Examples

[0066] (1) In this embodiment, when the target output torque B of the electric generator 10 is zero or negative, that is, when the electric generator 10 does not provide positive acceleration to the vehicle 100, the gear ratio of the automatic transmission 30 will not be downshifted unless the driver requests a downshift by using the downshift switch 67. Therefore, in this case, no shift shock accompanying downshift will occur in the automatic transmission 30.

[0067] Meanwhile, even when the target output torque B of the electric generator 10 is zero or negative, the gear ratio of the automatic transmission 30 is downshifted when the driver requests a downshift using the downshift switch 67. Therefore, in this situation, a shift shock occurs in the automatic transmission 30 during downshifting. However, since the shift shock occurs in response to the driver's request to downshift, the driver is unlikely to experience the discomfort of an unexpected shift shock.

[0068] (2) In the vehicle 100, the torque transmission efficiency via the automatic transmission 30 changes during downshifting. As a result, when the absolute value of the output torque of the electric generator 10 is large during downshifting, the fluctuation range of the force transmitted from the electric generator 10 to the drive wheel 42 easily increases due to the change in torque transmission efficiency via the automatic transmission 30.

[0069] In this respect, in this embodiment, due to the torque relaxation process, the absolute value of the output torque of the electric generator 10 decreases during the downshifting process. Since the absolute value of the output torque of the electric generator 10 is thus small, even if the torque transmission efficiency via the automatic transmission 30 changes, the fluctuation range of the force to be transmitted from the electric generator 10 to the drive wheel 42 can be suppressed from increasing excessively, and will only increase by that amount.

[0070] (3) In this embodiment, during the torque relaxation process, the absolute value of the output torque of the electric generator 10 becomes "0". Based on this, even if the torque transmission efficiency of the automatic transmission 30 changes during the downshift process, the fluctuation range of the force transmitted from the electric generator 10 to the drive wheel 42 via the automatic transmission 30 remains constant at "0". In other words, during the downshift process, there will be no shift shock due to the change in the force transmitted from the electric generator 10 to the drive wheel 42.

[0071] (4) In this embodiment, when the absolute value of the target output torque B of the electric generator 10 is equal to or less than a threshold, downshifting and torque relaxation processing together with downshifting are performed. Therefore, even if the absolute value of the output torque of the electric generator 10 becomes "0" through torque relaxation processing, the fluctuation range of the output torque of the electric generator 10 caused by the start of downshifting will not exceed the threshold. Therefore, the acceleration of the vehicle 100 will not change too much, or the vehicle 100 will not vibrate excessively due to the excessive fluctuation range of the output torque of the electric generator 10.

[0072] (5) In vehicle 100, the gear ratio of automatic transmission 30 increases due to downshifting. Based on this, such as Figure 3As shown, the rotational speed of the output shaft 11 at time t14, which is the completion time of the downshifting process, is greater than the rotational speed of the output shaft 11 at time t13, which is the start time of the downshifting process.

[0073] Here, if the output torque of the electric generator 10 is the same before and after the downshift is performed, the driving force of the vehicle 100 becomes greater when the downshift is completed due to the higher rotational speed of the output shaft 11. In other words, a shift shock occurs when the downshift is completed.

[0074] In this respect, in this embodiment, due to the torque recovery process, the output torque of the electric generator 10 at time t14, which is the completion time of the downshifting process, has a value that has the same sign as the output torque at time t13, which is the start time of the downshifting process, and its absolute value is smaller than the absolute value of the output torque at time t13. Thus, as... Figure 3 As shown, even if the rotational speed of the output shaft 11 of the electric generator 10 becomes higher in time t14 than in time t13, the fluctuation range of the driving force of the vehicle 100 is small. That is, even when the rotational speed of the output shaft 11 of the electric generator 10 increases, it is possible to suppress the shift shock that occurs in time t14, which is the timing of the downshifting process.

[0075] (6) Regarding electric vehicles, a technique is known in which the overall braking force is controlled as the sum of the braking force of the braking device 55 and the regenerative braking force of the electric generator 10, such that the overall braking force corresponds to the braking force of the brake operation amount BRA. In such a technique, the distribution between the braking force of the braking device 55 and the regenerative braking force of the electric generator 10 is predetermined, provided that the electric generator 10 provides constant performance. However, each time the internal combustion engine is replaced by the electric generator 10 or the electric generator 10 is replaced by a new electric generator, the electric generator 10 thus provided different performance. Therefore, with the braking force distribution predetermined, the vehicle 100 provides different braking behavior each time.

[0076] Meanwhile, in this embodiment, the motor control unit 82 controls the output torque of the electric generator 10 without considering the brake operation amount BRA. Therefore, the brake operation amount BRA does not affect the regenerative torque of the electric generator 10 (i.e., the negative acceleration to be given to the vehicle 100 by the electric generator 10). Therefore, it is not possible for the negative acceleration induced in the vehicle 100 to vary due to differences in the performance of the electric generator 10 to be attached to the vehicle 100, even if the brake operation amount BRA is constant.

[0077] Variations

[0078] This embodiment can also be implemented by adding the changes described below. This embodiment and the following variations can be combined without causing any technical inconsistencies.

[0079] - In the above embodiments, the execution conditions for downshifting can be changed. For example, when performing a downshift operation, the downshifting process can be performed regardless of the magnitude of the target output torque B. That is, the processing in S13 can be omitted.

[0080] - In the above embodiments, the torque recovery process can be omitted. For example, if the change in the gear ratio of the automatic transmission 30 accompanying the downshift process is small, the rotational speed of the electric generator 10 accompanying the downshift process can hardly increase. In this case, there is no problem even if the process S34 is omitted in the downshift control.

[0081] - In the above embodiments, the output torque of the electric generator 10 can be changed during the torque relaxation process. For example, the output torque of the electric generator 10 to be changed by the torque relaxation process does not necessarily have to be changed to "0", and can be changed to a negative value less than "0" or a positive value greater than "0". Even in this case, the absolute value of the output torque of the electric generator 10 to be changed by the torque relaxation process should be less than the absolute value of the output torque just before the downshift process was performed.

[0082] - In the above embodiments, torque relaxation processing can be omitted. For example, if torque relaxation processing is omitted, shift shock is more likely to occur due to changes in torque transmission efficiency via the automatic transmission 30. Note that, as described above, downshifting is performed when the driver requests a downshift using downshift switch 67. Therefore, even if a shift shock occurs due to the omission of torque relaxation processing, the driver is unlikely to experience the discomfort of an unexpected shift shock.

[0083] - In the above embodiment, if a negative determination is made in the processing of S13, the driver can be notified that downshifting is not allowed. For example, if a negative determination is made in the processing of S13, downshifting is prohibited even if a downshift is requested by operating the downshift switch 67. Therefore, the driver may feel uncomfortable that the gear position of the automatic transmission 30 has not been changed. In view of this, if a negative determination is made in the processing of S13, the driver can be notified that downshifting is prohibited. As a specific example of notifying the driver, the driver can be notified that downshifting is prohibited by illuminating an indicator light. Furthermore, if the gear position of the automatic transmission 30 is always displayed on a display or the like, the driver can also understand that downshifting is not allowed when the gear position display does not change.

[0084] In the above embodiment, the motor control unit 82 can control the output torque of the electric generator 10 based on the brake operation amount BRA. That is, the motor control unit 82 can control the output torque of the electric generator 10 based on the brake operation amount BRA.

[0085] - In the above embodiments, the shift actuator is not limited to the downshift switch 67. For example, the shift lever 63 can be used as the shift actuator, allowing the gears of the automatic transmission 30 to be operated via the shift lever 63. In this case, the upshift switch 66 or the downshift switch 67 can be omitted.

Claims

1. A control device for controlling a vehicle, the vehicle including an electric generator, an automatic transmission, and a shift actuator, the electric generator serving as a drive source for the vehicle, the electric generator being connected to drive wheels via the automatic transmission, the automatic transmission being configured to change gear ratios, and the shift actuator being used by a driver to operate the gear ratios of the automatic transmission, the control device comprising: A motor control unit, configured to control the output torque of the electric generator; as well as A shift control unit is configured to control the gear ratio of the automatic transmission, wherein When the output torque is zero or negative, the shift control unit prohibits downshifting of the automatic transmission when there is no downshift request via operation of the shift actuator; however, when a downshift request is made via operation of the shift actuator, the shift control unit allows the execution of the downshifting process. Specifically, after the downshifting process is executed until the downshifting process is completed, the motor control unit performs a torque relaxation process that reduces the absolute value of the output torque compared to the absolute value of the output torque before the downshifting process is executed. After the downshifting process is completed, the motor control unit performs torque recovery processing: controlling the output torque so that the value of the output torque has the same positive or negative sign as the output torque just before the downshifting process is executed, and its absolute value is less than the absolute value of the output torque just before the downshifting process is executed. Wherein, under the condition that the absolute value of the output torque is equal to or less than a predetermined threshold, the motor control unit allows the execution of the downshifting process, and controls the output torque in the torque relaxation process so that the output torque is zero; The vehicle includes a mechanical braking device configured to brake the drive wheels, and a brake pedal for the driver to operate the braking device. The control device includes a brake control unit configured to control the braking force of the braking device based on the amount of operation of the brake pedal; and The motor control unit controls the output torque without taking into account the amount of operation of the brake pedal.

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