JP4725488B2 - Brake control device - Google Patents

Description

  The present invention relates to a vehicle braking device that applies braking force to a plurality of wheels provided in a vehicle.

2. Description of the Related Art Conventionally, a brake device that realizes a target braking torque determined according to a driving state or a traveling state of a vehicle by cooperation of regenerative braking and hydraulic braking is known (for example, see Patent Document 1). Regenerative cooperative control is executed such that the total braking torque, which is the sum of the regenerative braking torque and the hydraulic braking torque, becomes the required braking torque requested by the driver. In this brake device, it is possible to absorb regenerative energy by regenerative braking and use it to improve the fuel efficiency of the vehicle.
JP 2006-123889 A

  In principle, the regenerative braking force can be used when the vehicle is running, but cannot be used when the vehicle is stopped. For this reason, when the vehicle stops during the execution of the regenerative cooperative control, the vehicle is braked only by the hydraulic braking by increasing the hydraulic braking force from the state of braking the vehicle by using both the regenerative braking and the hydraulic braking together. Will be transferred. In this case, it is desired to shift while maintaining a stable brake feeling or to control the braking force so as to improve the fuel consumption of the vehicle as much as possible.

  Accordingly, an object of the present invention is to provide a brake control technique that contributes to further improvement in fuel efficiency of the vehicle.

  In order to solve the above-described problems, a brake control device according to an aspect of the present invention includes a regenerative brake unit that generates a regenerative braking force by regenerative control of an electric motor, and a hydraulic braking force that is generated by supplying hydraulic fluid from a hydraulic pressure source. And a control unit that controls the regenerative brake unit and the hydraulic brake unit so that the required braking force calculated according to the driver's brake operation is satisfied. When the control unit shifts from the control state in which the sum of the regenerative braking force and the hydraulic braking force coincides with the required braking force to the control state in which the required braking force is generated only by the hydraulic braking force, the regenerative braking force and the hydraulic braking force are The hydraulic braking force is increased and the regenerative braking force is decreased so that the sum of and the required braking force is exceeded.

  According to this aspect, since the hydraulic braking force is increased and the regenerative braking force is decreased so that the sum of the regenerative braking force and the hydraulic braking force exceeds the required braking force, the regenerative braking force is more gradual than the increase of the hydraulic braking force. It is possible to reduce it. For this reason, regenerative braking is utilized more effectively and a large amount of regenerative energy is absorbed, thereby improving the fuel efficiency of the vehicle. Further, since the braking force exceeding the required braking force is generated, the braking force can be sufficiently generated even when the transition is made, without being insufficient.

  The control unit starts to increase the hydraulic braking force toward the required braking force when the vehicle is decelerated to the first vehicle speed, and regenerative braking force when the vehicle is decelerated to a second vehicle speed that is slower than the first vehicle speed. You may start to decrease. According to this aspect, the reduction of the regenerative braking force is started after the start of the increase of the hydraulic braking force. By delaying the decrease in the regenerative braking force, the regenerative braking force can be utilized more effectively.

  The control unit is configured to increase the hydraulic braking force and decrease the regenerative braking force so that the sum of the regenerative braking force and the hydraulic braking force exceeds the required braking force, and the sum of the regenerative braking force and the hydraulic braking force. It may be possible to select the second transition mode in which the hydraulic braking force is increased and the regenerative braking force is decreased so as to match the required braking force. According to this aspect, for example, the first transition mode and the second transition mode are selectively executed according to the situation such as a driver's command. According to the first transition mode, priority is given to improving fuel efficiency, and stabilization according to the second transition mode is prioritized. By making such a selection possible, it is possible to achieve compatibility with different viewpoints.

  According to the present invention, it is possible to improve the fuel efficiency of the vehicle.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a vehicle to which a brake control device according to an embodiment of the present invention is applied. A vehicle 1 shown in the figure is configured as a so-called hybrid vehicle, and includes an engine 2, a three-shaft power split mechanism 3 connected to a crankshaft that is an output shaft of the engine 2, and a power split mechanism 3. A motor generator 4 capable of generating electricity, an electric motor 6 connected to the power split mechanism 3 via a transmission 5, and an electronic control unit for hybrid (hereinafter referred to as “hybrid ECU”) that controls the entire drive system of the vehicle 1. The electronic control unit is all referred to as “ECU”). A right front wheel 9FR and a left front wheel 9FL, which are drive wheels of the vehicle 1, are connected to the transmission 5 via a drive shaft 8.

  The engine 2 is an internal combustion engine that is operated using a hydrocarbon-based fuel such as gasoline or light oil, and is controlled by the engine ECU 13. The engine ECU 13 can communicate with the hybrid ECU 7, and performs fuel injection control, ignition control, intake control, etc. of the engine 2 based on control signals from the hybrid ECU 7 and signals from various sensors that detect the operating state of the engine 2. Execute. Further, the engine ECU 13 gives information regarding the operating state of the engine 2 to the hybrid ECU 7 as necessary.

  The power split mechanism 3 transmits the output of the electric motor 6 to the left and right front wheels 9FR, 9FL via the transmission 5, distributes the output of the engine 2 to the motor generator 4 and the transmission 5, and the electric motor. 6 and the speed of the engine 2 is reduced or increased. The motor generator 4 and the electric motor 6 are each connected to a battery 12 via a power converter 11 including an inverter, and a motor ECU 14 is connected to the power converter 11. As the battery 12, for example, a storage battery such as a nickel hydride storage battery can be used. The motor ECU 14 can also communicate with the hybrid ECU 7 and controls the motor generator 4 and the electric motor 6 via the power converter 11 based on a control signal from the hybrid ECU 7 or the like. The hybrid ECU 7, engine ECU 13, and motor ECU 14 described above are all configured as a microprocessor including a CPU. In addition to the CPU, a ROM that stores various programs, a RAM that temporarily stores data, and an input / output port And a communication port.

  The left and right front wheels 9FR and 9FL can be driven by the output of the electric motor 6 by supplying electric power from the battery 12 to the electric motor 6 via the power converter 11 under the control of the hybrid ECU 7 and the motor ECU 14. . Further, the vehicle 1 is driven by the engine 2 in a driving region where the engine efficiency is good. At this time, by transmitting a part of the output of the engine 2 to the motor generator 4 via the power split mechanism 3, the electric motor 6 is driven using the electric power generated by the motor generator 4 or the power conversion device 11 is operated. It is possible to charge the battery 12.

  When the vehicle 1 is braked, the electric motor 6 is rotated by the power transmitted from the front wheels 9FR and 9FL under the control of the hybrid ECU 7 and the motor ECU 14, and the electric motor 6 is operated as a generator. That is, the electric motor 6, the power converter 11, the hybrid ECU 7, the motor ECU 14, and the like function as a regenerative brake unit 10 that applies braking force to the left and right front wheels 9FR, 9FL by regenerating the kinetic energy of the vehicle 1 into electric energy. To do.

  The vehicle 1 includes a hydraulic brake unit 20 in addition to such a regenerative brake unit 10. The hydraulic brake unit 20 includes a power hydraulic pressure source 30, a hydraulic actuator 40, and the like. The power hydraulic pressure source 30 includes an accumulator for accumulating hydraulic fluid, an accumulator pump, a motor, and the like, and supplies pressurized hydraulic fluid to the hydraulic actuator 40. The hydraulic actuator 40 includes a control valve for controlling the hydraulic pressure of the hydraulic fluid supplied from the power hydraulic pressure source 30 to follow the target hydraulic pressure, the power hydraulic pressure source 30 and a master cylinder (not shown). A control valve for switching as a hydraulic pressure source, a pressure sensor for measuring the hydraulic pressure, and the like.

  The hydraulic actuator 40 is connected to disc brake units 21FR and 21FL provided corresponding to the left and right front wheels, and a disc brake unit provided corresponding to the left and right rear wheels (not shown). When the hydraulic fluid is supplied to the disc brake unit 21 from the hydraulic actuator 40, the brake pad is pressed against the brake disc that rotates with the wheels, and a braking force due to friction is applied to each wheel. Hereinafter, this braking force will be referred to as hydraulic braking force as appropriate.

  In the hydraulic brake unit 20, the power hydraulic pressure source 30 and the hydraulic actuator 40 are controlled by the brake ECU 70. The brake ECU 70 is configured as a microprocessor including a CPU, and includes a ROM that stores various programs, a RAM that temporarily stores data, an input / output port, a communication port, and the like in addition to the CPU. The brake ECU 70 can communicate with the host hybrid ECU 7 and the like, and controls the power hydraulic pressure source 30 and the hydraulic actuator 40 based on control signals from the hybrid ECU 7 and signals from various sensors.

  The vehicle 1 is provided with a vehicle speed sensor 75 for detecting the traveling speed of the vehicle. The vehicle speed sensor 75 detects the traveling speed of the vehicle and supplies it to the hybrid ECU 7 and the brake ECU 70. The detection value of the vehicle speed sensor 75 is given to the hybrid ECU 7 and the brake ECU 70 etc. every predetermined time. As the vehicle speed sensor 75, a wheel speed sensor or the like typically provided corresponding to each wheel can be used.

  In the present embodiment, regenerative cooperative control for controlling the regenerative brake unit 10 and the hydraulic brake unit 20 in cooperation with each other is executed, and the vehicle 1 is braked. The vehicle 1 in the present embodiment can generate a desired braking force by using the regenerative braking force and the hydraulic braking force together by executing the regenerative cooperative control. In the present embodiment, the control unit includes a hybrid ECU 7, a brake ECU 70, a motor ECU 14, and the like.

  Regenerative cooperative control is started in response to a braking request. The braking request is generated when a braking force should be applied to the vehicle, for example, when the driver operates the brake pedal. In response to the braking request, the brake ECU 70 first calculates the magnitude of the requested braking force. The required braking force is calculated based on, for example, an amount indicating a brake operation amount of the driver, represented by a brake pedal stroke, a master cylinder pressure, and the like. Further, the brake ECU 70 receives from the hybrid ECU 7 a power generation-side upper limit value that is an upper limit value of the regenerative braking force that is determined based on the number of revolutions of the electric motor 6, and an electric storage that is an upper limit value that is determined based on the charge capacity of the battery 12. Supply with the upper limit value. The brake ECU 70 determines the minimum value among the power generation side upper limit value, the power storage side upper limit value, and the required braking force as the required regenerative braking force, and transmits it to the hybrid ECU 7.

  The hybrid ECU 7 outputs the required regenerative braking force to the motor ECU 14. The motor ECU 14 outputs a control command to the power converter 11 so that the braking force applied to the left and right front wheels 9FR, 9FL by the electric motor 6 becomes the required regenerative braking force. The power conversion device 11 controls the electric motor 6 based on a command from the motor 14. As a result, the kinetic energy of the vehicle 1 is converted into electric energy and stored in the battery 12 from the electric motor 6 via the power converter 11. The accumulated energy is used for driving the wheels, etc., and contributes to improving the fuel consumption of the vehicle.

  The motor ECU 14 acquires information indicating the actual operating state of the regenerative brake unit 10 such as the number of revolutions of the electric motor 6 and transmits the information to the hybrid ECU 7. The hybrid ECU 7 calculates the actual regenerative braking force actually applied to the wheels based on the actual operating state of the regenerative brake unit 10 and transmits the actual regenerative braking force to the brake ECU 70.

  The brake ECU 70 calculates the required hydraulic braking force to be generated by subtracting the actual regenerative braking force from the required braking force. Furthermore, the brake ECU 70 calculates the target hydraulic pressure of the hydraulic fluid in the disc brake unit 21 based on the required hydraulic braking force. The brake ECU 70 controls the hydraulic brake unit 20 so that the working hydraulic pressure becomes the target hydraulic pressure. As a result, a hydraulic braking force is applied to each wheel.

  In this way, regenerative cooperative control is executed. In short, the control unit calculates the required braking force according to the driver's braking operation, and calculates the required regenerative braking force and the required hydraulic pressure braking force so that the required braking force is satisfied. The control unit controls the regenerative brake unit 10 and the hydraulic brake unit 20 so that the actual regenerative braking force and the hydraulic brake force become the required regenerative braking force and the required hydraulic brake force, respectively.

  In the regenerative cooperative control according to the present embodiment, the regenerative braking force is preferentially used from the viewpoint of improving the fuel efficiency of the vehicle. The hydraulic braking force is used complementarily when the regenerative braking force is less than the required braking force. That is, in the regenerative cooperative control, it is not essential to generate both the regenerative braking force and the hydraulic braking force at the same time, and it is not necessary to generate the hydraulic braking force when the required braking force is satisfied by the regenerative braking force. Of course, it is possible to preferentially use the hydraulic braking force, for example, by making the distribution of the regenerative braking force and the hydraulic braking force different from those of the present embodiment from other viewpoints such as improving the brake feeling.

  By the way, the regenerative braking force can in principle be generated only while the vehicle is running, and becomes zero when the vehicle is stopped. For this reason, when the vehicle stops during the execution of the regenerative cooperative control, the hydraulic braking force is increased from the control state in which the required braking force is generated using both the regenerative braking force and the hydraulic braking force, and the required control is performed only by the hydraulic braking force. It will shift to the control state which generates motive power. That is, when the vehicle stops, it is necessary to perform “replacement” from the regenerative braking force to the hydraulic braking force.

  As a switching control method, for example, the hydraulic braking force is increased toward the required braking force and the regenerative braking force is decreased while making the sum of the regenerative braking force and the hydraulic braking force coincide with the required braking force. Things can be considered. In this case, the control unit starts the replacement control when the vehicle is decelerated to a predetermined vehicle speed. As the vehicle speed further decreases below the predetermined vehicle speed, the control unit gradually increases the required hydraulic braking force so as to reach the required braking force and gradually decreases the required regenerative braking force toward zero. The control unit sets so that the sum of the required regenerative braking force and the required hydraulic braking force matches the required braking force. The control unit controls the regenerative brake unit 10 and the hydraulic brake unit 20 so that the actual regenerative braking force and the hydraulic brake force become the required regenerative braking force and the required hydraulic brake force, respectively. That is, the control unit increases the hydraulic braking force and decreases the regenerative braking force so that the sum of the regenerative braking force and the hydraulic braking force matches the required braking force.

  An example of the temporal change in vehicle speed and braking force in this method will be described with reference to FIG. FIG. 2 is a diagram schematically illustrating an example of a temporal change in vehicle speed and braking force during braking by the brake control device according to the present embodiment. The vehicle speed is shown in the upper part of FIG. 2, the required braking force and the regenerative braking force are shown in the middle part, and the hydraulic braking force is shown in the lower part. As described above, the difference between the required braking force and the regenerative braking force corresponds to the hydraulic braking force, but the hydraulic braking force is shown in the lower part of FIG. 2 for easy understanding.

  The regenerative braking force monotonously increases as the vehicle speed decreases under a constant regenerative energy absorption rate. A curve indicating the relationship between the regenerative braking force and the vehicle speed when the regenerative energy absorption rate is constant is called an equal energy curve. In other words, the regenerative braking force increases along the equal energy curve as the vehicle speed decreases. Here, the regenerative energy absorption rate refers to electric energy per unit time obtained by regenerative control of the electric motor. That the regenerative energy absorption rate is constant means that the rate of decrease in the kinetic energy of the vehicle due to regenerative braking is constant. If the rate of decrease in kinetic energy is constant, the vehicle deceleration decreases as the vehicle speed increases. Conversely, the vehicle deceleration increases as the vehicle speed decreases. That is, it can be said that the regenerative braking force decreases as the vehicle speed increases, and the regenerative braking force increases as the vehicle speed decreases.

When the running speed of the vehicle is decelerated to a predetermined vehicle speed V _1, the swap control is started. By the switching control, the regenerative braking force is controlled to decrease as the vehicle speed decreases. The predetermined vehicle speeds V ₁ to the swap control is started, in the following as appropriate, referred to as swap vehicle speeds V ₁ to.

  Therefore, the regenerative braking force monotonously increases along the equal energy curve and reaches a predetermined maximum value as the vehicle speed decreases as shown in region a in FIG. As the vehicle speed further decreases, the regenerative braking force decreases as a result of the switching control as shown in the region b of FIG. Thus, the regenerative braking force is ideally controlled to draw one mountain during one braking.

  On the other hand, the required braking force increases to a value corresponding to the amount of brake operation by the driver when triggered by the braking request (region c in FIG. 2), and is maintained until the driver's braking operation is released (FIG. 2). Area d). For this reason, the hydraulic braking force is increased or decreased as follows.

First, when the required braking force increases, the regenerative braking force increases with a decrease in the vehicle speed, so the hydraulic braking force also increases (area e in FIG. 2). Since the regenerative braking force continues to increase toward the maximum value after the required braking force reaches a value corresponding to the brake operation, the hydraulic braking force starts to decrease (region f in FIG. 2). When the swap control is decelerated in vehicle speeds V ₁ to the vehicle speed swap is started hydraulic braking force starts increasing toward the required braking force. When the required braking force is reached, the hydraulic braking force is maintained at that value (region g in FIG. 2). Then, the hydraulic braking force also decreases as the required braking force decreases due to the release of the brake operation.

Here, the swap vehicle speeds V ₁ to can be determined, for example, as follows. First, the hydraulic fluid pressure required to replace the regenerative braking force generated up to the upper limit value with the hydraulic braking force is obtained. Then, the time required to increase the pressure to the hydraulic fluid pressure is calculated based on the control response in the hydraulic brake unit 20. This time corresponds to the required time from the start to the completion of the switching control.

Next, a reduction amount of the vehicle speed when the vehicle is decelerated at the maximum vehicle deceleration before the required time elapses is calculated. The amount of decrease in the vehicle speed is the state in which the maximum regenerative braking force is generated during braking at the assumed maximum vehicle deceleration, and the vehicle speed at the start of the displacement control when the displacement control is started and at the time of completion. It corresponds to the difference with the vehicle speed. Therefore, by setting the vehicle speeds V ₁ to swap the decrease of the vehicle speed, ideally can complete the control swap until vehicle stops. Note that the replacement vehicle speed may be set higher than the ideal value in consideration of the measurement error of the vehicle speed sensor 75, that is, the error in determining whether to stop the vehicle.

  In the switching control described above, the switching control can be executed while synchronizing the decrease in the regenerative braking force and the increase in the hydraulic braking force so that the sum of the regenerative braking force and the hydraulic braking force matches the required braking force. it can. Since the braking force actually generated from before the start of the switching control to after completion can be matched with the required braking force, this is preferable in terms of realizing a stable brake feeling. Hereinafter, this switching control is appropriately referred to as brake feeling priority switching control.

By the way, in some cases, it is preferable to prioritize improving the fuel consumption of the vehicle rather than realizing a stable brake feeling. In order to improve the fuel consumption of the vehicle, the regenerative braking force may be utilized as much as possible. It is considered as one method that sets as possible slow side swap vehicle speeds V ₁ to by improving the responsiveness of example hydraulic braking force. However, the improvement of the braking force response may increase the cost of the brake control device.

  Therefore, in the present embodiment, the control unit can execute fuel efficiency priority switching control described below in addition to brake feeling priority switching control. The control unit selects and executes either brake feeling priority change control or fuel efficiency priority change control. Note that the control unit may execute only the fuel efficiency priority switching control instead of the brake feeling priority switching control. In the present embodiment, the fuel efficiency priority switching control corresponds to the first transition mode, and the brake feeling priority switching control corresponds to the second transition mode.

  For example, the control unit may select and execute either brake feeling priority change control or fuel consumption priority change control according to a command from the driver. Input means such as a switch may be provided for the driver to instruct which replacement control should be executed. An output corresponding to an operation on the input unit may be transmitted to the control unit, and the control unit may execute replacement control according to the output.

  In the fuel efficiency priority switching control, the control unit controls the hydraulic brake unit and the regenerative brake unit so as to delay the decrease in the regenerative braking force rather than the increase in the hydraulic braking force. The fuel efficiency priority change control is different from the brake feeling priority change control that synchronizes both in terms of shifting the timing of increase of the hydraulic braking force and the timing of decrease of the regenerative braking force.

Therefore, the control unit allows the sum of the required regenerative braking force and the required hydraulic braking force to exceed the required braking force. The control unit gradually increases the required hydraulic braking force so as to reach the required braking force, and gradually decreases the required regenerative braking force with a delay from the required hydraulic braking force. The control unit controls the regenerative brake unit 10 and the hydraulic brake unit 20 so that the actual regenerative braking force and the hydraulic brake force become the required regenerative braking force and the required hydraulic brake force, respectively. In this way, the control unit increases the hydraulic braking force and decreases the regenerative braking force so that the sum of the regenerative braking force and the hydraulic braking force exceeds the required braking force. In the present embodiment, the control unit, the vehicle begins to increase toward the hydraulic braking force to the required braking force when decelerated to first swap vehicle speeds V ₁ to, slower than the first swap vehicle speeds V ₁ to the second swap When the vehicle is decelerated to the vehicle speed V ₂ (see FIG. 3), the regenerative braking force is decreased.

  FIG. 3 is a diagram schematically illustrating an example of temporal changes in vehicle speed and braking force during braking by the brake control device according to the present embodiment. FIG. 3 shows temporal changes in the vehicle speed and braking force particularly in the fuel efficiency priority change control. Similar to FIG. 2, the vehicle speed is shown in the upper part of FIG. 3, the required braking force and the regenerative braking force are shown in the middle part, and the hydraulic braking force is shown in the lower part. The regenerative braking force indicated by the solid line in the middle of FIG. 3 is the regenerative braking force in the fuel efficiency priority switching control, and the line segment connecting the points A and B in the figure by the broken line is the brake feeling priority shown in FIG. The regenerative braking force in the switching control is shown for comparison.

Until the vehicle speed even when performing the fuel consumption priority swap control according to the present embodiment shown in FIG. 3 is decelerated to a first swap vehicle speeds V ₁ to the control unit and 2 the hydraulic braking force and the regenerative braking force Change as well. That is, the control unit preferentially generates the regenerative braking force so as to match the required braking force, and generates the hydraulic braking force in a complementary manner.

Control unit, from the time when the vehicle speed is decelerated to the first swap vehicle speeds V ₁ to than the average rate of increase in the hydraulic braking force up to the point of hydraulic braking force reaches the requested braking force, the vehicle speed until the first swap vehicle speeds V ₁ to The hydraulic braking force and the regenerative braking force are controlled so that the average reduction rate of the regenerative braking force from the time of deceleration to the time when the regenerative braking force becomes zero becomes smaller. In FIG. 3, the average increase rate of the hydraulic braking force is shown as the absolute value of the slope of the line segment connecting point D and point E, or the slope of the line segment connecting point A and point B. The average reduction rate of the regenerative braking force is shown as the slope of the line segment connecting points A and C. It can be said that the control unit gradually increases the required hydraulic braking force so as to reach the required braking force, and gradually decreases the required regenerative braking force on average more than the required hydraulic braking force. In the brake feeling priority switching control, it can be said that the average increase rate of the hydraulic braking force and the average decrease rate of the regenerative braking force are controlled to be equal.

In the present embodiment, when the vehicle speed is decelerated to the first swap vehicle speed V _1, the control unit, the value of the time with respect to the regenerative braking force reaches the first swap vehicle speed V _1, i.e. regenerative braking during the braking While maintaining the maximum power as it is, the hydraulic braking force starts to increase toward the required braking force. And when the vehicle speed is decelerated to a second swap vehicle speed V ₂ less than the first swap vehicle speed V _1, the control unit starts to reduce the regenerative braking force. The control unit increases the hydraulic braking force to the required braking force until the regenerative braking force reaches zero. As time passes, the hydraulic braking force starts increasing, the regenerative braking force starts decreasing, the hydraulic braking force increases completely, and the regenerative braking force decreases. It can be said that the regenerative braking force decreases with an increase in the hydraulic braking force.

For such control, hybrid ECU7 the vehicle speed after the time which is reduced to the first swap vehicle speed V _1, the regenerative braking force to be output to the required value and the brake ECU70 regenerative braking force to be output to the motor ECU14 Different from the actual generated value. Specifically, the hybrid ECU 7 outputs a value exceeding the regenerative braking force value output to the brake ECU 70 to the motor ECU 14 as a required regenerative braking force. In other words, the hybrid ECU 7 outputs a value smaller than the actual regenerative braking force value acquired from the motor ECU 14 to the brake ECU 70 as a regenerative braking force value.

Between the time when the vehicle speed reaches the first switching vehicle speed V ₁ and the time when the vehicle speed is reduced to the second switching vehicle speed V ₂ , the hybrid ECU 7 sets the required value of the regenerative braking force output to the motor ECU 14 to the first switching vehicle speed V _1. Is maintained at the value of the regenerative braking force when After being decelerated to a second swap vehicle speed V _2, the hybrid ECU7 is gradually suitably reduce the required value of the regenerative braking force to be output to the motor ECU 14. The reduction rate of the regenerative braking force is appropriately determined so that the regenerative braking force becomes zero before the vehicle stops.

  The motor ECU 14 receives the required value of the regenerative braking force that is increased from the value output to the brake ECU 70, and controls the regenerative brake unit 10 to generate the regenerative braking force according to the required value. On the other hand, the brake ECU 70 generates a hydraulic braking force that exceeds the hydraulic braking force required to supplement the regenerative braking force and satisfy the required braking force.

Therefore, in the fuel economy priority swap control, until the regenerative braking force from the vehicle speed is decelerated to the first swap vehicle speed V ₁ is zero, exceed the total required braking force and the hydraulic braking force regenerative braking force become. For this reason, in the fuel efficiency priority switching control, the driver feels a brake feeling different from that when the brake feeling priority switching control is executed.

  Further, the hybrid ECU 7 uses a regenerative braking force value that would be actually generated under the brake feeling priority switching control as the regenerative braking force value output to the brake ECU 70. The brake ECU 70 controls the hydraulic brake unit 20 so that a value obtained by subtracting the value of the regenerative braking force transmitted from the hybrid ECU 7 from the required braking force is generated as the hydraulic braking force. As a result, the hydraulic braking force is increased in the same manner in the brake feeling priority change control and the fuel efficiency priority change control. In this way, the hydraulic braking force is controlled with a common setting in the brake feeling priority switching control and the fuel efficiency priority switching control, so that the control settings can be simplified.

The first swap vehicle speeds V _{1 to} the fuel economy priority swap control is set equal to the swap vehicle speeds V _{1 to} the brake feeling priority swap control. Swap vehicle speeds V _{1 to} the brake feeling priority swap control are set in consideration of the responsiveness of the hydraulic braking force as described above, may be employed a similar swap vehicle speeds V _{1 to} be in fuel economy priority swap control. As for the second swap vehicle speed V _2, it can be determined and the amount of change in allowable brake feeling, control response in reducing the regenerative braking force, and the like based on vehicle stop determination accuracy of the vehicle as appropriate. From the viewpoint of fuel efficiency, it is preferable to set the second swap vehicle speed V ₂ to the low speed side.

  That is, the control unit controls the hydraulic braking force with a common setting in the first transition mode and the second transition mode. In the first transition mode and the second transition mode, the vehicle speed at which the increase of the hydraulic braking force is started is set in common, and the increase rate of the hydraulic braking force is also set in common.

As described above, according to the fuel efficiency priority switching control according to the present embodiment, the regenerative braking force is utilized more as shown in the middle part of FIG. 3 by delaying the decrease in the regenerative braking force than the increase in the hydraulic braking force. It is possible to improve fuel efficiency. The same effect as setting the swap vehicle speeds V _{1 to} the low speed side, is preferable in that it can be realized by a simple control of delaying the decrease in the regenerative braking force.

  Further, by making the brake feeling different between the fuel efficiency priority switching control and the brake feeling priority switching control, it is possible to make the driver feel that control intended to improve fuel efficiency is being executed. This is expected to improve merchantability. Entrusting the driver with the choice between fuel efficiency priority switching control and brake feeling priority switching control is also considered to contribute to the improvement of merchantability. In addition, since the braking force that is actually generated exceeds the required braking force, the braking force is not insufficient, and the safety of the fuel efficiency priority change control is good.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added to each embodiment based on the knowledge of those skilled in the art, and such modifications are added. Embodiments can also be included within the scope of the present invention. Here are some examples.

  In the above-described embodiment, the control unit generates the regenerative braking force and the hydraulic braking force so that the hydraulic braking force starts increasing, the regenerative braking force starts decreasing, the hydraulic braking force increases, and the regenerative braking force decreases. I have control. Instead, for example, the increase of the hydraulic braking force, the start of the decrease of the regenerative braking force, the completion of the decrease of the regenerative braking force, and the completion of the increase of the hydraulic braking force occur. It is also possible to execute the switching control so as to be completed prior to the increase of. Also in this case, since the decrease start of the regenerative braking force is delayed with respect to the start of increase of the hydraulic braking force, the regenerative braking force can be effectively used. In addition, as in the above-described embodiment, both the change in brake feeling and the safety of fuel efficiency priority change control can be achieved.

Alternatively, until the vehicle speed is decelerated from reaching the first swap vehicle speeds V _{1 to} to a second swap vehicle speed V ₂ is not maintained at a value of the regenerative braking force when it reaches the first swap vehicle speeds V _{1 to} May be. If possible it may be further increased than the value of the regenerative braking force when it reaches the first swap vehicle speed V _1. Or it may be decreased from the value of the regenerative braking force when it reaches the first swap vehicle speed V _1. When decreasing, it is desirable to make it slower than the increase rate of the hydraulic braking force. The regenerative braking force fluctuation may be more preferably set in consideration of the fuel efficiency performance to be aimed at and the brake feeling.

1 is a schematic configuration diagram illustrating a vehicle to which a brake control device according to an embodiment of the present invention is applied. It is a figure which shows typically an example of the time change of the vehicle speed and braking force at the time of the braking of the brake control apparatus which concerns on this embodiment. It is a figure which shows typically an example of the time change of the vehicle speed and braking force at the time of the braking of the brake control apparatus which concerns on this embodiment.

Explanation of symbols

  7 hybrid ECU, 10 regenerative brake unit, 14 motor ECU 14, 20 hydraulic brake unit, 70 brake ECU, 75 vehicle speed sensor.

Claims (3)

A regenerative brake unit that generates regenerative braking force by regenerative control of the electric motor;
A hydraulic brake unit that generates hydraulic braking force by supplying hydraulic fluid from a hydraulic source;
A controller that controls the regenerative brake unit and the hydraulic brake unit so that a required braking force calculated according to a driver's brake operation is satisfied,
When the control unit shifts from a control state in which the sum of the regenerative braking force and the hydraulic braking force coincides with the required braking force to a control state in which the required braking force is generated only by the hydraulic braking force, the regenerative braking force and the hydraulic pressure control are performed. In order to increase the hydraulic braking force and decrease the regenerative braking force so that the sum of the power and the required braking force exceeds, the hydraulic braking force increases toward the required braking force when the vehicle is decelerated to the first vehicle speed. The brake control device is characterized by starting to reduce the regenerative braking force when the vehicle is decelerated to a second vehicle speed that is slower than the first vehicle speed . A regenerative brake unit that generates regenerative braking force by regenerative control of the electric motor;
A hydraulic brake unit that generates hydraulic braking force by supplying hydraulic fluid from a hydraulic source;
A controller that controls the regenerative brake unit and the hydraulic brake unit so that a required braking force calculated according to a driver's brake operation is satisfied,
When the control unit shifts from a control state in which the sum of the regenerative braking force and the hydraulic braking force coincides with the required braking force to a control state in which the required braking force is generated only by the hydraulic braking force, the regenerative braking force and the hydraulic pressure control are performed. In order to increase the hydraulic braking force and decrease the regenerative braking force so that the sum of the power and the required braking force exceeds, the hydraulic braking force increases toward the required braking force when the vehicle is decelerated to the first vehicle speed. The regenerative braking force is decreased at a slower rate than the increase rate of the hydraulic braking force while the vehicle is decelerated from the first vehicle speed to a second vehicle speed that is slower than the first vehicle speed, and the second vehicle speed is reduced. After the vehicle speed , the brake control device reduces the regenerative braking force so that the regenerative braking force becomes zero before the vehicle stops . The control unit includes a first transition mode in which the hydraulic braking force is increased and the regenerative braking force is decreased so that the sum of the regenerative braking force and the hydraulic braking force exceeds the required braking force, and the regenerative braking force and the hydraulic braking force. 3. The brake control device according to claim 1, wherein a second transition mode in which the hydraulic braking force is increased and the regenerative braking force is decreased so that the sum matches the required braking force can be selected.

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