JP4449781B2 - Braking control device - Google Patents

Description

  The present invention relates to a technical field of a braking control device in a vehicle including a hydraulic braking unit and a regenerative braking unit such as a hybrid vehicle.

  As this type of technology, there is one that distributes hydraulic braking force and regenerative braking force (see, for example, Patent Document 1). According to the braking control device for an electric vehicle described in Patent Document 1 (hereinafter referred to as “conventional technology”), when a vehicle speed becomes a predetermined value or less while usually applying a regenerative braking force to a wheel. While the regenerative braking force applied to the wheels is reduced and changed, the change in the posture of the vehicle is suppressed by increasing the hydraulic braking force so as to compensate for the reduced change.

In addition, a technique has also been proposed in which, when switching from regenerative braking to friction braking, the rate of decrease in regenerative braking torque is suppressed according to the response delay of friction braking torque (see, for example, Patent Document 2).
JP 2000-225932 A JP 2004-196064 A

  When switching from the regenerative braking force to the hydraulic braking force, it is necessary to increase the hydraulic braking force in association with the decrease in the regenerative braking force. However, in the conventional technology, when applying the hydraulic braking force, a delay in response occurs in the hydraulic pressure, and the hydraulic braking force that should be applied cannot be obtained, so that the braking force may be insufficient. Such lack of braking force can cause discomfort to the driver. That is, the conventional technology has a technical problem that it is difficult to brake the vehicle without impairing comfort.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a braking control device capable of braking a vehicle without impairing comfort.

In order to solve the above-described problem, a braking control device according to the present invention is a braking control device in a vehicle including a hydraulic braking unit and a regenerative braking unit that respectively apply a hydraulic braking force and a regenerative braking force to a wheel. A request value acquisition means for acquiring a required value of a braking force to be applied to the wheel in response to an input indicating that the vehicle is to be braked, a specifying means for specifying a regenerative braking force applied to the wheel, Target value calculation means for calculating the target value of the hydraulic braking force so that the sum of the target value and the specified regenerative braking force becomes the required value; and the hydraulic braking force applied to the wheel is calculated and control means for controlling the hydraulic braking means so that the target value, the regenerative braking force applied to the wheel Keru you in the process of switching to the hydraulic braking force from the regenerative braking force, which is at least the specified braking Goal but to update the at the time of starting to switch to hydraulic braking force, so that the calculated value larger than the target value the calculated target value by adding a predetermined value to the calculated target value Value updating means, and when the calculated target value is updated, the control means is configured so that the hydraulic braking force applied to the wheel becomes the updated target value. It is characterized by controlling.

  In the present invention, the “hydraulic braking force” is a concept that includes a braking force that acts on a wheel by friction between a braking member that operates by oil pressure and the wheel. The hydraulic braking means is a means capable of applying a hydraulic braking force defined by the concept to the wheel, and a mechanism for transmitting the material and shape of the operating member and the hydraulic pressure as long as the concept is secured. There is no limitation at all. For example, the hydraulic braking means may be a brake or a brake system called a drum brake or a disc brake. Further, the hydraulic braking means may be configured to be able to control the hydraulic pressure independently from the operation amount of a brake pedal or the like via an actuator or the like. Further, the hydraulic braking means may include a control system such as an antilock brake system. Hereinafter, the operation for the hydraulic braking means to brake the vehicle with the hydraulic braking force will be appropriately referred to as “hydraulic braking”.

  On the other hand, in the present invention, “regenerative braking force” refers to regenerative torque that is generated when kinetic energy generated with the rotation of a wheel is converted into electric energy and recovered in a power storage means such as a battery (that is, regenerated). This is a concept encompassing the braking force applied to the wheel by The regenerative braking means is a means capable of applying a regenerative braking force defined by the concept to the wheel, for example, a generator (generator) connected directly or indirectly to the wheel. May be. In this case, for example, the regenerative torque may be configured to be controllable by configuring the magnetic field inside the generator to be controllable. Alternatively, the regenerative braking means may have a function as an electric motor (motor) for rotating and driving the wheels by electric energy stored in the power storage means in addition to such energy regeneration. Hereinafter, the operation for the regenerative braking means to brake the vehicle by the regenerative braking force will be referred to as “regenerative braking” as appropriate.

  According to the braking control device of the present invention, during the operation, the required value acquisition unit acquires the required value of the braking force to be applied to the wheel in response to an input indicating that the vehicle should be braked. Here, the “input to the effect that the vehicle should be braked” is artificially performed by a driver or the like through a physical or mechanical input means such as a pedal, a button, a lever, a dial, or a switch. This is a concept defined including input, and typically indicates whether or not the brake pedal provided in the vehicle is operated or the amount of operation. However, such input includes not only input by such an operation by the driver or an external operation, but also input from another controller or device when some condition is satisfied. That is, input may be performed without an external operation by the driver.

  The correspondence relationship between the input and the required value of the braking force is not limited as long as the required value can be acquired according to the input. For example, even if the braking force (that is, the required value) to be applied to the wheels is associated with the amount of operation of the brake pedal by the driver (also referred to as “stepping amount” or “stroke amount”). Good. In this case, the braking force associated with such an operation amount may be set so as to further change according to the vehicle speed.

  When the required value of the braking force is acquired, the specifying unit specifies the regenerative braking force applied to the wheel (hereinafter, referred to as “regenerative braking force execution value” as appropriate).

  The regenerative braking means is controlled by a control unit such as a regenerative ECU (Electronic Controlling Unit), for example, and according to a target value set by the control unit or a control system that further controls the control unit. Regenerative braking force is applied to the wheels. The target value of the regenerative braking force is determined relatively freely with the required value as the upper limit. For example, from the standpoint of energy regeneration, it is advantageous that the required value is actively covered by the regenerative braking force, and it is basically preferable to perform control so that the regenerative braking force is given priority over the hydraulic braking force. It is. In this case, the required value of the braking force is almost covered by the regenerative braking force. In addition, for example, when energy regeneration is impossible or difficult for some reason, or when it is judged that it is better not to apply regenerative braking force, the target value of regenerative braking force is set to zero or a value equivalent thereto. May be.

  Here, “specifying the regenerative braking force applied to the wheel” means, for example, in addition to a mode in which the braking force actually acting at the contact point between the wheel and the road surface is directly detected. This is intended to include a mode in which an execution value is acquired indirectly through arithmetic processing based on torque acting on the connected drive shafts. Further, “specify” is a concept including secondarily acquiring information representing an execution value detected or acquired directly or indirectly through some communication means.

  When the execution value of the regenerative braking force is specified, the target value calculation unit calculates the target value of the hydraulic braking force. In the present invention, the braking force (required value) required for the vehicle is distributed to the regenerative braking force and the hydraulic braking force. Specifically, the target value of the hydraulic braking force is calculated such that the sum of the target value of the regenerative braking force specified by the specifying unit becomes the required value. Then, the control means controls the hydraulic braking means so that the hydraulic braking force applied to the wheel (hereinafter referred to as “execution value of hydraulic braking force” as appropriate) becomes the calculated target value. That is, the hydraulic braking force is cooperatively controlled with the execution value of the regenerative braking force so that the braking force applied to the wheels is always maintained at the required value.

  On the other hand, the regenerative braking force that can be applied to the wheels is affected by various conditions in the vehicle. For example, the regenerative energy that can be accepted is limited by the charge state and temperature of a battery or the like that stores the regenerated energy. The upper limit of regenerative energy that can be generated by the regenerative braking means is limited by the wheel speed (vehicle speed). Therefore, the upper limit value of the regenerative braking force that can be applied to the wheels is affected by the state of the vehicle such as the battery state and the vehicle speed. In addition, regenerative braking may be difficult for some physical, electrical, or mechanical reasons. Furthermore, from the viewpoint of regenerative efficiency, regenerative braking is often not performed in the low vehicle speed region. Prohibiting regenerative braking in such a low vehicle speed region is also supported from the point that it is difficult to finally stop the vehicle by the regenerative braking force. Therefore, the execution value of the regenerative braking force tends to change frequently according to the state of the vehicle during a series of operation periods for braking the vehicle (that is, during braking). In particular, when regenerative braking is prohibited using the vehicle speed as a threshold, the regenerative braking force decreases with a high probability once the vehicle is started.

  Here, particularly, when the regenerative braking force applied to the wheels until then decreases according to the state of the vehicle, the braking force corresponding to the decrease in the regenerative braking force is switched to the hydraulic braking force by cooperative control. Therefore, ideally, the braking force of the entire vehicle is maintained at the required value.

  Actually, however, the hydraulic braking force applied to the wheel is insufficient at that time due to, for example, a response delay of the hydraulic pressure in the hydraulic braking means or a time delay for specifying the execution value of the regenerative braking force. Less than a minute can occur. Therefore, in the process in which the regenerative braking force is switched to the hydraulic braking force, the braking force applied to the wheel may not satisfy the required value. In this case, since the deceleration (negative acceleration) requested by the driver through the input cannot be obtained, the driver may feel that the vehicle is relatively accelerating, and comfort may be impaired. . In particular, when all the required values are covered by the regenerative braking force, such a problem occurs remarkably in the process of switching all of them to the hydraulic braking force.

Therefore, the braking control apparatus according to the present invention solves the problem by providing the target value update means. That is, the target value update means updates the calculated target value so that it is larger than the calculated target value in the process of switching the braking force applied to the wheel from the regenerative braking force to the hydraulic braking force. To do. Then, when the calculated target value is updated, the control means controls the hydraulic braking means so that the hydraulic braking force applied to the wheels becomes the updated target value.
In particular, the target value update means updates the calculated target value by adding a predetermined value to the calculated target value at least when the specified regenerative braking force starts to switch to the hydraulic braking force. It has a configuration.

As a result, a shortage of hydraulic braking force due to a response delay of the hydraulic pressure is compensated, and the shortage of braking force as a whole vehicle is resolved. Further, at this time, since the target value is updated by adding the predetermined value, it is possible to update the target value relatively easily, and as a result, the shortage of braking force is quickly resolved. The predetermined value may be set in advance as a value that allows the hydraulic braking force to be suitably applied experimentally, empirically, or based on simulation. In this case, some limitation may be given to the predetermined value to be added. For example, such a restriction may be a restriction that the updated target value does not exceed the required braking force value. For example, when such a restriction is applied, the predetermined value may be gradually reduced in at least a part of the period during which the target value is updated.
Further, the response delay of the hydraulic pressure is remarkably generated when the braking force starts to change. Therefore, by adding the predetermined value at least when the regenerative braking force starts to be switched to the hydraulic braking force, the effective value of the hydraulic braking force can be quickly increased, which is effective. Note that this is significantly effective when the braking force is switched from a state in which little or no hydraulic braking force is applied (a state in which the required value is almost or entirely covered by the regenerative braking force).
Thus, according to the braking control device of the present invention, it is possible to brake the vehicle without impairing comfort. Here, “resolved” defines that the braking force finally applied to the wheel approaches the required value somewhat compared to the case where no increase of the target value is performed. It is a concept to do.

  “Switching” is a concept including a decrease in the effective value of the regenerative braking force. Accordingly, whether or not it is the switching period from the regenerative braking force to the hydraulic braking force can be easily determined by a change with time of the execution value of the regenerative braking force specified by the specifying means. Alternatively, based on information from some means for setting the target value of the regenerative braking force (for example, the regenerative ECU or a control unit that controls the regenerative ECU), the switching period before the execution value of the regenerative braking force decreases. Judgment may be made to visit. Further, “in the process of switching” is a concept indicating at least a part of a period during which switching from regenerative braking force to hydraulic braking force is performed (period during which transfer from regenerative braking to hydraulic braking is performed). is there. That is, as long as the deficiency in braking force applied to the wheels is improved by updating the target value of the hydraulic braking force, the target value does not necessarily have to be updated over the entire switching period (delivery period). It is the purpose.

  The amount of increase in the target value when the target value is updated is not limited as long as the sum of the execution value of the hydraulic braking force and the execution value of the regenerative braking force approaches the required value, but preferably the sum is It is determined to be equal to the required value. At this time, the correspondence relationship between the increase amount of the target value and the increase amount of the execution value of the hydraulic braking force affected by the response delay of the hydraulic pressure is given in advance experimentally, empirically, or by simulation or the like. Also good.

  The required value acquisition means, identification means, target value calculation means, control means and target value update means according to the present invention may be configured as one processing unit such as a brake ECU mounted on the vehicle. A part may be configured as another processing unit (for example, the above-described regenerative ECU). In this case, the brake ECU may superordinately control a control system that controls regenerative braking means such as the regenerative ECU described above.

In one aspect of the braking control apparatus according to the present invention, the target value updating means controls the wheels to perform hydraulic control in a process in which the specified regenerative braking force is switched from a state substantially equal to the required value to the hydraulic braking force. adding the threshold value greater than necessary to impart power as the predetermined value.

  In order to avoid frequent operation of a hydraulic pressure transmission mechanism (for example, a solenoid valve) in the hydraulic braking means, the control means may not apply the hydraulic braking force to the wheels when the target value is less than the threshold value (dead zone). . In this case, if the predetermined value is less than the threshold value, it is difficult to avoid a delay in response to the hydraulic pressure even if the target value is updated (increased). Therefore, the response delay of the hydraulic pressure can be improved by adding a value exceeding the dead zone as the predetermined value.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
<Configuration of Embodiment>
First, the configuration of the vehicle according to the first embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 is a schematic view of the vehicle 10.

  In FIG. 1, the vehicle 10 includes left and right drive shafts 11FL and 11FR, left and right front wheels FL and FR, a brake pedal 12, a brake pedal sensor 13, a brake ECU 100, a hydraulic braking device 200, and a regenerative system 300.

  The brake ECU 100 is configured to control the hydraulic braking device 200 and the regenerative system 300 by executing a braking control process to be described later, and to control the braking force acting on the vehicle 10. It is an electronic control unit that functions as an example of a “control device”.

  The regeneration system 300 includes a regeneration ECU 310, a drive regeneration device 320, and a battery 330.

  The regenerative ECU 310 is an electronic control unit configured to control the regenerative braking force acting on the left and right front wheels FL and FR that are drive wheels of the vehicle 10 by controlling the drive regenerative device 320. The regenerative ECU 310 is electrically connected to the brake ECU 100 and is configured to always communicate with the brake ECU 100, and is superordinately controlled by the brake ECU 100.

  The drive regenerative device 320 is an example of the “regenerative braking means” according to the present invention, which includes a drive motor 321 and is configured to be able to generate a regenerative braking force as the left and right front wheels FL and FR rotate. In FIG. 1, only the left and right front wheels FL and FR that are driving wheels are shown, and the left and right rear wheels that are driven wheels are omitted for the purpose of preventing the explanation from becoming complicated.

  The left and right front wheels FL and FR are connected to the rotor of the drive motor 321 via drive shafts 11FL and 11FR and a gear mechanism (not shown), respectively. Therefore, the driving force generated by the drive motor 321 is transmitted to the left and right front wheels FL and FR via the drive shafts 11FL and 11FR, respectively. A battery 330 is further connected to the drive motor 321. The drive motor 321 has a function of generating a drive torque corresponding to the electric power supplied from the battery 330 and generating regenerative energy using the torque input from the left and right front wheels FL and FR as a power source.

  The drive motor 321 includes a magnetic field generation mechanism that generates a magnetic field having a predetermined intensity and a coil (not shown) that rotates across the magnetic field. The magnetic field generated by the magnetic field generation mechanism changes according to the command signal supplied from the regenerative ECU 310. Further, the magnetic field and the coil rotate relatively when the wheel rotates. The magnitude of the regenerative energy generated by the drive motor 321 is a value corresponding to the strength of the magnetic field generated by the magnetic field generation mechanism and the relative rotational speed between the magnetic field and the coil, that is, the wheel speeds of the left and right front wheels FL and FR. It becomes. Therefore, the magnitude of the regenerative energy changes according to the value of the command signal supplied from the regenerative ECU 310.

  When the drive motor 321 generates regenerative energy, regenerative torque that attempts to brake the rotation acts on the left and right front wheels FL and FR. That is, the regenerative torque generated by the drive motor 321 acts as a braking force on the left and right front wheels FL and FR. Hereinafter, the braking force generated by the regenerative torque will be appropriately referred to as regenerative braking force Fg.

  The regenerative energy generated by the drive motor 321 is supplied to the battery 330 as a charging current. Therefore, as the large regenerative torque is generated, the battery 330 is charged with a larger charging current. The upper limit of regenerative energy that can be received by battery 330 is limited by the state of charge and temperature of battery 330. Further, the upper limit of the regenerative energy that can be generated by the drive motor 321 is limited by the wheel speeds of the left and right front wheels FL and FR. Accordingly, the upper limit of the regenerative braking force Fg is limited by the state of charge of the battery 330, the temperature, and the wheel speeds of the left and right front wheels FL and FR.

  The hydraulic braking device 200 includes a master cylinder 210, a hydraulic actuator 220, a reservoir tank 230, wheel cylinders 240FL and 240FR, calipers 250FL and 250FR, disk rotors 260FL and 260FR, and wheel cylinder pressure sensors 270FL and 270FR according to the present invention. It is an example of “hydraulic braking means”.

  The master cylinder 210 is connected to the brake pedal 12, and when the driver of the vehicle 10 depresses the brake pedal 12, a hydraulic pressure corresponding to the depressing amount (hereinafter referred to as “master cylinder pressure PM” as appropriate). ) Is generated.

  The hydraulic actuator 220 is configured to include a plurality of solenoid valves, a motor and a pump, and a pipe line (not shown) connecting them, and a part of the pipe line is formed from an oil-based material from the reservoir tank 230. Brake fluid is supplied. The hydraulic actuator 220 is electrically connected to the brake ECU 100, and the electromagnetic valve according to a command signal output from the brake ECU 100 according to the output value of the brake pedal sensor 13 that detects the depression amount of the brake pedal 12. By opening / closing and driving the pump, etc., it is possible to generate a hydraulic pressure corresponding to the command signal. The hydraulic actuator 220 is also connected to the master cylinder 210. The hydraulic actuator 220 is connected to the wheel cylinders 240FL and 240FR provided on the left and right front wheels FL and FR. Accordingly, a hydraulic pressure (hereinafter referred to as “wheel cylinder pressure PW” as appropriate) corresponding to the hydraulic pressure generated by the hydraulic actuator 220 is supplied to each wheel cylinder. The wheel cylinder pressure PW in each wheel cylinder is detected by wheel cylinder pressure sensors 270FL and 270FR. Each wheel cylinder pressure sensor 270FL and 270FR is electrically connected to the brake ECU 100, and each wheel cylinder pressure PW is monitored by the brake ECU 100.

  Each wheel cylinder drives calipers 250FL and 250FR with a force corresponding to each wheel cylinder pressure PW. When the calipers 250FL and 250FR are driven, brake pads (not shown) attached to the calipers 250FL and 250FR are pressed toward the braking surfaces of the disc rotors 260FL and 260FR with a force corresponding to the wheel cylinder pressure PW. Accordingly, a braking force having a magnitude corresponding to a command signal given from the brake ECU 100 to the hydraulic braking device 200 is applied to each wheel. The braking force generated by the hydraulic braking device 200 is hereinafter referred to as a hydraulic braking force Fo.

  Normally, the brake ECU 110 controls the hydraulic actuator 220 so that the master cylinder 210 and the wheel cylinders 240FL and 240FR are mechanically disconnected. Therefore, each wheel cylinder pressure PW is controlled independently of the master cylinder pressure PM. However, in preparation for a case where the wheel cylinder pressure PW cannot be controlled via the hydraulic actuator 200, the brake ECU 110 mechanically connects the master cylinder 210 and the wheel cylinders 240FL and 240FR at any time, and each wheel cylinder pressure PW Is controlled to be equal to the master cylinder pressure PM. In this case, the hydraulic braking force Fo corresponding to the depression amount of the brake pedal 12 is output.

<Operation of Embodiment>
Next, with reference to FIG. 2, the details of the braking control process will be described as the operation of the present embodiment. FIG. 2 is a flowchart of the braking control process. In the present embodiment, for the purpose of preventing complication of explanation, it is assumed that braking force is applied only to the left and right front wheels FL and FR.

  In FIG. 2, first, the brake ECU 100 determines whether or not the brake pedal 12 is operated (step A10). The brake ECU 100 constantly monitors the output of the brake pedal sensor 13 at a fixed timing, and determines whether or not the brake pedal 12 is operated based on the output. When the brake pedal 12 is not operated (step A10: NO), the brake ECU 100 repeats the processing related to step A10 until the brake pedal 12 is operated, and when the brake pedal 12 is operated (step A10: YES). ), The required braking force Fr (that is, an example of the “required value of the braking force” according to the present invention) is acquired (step A11). The required braking force Fr is a braking force required for the vehicle 10 and is set in advance according to the amount of depression of the brake pedal 12. The brake ECU 100 acquires the required braking force Fr according to the depression amount of the brake pedal 12 detected by the brake pedal sensor 13.

  When the required braking force Fr is acquired, the brake ECU 100 sets a target value for the regenerative braking force Fg (step A12).

  In the present embodiment, when the regenerative braking force Fg is generated, regenerative energy corresponding to the regenerative braking force Fg is supplied to the battery 330 as charging energy as described above. Therefore, from the viewpoint of always maintaining a good charged state of the battery 330, it is preferable that the required braking force Fr is all covered by the regenerative braking force Fg. Therefore, in the present embodiment, the brake ECU 100 sets the target value of the regenerative braking force Fg so that the required braking force Fr is basically covered by the regenerative braking force Fg, that is, the regenerative braking force Fg is given priority. .

  However, since the upper limit value of the regenerative braking force Fg is affected by the state of the vehicle 10 such as the temperature of the battery 330, the charging state, and the vehicle speed (wheel speed) of the vehicle 10 as already described, the regenerative braking force is not necessarily limited. It is not always possible to cover all of the required braking force Fr with Fg. Therefore, the brake ECU 100 sets a target value for the regenerative braking force Fg according to the state of the vehicle 10. For example, in FIG. 1, the upper limit value of the regenerative braking force Fg is calculated based on the vehicle speed of the vehicle 10 and the state of charge of the battery 330 obtained from a wheel speed sensor and an SOC (State Of Charge) sensor (not shown). The upper limit value is set as a target value.

  When the target value of the regenerative braking force Fg is determined, the brake ECU 100 transmits a regeneration request to the regenerative ECU 310 so that the set target value of the regenerative braking force Fg is output (step A13). When the regeneration ECU 310 receives this regeneration request, it supplies a command signal to the drive regeneration device 320. When the drive regeneration device 320 operates in accordance with the command signal, a regenerative braking force Fg is applied to the left and right front wheels FL and FR.

  When the regeneration request is transmitted, the brake ECU 100 specifies the execution value of the regenerative braking force Fg actually applied to the left and right front wheels FL and FR in accordance with the regeneration request (step A14).

  Since the regenerative braking force Fg varies depending on the state of the vehicle 10, it does not always occur according to the target value. Therefore, the regenerative ECU 310 always grasps the execution value of the regenerative braking force Fg. Specifically, the regenerative torque is calculated from the charging current for the battery 330, and the regenerative control that finally acts on the ground contact surfaces of the left and right front wheels FL and FR based on the gear mechanism and the tire radii of the left and right front wheels FL and FR. The power Fg is calculated. The calculated execution value of the regenerative braking force Fg is transmitted as information representing the execution value to the brake ECU 100 at a certain timing, and the brake ECU 100 receives the information to execute the execution value of the regenerative braking force Fg. Is identified.

  When the execution value of the regenerative braking force Fg is specified, the brake ECU 100 calculates a target value of the hydraulic braking force Fo (step A15). At this time, the target value of the hydraulic braking force Fo is calculated so that the sum of the target value of the regenerative braking force Fg and the execution value of the regenerative braking force Fg becomes the required braking force Fr. When the target value of the hydraulic braking force Fo is calculated, the brake ECU 100 determines whether or not it is during the braking force switching period (step A16). The braking force switching period will be described later. If it is not during the braking force switching period (step A16: NO), the brake ECU 100 controls the hydraulic actuator 220 so that the execution value of the hydraulic braking force Fo becomes the calculated target value (step 18). That is, cooperative control is performed. Specifically, in response to a command signal from the brake ECU 100, each hydraulic actuator 220 has a calculated target value related to a hydraulic braking force Fo (that is, an execution value) acting on the ground contact surface of each wheel. Wheel wheel cylinder pressure PW is controlled. The correspondence relationship between the wheel cylinder pressure PW and the execution value of the hydraulic braking force Fo is determined in advance experimentally, empirically, or based on simulations. When the hydraulic braking force Fo is controlled in step A18, the process proceeds to step A10 again. If the operation of the brake pedal 12 is continued, a series of processes is repeated.

  Here, the relationship between the regenerative braking force Fg and the hydraulic braking force Fo will be described with reference to FIG. FIG. 3 is an exemplary diagram of the braking force in the vehicle 10. Hereinafter, description will be continued by adding FIG. 3 to FIG. 2 as appropriate.

  In FIG. 3, the horizontal axis represents time, and the vertical axis represents braking force. However, for the purpose of preventing the drawing from becoming complicated, the vertical axis represents the regenerative braking force, the middle row represents the hydraulic braking force, and the lower row represents the braking force that finally acts on the vehicle 10.

  In FIG. 3, during the period from time T0 to time T1, the execution value of the regenerative braking force Fg is controlled to be approximately the required value Fr. Therefore, the execution value of the hydraulic braking force Fo is substantially zero. ing.

  Here, during the braking of the vehicle 10, if the state of the vehicle 10 is not to be regeneratively braked or is difficult to perform regenerative braking, the regenerative braking force Fg is executed. The value decreases. Specifically, in step A12 of FIG. 2, the brake ECU 100 sets the target value of the regenerative braking force Fg to be gradually reduced. Along with this, the regenerative braking force Fg is gradually switched to the hydraulic braking force Fo. That is, delivery from regenerative braking to hydraulic braking (also referred to as “replacement”) is performed. The period during which the braking force is switched in this way is the aforementioned switching period. Therefore, the determination according to step A16 is performed based on the history of the execution value of the regenerative braking force Fg. The state of the vehicle 10 that requires such switching is, for example, when the vehicle speed is less than a predetermined value (for example, about 15 km / h) or when the battery 330 is in a fully charged state or a state close thereto. Or a case where some abnormality is detected.

  In FIG. 3, the target value (dotted line) of the regenerative braking force Fg starts to be controlled to decrease at time T1. Accordingly, the regenerative braking force at time T2 when a delay time elapses from time T1 until the regenerative ECU 310 controls the drive regenerative unit 320 to reduce the regenerative torque (that is, to reduce the execution value of the regenerative braking force). The effective value (solid line) of Fg starts to decrease. Then, the target value of the regenerative braking force Fg is set to zero at time T3, and the execution value of the regenerative braking force Fg becomes zero at time T4 when an appropriate time has elapsed from time T3.

  Here, if the effective value of the regenerative braking force Fg starts to decrease, the braking force corresponding to the decrease is naturally compensated by the hydraulic braking force Fo, and the braking force in the vehicle 10 is ideally maintained at the required value Fr. Is done. Specifically, an ideal target value is set as indicated by a solid line in the middle stage of FIG. 3, and the hydraulic braking force Fo is controlled according to the ideal target value. However, because the brake ECU 100 controls the hydraulic braking force to a desired value by controlling the wheel cylinder pressure PW of each wheel, the target value is actually set by the response delay of the hydraulic pressure in the hydraulic actuator 220. A time delay occurs until the target value is applied to the wheel as the hydraulic braking force Fo.

  Therefore, in the braking control process shown in FIG. 2, when the brake ECU 100 is in the braking force switching period (step A16: NO), the brake ECU 100 sets the target value calculated in step A15 (the ideal target value in FIG. 3). On the other hand, a correction value ΔF (an example of “predetermined value” according to the present invention) is added to update the target value (step A17). In this embodiment, it is assumed that a time delay related to communication between the brake ECU 100 and the regenerative ECU 310 can be ignored. Therefore, the brake ECU 100 starts updating the target value of the hydraulic braking force Fo at time T2 in FIG.

  At this time, the brake ECU 100 adds a value equal to or greater than the braking force corresponding to the dead zone of the hydraulic actuator 220 as the correction value ΔF. The dead zone is a braking force range set in advance to avoid frequent operation of the solenoid valve or the like in the hydraulic actuator 220, and the hydraulic actuator 220 does not operate with respect to a target value change within the dead zone. . The brake ECU 100 avoids a delay in response time due to the dead zone by setting the correction value ΔF to a value that exceeds the dead zone.

  Returning to FIG. 2, when the target value is updated, the updated target value is output as an execution value from the hydraulic braking device 200 by the processing according to step A <b> 18. Such updating of the target value and output of the updated target value are continued as long as it is determined in step A16 that the braking force is being switched.

  In FIG. 3, the target value of the hydraulic braking force Fo is increased in the period from time T2 to time T4 (braking force switching period). Since the target value of the hydraulic braking force Fo is controlled so as not to exceed the required braking force Fr, the correction value is gradually reduced from ΔF during the period from time T3 'to time T4. As a result, the execution value (solid line in the figure) of the hydraulic braking force Fo coincides with the ideal target value and is suitably switched to the execution value of the regenerative braking force Fg. That is, the braking force in the vehicle 10 is maintained at the required braking force Fr (lower stage in FIG. 3). In the present embodiment, the target value of the hydraulic braking force Fo is determined such that the braking force of the vehicle 10 is maintained at the required braking force Fr. Such a correction value ΔF is determined based on a correspondence relationship between the correction value ΔF and the execution value of the hydraulic braking force Fo given in advance experimentally, empirically, or based on simulations.

  Here, with reference to FIG. 4, the effect of this embodiment is demonstrated based on the comparison with a comparative example. FIG. 4 is an exemplary diagram of the braking force in the vehicle according to the comparative example of the present invention. In the figure, the same reference numerals are given to the same parts as those in FIG.

  In FIG. 4, the behavior of the regenerative braking force Fg is the same as that in FIG. 3, and the behavior of the hydraulic braking force Fo is different from that in FIG. That is, in FIG. 4, the hydraulic braking force Fo is applied according to the target value of the hydraulic braking force Fo calculated as the regenerative braking force Fg decreases (corresponding to the ideal target value in FIG. 3). That is, the target value as described above is not updated.

  In this case, even if the effective value of the regenerative braking force Fg decreases at time T2, the braking force corresponding to the decrease starts to be compensated by the hydraulic braking force Fo at time T5 when the response delay Δt has elapsed from time T2. In addition, even if the execution value of the regenerative braking force Fg becomes zero, the execution value of the hydraulic braking force Fo becomes the required braking force Fr at time T6 when the response delay Δt has elapsed from time T4. Accordingly, in the period from time T2 to time T6, the braking force of the vehicle is insufficient (see the lower stage). Due to the insufficient braking force, the vehicle according to the comparative example cannot stop at the braking distance desired by the driver, resulting in a driver feeling uncomfortable.

  As described above, in the present embodiment, the brake ECU 100 updates the target value of the hydraulic braking force Fo so that the braking force is always maintained at the required braking force Fr. Therefore, it is possible to brake the vehicle without giving the driver an unpleasant feeling, that is, without impairing comfort.

  In addition, the aspect in which brake ECU100 reduces the target value of the regenerative braking force Fg is not limited at all. For example, when the braking force is switched relatively steeply (the switching period is short), the period during which the braking force may be insufficient is short, but the vehicle may fall into a state where the braking force is not applied at all instantaneously. In addition, when the braking force is switched relatively slowly (the switching period is long), there is a possibility that the period during which the braking force is insufficient may be lengthened, but in any case, the effect according to the present invention is ensured.

  When the brake ECU 100 decreases the target value of the regenerative braking force Fg, for example, when it is determined in advance that the execution value of the regenerative braking force Fg is finally zero, the brake ECU 100 determines that the regenerative braking force Fg is zero. It can be determined in advance how the target value of the power Fg is attenuated. For example, when the vehicle speed is equal to or lower than a predetermined value, it can be determined that the current regenerative braking force is “zeroed after XX seconds” or “damped at a damping rate ΔΔ%”. In this case, the brake ECU 100 can grasp the switching period of the braking force in advance, and determine in advance how to update (increase) the execution value of the hydraulic braking force Fo in the future. Is also possible.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

1 is a schematic diagram of a vehicle according to a first embodiment of the present invention. 2 is a flowchart of a braking control process executed by a brake ECU provided in the vehicle of FIG. It is an illustration figure of the braking force in case the braking control process of FIG. 2 is performed. It is an illustration figure of braking power concerning a comparative example of the present invention .

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 14 ... Brake pedal, 100 ... Brake ECU, 200 ... Hydraulic brake device, 220 ... Hydraulic actuator, 300 ... Regenerative system, 310 ... Regenerative ECU, 320 ... Drive regenerative device.

Claims (2)

A braking control device in a vehicle comprising a hydraulic braking means and a regenerative braking means that respectively apply a hydraulic braking force and a regenerative braking force to a wheel,
Request value acquisition means for acquiring a request value of a braking force to be applied to the wheel in response to an input indicating that the vehicle is to be braked;
A specifying means for specifying a regenerative braking force applied to the wheel;
Target value calculating means for calculating the target value of the hydraulic braking force so that the sum of the target value and the specified regenerative braking force becomes the required value;
Control means for controlling the hydraulic braking means so that the hydraulic braking force applied to the wheels becomes the calculated target value;
Keru you in the process of braking force applied to the wheel is switched to the hydraulic braking force from the regenerative braking force, at the time when the regenerative braking force which is at least the specified began switched to the hydraulic braking force, which is the calculated target A target value updating means for updating the calculated target value so as to be larger than the calculated target value by adding a predetermined value to the value;
The control means controls the hydraulic braking means so that a hydraulic braking force applied to the wheel becomes the updated target value when the calculated target value is updated. Braking control device. The target value updating means sets a value equal to or greater than a threshold necessary for applying the hydraulic braking force to the wheel in the process of switching from the state where the specified regenerative braking force is substantially equal to the required value to the hydraulic braking force. The braking control device according to claim 1 , wherein the braking control device adds the predetermined value.

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