JP4661313B2 - Brake control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle brake that controls the brake hydraulic pressure in a wheel cylinder generated by the operation of a hydraulic pump when the driver operates the brake operation member to a value corresponding to the operation of the brake operation member. The present invention relates to a control device, and more particularly to setting of the operation start time of the hydraulic pump.

  In recent years, this type of brake device has been widely proposed and is generally referred to as a brake-by-wire system. Such a brake device includes, for example, a sensor (for example, a stroke sensor) that detects an operation amount of a brake operation member (for example, a brake pedal) by a driver. When the brake operation member is operated by the driver, the device activates the hydraulic pump and generates the hydraulic pump based on the output of the sensor (that is, an electric signal). The brake fluid pressure in the wheel cylinder (hereinafter referred to as “wheel cylinder fluid pressure”) is controlled to a value corresponding to the operation amount.

  In such an apparatus, it is required that the wheel cylinder hydraulic pressure is quickly increased to follow the value corresponding to the operation amount after the driver starts operating the brake operation member. Here, if the hydraulic pump is activated at the same time as the operation of the brake operation member, this requirement may not be achieved. This is based on the following reason.

  That is, immediately after the operation of the hydraulic pump is started, due to the low rotational speed, the discharge flow rate of the hydraulic pump becomes a value necessary for increasing the wheel cylinder hydraulic pressure to a value corresponding to the operation amount. On the other hand, it is easy to run out.

  In addition, at the initial stage when the wheel cylinder hydraulic pressure starts to increase from “0” due to the start of operation of the hydraulic pump, the brake pad is not in contact with the corresponding brake disk when the wheel cylinder hydraulic pressure is “0”. It moves from the position to a position that contacts the brake disk (position where the brake disk can be pressed). During this time, most of the amount of brake fluid discharged from the hydraulic pump is consumed for the movement of the piston in the wheel cylinder accompanying the movement of the brake pad, so that the wheel cylinder hydraulic pressure can hardly increase. The above is the reason why the above requirement cannot be achieved if the hydraulic pump is started simultaneously with the start of operation of the brake operation member.

For this reason, in the brake hydraulic pressure control device described in Patent Document 1 below, the amount of operation of the accelerator pedal is set to “0” even when the brake operation member is not operated (started) by the driver. Then, it is predicted that the operation of the brake operation member will be started thereafter (immediately thereafter), and the operation of the hydraulic pump is started earlier than the operation start time of the brake operation member.
JP-A-9-188242

  However, even when the operation of the hydraulic pump is started when the operation amount of the accelerator pedal becomes “0” in this way, for example, when a sudden (panic) brake operation is performed, If the amount of operation of the brake operation member immediately after the operation start time of the brake operation member is very large, the rotation speed of the hydraulic pump has not yet sufficiently increased immediately after the operation start time of the brake operation member. As a result, the discharge flow rate of the hydraulic pump may still be insufficient with respect to the value required to increase the wheel cylinder hydraulic pressure to a value corresponding to the operation amount.

  In other words, when the brake operation is abruptly performed, the wheel cylinder hydraulic pressure cannot quickly follow the value corresponding to the operation amount after the start of the operation of the brake operation member by the driver. There is a problem that there is.

  The present invention has been made to cope with such a problem, and the object thereof is a brake control device applied to a brake-by-wire system, even when a sudden braking operation is performed. An object of the present invention is to provide a wheel cylinder fluid pressure that can quickly follow the value corresponding to the operation of the brake operation member after the brake operation start time.

  The brake hydraulic pressure control device according to the present invention includes a hydraulic pump for generating a brake hydraulic pressure in a wheel cylinder of a vehicle, and an operation of the hydraulic pump when a driver operates a brake operating member. The brake fluid pressure control means for controlling the brake fluid pressure generated in the wheel cylinder to a value corresponding to the operation of the brake operation member is applied to a vehicle brake device.

  The brake fluid pressure control device according to the present invention is characterized in that a deceleration behavior index value acquisition means for acquiring a deceleration behavior index value, which is a value representing the degree of deceleration behavior of the vehicle, and an operation of the brake operation member by the driver Pump operation start means for starting the operation of the hydraulic pump when the degree of the deceleration behavior represented by the acquired deceleration behavior index value is not less than a predetermined level even if It is in having.

  In general, when the brake operation is started from the state where the driver is operating the accelerator pedal while the driver is operating, the accelerator pedal operation amount is first reduced to “0”, and then the brake operation is started. The

  Here, the deceleration behavior may occur in the vehicle while the accelerator pedal operation amount is decreasing. In other words, a deceleration behavior can occur in the vehicle from the time before the accelerator pedal operation amount becomes “0”. In other words, even when the brake operation member is not operated, it can be determined that the driver has an intention to decelerate by detecting the deceleration behavior of the vehicle.

  The present invention is based on such knowledge. That is, according to the present invention, even when the brake operation member is not operated by the driver, the degree of the deceleration behavior represented by the acquired deceleration behavior index value becomes a predetermined level or more. Then, the operation of the hydraulic pump is started in anticipation that the operation of the brake operation member is started thereafter (immediately after).

  Thereby, the operation of the hydraulic pump can be started at an early stage from the time before the accelerator pedal operation amount becomes “0” (that is, the time sufficiently before the operation of the brake operation member is started). Therefore, it can be ensured that the rotational speed of the hydraulic pump is sufficiently increased at the start of operation of the brake operation member. As a result, even when an abrupt brake operation is performed, the wheel cylinder hydraulic pressure can quickly follow the value corresponding to the operation of the brake operation member after the start of the brake operation.

  In this case, the deceleration behavior index value acquisition means is configured to acquire a time differential value of acceleration in the longitudinal direction of the vehicle (hereinafter referred to as “vehicle acceleration”) as the deceleration behavior index value. The pump operation start means is configured such that, even when the driver does not operate the brake operation member, when the acquired time differential value of the acceleration is equal to or less than a predetermined negative value, the hydraulic pressure Suitably configured to initiate pump operation.

  The time differential value (negative value) of the vehicle body acceleration can be a value that accurately represents an indication of the deceleration behavior of the vehicle (particularly rapid deceleration behavior). In addition, the sudden deceleration behavior in the vehicle means that the rate of decrease in the accelerator pedal operation amount is large. Furthermore, when the rate of decrease of the accelerator pedal operation amount is large, the subsequent brake operation is often abrupt.

  From the above, if configured as described above, a sign of a sudden brake operation can be accurately predicted, and as a result, when a sudden brake operation is performed, the wheel cylinder hydraulic pressure is further increased after the start of the brake operation. The value according to the operation of the brake operation member can be surely followed.

  Furthermore, the pump operation start means is configured such that the vehicle body speed of the vehicle is equal to or higher than a predetermined speed even when the brake operation member is not operated by the driver, and the acquired acceleration is It is more preferable that the operation of the hydraulic pump is started when the time differential value is equal to or less than a negative predetermined value.

  In general, the degree of the requirement that “the wheel cylinder hydraulic pressure immediately follows the value corresponding to the operation of the brake operation member after the start of operation of the brake operation member” increases as the vehicle body speed of the vehicle increases. In other words, for example, when the vehicle body speed is extremely low, for example, the speed of creep generated by the action of the torque converter of the automatic transmission, the hydraulic pump starts operating earlier than the operation start time of the brake operating member. The degree of demand to be made is very low.

  Therefore, if the hydraulic pump is started only when the vehicle body speed of the vehicle is equal to or higher than a predetermined speed (for example, the upper limit value of the creep speed) as in the above configuration, the hydraulic pump is unnecessarily needed. Since the occurrence of a situation where the operation is started early can be prevented, an increase in energy consumption can be suppressed.

  By the way, the brake device for a vehicle to which the brake control device according to the above invention is applied is specifically a solenoid valve interposed between a reservoir and a wheel cylinder, and between the solenoid valve and the wheel cylinder. When the brake operation member is operated by the driver and the hydraulic pump that discharges the brake fluid, the brake fluid in the wheel cylinder is generated by operating the hydraulic pump and operating the hydraulic pump. Brake fluid pressure control means for controlling the electromagnetic valve so that the pressure becomes a value corresponding to the operation of the brake operation member.

  In this case, the solenoid valve is preferably a normally open solenoid valve. The wheel cylinder hydraulic pressure needs to be maintained at “0” from the time when the hydraulic pump is started at an early stage until the operation of the brake operating member is started.

  According to the above configuration, the wheel cylinder hydraulic pressure can be maintained at “0” without exciting the electromagnetic valve during this period. That is, since the excitation period of the solenoid valve can be set only during operation of the brake operation member, an increase in energy consumption can be further suppressed.

  Further, the normally open solenoid valve is more preferably a linear solenoid valve (that is, a normally open linear solenoid valve). According to this, since the wheel cylinder hydraulic pressure can be adjusted linearly (in a stepless manner), the wheel cylinder hydraulic pressure can be made to follow more accurately with a value corresponding to the operation of the brake operating member.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a vehicle brake device including a vehicle brake control device according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a vehicle equipped with a brake device 10 according to an embodiment of the present invention.

  The brake device 10 is a so-called brake-by-wire system, and a brake pedal BP and a brake hydraulic circuit are separated. The brake device 10 is configured to include a stroke simulator mechanism 20 and a hydraulic unit 30 for generating braking force due to brake fluid pressure on the wheels.

  The stroke simulator mechanism 20 incorporates a known reaction force application mechanism that applies an appropriate reaction force corresponding to the brake fluid pressure corresponding to the stroke St to the brake pedal BP according to the stroke St of the brake pedal BP. Yes. Detailed description of the reaction force application mechanism will be omitted. Thus, the driver can obtain an appropriate brake pedal feeling when operating the brake pedal BP.

  As shown in FIG. 2 showing the schematic configuration of the hydraulic unit 30, the brake fluid of two systems comprising a front wheel side system related to the front two wheels FL and FR and a rear wheel side system related to the rear two wheels RL and RR is shown. A pressure circuit is provided. Since the front wheel system and the rear wheel system have the same configuration, only the front wheel system will be described below.

  A normally open linear solenoid valve LVfr is interposed between a reservoir RS for storing brake fluid at atmospheric pressure and a wheel cylinder Wfr of the right front wheel FR. A normally open linear solenoid valve LVfl is interposed between the reservoir RS and the wheel cylinder Wfl of the left front wheel FL. The operation of the normally open linear solenoid valves LVfr and LVfl will be described later.

  The front wheel side motor Mf which is a brushless motor is configured to drive two hydraulic pumps HPfr and HPfl which are trochoid pumps simultaneously. Note that the brushless motor has an advantage of excellent response and durability. Moreover, the trochoid pump has the merit that the discharge pulsation is smaller than that of the so-called piston pump, and the noise accompanying the operation is small.

  The hydraulic pump HPfr pumps up the brake fluid in the reservoir RS via a check valve, and discharges the pumped brake fluid between the normally open linear solenoid valve LVfr and the wheel cylinder Wfr via the check valve. Yes. Similarly, the hydraulic pump HPfl pumps up the brake fluid in the reservoir RS through the check valve, and discharges the pumped brake fluid between the normally open linear solenoid valve LVfl and the wheel cylinder Wfl through the check valve. It has become.

  Next, the normally open linear solenoid valves LVfr and LVfl will be described. Since the normally open linear solenoid valves LVfr and LVfl have the same configuration, the normally open linear solenoid valve LVfr will be mainly described below. A force in the opening direction based on a biasing force from a coil spring (not shown) is constantly acting on the valve body of the normally open linear electromagnetic valve LVfr.

  Further, the valve body of the normally open linear electromagnetic valve LVfr is braked in the reservoir RS from the brake fluid pressure in the wheel cylinder Wfr (hereinafter referred to as “wheel cylinder fluid pressure Pwfr”. The same applies to other wheels). The force in the opening direction based on the differential pressure obtained by reducing the hydraulic pressure (that is, the atmospheric pressure) (hereinafter simply referred to as “actual differential pressure ΔPfr”, the same applies to other wheels) and the normally open linear electromagnetic A closing force based on a suction force that increases proportionally with the energization current to the valve LVfr is applied.

  As a result, the differential pressure (command differential pressure) corresponding to the suction force is determined so as to increase in proportion to the energization current. The normally open linear solenoid valve LVfr is closed when the command differential pressure is larger than the actual differential pressure ΔPfr, thereby blocking communication between the reservoir RS and the wheel cylinder Wfr.

  On the other hand, the normally open linear solenoid valve LVfr opens when the actual differential pressure ΔPfr is greater than the command differential pressure, and communicates the reservoir RS with the wheel cylinder Wfr. As a result, the brake fluid between the normally open linear solenoid valve LVfr (supplied from the hydraulic pump HPfr) and the wheel cylinder Wfr flows to the reservoir RS side via the normally open linear solenoid valve LVfr, so that the actual differential pressure is increased. ΔPfr (accordingly, wheel cylinder hydraulic pressure Pwfr) can be adjusted to coincide with the command differential pressure.

  In other words, when the front wheel side motor Mf (hydraulic pump HPfr) is driven, the wheel cylinder hydraulic pressure Pwfr is linearly independent (steplessly) according to the energization current to the normally open linear solenoid valve LVfr. It can be controlled.

  On the other hand, when the normally open linear solenoid valve LVfr is in a non-excited state (that is, when the energization current is set to “0”), the normally open linear solenoid valve LVfr is kept open by the biasing force of the coil spring. Yes. In this case, regardless of whether or not the front wheel side motor Mf (hydraulic pump HPfr) is driven, the actual differential pressure ΔPfr becomes “0” and the wheel cylinder hydraulic pressure Pwfr becomes the brake hydraulic pressure in the reservoir RS (ie, , Atmospheric pressure).

  The same applies to the normally open linear solenoid valve LVfl. That is, when the front wheel side motor Mf (hydraulic pump HPfl) is driven, the wheel cylinder hydraulic pressure Pwfl is independently and linearly (steplessly) controlled according to the energization current to the normally open linear solenoid valve LVfl. To get. On the other hand, when the normally open linear solenoid valve LVfl is in the non-excited state (that is, when the energization current is set to “0”), the actual motor regardless of whether the front wheel side motor Mf (hydraulic pump HPfl) is driven or not. The differential pressure ΔPfl becomes “0”, and the wheel cylinder hydraulic pressure Pwfl becomes equal to the brake hydraulic pressure (that is, atmospheric pressure) in the reservoir RS.

  The front wheel side system has been described above. The same applies to the rear wheel side system. When the rear wheel motor Mr (hydraulic pump HPrr, HPrl) is driven, the normally open linear solenoid valves LVrr, LVrl The wheel cylinder hydraulic pressures Pwrr and Pwrl can be controlled linearly (in a stepless manner) and individually in accordance with the respective energization currents. On the other hand, when the normally open linear solenoid valves LVrr and LVrl are de-energized (that is, when the energization current is set to “0”), whether or not the rear wheel side motor Mr (hydraulic pumps HPrr and HPrl) is driven. Regardless of this, the actual differential pressures ΔPrr, ΔPrl become “0”, and the wheel cylinder hydraulic pressures Pwrr, Pwrl become equal to the brake hydraulic pressure in the reservoir RS (ie, atmospheric pressure).

  As described above, the hydraulic unit 30 individually drives the wheel cylinder hydraulic pressure Pw ** by driving the motors Mf and Mr and controlling the current supplied to the normally open linear solenoid valve LV **. It can be adjusted. Note that “**” added to the end of the variable, etc. is a comprehensive notation such as “fl”, “fr”, etc. attached to the end of the variable to indicate which wheel the variable is related to. Thus, for example, the wheel cylinder hydraulic pressure Pw ** comprehensively indicates the wheel cylinders Pwfr, Pwfl, Pwrr, Pwrl.

  Referring to FIG. 1 again, this brake device 10 includes electromagnetic pickup type wheel speed sensors 41fr, 41fl, 41rr and 41rl that respectively output signals having a frequency corresponding to the wheel speed of the wheel **, and brake pedal BP. A stroke sensor 42 that detects a stroke and outputs a signal indicating a brake pedal stroke St; an accelerator operation amount sensor 43 that detects an operation amount of an accelerator pedal AP and outputs a signal indicating an accelerator pedal operation amount Accp; and a wheel cylinder Wheel cylinder hydraulic pressure sensors 44fr, 44fl, 44rr, 44rl (see FIG. 2) for detecting the hydraulic pressure Pw ** are provided.

  In addition, the brake device 10 includes an electric control device 50. The electrical control device 50 includes a CPU 51 connected to each other by a bus, a routine (program) executed by the CPU 51, a table (lookup table, map), a ROM 52 in which constants are stored in advance, and the CPU 51 temporarily stores data as necessary. The microcomputer includes a RAM 53 that stores data, a backup RAM 54 that stores data while the power is on, and retains the stored data while the power is shut off, and an interface 55 including an AD converter. The interface 55 is connected to the sensors 41 to 44, supplies signals from the sensors 41 to 44 to the CPU 51, and in response to instructions from the CPU 51, the electromagnetic valve LV ** of the hydraulic unit 30 and the motors Mf, Mr. A drive signal is sent to the.

(Outline of brake fluid pressure control)
Next, an outline of the brake fluid pressure control executed by the brake device 10 according to the embodiment of the present invention having the above-described configuration (hereinafter referred to as “this device”) will be described. While the driver is operating the brake pedal BP (hence, when the brake pedal stroke St> 0), this apparatus drives the motors Mf and Mr together (thus, the hydraulic pump). HP ** is driven) and the normally open linear solenoid valve LV ** is controlled to adjust the wheel cylinder hydraulic pressure Pw ** to the optimum target value corresponding to the brake pedal stroke St.

  As a result, the relationship between the wheel cylinder hydraulic pressures on the front wheel side and the rear wheel side is basically set so as to follow a well-known ideal braking force distribution curve. Further, the wheel cylinder hydraulic pressures Pwfr and Pwfl for the left and right front wheels are set to the same pressure, and the wheel cylinder hydraulic pressures Pwrr and Pwrl for the left and right rear wheels are also set to the same pressure. The above is the outline of the brake fluid pressure control.

(Early start of operation of hydraulic pump HP **)
Next, the advancement of the operation start timing of the hydraulic pump HP ** will be described. Assuming that the hydraulic pump HP ** starts operating simultaneously with the start of operation of the brake pedal BP by the driver, as described above, the wheel cylinder hydraulic pressure Pw ** is quickly braked after the start of operation of the brake pedal BP. The target value corresponding to the pedal stroke St cannot be followed. This is mainly due to the fact that the rotational speed of the hydraulic pump HP ** has not yet sufficiently increased immediately after the start of operation of the brake pedal BP, and the discharge flow rate of the hydraulic pump HP ** is insufficient. .

  Therefore, in order to promptly follow the target value of the wheel cylinder hydraulic pressure Pw ** after the operation start time of the brake pedal BP, the operation start timing of the hydraulic pump HP ** is advanced and the operation of the brake pedal BP is performed. It is necessary to ensure that the rotational speed of the hydraulic pump HP ** has already increased sufficiently at the start.

  Therefore, in the present device, when the operation of the brake pedal BP is not started, the time differential value DDVso of the vehicle body acceleration DVso calculated as described later is equal to or less than a predetermined negative value −α (α: a positive constant). In principle, the operation of the motors Mf, Mr (and hence the hydraulic pump HP **) is started earlier than the operation start point of the brake pedal BP. The vehicle body acceleration DVso takes a positive value when the vehicle body is accelerating while moving forward, and takes a negative value when the vehicle body is decelerating while moving forward.

  Hereinafter, this will be described with reference to the time chart of FIG. In FIG. 3, the operation of the brake pedal BP is started at a subsequent time t <b> 4 from a state in which the driver keeps the accelerator pedal operation amount Accp constant before the time t <b> 1 and the vehicle is traveling normally (constant speed traveling). In this case, an example of changes in the brake pedal stroke St, the accelerator pedal operation amount Accp, the vehicle body acceleration DVso, and the time differential value DDVso of the vehicle body acceleration is shown.

  In this case, first, after time t1, the driver performs an operation of returning the accelerator pedal AP. As a result, as shown in FIG. 3B, the accelerator pedal operation amount Accp decreases after time t1, and becomes “0” at time t3. Thereafter, the driver changes the foot that has been operating the accelerator pedal AP to the brake pedal BP, and starts the operation of the brake pedal BP at time t4. As a result, as shown in FIG. 3A, the brake pedal stroke St increases from “0” after time t4.

  When the accelerator pedal operation amount Accp and the brake pedal stroke St change in this manner, the vehicle already has a deceleration behavior from the time t1 to t3 when the accelerator pedal operation amount Accp is decreasing, and FIG. As shown, the vehicle body acceleration DVso decreases from “0” after time t1.

  As a result, as shown in FIG. 3D, the time differential value DDVso (deceleration behavior index value) of the vehicle body acceleration DVso is obtained at time t2 before time t3 when the accelerator pedal operation amount Accp becomes “0”. The “negative predetermined value−α” is reached. Thus, the time differential value DDVso (negative value) of the vehicle body acceleration is a value that early and accurately represents a sign of a sudden deceleration behavior of the vehicle.

  That is, even before the operation of the brake pedal BP is started (in this example, before the time t4), the time differential value DDVso of the vehicle body acceleration reaches the “negative predetermined value −α”, so that the vehicle If a clear deceleration behavior is detected, it can be determined that the driver has an intention to decelerate.

  From the above, this apparatus is the hydraulic pump HP ** before the operation of the brake pedal BP is started and the time differential value DDVso of the vehicle body acceleration is equal to or less than the “negative predetermined value −α”. In principle, the operation of As a result, the time (according to time t2 in this example) before the time (in this example, time t3) when the accelerator pedal operation amount Accp becomes “0”, that is, the operation start time of the brake pedal BP (in this example, time t2). The operation of the hydraulic pump HP ** can be started at an early stage from a time point sufficiently before time t4).

  Therefore, it can be ensured that the rotation speed of the hydraulic pump HP ** is sufficiently increased at the operation start time of the brake pedal BP (in this example, time t4). As a result, even when the brake pedal BP is suddenly operated, the wheel cylinder hydraulic pressure Pw ** is promptly determined according to the brake pedal stroke St after the brake operation start time (in this example, after time t4). The target value can be made to follow.

  In addition, the hydraulic pump HP ** (that is, the motor Mf, Mr) is always operated after the brake operation start time so that the wheel cylinder hydraulic pressure Pw ** quickly follows the target value corresponding to the brake pedal stroke St. A method is also conceivable. As described above, even when the hydraulic pump HP ** is operating, the wheel cylinder hydraulic pressure Pw is set by deactivating the normally open linear solenoid valve LV ** when the brake pedal BP is not operated. This is because ** can be maintained at “0”.

  However, with this method, the operating time of the motors Mf and Mr becomes long and energy consumption increases. On the other hand, according to the present apparatus, the wheel cylinder hydraulic pressure Pw ** can quickly follow the target value corresponding to the brake pedal stroke St after the brake operation start time, while being required for driving the motors Mf and Mr. An increase in energy consumption can be suppressed as much as possible.

(Actual operation)
Next, the actual operation of the brake device 10 according to the embodiment of the present invention configured as described above will be described with reference to FIGS. 4 to 7, which are flowcharts showing routines executed by the CPU 51 of the electric control device 50. explain.

<Calculation of wheel speed, etc.>
The CPU 51 repeatedly executes the routine for calculating the wheel speed and the like shown in FIG. 4 every elapse of a predetermined time (execution interval time Δt, for example, 6 msec). Therefore, when the predetermined timing is reached, the CPU 51 starts the process from step 400, proceeds to step 405, and calculates the wheel speed (the speed of the outer periphery of the wheel **) Vw ** at the current time of the wheel **. Specifically, the CPU 51 calculates the wheel speed Vw ** based on the fluctuation frequency of the output value of the wheel speed sensor 41 **.

  Next, the CPU 51 proceeds to step 410 to calculate the estimated vehicle body speed Vso based on the obtained wheel speed Vw **. This estimated vehicle body speed Vso is set to the minimum value of the wheel speeds Vw ** when the vehicle is in a driving state (Accp> 0), for example, and when the vehicle is in a braking state (St> 0). Is set to the maximum of the wheel speeds Vw **.

  Next, the CPU 51 proceeds to step 415, and the estimated vehicle body speed Vso obtained in step 410, the estimated vehicle body speed previous value Vsob updated in step 435 described later at the time of the previous execution of this routine, and the step 415 The vehicle body acceleration DVso is calculated based on the described formula. Thus, the vehicle body acceleration DVso takes a positive value when the vehicle body is accelerating while moving forward, and takes a negative value when the vehicle body is decelerating while moving forward.

  Subsequently, the CPU 51 proceeds to step 420, in which the vehicle body acceleration DVso obtained in step 415, the vehicle body acceleration previous value DVsob updated in step 435 described later at the time of the previous execution of this routine, A time differential value DDVso of the vehicle body acceleration is calculated based on the described formula. This step 420 corresponds to deceleration behavior index value acquisition means.

  Next, the CPU 51 proceeds to step 425 and comprehensively determines the brake pedal BP by the driver from information such as the value of the brake pedal stroke St detected by the stroke sensor 42 and the state of a well-known brake switch (stop lamp switch) not shown. Judge whether or not there is a willingness to step in. As a result, the CPU 51 sets the value of the flag BRAKE to “1 (during braking)” when it is determined that the brake pedal BP is intended to be depressed, and the flag BRAKE is determined when it is determined that the brake pedal BP is not depressed. Is set to “0 (non-braking)”.

  Next, the CPU 51 proceeds to step 430, and the accelerator pedal by the driver is comprehensively determined from information such as the value of the accelerator pedal operation amount Accp detected by the accelerator operation amount sensor 43, the state of the accelerator switch (not shown), the state of the idle switch, and the like. The presence or absence of the AP's intention to step in is determined. As a result, if the CPU 51 determines that there is an intention to depress the accelerator pedal AP, it sets the value of the flag ACCEL to “1 (AP: ON)”, and if it determines that there is no intention to depress the accelerator pedal AP, The value of ACCEL is set to “0 (AP: OFF)”.

  Then, the CPU 51 proceeds to step 435 to set the estimated vehicle body speed previous value Vsob to the value of the estimated vehicle body speed Vso obtained in step 410 and the vehicle body acceleration previous value DVsob to the value of the vehicle body acceleration DVso obtained in step 415. The value is set, and the routine proceeds to step 495 to end the present routine tentatively. The above processing is repeatedly executed every elapse of a predetermined time (for example, 6 msec).

(Pre-actuation Bragg setting)
Further, the CPU 51 repeatedly executes a routine for setting the pre-operation flag PRE shown in FIG. 5 every elapse of a predetermined time (for example, 6 msec). Here, “pre-operation” means the hydraulic pump HP ** (accordingly, the motors Mf, Mr) from the time before the operation of the brake pedal BP is started (time t2 in the example of FIG. 3). Means to activate the system early.

  Therefore, when the predetermined timing is reached, the CPU 51 starts the process from step 500, proceeds to step 505, and determines whether or not the value of the pre-operation flag PRE at present is “0”. Here, when the value of the pre-operation flag PRE is “1”, the pre-operation flag indicates a state in which the condition for performing the pre-operation is satisfied, and when the value is “0”, the condition for performing the pre-operation. The state where is not established.

  Assuming that the value of the pre-operation flag PRE is “0”, the CPU 51 determines “Yes” when the process proceeds to step 505, proceeds to step 510, and the estimated vehicle body speed Vso calculated at step 410 is When it is determined whether or not the value is equal to or higher than a value obtained by adding a predetermined positive value β to the upper limit value Vc of the creep speed generated by the action of the torque converter of the automatic transmission (not shown). Proceed to

  When the CPU 51 proceeds to step 515, it determines whether or not the value of the flag BRAKE set in step 425 is “0” (that is, whether it is not braking), and determines “Yes”. The process proceeds to step 520.

  When the CPU 51 proceeds to step 520, the CPU 51 determines whether or not the time differential value DDVso of the vehicle body acceleration calculated in step 420 is equal to or less than the “negative predetermined value−α” and determines “Yes”. (That is, when all the conditions of steps 510, 515, and 520 are satisfied), the process proceeds to step 530, the value of the pre-operation flag PRE is changed from “0” to “1”, and then the process proceeds to step 595. Exit once. That is, the conditions for performing the pre-operation are satisfied when all of the conditions of steps 510, 515, and 520 are satisfied.

  Here, due to the presence of the condition of step 510, when the estimated vehicle speed Vso is an extremely low speed less than (Vc + β), the condition for performing the pre-operation is not satisfied. As a result, it is possible to prevent a situation in which the pre-operation is performed unnecessarily when the level of the pre-operation is low, and as a result, an increase in energy consumption can be suppressed.

  On the other hand, if any of the conditions of Steps 510 and 515 is not satisfied, the CPU 51 makes a “No” determination when proceeding to Step 510 or Step 515 and immediately proceeds to Step 595 to end the present routine tentatively. As a result, the value of the pre-operation flag PRE is maintained at “0” (that is, the condition for performing the pre-operation is not satisfied).

  In addition, if both the conditions of steps 510 and 515 are satisfied and only the condition of step 520 is not satisfied, the CPU 51 makes a “No” determination at step 520 to proceed to step 525, where the value of the flag ACCEL is “0”. It is determined whether or not there is. If the determination is “No”, the CPU 51 immediately proceeds to step 595. As a result, the value of the pre-operation flag PRE is maintained at “0”.

  In this case, the return speed of the driver's accelerator pedal AP is low and the condition of “DDVso ≦ −α” representing the deceleration behavior of the vehicle is not satisfied, and the accelerator pedal operation amount Accp is set to “0”. It corresponds to the case where it has not reached. In this case, it is difficult to predict that the driver intends to decelerate and that the operation of the brake pedal BP is started thereafter (immediately after). Therefore, as described above, the pre-operation condition is not established by maintaining the value of the pre-operation flag PRE at “0”.

  On the other hand, if the determination in step 525 is “Yes”, the CPU 51 proceeds to step 530 described above and changes the value of the pre-operation flag PRE from “0” to “1”. That is, in this case, a condition for performing the pre-operation is satisfied. This case corresponds to the case where the accelerator pedal operation amount Accp reaches “0” although the return speed of the accelerator pedal AP of the driver is low and the condition of “DDVso ≦ −α” indicating the vehicle deceleration behavior is not satisfied. is doing.

  In this case, similarly to the device described in Patent Document 1, it is possible to predict that the driver intends to decelerate and the operation of the brake pedal BP is started thereafter (immediately after). Accordingly, as described above, the value of the pre-operation flag PRE is set to “1”, and the condition for performing the pre-operation is established in this case as well.

  Next, the case where the value of the pre-operation flag PRE at the present time is “1” (that is, the condition for performing the pre-operation is satisfied) will be described. In this case, the CPU 51 makes a “No” determination when proceeding to step 505, proceeds to step 535, determines whether or not the estimated vehicle body speed Vso is equal to or lower than the upper limit value of the creep speed, and determines “Yes”. If so, the process proceeds to step 550 and the value of the pre-operation flag PRE is changed from “1” to “0”.

  When determining “No” in the determination of step 535, the CPU 51 proceeds to step 540 to determine whether or not the value of the flag BRAKE is “1” (that is, whether the brake is being applied). ”, The process proceeds to step 550 described above.

  When determining “No” in the determination of step 540, the CPU 51 proceeds to step 545 to determine whether or not the time during which the value of the flag ACCEL is maintained at “1” continues for a predetermined time. ”, The process proceeds to step 550 described above. That is, the condition for canceling the establishment of the condition for performing the pre-operation is satisfied when any one of the conditions of Steps 535, 540, and 545 is satisfied.

  On the other hand, when all the conditions of steps 535, 540, and 545 are not satisfied (that is, when the condition for canceling the condition for performing the pre-operation is not satisfied), the CPU 51 determines “No” in step 545. Determine and proceed immediately to step 595. As a result, the value of the pre-operation flag PRE is maintained at “1”. As a result, the state where the conditions for performing the pre-operation are satisfied is maintained.

  As described above, the value of the pre-operation flag PRE is sequentially updated to a value of “1” or “0” every elapse of a predetermined time (for example, 6 msec).

(Control of motor and pump)
Further, the CPU 51 repeatedly executes a routine for controlling the motors Mf, Mr and the hydraulic pump HP ** shown in FIG. 6 every elapse of a predetermined time (for example, 6 msec). Accordingly, when the predetermined timing comes, the CPU 51 starts the process from step 600 and proceeds to step 605 to determine whether or not at least one of the value of the flag BRAKE and the value of the pre-operation flag PRE is “1”. judge.

  When the CPU 51 determines “Yes” in Step 605 (that is, when braking is being performed, or when the condition for performing pre-operation is not satisfied while braking is being performed), the CPU 51 proceeds to Step 610. After instructing the motors Mf and Mr (and hence the hydraulic pump HP **) to operate together, the routine proceeds to step 695 and this routine is temporarily terminated.

  Thereafter, as long as the condition of step 605 is satisfied, the CPU 51 repeatedly executes the processes of steps 605 and 610. As a result, the operations of the motors Mf and Mr (and hence the hydraulic pump HP **) are continued.

  On the other hand, when the condition of step 605 is not satisfied (that is, when the braking is not being performed and the condition for performing the pre-operation is not satisfied), the CPU 51 determines “No” at step 605 to determine step 615. Then, after giving an instruction to stop the operation of the motors Mf, Mr (and therefore the hydraulic pump HP **), the routine proceeds to step 695 and this routine is once terminated.

  Thereafter, as long as the condition of step 605 is not satisfied, the CPU 51 repeatedly executes the processes of steps 605 and 615. As a result, the motors Mf and Mr (and hence the hydraulic pump HP **) continue to be stopped. Note that the routines of FIGS. 5 and 6 correspond to pump operation start means.

(Brake fluid pressure control)
Further, the CPU 51 repeatedly executes a routine for controlling the brake fluid pressure shown in FIG. 7 every elapse of a predetermined time (for example, 6 msec). Therefore, when the predetermined timing is reached, the CPU 51 starts processing from step 700 and proceeds to step 705 where the value of the flag BRAKE is “1” and the brake pedal stroke St obtained from the stroke sensor 42 is set. It is determined whether or not the value is greater than “0”.

  When the CPU 51 determines “Yes” in step 705 (that is, when braking and the brake pedal BP is operated), the CPU 51 proceeds to step 710 and determines the value of the brake pedal stroke St and the brake pedal stroke St. The target hydraulic pressure Pwt ** of the wheel cylinder hydraulic pressure Pw ** is determined for each wheel based on a predetermined table that defines the relationship between the target hydraulic pressure Pwt ** and the target hydraulic pressure Pwt **.

  Then, the CPU 51 proceeds to step 715 and normally opens so that the wheel cylinder hydraulic pressure Pw ** obtained from the wheel cylinder hydraulic pressure sensor 44 ** coincides with the determined target hydraulic pressure Pwt **. After giving an instruction to control the linear electromagnetic valve LV **, the routine proceeds to step 795 to end the present routine tentatively. As a result, the wheel cylinder hydraulic pressure Pw ** is adjusted to the optimum value described above according to the brake pedal stroke St.

  On the other hand, when the CPU 51 determines “No” in Step 705 (that is, when the brake pedal BP is not operated (including the case where the value of the pre-operation flag PRE is “1”)), Step 720 is performed. Proceed to step 4 to de-energize all normally open linear solenoid valves LV **. Thereby, the wheel cylinder hydraulic pressure Pw ** is maintained at “0”.

  As described above, the normally open solenoid valve is used as the solenoid valve, so that the excitation period of the solenoid valve can be set only during the operation of the brake pedal BP. As a result, an increase in energy consumption is suppressed. can do. The routine of FIG. 7 corresponds to brake fluid pressure control means.

  As described above, the brake (control) device that is the brake-by-wire system according to the embodiment of the present invention is capable of time differentiation of the vehicle body acceleration even before the operation of the brake pedal BP is started. It is predicted that the operation of the brake pedal BP will be started after (immediately after) when the value DDVso becomes equal to or less than “negative predetermined value −α” (that is, when a clear deceleration behavior of the vehicle is detected). In principle, the operation of the hydraulic pump HP ** is started. As a result, the time (according to time t2 in FIG. 3) before the time (according to time t3 in FIG. 3) when the accelerator pedal operation amount Accp becomes “0”, that is, the operation start time of the brake pedal BP (in FIG. 3). The operation of the hydraulic pump HP ** can be started at an early stage from a time point sufficiently before time t4).

  Therefore, it can be ensured that the rotation speed of the hydraulic pump HP ** is sufficiently increased at the operation start time of the brake pedal BP (time t4 in FIG. 3). As a result, even when the brake pedal BP is suddenly operated, the wheel cylinder hydraulic pressure Pw ** is promptly determined according to the brake pedal stroke St after the brake operation start time (after time t4 in FIG. 3). The target value can be made to follow.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the time differential value DDVso of the vehicle body acceleration DVso is used as a deceleration behavior index value for detecting a clear deceleration behavior of the vehicle, but the vehicle body acceleration DVso itself may be used.

  Moreover, in the said embodiment, although a normally open linear solenoid valve is used as a solenoid valve for adjusting wheel cylinder hydraulic pressure, a normally closed linear solenoid valve may be used. Furthermore, an open / close valve (ON-OFF valve) may be used instead of a linear valve as an electromagnetic valve for adjusting the wheel cylinder hydraulic pressure.

  In addition, in the above-described embodiment, the hydraulic unit 30 includes two brake fluid pressure circuits (a front wheel system related to the front two wheels FL and FR and a rear wheel system related to the rear two wheels RL and RR) ( 2) brake fluid pressure circuit (so-called cross piping) consisting of a system related to the left front wheel FL and the right rear wheel RR and a system related to the right front wheel FR and the left rear wheel RL. You may comprise so that it may be provided.

1 is a schematic configuration diagram of a vehicle equipped with a brake device according to an embodiment of the present invention. It is a schematic block diagram of the hydraulic unit shown in FIG. 6 is a time chart showing an example of changes in brake pedal stroke, accelerator pedal operation amount, vehicle body acceleration, and time differential values of vehicle body acceleration when the driver starts operating the brake pedal. 2 is a flowchart showing a routine for calculating wheel speeds and the like executed by a CPU shown in FIG. 1. It is the flowchart which showed the routine for setting the pre-operation flag which CPU shown in FIG. 1 performs. 2 is a flowchart showing a routine for controlling a motor / pump executed by a CPU shown in FIG. 2 is a flowchart showing a routine for controlling brake fluid pressure executed by a CPU shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Brake device, 20 ... Stroke simulator, 30 ... Hydraulic unit, 41 ** ... Wheel speed sensor, 42 ... Stroke sensor, 43 ... Accelerator operation amount sensor, 44 ... Wheel cylinder hydraulic pressure sensor, 50 ... Electric control device, 51 ... CPU, HP ** ... Hydraulic pump, LV ** ... Normally open linear solenoid valve, Mf, Mr ... Motor

Claims (6)

A hydraulic pump for generating brake hydraulic pressure in the vehicle wheel cylinder;
Brake hydraulic pressure control means for controlling the brake hydraulic pressure in the wheel cylinder generated by the operation of the hydraulic pressure pump to a value corresponding to the operation of the brake operating member when the driver operates the brake operating member When,
A vehicle brake control device applied to a vehicle brake device comprising:
As a deceleration behavior index value that is a value representing the degree of deceleration behavior of the vehicle, a deceleration behavior index value acquisition unit that acquires a time differential value of acceleration in the vehicle longitudinal direction of the vehicle ;
When the time differential value of acceleration in the longitudinal direction of the vehicle acquired by the deceleration behavior index value acquisition means becomes equal to or less than a negative predetermined value, the driver starts operating the brake operation member thereafter. Brake operation start prediction means for predicting,
Even when the driver does not operate the brake operating member , the brake operation start predicting means predicts that the driver will start the operation of the brake operating member. Pump operation start means for starting the operation of the pressure pump;
A brake control device for a vehicle comprising: The vehicle brake control device according to claim 1 ,
The pump operation start means is
Even when the driver does not operate the brake operation member , the vehicle body speed of the vehicle is equal to or higher than a predetermined speed, and the brake operation member is operated by the driver by the brake operation start prediction unit. The vehicle brake control device is configured to start the operation of the hydraulic pump when the operation is predicted to be started. A solenoid valve interposed between the reservoir and the wheel cylinder;
A hydraulic pump that discharges brake fluid between the solenoid valve and the wheel cylinder;
When the driver operates the brake operation member, the hydraulic pressure pump is operated and the brake hydraulic pressure in the wheel cylinder generated by the operation of the hydraulic pressure pump is in accordance with the operation of the brake operation member. Brake fluid pressure control means for controlling the solenoid valve to be a value,
A vehicle brake device comprising:
As a deceleration behavior index value that is a value representing the degree of deceleration behavior of the vehicle, a deceleration behavior index value acquisition unit that acquires a time differential value of acceleration in the vehicle longitudinal direction of the vehicle ;
When the time differential value of acceleration in the longitudinal direction of the vehicle acquired by the deceleration behavior index value acquisition means becomes equal to or less than a negative predetermined value, the driver starts operating the brake operation member thereafter. Brake operation start prediction means for predicting,
Even when the driver does not operate the brake operating member , the brake operation start predicting means predicts that the driver will start the operation of the brake operating member. Pump operation start means for starting the operation of the pressure pump;
Brake device for vehicles equipped with. The vehicle brake device according to claim 3 ,
The electromagnetic valve is a brake device for a vehicle which is a normally open type electromagnetic valve. The vehicle brake device according to claim 4 ,
The normally open solenoid valve is a vehicle brake device that is a linear solenoid valve. The vehicle brake device according to claim 5 ,
The pump operation start means is
Even when the driver does not operate the brake operation member , the vehicle body speed of the vehicle is equal to or higher than a predetermined speed, and the brake operation member is operated by the driver by the brake operation start prediction unit. The vehicle brake device is configured to start the operation of the hydraulic pump when the operation is predicted to be started.

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