JP2006142902A - Hill hold braking force control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hill hold braking force control device of a vehicle enabling smooth starting by improving starting performance and climbing ability in starting on a slope when releasing hill hold braking force of front and rear wheels. <P>SOLUTION: The hill hold braking force control device of the vehicle has at least one motor mounted in power source for driving the wheels, a motor traction control means for restoring grip of the wheels by motor torque-down control when detecting driving slip of the wheels, and a hill hold braking force control means for preventing the vehicle from retreating by holding braking force of the front and rear wheels when stopping on the slope. The hill hold braking force control means releases driving wheel braking force later than driven wheel braking force in starting on the slope when releasing braking force of the front and rear wheels. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hill hold braking force control device for a vehicle that is applied to a hybrid vehicle, an electric vehicle, or the like and that has at least one motor as a power source for driving wheels.

  In a hybrid vehicle equipped with a motor as the power source, when the drive wheel slips, the motor over-rotates in accordance with the drive slip and an overcurrent is generated in the motor drive circuit. Needs to converge the driving slip with good response. The motor traction control device for converging the drive slip for the purpose of protecting the components is configured to predict that the drive slip will occur when the change rate (angular acceleration) of the rotational angular velocity of the drive wheel is equal to or greater than a predetermined value, and to reduce the motor torque. And driving slip that occurs with an increase in motor torque is prevented (see, for example, Patent Document 1).

Conventionally, when a driver stops on a hill and switches his foot from the brake pedal to the accelerator pedal, so-called hill hold brake control is performed to prevent the vehicle from moving backward by maintaining the braking pressure in the wheel cylinder. A brake device is known (see, for example, Patent Document 2).
JP-A-10-304514 JP-A-10-181575

  However, in the brake device that executes the above-described conventional hill hold brake control, the braking force distribution of the front and rear wheels has not been studied, and the driving wheel braking force is also obeyed when starting a slope that releases the braking force of the front and rear wheels. Since the driving wheel braking force is also released at the same time, in a scene where the hydraulic pressure of the driving wheel is suddenly released, when the driving wheel slips up and motor traction control is started, the motor torque decreases and the vehicle starts off. Performance and climbing ability will decrease. In addition, if the driving wheel braking force and the driven wheel braking force are released at the same time, there is a problem that the drag resistance is too large to ensure a seamless start.

  The present invention has been made paying attention to the above-mentioned problem. When starting a hill where the hill hold braking force of the front and rear wheels is released, the vehicle hill can improve the starting performance and the climbing ability and realize a seamless start. An object of the present invention is to provide a hold braking force control device.

In order to achieve the above object, the vehicle hill hold braking force control device according to the present invention includes at least one motor provided in a power source for driving the wheel, and a wheel grip by motor torque down control when a wheel drive slip is detected. In a hill hold braking force control device for a vehicle, comprising: motor traction control means for recovering the vehicle, and hill hold braking force control means for preventing the vehicle from moving backward by maintaining the braking force of the front and rear wheels when the hill stops. ,
The hill hold braking force control means releases the driving wheel braking force later than the driven wheel braking force when starting on a slope where the braking force of the front and rear wheels is released.

  Therefore, in the hill hold braking force control device for a vehicle according to the present invention, when the hill hold braking force control means releases the braking force of the front and rear wheels, the driving wheel braking force is released later than the driven wheel braking force. Is done. That is, while maintaining the hill hold property on the drive wheel side where the braking force is released slowly, the drag resistance is reduced on the driven wheel side where the braking force is released earlier, and the occurrence of a drive slip that causes a reduction in motor torque or a large amount Generation of drag resistance is eliminated. As a result, at the time of starting on a hill where the hill hold braking force of the front and rear wheels is released, the starting performance and the climbing ability can be improved, and a seamless start can be realized.

  Hereinafter, the best mode for realizing a hill hold braking force control device for a vehicle according to the present invention will be described based on a first embodiment shown in the drawings.

First, the drive system configuration of the hybrid vehicle will be described.
FIG. 1 is an overall system diagram showing a drive system of a hybrid vehicle to which the motor traction control device of Embodiment 1 is applied. As shown in FIG. 1, the drive system of the hybrid vehicle in the first embodiment includes an engine E, a first motor generator MG1, a second motor generator MG2 (motor), an output sprocket OS, and a power split mechanism TM. Have.

  The engine E is a gasoline engine or a diesel engine, and the opening degree of a throttle valve and the like are controlled based on a control command from an engine controller 1 described later.

The first motor generator MG1 and the second motor generator MG2 are synchronous motor generators in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator. Based on a control command from the motor controller 2 described later, Each is controlled independently by applying a three-phase alternating current generated by the control unit 3.
Both of the motor generators MG1 and MG2 can operate as electric motors that are rotated by receiving power supplied from the battery 4 (hereinafter, this state is referred to as “powering”), and the rotor is rotated by an external force. If it is, the battery 4 can be charged by functioning as a generator that generates electromotive force at both ends of the stator coil (hereinafter, this state is referred to as “regeneration”).

  The power split mechanism TM is configured by a simple planetary gear having a sun gear S, a pinion P, a ring gear R, and a pinion carrier PC. And the connection relationship of the input / output member with respect to the three rotating elements (sun gear S, ring gear R, and pinion carrier PC) of the simple planetary gear will be described. A first motor generator MG1 is connected to the sun gear S. A second motor generator MG2 and an output sprocket OS are connected to the ring gear R. An engine E is connected to the pinion carrier PC via an engine damper ED. The output sprocket OS is connected to the left and right front wheels via a chain belt CB, a differential and a drive shaft (not shown).

Due to the above connection relationship, the first motor generator MG1 (sun gear S), the engine E (planet carrier PC), the second motor generator MG2 and the output sprocket OS (ring gear R) are arranged in this order on the alignment chart shown in FIG. It is possible to introduce a rigid lever model (a relationship in which three rotational speeds are always connected by a straight line) that can simply express the dynamic operation of a simple planetary gear.
Here, the “collinear diagram” is a velocity diagram used in a simple and easy-to-understand method of drawing instead of the method of obtaining by equation when considering the gear ratio of the differential gear, Take the number of rotations (rotation speed) of the rotating elements, take each rotating element on the horizontal axis, and based on the gear ratio λ of sun gear S and ring gear R, the interval between each rotating element (S ~ PC): (PC ~ R ) Length ratio is 1: λ.

Next, the control system of the hybrid vehicle will be described.
As shown in FIG. 1, the hybrid vehicle control system in the first embodiment includes an engine controller 1, a motor controller 2, a power control unit 3 (high power unit), a battery 4 (secondary battery), and a brake controller 5. And an integrated controller 6.

  The integrated controller 6 receives input information from an accelerator opening sensor 7, a vehicle speed sensor 8, an engine speed sensor 9, a first motor generator speed sensor 10, and a second motor generator speed sensor 11. Brought about. Note that the vehicle speed sensor 8 and the second motor generator rotation speed sensor 11 are for detecting the output rotation speed of the same power split mechanism TM, so the vehicle speed sensor 8 is omitted and the second motor generator rotation speed sensor 11 The sensor signal may be used as a vehicle speed signal. Note that the motor controller 2 provides information on the battery S.O.C representing the state of charge of the battery 4.

  The brake controller 5 includes a front left wheel speed sensor 12, a front right wheel speed sensor 13, a rear left wheel speed sensor 14, a rear right wheel speed sensor 15, a steering angle sensor 16, and a master cylinder pressure sensor 17. The brake stroke sensor 18 provides input information.

  The engine controller 1 responds to an engine operating point (Ne) according to a target engine torque command or the like from an integrated controller 6 that inputs an accelerator opening AP from an accelerator opening sensor 7 and an engine speed Ne from an engine speed sensor 9. , Te), for example, is output to a throttle valve actuator (not shown).

  The motor controller 2 receives the motor of the first motor generator MG1 in response to a target motor generator torque command or the like from the integrated controller 6 that inputs the motor generator rotational speeds N1 and N2 from the motor generator rotational speed sensors 10 and 11 by the resolver. A command for independently controlling the operating point (N1, T1) and the motor operating point (N2, T2) of the second motor generator MG2 is output to the power control unit 3.

  The power control unit 3 constitutes a high-power unit with a high voltage of the power supply system that can supply power to both motor generators MG1 and MG2 with a smaller current. As shown in FIG. It has a converter 3b, a drive motor inverter 3c, a generator generator inverter 3d, and a capacitor 3e. A drive motor inverter 3c is connected to the stator coil of the second motor generator MG2. A generator generator inverter 3d is connected to the stator coil of the first motor generator MG1. The joint box 3a is connected to a battery 4 that is discharged during power running and charged during regeneration.

  The brake controller 5 performs ABS control according to a control command to a brake hydraulic pressure unit 19 that independently controls the brake hydraulic pressure of the four wheels during low-μ road braking, sudden braking, and the like. At the time of braking by the brake, regenerative brake cooperative control is performed by issuing a control command to the integrated controller 6 and a control command to the brake hydraulic pressure unit 19. Furthermore, when the driver stops on a hill and switches his foot from the brake pedal to the accelerator pedal, so-called hill hold brake control is performed to prevent the vehicle from moving backward by maintaining the brake fluid pressure in the wheel cylinder. .

  The brake controller 5 includes wheel speed information from the wheel speed sensors 12, 13, 14, 15, steering angle information from the steering angle sensor 16, braking operation from the master cylinder pressure sensor 17 and the brake stroke sensor 18. Quantity information is entered. And based on these input information, a predetermined calculation process is performed and the control command by the process result is output to the integrated controller 6 and the brake hydraulic pressure unit 19. A front left wheel wheel cylinder 20, a front right wheel wheel cylinder 21, a rear left wheel wheel cylinder 22, and a rear right wheel wheel cylinder 23 are connected to the brake fluid pressure unit 19.

  The integrated controller 6 manages the energy consumption of the entire vehicle and has a function for running the vehicle with the highest efficiency. The integrated controller 6 performs engine operating point control by a control command to the engine controller 1 during acceleration running or the like. In addition, the motor generator operating point control is performed by a control command to the motor controller 2 at the time of stopping, running, braking, or the like. The integrated controller 6 includes the accelerator opening AP, the vehicle speed VSP, the engine speed Ne, the first motor generator speed N1, and the second motor generator speed N2 from the sensors 7, 8, 9, 10, and 11. Entered. And based on these input information, a predetermined calculation process is performed and the control command by the process result is output to the engine controller 1 and the motor controller 2. FIG. The integrated controller 6 and the engine controller 1, the integrated controller 6 and the motor controller 2, and the integrated controller 6 and the brake controller 5 are connected by bidirectional communication lines 24, 25, and 26, respectively, for information exchange.

Next, the configuration of the hill hold brake control device will be described.
As shown in FIG. 6, the hill hold brake control device of the first embodiment includes an integrated controller 6, a brake controller 5, a brake actuator having a brake hydraulic unit 19 and wheel cylinders 20, 21, 22, and 23, Consists of.
The integrated controller 6 includes a torque command calculation unit 6a for inputting sensor signals from the accelerator opening sensor 7 and the vehicle speed sensor 8, a sensor signal from the accelerator opening sensor 7 and the vehicle speed sensor 8, and a torque command calculation unit 6a. And a climbing amount estimation calculation unit 6b for inputting a calculation result from.
The brake controller 5 includes a hill hold torque calculation unit 5 a that inputs a calculation result from the climbing amount estimation calculation unit 6 b and a sensor signal from the brake stroke sensor 18. The details of the calculation processing in the torque command calculation unit 6a, the climbing amount estimation calculation unit 6b, and the hill hold torque calculation unit 5a will be described in detail with reference to the flowchart shown in FIG.

Next, driving force performance will be described.
As shown in FIG. 2 (b), the driving force of the hybrid vehicle of the first embodiment includes the engine direct driving force (the driving force obtained by subtracting the generator driving amount from the total engine driving force) and the motor driving force (both motor generators MG1). , Driving force by the sum of MG2). As shown in FIG. 2A, the maximum driving force is configured such that the lower the vehicle speed, the greater the motor driving force. In this way, since the vehicle does not have a transmission and travels by adding the direct driving force of the engine E and the motor driving force that is electrically converted, the full power of the accelerator pedal is fully opened from low speed to high speed from the state of low steady driving power. Until now, it is possible to control the driving force seamlessly with good response to the driver's required driving force (torque on demand).
In the hybrid vehicle of the first embodiment, the engine E, the motor generators MG1 and MG2, and the left and right front wheels (wheels) are connected without a clutch via the power split mechanism TM. Further, as described above, most of the engine power is converted into electric energy by a generator, and the vehicle is driven by a motor with high output and high response. For this reason, for example, when driving on a slippery road such as an ice burn, when the driving force of the vehicle changes suddenly due to wheel slip or wheel lock during braking, the parts of the power control unit 3 are protected from excessive current. Alternatively, it is necessary to protect the parts from over-rotation of the pinion of the power split mechanism TM. On the other hand, utilizing the characteristics of motors with high output and high response, we have developed from the component protection function to detect the driving slip of the wheel instantly, recover the grip, and motor traction to drive the vehicle safely Adopt control.

Next, the braking force performance will be described.
In the hybrid vehicle of the first embodiment, the kinetic energy of the vehicle is converted into electric energy by operating the second motor generator MG2 operating as a motor as a generator (generator) during braking by an engine brake or a foot brake. Then, a regenerative braking system that recovers and reuses the battery 4 is adopted.
As shown in Fig. 3 (a), the general regenerative brake cooperative control in this regenerative brake system calculates the required braking force with respect to the brake pedal depression amount, regardless of the magnitude of the required braking force. The required braking force is shared by the regenerative component and the hydraulic component.
In contrast, the regenerative brake cooperative control employed in the hybrid vehicle of the first embodiment calculates the required braking force with respect to the brake pedal depression amount as shown in FIG. 3 (b), and calculates the calculated required braking force. On the other hand, the regenerative brake is given priority, and as long as the regenerative portion can cover it, the regenerative portion is expanded to the maximum without using the hydraulic component. Thereby, especially in a traveling pattern in which acceleration / deceleration is repeated, energy recovery efficiency is high, and energy recovery by regenerative braking is realized up to a lower vehicle speed.

Next, the vehicle mode will be described.
As the vehicle mode in the hybrid vehicle of the first embodiment, as shown in the collinear diagram of FIG. 4, “stop mode”, “start mode”, “engine start mode”, “steady travel mode”, “acceleration mode” Have
In the “stop mode”, as shown in FIG. 4A, the engine E, the generator MG1, and the motor MG2 are stopped. In the “start mode”, as shown in FIG. 4 (2), the vehicle starts by driving only the motor MG2. In the “engine start mode”, as shown in FIG. 4 (3), the sun gear S rotates to start the engine E by the generator MG1 having a function as an engine starter. In the “steady travel mode”, as shown in FIG. 4 (4), the vehicle travels mainly by the engine E, and power generation is minimized in order to increase efficiency. In the “acceleration mode”, as shown in FIG. 4 (5), the engine E is rotated and the generator MG1 starts generating power. The electric power of the battery 4 is used to increase the driving force of the motor MG2. In addition, it accelerates.
In reverse running, in the “steady running mode” shown in FIG. 4 (4), if the rotation speed of the generator MG1 is increased while the increase in the rotation speed of the engine E is suppressed, the rotation speed of the motor MG2 becomes negative. Transition and reverse travel can be achieved.

  At the time of start-up, when the ignition key is turned, the engine E starts, and after the engine E is warmed up, the engine E stops immediately. When starting or at a light load, when starting or when going down a gentle hill that runs at a very low speed, the fuel is cut in areas where engine efficiency is low, and the engine stops and the motor MG2 runs. During normal travel, the driving force of the engine E is driven directly by one of the wheels by the power split mechanism TM, while the other drives the generator MG1 and assists the motor MG2. At the time of full open acceleration, power is supplied from the battery 4 and further driving force is added. When decelerating or braking, the wheel drives the motor MG2 and acts as a generator to perform regenerative power generation. The collected electrical energy is stored in the battery 4. When the charge amount of the battery 4 decreases, the generator MG1 is driven by the engine E and charging is started. When the vehicle is stopped, the engine E is automatically stopped except when the air conditioner is used or when the battery is charged.

Next, the operation will be described.
[Hill hold brake control processing]
FIG. 7 is a flowchart showing the flow of the hill hold brake control process executed by the integrated controller 6 and the brake controller 5 of the first embodiment. Each step will be described below (hill hold brake control means).

  In step S1, the accelerator opening is calculated based on the sensor signal from the accelerator opening sensor 7, and the process proceeds to step S2.

In step S2, following the calculation of the accelerator opening in step S1, the vehicle speed is calculated based on the sensor signal from the vehicle speed sensor 8, and the process proceeds to step S3.
Here, as for the vehicle speed information, the wheel speed may be calculated based on sensor signals from the wheel speed sensors 12, 13, 14, 15 instead of the vehicle speed calculation.

In step S3, following the vehicle speed calculation in step S2, a torque command (driver required torque) is calculated based on the accelerator opening information and the vehicle speed information, and the process proceeds to step S4.
Here, as the “torque command (driver required torque)”, for example, a driving force map (accelerator opening × vehicle speed × driving torque) (not shown) is prepared in advance, and the driving force map is calculated from the accelerator opening information and the vehicle speed information. Search to calculate torque command.

In step S4, following the calculation of the torque command in step S3, the climbing amount is estimated based on the torque command, the vehicle speed, and the accelerator opening, and the process proceeds to step S5 (road surface gradient detecting means).
Here, the “climbing amount (= road surface gradient)” is estimated according to whether the vehicle speed is lower or higher than the vehicle speed estimated by the torque command. Further, when the vehicle moves backward when the vehicle stops, the gradient is estimated according to the reverse amount (change amount). The above processing is performed by the integrated controller 6.

  In step S5, following the uphill amount estimation calculation in step S4, the brake stroke is calculated based on the sensor signal from the brake stroke sensor 17.

  In step S6, following the calculation of the brake stroke in step S5, the road surface gradient value (= climbing amount) estimated in step S4 is input, and the process proceeds to step S7.

In step S7, following the input of the road surface gradient value in step S6, the hill hold torque is calculated according to the road surface gradient value, and the process proceeds to step S8.
Here, the “hill hold torque” is a torque that keeps the vehicle stopped on a slope, and as shown in FIG. 8, the hill hold torque increases as the road gradient value (%) increases. .

In step S8, following the calculation of the hill hold torque in step S7, the responsiveness of the front (driving wheel) braking force and the responsiveness of the rear (driven wheel) braking force are determined according to the road surface gradient value, and the process proceeds to step S9. Transition.
Here, as shown in FIG. 9, the “responsiveness of the front braking force and the responsiveness of the rear braking force” increases the time constant of the front braking force when the front braking force and the rear braking force are compared. By setting the value, the response of the front braking force is made slower than the response of the rear braking force. Further, the response to decrease in the front braking force and the decrease in response to the rear braking force with respect to the road surface gradient value (%) are accelerated by decreasing the time constant as the road surface gradient value (%) increases. Furthermore, the difference between the lower response of the front braking force and the lower response of the rear braking force is set to increase as the road surface gradient value (%) increases.

In step S9, following the response determination of the front braking force and the rear braking force in step S8, a torque command for obtaining the front EBD hydraulic pressure and the rear EBD hydraulic pressure based on the determined response is given to the brake hydraulic pressure unit 19. Output and move to return.
That is, when the hill hold control is started when the hill is stopped, after the rear EBD hydraulic pressure reaches the target hydraulic pressure, as shown in the EBD hydraulic pressure characteristic of FIG. You will be commanded to reach the hydraulic pressure. Here, "EBD (abbreviation of Electoric Brake force Distribution)" refers to an electronically controlled braking force distribution system, and it is possible to control the front wheel braking force characteristic and the rear wheel braking force characteristic separately by applying the ABS system. It is a thing.

[Background of traction control]
For example, Japanese Patent Application Laid-Open No. 10-304514 discloses a technique (angular acceleration control) for improving torque down response in the initial stage of slip. This technique is often applied to a vehicle using a motor as a unit for generating a driving force, such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle. The basis of this technology is a configuration that predicts that drive slip will occur when the rate of change (angular acceleration) of the rotational angular velocity of the drive wheels is greater than or equal to a predetermined value, and reduces the motor torque. With this configuration, it is possible to prevent a drive slip that occurs with an increase in motor torque.

Here, the reason why “angular acceleration control” that suppresses slip with high responsiveness in the early stage of generation of drive slip in a hybrid vehicle using a motor as a unit for generating drive force will be described.
If there is no motor traction control device and the drive slips, the power generation of the engine cannot catch up and the motor draws more current from the battery. Therefore, an overcurrent is generated in the motor drive circuit, and the elements on the circuit are damaged. For example, in the power control unit 3 according to the first embodiment, as shown by the arrow in FIG. 5, when an overcurrent flows through the capacitor 3e, the fuse of the joint box 3a and the switching circuit of the boost converter 3b are damaged. There is a case. Moreover, in a hybrid vehicle or a fuel cell vehicle, overcurrent tends to flow as the motor output (motor output ratio) is larger than that of the secondary battery. In addition, overvoltage and overcurrent flow more easily as the output of the engine and fuel cell (engine output ratio) is larger than that of the secondary battery. There is a relationship. Therefore, in order to reliably protect the parts, it is necessary to perform motor traction control that converges the drive slip with good response by "angular acceleration control" in which torque is limited when slipping.

  However, in the conventional “angular acceleration control”, priority is given to component protection on a low μ road where drive slip is likely to occur, and a large motor torque down amount is provided when the occurrence of drive slip is predicted.

  On the other hand, for example, in Japanese Patent Application Laid-Open No. 10-181575, when a driver stops on a slope and switches his foot from a brake pedal to an accelerator pedal, the vehicle moves backward while maintaining the braking pressure in the wheel cylinder. A brake control device that performs so-called hill hold brake control is known. In such a brake control device, as described in the above publication, the hydraulic pressure of the master cylinder is confined in the wheel cylinder by closing the solenoid valve of the brake circuit capable of executing the existing ABS control. Can be achieved. And in performing this hill hold control, for example, if it is detected that the master cylinder hydraulic pressure has fallen below a preset hill hold start determination threshold as the brake pedal is changed, this is used as a start condition. Hill hold control was being executed. In other words, when the master cylinder hydraulic pressure falls below the hill hold start determination threshold, the solenoid valve is closed, so that the hydraulic pressure slightly lower than the hill hold start determination threshold is confined in the wheel cylinder. It is possible to confine the braking pressure required for stopping in the wheel cylinder.

  Therefore, assuming a hybrid vehicle equipped with both a motor traction control system based on "angular acceleration control" and a hill hold brake control system, the distribution of braking force between the front and rear wheels has not been studied in the conventional hill hold brake control. When starting on a slope where the braking force of the front and rear wheels is released, the driving wheel braking force and the driven wheel braking force are simultaneously released.

  Therefore, when the driving wheel braking force and the driven wheel braking force are released simultaneously at an early stage, the driving wheel slips up, and when "angular acceleration control (motor traction control)" is started, the motor torque decreases, Start performance and climbing ability will decrease. Especially in the scene where the hydraulic pressure of the driving wheel is suddenly released, the drive wheel slips up, causing a problem of voltage rise in the high voltage unit or overcurrent flowing into the single phase, causing significant damage to the system. May give.

  In addition, if the driving wheel braking force and the driven wheel braking force are released at the same time, the drag resistance is too large, and the longitudinal acceleration fluctuates due to the drag resistance with respect to the drive force trying to advance the vehicle. And it will be a jerky start.

[Hill hold brake control action]
In the first embodiment, when starting a hill where the hill hold braking force of the front and rear wheels is released, the driving wheel braking force is released later than the driven wheel braking force, thereby improving the starting performance and climbing ability and realizing a seamless start. I tried to do it.

  That is, when the vehicle is running on a hill or when the hill is stopped, the flow proceeds to step S1, step S2, step S3, step S4, step S5, step S6, step S7, step S8 in the flowchart of FIG. The response of the front braking force and the response of the rear braking force are determined according to the road surface gradient value. In the next step S9, when the start condition of the hill hall control is satisfied at the time of the slope stop, or the start from the slope stop If the release condition for the hill hall control is satisfied, the front hydraulic pressure and the rear hydraulic pressure are controlled by the response (time constant) determined in step S8.

  That is, in step S8, the time constant is determined so as to make the response of the front braking force slower than the response of the rear braking force (FIG. 9), so that the start condition of the hill hall control is satisfied when the hill stops. As shown in FIG. 11, the rear hydraulic pressure rises with a steep slope from time t0, and reaches the pressure regulation target value at time t1. On the other hand, the front hydraulic pressure rises with a gentle gradient from the time point t0, and reaches the pressure regulation target value at the time point t2 that is delayed from the time point t1.

  Further, when the condition for canceling the hill hall control is satisfied at the time of starting from the stop of the hill, as shown in FIG. 11, the rear hydraulic pressure decreases with a steep slope from the time point t2, and the zero liquid level is reached at the time point t3. Reach pressure. On the other hand, the front hydraulic pressure decreases with a gentle gradient from the time t2, and reaches the zero hydraulic pressure at a time t4 that is delayed from the time t3.

Therefore, as shown in FIG. 12, on the front wheel side (driving wheel side) where the braking force is released slowly, the rear wheel where the braking force is released quickly while maintaining the hill hold property due to the remaining front hydraulic pressure. On the side (driven wheel side), the rear hydraulic pressure is eliminated early, thereby reducing drag resistance.
In other words, the occurrence of slip on the front wheel side, which causes a reduction in motor torque, is eliminated as in the case where the hydraulic pressure is eliminated with high response at both the front and rear. The generation of a large drag resistance is eliminated as in the case of eliminating with.

As described above, in the first embodiment, at the time of starting on a hill where the hill hold braking force of the front and rear wheels is released, the start performance and the climbing ability can be improved, and a seamless start can be realized.
In addition, since the hydraulic pressure of the front wheels (drive wheels) is released slowly by slowing down the responsiveness of the front braking force, sudden changes in the wheel speed of the front wheels are effectively suppressed, It is possible to surely prevent a system from being seriously damaged by a voltage increase in a certain power control unit 3 or an overcurrent flowing into a single phase.

Next, the effect will be described.
In the vehicle hill hold braking force control apparatus according to the first embodiment, the following effects can be obtained.

  (1) At least one motor installed in the power source that drives the wheel, motor traction control means for recovering the grip of the wheel by motor torque down control when the driving slip of the wheel is detected, and braking force of the front and rear wheels when the hill is stopped And a hill hold braking force control device for preventing the vehicle from moving backward by maintaining the hill hold braking force control device. The hill hold braking force control device releases the braking force of the front and rear wheels. In order to release the driving wheel braking force later than the driven wheel braking force when starting a slope, the hill hold braking force of the front and rear wheels is released, improving the starting performance and climbing ability, and realizing a seamless start Can do.

  (2) The hill hold braking force control means makes the power control unit 3 in order to make the driving wheel braking force lowering response slower than the driven wheel braking force lowering response when starting the hill to release the braking force of the front and rear wheels. It is possible to surely prevent the system from being seriously damaged by an increase in voltage and an overcurrent flowing into a single phase.

  (3) Road surface gradient detecting means (step S4) for detecting the road surface gradient of the stopped hill is provided, and the hill hold braking force control means increases the driving wheel braking force with lower response as the road surface gradient increases. In order to speed up both driving wheel braking force reduction responsiveness, the higher the road surface gradient at the start, the lower the braking force characteristic that corresponds to increasing the driving force with better response, regardless of the slope of the road surface. Ability can be improved.

  (4) The hill hold braking force control means increases the difference between the drive wheel braking force decrease response and the driven wheel braking force decrease response as the road surface gradient increases. The braking force reduction characteristics correspond to the need to keep the hill hold property, and seamless start can be realized regardless of the slope of the road surface on the slope.

  (5) The motor traction control means detects angular acceleration of the driving wheel or motor, and performs “angular acceleration control” to recover the grip of the wheel by motor torque down control when the angular acceleration exceeds the set angular acceleration. When starting off a hill, it is possible to reliably prevent the vehicle from slipping down by entering “angular acceleration control” for protecting parts with a high torque-down speed and a large torque-down amount.

  As mentioned above, although the hill hold braking force control device for a vehicle according to the present invention has been described based on the first embodiment, the specific configuration is not limited to the first embodiment, and each claim of the claims Design changes and additions are permitted without departing from the spirit of the invention.

  In the first embodiment, an example is shown in which only “angular acceleration control” is executed as motor traction control. However, the present invention is also applicable to a motor that executes motor traction control combining “angular acceleration control” and “slip amount control”. it can.

  In the first embodiment, as a hill hold braking force control means, a preferable example is shown in which the driving wheel braking force lowering response and the driven wheel braking force lowering response are different when starting on a slope where the braking force of the front and rear wheels is released. However, in short, it is included even if the driving wheel braking force is released later than the driven wheel braking force when the vehicle starts moving on a slope to release the braking force of the front and rear wheels.

  In the first embodiment, an example of application to a hybrid vehicle including one engine, two motor generators, and a power split mechanism is shown. However, the hill hold braking force control device of the present invention is a hybrid including another power unit structure. In short, any vehicle such as a car, an electric vehicle, a fuel cell vehicle, a motor 4WD vehicle, etc., which is equipped with at least one motor as a power source for driving wheels can be applied.

1 is an overall system diagram illustrating a hybrid vehicle to which a hill hold braking force control device according to a first embodiment is applied. FIG. 2 is a driving force performance characteristic diagram and a driving force conceptual diagram in a hybrid vehicle to which the hill hold braking force control device of the first embodiment is applied. It is a contrast characteristic figure showing the braking force performance by regenerative cooperation in the hybrid vehicle to which the hill hold braking force control device of Example 1 was applied. It is a collinear diagram which shows each vehicle mode in the hybrid vehicle to which the hill hold braking force control apparatus of Example 1 was applied. It is a block diagram which shows the high electric power unit (battery, power control unit, 1st motor generator, 2nd motor generator) of the hybrid vehicle of Example 1. FIG. It is a control block diagram which shows the structure of the hill hold brake control apparatus of Example 1. FIG. It is a flowchart which shows the flow of the hill hold braking force control process performed with the integrated controller and brake controller of Example 1. FIG. It is a figure which shows an example of the hill hold torque characteristic with respect to the gradient calculated by the hill hold brake control in Example 1. FIG. It is a figure which shows an example of the time constant characteristic of a driving wheel and a driven wheel with respect to the gradient calculated by the hill hold brake control in Example 1. FIG. It is a figure which shows the raise characteristic of the target hydraulic pressure at the time of the hill hold brake control start in Example 1, the rear EBD hydraulic pressure, and the front EBD hydraulic pressure. It is a figure which shows each characteristic of the pressure regulation target value, rear hydraulic pressure, and front hydraulic pressure from the hill hold brake control start in hill hold brake control in Example 1 to hill hold brake control cancellation | release. FIG. 6 is an operation explanatory diagram illustrating a state in which hill hold performance is maintained at the time of start in a vehicle that executes hill hold brake control in the first embodiment.

Explanation of symbols

E engine
MG1 1st motor generator
MG2 Second motor generator (motor)
OS output sprocket
TM power split mechanism 1 engine controller 2 motor controller 3 power control unit 4 battery 5 brake controller 6 integrated controller 7 accelerator opening sensor 8 vehicle speed sensor 9 engine speed sensor 10 first motor generator speed sensor 11 second motor generator speed Sensor 12 Front left wheel speed sensor 13 Front right wheel speed sensor 14 Rear left wheel speed sensor 15 Rear right wheel speed sensor 16 Steering angle sensor 17 Master cylinder pressure sensor 18 Brake stroke sensor 19 Brake fluid pressure unit 20 Front left wheel wheel cylinder 21 Front right wheel wheel cylinder 22 Rear left wheel wheel cylinder 23 Rear right wheel wheel cylinder

Claims (5)

At least one motor provided in a power source for driving the wheel, motor traction control means for recovering the grip of the wheel by motor torque down control when detecting the driving slip of the wheel, and maintaining the braking force of the front and rear wheels when the hill is stopped In a hill hold braking force control device for a vehicle, comprising a hill hold braking force control means for preventing the vehicle from retreating,
The hill hold braking force control device releases a driving wheel braking force later than a driven wheel braking force when starting a slope for releasing the braking force of front and rear wheels. In the vehicle hill hold braking force control device according to claim 1,
The hill hold braking force control means makes the drive wheel braking force decrease responsiveness slower than the driven wheel braking force decrease responsiveness at the start of a slope that releases the braking force of the front and rear wheels. Braking force control device. In the vehicle hill hold braking force control device according to claim 2,
Provide road surface gradient detection means for detecting the road surface gradient of the stopped slope,
A hill hold braking force control device for a vehicle according to claim 1, wherein the hill hold braking force control means increases both the driving wheel braking force decreasing response and the driven wheel braking force decreasing response as the road surface gradient increases. In the vehicle hill hold braking force control device according to claim 3,
The hill hold braking force control means increases the difference between the driving wheel braking force decrease response and the driven wheel braking force decrease response as the road surface gradient increases. apparatus. In the hill hold braking force control device for a vehicle according to any one of claims 1 to 4,
The motor traction control means detects angular acceleration of a drive wheel or a motor, and performs angular acceleration control for recovering a wheel grip by motor torque down control when the angular acceleration exceeds a set angular acceleration. Hill hold braking force control device.

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