JP2009190483A - Braking control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking control device of a vehicle allowing securing of stability of a turning behavior by early elimination of under-steering. <P>SOLUTION: In this braking control device having a regenerative braking force limiting means 5d, a vehicle wheel speed right and left difference detection means for detecting a vehicle speed difference between right and left wheels of the vehicle is provided, and the regenerative braking limiting means 5d changes limiting amount of regenerative braking force according to an under-steering tendency based on the vehicle speed right and left difference. The regenerative limiting control part 5d more limits regenerative braking torque when performing turning braking as the vehicle speed right and left difference becomes smaller and vehicle speed front and rear difference becomes larger. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to a technical field of a vehicle braking control device that executes regenerative cooperative brake control that distributes a friction braking force and a regenerative braking force.

Conventionally, in a vehicle in which front wheels are motor-driven, when understeer is detected during braking and turning, the stronger the understeer tendency, the smaller the front wheel regenerative braking torque and the larger the rear wheel friction braking torque. The braking force distribution is changed from the excessive distribution of the front wheel braking force to the braking force distribution according to the ideal distribution characteristic of the front and rear wheels to suppress the deterioration of turning performance (see, for example, Patent Document 1).
JP-A-5-161209

  However, in the above prior art, since the detection of understeer is estimated based on the steering angle and the yaw rate or lateral acceleration (hereinafter referred to as lateral G), the detection of understeer is delayed and the stability of the turning behavior is reduced. There was a problem that it could not be secured.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a vehicle braking control device capable of ensuring the stability of turning behavior by early elimination of understeer.

  In order to solve the above problems, in the vehicle braking control apparatus of the present invention, the limit amount of the regenerative braking force is changed according to the understeer tendency based on the wheel speed left-right difference.

  In the present invention, since the limit amount of the regenerative braking force is changed based on the difference between the left and right wheel speeds, the regenerative braking force can be limited without delay from the initial stage of occurrence of understeer to ensure the stability of the turning behavior.

  Hereinafter, the best mode for realizing a braking control device for a vehicle according to the present invention will be described based on Examples 1 to 3 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 hybrid vehicle by front wheel drive to which the braking control device of the first embodiment 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 (regenerative braking means) MG2, an output sprocket OS, and a power split mechanism TM. Have.

The engine E is a gasoline engine or a diesel engine, and the valve opening degree of the 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, and power control is performed based on a control command from a motor controller 2 described later. Each is independently controlled by applying a three-phase alternating current generated by the unit 3.

  Both motor generators MG1 and MG2 can operate as electric motors that are driven to rotate 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. In this case, the battery 4 can be charged by functioning as a generator that generates electromotive force at both ends of the stator coil (hereinafter, this operation 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. The sun gear S is connected to a first motor generator MG1. The ring gear R is connected to the second motor generator MG2 and the output sprocket OS. 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 (drive 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 set the interval between each rotating element to the collinear lever ratio (1: λ) based on the gear ratio λ of the sun gear S and ring gear R It arrange | positions so that it may become.

Next, the control system of the hybrid vehicle will be described.
As shown in FIG. 1, the control system of the hybrid vehicle in the first embodiment includes an engine controller 1, a motor controller 2, a power control unit 3, a battery 4 (secondary battery), 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. It is.

  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 master cylinder pressure sensor 17, and a brake stroke sensor 18. , Provides input information.

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

  The motor controller 2 operates the motor operation of the first motor generator MG1 in response to a target motor generator torque command from the integrated controller 6 that inputs the motor generator rotational speeds N1 and N2 from both the motor generator rotational speed sensors 10 and 11 by the resolver. A command for independently controlling the 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 motor controller 2 uses information on the battery S.O.C that indicates the state of charge of the battery 4.

  The power control unit 3 has a joint box, a step-up converter, a drive motor inverter, and a generator generator inverter that are not shown in the figure, and is a power source that can supply power to both motor generators MG1 and MG2 with less current with reduced loss. Configure the high-voltage system. A drive motor inverter is connected to the stator coil of second motor generator MG2, and a generator generator inverter is connected to the stator coil of first motor generator MG1. The joint box is connected to a battery 4 that is discharged during power running and charged during regeneration.

  The brake controller 5 performs ABS control by a control command to the brake fluid pressure unit 19 that independently controls the brake fluid pressure of the four wheels during low-μ road braking or sudden braking, If the regenerative braking torque is insufficient with respect to the required braking torque during a deceleration request operation such as a foot release operation, the control command to the integrated controller 6 and the brake hydraulic pressure unit 19 are supplemented so that the shortage is compensated by the friction braking torque. Regenerative cooperative brake control is performed by issuing a control command.

  The brake controller 5 receives wheel speed information from the wheel speed sensors 12, 13, 14, 15 and braking operation amount information from the master cylinder pressure sensor 17 and the brake stroke sensor 18. 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. The brake hydraulic unit 19 includes a front left wheel disc brake 20, a front right wheel disc brake 21, a rear left wheel disc brake 22, and a rear right wheel disc brake 23, which are not shown in the figure. Wheel cylinder is connected. Each of the disc brakes 20, 21, 22, 23 is a friction braking means that outputs a friction braking force.

  The integrated controller 6 manages the energy consumption of the entire vehicle and has the function of running the vehicle with the highest efficiency, and performs engine operating point control by a control command to the engine controller 1 during acceleration running, etc. Further, 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, drive torque performance will be described.
As shown in FIG. 2 (b), the driving torque of the hybrid vehicle of the first embodiment includes the engine direct driving torque (the driving torque obtained by subtracting the generator driving amount from the total engine driving torque) and the motor driving torque (both motor generators MG1). , Driving torque by the sum of MG2). As shown in FIG. 2 (a), the maximum driving torque is configured such that the motor driving torque occupies more as the vehicle speed becomes lower. In this way, since the vehicle does not have a transmission and travels by adding the direct drive torque of the engine E and the motor drive torque converted electrically, the full power of the accelerator pedal is fully opened from low speed to high speed from the state of low steady operation power. Until now, the drive torque can be controlled seamlessly with good response to the driver's request (torque on demand).

  In the hybrid vehicle of the first embodiment, the engine E, the motor generators MG1, MG2, and the left and right front tires are connected without a clutch through 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 torque of the vehicle changes suddenly due to tire slip or tire lock during braking, the power control unit 3 is protected from excessive current. Alternatively, it is necessary to protect parts from the pinion over-rotation of the power split mechanism TM. On the other hand, motor traction control that utilizes the high-output and high-response motor characteristics, developed from the component protection function, detects tire slip instantly, recovers its grip, and runs the vehicle safely. Is adopted.

Next, the braking torque performance will be described.
In the hybrid vehicle of the first embodiment, the second motor generator MG2 that is operating as a motor is operated as a generator during a deceleration requesting operation such as a brake depression operation or an accelerator release operation, whereby the kinetic energy of the vehicle is converted into electric energy. A regenerative braking system is adopted in which the battery 4 is collected and recovered in the battery 4 and reused.

  As shown in FIG. 3 (a), the general regenerative brake cooperative control in this regenerative brake system calculates the required braking torque for the brake pedal depression amount, regardless of the magnitude of the required braking torque. The required braking torque is shared by the regenerative component and the hydraulic component.

  On the other hand, the regenerative brake cooperative control employed in the hybrid vehicle of the first embodiment calculates the required braking torque with respect to the brake pedal depression amount as shown in FIG. 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 a vehicle mode in the hybrid vehicle of the first embodiment, as shown in the alignment chart of FIG. 4, “stop mode”, “start mode”, “engine start mode”, “steady travel mode”, and “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 “start mode”, as shown in FIG. 4B, the vehicle starts by driving only the motor MG2. In the “engine start mode”, as shown in FIG. 4 (c), the sun gear S rotates to start the engine E by the generator MG 1 having a function as an engine starter. In the “steady running mode”, as shown in FIG. 4 (d), the vehicle runs mainly with the engine E, and power generation is minimized in order to increase efficiency. In the “acceleration mode”, as shown in FIG. 4 (e), the rotational speed of the engine E is increased and power generation by the generator MG1 is started, and the driving torque of the motor MG2 is generated using the electric power and the electric power of the battery 4. In addition, it accelerates.

  In reverse running, in the “steady running mode” shown in FIG. 4 (d), 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 start, the engine E is started by turning the ignition key. When the engine E warms up, the engine E is stopped immediately. At the time of start-up or when the vehicle is lightly loaded down a gentle hill running at a very low speed, the fuel is cut in the region where the engine efficiency is low, and the engine E is stopped and the vehicle is driven by the motor MG2. During normal travel, the driving torque of the engine E is driven directly by the power split mechanism TM to the left and right front wheels, and the other drives the generator MG1 to assist the motor MG2. At the time of full open acceleration, power is supplied from the battery 4 and further driving torque is added. During the deceleration request operation, the left and right front wheels drive the motor MG2 and act 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 braking control apparatus of Example 1 will be described.
FIG. 5 is a control block diagram of the brake controller 5 of the first embodiment. The brake controller 5 includes a braking control unit (braking force control unit) 5a and a wheel speed front / rear difference detection unit (wheel speed front / rear detection unit) that is an understeer detection unit. A difference detection means) 5b, a wheel speed left / right difference detection section (wheel speed left / right difference detection means) 5c, and a regenerative braking restriction section (regenerative braking force restriction means) 5d.

The braking control unit 5a calculates the required braking torque based on the braking operation amount detected by the brake pedal stroke sensor 18, and when the required braking torque is sufficient only by the required regenerative torque, the braking control unit 5a obtains the required regenerative torque. A control command is output to the integrated controller 6. When the required regenerative torque is insufficient with respect to the required braking torque, a control command for obtaining the insufficient braking torque is output to the brake hydraulic pressure unit 19.
The wheel speed front / rear difference detecting unit 5b is based on the wheel speeds from the wheel speed sensors 12, 13, 14, and 15, and the average value of the front turning outer wheel speed and the rear left and right rear wheels (= estimated vehicle speed). The difference between the front and rear wheel speeds is calculated.
The wheel speed left / right difference detection unit 5 c calculates a wheel speed left / right difference which is a difference between the left front wheel speed from the front left wheel speed sensor 12 and the right front wheel speed from the front right wheel speed sensor 13.

The regenerative braking restriction unit 5d calculates a restriction amount to restrict the distribution ratio of the regenerative braking torque to the required braking torque at the time of regenerative braking based on the wheel speed front-rear difference and the wheel speed left-right difference.
When the limit amount is calculated, the brake control unit 5a sets the value obtained by subtracting the limit amount from the required regenerative torque as the final required regenerative torque (regenerative braking force limit control).

[Regenerative braking force limit control process]
FIG. 6 is a flowchart showing the flow of the regenerative braking force limit control process executed by the brake controller 5 of the first embodiment. Each step will be described below. This control process is repeatedly executed at a predetermined calculation cycle. However, when there is any control intervention of ABS control, TCS control, or VDC control (vehicle behavior stabilization control), these controls are terminated. It is interrupted until

  In step S1, the brake control unit 5a determines whether or not there is a deceleration request due to a brake depression operation or the like. If YES, the process proceeds to step S2, and if NO, the process proceeds to return.

  In step S2, the wheel speed longitudinal difference detection unit 5b calculates the wheel speed longitudinal difference from each wheel speed read in step S2, and the process proceeds to step S3. Here, the front-rear wheel speed difference is obtained from the difference between the front turning outer wheel speed and the average value of the left and right rear wheels (= estimated vehicle body speed). That is, in front-wheel drive-based vehicles, when braking and turning, the wheel load on the turning inner wheel decreases due to the centrifugal force acting on the vehicle, and when comparing the turning inner and outer wheels, the turning inner wheel enters the braking lock state before the turning outer wheel. Transition. Therefore, when the average value of the turning inner wheel speed and the regenerative braking wheel speed is used as the regenerative braking wheel speed used for the calculation of the wheel speed deviation, the understeer tendency is overestimated. Therefore, the understeer tendency can be accurately evaluated by using the difference between the average vehicle speed of the front wheel (regenerative braking wheel) and the rear wheel outside the turn.

  In step S3, the wheel speed left / right difference detector 5c calculates the wheel speed left / right difference from the wheel speeds of the left and right front wheels, and the process proceeds to step S4.

  In step S4, the regenerative braking restriction unit 5d refers to the regenerative restriction amount setting map of FIG. 7 based on the difference between the front and rear wheel speeds calculated in step S2 and the difference between the left and right wheel speeds calculated in step S3. The amount is calculated, and the process proceeds to step S5. In the regenerative restriction amount setting map of FIG. 7, the regenerative restriction amount is set to be larger as the wheel speed front-rear difference is larger and larger as the wheel speed left-right difference is smaller.

  In step S5, the braking control unit 5a subtracts the regeneration limit amount calculated in step S4 from the required regeneration torque set in advance according to the driver's braking operation amount (brake pedal operation amount), thereby obtaining the final regeneration. The braking torque is calculated, and the process proceeds to step S6.

  In step S6, the braking control unit 5a outputs a control command for obtaining the regenerative torque calculated in step S5 to the integrated controller 6. If the regenerative braking torque is insufficient with respect to the required braking torque, the shortage is friction-braking. A control command obtained by torque is output to the brake hydraulic pressure unit 19, and the process proceeds to return.

Next, the operation will be described.
[Vehicle behavior during turning braking]
For example, when regenerative braking is performed only on the left and right front wheels without restricting the regenerative braking force at the time of braking turning, the vehicle behavior tends to be understeered particularly during braking turning on a low μ road. This is due to the following reason.

  First, the braking force distribution between the front wheel braking force and the rear wheel braking force at the time of braking is the distribution of the braking force of a general vehicle (a vehicle that does not have a proportioning valve or an electronically controlled braking force distribution system EBD). As shown in FIG. 5, the braking force is distributed along a linear characteristic that approximates an ideal distribution line for maximizing the braking force. However, in hybrid vehicles, in order to make the braking force distribution ideal braking force distribution, it is necessary to operate a hydraulic friction brake on the left and right rear wheels that are not connected to the generator, and the regenerative component is deducted from the hydraulic component. Therefore, the amount of energy recovered is reduced, which is disadvantageous for improving fuel efficiency.

  Therefore, in the hybrid vehicle of the first embodiment, all of the braking force that can be provided by the regenerative portion with respect to the driver's required braking force is obtained by the regenerative portion, that is, the regenerative braking force is applied only to the front wheels. By doing so, we try to improve fuel efficiency as much as possible. In this case, the braking force distribution of the left and right rear wheels becomes zero, the rear wheel braking force for a general vehicle is added to the front wheel braking force, the front wheel braking force ratio increases, and the front wheel lock boundary line approaches.

  Therefore, when braking and turning, the front wheel braking force due to regenerative braking becomes excessive.For example, when approaching the front wheel lock boundary line, lateral force generation on the left and right front wheels is limited, and the vehicle is moved outward from the intended turning line by the front wheel turning angle. The understeer characteristic is shown with respect to the turning behavior along the line that swells, that is, the setting standard steer characteristic determined by the specifications of the vehicle. This understeer characteristic has a tendency to increase understeer as the front wheel braking force approaches the front wheel lock boundary line.

[Regeneration limit amount setting logic according to wheel speed difference]
On the other hand, in the braking control device according to the first embodiment, the regenerative restriction amount for limiting the regenerative braking force is increased as the wheel speed front-rear difference is larger and the wheel speed left-right difference is smaller. That is, in the flowchart of FIG. 6, in the flow from step S 1 → step S 2 → step S 3 → step S 4 → step S 5 → step S 6, the regeneration limit amount setting map is referred to in step S 4, and the required regeneration torque is determined in step S 5. The final regenerative torque is calculated by subtracting the regenerative limit amount.

  Here, the vehicle behavior estimation logic that the wheel speed deviation can be used to predict the understeer tendency will be described.

(Wheel speed difference before and after)
In the case of a vehicle based on a front wheel drive, the vehicle immediately before the occurrence of an understeer tendency at the time of braking turns has the left and right wheel speed deviation of the front wheel ≈ 0 (pumping) and the left and right wheel speed deviation of the rear wheel ≈ 0 (pumping) Yes, because the tire friction circle on the front wheel side is exhausted, the wheel speed decreases due to the braking lock, while the rear wheel speed follows the vehicle speed, and the wheel speed between the rear wheel speed and the front wheel speed. The deviation (wheel speed difference before and after) is large.

On the other hand, when the understeer tendency does not occur, the left and right wheel speed deviation of the front wheel is a constant value (wheel speed deviation due to the turning radius difference), and there is a margin in the friction circle of the tire on the front wheel side. The wheel speed deviation between the rear wheel speed following the vehicle body speed and the front wheel speed is small.
That is, the difference between the front and rear wheel speeds during turning braking is substantially equal to the magnitude of the understeer tendency, which is the degree of the understeer characteristic.

  In general, an understeer tendency is often determined based on a deviation between a target yaw rate of a vehicle and a generated yaw rate. However, when the yaw rate is used, understeer can be determined only after a remarkable understeer tendency appears in the yaw rate. That is, since it is difficult to predict the occurrence of understeer at the early stage of turning, there is a delay in limiting the regenerative braking force, and reliable turning behavior cannot be stabilized.

  On the other hand, in Example 1, the regenerative braking force can be limited at a stage before the understeer tendency becomes remarkable due to the difference in wheel speed before and after, and the stability of the turning behavior can be ensured. The wheel speed sensor has a higher sampling rate than the yaw rate sensor, and is advantageous in terms of control response.

(Wheel speed left / right difference)
In the braking control device of the first embodiment, in addition to the wheel speed front-rear difference, the limit amount of the regenerative braking force is increased as the wheel speed left-right difference is smaller.
When the vehicle turns, the center of gravity moves to the outside of the turn, and the wheel load of the wheel on the outside of the turn becomes larger than the wheel load of the wheel on the inside of the turn. For this reason, in a vehicle in which the braking force distribution of the front and rear wheels is set to a braking force distribution along a linear characteristic that approximates an ideal distribution line, as shown in FIG. 9, when turning right, a friction circle (friction circle) of the right wheel The friction circle on the left wheel is larger than Therefore, when turning, the right wheel reaches the limit of the tire generating force before the left wheel. The transition of each wheel speed at this time is shown in FIG.

  On the other hand, in a vehicle that prioritizes regenerative braking of the front wheels, as shown in FIG. 11, although the left side is weighted by turning right, the absolute braking force of the front wheels is greater than that of the rear wheels due to regenerative braking. Therefore, the front wheel reaches the limit of the tire generating force before the rear wheel. FIG. 12 is a diagram showing transition of each wheel speed at this time, and it can be seen that the wheel speed of the left front wheel decreases and converges to the wheel speed of the right front wheel before the wheel speed front-rear difference increases. .

  In other words, when turning, a wheel speed left / right difference occurs due to the difference in turning radius, but when an understeer tendency starts, the wheel speed left / right difference converges at an initial stage, and then the wheel speed front / back difference gradually increases. Yes.

  On the other hand, in the braking control apparatus of the first embodiment, the occurrence of understeer is predicted at the initial stage of turning based on the difference between the left and right wheel speeds during braking turning, and the regenerative braking force is more limited as the difference between the left and right wheel speeds is smaller. The regenerative braking force can be limited immediately before understeer occurs, and the stability of the turning behavior can be secured while suppressing the understeer tendency.

FIG. 13 is a time chart of the wheel speed, the wheel speed front-rear difference, and the wheel speed left-right difference showing the regenerative braking force limit control operation of the first embodiment.
For example, if the regenerative braking torque is limited only based on the difference between the front and rear wheel speeds, which is the estimated understeer amount, the regenerative braking torque is limited after the wheel speed front / rear difference reaches the threshold value for starting the regenerative restriction at time t2. Therefore, it takes time until the regenerative braking torque is limited after understeering occurs.

  In the first embodiment, the regenerative braking torque can be limited from time t1 before time t2 by limiting the regenerative braking torque based on the degree of convergence of the wheel speed left / right difference. In other words, by setting the regenerative limit amount based on the wheel speed left-right difference in addition to the wheel speed front-rear difference, it becomes possible to make the regeneration limit start threshold for the wheel speed front-rear difference shallower (smaller). It is possible to ensure the stability of the turning behavior by speeding up the intervention of the restriction.

Next, the effect will be described.
The vehicle braking control apparatus according to the first embodiment has the following effects.

  (1) The regenerative braking limiting unit 5d limits the regenerative braking force based on the wheel speed left / right difference and the wheel speed front / rear difference, and therefore limits the regenerative braking force without delay from the initial stage of the occurrence of understeer. Stability can be ensured.

  (2) The understeer detection means is a wheel speed front / rear difference detecting unit 5b that detects a wheel speed front / rear difference that is a wheel speed difference between the front and rear wheels, and the regenerative braking restriction unit 5d increases the regenerative restriction amount as the wheel speed front / rear difference increases. To make it larger. As a result, the understeer tendency can be suppressed at an earlier stage and the turning behavior state quantity such as a yaw rate sensor can be detected as compared with the case where the understeer quantity is estimated from the turning behavior state quantity (generated yaw rate, etc.) of the vehicle. Means can be omitted, which is advantageous in terms of cost.

  (3) The regenerative braking restriction unit 5d increases the regenerative restriction amount as the difference between the left and right wheel speeds becomes smaller. Therefore, the regenerative braking torque can be restricted immediately after the occurrence of understeer, thereby ensuring the stability of the turning behavior. be able to.

  In the second embodiment, the regenerative braking force set based on the difference between the front and rear wheel speeds based on the differential value of the difference between the theoretical difference between the left and right theoretical wheel speeds when turning and the actual difference between the left and right wheel speeds. This is an example of changing the limit amount. Since the entire system configuration is the same as that of the first embodiment, illustration and description are omitted.

  The regenerative braking limiting unit 5d of the second embodiment calculates a limiting amount for limiting the distribution ratio of the regenerative braking torque to the required braking torque at the time of regenerative braking based on the wheel speed longitudinal difference, and sets the limiting amount. The correction is made based on the sign of the differential value of the deviation between the theoretical wheel speed left / right difference during turning in the reference steering characteristic and the actual wheel speed left / right difference.

[Regenerative braking force limit control process]
FIG. 14 is a flowchart showing the flow of the regenerative braking force limit control process executed by the brake controller 5 of the second embodiment. Each step will be described below. In addition, the step which performs the same process as Example 1 attaches | subjects the same step number, and abbreviate | omits description.

  In step S11, the regenerative braking limiting unit 5d calculates a differential value of the deviation between the theoretical difference between the left and right theoretical wheel speeds when turning in the standard steering characteristics and the actual difference between the left and right wheel speeds calculated in step S3. Move to S12. Here, the theoretical difference between the left and right theoretical wheel speeds when turning in the standard steering characteristic can be obtained from the vehicle specifications according to the vehicle speed and the turning angle of the front wheels. For example, the driven wheels (left and right rear wheels) By adopting a method for estimating the turning angle from the wheel speed difference using a vehicle model or the like, a sensor for detecting the turning angle can be omitted.

  In step S12, the regenerative braking restriction unit 5d calculates the regenerative restriction amount with reference to the regenerative restriction amount setting map of FIG. 15 based on the wheel speed front-rear difference calculated in step S2, and proceeds to step S13. In the regeneration limit amount setting map of FIG. 15, the regeneration limit amount is set so as to increase as the wheel speed front-rear difference increases.

  In step S13, the regenerative braking restriction unit 5d determines whether or not the differential value calculated in step S11 is a negative value. If YES, the process proceeds to step S14. If NO, the process proceeds to step S15.

  In step S14, in the regenerative braking restriction unit 5d, a value obtained by reducing the regenerative restriction amount calculated in the previous calculation cycle at a predetermined ratio is set as the regenerative restriction amount, and the process proceeds to step S5. Here, the reduction rate of the regenerative restriction amount is a constant value, but may be changed according to the vehicle speed and the steering angle.

  In step S15, the regenerative braking restriction unit 5d determines whether or not the differential value calculated in step S11 is a positive value. If YES, the process proceeds to step S16, and if NO, the process proceeds to step S17.

  In step S16, the regenerative braking restriction unit 5d sets the regenerative restriction amount calculated in step S12 to the current regenerative restriction amount, and the process proceeds to step S5.

  In step S17, the regenerative braking limit unit 5d sets the regenerative limit amount calculated in the previous calculation cycle to the current regenerative limit amount, and proceeds to step S5.

Next, the operation will be described.
[Regeneration restriction logic according to the differential value of the deviation between the theoretical value of wheel speed front and back difference and the actual measurement value]
As described in the first embodiment, the understeer tendency at the time of braking and turning appears as convergence of the wheel speed left-right difference at the initial stage, and then becomes remarkable due to the increase in the wheel speed front-rear difference. That is, it is possible to predict which direction the understeering direction is directed by looking at the change direction of the wheel speed left-right difference.

Accordingly, in the second embodiment, the differential value of the theoretical wheel speed left / right difference during turning in the steering characteristic of the setting reference and the actual wheel speed left / right difference calculated from the detection values of the wheel speed sensors 12, 13, 14, and 15 is used. Based on this differential value, the regenerative limit amount set according to the difference between the front and rear of the wheel speed is changed to increase the sensitivity of the regenerative limit to the understeer tendency, ensuring the stability of turning behavior and improving the practical fuel consumption. To achieve both.
Hereinafter, a specific correction method for the regenerative restriction amount in accordance with the differential value will be described.

  (a) When the differential value is a positive value (in the case of FIG. 16 (a)), the required regenerative torque is limited using the regenerative restriction amount determined according to the wheel speed longitudinal difference. At this time, in the flowchart shown in FIG. 14, the flow proceeds from step S1 → step S2 → step S3 → step S11 → step S12 → step S13 → step S15 → step S16 → step S5 → step S6. The regenerative restriction amount corresponding to the wheel speed front-rear difference is set as the final regenerative restriction amount.

  If the differential value is a positive value, it can be determined that the difference between the wheel speed and the left / right wheel speed is converging, i.e., the direction in which the understeer tendency is increasing. By setting the regeneration limit amount accordingly, the understeer tendency can be suppressed earlier and the turning behavior can be stabilized.

  (b) If the differential value of the deviation is zero (in the case of FIG. 16 (b)), step S1, step S2, step S3, step S11, step S12, step S13, step S15, step S17, step S5 → Proceed to step S6. In step S17, the previous regeneration limit amount is maintained.

  When the differential value is zero, it can be determined that the wheel speed difference between the left and right wheels is constant, i.e., the understeer tendency does not fluctuate.In this case, the regenerative braking torque is excessively limited by maintaining the regenerative limit amount. Can be prevented, and the practical fuel consumption can be improved.

  (c) If the differential value of the deviation is negative (in the case of FIG. 16 (c)), step S1, step S2, step S3, step S11, step S12, step S13, step S14, step S5, step S5 The flow proceeds to step S6. In step S14, the regeneration limit amount is decreased from the previous value.

  If the differential value is a negative value, it can be determined that the difference between the wheel speed and the left / right wheel speed is increasing, i.e., the direction in which the understeer tendency is weakened. By reducing the corresponding regenerative restriction amount, regenerative braking can be recovered early and the practical fuel consumption can be improved.

Next, the effect will be described.
The vehicle braking control apparatus according to the second embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment.

  (4) The regenerative braking limiting unit 5d determines the regenerative limiting amount corresponding to the understeer tendency based on the differential value of the deviation between the theoretical wheel speed left / right difference during turning and the actual wheel speed left / right difference in the set standard steering characteristics. To change. Thereby, the sensitivity of the regenerative restriction with respect to the understeer tendency can be increased, and both the ensuring of the stability of the turning behavior and the improvement of the practical fuel consumption can be achieved.

  (5) When the differential value is a positive value, the regenerative braking limiting unit 5d sets the regenerative braking force limit amount to a value corresponding to the understeer amount estimated from the difference between the front and rear wheel speeds. Can be suppressed.

  (6) When the differential value is zero, the regenerative braking limiting unit 5d maintains the previous regenerative braking force limit, so that the regenerative braking torque can be prevented from being excessively limited, and the practical fuel consumption can be improved. Can be planned.

  (7) When the differential value is negative, the regenerative braking limit unit 5d reduces the regenerative braking force limit amount from the previous value. Therefore, when the understeer tendency converges, the regenerative braking limit unit 5d It is possible to improve the practical fuel consumption.

  The third embodiment is set based on the difference between the front and rear wheel speeds in accordance with the magnitude of the gradient of the difference between the theoretical difference between the left and right theoretical wheel speeds when turning and the actual difference between the left and right wheel speeds. This is an example of correcting the regenerative restriction amount. Since the entire system configuration is the same as that of the first embodiment, illustration and description are omitted.

  The regenerative braking restriction unit 5d of the third embodiment calculates a restriction amount for restricting the distribution ratio of the regenerative braking torque to the required braking torque at the time of regenerative braking based on the wheel speed longitudinal difference, and sets the restriction amount. The correction is made based on the magnitude of the differential value of the deviation between the theoretical difference between the left and right theoretical wheel speeds when turning in the standard steering characteristic.

[Regenerative braking force limit control process]
FIG. 17 is a flowchart showing the flow of the regenerative braking force limit control process executed by the brake controller 5 of the third embodiment. Each step will be described below. In addition, the same step number is attached | subjected to the step which performs the same process as Example 1 or Example 2, and description is abbreviate | omitted.

  In step S21, the regeneration limit amount calculated in step S12 is corrected according to the magnitude of the differential value, and the process proceeds to step S5. In this step, referring to the correction gain setting map of FIG. 18, the correction gain is calculated from the differential value calculated in step S11, and the calculated correction gain is multiplied by the regeneration limit amount calculated in step S12. In FIG. 18, the correction gain is set such that the larger the absolute value of the differential value, that is, the smaller the differential value, the smaller the value (<1).

  In step S22, the regeneration limit amount calculated in step S12 is corrected according to the magnitude of the differential value, and the process proceeds to step S5. In this step, referring to the correction gain setting map of FIG. 19, the correction gain is calculated from the differential value calculated in step S11, and the calculated correction gain is multiplied by the regeneration limit amount calculated in step S12. In FIG. 19, the correction gain is set to be a larger value (> 1) as the differential value is larger.

Next, the operation will be described.
In the third embodiment, the differential value of the deviation between the theoretical wheel speed left / right difference during turning and the actual wheel speed left / right difference in the steering characteristics of the setting reference is calculated, and the wheel speed longitudinal difference is calculated based on the sign of this differential value. In order to change the regenerative restriction amount according to the same as in Example 2, it is possible to increase the sensitivity of the regenerative restriction with respect to the understeer tendency, and to ensure both the stability of the turning behavior and the improvement of the practical fuel consumption.

  Furthermore, in Example 3, when the differential value is a positive value, the regeneration limit amount is increased as the differential value increases. At this time, in the flowchart of FIG. 17, the flow proceeds from step S1 → step S2 → step S3 → step S11 → step S12 → step S13 → step S15 → step S22 → step S5 → step S6. The larger the value, the larger the correction gain, and the regeneration limit amount is corrected to a larger value.

  In other words, since the positive differential value represents an increasing gradient of the understeer tendency, it is possible to predict how much the understeer tendency will increase by looking at the magnitude of the differential value. Therefore, by correcting the regenerative limit amount based on the difference between the front and rear wheel speeds according to the degree to which the understeer tendency increases, it becomes possible to limit the regenerative braking torque that pre-reads the increase in understeer, and to ensure the stability of the turning behavior. it can.

  When the differential value is a negative value, the regenerative braking amount is made smaller as the differential value is smaller (the absolute value of the differential value is larger). At this time, the flow proceeds from step S1 → step S2 → step S3 → step S11 → step S12 → step S13 → step S21 → step S5 → step S6. In step S21, the correction gain increases as the absolute value of the differential value increases. Decrease and correct the regeneration limit to a smaller value.

  In other words, since the negative differential value represents a decreasing gradient of the understeer tendency, it can be predicted how much the understeer tendency is weakened by looking at the magnitude of the differential value. Therefore, by correcting the amount of regenerative braking based on the difference between the front and rear wheel speeds according to the degree to which understeer weakens, it becomes possible to limit the regenerative braking torque that pre-reads the decrease in the understeer tendency and prevents excessive regenerative braking torque limitation. Therefore, it is possible to improve the practical fuel consumption.

Next, the effect will be described.
The vehicle braking control apparatus according to the third embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment and the effects (4) to (7) of the second embodiment.

  (8) The regenerative braking limiting unit 5d determines that the differential value of the deviation between the theoretical difference between the left and right theoretical wheel speeds when turning and the detected difference between the left and right wheel speeds is a positive value. Since the limit amount of the regenerative braking force becomes larger as the value increases, it becomes possible to limit the regenerative braking torque that prefetches the increase in understeer, and the stability of the turning behavior can be ensured.

  (9) When the differential value of the deviation between the theoretical difference between the left and right theoretical wheel speeds when turning and the detected difference between the left and right wheel speeds is a negative value, the regenerative braking limit unit 5d The smaller the amount, the smaller the regenerative braking force limit, so it is possible to limit the regenerative braking torque that pre-reads the decrease in the understeer tendency, and it is possible to prevent excessive regenerative braking torque limitation and improve the practical fuel consumption. .

(Other examples)
As mentioned above, although the braking control apparatus of the vehicle of this invention has been demonstrated based on Examples 1-3, it is not restricted to these Examples about a concrete structure, Each claim of a claim Design changes and additions are allowed without departing from the gist of the invention.

  Example 2 and Example 3 may be combined. For example, when the differential value of the deviation between the theoretical difference between the left and right theoretical wheel speeds when turning in the steering characteristic of the setting reference and the detected difference between the left and right wheel speeds is a positive value, as in the third embodiment, If the regenerative restriction amount is corrected according to the magnitude and the differential value is a negative value, the regenerative restriction amount may be reduced at a constant rate as in the second embodiment.

1 is an overall system diagram showing a front wheel drive hybrid vehicle to which a braking control device of Embodiment 1 is applied. FIG. 3 is a drive torque performance characteristic diagram and a drive torque conceptual diagram in a front-wheel drive hybrid vehicle to which the braking control device of Embodiment 1 is applied. It is a contrast characteristic figure showing the braking torque performance by regeneration cooperation in the front-wheel drive hybrid vehicle to which the braking control device of Example 1 was applied. It is a collinear diagram which shows each vehicle mode in the front-wheel drive hybrid vehicle to which the braking control apparatus of Example 1 was applied. FIG. 3 is a control block diagram of the brake controller 5 according to the first embodiment. 6 is a flowchart showing a flow of regenerative braking force limit control processing executed by the brake controller 5 of the first embodiment. 3 is a regeneration restriction amount setting map according to the first embodiment. It is a braking force distribution characteristic diagram showing the braking force distribution at the time of regenerative cooperation. It is a figure which shows the change of the friction circle of each wheel at the time of the right turn in the vehicle made into braking force distribution along the linear characteristic which approximates the braking force distribution of a front-and-rear wheel to an ideal distribution line. It is a time chart which shows the wheel speed change of each wheel at the time of the right turn in the vehicle which made the braking force distribution of front and rear wheels the braking force distribution along the linear characteristic approximating the ideal distribution line. It is a figure which shows the change of the friction circle of each wheel at the time of the right turn in the vehicle which gives priority to regenerative braking. It is a time chart which shows the wheel speed change of each wheel at the time of the right turn in the vehicle which gives priority to regenerative braking. 4 is a time chart of wheel speed, wheel speed front-rear difference and wheel speed left-right difference showing the regenerative braking force limit control operation of the first embodiment. It is a flowchart which shows the flow of the regenerative braking force restriction | limiting control process performed with the brake controller 5 of Example 2. FIG. 10 is a regenerative restriction amount setting map according to the second embodiment. 6 is a time chart of a deviation between a theoretical wheel speed left / right difference during turning and an actual wheel speed left / right difference in a setting reference steering characteristic indicating a regenerative braking force limiting control operation according to a second embodiment; It is a flowchart which shows the flow of the regenerative braking force restriction | limiting control process performed with the brake controller 5 of Example 3. FIG. It is a correction gain setting map in case the differential value of Example 3 is a negative value. It is a correction gain setting map in case the differential value of Example 3 is a positive value.

Explanation of symbols

E engine
MG1 1st motor generator
MG2 Second motor generator (regenerative braking means)
MG3 3rd motor generator
OS output sprocket
TM Power split mechanism 1 Engine controller 2 Motor controller 3 Power control unit 4 Battery 5 Brake controller 5a Braking controller (braking force control means)
5b Wheel speed longitudinal difference detector (wheel speed longitudinal difference detector)
5c Wheel speed left / right difference detection unit (wheel speed left / right difference detection means)
5d regenerative braking limiting unit (regenerative braking force limiting means)
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 17 Master cylinder pressure sensor 18 Brake stroke sensor 19 Brake fluid pressure unit 20 Front left wheel disc brake (friction braking means)
21 Front right wheel disc brake (friction braking means)
22 Rear left wheel disc brake (friction braking means)
23 Rear right wheel disc brake (friction braking means)

Claims (9)

Regenerative braking means provided on the left and right front wheels and outputting regenerative braking force;
Friction braking means provided on each of the front and rear wheels and outputting friction braking force;
Braking force control means for executing regenerative cooperative brake control for allocating the friction braking force and the regenerative braking force based on a driver's required braking force;
An understeer detecting means for detecting an understeer tendency that is a degree of an understeer characteristic with respect to a vehicle setting reference steer characteristic;
Regenerative braking force limiting means for limiting the regenerative braking force to be smaller as the understeer tendency is higher;
In a braking control device for a vehicle having
A wheel speed left / right difference detecting means for detecting a wheel speed left / right difference which is a wheel speed difference between the left and right wheels;
The regenerative braking force limiting means changes the limiting amount of the regenerative braking force in accordance with the understeer tendency based on the wheel speed left / right difference. The vehicle braking control device according to claim 1,
The understeer detection means is a wheel speed front / rear difference detection means for detecting a wheel speed front / rear difference which is a wheel speed difference between the front and rear wheels,
The regenerative braking force limiting means limits the regenerative braking force to a smaller value as the wheel speed front-rear difference is larger. In the vehicle braking control device according to claim 1 or 2,
The regenerative braking force limiting means limits the regenerative braking force to a smaller value as the difference between the left and right wheel speeds is smaller. In the vehicle braking control device according to claim 1 or 2,
The regenerative braking force limiting means is based on the differential value of the deviation between the theoretical wheel speed left / right difference during turning in the steering characteristic of the setting reference and the detected wheel speed left / right difference according to the understeer tendency. A braking control apparatus for a vehicle, characterized in that a limit amount of the regenerative braking force is changed. The vehicle braking control device according to claim 4,
The regenerative braking force limiting means, when the differential value is a positive value, sets the limiting amount of the regenerative braking force as the limiting amount of the regenerative braking force according to the understeer tendency. Control device. In the vehicle brake control device according to claim 4 or 5,
The vehicle regenerative braking force limiting means maintains the previous regenerative braking force limit when the differential value is zero. The vehicle braking control device according to any one of claims 4 to 6,
The regenerative braking force limiting means reduces the limiting amount from the previous limiting amount of the regenerative braking force when the differential value is a negative value. In the vehicle braking control device according to claim 1 or 2,
The regenerative braking force limiting means corrects the regenerative braking force limit amount according to the understeer tendency to a larger value as the differential value is larger when the differential value is a positive value. Braking control device. In the braking control device for a vehicle according to claim 1, 2 or 8,
The regenerative braking force limiting means, when the differential value is a negative value, corrects the regenerative braking force limit amount according to the understeer tendency to a smaller value as the differential value is smaller. Braking control device.

Images