JP2006205787A - Regenerative braking control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a regenerative braking control device of a vehicle capable of preventing hunting of a regeneration amount setting mode and stably controlling the braking regeneration amount in such a status that a road μ estimated according to wheel speed information rapidly changes. <P>SOLUTION: This regenerative braking control device of a vehicle comprises a road μ estimation means estimating the road μ based on the vehicle wheel speed information, and a regenerative braking control means controlling a regenerative braking amount according to the estimated road μ. The regenerative braking control means maintains the regenerative braking amount immediately before the road μ rapidly changes when a status in which the estimated road μ rapidly changes is detected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a regenerative braking control device for a vehicle (such as a hybrid vehicle or an electric vehicle) that performs regenerative braking control that estimates road surface μ based on wheel speed information and controls a regenerative braking amount according to the estimated road surface μ.

Conventionally, in a vehicle including a driving wheel that can be braked by hydraulic pressure and regeneration and a driven wheel that can be braked by hydraulic pressure, the braking force setting mode has three stages (regeneration priority mode, normal mode, emergency mode), A technique for preventing a sudden change in braking force by smoothly switching between the regeneration priority mode and the normal mode is known. Note that the mode switching control is performed based on the estimated road surface μ (see, for example, Patent Document 1).
JP-A-5-161209

  However, in the above-described conventional regenerative braking control device, when the mode is set based on the estimated road surface μ, for example, the wheel floats when the wheel jumps (= the vehicle jumps) as when traveling on a rough road. When the vehicle is idling, that is, when the road surface μ estimated by the wheel speed information is extremely low μ, hunting occurs between the regeneration priority mode and the normal mode by repeatedly jumping and landing on the wheels. It is obvious to do. As a result, there is a problem that the usability of the driver is lowered.

  The present invention has been made paying attention to the above-mentioned problem, and prevents the occurrence of hunting in the regeneration amount setting mode in a situation where the road surface μ estimated by the wheel speed information changes suddenly, and stable braking regeneration amount control. An object of the present invention is to provide a regenerative braking control device for a vehicle that can achieve the above.

In order to achieve the above object, in the regenerative braking control device for a vehicle in the present invention,
Road surface μ estimation means for estimating the road surface μ based on wheel speed information;
Regenerative braking control means for controlling the amount of regenerative braking according to the estimated road surface μ;
In a vehicle regenerative braking control device comprising:
The regenerative braking control means maintains the regenerative braking amount immediately before the road surface μ changes suddenly when detecting a situation where the estimated road surface μ changes suddenly.

  Therefore, in the regenerative braking control device for a vehicle according to the present invention, when the regenerative braking control means detects a situation where the estimated road surface μ changes suddenly, the regenerative braking amount immediately before the road surface μ changes suddenly is maintained. For example, even when the road surface μ estimated by the wheel speed information changes suddenly when the wheel repeats jumping and landing as when traveling on bad roads, it is set by the estimated road surface μ in the regenerative braking control means. The regenerative amount setting mode is maintained as it is in the mode set immediately before the estimated road surface μ suddenly changes. As a result, in a situation where the road surface μ estimated by the wheel speed information changes suddenly, it is possible to prevent the occurrence of hunting in the regeneration amount setting mode and achieve stable braking regeneration amount control.

  Hereinafter, the best mode for realizing a regenerative braking 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 regenerative braking 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, an output sprocket OS, and a power split mechanism TM.

  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 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. 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 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 hybrid vehicle control system in the first embodiment includes an engine controller 1, a motor controller 2, a power control unit 3, a battery 4, and a brake controller 5 (mechanical braking force control means). And an integrated controller 6. Note that an auxiliary battery is connected to the battery 4 (high power battery) via a DC / DC converter (not shown) that uses the battery 4 as a power source, and this auxiliary battery is used as an operating power source for each of the controllers 1, 2, 5, and 6. And

  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.

  The brake controller 5 includes a front left wheel speed sensor 12 (wheel speed detection means), a front right wheel speed sensor 13 (wheel speed detection means), a rear left wheel speed sensor 14 (wheel speed detection means), and a rear Input information is provided from the right wheel speed sensor 15 (wheel speed detection means), the steering angle sensor 16, the master cylinder pressure sensor 17, and the brake stroke sensor 18.

  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 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, not shown, and can supply power to both motor generators MG1 and MG2 with less current with reduced loss. Configure the power supply system high voltage system. A drive motor inverter is connected to the stator coil of the second motor generator MG2, and a generator generator inverter is connected to the stator coil of the 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 hydraulic pressure unit 19 that independently controls the brake hydraulic pressure of the four wheels during low-μ road braking, sudden braking, etc. At the time of a deceleration request operation by an accelerator release operation or the like, regenerative cooperative brake control is performed by issuing a control command to the integrated controller 6 and a control command to the brake hydraulic pressure unit 19. 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 brake fluid pressure unit 19 and the wheel cylinders 20, 21, 22, and 23 correspond to mechanical braking means.

  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, 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 in 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 force of the vehicle changes suddenly due to tire slip or tire locking 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 force 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 the deceleration request 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 recovered 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 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. 4B, the motor MG2 is driven to start. 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 power of the motor MG2 is increased 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 force of the engine E is driven directly by the power split mechanism TM to the left and right front wheels, 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. 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 operation will be described.
[Road surface μ estimation processing]
FIG. 5 is a flowchart showing the flow of the road surface μ estimation process executed by the integrated controller 6 of the first embodiment. Each step will be described below (road surface μ estimation means).

In step S1, it is determined whether the vehicle is traveling. If YES, the process proceeds to step S2. If NO, the determination in step S1 is repeated.
Here, “running determination” indicates, for example, a travel range such as a D range signal, an R range signal, or the like (other than the P and N ranges) when a signal from an unillustrated inhibitor switch that detects the selection position of the select lever. If it is a signal, it is determined that the vehicle is traveling.

  In step S2, following the determination that the vehicle is traveling in step S1, the wheel speed information from each wheel speed sensor 12, 13, 14, 15 is monitored, and the process proceeds to step S3.

In step S3, following the wheel speed monitor in step S2, the road surface μ is estimated based on the drive torque command values for the engine E and the motor generators MG1 and MG2 and the wheel speed information, and the process proceeds to step S4. .
Here, “estimation of the road surface μ” is obtained by obtaining wheel speed detection values (for example, driving wheel speed average values) from the wheel speed sensors 12 and 13 of the left and right front wheels, which are driving wheels, and is estimated from a driving torque command value. When the difference between the vehicle speed and the vehicle speed is small, it is estimated that the road is a high μ road, and when the difference is large, the road is a low μ road. That is, on the high μ road where the occurrence of driving slip is small, the vehicle speed estimated by the driving torque and the wheel speed are almost the same, whereas on the low μ road where the occurrence of driving slip is large, the speed is estimated based on the driving torque. This is because the wheel speed increases as the vehicle speed decreases.

In step S4, following the estimation of the road surface μ in step S3, the degree of change of each wheel speed sensor 12, 13, 14, 15 is stored on a pre-stored “wheel jump determination map (FIG. 6)”. With reference to it, it is determined whether or not the wheel speed is suddenly changed (wheel jump). If YES, the process proceeds to step S5. If NO, the process returns to step S1.
Here, as shown in FIG. 6, the “wheel jump determination map” is given by a two-dimensional map based on the estimated vehicle speed estimated from the drive torque command value and the detected wheel speed value, and a wheel jump determination area is displayed on this two-dimensional map. A and B are set. Then, when the operating point specified by the estimated vehicle speed and the detected wheel speed value of each wheel exists in at least one of the wheel jump determination areas A and B, the wheel speed is suddenly changed (= wheel jump). Is determined.
That is, in the case of a front-wheel drive vehicle in which regenerative braking is applied only to the front wheels as in the first embodiment, during regenerative braking, the wheel speed detection value of the rear wheels rapidly increases and the wheel jump determination occurs when the front wheels are grounded and the rear wheels are floating. It is determined that the wheel jump is in the state of the area A. Further, when the rear wheel is grounded and the front wheel is floating, the wheel speed detection value of the front wheel is suddenly decreased and it is determined that the wheel jump is in the state of the wheel jump determination area B. Further, in the state where the four wheels are floating, the wheel speed detection value of the rear wheel is rapidly increased and is in the area of the wheel jump determination area A, and the wheel speed detection value of the front wheel is rapidly decreased and the area of the wheel jump determination area B is It is determined that there is a wheel jump in the state of

  In step S5, following the determination of the wheel jump in step S4, the estimation of the road surface μ is interrupted, the estimated road surface μ is fixed to the value of the estimated road surface μ immediately before the wheel jump determination, and the process proceeds to step S6. By fixing the estimated road surface μ, as a result, the regenerative braking control is also maintained in the control immediately before the wheel jump determination.

  In step S6, following the estimation suspension of the road surface μ and the fixation of the estimated road surface μ in step S5, the degree of change of each wheel speed sensor 12, 13, 14, 15 is stored in advance as a “wheel jump determination map ( As shown in FIG. 6), it is determined whether each wheel speed detection value has returned from a sudden decrease or sudden increase and deviated from the wheel jump determination areas A and B. If YES, the process proceeds to step S7. In this case, the determination in step S6 is repeated.

In step S7, following the determination that each wheel speed detection value has deviated from the wheel jump determination areas A and B in step S6, the estimation of the road surface μ is resumed with reference to the estimated road surface μ fixed in step S5. The process proceeds to step S8.
Here, in the “estimated resumption of road surface μ”, in the estimation resumption start area, the value of the fixed estimated road surface μ just before the wheel jump determination and the value of the road surface μ newly estimated by the vehicle body speed and the wheel speed are Thus, the estimated road surface μ value can be smoothly changed by a method of taking the interpolation value.

  In step S8, following the resumption of the estimation of the road surface μ in step S7, it is determined whether or not to shift to the vehicle system end flow. If YES, the flow ends. If NO, the flow returns to step S1. . That is, when the driver shuts down the vehicle system (for example, detects an ignition OFF signal), this control is terminated, and if the system activation is continued, the process is fed back to step S1.

  When the road surface μ is estimated in the flowchart in FIG. 5, the regenerative braking amount is controlled according to the regenerative-hydraulic braking amount distribution map for the estimated road surface μ shown in FIG. That is, the regenerative-hydraulic braking amount distribution map for the estimated road surface μ gives the regenerative braking amount only to the front wheels in the high μ region where the estimated road surface μ is equal to or less than the first set road surface μ (= μ1), and the estimated road surface μ is the first. In the region from the set road surface μ (= μ1) to the second set road surface μ (= μ2), the lower the μ, the more restrictive the regenerative braking amount of the front wheels, and the rear wheel hydraulic braking force depending on the limit amount. In the low μ region where the estimated road surface μ is greater than or equal to the second set road surface μ (= μ2), the maximum limit of the regenerative braking amount is the ideal distribution of the braking force distribution ratio of the front and rear wheels by the regenerative braking force and hydraulic braking force. Regenerative cooperative control is performed so as to provide a ratio (regenerative braking control means).

[Road surface μ estimation effect on dry road surface]
When traveling on a dry road surface with a high road surface μ and no irregularities, the flow proceeds from step S1 to step S2 to step S3 to step S4 in the flowchart of FIG. 5, where the wheel speed is suddenly changed (wheel jump). Is not determined, the flow of step S1, step S2, step S3, and step S4 is repeated.

  For example, the behavior on the dry road surface (μ≈1) will be described with reference to the time chart shown in the upper part of FIG. When the change characteristic of the estimated vehicle speed estimated from the torque command value of the drive source is the characteristic shown from time t1 to time t7 where acceleration, deceleration, acceleration, and deceleration are repeated, the change characteristic of the detected wheel speed is from time t1. Since there is no drive wheel slip until slightly before time t2, the characteristic follows the estimated vehicle speed characteristic. Since a little drive wheel slip occurs slightly before the time t2 until approximately the middle time between the time t4 and the time t5, the characteristic follows a little higher speed than the estimated vehicle speed characteristic. Further, since there is no driving wheel slip from the substantially intermediate point between time t4 and time t5 to time t7, the characteristic follows the estimated vehicle speed characteristic.

  Therefore, the road surface μ estimated from the estimated vehicle speed and the detected wheel speed is estimated road surface μ = 1 from time t1 to a little before time t2, and from a little before time t2 to an almost intermediate point between time t4 and time t5. The estimated road surface μ is a value slightly smaller than 1, and the estimated road surface μ = 1 from approximately the midpoint between time t4 and time t5 to time t7.

  Therefore, when a deceleration request operation is performed while traveling on a dry road surface, as shown in FIG. 7, the estimated road surface μ becomes a high μ region equal to or less than the first set road surface μ (= μ1), and the required braking force is reduced. Regenerative braking with 100% front wheel regeneration that gives the regenerative braking amount only to the left and right wheels, that is, regenerative braking priority control. Thereby, especially in a traveling pattern in which acceleration / deceleration is repeated, energy recovery efficiency is high, and energy recovery by regenerative braking can be realized up to a lower vehicle speed.

[Road surface μ estimation effect on low μ road surface]
When a wheel jump occurs while traveling on a low μ road surface, in the flowchart of FIG. 5, the flow proceeds from step S1, step S2, step S3, step S4, and step S5. In step S5, the wheel jump in step S4 is performed. Based on the determination, the estimation of the road surface μ is interrupted, and the estimated road surface μ is fixed to the value of the estimated road surface μ immediately before the wheel jump determination. In addition, while the wheel speed rapid change (wheel jump) continues, the process proceeds from step S5 to step S6, and the deviation determination from the wheel jump in step S6 is repeated. And if it deviates from a wheel speed sudden change (wheel jump), it will progress to step S7 from step S6, and estimation of road surface μ will be restarted with reference to the said fixed estimated road surface μ in step S7.

  For example, the behavior on a low μ road surface (μ≈0) will be described with reference to a time chart shown at the bottom of FIG. When the change characteristic of the estimated vehicle speed estimated from the torque command value of the drive source is the characteristic shown from time t1 to time t7 where acceleration, deceleration, acceleration, and deceleration are repeated, the change characteristic of the detected wheel speed is from time t1. Until time t2, there is no drive wheel slip, so the characteristic follows the estimated vehicle speed characteristic. From time t2 to time t3, the detected wheel speed protrudes and increases due to the occurrence of driving slip. From time t3 to time t4, there is a characteristic that the driving slip is gradually increased and the estimated vehicle speed characteristic moves away from the high speed side. From time t4 to time t5, there is a characteristic in which the occurrence of driving slip shifts from increasing to decreasing, so that the estimated vehicle speed characteristic approaches the estimated vehicle speed characteristic after moving away from the estimated vehicle speed characteristic to the high speed side. From time t5 to time t6, the detected wheel speed protrudes and increases due to the occurrence of drive slip. From time t6 to time t7, since there is no drive wheel slip, the characteristic follows the estimated vehicle speed characteristic.

  Therefore, the road surface μ estimated from the estimated vehicle speed and the detected wheel speed is estimated road surface μ = 1 from time t1 to time t2, and is estimated road surface μ≈0 from time t2 to time t3, but in step S5. Since the estimation of the road surface μ is interrupted and fixed to the value of the estimated road surface μ immediately before the wheel jump determination, the estimated road surface μ = 1 is maintained as the value of the control applied road surface μ. From time t3 to time t5, the estimated road surface μ changes with a value smaller than 1 along with the change in the detected wheel speed. From time t5 to time t6, the estimated road surface μ≈0, but in step S5, the estimation of the road surface μ is interrupted and fixed to the value of the estimated road surface μ immediately before the wheel jump determination, so that the control applied road surface μ As a value, estimated road surface μ = about 0.7 is maintained. Further, from time t6 to time t7, the estimated road surface μ = 1 immediately, but by referring to the fixed estimated road surface μ = 0.7, the control application road surface μ gradually increases from about 0.7 immediately after time t6. Converge to 1.

  For this reason, when a deceleration request operation is performed while traveling on a low μ road surface, the control applied road surface μ with reduced fluctuation is applied to the regenerative control with respect to the estimated road surface μ with large fluctuation calculated based on the detected wheel speed. Thus, it is possible to prevent hunting in which the regeneration priority mode of the front wheel regeneration 100% and the regeneration normal mode by ideal distribution are alternately repeated when the estimated road surface μ having a large variation is applied to the regeneration control. This is true not only during traveling on the low μ road surface, but also when traveling on rough roads with irregularities that cause wheel jumps, for example. In addition, sudden changes in the regeneration mode can be prevented even under conditions in which the road surface μ changes suddenly, such as when the road suddenly enters a low μ road from a high μ road.

  Further, as in the first embodiment, if the front wheel drive vehicle jumps during the regenerative running, only the front wheels may be locked and the behavior at the time of landing may be disturbed. Based on the assumption that μ is in the low μ range (see FIG. 7), when the braking force distribution is set to the ideal distribution state, the braking force ideal distribution state is maintained during the wheel jump determination. The stability of the vehicle behavior can be ensured.

Next, the effect will be described.
In the regenerative braking control device for a vehicle according to the first embodiment, the following effects can be obtained.

  (1) In a regenerative braking control device for a vehicle, comprising: a road surface μ estimating unit that estimates a road surface μ based on wheel speed information; and a regenerative braking control unit that controls a regenerative braking amount according to the estimated road surface μ. When the regenerative braking control means detects the situation where the estimated road surface μ changes suddenly, the regenerative braking control means sets the regenerative amount in a situation where the road surface μ estimated by the wheel speed information changes suddenly in order to maintain the regenerative braking amount immediately before the road surface μ changes suddenly. Mode hunting can be prevented from occurring, and stable braking regeneration amount control can be achieved.

  (2) The road surface μ estimation means includes a detection value from the wheel speed sensors 12, 13, 14, and 15 and a vehicle body speed estimated from a driving torque of a power source by the engine E and the motor generators MG1 and MG2. As the difference is larger, it is estimated that the road is a low μ road (step S3). Therefore, it is possible to easily estimate the road surface μ without adding a new sensor for estimating the road surface μ.

  (3) Wheel jump determination means (step S4) for determining wheel jump is provided, and when the road surface μ estimation means determines the wheel jump, the road surface μ estimation is interrupted, and the estimated road surface μ immediately before the wheel jump determination is obtained. Since it is fixed (step S5), during the wheel jump determination, it is possible to maintain the regenerative braking amount immediately before the road surface μ changes suddenly by fixing the estimated road surface μ.

  (4) After fixing the estimated road surface μ based on the determination of wheel jump, the road surface μ estimating means refers to the fixed road surface μ when the detected wheel speed deviates from the wheel jump determination area (step S6). Therefore, when the vehicle jumps from the wheel jump situation, it is possible to return to the regenerative braking control based on the estimation of the road surface μ with good response.

  (5) The vehicle performs regenerative braking only on the left and right wheels of the front wheel based on a deceleration request operation. The vehicle is provided with wheel speed sensors 12, 13, 14, and 15 for detecting wheel speed, and the wheel jump determination means ( Step S4) determines that the wheel jumps when at least one of the wheel speed rapid decrease of the regenerative braking wheel and the wheel speed rapid increase of the non-regenerative braking wheel is satisfied, so that the wheel speed information is not used without using an additional sensor. The wheel jump can be determined only by the above.

  (6) The regenerative braking control means (FIG. 7) is provided with a brake fluid pressure unit 19 and rear wheel wheel cylinders 22 and 23 that generate hydraulic braking force on the left and right rear wheels that do not perform regenerative braking among the front and rear wheels. In the high μ region where the estimated road surface μ is equal to or less than the first set road surface μ (= μ1), the regenerative braking amount is given only to the front wheels, and the estimated road surface μ is changed from the first set road surface μ (= μ1) to the second set road surface μ. In the region up to (= μ2), the lower the μ, the more the front wheel regenerative braking amount is limited, and the rear wheel hydraulic braking force is increased according to the limiting amount, so that the estimated road surface μ becomes the second set road surface μ ( = In the low μ region, which is equal to or greater than μ2), the regenerative cooperative control is performed so that the maximum restriction amount of the regenerative braking amount is defined so that the front-rear wheel braking force distribution ratio by the regenerative braking force and the hydraulic braking force becomes the ideal distribution ratio. In the region where the estimated road surface μ is high, the regeneration priority mode can improve fuel efficiency. When the constant road surface μ is in the low μ region, it is possible to ensure the vehicle's behavior stability by ideally distributing the braking force, and in the intermediate road surface μ region where the estimated road surface μ is from μ1 to μ2, the sudden change of the control mode is suppressed and low. The more you move to the μ side, the more stable the vehicle can be.

  As described above, the regenerative braking control device for a vehicle according to the present invention has been described based on the first embodiment. However, the specific configuration is not limited to the first embodiment, and the claims relate to each claim. Design changes and additions are allowed without departing from the scope of the invention.

  In the first embodiment, an example of application to a front wheel drive-based vehicle (FF vehicle) is shown. However, the regenerative braking control device of the present invention can also be applied to a rear wheel drive-based vehicle (for example, an FR vehicle). However, it can also be applied to a four-wheel drive vehicle that performs regenerative braking on the front and rear wheels.

  In the first embodiment, as the regenerative braking control means, when a situation in which the estimated road surface μ changes suddenly is detected, the estimation of the road surface μ is interrupted, and the estimated road surface μ is fixed, so that the regenerative braking amount immediately before the road surface μ suddenly changes is obtained. Although an example of maintaining is shown, if a situation in which the estimated road surface μ changes suddenly is detected, an example in which the regeneration mode immediately before the road surface μ suddenly changes is continued as it is while maintaining the estimation of the road surface μ may be used.

  In Example 1, as an example of the regeneration mode for the estimated road surface μ, as shown in FIG. 7, an example in which the regenerative 100% mode to the ideal distribution mode are changed in a stepless manner according to the size of the estimated road surface μ is shown. For example, the 100% regeneration mode and the ideal distribution mode may be switched in two stages with a predetermined estimated road surface μ as a boundary, and the size of the estimated road surface μ from the 100% regeneration mode to the ideal distribution mode is also possible. It may be switched to a plurality of stages according to the above.

  In the first embodiment, an example of means for obtaining hydraulic braking force by brake hydraulic pressure is shown as mechanical braking means. However, even when mechanical braking force is obtained by something other than regenerative braking force such as an electric motor brake (EMB). included.

  In the first embodiment, an example of application to a front-wheel drive hybrid vehicle including one engine, two motor generators, and a power split mechanism has been shown. However, the regenerative braking control device of the present invention includes another power unit structure. A vehicle that performs regenerative braking control that estimates the road surface μ based on wheel speed information and controls the amount of regenerative braking according to the estimated road surface μ, such as a hybrid vehicle, electric vehicle, fuel cell vehicle, etc. driven by front wheels or rear wheels. Can be applied if present.

1 is an overall system diagram illustrating a hybrid vehicle to which a regenerative braking 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 regenerative braking 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 car to which the regenerative braking control device of Example 1 was applied. It is an alignment chart which shows each vehicle mode in the hybrid vehicle to which the regenerative braking control apparatus of Example 1 was applied. 6 is a flowchart illustrating a flow of a road surface μ estimation process executed by the integrated controller of the first embodiment. It is a figure which shows the wheel jump determination map used by the road surface (micro | micron | mu) estimation process of Example 1. FIG. It is a figure which shows the regeneration-hydraulic braking amount distribution map with respect to the estimated road surface (mu) obtained by the road surface (mu) estimation process of Example 1. FIG. A time chart showing the estimated vehicle speed, detected wheel speed, estimated road surface μ characteristics in dry road behavior, and estimated vehicle speed, detected wheel speed, estimated road surface μ, and control road surface μ characteristics in low μ road behavior is there.

Explanation of symbols

E engine
MG1 1st motor generator
MG2 Second motor generator
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 (wheel speed detection means)
13 Front right wheel speed sensor (wheel speed detection means)
14 Rear left wheel speed sensor (wheel speed detection means)
15 Rear right wheel speed sensor (wheel speed detection means)
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 24, 25, 26 Two-way communication line

Claims (6)

Road surface μ estimation means for estimating the road surface μ based on wheel speed information;
Regenerative braking control means for controlling the amount of regenerative braking according to the estimated road surface μ;
In a vehicle regenerative braking control device comprising:
When the regenerative braking control means detects a situation where the estimated road surface μ changes suddenly, the regenerative braking control device maintains the regenerative braking amount immediately before the road surface μ suddenly changes. In the regenerative braking control device for a vehicle according to claim 1,
The road surface μ estimation means estimates that the road surface is a low μ road as the difference between the detected value from the wheel speed sensor and the vehicle speed estimated from the driving torque of the power source increases. Braking control device. In the regenerative braking control device for a vehicle according to claim 1 or 2,
Wheel jump determination means for determining wheel jump is provided,
When the road surface μ estimation means determines a wheel jump, the road surface μ estimation unit interrupts the estimation of the road surface μ and fixes the road surface μ to the estimated road surface μ immediately before the determination of the wheel jump. In the regenerative braking control device for a vehicle according to claim 3,
The road surface μ estimation means refers to the fixed road surface μ and resumes estimation of the road surface μ when the detected wheel speed deviates from the wheel jump determination area after fixing the estimated road surface μ based on the determination of the wheel jump. A regenerative braking control device for a vehicle. In the regenerative braking control device for a vehicle according to claim 3 or 4,
The vehicle performs regenerative braking on only one of the front and rear wheels based on a deceleration request operation,
Wheel speed detection means for detecting the wheel speed is provided,
The wheel jump determination means determines a wheel jump when at least one of the conditions of a sudden speed reduction of a regenerative braking wheel and a rapid speed increase of a non-regenerative braking wheel is satisfied. apparatus. In the regenerative braking control device for a vehicle according to any one of claims 1 to 5,
Mechanical braking means for generating mechanical braking force on the other left and right wheels that do not perform regenerative braking at least among the front and rear wheels;
The regenerative braking control means gives a regenerative braking amount to only one of the front and rear wheels in a high μ region where the estimated road surface μ is equal to or less than the first set road surface μ, and the estimated road surface μ is changed from the first set road surface μ to the second set road surface. In the region up to μ, the lower the μ, the more the regenerative braking amount of one of the front and rear wheels is limited, and the other mechanical braking force of the front and rear wheels is increased according to the limiting amount, so that the estimated road surface μ is the second. In the low μ region that is greater than or equal to the set road surface μ, perform regenerative cooperative control that regulates the maximum regenerative braking amount limit so that the braking force distribution ratio of the front and rear wheels by the regenerative braking force and mechanical braking force is the ideal distribution ratio A regenerative braking control device for a vehicle.

Images