JP2008092683A - Drive torque controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive torque controller for a vehicle that can improve fuel efficiency and prevent the deterioration of braking feeling at the same time, while securing vehicle controllability by generating creep torque. <P>SOLUTION: The drive torque controller for a vehicle, which controls the drive torque output by an electric motor, is provided with a creep torque calculation means, which calculates the creep torque as drive torque when predetermined conditions are satisfied, and a creep torque limitation means, which limits the creep torque before the vehicle stops based on a quantity of state representing vehicle movement. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive torque control device for a vehicle that performs control to generate creep torque.

2. Description of the Related Art Conventionally, in a drive torque control device for a vehicle that does not include a torque converter (with automatic transmission), a drive torque that simulates a creep torque (hereinafter simply referred to as a creep torque) is generated in a low vehicle speed range to improve vehicle controllability. There is something to secure (for example, Patent Document 1). The device described in Patent Document 1 controls the operating state of the electric motor, and reduces the generated creep torque according to the amount of depression of the brake pedal, and makes it zero when the vehicle stops. The reason for controlling the creep torque in this way is to improve fuel efficiency. When the amount of brake operation is large, the driver often tries to stop the vehicle, and creep torque is often unnecessary. In anticipation of such a case, the amount of energy consumption is reduced by reducing the creep torque as the brake operation amount increases.
Japanese Patent Laid-Open No. 7-154905

  However, in the above apparatus, the actual vehicle deceleration (hereinafter simply referred to as deceleration) may be larger than the deceleration planned by the driver. That is, in a vehicle equipped with a general torque converter (with automatic transmission), when creep torque is generated during braking, the braking torque is reduced by the amount of creep torque. Becomes smaller than the target deceleration according to the brake operation amount of the person. And usually, the driver unconsciously schedules that the actual deceleration obtained is insufficient with respect to the target deceleration, and increases the amount of brake operation to cope with the insufficient deceleration (decrease in braking torque). ing. On the other hand, when the control for reducing the creep torque according to the brake operation amount is performed as in the above-described device, a larger deceleration than that planned by the driver is obtained, and the braking feeling is deteriorated. That is, in a drive torque control device that generates creep torque to ensure vehicle maneuverability, there is a problem that it is difficult to achieve both improvement in fuel efficiency and prevention of deterioration in braking feeling.

  The present invention has been made paying attention to the above-mentioned problems, and provides a vehicle drive torque control device capable of achieving both improvement in fuel consumption and prevention of deterioration in braking feeling while generating creep torque to ensure vehicle controllability. With the goal.

  In order to achieve the above object, in the vehicle drive torque control device of the present invention, when a predetermined condition is satisfied in the vehicle drive torque control device for controlling the drive torque output by the electric motor, a creep torque is set as the drive torque. Creep torque calculating means for calculating and creep torque limiting means for limiting the creep torque based on a state quantity representing vehicle motion before stopping the vehicle are provided.

  Therefore, in the vehicle drive torque control device of the present invention, the creep torque is generated to ensure vehicle controllability, the creep torque is limited based on the vehicle behavior value before the vehicle stops, and after the vehicle stops. Since it does not output useless torque, it is possible to achieve both prevention of deterioration of braking feeling and improvement of fuel consumption.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for realizing a vehicle drive torque control apparatus according to the present invention will be described below based on embodiments shown in the drawings.

First, the drive system configuration of the vehicle in the first embodiment will be described.
FIG. 1 is an overall system diagram illustrating a hybrid vehicle by front wheel drive to which the drive torque control device of the first embodiment is applied. The drive system of the hybrid vehicle has 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 the throttle valve and the like are controlled based on a control command from an engine controller 1 described later.

The first and second motor generators MG1 and MG2 are synchronous motor generators in which permanent magnets are embedded in a rotor and a stator coil is wound around a stator. Based on a control command from a motor controller 2 described later, a power control unit The three-phase alternating current generated by 3 is applied to be controlled independently.
First and second motor generators MG1 and MG2 can operate as electric motors that are driven to rotate by receiving electric power from battery 4 (hereinafter, this state is referred to as “powering”), and the rotor is driven by an external force. In the case of rotation, 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. 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. The 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).

Next, a control system for the hybrid vehicle of the first embodiment will be described.
As shown in FIG. 1, the control system of the hybrid vehicle of 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 engine controller 1 outputs a command for controlling the engine operating point (Ne, Te) according to the target engine torque Te or the like output from the integrated controller 6, for example, to a throttle valve actuator (not shown).

  The motor controller 2 determines the motor operating point (Nm1, Tm1) of the first motor generator MG1 and the motor operating point (Nm2, Tm1) of the first motor generator MG1 according to the target motor generator torque Tm output from the integrated controller 6. Tm2) and a command to control each independently are 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 can supply power to both motor generators MG1 and MG2 with less current with reduced loss. Power system high voltage system. A drive motor inverter is connected to the stator coil of second motor generator MG2. A generator coil inverter is connected to the stator coil of first motor generator MG1. The joint box is connected with a battery 4 that is discharged during power running and charged during regeneration.

  The brake controller 5 includes a wheel speed from each of the wheel speed sensors 12 to 15, a steering angle from the steering angle sensor 16, a brake operation amount BS from the master cylinder pressure sensor 17 and the brake stroke sensor 18, and a yaw rate sensor 27. And the lateral acceleration from the lateral acceleration sensor 28 are input. In addition to calculating the required braking torque Tb * based on the brake operation amount BS, the brake controller 5 executes a predetermined calculation process based on the above information. The brake controller 5 outputs a control command based on these calculation processing results to the integrated controller 6 and the brake hydraulic pressure unit 19. Each wheel wheel cylinder 20 to 23 is connected to the brake hydraulic unit 19.

  The brake controller 5 performs ABS control for independently controlling the brake fluid pressure of each wheel in response to a control command to the brake fluid pressure unit 19 during low-μ road braking, sudden braking, or the like. In addition, when a deceleration request is made by brake depression or accelerator release operation, etc., if the regenerative braking torque alone is insufficient, a control command is output to the brake hydraulic unit 19 to compensate for the shortage with the hydraulic braking torque By doing so, regenerative cooperative brake control is performed.

  The integrated controller 6 includes an accelerator opening APO from the accelerator opening sensor 7, a vehicle speed VSP from the vehicle speed sensor 8, an engine speed Ne from the engine speed sensor 9, and a first motor generator speed sensor (resolver). ) The first motor generator rotational speed Nm1 from 10 and the second motor generator rotational speed Nm2 from the second motor generator rotational speed sensor (resolver) 11 are input. The integrated controller 6 executes predetermined arithmetic processing based on these pieces of information, and outputs a control command based on the processing result to the engine controller 1 and the motor controller 2. The integrated controller 6, the engine controller 1, the motor controller 2, and the brake controller 5 are connected by bidirectional communication lines 24, 25, and 26, respectively, for information exchange.

  The integrated controller 6 manages the energy consumption of the entire vehicle and has a function of running the vehicle with the highest efficiency. A control command such as the target engine torque Te is output to the engine controller 1 to perform engine operating point control, and a control command such as the target motor generator torque Tm is output to the motor controller 2 to perform motor operating point control. Furthermore, regenerative cooperative brake control is performed by a control command to the brake controller 5.

Next, drive torque performance will be described.
In the hybrid vehicle of the first embodiment, 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. The driving torque of the hybrid vehicle of the first embodiment is the sum of the engine direct driving torque (subtracting the torque necessary for driving the generator from the engine total driving torque) and the driving torque of the first and second motor generators MG1, MG2 It is the sum of the motor driving torque. In the configuration of the maximum drive torque, the motor drive torque occupies more as the vehicle speed is lower. In this way, since there is no transmission and the engine E is driven by adding the direct drive torque of the engine E and the electric motor drive torque converted electrically, the full power of the accelerator pedal is fully opened from low to high speeds from the state of low steady-state power. Until now, the drive torque can be controlled seamlessly with good response to the driver's request.

Next, the braking torque performance will be described.
In the hybrid vehicle of the first embodiment, at the time of a deceleration request operation such as a brake depressing operation or an accelerator release operation, a regenerative braking torque is output to the drive wheels, and the second motor generator MG2 operating as a motor is operated as a generator. Thus, a regenerative braking system is adopted in which the kinetic energy of the vehicle is converted into electric energy, collected in the battery 4 and reused.

Next, the vehicle mode will be described.
The hybrid vehicle of the first embodiment has each mode of “stop”, “start”, “engine start”, “steady travel”, and “acceleration” as vehicle modes.
When the vehicle is stopped, the engine E is automatically stopped except when the air conditioner is used or when the battery is charged. In the “stop mode”, the engine E, the generator MG1, and the motor MG2 are stopped.
At the time of starting, the engine E is started by turning the ignition key. When the engine E is warmed up, the engine E is stopped immediately. In the “engine start mode”, the generator MG1 having a function as an engine starter rotates the sun gear S and starts the engine E.
Fuel is cut off in areas where engine efficiency is poor, such as when starting, running at extremely low speeds, or during light loads on a gentle slope, and engine E stops and runs with motor MG2. In “start mode”, the vehicle starts with only the driving torque of the motor MG2.
During normal travel, the drive torque of the engine E directly drives the left and right front wheels via the power split mechanism TM and drives the generator MG1, and uses the electric power to assist the motor MG2. In the “steady traveling mode”, the vehicle travels mainly by the driving torque of the engine E, and the power generation amount is minimized in order to increase efficiency. In the “acceleration mode”, the number of revolutions of the engine E is increased and power generation by the generator MG1 is started, and the driving torque of the motor MG2 is applied using the electric power and the electric power of the battery 4 for acceleration.
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.
Note that, in the “steady travel mode”, if the rotational speed of the generator MG1 is increased while suppressing the increase in the rotational speed of the engine E, the rotational speed of the motor MG2 shifts to the negative side, and reverse traveling can be achieved.

[Drive torque control]
Next, drive torque control according to the first embodiment will be described. The integrated controller 10 applies a limiter to the primary target motor generator torque Tm (hereinafter, Tm0) calculated based on the accelerator opening APO, the vehicle speed VSP, and the like under a predetermined condition, and finally sets the value after the limiter is applied. The target motor generator torque Tm is output to the motor controller 2.

(Primary target motor generator torque calculation)
Hereinafter, in the first embodiment, only the scene where the engine E is stopped and the vehicle is driven by the motor MG2 will be described. Therefore, the target motor generator torque Tm is simply referred to as drive torque Tm.
If the accelerator opening APO is not zero, the integrated controller 10 calculates a driving torque Tm0 that satisfies the required driving torque according to the accelerator opening APO.

  On the other hand, when the accelerator opening APO is switched to zero, that is, at the time of a deceleration request operation by releasing the accelerator pedal, the driving feeling in a vehicle having an automatic transmission with a normal torque converter is simulated according to the driving conditions. A drive torque Tm0 that can be realized is calculated. Specifically, the regenerative braking torque output state is switched to the creep torque output state according to the vehicle speed as follows.

  When the vehicle speed VSP is equal to or higher than a predetermined engine idle rotation equivalent vehicle speed Vidle, a regenerative braking torque (negative drive torque Tm0) corresponding to the engine brake is calculated. As a result, an appropriate vehicle deceleration is generated. Here, the engine idle speed equivalent vehicle speed Vidle is calculated based on a hypothetical first speed gear ratio and a predetermined engine idle speed when it is assumed that a stepped automatic transmission is provided.

  As the vehicle speed decreases, the regenerative braking torque Tm0 is gradually reduced. When the vehicle speed becomes Vidle, the magnitude of the regenerative braking torque Tm0 is made zero. When the vehicle speed is switched below Vidle, a positive drive torque Tm0 corresponding to the creep torque generated by the torque converter is calculated in order to generate an appropriate creep running feeling. Specifically, a drive torque Tm0 that simulates the output torque characteristics of a general torque converter is calculated in consideration of a predetermined torque converter speed ratio. The calculated Tm0 gradually increases as the vehicle speed decreases.

(Limiter processing)
FIG. 2 shows a map 1 for setting the drive torque upper limit value Tm * which the integrated controller 10 has. When the driving torque Tm0 calculated as described above is equal to or less than the upper limit value Tm * set using the map 1 (Tm0 ≦ Tm *), the integrated controller 10 sets the driving torque Tm0 as the final driving torque Tm. Set. On the other hand, when the drive torque Tm0 is larger than the upper limit value Tm * (Tm0> Tm *), the upper limit value Tm * is set as the final drive torque Tm. By performing drive torque control by limiter processing using a map stored in advance as described above, a control law for sequentially calculating Tm based on a plurality of parameters becomes unnecessary, and control can be simplified. Hereinafter, setting of the upper limit value Tm * using the map 1 will be described.

  The map 1 is three-dimensional, and the driving torque upper limit value Tm * is determined from the required braking torque Tb * and the vehicle behavior value. The vehicle behavior value is a state quantity representing vehicle motion, as will be described later, and serves as an index of vehicle behavior at the time of stopping. In the first embodiment, the vehicle speed VSP is used as the vehicle behavior value. Map 1 is based on a trapezoidal two-dimensional map that gradually decreases the creep torque upper limit value Tm * when the required braking torque Tb * exceeds a predetermined value, and this two-dimensional map is stretched along the vehicle behavior value axis. And it has the shape which provided the wedge-shaped crack in the vehicle behavior value zero vicinity. Since the map 1 is symmetric in the positive and negative axis directions (forward / reverse of the vehicle) of the vehicle behavior value, only the positive direction will be described below.

First, a description will be given along the axial direction of the required braking torque Tb *. Hereinafter, the minute vehicle speed Vstop indicates a minute vehicle speed just before stopping or immediately after starting.
First, the case where the vehicle speed VSP is fixed to a predetermined value equal to or lower than the engine idle rotation equivalent vehicle speed Vidle and equal to or higher than a predetermined minute vehicle speed Vstop0 will be described. When the required braking torque Tb * is not less than zero and not more than the predetermined value Tb2 *, the upper limit value Tm * is maintained at the predetermined maximum value Tm * max and is not decreased. When the required braking torque Tb * is not less than the predetermined value Tb2 * and not more than the predetermined value Tb3 *, the upper limit value Tm * is decreased as the required braking torque Tb * increases. In the region where Tb * is equal to or greater than the predetermined value Tb3 *, the upper limit value Tm * is set to zero.

  Second, the case where the vehicle speed VSP is fixed to zero, that is, the case where the vehicle is stopped will be described. When the required braking torque Tb * is not less than zero and not more than the predetermined value Tb1 *, the upper limit value Tm * is maintained at the maximum value Tm * max and is not decreased. On the other hand, when the required braking torque Tb * is not less than the predetermined value Tb1 * and not more than the predetermined value Tb2 *, the upper limit value Tm * is decreased along the surface N2 as the required braking torque Tb * increases. In the region where the required braking torque Tb * is equal to or greater than the predetermined value Tb2 *, the upper limit value Tm * is set to zero.

Next, the vehicle behavior value (vehicle speed VSP) will be described along the axial direction.
First, when the required braking torque Tb * is fixed to a predetermined value that is greater than or equal to zero and less than or equal to Tb1 *, the upper limit value Tm * is maintained at the maximum value Tm * max and is not decreased in all vehicle speed regions.

  Second, the case where the required braking torque Tb * is fixed to a predetermined value not less than Tb1 * and not more than Tb2 * will be described. When the vehicle speed VSP is below Vidle and above Vstop0, the upper limit value Tm * is maintained at the maximum value Tm * max and is not reduced. When the vehicle speed VSP is greater than or equal to zero and less than or equal to Vstop0, the upper limit value Tm * decreases along the plane N3 as the vehicle speed VSP decreases, and below the vehicle speed at the point where the intersection line L1 between the plane N2 and the plane N3 intersects. Maintain the value Tm * at the intersection and do not decrease it.

  Third, the case where the required braking torque Tb * is fixed to a predetermined value not less than Tb2 * and not more than Tb3 * will be described. When the vehicle speed VSP is equal to or lower than Vidle and equal to or higher than Vstop, the upper limit value Tm * is maintained at the value Tm * on the surface N1, and is not decreased. When the vehicle speed VSP is greater than or equal to zero and less than or equal to Vstop, the upper limit value Tm * decreases as the vehicle speed VSP decreases. When vehicle speed VSP is zero, upper limit value Tm * is set to zero. For example, when the required braking torque Tb * is fixed at Tb4 *, when the vehicle speed VSP is equal to or lower than Vidle and equal to or higher than Vstop1, the upper limit value Tm * is maintained at the value Tm1 * on the line segment L2 and is not decreased. When the vehicle speed VSP is greater than or equal to zero and less than or equal to Vstop1, the upper limit value Tm * is decreased along the dotted line L3 as the vehicle speed VSP decreases, and when the vehicle speed VSP is zero, the upper limit value Tm * is set to zero.

  Fourth, when the required braking torque Tb * is fixed to a predetermined value equal to or greater than Tb3 *, the upper limit value Tm * is set to zero in the entire vehicle speed range.

[Operation of Example 1]
(Prevents deterioration of braking feeling)
FIG. 3 is a time chart showing braking G (vehicle deceleration) when the vehicle is stopped using the drive torque control apparatus according to the first embodiment.

The brake is not depressed before and after t1, and the required braking torque Tb * is zero.
At t1, the accelerator that has been stepped on so far is returned, and the accelerator opening APO is switched to zero. Since the vehicle speed VSP is V0 and is equal to or higher than the engine idle rotation equivalent vehicle speed Vidle, the regenerative braking torque Tm0 is calculated. Until t4, since the vehicle speed VSP is equal to or higher than Vidle, the limiter process by map 1 is not performed (Tm = Tm0). Therefore, after t1, the vehicle speed VSP gradually decreases due to regenerative braking torque Tm0, travel resistance, etc., and braking G1 is generated. The regenerative braking torque Tm0 gradually approaches zero as the vehicle speed VSP decreases.

  Brake operation is started at t2, and operation is completed at t3. During this time, since the required braking torque Tb * gradually increases from zero, in addition to the regenerative braking torque Tm0 output to the drive wheels, hydraulic braking torque that satisfies the required braking torque Tb * is applied to each wheel. Therefore, the vehicle speed VSP gradually decreases at a larger decrease rate than in t1 to t2, and braking G2 larger than braking G1 is generated.

  At t3, the required braking torque Tb * becomes a constant value. This value is assumed to be a value Tb4 * shown in Map 1, and Tb * is maintained at Tb4 * after t3.

  At t4, the reduced vehicle speed is switched to less than Vidle. Therefore, the sign of the calculated drive torque Tm0 is switched from negative to positive, and the regenerative braking torque output is switched to the creep torque output. Further, since the vehicle speed is equal to or lower than Vidle, the upper limit value Tm * is set using the map 1 and the limiter process is performed.

  After t4, as the vehicle speed VSP decreases, the drive torque Tm0 gradually increases from zero by simulating creep torque. Since Tb * is a constant value Tb4 *, the upper limit value Tm * set based on the map 1 is Tm1 * until t5 when the vehicle speed is Vstop1. During the period from t4 to t5, the driving torque Tm0 is equal to or lower than the upper limit value Tm1 *, so that the Tm set to Tm0 continues to increase gradually. As a result, braking torque Tb4 * applied to the wheels and creep torque torque Tm are applied to the drive wheels. Therefore, the total braking torque (| Tb4 * -Tm |) gradually decreases, and the rate of decrease in vehicle speed VSP gradually decreases. Therefore, the magnitude of the braking G gradually decreases from G2.

  At t5, the reduced vehicle speed is switched to the minute vehicle speed Vstop1 or less. Since Tb * is a constant value Tb4 *, Tm * is set on the line segment (dotted line) L3 of map 1 after t5 until t7 when the vehicle stops. That is, as the vehicle speed VSP decreases from Vstop1 toward zero, Tm * decreases from Tm1 * toward zero along the line segment L3.

  At t6, the decreased Tm * matches the increased Tm0 at Tm2 *. Since tm0 becomes larger than Tm * after t6, the final Tm becomes the upper limit value Tm *. Therefore, Tm (= Tm *) decreases along the line segment L3 and becomes zero at t7 when the vehicle speed VSP becomes zero. Accordingly, the drive torque Tm is limited to zero just before stopping, and the creep torque output is released.

  At t7, the vehicle speed VSP becomes zero and the vehicle stops. Since the vehicle speed VSP is zero, the braking G is also zero. Since the upper limit value Tm * is zero while the vehicle is stopped, the driving torque Tm is maintained at zero.

  As described above, during the period from t4 when the vehicle speed VSP becomes Vidle to t7 when the vehicle speed becomes zero, the creep torque Tm is output and the rate of decrease of the vehicle speed VSP (vehicle deceleration) gradually decreases, so braking immediately before stopping G is sufficiently small. Therefore, the brake feeling does not deteriorate.

(Prevents vehicle sliding down)
FIG. 4 is a time chart showing vehicle speed and the like when starting on a slope using the drive torque control apparatus of the first embodiment. The case of starting on an uphill is shown.

Before t1, the vehicle speed VSP was zero and the vehicle was stopped. The accelerator is not stepped on, the accelerator opening APO is zero, and the drive torque Tm is not generated. The brake is depressed before and after t1, and a constant required braking torque Tb * is output until t3. Here, the required braking torque Tb * indicates an upper limit value of the (hydraulic pressure) braking torque Tb that can actually be generated in the wheel. In order to simplify the explanation, the output constant required braking torque Tb * is assumed to be a value Tb2 * in the map 1.
Hereinafter, the starting direction is the positive direction, and the backward direction (the direction in which the vehicle slides down the hill) is the negative direction. Due to the uphill, the vehicle is subject to gravity due to gravity (hereinafter simply referred to as load) in the negative direction. The braking torque Tb actually generated in the wheel has the same magnitude as the torque Tb0 (constant value) acting in the negative direction on the wheel due to the load, and the direction is the positive direction opposite to Tb0. Note that the size of Tb0 is smaller than Tb2 *.

After t1, the accelerator is depressed and the accelerator opening APO starts to increase, and the driving torque Tm0 corresponding to the accelerator opening APO is calculated. After t1, both the accelerator and the brake are stepped on until t5 when the brake is completely returned.
After t2, since the accelerator opening APO is held at the constant value APO1, Tm0 is also maintained at the constant value Tm01.

  Until t3, the required braking torque Tb * is a constant value Tb2 * and the vehicle speed is zero. Therefore, Tm * set by the map 1 is zero. Since Tm0 ≧ Tm *, the final Tm is zero. In other words, Tm is cut by the amount of Tm0 and decreases (shaded area).

  At t3, the brake starts to be released and is completely returned at t5. Therefore, the required braking torque Tb * starts to decrease from Tb2 * toward zero, becomes Tb1 * at t4, and becomes zero at t5.

  Since vehicle speed VSP is zero between t3 and t4, Tm * increases from zero to Tm * max along slope N2 of map 1. For convenience of explanation, if Tm01 is substantially the same size as Tm * max, Tm01 is equal to or greater than Tm * from t3 to t4, so Tm is Tm *. Therefore, as Tm * increases, the driving torque Tm also increases from zero to Tm01 (≈Tm * max) along the slope N2.

  On the other hand, the braking torque Tb actually generated in the wheel is a value obtained by subtracting the driving torque Tm from the torque Tb0 due to the load (Tb = Tb0−Tm). In other words, the braking torque Tb as the reaction force of the load is reduced by being replaced with the increasing driving torque Tm, and then reversed negatively to cancel the increase in the driving torque Tm. From t3 to t4, the sum (Tm + Tb) of the driving torque Tm and the braking torque Tb is balanced with the torque Tb0 due to the load.

  After t4, Tm is constant at Tm01 (≈Tm * max). On the other hand, after t4, since the magnitude of Tb (negative value) is limited by Tb *, it gradually decreases from Tb1 * (negative value) toward zero. Therefore, the sum (Tm + Tb) of the driving torque Tm and the braking torque Tb exceeds the torque Tb0 due to the load. In other words, an extra drive torque Tm for starting the vehicle is generated in addition to the torque Tb0 necessary for supporting the load as a total by the decrease in the magnitude of Tb (negative value). Therefore, the vehicle speed starts to increase from zero.

  As described above, since the torque Tb0 necessary to support the load is always supplied to the wheel by the sum of the braking torque Tb and the driving torque Tm (Tm + Tb) from t3 to t5 when the brake is returned, the slope The vehicle does not slide down when starting. Further, since the increase of the drive torque Tm is completed at t4 before t5 when the brake is completely returned, it is possible to start the hill quickly.

[Effects of Example 1 in Comparison with Comparative Example]
Hereinafter, virtual comparative examples 1 and 2 are set, and these are compared with the first embodiment. Comparative examples 1 and 2 are both drive torque control devices for hybrid vehicles, and are common to the first embodiment in that a limit is applied to the drive torque Tm using a map. However, Comparative Examples 1 and 2 are different from the first embodiment in that the upper limit value Tm * is set only in relation to the required braking torque Tb * and the Tm0 is limited without considering the vehicle behavior factor. Further, Comparative Example 2 is different from Example 1 in that Tb * is reduced corresponding to the restriction of Tm0.

  FIG. 5 is a map 2 used by Comparative Examples 1 and 2. When the required braking torque Tb * is not less than zero and not more than the predetermined value Tb1 *, the upper limit value Tm * is held at the maximum value Tm * max. When the required braking torque Tb * is equal to or greater than Tb1 * and equal to or less than a predetermined value Tb2 *, Tm * is gradually decreased as Tb * increases. When Tb * is equal to or higher than Tb2 * (for example, when Tb4 * is set), Tm * is set to zero. As described above, when Tb * is equal to or higher than Tb1 *, the useless driving torque Tm0 is cut to improve fuel efficiency.

(Deterioration of braking feeling in Comparative Example 1)
In Comparative Example 1, Tm * is set by map 2 regardless of factors of vehicle behavior such as vehicle speed, and Tm * is decreased in accordance with a decrease in required braking torque Tb *. For this reason, the brake feeling is deteriorated as follows.

  FIG. 6 is a time chart similar to that of the first embodiment (FIG. 3) when the vehicle is stopped using the drive torque control device of the first comparative example. Portions common to those in FIG. 3 are denoted by the same reference numerals as those in FIG.

  Since Tb * is zero from t1 to t2, Tm * is set to Tm * max based on Map 2. After t2, Tb * begins to decrease. When Tb * switches to Tb1 * or less at t2 ', Tm * is decreased according to the decrease in Tb *. When Tb * switches below Tb2 * at t2 '', Tm * is set to zero, and thereafter held at zero. After t3, Tb * is maintained at Tb4 *.

  After t4 when the vehicle speed VSP is equal to or lower than Vidle, the creep torque Tm0 is calculated. However, since Tm * is set to zero, the final Tm is zero. That is, the creep torque Tm0 is cut and does not occur. Therefore, after t4, until the vehicle stops, a large braking torque is generated against the will of the driver who is operating the brake on the assumption that creep torque is generated, and the rate of decrease in vehicle speed VSP (vehicle deceleration) Becomes larger. That is, the braking G3 immediately before the vehicle stops increases, so that the braking feeling is deteriorated.

(Vehicle sliding down in Comparative Example 2)
In Comparative Example 2, Tm * is decreased according to the decrease in the required braking torque Tb * using Map 2, and Tm0 is calculated by cutting Tm0 that exceeds Tm *. At the same time, the required braking torque Tb * is reduced by the amount corresponding to the cut of Tm0. For this reason, the deterioration of the braking feeling is prevented as described below, but the vehicle slips down when starting on a slope.

  FIG. 7 is a time chart similar to that of the first embodiment (FIG. 3) when the vehicle is stopped using the drive torque control device of the second comparative example. Portions common to those in FIG. 3 are denoted by the same reference numerals as those in FIG.

  As in Comparative Example 1, after t4 when the creep torque Tm0 is calculated, since Tm * is held at zero, Tm becomes zero and no creep torque is generated. In Comparative Example 2, after t4, Tb * is decreased by the cut Tm0 (shaded portion). In this way, since t4 and until t7 when the vehicle stops, the required braking torque Tb * is gradually reduced, so that a large braking torque against the intention of the driver who performs the braking operation on the assumption that creep torque is generated Will not occur. That is, as in the first embodiment, the braking G is sufficiently small immediately before the stop t7. For this reason, deterioration of the braking feeling is prevented.

  FIG. 8 is a time chart similar to that of the first embodiment (FIG. 4) in the case of starting on a slope using the drive torque control device of the second comparative example. Parts common to those in FIG. 4 are denoted by the same reference numerals as those in FIG.

In Comparative Example 2, Tb * is decreased by the cut of Tm0 from t1 to t4 (shaded portion). Therefore, the size of Tb * (dashed line) decreases from Tb2 * to zero between t1 and t2. The magnitude of Tb * increases gradually from t3 to t4 when the cut amount of Tm0 decreases, but the brake is returned from t3 to t5, so Tb * from t4 to t5 The magnitude of decreases again towards zero. Here, the magnitude of the braking torque Tb actually generated in the wheel is limited by Tb *.
Therefore, after t1 ′ when the magnitude of the braking torque Tb becomes lower than the torque Tb0 due to the load, the vehicle slides down due to the load. The driving torque Tm necessary for the vehicle forward is generated after t3 ′ when the sum (Tm + Tb) of the driving torque Tm and the braking torque Tb exceeds the torque Tb0 due to the load. That is, during t1 ′ to t3 ′, the torque for supporting the load is insufficient (shaded portion), and the vehicle slides down.

(Operational effect of the first embodiment)
In the map 1 for determining the driving torque upper limit value Tm * of the first embodiment, a vehicle behavior factor is introduced as a parameter to obtain a three-dimensional map. The main features of Map 1 in comparison with Map 2 of Comparative Examples 1 and 2 are as follows.

  First, the Tb * region where Tm * is set to a value greater than zero was expanded from zero to Tb2 * to zero to Tb3 *. As a result, even when the brake is stepped over a certain amount and the required braking torque Tb * is equal to or greater than a certain value (Tb1 *), it is not necessary to cut the driving torque Tm uniformly as in Comparative Examples 1 and 2. It is possible to reliably generate the creep torque Tm when necessary. Furthermore, when Tb * is equal to or higher than Tb2 * (above a predetermined vehicle speed Vstop), Tm * is decreased as Tb * increases. Thus, as in the conventional case, when the brake is depressed and the driving torque Tm is expected to be unnecessary, the driving torque Tm can be cut to improve fuel efficiency.

  Second, Tm * is changed according to the vehicle behavior value, specifically the vehicle speed VSP. First, we decided to set Tm * only when the engine idle speed equivalent vehicle speed was less than Vidle. Therefore, after the accelerator opening APO becomes zero, the limiter process is not performed uniformly according to the required braking torque Tb * as in Comparative Examples 1 and 2, but only at the time of executing the control that actually generates the creep torque. By performing the limiter process, an unnecessary restriction process can be eliminated. Next, a predetermined vehicle speed Vstop is provided as a trigger for decreasing Tm *, and Tm is returned to zero immediately before stopping to eliminate creep torque. Therefore, it is possible to prevent a situation in which unnecessary creep torque is continuously output even after the vehicle stops and deteriorate the fuel consumption, and at the same time, it is possible to prevent the deterioration of the vehicle behavior by suppressing the accumulation of torque in the drive system as described later.

  Third, when the vehicle speed VSP is equal to or lower than the predetermined vehicle speed Vstop, the area from zero to Tb2 * has substantially the same shape as the map 2, and the area above Tb2 * is set to a small Tm *. For example, when the vehicle speed VSP is zero, Tm * is set to Tm * max in the range of zero to Tb1 *, and in the region of Tb1 * to Tb2 *, Tm * is decreased as Tb * increases, while Tm2 is equal to or higher than Tb2 *. * Was set to zero. Therefore, for example, when starting on a slope with both the accelerator and brake being depressed as described above, if the amount of brake depression is large, unnecessary driving torque Tm output is prevented and fuel consumption is improved, and the brake is released. When the vehicle is driven, the driving torque Tm is output quickly, so that the vehicle can be prevented from sliding down. The rising speed of the drive torque Tm can be adjusted by, for example, the inclination of the surface N2 of the map 1.

(Set the predetermined vehicle speed Vstop just before stopping)
In Map 1, Tm * is decreased when the vehicle speed VSP falls below the predetermined value Vstop. In other words, the creep torque Tm is limited before stopping but not after stopping, and the timing for limiting Tm is controlled based on the vehicle speed VSP. Hereinafter, the setting of the predetermined vehicle speed Vstop as a trigger for decreasing Tm will be described with reference to FIG.

  From t6 to t7 immediately before stopping, Tm decreases rapidly from Tm2 * toward zero. If the Tm decreases rapidly while the wheel is restricted against rotation by a sufficiently large (hydraulic pressure) braking torque, the torque (torsion) Tm accumulated in the drive system is released all at once. There is a risk that the driver may feel uncomfortable due to the squatting or lifting of the vehicle body. For example, it may be considered that the creep torque Tm is set to zero at a predetermined time after the vehicle stops, but in this case, unnecessary torque continues to be output, and the fuel consumption deteriorates. In addition, the amount of torque accumulated in the drive system becomes large, and the possibility of giving the above-mentioned uncomfortable feeling increases. Therefore, in the first embodiment, after the vehicle speed VSP drops below the engine idle rotation equivalent vehicle speed Vidle, it is assumed that the creep torque Tm is continuously output without being cut, and the creep torque Tm is limited before stopping. did.

Furthermore, in the present Example 1, the timing for limiting the creep torque Tm was optimized as follows. In other words, if Vstop1 is set large and the creep torque Tm decrease timing is advanced, the creep torque Tm is cut without increasing to a sufficient level, and the driver is operating the brake on the assumption that the creep torque Tm is generated. A large braking torque Tb contrary to the intention is generated, and the vehicle speed rapidly decreases from Vstop1.
For this reason, there is a possibility that the braking G immediately before the vehicle stops increases and the deterioration of the braking feeling cannot be prevented. Specifically, the amount of change in the vehicle speed VSP before and after the vehicle stops increases, so that the kinetic energy of the entire vehicle cannot be absorbed by the friction of the suspension, damper, etc., which may cause the body of the vehicle on the spring to sway. Therefore, Vstop1 is set to be sufficiently small so that the kinetic energy released when the vehicle stops is within a range that does not result in such a deterioration in braking feeling.

  Note that, when the minute vehicle speed Vstop is determined, there is a possibility that the vehicle speed sensor 8 may detect such a small value that it cannot be detected by the vehicle speed sensor 8. Therefore, in the first embodiment, the vehicle body speed is detected by the motor generator rotational speed sensor (resolver) 10 or the like. Yes.

As is clear from the above, the vehicle behavior value in the map 1 of the present invention means a state quantity representing the vehicle motion. For example, in addition to the vehicle speed VSP, the vehicle deceleration (= front-rear G) or (vehicle weight distribution or This refers to the amount of vehicle pitching (specified by the spring constant of the suspension, the damping coefficient of the damper, etc.).
The vehicle behavior value that triggers a decrease in Tm is that when the vehicle stops at that value, the kinetic energy of the entire vehicle can be sufficiently absorbed by the friction of the suspension, damper, etc., resulting in the shaking of the vehicle body on the spring. Therefore, it means a value that does not cause deterioration of the braking feel.
Therefore, in the first embodiment, the vehicle speed VSP is used as the vehicle behavior value in the map 1, but not only the vehicle speed VSP but any one of the above state quantities may be used.

[Effect of Example 1]
Hereinafter, the effects of the vehicle drive torque control device of the present invention, which are grasped from the first embodiment, are listed.

(1) In the vehicle drive torque control device for controlling the drive torque Tm output by the electric motor MG2, creep torque calculation means (integrated controller 6) for calculating the creep torque Tm as the drive torque Tm when a predetermined condition is satisfied. In addition, creep torque limiting means (map 1) is provided for limiting the creep torque Tm based on a state quantity representing vehicle motion before the vehicle stops.
Therefore, while generating creep torque to ensure vehicle maneuverability, the braking torque Tm is limited based on the vehicle behavior value before the vehicle stops, and no unnecessary torque Tm is output after the vehicle stops. Both deterioration prevention and fuel efficiency improvement can be achieved.

(2) The predetermined condition described in (1) above is that the vehicle speed VSP is equal to or less than the engine idle rotation equivalent vehicle speed Vidle.
Therefore, the creep torque Tm can be output at an appropriate timing, the vehicle controllability can be ensured, and at the same time, the fuel efficiency can be improved by suppressing the output of the useless torque Tm.

(3) The state quantity in (1) above is the vehicle speed VSP (body speed equivalent value), and the creep torque limiting means (map 1) sets the creep torque Tm when the vehicle speed VSP is switched below the predetermined minute vehicle speed Vstop. I decided to limit it.
Therefore, the change in the kinetic energy of the entire vehicle body before and after the limit of the creep torque Tm is suppressed, and as a result, the vibration on the spring of the vehicle body is suppressed, so that it is possible to prevent the deterioration of the braking feeling due to the creep cut.

(4) The predetermined minute vehicle speed Vstop in the above (3) is a value at which the change in the kinetic energy of the entire vehicle body before and after the limit of the creep torque Tm does not cause a vibration on the spring of the vehicle body.
Therefore, since the change in the kinetic energy of the entire vehicle body before and after the limit of the creep torque Tm does not cause a vibration on the spring of the vehicle body, it is possible to prevent the braking feeling from being deteriorated due to the creep cut.

The vehicle driving torque control device according to the present invention has been described based on the first embodiment. However, the specific configuration is not limited to these embodiments, and the claims relate to each claim. Design changes and additions are allowed without departing from the scope of the invention.
For example, in the first embodiment, the apparatus of the present invention is applied to a hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle as long as it is a vehicle that outputs drive torque by an electric motor.

1 is an overall system diagram illustrating a vehicle to which a drive torque control device according to a first embodiment is applied. 5 is a map 1 for setting a driving torque upper limit value in the first embodiment. 3 is a time chart showing braking G (vehicle deceleration) and the like when the vehicle is stopped using the drive torque control device according to the first embodiment. 3 is a time chart showing a vehicle speed and the like when starting on a slope using the drive torque control device according to the first embodiment. It is the map 2 which sets the drive torque upper limit in the comparative examples 1 and 2. 10 is a time chart showing braking G (vehicle deceleration) and the like when the vehicle is stopped using the drive torque control device of Comparative Example 1; 10 is a time chart showing braking G (vehicle deceleration) and the like when the vehicle is stopped using the drive torque control device of Comparative Example 2; 6 is a time chart showing vehicle speed and the like when starting on a slope using the drive torque control device of Comparative Example 2;

Explanation of symbols

2 Motor controller 5 Brake controller 6 Integrated controller 11 Second motor generator rotational speed sensor 17 Master cylinder pressure sensor 18 Brake stroke sensor 19 Brake fluid pressure unit E Engine MG2 Second motor generator

Claims (4)

In a vehicle drive torque control device for controlling a drive torque output by an electric motor,
A creep torque calculating means for calculating a creep torque as the driving torque when a predetermined condition is satisfied;
A creep torque limiting means for limiting the creep torque based on a state quantity representing vehicle motion before the vehicle stops;
A drive torque control device for a vehicle, comprising: The vehicle drive torque control device according to claim 1,
The vehicle driving torque control device according to claim 1, wherein the predetermined condition is that the vehicle speed is equal to or lower than a vehicle speed equivalent to engine idle rotation. The vehicle drive torque control device according to claim 1 or 2,
The state torque is a vehicle body speed equivalent value, and the creep torque limiting means limits the creep torque when the vehicle body speed equivalent value is switched to a predetermined value or less. In the vehicle drive torque control device according to claim 3,
The vehicle drive torque control device according to claim 1, wherein the predetermined value is a value that does not cause a swing on a spring of the vehicle body due to a change in kinetic energy of the entire vehicle body before and after the creep torque limit.

Images