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Vehicle slip control

a technology of vehicle slippage and control, applied in the direction of process and machine control, tractors, instruments, etc., can solve the problems of motor torque to be increased, hybrid vehicles tend to be susceptible to this phenomenon, etc., and achieve the effect of reducing the likelihood of torque control of the drive sha

Inactive Publication Date: 2006-07-11
TOYOTA JIDOSHA KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006]Accordingly, an object of the present invention is to reduce the likelihood that the torque control of a drive shaft will result in repeated slippage.
[0007]In order to attain at least part of the above and related objects of the present invention, there is provided a slip control device for use in a vehicle, which includes at least one prime mover for driving a drive shaft of the vehicle. The drive shaft transmits a driving force of the prime mover to the wheels of the vehicle. The slip control device comprises an angular acceleration meter configured to measure an angular acceleration of the drive shaft, and a torque controller. The torque controller enhances torque restrictions of the drive shaft when the angular acceleration exceeds a specific first threshold value, and relaxes the enhanced torque restrictions once the angular acceleration falls below the first threshold value and further satisfies a specific restriction relaxation condition
[0008]According to the above structure, the likelihood of repeated slippage is reduced because the torque restrictions are relaxed only when the specific restriction relaxation condition is satisfied, but not merely when the angular acceleration of the drive shaft falls below the first threshold value.

Problems solved by technology

The above-described slip control technique entails reducing the motor torque once the drive wheels have slipped, but the subsequent reduction in rotational angular speed allows the motor torque to be increased, occasionally leading to another slippage event.
In particular, hybrid vehicles tend to be susceptible to this phenomenon because of the fast motor response to a varying torque.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

first embodiment

D. First Embodiment of Slip Control

[0064]FIG. 3 is a block diagram depicting a circuit structure related to slip control. The master control CPU 272 implements the functions of an angular acceleration determining section 272a and a torque control section 272b. The angular acceleration determining section 272a determines a rotational speed N and an angular acceleration AX (change of rotational speed with respect to time) of the second motor MG2 on the basis of the signal REV2 fed from the rpm sensor 144 via the main motor control CPU 262. The number of rotations per minute (rpm) may, for example, be used herein as the unit of measurement for the rotational speed N. The rpm sensor 144 may, for example, measure the rotational speed N every 16 milliseconds. The angular acceleration determining section 272a calculates the average value Nave (that is, the moving average) of three immediately preceding rotational speeds N. The angular acceleration AX can be determined as a change in the av...

second embodiment

E. Second Embodiment of Slip Control

[0096]In the second embodiment, an even more efficient slip control is achieved by supplementing the above-described control procedure of the first embodiment with a procedure in which restrictions are applied to the rpm N of the second motor MG2.

[0097]FIGS. 12(A) and 12(B) are graphs depicting variations in the angular acceleration AX and rpm N of the second motor MG2. At time t1, the angular acceleration AX is greater than the first threshold value AXT1, so the torque restrictions are enhanced in the manner described in the first embodiment, and a torque restriction map such as that shown in FIG. 7(B) is established, as can be seen in FIG. 12(B). As a result, the torque of the second motor MG2 is restricted, the rpm N is immediately reduced, and the angular acceleration AX is brought below the first threshold value AXT1. However, the torque restriction map subsequently retains the state shown in FIG. 7(B) because the above-described relaxation c...

third embodiment

F. Third Embodiment of Slip Control

[0115]In the third embodiment, the motor torque control of the second embodiment is supplemented with suppressing excessive drive shaft rotation by operating the engine 150 in an idling state under specific conditions.

[0116]FIG. 14 is a diagram illustrating an idling operation shifting area adopted in the third embodiment. As used herein, the term “idling operation shifting area” refers to an area in which the engine 150 is forcibly shifted into an idling state. The master control CPU 272 brings the engine 150 into an idling state when the following condition (S3) is satisfied.[0117](S3): The current motor rpm Nc exceeds a value (Nmax+200) obtained by adding 200 rpm to the upper limit Nmax.

[0118]When the condition S3 is satisfied, the torque from the engine 150 drives the axle 112 even with zero motor torque, allowing the motor rpm to remain unreduced and slippage to continue. In view of this, the engine 150 is forced to operate in an idling state ...

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PUM

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Abstract

Torque restrictions on a drive shaft are enhanced when the angular acceleration AX of the drive shaft exceed a specific first threshold value. The enhanced torque restrictions are subsequently relaxed when the angular acceleration drops below the first threshold value and further a specific restriction relaxation condition is satisfied. The torque restrictions are expressed as a graph representing a relation according to which an upper torque limit Tmax decreases with increased angular acceleration AX. The torque restriction are enhanced or relaxed by moving the position of a torque axis relative to the graph along the angular acceleration axis while preserving a shape of the graph.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a technique for controlling the driving force of a vehicle with consideration for vehicle slip.[0003]2. Description of the Related Art[0004]Hybrid vehicles have been developed in which internal combustion engines and motors are provided as prime movers. A technique for controlling the slip of a hybrid vehicle is disclosed, for example, in JPA 10-304514. According to this technique, drive wheels become more likely to slip, prompting a reduction in motor torque, when the rate of change of the rotational angular speed (also referred to as “angular acceleration”) of a drive shaft exceeds a threshold value. It is thus possible to prevent slip from occurring during an increase in the driving force of a motor.[0005]The above-described slip control technique entails reducing the motor torque once the drive wheels have slipped, but the subsequent reduction in rotational angular speed allows the m...

Claims

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Application Information

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IPC IPC(8): B60K28/16B60K6/20B60K6/365B60K6/445B60L50/16B60W10/06B60W10/08B60W10/10B60W10/26B60W20/00F02D29/02
CPCB60K6/445B60K28/16B60L2240/486B60W10/06B60W10/08B60W10/26B60W20/00B60W2510/1045B60W2540/10Y10S903/903Y10S903/945Y10S903/91Y02T10/62B60W2710/025B60K17/04B60W10/10
Inventor NADA, MITSUHIRO
Owner TOYOTA JIDOSHA KK