JPH04293627A - Traction control device for vehicle - Google Patents

Abstract

PURPOSE:To effectively perform the traction control over the whole running region by concurrently performing the ignition timing retard control and shift control, changing the shift characteristic, and performing the shift-up control to invariably keep the engine rotating speed in the retardable rotation area. CONSTITUTION:An engine control unit 30 has an ignition timing controller 31 inputted with the engine rotating speed N of a crank angle sensor 21, the signal of the crank angle theta, and the signal of the intake air quantity Q of an air flow meter 22 and sets the optimum ignition timing thetaig in response to running conditions based on the basic fuel injection quantity Tp and the engine rotating speed N. A shift control unit 40 has a shift mode setting section 41 inputted with the vehicle speed V using the pseudo vehicle speed of a slip control unit 20 and the throttle opening alpha of a throttle opening sensor 24 and sets the shift mode based on a shift pattern map, and the shift signal corresponding to the shift mode is outputted to a shift means 25 via an output section 42.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a traction control system (TCS) that controls engine output etc. to prevent wheel slip during acceleration of a vehicle, and more specifically, ignition timing retard control as means for reducing engine output. This paper relates to a method using

0002

[Prior Art] Generally, in a vehicle such as an automobile, if the driving force generated by the engine output is greater than necessary compared to the tire grip force during acceleration, the wheels may slip, impairing steering stability, fuel efficiency, etc. In recent years, such wheel slips have become more likely to occur, especially due to increased engine output. Therefore, traction control has been proposed in which, when wheel slip is detected during acceleration, the engine output is forcibly reduced to prevent slip. In this case, there are methods to reduce the engine output by controlling the engine's fuel injection amount, ignition timing, intake air amount, boost pressure, etc. Retard control of the ignition timing is easy to control and prevents shocks from fluctuations in engine output. There are advantages such as less

[0003] Here, the case of retard control of the ignition timing of the engine will be explained. The retard control increases the afterburning of the fuel, which directly affects the exhaust temperature Tex. The exhaust gas temperature characteristic when the throttle is fully open is generally set by the engine speed N and the retard amount R as shown in Figure 3. In this case, if the exhaust temperature Tex increases, it will affect the damage to the catalyst, so For example 900
An upper limit temperature Tmax of °C is set. From this characteristic, even if the retard amount R is constant, the exhaust temperature Tex will also rise as the engine speed N increases, and in normal control with a small retard amount R0, the exhaust temperature T
ex becomes equal to or lower than the upper limit temperature Tmax. By the way, in traction control, if the engine output is reduced by 30% or 40%, for example,
% decrease, so when the retard amount is increased to R1 and R2, the characteristics of the exhaust temperature Tex become higher and the engine speed decreases to N.
1, N2 reaches the upper limit temperature Tmax in a low state, and if the engine speed N is higher than this, traction control becomes impossible. Therefore, when such ignition timing retard control is used, it is necessary to further reduce the engine rotation speed N by using speed change control and the like to expand the operating range in which traction control is possible.

[0004] Conventionally, regarding the above-mentioned engine output reduction control and speed change control in combination, for example, Japanese Patent Laid-Open No. 61-1
There is a prior art disclosed in Japanese Patent No. 05228. Here, when a sudden start is detected due to an increase in the vehicle speed and engine speed when shifting to the driving range, the engine output is reduced to reduce the shift impact, impact load on the drive system, etc. has been done.

[0005]

[Problem to be Solved by the Invention] However, the above-mentioned prior art is a measure for alleviating the impact and load on the drive system etc. during a sudden start, and the technical idea is different from the traction control of the present invention. There is. Regarding gear shifting, only a shift operation is performed to the driving range, and no control is performed to lower the engine speed by changing the gear shifting characteristics.

The present invention has been made in view of this point, and when wheels slip during acceleration, the ignition timing is retarded to reduce the engine output, and the gear shift is controlled to prevent the catalyst from increasing due to the rise in exhaust temperature. The purpose is to prevent damage and enable traction control to be performed throughout the driving range.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a slip control unit that outputs a traction control signal when a wheel slips during acceleration, and a slip control unit that sets the ignition timing according to at least the engine operating state and ignites the engine. The engine control unit is equipped with an engine control unit that outputs a signal, and a shift control unit that sets a shift mode according to the driving condition and outputs a shift signal, and the engine control unit retards the ignition timing according to the traction control signal. The transmission control unit has means for determining a maximum possible engine rotational speed, and the transmission control unit has means for changing the transmission characteristics according to the maximum engine rotational speed so as not to exceed the maximum engine rotational speed.

[0008]

[Operation] Based on the above configuration, when a traction control signal is output during wheel slip during acceleration, the engine control unit retards the ignition timing, and the transmission control unit adjusts the transmission characteristics according to the maximum engine speed that can be retarded. With this change, the rotation speed is controlled to a range where retardation is possible by sequentially upshifting throughout the driving range, and this allows retardation to be performed without causing damage to the catalyst due to the rise in exhaust temperature that accompanies retard control. Traction control is maintained to effectively prevent wheel slippage.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. Referring to FIG. 2, an outline of the drive system and traction control system of a four-wheel drive vehicle will be explained. Reference numeral 1 denotes an engine, and this engine 1 is connected to a transfer device 4 such as a center differential via a clutch 2 and a transmission 3 to distribute power. One output side of the transfer device 4 has a front drive shaft 5, a front differential 6, and an axle 7.
The other output side is connected to the left and right rear wheels 13L, 13 via the rear drive shaft 9, propeller shaft 10, rear differential 11, and axle 12.
R and is configured to run in four-wheel drive.

To explain the control system, the left and right front wheels 8
Wheel speed sensors 15a to 15d are provided for the rear wheels L, 8R and the rear wheels 13L, 13R, respectively, so as to separately detect the wheel speed ω. Further, a G sensor 16 is provided at the center of the vehicle body to detect acceleration/deceleration G in the longitudinal direction of the vehicle body. Further, the steering device 17 is provided with a steering angle sensor 18 that detects the steering angle φ during turning, and these sensor signals are input to the slip control unit 20. The slip control unit 20 continuously calculates a pseudo vehicle speed Vr during acceleration/deceleration driving, calculates a slip rate S at the time of wheel slip based on this pseudo vehicle speed Vr, wheel speed ω, steering angle φ, etc., and also calculates a target slip rate Sd. is set, the engine output reduction amount is determined from these slip ratios S and Sd, and a traction control signal corresponding to this is output to the engine control unit 30 and the transmission control unit 40. The engine control unit 30 performs ignition timing retard control using a traction control signal to forcibly reduce engine output to prevent slippage. The shift control unit 40 is configured to perform upshift control according to the maximum engine rotation speed Nmax, which is the upper limit of the exhaust temperature Tex when performing ignition timing retard control, and to lower the engine rotation speed N to a rotation range where retardation is possible.

In FIG. 1, an engine control unit 30
The traction control system of the transmission control unit 40 will be explained. The engine control unit 30 has an ignition timing control section 31 into which signals of the engine rotation speed N and crank angle θ from the crank angle sensor 21 and signals of the intake air amount Q from the air flow meter 22 are input, and the basic fuel injection amount Tp and the signal of the intake air amount Q are input. Optimal ignition timing θ according to each driving condition depending on engine speed N
Set up ig. The ignition signal at this ignition timing θig is outputted from the output section 32 to the ignition means 23 based on the crank angle signal. Further, it has a retard amount determination section 33 into which the traction control signal from the slip control unit 20 is input, and determines the retard amount R according to the amount of engine output reduction,
The correction unit 34 on the output side of the ignition timing control unit 31 adjusts the ignition timing θ.
Correct the retard of ig. The retard amount R is input to the maximum engine speed determining section 35, and with reference to the exhaust temperature characteristic map shown in FIG. 3, the maximum engine speed Nmax at which the upper limit temperature Tmax is reached at the retard amount R is determined. On the other hand, the transmission control unit 40 is the slip control unit 20.
Vehicle speed V using pseudo vehicle speed etc., throttle opening sensor 2
Shift mode setting section 41 to which the throttle opening degree α of No. 4 is input.
, a gear shift mode is set based on the gear shift pattern map, and a gear shift signal corresponding to this gear shift mode is outputted by the output section 4.
2 to the transmission means 25. The shift mode setting section 41 has a shift characteristic changing section 43 into which the maximum engine speed Nmax is input, and shifts the shift points indicated by the solid line in FIG. configured to change.

Next, the operation of this embodiment will be explained. First, when the transmission 3 is shifted to the driving range while the engine is running, the shifting power is input to the transfer device 4 and distributed, and is transmitted to the left and right front wheels 8L, 8R and the rear wheels 13L, 13R for four-wheel drive driving. . When driving in four-wheel drive, under conditions where the road surface μ is relatively large and the engine output is not unnecessarily large, it is possible that one of the four wheels or the front and rear wheels 8L, 8R or 13L, 13R slips. Also, slippage is prevented by differential lock and torque distribution control. Therefore, most of the wheels always grip the road surface and the vehicle runs while exhibiting the performance of a four-wheel drive vehicle. At this time, signals from the wheel speed sensors 15a to 15d, the G sensor 16, and the steering angle sensor 18 are input to the slip control unit 20 and processed. That is, the minimum wheel speed ωmi
The grip and slip of the wheels are determined by comparing the vehicle speed by n and the vehicle speed accumulated by integrating the acceleration/deceleration G, and by selecting and using one and the other of the vehicle speeds under these conditions, the pseudo vehicle speed Vr is highly accurate. are calculated continuously. and,
The slip rate S is calculated using the pseudo vehicle speed Vr and the maximum wheel speed ωmax, the optimal target slip rate Sd is set using the pseudo vehicle speed Vr and the steering angle φ, and the engine output reduction amount is determined based on the difference between the two slip rates S and Sd. When the wheels are gripped, the slip rate S becomes approximately equal to the target slip rate Sd, and no traction control signal is output.

On the other hand, in the engine control unit 20, the engine rotation speed N, the crank angle θ,
The intake air amount Q signal of the air flow meter 22 is input,
The ignition timing control section 31 sets the optimum ignition timing θig according to the engine operating condition, and this ignition signal is sent to the ignition means 2.
3 to control the ignition timing. In addition, signals of the vehicle speed V and the throttle opening α from the throttle opening sensor 24 are inputted to the shift control unit 40, and the shift mode setting section 41 sets a gear position according to the driving conditions. The output is output to control the speed change.

By the way, even when traveling in four-wheel drive,
If the road surface μ decreases extremely or the engine output increases more than necessary, the grip force of the four wheels decreases, causing four-wheel slip. Then, the slip control unit 20 outputs to the engine control unit 30 and the transmission control unit 40 a traction control signal of an amount of engine output reduction corresponding to the difference between the slip ratio S and the target slip ratio Sd in this case. Therefore, the retard amount determination unit 33 determines a retard amount R corresponding to the engine decrease amount of the traction control signal, and performs correction control so that the ignition timing θig is delayed by this retard amount R. Therefore, in engine 1, the ignition timing θ
The engine output is forcibly lowered by reducing the combustion pressure and the like due to the delay in ig, and the driving force on the wheel side is also reduced accordingly to prevent slippage.

At this time, the maximum engine speed determining section 35
The maximum engine speed Nmax at which the upper limit temperature Tmax is reached is determined based on the exhaust temperature characteristics, and the speed change characteristics are changed by the speed change characteristics changing section 43 according to this maximum engine speed Nmax. For this reason, afterburning combustion increases due to retard control in the engine 1, and as the engine speed N increases, the exhaust temperature Tex rapidly increases and its upper limit temperature Tmax
When the maximum engine speed corresponding to Nmax is reached,
The gear is upshifted from a low gear to a high gear. Therefore, by this upshift, the engine speed N is lowered by a relatively large amount than the maximum engine speed Nmax, and in this way, the engine speed N is always kept low by sequentially upshifting throughout the driving range, and in this state. The above retard control continues without damaging the catalyst,
This effectively prevents slippage due to a reduction in engine output.

Although the embodiments of the present invention have been described above, it is of course applicable to two-wheel drive vehicles, and the control system is not limited thereto.

[0017]

[Effects of the Invention] As explained above, according to the present invention,
In a system that retards ignition timing using vehicle traction control, the exhaust temperature is always kept below the upper limit, so damage to the catalyst can be reliably prevented when the exhaust temperature rises due to retard control. Ignition timing retard control and shift control are used together to change the shift characteristics and perform upshift control to always keep the engine speed within the range where retardation is possible, effectively controlling traction throughout the entire driving range. be able to. Since the shift characteristics are changed using the maximum engine speed that can be retarded in the exhaust temperature characteristics, the engine speed can be appropriately reduced by upshift control, and the control is easy.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a traction control device for a vehicle according to the present invention.

FIG. 2 is an overall configuration diagram of a drive system and a traction control system of a four-wheel drive vehicle.

FIG. 3 is a diagram of exhaust temperature characteristics showing an engine speed range in which retardation is possible.

FIG. 4 is a diagram illustrating a state in which the speed change characteristics are changed.

[Explanation of symbols] 20 Slip control unit 30 Engine control unit 31 Ignition timing control section 33 Retard amount determination section 34 Correction section 35 Maximum engine speed determination section 40 Speed change control unit 41 Shift mode setting section 43 Shift characteristics change section

Claims (2)

[Claims] Claim 1: A slip control unit that outputs a traction control signal when a wheel slips during acceleration; an engine control unit that outputs an ignition signal by setting an ignition timing that corresponds to at least an engine operating condition; a transmission control unit that sets a transmission mode and outputs a transmission signal; the engine control unit has means for retarding the ignition timing in response to the traction control signal and determining a maximum engine speed at which retardation is possible;
A traction control device for a vehicle, wherein the speed change control unit has means for changing speed change characteristics according to a maximum engine speed so as not to exceed the maximum engine speed. 2. The traction control for a vehicle according to claim 1, wherein the maximum engine speed that can be retarded is determined based on the relationship between the retard amount and the upper limit temperature of the exhaust gas that does not damage the catalyst in exhaust temperature characteristics. Device.