JPH051613A - Drive wheel slip control device - Google Patents

Abstract

PURPOSE:To prevent overheating of an exhaust gas purification device when an engine output is reduced, in a drive wheel slip control device. CONSTITUTION:In stationary operating conditions, a table 1 is selected and, according to increase in slip ratio output by an overslip detecting means of drive wheels, an engine output is reduced progressively by an ignition retard, air-fuel ratio leaning of all cylinders, and a means including combination of air-fuel ratio leaning with fuel cut. When a condition in which both an engine speed and a slip ratio exceed a specified limit continues for a specified period, a table 2 is selected and an engine output is reduced progressively by a means not including the ignition retard and the air-fuel ratio leaning of all cylinders, whereby overheating of an exhaust gas purification device can be prevented. Also, in place of the condition in which both the engine speed and the slip ratio exceed specified limits continues for a specified period, even if timing for switching over from the table 1 to the table 2 is set at a time when the floor temperature of the exhaust gas purification device exceeds a specified limit, the overheating of the exhaust gas purification device can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive wheel slip control device for reducing the output of an engine when excessive slip of the drive wheels is detected, and particularly to a vehicle equipped with a catalytic exhaust gas purifying device. Drive wheel slip control device.

[0002]

2. Description of the Related Art In order to prevent the drive wheels from slipping excessively when starting or accelerating a vehicle, when the slip value of the drive wheels exceeds a predetermined value, the output of the engine is reduced to prevent the slippage. In the so-called traction control for suppressing, it is known to use a combination of ignition retard control, air-fuel ratio control and fuel cut control as engine output reduction means (Japanese Patent Laid-Open No. 2-1574).
No. 40).

[0003]

By the way, in an engine equipped with a catalytic exhaust gas purifying device, if the floor temperature of the exhaust gas purifying device rises, not only the exhaust gas purifying performance decreases but also The exhaust gas purification device itself may be damaged by overheating. Therefore, if ignition retard control or air-fuel ratio control is continuously performed to reduce the output of the engine as in the conventional case, the exhaust gas temperature may rise and the exhaust gas purification device may be adversely affected. That measure is necessary.

The present invention has been made in view of the above circumstances, and an object of the present invention is to achieve both output control of an engine and protection of an exhaust gas purification device in a drive wheel slip control device.

[0005]

To achieve the above object, the present invention provides a drive wheel speed sensor for detecting the drive wheel speed of a vehicle, and an excessive slip of the drive wheel based on the output of the drive wheel speed sensor. And an output of an engine having a catalytic exhaust gas purifying device based on an excessive slip detection means that outputs a slip value according to the degree of the excessive slip, and a preset engine output reduction mode and the slip value. In a drive wheel slip control device including engine output reduction means for reducing the engine output reduction mode, when the engine rotation speed exceeds a predetermined value and the slip value exceeds the predetermined value for a predetermined time, the engine output reduction mode And a mode switching means for switching from the normal mode to the exhaust gas temperature lowering mode for lowering the exhaust gas temperature. That.

Further, according to the present invention, a drive wheel speed sensor for detecting a drive wheel speed of a vehicle, an excessive slip of the drive wheel is detected based on an output of the drive wheel speed sensor, and a slip according to the degree of the excessive slip is detected. Drive wheel including excess slip detection means for outputting a value and engine output reduction means for reducing the output of an engine having a catalytic exhaust gas purifying device based on a preset engine output reduction mode and the slip value In the slip control device, when the bed temperature sensor for detecting the bed temperature of the exhaust gas purifying device and the bed temperature output by the bed temperature sensor exceed a predetermined value, the engine output reduction mode is changed from the normal mode to the exhaust gas temperature. The second feature is that the apparatus is provided with a mode switching means for switching to an exhaust gas temperature lowering mode for lowering the exhaust gas.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a drive wheel slip control device according to a first embodiment of the present invention. For example, a throttle valve 3 is provided in the middle of an intake pipe 2 of a 5-cylinder engine 1. The throttle valve 3 has a throttle valve opening (θ
_TH ) sensor 4 is connected and outputs an electric signal according to the opening degree of the throttle valve 3 to output an electronic control unit for engine control (hereinafter referred to as "ENG-ECU").
Supply to 5.

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). The valve opening time of fuel injection is controlled by a signal from the ENG-ECU 5 and is electrically connected to the ENG-ECU 5.

An ignition plug 16 provided for each cylinder of the engine 1 is electrically connected to the ENG-ECU 5, and the ignition timing θ _IG is controlled by the ENG-ECU 5.

On the other hand, an intake pipe absolute pressure (P _BA ) sensor 7 is provided immediately downstream of the throttle valve 3, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is sent to the ENG-ECU 5. Supplied.

The engine speed (Ne) sensor 10 is mounted around a cam shaft or a crank shaft (not shown) of the engine 1, and outputs a pulse (hereinafter referred to as "TDC signal pulse") at a predetermined crank angle position each time the crank shaft of the engine 1 rotates. Is output), and the signal pulse is ENG
-Supplied to the ECU 5.

A catalytic type exhaust gas purifying device 14 is arranged in the exhaust pipe 13 of the engine 1 to remove HC in the exhaust gas,
Purifies components such as CO and NOx. The exhaust gas purification device 14, bed temperature (T _CAT) sensor 15 for detecting the bed temperature T _CAT is attached. O as an exhaust gas concentration detector
_{The 2} sensor 12 is mounted on the exhaust pipe 13 on the upstream side of the exhaust gas purifying device 14, detects the oxygen concentration in the exhaust gas, and outputs a signal corresponding to the detected value.
Supply to.

Further, the ENG-ECU 5 includes an electronic control unit (hereinafter referred to as "TCS") for detecting a drive wheel slip.
-"ECU") 30 is connected. This TCS
-ECU 30 includes drive wheel speed sensors 31, 32 for detecting rotational speeds W _FR , W _FL of left and right drive wheels (not shown).
And driven wheel speed sensors 33, 34 for detecting the rotational speeds W _RR , W _RL of the left and right driven wheels (not shown), and a steering sensor 35 for detecting the turning angle δ of the steering wheel (not shown). Are connected to these sensors 31
˜35 supplies the detection signal to the TCS-ECU 30. The steering sensor 35 outputs an absolute angle of a positive angle (+ 1 °, + 2 °, ...) When turning to the right and a negative angle (-1 °, -2 °, ...) When turning to the left, with the neutral point at zero degree. It is a sensor that does.

In this embodiment, the ENG-ECU is used.
5 constitutes an engine output reducing means and a mode switching means, and the TCS-ECU 30 constitutes an excessive slip detecting means.

The ENG-ECU 5 is a sensor and TCS.
An input circuit 5a having a function of shaping an input signal waveform from the ECU 30, correcting a voltage level to a predetermined level, converting an analog signal value into a digital signal value, a central processing circuit (hereinafter referred to as "CPU") 5b, a storage means 5c for storing various calculation programs executed by the CPU 5b and calculation results, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

The CPU 5b discriminates various engine operating states such as a feedback control operating region to the stoichiometric air-fuel ratio by the O ₂ sensor 12 and an open loop control operating region based on the above-mentioned various engine parameter signals, and at the same time, the engine operating state. According to the following equations (1) and (2), the fuel injection valve 6 synchronized with the TDC signal pulse
Of the fuel injection time T _OUT and the fuel injection time T _MA for acceleration increase not synchronized with the TDC signal pulse.

T _OUT = T _i × K _TCS × K _WOT × K _O2 × K ₁ + T _ACC × K ₂ + K ₃ (1) T _MA = T _iA × K _1A + K _3A (2) Here, Ti is a basic fuel injection time determined in accordance with the basic fuel amount, specifically, the engine speed Ne and the intake pipe absolute pressure P _BA, and a Ti map for determining this Ti value is stored in the storage means 5c. Remembered Ti _A is
It is a fuel increase reference value at the time of acceleration not synchronized with the TDC signal pulse, and is stored in the storage means 5c as a map like Ti.

K _TCS is a lean correction coefficient that is set to a value smaller than 1.0 as will be described later when an excessive slip state of the drive wheels is detected, and is other than the excessive slip state of the drive wheels. Sometimes the value is set to 1.0.

K _WOT is the _enrichment correction coefficient of the mixer when the throttle valve is fully opened, K _O2 is the O ₂ feedback correction coefficient obtained according to the output of the O ₂ sensor 12, and T _ACC is applied when the engine 1 is accelerated. This is an acceleration increase variable.

K ₁ , K ₂ and K _{3 in the} equation (1) and K _1A and K _{3A in} the equation (2) are other correction coefficients and variables calculated according to various engine parameter signals, respectively.
The predetermined value is determined so as to optimize various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state.

The CPU 5b further determines the ignition timing θ _IG according to the engine speed Ne and the intake pipe absolute pressure P _BA .

The CPU 5b outputs a signal for driving the fuel injection valve 6 and the ignition plug 16 via the output circuit 5d, based on the result calculated and determined as described above.

FIG. 2 shows the internal structure of the TCS-ECU 30.
FIG. 3 is a block configuration diagram showing the configuration of the left and right driven wheels.
The detection signals of the sensors 33 and 34 are respectively the first subtraction circuit 41.
And the first average value calculation circuit 46. First decrease
The calculation circuit 41 determines the left and right driven wheel speeds W_RL, W_RRSpeed difference Δ
Vr (= W_RL-W_RR) Is calculated and stored in the first multiplication circuit 42.
Supply. The first multiplication circuit 42 calculates the speed difference ΔVr.
Tread width d (for example, d = 1.2m) of the left and right driven wheels
By multiplying, the yaw rate approximate value Y ′ is obtained. _n(= Δ
Vr × d) and calculates the first memory circuit 43 and the filter circuit.
Input to path 44. The first memory circuit 43 stores the yaw.
Approximate rate Y '_nIs stored and the previous value Y '_n-1The above
Input to the filter circuit 44. Where the subscripts n, n-1
Filtering operation is repeated in a fixed cycle
Therefore, the current value and the previous value of the cycle are shown.

The filter circuit 44 approximates the yaw rate.
Value Y '_nTo filter yaw rate Y_nAlso get
Therefore, the second memory circuit 45 is connected to the output side.
Has been. The second storage circuit 45 is provided in the filter circuit 44.
Output Y_nIs stored and the previous value Y _n-1, Value before last Y_n-2age
Input to the filter circuit 44. The filter circuit 44 is above
Input signal Y'described above_n, Y '_n-1, Y_n-1, Y_n-2Next
Applying to equation (3), the yaw rate Y_nTo calculate the second reduction
It is supplied to the arithmetic circuit 51.

Y _n = α ₁ × Y ' _n + α ₂ × Y' _n-1 + β ₁ × Y _n-1 + β ₂ × Y _n-2 (3) where α ₁ , α ₂ and β ₁ and β ₂ are constants determined by experimental results.

The filter circuit 44 is a recursive low-pass filter (reduced pass filter) and is used to remove the influence of the vibration of the vehicle suspension on the left and right driven wheel speeds W _RL and W _RR . . For example, the fluctuation frequency of the left and right driven wheel velocities W _RL and W _RR due to the vibration and resonance of the suspension while traveling on a rough road is about 10 HZ, while the frequency range of the yaw rate used to control the vehicle motion is about 0 to 2 Hz. Therefore, the filter circuit 44
Approximation Y _'n of the yaw rate as the attenuation band of the above 3Hz
I'm trying to filter. Yaw rate Y _n
Is an estimated value of the actual yaw rate around the center of gravity of the vehicle, and outputs a positive value for right turn and a negative value for left turn.

The first average value calculating circuit 46 calculates the average value V _v (= (W _RL + W _RR ) of the left and right driven wheel speeds W _RL and W _RR.
/ 2) is calculated as a vehicle body speed, and the calculated value is supplied to a calculation parameter selection circuit 47 and a reference deviation (Ds) calculation circuit 54 and a reference drive wheel speed (Vref) calculation circuit 57 which will be described later. The calculation parameter selection circuit 47 has calculation parameters a ₁ , a ₂ , used for calculation in the reference yaw rate (Yb _n ) calculation circuit 48 connected to the output side thereof.
The values of b ₁ and b ₂ are selected according to the vehicle speed V _v ,
The selected value is input to the reference yaw rate calculation circuit 48.

On the other hand, the output side of the steering sensor 35 is
The third memory circuit 49 is connected to the third memory circuit 49.
The road 49 stores the detected turning angle δ and stores the previous turning angle.
Value δ _n-1, The value before two times δ_n-2As reference yaw rate calculation times
Enter on path 48. Output of reference yaw rate calculation circuit 48
A fourth storage circuit 50 is connected to the side of the
The circuit 50 calculates the reference yaw rate Yb._nRemember
The stored value is the previous value Yb _n-1, Value before last Yb_n-2As a base
It is input to the quasi-yaw rate calculation circuit 48. Reference yaw rate
The calculation circuit 48 calculates the change history of the turning angle δ (δ_n-1，
δ_n-2) And the change history of the reference yaw rate Yb itself (Yb
_n-1, Yb_n-2) Based on the current standard yaw
Yb_nIs calculated by the physical model formula (4),
2 of the subtraction circuit 51 and the steering characteristic determination circuit 52
input.

Yb _n = a ₁ × δ _n-1 + a ₂ × δ _n-2 −b ₁ × Yb _n-1 −b ₂ × Yb _n-2 (4) This reference yaw rate Yb _n is the yaw rate Y _n. Similarly, the signal is calculated as a signal representing an ideal yaw rate that is positive when turning right and negative when turning left.

The second subtraction circuit 51 uses the equation (3)
And the reference yaw rate Y _n
b _n deviation between Dr (= Y _n -Yb _n) is calculated and input into the steering characteristic determination circuit 52 and the absolute value circuit 53. The absolute value conversion circuit 53 uses the absolute value | D of the deviation Dr.
The r | is input to the third subtraction circuit 55. The steering characteristic determination circuit 52 determines the deviation D from the reference yaw rate Yb _n.
Based on r and, the steering characteristic is determined as follows,
The result is supplied to the reference deviation (Ds) calculation circuit 54. (1) When Yb _n > 0 and Dr> 0, or Yb _n <
When 0 and Dr <0, oversteering is determined. (2) When Yb _n <0 and Dr> 0, or Yb _n >
When 0 and Dr <0, it is determined that the steering is understeering.

The Ds calculation circuit 54 has a steering characteristic.
Along with the determination result, the vehicle speed V _vAnd steering
The turning angle δ detected by the sensor 35 is input,
The Ds calculation circuit 54 uses the input signals as a reference bias.
The difference Ds is calculated and input to the third subtraction circuit 55.
This reference deviation Ds is the vehicle speed V_v, Steering angle δ and
The yaw rate deviation calculated based on the alling characteristics
It is the reference value of Dr, and the vehicle speed V_vIs small and steered
The larger the angle δ, the larger the value set. This is driven
When the wheel speed, that is, the vehicle speed is low and the turning angle δ is large,
While the steering characteristics of the vehicle are non-linear,
Reference yaw rate calculated by the reference yaw rate calculation circuit 48
To Yb_nIs linear, the reference yaw rate Yb_nWhen
Yaw rate Y_nThis is because the deviation Dr between and becomes large.
For front-wheel drive vehicles, turn the steering
Excessive driving force may cause understeering.
Therefore, the determination result of the steering characteristic determination circuit 52 is
If the steering is under-steering, the reference deviation Ds
To reduce. This means that the yaw rate deviation described below will be eliminated.
Increase the deviation B (= | Dr | −Ds) of the pair value | Dr |
And ultimately acts to reduce the engine output.
It As a result, the above-mentioned understeering tendency is prevented.
You can On the other hand, in the case of rear-wheel drive vehicles, excessive
When driving force is applied, there is no tendency for oversteering.
Therefore, contrary to the case of the front-wheel drive vehicle described above,
-Low engine output when steering condition is detected
The reference deviation Ds is changed in the downward direction.
There is.

The third subtraction circuit 55 calculates the deviation B (= | Dr | −Ds) of the yaw rate deviation absolute value | Dr | and inputs it to the second multiplication circuit 56. The second multiplication circuit 56 multiplies the deviation B by a predetermined constant K to correct a reference driving wheel speed Vref described later.
× B is calculated and supplied to the fourth subtraction circuit 58.

[0034] The average value of the driven wheel velocity calculated by the first average value calculating circuit 46, i.e., the reference driving wheel speed Vref calculation circuit 57 the vehicle speed V _v is inputted, the vehicle body speed V
_As a reference drive wheel speed (Vref) according to _v , a target value V _RP of the drive wheel speed, a first predetermined drive wheel speed V _R1 and a second value
Of the predetermined driving wheel speed V _R2 of the fourth subtraction circuit 5
Enter in 8. The fourth subtraction circuit 58 subtracts the correction term K × B from the three reference drive wheel velocities V _R1 , V _R2 and V _RP to obtain the corrected reference drive wheel velocity V ′ _R1 (= V _R1 − K
XB), _V'R2 (= _VR2- KxB) and _V'RP (= _VRP
-K × B) is input to the DUTY calculation circuit 60 which calculates the slip value DUTY which is a parameter corresponding to the slip state of the driving wheels.

On the other hand, the left and right drive wheel speed sensors 31, 32
The detection signal of is input to the second average value calculation circuit 59,
The second average value calculation circuit 59 calculates the average of the left and right driving wheel speeds.
Value V _W(= (W_FL+ W_FR) / 2) and calculate the DUT
Input to the Y calculation circuit 60.

[0036] The three reference driving wheel speed V _R1, V _R2, and V _RP is the straight line indicating the vehicle speed V _v as shown in FIG. 3, for example, the relationship between the vehicle body velocity V _v and the driving wheel speed V _W A,
Calculated based on B and C. Generally, the slip ratio λ representing the degree of drive wheel slip is calculated by λ = (V _W −V _V ) / V _W (5), and when the slip ratio λ increases,
The longitudinal driving force (that is, the traveling direction of the vehicle) due to the frictional force between the tire and the road surface becomes maximum at the third slip ratio λ ₂ (for example, 15%) as shown by the solid line in FIG. It decreases when it exceeds λ ₂ . The limit lateral force between the tire and the road surface decreases as the slip ratio λ increases, as indicated by the broken line in the figure. Therefore, when the slip λ exceeds the second slip ratio λ ₂ , the driving force in both the vertical direction and the horizontal direction is reduced, and it becomes impossible to obtain a sufficient driving force or a limit lateral force. On the other hand, the slip ratio λ is equal to the first slip ratio λ ₁ (for example, 5
%), The drive wheel slip does not exceed the limit,
It is in a state where a stable grip is obtained.

Considering the above points, the straight lines A and B in FIG. 3 are made to correspond to the first and second slip ratios λ ₁ and λ ₂ in FIG. 4, and the detected drive wheel speed V _W and the vehicle body When the relationship with the speed V _V is in the area between the straight lines A and B, the increasing tendency of the driving force is in the linear area with respect to the increase of the slip rate, so the slip rate λ = λ ₀ (for example, 8%). The driving wheel speed V _RP (corresponding to the straight line C in FIG. 3) is set as the target value of the driving wheel speed, and the driving wheel slip control according to the slip value DUTY described later is performed. However, it is actually a reference driving wheel speed V of the corrected reference driving wheel speed to be used in calculating the DUTY value is corrected by the fourth subtraction circuit _'R1, V' _R2 and V _'RP.

The DUTY calculating circuit 60 detects the drive wheel speed V _W and the corrected reference drive wheel speeds _V'R1 , V '.
By applying and _R2 and V _'RP to the following equation (6) to (10), calculates the slip value DUTY as a parameter according to the degree of drive wheel slip, supplying the results output the calculated the ENG-ECU 5 as a DUTY signal To do.

The _{DUTY = (V RPn- V R1n)} / (V R2n- V R1n) -D n ...... (6) D n = D n-1 + ΔD n ...... (7) ΔD n = K P × ΔV WP + K _I × (V _RPn −V _wn ) + K _D × (ΔV _Wn −ΔV _wn-1 ) ... (8) ΔV _Wn = V _Wn −V _Wn-1 …… (9) ΔV _Wp = (V _{Wn-1 -V RPn-1) - (V} Wn -V RPn) ...... (10) _{here, K P, K I, K} D each predetermined proportional gain, integral gain and derivative gain. Subscripts n, n-
1 represents the current value and the previous value of the cycle because the calculation is repeated in a constant cycle.

By calculating the slip value DUTY using the above equations (6) to (10), the so-called tracking type PID control is applied to the drive wheel slip control, and the noise contained in the detected drive wheel speed V _W. The influence of the component (error element) can be reduced and appropriate drive wheel slip control can be performed. The slip value DUTY becomes larger as the slip ratio λ of the drive wheels becomes higher.

As described above, the slip value DUTY is the reference drive wheel speed V _R1 , V calculated according to the vehicle speed V _v.
Reference drive wheel speed V ′ _R1 , obtained by correcting _R2 and V _RP with a correction term K × B according to steering characteristics (degree of over-steering or under-steering), turning angle δ and vehicle speed V _v , Since it is calculated based on V ′ _R2 , V ′ _RP and the detected drive wheel speed V _W , by performing engine output control using this slip value DUTY, a wide range of vehicle body speed and turning angle can be obtained. Appropriate drive wheel slip control and vehicle yaw motion control are possible throughout.

Next, the contents of the engine output control based on the slip value DUTY output from the TCS-ECU 30 will be specifically described.

As shown in the flow chart of FIG.
In the operating state of _LEVELTable 1
Selected and its TC_LEVELNormal mode based on Table 1
Engine output reduction control is performed.

As shown in the left column of FIG. 5, the TC _LEVEL table 1 includes level N, level R, level 0, level 1, level 2, level 3, level 4, and level 5 depending on the slip value DUTY. The engine output control is performed in eight stages.

FIG. 6 shows the engine output reduction means actually applied at each of the above levels.
~ # 5 indicates the cylinder number. Here, N is normal operation without output reduction, R is output reduction by ignition retard, L is output reduction by making the air-fuel ratio lean, and F / C is output reduction by fuel cut. Thus, at level N, where the slip value of the drive wheel is the smallest, normal operation of all cylinders, ignition retard of all cylinders at level R, and air-fuel ratio of all cylinders at level 0 as the slip value of the drive wheel increases. Leaning, combined use of air-fuel ratio leaning and fuel cut at level 1 to level 4, fuel cut of all cylinders is executed at level 5 where the slip value of the drive wheel is the largest, and as the level N shifts to level 5, The engine output reduction amount is set to gradually increase. This allows
The engine output is reduced according to the magnitude of the slip value DUTY output by the TCS-ECU 30, that is, the magnitude of the slip value of the drive wheels, and excessive slip of the drive wheels is suppressed.

Then, in step S2, the engine speed Ne output from the engine speed sensor 10 is the reference value N _STCH.
(For example, 5000 RPM) is determined. If YES, it is determined in step S3 whether TC _LEVEL exceeds the level R. If YES in step S3, it is further determined in step S4 whether or not a predetermined time (for example, 3 sec) until the timer counts up has elapsed. If YES, that is, the engine speed Ne is equal to the reference value N _STCH . When TC _LEVEL exceeds the level R and a predetermined time has passed,
In step S5, the TC _LEVEL table 2 shown in the right column of FIG.
Is selected to reduce the engine output in the exhaust gas temperature lowering mode. In addition, when Ne becomes equal to or less than the reference value N _STCH in step S2, and TC is set in step S3.
_{When LEVEL} becomes equal to or lower than the level R, the timer is set to zero in step S6 each time.

TC _LEVEL table 2 shown in the right column of FIG.
_Does not have the level R and the level 0 in the TC _LEVEL table 1, and the region of the slip value DUTY corresponding thereto is all at the level 1. Therefore, this TC
_{When the LEVEL} table 2 is selected, the level R ignition retard where the exhaust gas temperature is likely to rise and the air-fuel ratio leaning of all the level 0 cylinders are not performed, and the level N idle at the next stage of the normal operation is performed. The engine output is reduced by making the fuel ratio lean and using fuel cut together.

Thus, in the normal operation state in which the temperature of the exhaust gas is unlikely to rise, the TC _{LEVE L} table 1 is selected to finely control the engine output in the normal mode and effectively suppress the drive wheel slip. it can, also the temperature of the exhaust gas engine rotational speed is high and the slip value DUTY is larger state continues likely to increases rises, the temperature of the exhaust gas is unlikely to rise TC _LEVEL table 2
Can be selected to reduce the engine output in the exhaust gas temperature lowering mode and maintain the performance of the exhaust gas purification device 14 and prevent damage.

[0049] Figure 8 shows a flow chart of a second embodiment of the present invention, switching from the TC _LEVEL table 1 in this example to the TC _LEVEL table 2 is performed by another condition. That is, in step S7, TC _LEVEL
When the table 1 is selected and the bed temperature T _CAT output by the bed temperature sensor 15 of the exhaust gas purification device 14 exceeds the reference value T _CR in step S8, TC is set in step S9.
_LEVEL table 2 is selected to prevent the exhaust gas temperature from rising.

As described above, by directly detecting the floor temperature T _CAT of the exhaust gas purifying device 14 and switching the TC _LEVEL table, overheating of the exhaust gas purifying device 14 can be prevented more reliably.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small modifications can be made without departing from the present invention described in the claims. It is possible to make design changes.

[0052]

As described above, according to the first feature of the present invention, the mode switching means is operated when the predetermined time has elapsed when the number of revolutions of the internal combustion engine exceeds the predetermined value and the slip value exceeds the predetermined value. Because the engine output reduction mode is switched from the normal mode to the exhaust gas temperature reduction mode by
When there is no risk that the exhaust gas temperature will rise excessively, the engine output will be effectively reduced in the normal mode, and when there is a risk that the exhaust gas temperature will rise, the exhaust gas temperature rise mode will be used to raise the exhaust gas temperature. The output of the engine can be reduced while suppressing. As a result, the rise of the floor temperature of the exhaust gas purification device is prevented, and the performance maintenance and damage prevention of the exhaust gas purification device are achieved.

Further, according to the second feature of the present invention, when the floor temperature sensor of the exhaust gas purifying device detects that the floor temperature exceeds a predetermined value, the engine output reduction mode is changed from the normal mode to the exhaust gas temperature reduction mode. Since the gas temperature is switched, even if the bed temperature of the exhaust gas purification device exceeds a predetermined value for some reason, the bed temperature can be promptly lowered to more reliably protect the exhaust gas purification device. .

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a drive wheel slip control device.

FIG. 2 is a block diagram of a drive wheel slip detection electronic control device.

FIG. 3 is a graph showing the relationship between vehicle body speed and drive wheel speed corresponding to the slip ratio of drive wheels.

FIG. 4 is a diagram showing a relationship between a slip ratio of driving wheels and a driving force.

FIG. 5 is a table used in a normal mode and an exhaust gas temperature lowering mode.

FIG. 6 is a table showing the contents of each level of engine output reduction control.

FIG. 7 is a flowchart of a control program of the first embodiment.

FIG. 8 is a flowchart of a control program of the second embodiment.

[Explanation of symbols]

1 ... Engine 5 ... ENG-ECU (engine output reducing means,
Mode switching means) 14 Exhaust gas purifying device 15 Floor temperature sensor 30 TSC-ECU (excessive slip detection means) 31 Drive wheel speed sensor 32 Drive Wheel speed sensor

Claims (2)

[Claims] 1. A drive wheel speed sensor (31, 32) for detecting a drive wheel speed of a vehicle, and a drive wheel speed sensor (3).
1, 32) to detect excess slip of the drive wheels and output a slip value according to the extent of the excess slip, excess slip detection means (30), a preset engine output reduction mode and the slip. In the drive wheel slip control device including the engine output reduction means (5) for reducing the output of the engine (1) having the catalytic exhaust gas purifying device (14) based on the value, the rotation of the engine (1). When the number exceeds a predetermined value and the slip value exceeds the predetermined value for a predetermined time, a mode switching means for switching the engine output reduction mode from the normal mode to the exhaust gas temperature lowering mode for lowering the exhaust gas temperature ( 5) A drive wheel slip control device comprising: 2. A drive wheel speed sensor (31, 32) for detecting a drive wheel speed of a vehicle, and a drive wheel speed sensor (3).
1, 32) to detect excess slip of the drive wheels and output a slip value according to the extent of the excess slip, excess slip detection means (30), a preset engine output reduction mode and the slip. A drive wheel slip control device comprising an engine output reduction means (5) for reducing the output of an engine (1) having a catalytic type exhaust gas purification device (14) based on the above value and the exhaust gas purification device ( 14) The floor temperature sensor (1
5) and mode switching means for switching the engine output reduction mode from the normal mode to the exhaust gas temperature lowering mode for lowering the exhaust gas temperature when the floor temperature outputted by the floor temperature sensor (15) exceeds a predetermined value. 5) A drive wheel slip control device comprising: