JPS6288618A - Device for controlling slippage of four-wheel-driven vehicle - Google Patents

Abstract

PURPOSE:To suppress slippage while relieving a burden to a driver by stopping a differential function when judged slipping from the rotating conditions of front and rear wheels, while operating said differential function when judged a steady traveling condition from a car speed and throttle opening. CONSTITUTION:Rotating condition deta from front wheel rotating condition sensors 51, 52, and from a rear wheel rotating condition sensor 53 are inputted in an acceleration slippage control unit 60 and processed under a prescribed program, to judge the slipping condition..When judged a slipping condition, a differential function stopping signal is outputted to a speed change control unit 40. Thereby, the control unit 41 stops the control of a differential controlling solenoid 20. On the other hand, a car speed 30 and a throttle valve opening 31 are inputted in the control unit 60 and, when judged a steady traveling condition from these inputted signals, the control unit 60 removes the differential function stopping signal, to restore the differential function. By this construction a burden to a driver can be relieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a slip control device for a four-wheel drive vehicle, and more specifically, the present invention relates to a slip control device for a four-wheel drive vehicle. The present invention relates to a slip control device for a four-wheel drive vehicle that controls a differential means provided therein.

[Prior Art] Four-wheel drive vehicles have become widely popular in recent years because they can safely drive on rough roads such as muddy areas or snow-covered roads, and they also have excellent performance on pitching and stability when driving at high speeds. It has reached this point. Such four-wheel drive vehicles are equipped with a differential mechanism between the front and rear wheels in order to absorb the difference in rotational speed between the front wheels and the rear wheels that occurs when turning. On the other hand, if at least one of the four wheels enters a rough road and spins, the driving force is no longer transmitted to the other wheels due to the action of the differential mechanism.

As a countermeasure against such a case, a mechanism is provided to prevent the differential mechanism from performing differential operation. Due to the action of the mechanism that prevents this differential operation, the speed difference between the front and rear wheels is eliminated, and effective driving force is transmitted to either wheel.

By the way, when a four-wheel drive vehicle as described above travels on a road surface with a low coefficient of friction, each wheel may slip independently if the differential mechanism described above is in operation. As a countermeasure against such defects, if the coefficient of friction between the steered wheels and the road surface is below a predetermined value and the differential function between the front and rear wheels is not blocked, a system is installed to block the differential function. ``4-wheel drive vehicle'' that displays instructions (1987-)
155225) etc. have been proposed.

[Problems to be Solved by the Invention] This prior art slip control device for a four-wheel drive vehicle has the following problems.

That is, (1) While driving on a road surface with a low coefficient of friction, even if an instruction to disable the differential function between the front and rear wheels is displayed, the driver has to perform this operation. However, while driving on the above-mentioned road surface, the running stability and braking stability of the vehicle are reduced, making it difficult to drive.

In such a case, there is a problem in that if the driver performs a new operation according to the display, it becomes a burden on the driver and reduces the operability of the four-wheel drive vehicle.

(2) Conventionally, slip conditions have been determined by focusing only on the coefficient of friction between the front wheels, which are steering wheels, and the road surface. Therefore, if the rear wheels slip before the front wheels, there is a problem in that the slip cannot be suppressed.

(3) Furthermore, if you continue to drive for a long time with the differential function between the front and rear wheels disabled, the difference in rotational speed between the front and rear wheels will not be absorbed in a four-wheel drive vehicle, causing twisting in the power transmission system. Since the force is applied, there is a problem in that the tires wear out quickly and fuel efficiency decreases.

(4) As a countermeasure to the above (3), once the differential function is blocked, it may be configured such that the blocking of the differential function is canceled after a predetermined period of time has elapsed from that time. However, if the slip condition still continues at that point, there is a problem that sufficient slip control cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a slip control device for a four-wheel drive vehicle that appropriately controls blocking and activation of a differential function between front and rear wheels to suppress slip of four wheels.

RI51 MEANS FOR SOLVING THE PROBLEMS In order to solve the above-mentioned problems, the present invention adopts the configuration illustrated in FIG. 1. That is, as illustrated in FIG. 1, the present invention includes a differential means M1 having a differential function of absorbing the difference in rotational speed between front wheels and rear wheels rotated by driving force transmitted from an internal combustion engine. In the slip control device for a four-wheel drive vehicle, the differential means M1 is configured to activate or block the differential function according to an external command, and further includes front wheel rotational state detection means for detecting the rotational state of the front wheels. M
2, and rear wheel rotational state detection means M for detecting the rotational state of the rear wheel.
3, a slip determination means M4 for determining whether or not the front wheel or the rear wheel is in a slip state based on the detection results of the front wheel rotation state detection means M2 and the rear wheel rotation state detection means M3; a vehicle speed detection means M5 for detecting the speed of the four-wheel drive vehicle; a throttle valve opening detection means M6 for detecting the opening of the throttle valve 15 of the internal combustion engine; and detection of the detected throttle valve opening and the vehicle speed. steady running determining means M7 for determining whether or not the four-wheel drive vehicle is in a steady running state based on the vehicle speed detected by the means M5; a command to the differential means M1 to block the differential function when the steady running state is determined by the steady running determining means M7, and to activate the differential function when the steady running state is determined by the steady running determining means M7. The gist of the present invention is a slip control device for a four-wheel drive vehicle, characterized by comprising: a dynamic control means M8;

The differential means M1 prevents or activates a differential function that absorbs the difference in rotational speed between the front wheels and rear wheels of a four-wheel drive vehicle in accordance with an external command. For example, it may be constructed from a pair of small differential gears made of bevel gears, a pair of large differential gears, a multi-disc clutch that directly connects a drive shaft, and a drive device thereof.

Also, for example, a planetary gear and a sun gear of the planetary gear.

It can also be composed of a clutch that connects any two of a planetary gear and a ring gear, and a driving device thereof.

The front wheel rotation state detection means M2 detects the rotation state of the front wheels.

The rear wheel rotational state detection means M3 detects the rotational state of the rear wheel.

Here, the rotational state may be, for example, a rotational speed or rotational acceleration, or a rotational angle. Therefore, the double-dry state detecting means M2, M3 can also be constituted by, for example, an electromagnetic pickup, a proximity switch, a semiconductor Hall sensor, etc. provided close to the axle of the wheel.

Further, for example, a configuration may be adopted in which an optical sensor detects a lattice of a lattice disk disposed on an axle or a shaft interlocking with the axle.

The slip determining means M4 determines whether either of the two wheels is in a slip state based on the rotational state of the front wheels and the rear wheels. For example, the vehicle may be configured to determine that the vehicle is in a slipping state when the difference in rotational speed between the front wheels and the rear wheels is equal to or greater than a predetermined value. Alternatively, for example, the slip state may be determined based on the rotational speed of each of the front wheels or the rear wheels, and based on the ratio of deviation between this rotational speed and the vehicle body speed.

The vehicle speed detection means M5 is for detecting the vehicle speed of a four-wheel drive vehicle. For example, the rotation angle of the drive shaft per predetermined time may be measured, and the vehicle speed may be detected based on the measured value.

Throttle valve opening detection means M6 refers to internal combustion engine M1.
This detects the opening of the throttle valve. For example, the rotation amount of a member that rotates in conjunction with the throttle valve may be detected by a throttle position sensor having a plurality of contacts.

The steady running determination means M7 determines whether the four-wheel drive vehicle is in a steady running state based on the vehicle speed and the throttle valve opening. For example, if the change in the throttle valve opening within the predetermined opening determination time is less than the predetermined opening value, and the change in vehicle speed within the predetermined vehicle speed determination time is less than the predetermined vehicle speed value, the vehicle is in a steady running state. It may be configured to make a determination.

The differential control means M8 blocks the differential function when it is determined that the vehicle is in a slip state, and activates the differential function when it is determined that the vehicle is in a steady running state, respectively. This command is given to the differential means M1 that has been set.

The slip determining means M4, the steady running determining means M7, and the differential control means M8 may each be realized as independent discrete logical operation circuits. In addition, ROM mainly uses the well-known CPU.

It is configured as a logical operation circuit together with RAM and other peripheral circuit elements, and realizes each of the above means according to a predetermined processing procedure, determines whether the vehicle is slipping or steady running, and outputs a command to the differential means M1. There may be.

[Function] As illustrated in FIG. 1, the slip control device for a four-wheel drive vehicle of the present invention detects a slip state based on the detection results of the front wheel rotation state detection means M2 and the rear wheel rotation state detection means M3. If the slip determination means M4 determines that there is a slip, the differential control means M8 instructs the differential means M1 to block the differential function, and on the other hand, the detection results of the vehicle speed detection means M5 and the throttle valve opening detection means M6 When the steady running determining means M7 determines that the vehicle is in a steady running state based on the above, the differential control means M8 operates to instruct the differential means M1 to operate the differential function.

That is, if it is determined that the vehicle is in a slip state, slip control is started, and if it is determined that the vehicle is in a steady running state based on changes in vehicle speed and throttle valve opening, slip control is ended.

Therefore, the slip control device for a four-wheel drive vehicle of the present invention works to immediately activate the differential function and end the slip control when the vehicle enters a steady driving state, after starting the slip control that inhibits the differential function. . The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

FIG. 2 shows a system configuration of a slip control device for a four-wheel drive vehicle, which is an embodiment of the present invention. The output of the engine 1 is transmitted to the four-wheel drive transfer mechanism 3 via the automatic transmission 2, and then distributed to each wheel as driving force.

The automatic transmission 2 has a torque converter 4 with lockup.
and a transmission 5. The lock-up torque converter 4 has a lock-up clutch therein that engages the input shaft 4a and the output shaft 4b, and the lock-up clutch is activated by the lock-up control solenoid 6.
a and the output shaft 4b are engaged or separated. The output of the engine 1 is applied to the input shaft 4a from a crankshaft (not shown), and when the lock-up clutch is engaged by the operation of the lock-up control solenoid 6, the output shaft 4b
and is transmitted to the transmission 5.

The transmission 5 is a well-known mechanism equipped with planetary gears, and is configured to switch over a plurality of gears by operating a shift control solenoid 7.

The output of the transmission 5 is transmitted to the four-wheel drive transfer mechanism 3.

The four-wheel drive transfer mechanism 3 has a center differential 8 of a planetary gear type. The center differential 8 is composed of a carrier 9 that receives power from the transmission 5, a planetary pinion gear 10 carried by the carrier 9, and a sun gear 11 and a ring gear 12 meshed with the planetary pinion gear 10. .

The ring gear 12 is connected to a rear wheel drive shaft 13, and the sun gear 11 is connected to a sleeve-shaped front wheel drive intermediate shaft 14 concentric with the rear wheel drive shaft 13.

The four-wheel drive transfoot mechanism 3 is provided with a front wheel drive shaft 15 C) parallel to the front wheel drive intermediate shaft 14,
The front wheel drive intermediate shaft 14 and the front wheel drive shaft 15 are connected by an endless chain 18 that meshes with sprockets 16 and 17 disposed on each of them. Note that the distribution ratio of the driving force between the rear wheel drive shaft 13 and the front wheel drive shaft 15 is determined based on the ratio of the number of teeth between the sun gear 11 and the ring gear 12.

Four wheel drive transformer 7? The mechanism 3 includes a differential control clutch 1 that selectively engages the sun gear 11 and the ring gear 12.
9 is disposed, and the differential control clutch 19 is configured to be engaged or disengaged by the action of a differential control solenoid 2o.

One end side of a rear propeller shaft 22 is connected to the rear wheel drive shaft 13 via a universal joint 21, and the other end side of the rear propeller shaft 22 is similarly connected to the universal joint 23.
Driving force is transmitted to the rear wheels 24 via a rear wheel differential (not shown).

On the other hand, one end of a front propeller shaft 26 is connected to the front wheel drive shaft 15 via a universal joint 25, and the other end of the front propeller shaft 26 is similarly connected to the universal joint 2.
7, and the driving force is transmitted to the front wheels 28 via a front wheel differential (not shown).

Since the driving force transmission mechanism is configured as shown below,
It works as follows. That is, when the differential control clutch 19 is not engaged due to the action of the differential control lens 20 described above, the center differential 8 performs the operating function, and the output of the engine 1 is transmitted to the four wheels via the automatic transmission 2. Rear wheel 24 and front wheel 2 from drive transfer mechanism 3
8 as a driving force. The distribution ratio of the driving force is determined according to the ratio of the number of teeth between the Zang gear 11 and the ring gear 12. On the other hand, when the differential control clutch 19 is engaged due to the action of the differential control solenoid 20, the center differential 8 is directly connected.
The output of engine 1 is 50% each for rear wheels 24 and front wheels 28.
will be distributed evenly and transmitted. In this case, the center differential 8 is in a state where its differential function is blocked, and the rear wheels 24 and front wheels 28 are each directly coupled and driven.

This system is also provided with hydraulic pressure switching solenoids 29a and 29b for preventing acceleration slippage by communicating and cutting off a brake hydraulic circuit (not shown).

This system uses a vehicle speed sensor 30 as a detector, which detects the vehicle speed by measuring the rotational speed of the rear wheel drive shaft 13.
It has a throttle position sensor 31 that detects the opening degree of the throttle valve of the engine 1, and a neutral start switch 32 that detects the shift position. The signals of each sensor and switch mentioned above are controlled by the electronic control unit for speed change control (
(hereinafter simply referred to as TECLI) 40, and the corresponding TEC
U40 drives and controls the lock-up control solenoid 6, shift control solenoid 7, and differential control solenoid 20 described above.

In addition, this system includes other detectors such as a left front wheel rotation speed sensor 51 that detects the rotation speed of the left front wheel, a right front wheel rotation speed sensor 52 that detects the rotation speed of the right front wheel, and a rear wheel rotation speed sensor 52 that detects the rotation speed of the rear wheel. A wheel rotation speed sensor 53 is provided.

The above-mentioned signals of sen 1 and no are input to an electronic control unit for acceleration slip control (hereinafter simply referred to as 5ECU) 60, and
The ECU 60 has the above-mentioned hydraulic pressure switching solenoids 29a and 2.
9b is driven and controlled.

Next, the configurations of the TECU 40 and 5ECLI 60 will be explained based on FIG. 3.

The TECLJ40 inputs and calculates each data detected by each sensor and switch described above according to a control program, and also includes a CPU 40a that performs processing for controlling each device described above, and the control program and initial data are stored in advance. Stored ROM40b, T
It is configured as a logic operation circuit centered around a RAM 40c that temporarily stores various data input to the ECU 40 and data necessary for engine control, and is connected to an input/output port 40e and an output port 40f via a common bus 40d. to perform external input/output.

The TECU 40 includes the neutral start switch 32 and the buffer 4 of the throttle position sensor 31 described above.
0q, 40h, and a waveform shaping circuit 401 that shapes the waveforms of the output signals of the vehicle speed sensor 30.
Data transferred via the data bus 55 that transfers data to and from the J60 and output signals from each of the above sensors are input to the CPU 40a via the input/output port 40e, and the CPU 40a receives the data via the input/output port 40e. Data is output to the data bus 55.

In addition, the TECt 140 includes 40 m in the drive circuits 40j and 40 that supply drive current to the lock-up control solenoid 6, the shift control solenoid 7, and the differential control solenoid 20, and the CPU 40a is The drive circuit 40j.

40, a control signal is output to 40m.

On the other hand, 5ECtJ60 is the CPU 60a as well.

It is configured as a logic operation circuit centering on the ROM 60b and RAM 60c, and is connected to the input/output port 0f and the output port 0C via the common bus 60e to perform input/output with the outside.

The 5ECU 60 includes a waveform shaping circuit 60i that shapes the waveforms of the buffer 760h of the throttle position sensor 31 and the output signals of the vehicle speed sensor 30, the left front wheel rotational speed sensor 51, the right front wheel rotational speed sensor 52, and the rear wheel rotational speed sensor 53. The data transferred by the data bus 55 that transfers data between the TECU 40 and the output signals from the above-mentioned sensors are input to the CPU 40a via the input/output capotro 0f, and the CPU 40a - Output data to the data bus 55 via the trolley 0f.

The 5ECU 60 also includes a drive circuit 60 that supplies drive current to the hydraulic pressure switching control solenoids 29a and 29b described above.
The CPU 60a is connected to the drive circuit 60j via the output port 0Q.

A control signal is output to 60k. Note that the 5ECtJ60 also includes a self-running timer 60m that generates an interrupt to the CPU 60a after a set time has elapsed.

Next, the processing executed by the TECU 40 and the 5ECU 60 will be explained based on the flowcharts shown in FIGS. 4 and 5.

First, the slip control wJ process executed by the 5ECU 60 will be explained based on the flowchart shown in FIG.

This slip control process is repeatedly executed every 20 [m5ec] as the four-wheel drive vehicle travels after the 5ECU 60 is activated. In addition, with the execution of this slip control process, each rotation speed Vfl, Vfr, Vr of the left front wheel, right front wheel, and rear wheel is determined by a wheel rotation speed calculation process (not shown) based on the output signal of the rotation speed sensor of each wheel. It has been calculated.

Also, by the throttle valve opening calculation process (not shown), the throttle position sensor 3 is
〇 is calculated from 1 to the detected throttle valve opening change value. Furthermore, a change value ΔV of the vehicle speed calculated based on the detected value of the vehicle speed sensor 30 at a predetermined time interval is calculated by a vehicle speed calculation process (not shown).

In step 100, the left front wheel rotation speed Vfl and the right front wheel rotation speed Vfr are calculated by the wheel rotation speed calculation process.
, the rear wheel rotational speed V', the throttle valve opening change value Δθ calculated by the throttle valve opening calculation process, and the vehicle speed change value ΔV calculated by the vehicle speed calculation process, are stored in RAM.
A process of reading from a predetermined area of 60G is performed.

In the following step 102, the difference between the average value of the left front wheel rotational speed ■fl and the right front wheel rotational speed ■fr and the rear wheel rotational speed vr is calculated as in the following equation (1), and the front and rear wheel difference DV1 is calculated. Processing is performed.

DV1 = l Vr - (Vfr + Vfl) / 21 - (
1) Next, in step 104, the difference between the left front wheel rotational speed Vfl and the right front wheel rotational speed Vfr is calculated as shown in the following equation (2), and a process is performed to calculate the left and right wheel difference DV2.

DV2= l Vfr-Vfl l =
・(2>Next, proceed to step 106 and repeat step 10 above)
The front and rear wheel difference DVI calculated in step 2 is the front and rear wheel difference reference value VT1.
A determination is made as to whether or not it exceeds . If it is determined that the front and rear wheel difference DV1 exceeds the front and rear wheel difference reference value VT1, it is assumed that one of the front and rear wheels has fallen into a slip state, and the process proceeds to step 108. In step 108, the front and rear wheel difference flag FFR is set to the value 1, and then the process proceeds to step 110. On the other hand, if it is determined in step 106 that the front and rear wheel difference DV1 is equal to or less than the front and rear wheel difference reference value VT1, the process proceeds to step 110.

In step 110, it is determined whether the left and right wheel difference DV2 calculated in step '104 exceeds the left and right wheel difference reference value VT2. Left and right wheel difference D V 21r; If it is determined that the difference exceeds the left and right wheel difference reference value VT2, it is assumed that either the left front wheel or the right front wheel is in a slip state, and the process proceeds to step 112. In step 112, the left and right wheel difference flag FLR is set to the value 1, and then the process proceeds to step 114. On the other hand, if it is determined in step 110 that the left and right wheel difference DV2 is less than the left and right wheel difference reference value VT2T2, the process proceeds to step 114.

In step 114, the throttle valve opening change value Δθ read in step 100 is set to the opening change reference value by 1.
A determination is made as to whether it is less than or equal to the maximum value. If it is determined that the throttle valve opening change value Δθ is less than the opening change reference value by 1, the process proceeds to step 116. Step 1
In step 16, the opening counter NTI-( is incremented by 1, and then the process proceeds to step 120. On the other hand, if in step 114, the throttle valve opening change value Δθ is greater than or equal to the opening change reference value by 1, If it is determined, the process proceeds to step 118. In step 118, the opening counter N
After the process of resetting TH to the value O is performed, the process proceeds to step 120. In step 120, it is determined whether the value of the opening counter NTl-1 exceeds the stability reference value by 2 or not.

If it is determined that the value of the opening counter N T +-1 has been sufficiently added to exceed the stable reference value by 2, step 12
Proceed to step 2. In step 122, the throttle valve opening stability determination flag FIT is set to the value 1, and then the process proceeds to step 126.

On the other hand, if it is determined in step 120 that the value of the opening counter NTH is less than the stability reference value by 2 due to insufficient addition, the process proceeds to step 124. Step 1
In step 24, the throttle valve opening stability determination flag FIT is reset to the value O, and then step 12
Proceed to step 6.

In step 126, it is determined whether the vehicle speed change value Δ■ read in step 100 is less than 3 of the vehicle speed change reference value. If it is determined that the vehicle speed change value ΔV is less than the vehicle speed change reference value 3, step 128
Proceed to. In step 128, the vehicle speed counter NV is set to 1 (
After the brightening process is performed, the process advances to step 132. On the other hand, if it is determined in step 126 that the vehicle speed change value ΔV is 3 or more than the vehicle speed change reference value, the process proceeds to step 130. At step 130, the vehicle speed counter NV
After the process of resetting the value O to the value O, step 1
Proceed to step 32. In step 132, the vehicle speed counter N
A determination is made as to whether or not the value of V exceeds a steady reference value (Ii'iK 4). If it is determined that the value of the vehicle speed counter NV has been sufficiently added to exceed the steady reference value of 4, the process proceeds to step 134. .

In step 134, the steady vehicle speed flag FIV is set to the value 1, and then the process proceeds to step 1138. On the other hand, if it is determined in step 132 that the value of the vehicle speed counter NV is still 4 or less than the steady reference value due to insufficient addition, the process proceeds to step 136. Step 136
After a process of resetting the steady vehicle speed flag FIV to the value O is performed, the process proceeds to step 138.

In step 138, it is determined whether the throttle valve opening stability determination flag FIT is set to the value 1 or not. Throttle valve opening stability determination flag FIT
If it is determined that the value 1 is set to 1~, it is determined that the operation of the throttle valve is stable and no rapid acceleration or deceleration is performed, and the process proceeds to step 140. In step 140, it is determined whether the steady vehicle speed flag FIV is set to the value 1 or not. Vehicle speed steady flag F
If it is determined that IV is set to the value 1,
It is determined that the running state is steady, and the process proceeds to step 142. In step 142, processing is performed to reset the front and rear wheel difference flag FFR to the value O, assuming that the slip condition has converged. In the following step 144, the left and right wheel difference flag FLR is similarly reset to the value O, assuming that the slip has converged, and then the process proceeds to step 146. On the other hand, if it is determined in the above step 138 that the throttle valve opening stability determination flag FIT is not set to the value 1, or if it is determined that the vehicle speed steady flag FIV is not set to the value 1 in the above step 140. If so, the process proceeds to step 146 assuming that the running state is not steady and is still in a slipping state.

In step 146, it is determined whether the left and right wheel difference flag FLR is set to the value 1. Left and right wheel difference flag F
If it is determined that LR is set to the value 1, that is, if either the left or right front wheel is in a slip state, the process advances to step 148. In step 148,
After the process of setting the differential control flag FDL to the value 1 is performed, the main slip control process is completed by processing 1 to rNEX'TJ. On the other hand, if it is determined that the left and right wheel difference flag FLR is not set to the value 1, that is, if neither the left nor right front wheels are in a slip state, the process proceeds from step 146 to step 150. Step 15
0, it is determined whether the front and rear wheel difference flag FFR is set to the value 1 or not.

If it is determined that the front and rear wheel difference flag FFR is set to the value 1, that is, if either the front or rear wheels are in a slip state, the process proceeds to step 148 described above and the differential control flag FDL is set. Shun set to value 1, rNEX
It can be handled to TJ and this process ends. On the other hand, if it is determined that the front and rear wheel difference flag FFR is not set to the value 1,
That is, if neither the front nor the rear wheels are in a slip state, the process proceeds from step 150 to step 152 described above. In step 152, the differential control flag FDL is reset to the value O, and then rNEXTJ is processed and the process ends. Note that from now on, this process will be performed for 20 [m
It is executed repeatedly every 5ec].

Next, the differential control processing executed by the TECU 40 will be explained based on the flowchart shown in FIG. This differential control process is repeatedly executed at predetermined time intervals in conjunction with the slip control process described above.

In step 200, a process is performed in which the value of the differential control flag FDL set by the slip control process described above is read from the 5ECU 60 into the TECtJ40. In subsequent step 205, it is determined whether the value of the differential control flag FDL read in step 200 is set to 1 or not. If it is determined that the differential control flag FDL is set to the value 1, that is, if one of the wheels is in a slip state, step 21 is performed.
Proceed to step 5. In step 215, the differential control solenoid 20
A process of energizing is performed. Through this process, the differential control clutch 19 engages the sun gear 11 and the ring gear 12, so that the center differential 8 is in a state where its differential function is blocked, so that the rear wheels 24 and the front wheels 28 are directly coupled and driven. After that, it can be handled to rNEXTJ and the main differential control process ends.

On the other hand, if it is determined that the differential control flag FDL is not set to the value 1, that is, if none of the wheels are in a slip state, the process proceeds to step 210. In step 210, a process is performed to stop energizing the differential control solenoid 20. As a result of this process, differential control clutch 19 separates sun gear 11 and ring gear 12, center differential 8 operates to perform a differential function, and rear wheels 24 and front wheels 28 are driven independently. Thereafter, the main differential control process is terminated by moving to rNEXTJ. Thereafter, the main differential braking process 1aIl is repeatedly executed in conjunction with the slip control process described above.

Next, an example of the control state of the slip control process and the differential control process described above is shown in FIG.
The explanation will be based on.

At time t1 while the four-wheel drive vehicle is running, a slip occurs, and the front and rear wheel difference DV1 between the average rotational speed of the left and right front wheels and the rear wheel rotational speed exceeds the front and rear wheel difference reference value VT1. Therefore, at the same time t1, the front and rear wheel difference flag FFR is set to the value 1, and the differential control flag FDL is also set to the value 1. As a result, energization of the differential control solenoid 20 is started at the same time t1, and as soon as a predetermined solenoid activation time has elapsed, the differential function of the center differential 8 is blocked and the front wheels and rear wheels are directly connected. By directly connecting the front and rear wheels, the difference in rotational speed between the front and rear wheels is reduced, and at time t
2, the front and rear wheel difference DV1 is less than the front and rear wheel difference reference value VTI.

On the other hand, at time t3, slip occurs in either the left front wheel or the right front wheel, and the left and right wheel difference DV2 exceeds the left and right wheel difference reference value VT2. Therefore, at the same time t3,
The left and right wheel difference flag FLR is set to the value 1. Note that since the differential control flag FDL has already been set to the value 1, this state is maintained. Since the front and rear wheels continue to be directly connected, the left and right wheel difference DV2 decreases, and at time t4, the left and right wheel difference DV2 becomes equal to or less than the left and right wheel difference reference value VT2.

Thereafter, since the slip state is suppressed, the four-wheel drive vehicle shifts to a smooth running state. Therefore, from around time t5, the throttle valve opening degree θ becomes almost constant, and the throttle valve opening degree change value Δθ becomes less than 1 from the opening degree change reference value, and the value of the opening degree counter NTH is added to it, and gradually increases. Eventually, at time t7, the value of the opening counter NTH exceeds the stability reference value of 2, so at the same time t7, the throttle valve opening stability determination flag FIT is set to the value 1. However, the value of the steady vehicle speed flag FIV is O.
Therefore, front and rear wheel difference flag FFR, left and right wheel difference flag FLR
1 differential control flag FDL is maintained at the value 1.

On the other hand, from around time t6, the vehicle speed ■ becomes almost constant, and the vehicle speed change value Δ■ becomes less than 3 than the vehicle speed change reference value, and the value of the vehicle speed counter NV is added to it, and gradually increases. Eventually time t
At time t8, the value of the vehicle speed counter NV exceeds the steady reference value of 4, so at the same time t8, the steady vehicle speed flag FIV is set to the value 1. At the same time t8, the throttle valve opening stability determination flag FIT is also set to the value 1, so it is determined that the four-wheel drive vehicle has entered the steady running state, and the front and rear wheel difference flag FFR and the left and right wheel difference flag FFR are set to 1. Both the flags FLR are reset to the value O, and the differential control flag FDL is also reset to the value O. Therefore, at the same time t8, the power supply to the differential control solenoid 20 is stopped, and after a predetermined solenoid activation time has elapsed, the center differential 8 comes to perform the differential function, so that the front wheels and the rear wheels are driven independently again. be done. Thereafter, if either the front and rear wheel difference flag FFR or the left and right wheel difference flag FLR is set to the value 1, the differential control flag F
If DL is set to the value 1 to directly connect the front and rear wheels, and on the other hand, both the steady vehicle speed flag FIV and the throttle valve opening stable determination flag FIT are set to the value 1, the difference between the front and rear wheels Flag FFR1 Left and right wheel difference flag F
In LR1, the differential control flag FDL is reset to the value O, and the control for independently driving the front wheels and the rear wheels is repeated.

In this embodiment, the four-wheel drive transformer 71m structure 3 serves as the differential means M1, the left front wheel rotation speed sensor 51, the right front wheel rotation speed sensor 52, and the 5ECU 60 serve as the front wheel rotation state detection means M2, and the rear wheel rotation speed Sensor 53 and 5ECU60
correspond to the rear wheel rotation state detection means M3. Also, 5
Processes executed by the ECtJ60 and the 5ECU60 (steps 102, 104, 106, 108, 110
112) functions as slip determination means M4, vehicle speed sensor 30 and 5ECU60 correspond to vehicle speed detection means M5, and throttle position sensor 31 and 5ECU60 correspond to throttle valve trace detection means M6. Furthermore, the processes executed by the 5ECU60 and the 5ECLJ60 (steps 114, 116, 118, 120, 1
22,124°126.128,130,132,13
4,136.138,140,142,144> is the steady running determination means M7, and the 5ECU60 and the 5EC
Processing performed by U60 (steps 146 and 148)
, 150, 152> and TECU40 and the TECtJ
40 (steps 205, 210,
215) respectively function as differential control means M8.

As explained above, in this embodiment, based on the detection results of the left front wheel rotation speed sensor 51, the right front wheel rotation speed sensor 52, and the rear wheel rotation speed sensor 53, the front and rear wheel difference DVI exceeds the front and rear wheel difference reference value VT1. If it exceeds the left or right front wheel difference D
If V2 exceeds the value VT2, it is determined that the four-wheel drive is in a slip state, and the differential function of the center differential 8 is blocked and the front and rear wheels are directly connected. On the other hand, the condition in which the throttle valve opening degree change value 〇 is less than the opening degree change reference value continues for a predetermined period of time, and the vehicle speed change value ΔV is less than the vehicle speed change reference value by 3 is the predetermined state. If the four-wheel drive vehicle continues for a certain period of time, it is determined that the four-wheel drive vehicle has entered a steady running state, and the center differential 8 is configured to perform a differential function to drive the front wheels and rear wheels independently. Therefore, even if the four-wheel drive vehicle falls into a slipping state, the slipping state can be suppressed without requiring any special operation by the driver, and driving stability and braking stability can be improved.

In addition, only when the throttle valve opening change value Δθ within a predetermined time is less than the opening change reference value by 1, and the vehicle speed change value ΔV is less than the vehicle speed change reference value by 3, the four-wheel drive vehicle is in a steady state. It is determined that the vehicle is in a running state and the slip control is terminated. For this reason, slip control is continued when the vehicle is in a slip state, and is immediately terminated when the vehicle enters a steady state, so that the state in which the front wheels and rear wheels are directly connected is the minimum necessary time. It does not put unnecessary stress on the power transmission system or tires, and it is possible to achieve both the durability and slip control performance of four-wheel drive vehicles.

Furthermore, as the state in which the front and rear wheels are directly connected as described above is the minimum necessary, the state in which the driving force is distributed to the four wheels and runs smoothly, which is unique to four-wheel drive vehicles, becomes longer. Since the output of engine 1 is less likely to be wasted,
Slip control that maintains good fuel efficiency becomes possible.

In addition, the rental differential 7 that is pre-installed on four-wheel drive vehicles
Since slip control is performed using the lential 8 and the differential control clutch 19, slip control can be achieved with a cylinder configuration.

Furthermore, since slip judgment is performed based on both the front and rear wheel difference DV1 and the left and right wheel difference DV2, slip control can be started or continued even if one of the four wheels is in a slip state. becomes possible. This is particularly effective when driving on muddy or snowy roads.

Further, since slip control is performed by directly connecting the front wheels and the rear wheels, there is an advantage that slip control can be performed even if, for example, an abnormality occurs in a dedicated slip prevention brake system.

In this embodiment, the slip control is performed using the TECU 40 and the 5ECU 60, but it is also possible to perform the slip control using one ECU, for example.

Furthermore, although this embodiment performs slip control by directly connecting the front and rear wheels without using an existing acceleration slip control device, for example, it is possible to combine the control of an existing acceleration slip control device with the slip control of this embodiment. It can also be configured to do so. When configured in this way, the control accuracy of slip control is improved, and more rapid slip control becomes possible.

Note that in this embodiment, the left-right wheel difference DV2 is detected only from the front wheels, but it may be configured to detect the left-right wheel difference of the rear wheels as well. With this configuration as well, the control accuracy of slip control is improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention. be.

As described in detail above, the slip control device for a four-wheel drive vehicle of the present invention determines whether the vehicle is in a slip state based on the detection results of the front wheel rotation state detection means and the rear wheel rotation state detection means. If it is determined by the means, the differential control means instructs the differential means to block the differential function, and on the other hand, based on the detection results of the vehicle speed detection means and the throttle valve distance detection means, the vehicle is in a steady running state. When the steady running determination means determines that, the differential control means is configured to instruct the differential means to operate the differential function. Therefore, even in driving conditions where the running stability and braking stability of the vehicle deteriorate, such as when entering a road surface with a low coefficient of road friction, slip conditions can be suppressed without burdening the driver with special operations. Therefore, it is possible to improve the safety of vehicle running.

Furthermore, since the slip state is determined based on the rotational states of the front wheels and the rear wheels, if any one of the four wheels is in a slip state, the slip state can be reliably detected.

Furthermore, slip control is terminated after determining the steady running state based on the vehicle speed and throttle valve opening.
Since the slip control is continued while the vehicle is in the slip state, it is possible to perform the optimum slip control according to the driving state of the four-wheel drive vehicle.

For example, if the steady running determination means detects that the change in the throttle valve opening detected by the throttle valve opening detection means within a predetermined opening determination time is less than a predetermined opening value, and the vehicle speed detection means detects If the four-wheel drive vehicle is configured to be determined to be in a steady running state when a change in the detected vehicle speed within a predetermined determination time is less than a predetermined vehicle speed value, the accuracy of determining the steady running state is improved. There is also the advantage that the control accuracy of slip control is also improved.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram conceptually illustrating the content of the present invention, Fig. 2 is a system configuration diagram of an embodiment of the invention, and Fig. 3 is a block diagram for explaining the configuration of the electronic control device. 4 and 5 are flowcharts showing the processing executed by the electronic control unit in one embodiment of the present invention, and FIG. 6 is a timing chart showing the state of the control. Ml... Differential means M2... Front wheel rotation state detection means M3... Contact wheel rotation state detection means M4... Slip determination means M5... Vehicle speed detection means M6... Throttle valve opening detection means M7...Steady running determination means M8...Differential control means 1...Engine 3...Four-wheel drive transformer mechanism 8...Center differential 7 ratio cell 19...Differential control clutch 20. ... Differential control solenoid 24 ... Rear wheel 28 ... Front wheel 30 ... Vehicle speed sensor 31 ... Throttle position sensor 40 ... Electronic control unit for speed change control (TECU>51 ... Left Front wheel rotation speed sensor 52...Right front wheel rotation speed sensor 53...Rear wheel rotation speed sensor 60...Electronic control device for acceleration slip control (SECL)
I>

Claims (1)

[Claims] 1. Slip control device for a four-wheel drive vehicle equipped with a differential means having a differential function to absorb the difference in rotational speed between front wheels and rear wheels rotated by driving force transmitted from an internal combustion engine. , the differential means is configured to activate or inhibit the differential function according to an external command, and further includes front wheel rotation state detection means for detecting the rotation state of the front wheels; and front wheel rotation state detection means for detecting the rotation state of the rear wheels. and a slip determination that determines whether the front wheel or the rear wheel is in a slip state based on the detection results of the front wheel rotation state detection means and the rear wheel rotation state detection means. means, vehicle speed detection means for detecting the speed of the four-wheel drive vehicle, throttle valve opening detection means for detecting the opening of the throttle valve of the internal combustion engine, and detection of the detected throttle valve opening and the vehicle speed. steady running determining means for determining whether or not the four-wheel drive vehicle is in a steady running state based on the vehicle speed detected by the means; differential control means for commanding each of the differential means to block the differential function, and to activate the differential function when the steady running state is determined by the steady running determining means; A slip control device for a four-wheel drive vehicle, characterized by comprising: 2. The steady running determination means determines that the change in the throttle valve opening detected by the throttle valve opening detection means within a predetermined opening determination time is less than a predetermined opening value, and that the throttle valve opening detected by the vehicle speed detection means The four-wheel drive vehicle according to claim 1, wherein the four-wheel drive vehicle is configured to determine that the four-wheel drive vehicle is in a steady running state when a change in vehicle speed within a predetermined vehicle speed determination time is less than a predetermined vehicle speed value. Car slip control device.