JPH055689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a driving force distribution control device for a four-wheel drive vehicle that controls the distribution of driving force to front and rear wheels according to predetermined control conditions.

(Prior Art) As a conventional drive force distribution control device for a four-wheel drive vehicle, a device as described in, for example, Japanese Patent Laid-Open No. 57-80926 is known.

This conventional device includes means for detecting the rotation speed of the front wheels, means for detecting the rotation speed of the rear wheels, means for comparing the detection results of both detection means, and switching of four-wheel drive based on the comparison results from the comparison means. The vehicle was equipped with an instruction means for instructing a changeover from two-wheel drive to four-wheel drive when the difference in rotational speed between the front adjacent wheel and the rear wheel exceeded a predetermined value.

(Problems to be Solved by the Invention) However, in such a conventional driving force distribution control device, the rotation speed detection means may output a false detection value, or one of the detection means may be inoperable. This would instruct the driver to switch from two-wheel drive to four-wheel drive even if the difference in rotational speed between the front and rear wheels exceeds a predetermined value. Even if it is preferable to
The vehicle remains in a four-wheel drive state in which the driving force is equally distributed between the front and rear wheels, and a large load is constantly applied to the power train system that transmits the driving force, and tight corner braking occurs due to the direct drive connection. There was a problem that

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention employs the following solving means. did.

The solution of the present invention will be explained with reference to the conceptual diagram of the claims shown in FIG. ,
Rotation signals from rotation sensors 5 and 6 provided in each of the front and rear wheel drive force transmission systems are input, and the actuator 4 is actuated based on the rotation signals.
A driving force distribution control device for a four-wheel drive vehicle, comprising: a control means 7 for outputting a control signal to a four-wheel drive vehicle; When a rotation signal indicating an abnormality is input to 8, the control means 7 outputs a control signal to put the actuator 4 into a two-wheel drive state.

(Function) Therefore, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, by using the above-mentioned means, when the rotation sensor outputs a signal indicating an abnormality due to a failure, the transfer It is possible to cancel the driving force distribution control in the four-wheel drive direction to A and fix the two-wheel drive state.

In this way, when the rotation sensor fails, 2
By setting the vehicle to a wheel drive state, regardless of whether it is normal or abnormal, a large load is constantly applied to the powertrain system, such as when controlling the drive force distribution based on rotation signals, and tight corner braking phenomena can be avoided. never occurs.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.
In describing this embodiment, a driving force distribution control device for a four-wheel drive vehicle based on rear wheel drive will be taken as an example.

First, the configuration of the embodiment shown in FIGS. 2 to 5 will be explained.

Reference numeral 10 denotes a driving force distribution device, which, as shown in FIG.
2, input shaft 13, rear wheel drive shaft 14, multi-plate friction clutch 15, oil pump 16, pressure oil discharge pipe 1
7, an oil suction pipe 18, a reserve tank 19, a gear train 20, and a front wheel drive shaft 21.

The drive input shaft 11 is a shaft to which the driving force that has passed through the engine and clutch is input.

The transmission 12 changes the rotational driving force from the drive input shaft 11 according to a gear position selected by a shift operation, and in the embodiment, gear sets with different gear ratios are mounted on two parallel shafts. I am using a type with a .

The input shaft 13 is connected to the transmission 12 to a multi-plate friction clutch 15 as a transfer.
This is the shaft to which the rotational driving force is input.

The rear wheel drive shaft 14 is coaxially and directly connected to the input shaft 13, and the rotational driving force from the input shaft 13 is directly transmitted thereto.

The multi-plate friction clutch 15 is a clutch that can change the driving force transmitted to the front wheels by the clutch engagement pressure, and includes a clutch drum 15a fixed to the input shaft 13 and the rear wheel drive shaft 14, and a clutch drum 15a fixed to the input shaft 13 and the rear wheel drive shaft 14. A friction plate 15b rotationally engaged with the input shaft 15a, a clutch hub 15c rotatably supported on the outer circumference of the input shaft 13, and a friction disk 15d rotationally engaged with the clutch hub 15c. Friction plate 15b and friction disk 1 arranged in
Clutch piston 1 provided on one end side with 5d
5e, and a cylinder chamber 1 formed between the clutch piston 15e and the clutch drum 15a.
5f.

The oil pump 16 is a pump that sucks oil in the reserve tank 19 through an oil suction pipe 18, pressurizes it, and supplies it to a pressure oil discharge pipe 17, which is communicated with the cylinder chamber 15f, When pressurized oil is supplied from the oil pump 16, clutch engagement pressure is applied to the clutch piston 15e to bring the friction plate 15b and friction disk 15d into pressure contact, thereby transmitting the driving force from the input shaft 13 to the front wheels. let

The gear train 20 includes the clutch hub 1
5c, a second gear 20c provided on the intermediate shaft 20b, and a third gear 20d provided on the front wheel drive shaft 21. This is a means of transmitting driving force to the front wheels by tightening the wheels.

The front wheel side drive shaft 21 is a shaft that transmits rotational driving force to the front wheels of the vehicle.

Incidentally, FIG. 3 shows a specific example of a transfer case, in which the multi-disc friction clutch 15, gears, and shafts are housed in a transfer case 22.

In Fig. 3, 15g is a dish plate, 23 is a return spring, 24 is a control pressure oil input port,
25 is a control pressure oil path, 26 is a rear wheel side output shaft, 27 is a lubricating oil path, 28 is a speedometer pinion,
29 is an oil seal, 30 is a bearing, 31 is a needle bearing, 32 is a thrust bearing, and 33 is a joint flange.

40 is a driving force distribution control device, which includes a vehicle speed sensor 50, a front wheel rotation sensor 41, a rear wheel rotation sensor 42, an ignition switch 43, a proportional constant setting means 44, a control unit 45, a valve solenoid 46, an electromagnetic proportional A control relief valve 47 and a branch drain oil passage 48 are provided.

The vehicle speed sensor 50 detects the vehicle speed and outputs a vehicle speed signal v
This is a sensor that outputs , and is provided in the speedometer pinion 28 or the like.

Front wheel rotation sensor 41 and rear wheel rotation sensor 4
2 are provided in the middle of the front wheel drive shaft 21 and the rear wheel drive shaft 14, respectively, and rotate by a rotary plate fixed to the shaft and a phototube and a photoelectric element arranged in the holes of the rotary plate. A sensor or the like is used, and both rotation sensors 41 and 42 output rotation signals nf and nr in the form of pulse signals corresponding to shaft rotation.

The ignition switch 43 is closed by inserting a key into the key cylinder and rotating it to the engine starting position, and outputs an ON signal i.

The proportional constant setting means 44 is provided so that the difference in rotational speed ΔN between the front and rear wheels is influenced by the operating conditions of the driver, the road surface friction coefficient, etc., and can be adapted to these influencing factors. be.

As shown in Fig. 5, the torque transmitted to the front wheels ΔT is expressed as a function of the rotational speed difference ΔN as shown in the following equation, and by changing the proportionality constant K,
The relationship between the transmission torque ΔT and the rotational speed difference ΔN can also be changed.

ΔT=K・func(ΔN)K: proportional constant Specifically, the proportional constant setting means 44 may be one that can be set appropriately by the driver using a manual dial switch, etc., or a road surface friction coefficient sensor, etc. The proportionality constant K may be automatically changed using the following method.

The control unit 45 controls the vehicle speed signal v from the vehicle speed sensor 50 and the rotation sensor 4.
1 and 42, the ON signal i from the ignition switch 43, and the proportional constant signal k from the proportional constant setting means 44, basically the drive shafts 21 and 14 of the front and rear wheels are input. Rotational speed difference ΔN (Nr
-Nf) and outputs a control signal c to the valve solenoid 46 that brings the driving force distribution closer to the four-wheel drive state as the rotational speed difference ΔN increases. circuit 451,
452, clock circuit 453, RAM454,
ROM455, CPU456, control signal generation circuit 4
It is equipped with 57.

Count circuits 451 and 452 receive rotation signals nf and 452 input from rotation sensors 41 and 42, respectively.
This circuit converts nr into a digital signal and makes it a signal that can be processed by the CPU 456.

The clock circuit 453 is a circuit for giving time instructions and causing the CPU 456 to perform arithmetic processing at predetermined time intervals.

The above RAM 454 (random access memory) is a memory that can be written to and read from.
The RAM 454 is a circuit that specifically stores the count numbers of the rotation signals nf and nr that are input while the CPU 456 is performing arithmetic processing.

The above ROM455 (read-only memory) is a read-only memory.
As shown in the solid line in Figure 5, the rotational speed difference ΔN
The basic relationship between ΔT and the torque transmitted to the front wheels is stored in advance in the form of a table, and the CPU 4
After the rotational speed difference ΔN (ΔN=Nr−Nf) is calculated in step 56, a table search is performed. Also,
This ROM 455 contains respective calculated vehicle speeds Vf ^* , which correspond to the front wheel rotation speed Nf, the rear wheel rotation speed Nr, the final reduction ratio, and the wheel circumferential speed based on the wheel outer diameter.
The calculation formula for Vr ^* and the error vehicle speed ΔVf, ΔVr between the calculated vehicle speed Vf ^* , Vr ^* and the actual vehicle speed V based on the vehicle speed signal v.
The calculation formula (ΔVf=Vf ^* −V, ΔVr=Vr ^* −V),
Set value A is the allowable error value for these error vehicle speeds ΔVf and ΔVr (a value that cannot occur in normal slips is set; for example, A is set to 20
Kg/h) and the abnormality determination calculation formula ΔVfr=ΔVf−ΔVr for the vehicle speed sensor 50 are stored, and in the embodiment, the vehicle speed sensor 50 and both rotation sensors 41 and 42 are used as abnormality detection means, ΔVf>A, ΔVr
>A is detected (including the case where the vehicle speed sensor 50 is abnormal).

The CPU 456 (central processing unit) is a central processing unit that performs arithmetic processing.
Calculation of ΔVr, calculation of rotation speed difference ΔN between front and rear wheels,
Reads data from the RAM 454 and ROM 455, and sends the resulting signal to the control signal generation circuit 455.
Output to 7.

The control signal generation circuit 457 provides control to the CPU 4 for the valve solenoid 46 which is an actuator.
This circuit outputs a control signal c according to the result signal from 56.

The valve solenoid 46 is connected to the pressure oil discharge pipe 17
An actuator that drives an electromagnetic proportional control relief valve 47 provided in the middle of a branch drain oil passage 48 branched from the reserve tank 19 to the reserve tank 19.
If there is no output of control signal c, check oil line 4.
The relief valve 47 opens with the hydraulic pressure from 9,
The clutch is in the open state, but when the control signal c is output, the relief valve 47 moves in the closing direction, and the discharge pressure from the oil pump 16 is set to the oil pressure according to the control signal c. Incidentally, the clutch engagement pressure P is expressed by the following equation.

P=ΔT/(μ・S・2n・Rm) μ: Coefficient of friction of clutch plate S: Area of pressure acting on piston n: Number of friction discs
Rm: Torque transmission effective radius of friction disk Next, the operation of the embodiment will be explained.

(a) When both rotation sensors are normal The flow of the control operation is explained using the flowchart in Fig. 7. Both rotation sensors 41 and 42
If there is no failure and normal rotation signals nf and nr are output, step 100 → step 101 →
The process proceeds as follows: step 102 → step 103 → step 104 → step 105 → step 106 → step 107 → step 108. In step 108, the clutch pressure corresponding to the transmitted torque ΔT calculated in step 107 is obtained by the final correction calculation. A control signal c is output.

Incidentally, this program execution is started by the ON signal i from the ignition switch 43, and in step 100, the input signal is read,
In step 101 and step 102, calculations are performed that serve as the basis for determining whether the rotation sensors 41 and 42 are abnormal.In steps 103 and 104, it is determined whether the rotation sensors 41 and 42 are abnormal.In steps 105 to 107, the operation is performed. Calculations and table searches necessary for force distribution control are performed.

Due to this drive force distribution control in the normal state, when driving there is no difference in rotation between the front and rear wheels, the vehicle is almost rear-wheel drive, and when there is a difference in rotation between the front and rear wheels during sudden acceleration or braking, or when driving on a road with a low friction coefficient. etc.,
A four-wheel drive state is established in which the front wheel drive force distribution increases in accordance with the magnitude of the rotational difference.

As shown in Fig. 6, the driving force distribution control function gradually changes the driving force distribution depending on the degree of rotational speed difference between the front and rear wheels. Furthermore, there is no drive loss.

(b) If both rotation sensors are abnormal, the flow of control operation is from step 100 to step
101 → Step 102 → Step 103 (→ Step
104) → Step 109 → Step 110 → Step
The program then proceeds to step 111, where a control signal c is output to release the clutch pressure and bring the rear wheels into a driving state.

In addition, in step 103 and step 104, it is determined whether there is any abnormality in the rotation signals nf, nr output from the respective rotation sensors 41, 42, and in step 109, it is determined that there is an abnormality in the vehicle speed sensor 50 and ΔVf>A. Alternatively, a check is made if it is determined that ΔVr>A.

Therefore, if the vehicle speed signal v from the vehicle speed sensor 50 is abnormal, the process proceeds from step 103 or step 104 to step 109 → step 111, and the rear wheel drive is changed as in the case where the rotation signals nf, nr are abnormal. A control signal c to set the state is output.

Further, in step 110, it is checked whether the actual vehicle speed V based on the vehicle speed signal v is V>0, that is, whether the vehicle speed sensor 50 is operating.
If you make a wrong judgment that A, ΔVr>A,
Perform normal driving force distribution control. The flow of operation at this time is from step 103 or step 104 to step 109 → step 110 → step 105.
→ Step 106 → Step 107 → Proceed to step 108.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, although the embodiment shows a four-wheel drive vehicle based on a rear-wheel drive vehicle, it may also be a four-wheel drive vehicle based on a front-wheel drive vehicle. In that case, the rotational speed difference ΔN may be calculated as Nf - Nr.

In addition, in the embodiment, a vehicle speed sensor is provided in addition to a sensor that detects the rotational speed of the wheels, but the vehicle speed sensor is not necessarily required. It may be determined that the rotation sensor is abnormal by detecting that it continues to output an impossible value.

Further, in the embodiment, the relationship between the transmission torque ΔT and the rotational speed difference ΔN is set so as to obtain the characteristics of a viscous clutch, but there is no need to limit the relationship to this.

Further, the means for controlling the clutch engagement pressure is not limited to the electromagnetic proportional relief valve of the embodiment, but other means may be used.

Further, the mounting position of the rotation sensor is not limited to the mounting position of the embodiment as long as it is provided in the drive transmission system of the front wheel side and the rear wheel side.

In addition, in the embodiment, an example was shown in which a variable torque clutch that can gradually change the driving force distribution ratio to the front and rear wheels was used as a transfer, but a dog clutch or the like could be used to change between 2-wheel drive and 4-wheel drive.
It can also be applied to devices equipped with a transfer that can be switched ON/OFF.

In that case, the control map of front wheel torque ΔT and rotational speed difference ΔN is ΔN=B (however, B<A)
Any device may be used as long as it is set so that the dog clutch is activated when a rotational difference exceeding .

(Effects of the Invention) As described above, the driving force distribution control device for a four-wheel drive vehicle of the present invention is provided with an abnormality detecting means for detecting an abnormality in the rotation sensor, and the abnormality detecting means is configured to detect an abnormality. The control means outputs a control signal to put the actuator into a two-wheel drive state when the rotation signal indicated by It is possible to cancel the driving force distribution control in the four-wheel drive direction to the A and fix the two-wheel drive state, and to perform the driving force distribution control based on the rotation signal regardless of whether it is normal or abnormal.
The effect is that a large load is not constantly applied to the power train system and tight corner braking does not occur.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a claim showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention, Fig. 2 is an overall view showing a driving force distribution control device of an embodiment, and Fig. 3 is a transfer diagram of the embodiment device. 4 is a block diagram showing the control unit of the embodiment device, and FIG. 5 is a graph showing the relationship between the rotation speed difference and the transmitted torque stored in advance in the control unit of the embodiment device. FIG. 6 is a graph showing the relationship between the rotation speed difference and the driving force distribution ratio in the embodiment device, and FIG. 7 is a flowchart showing the flow of control operations in the control unit of the embodiment device. DESCRIPTION OF SYMBOLS 1... Front wheel, 2... Rear wheel, 3... Transfer, 4... Actuator, 5, 6... Rotation sensor, 7... Control means, 8... Abnormality detection means,
...rotation signal, ...control signal.

Claims (1)

[Claims] 1. Input rotation signals from a transfer provided in the middle of a drive power transmission system to the front and rear wheels, an actuator that operates the transfer, and a rotation sensor provided in each of the drive power transmission systems of the front and rear wheels,
A control device for outputting a control signal to the actuator based on the rotation signal, a driving force distribution control device for a four-wheel drive vehicle, further comprising an abnormality detection means for detecting an abnormality in the rotation sensor,
Driving force distribution for a four-wheel drive vehicle, characterized in that the control means outputs a control signal for setting the actuator to a two-wheel drive state when a rotation signal indicating an abnormality is input to the abnormality detection means. Control device.