JPS63151526A - Power transmitting device for four-wheel drive car - Google Patents

Abstract

PURPOSE:To optimize the distribution of braking force in 4WD for transmitting rotational torque of a drive device to rear wheels through an electric motor with the generating brake, by nullifying the output current of motor in the operation of brake to release rotational restraint. CONSTITUTION:Rotary torque of a drive device 1 consisting of an engine and a transmission is transmitted to front wheels 4 as main drive wheels, while power is transmitted to rear wheels 7 as driven wheels through an electric motor 11 consisting of a rotor 12, stator 13 and output terminal 14 connected to a resistor 15 by utilizing a generating brake. A brake pedal switch 16 is connected in series to the resistor 15 to open the contact in the operation of brake pedal, nullify the output current of motor 11 and shut off the generating braking. The front and rear wheels 4, 7 are released from the restraint of rotation, and the rotation of rear wheels is freed so that an optimum distribution of braking becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power transmission device for a four-wheel drive vehicle that utilizes dynamic braking by an electric motor.

(Prior Art) The present applicant previously disclosed in Japanese Patent Application No. 61-215375,
The rotational torque of the drive device is directly connected to the main drive wheel and transmitted to the slave drive wheels via an electric motor that is connected to a resistor to an output terminal provided on either the rotor or the stator. We have proposed a power transmission system for four-wheel drive vehicles (hereinafter referred to as 4WD vehicles). According to this, the differential rotation-transmission torque characteristic can be easily and widely changed by dynamic braking of the electric motor.

By the way, in general two-wheel drive vehicles, it is essential from the viewpoint of braking stability that the rear wheels are not locked during braking. This is because when the rear wheels lock, the tires lose their rolling direction, and the lateral grip of the rear wheels rapidly decreases, resulting in oversteer.

Therefore, in a normal vehicle, it is necessary to set the brake force distribution on the front wheel side higher than that on the rear wheel side with respect to the brake force distribution between the front and rear wheels determined from the weight distribution between the front and rear wheels. This allows the rear wheels to remain unlocked even when the front wheels are locked, ensuring stability during braking.

Particularly in front-wheel drive vehicles with light rear wheel loads, the loads on the front and rear wheels are as shown in Figure 3.

(Wr), and the road surface friction coefficient (tou) is the maximum braking force that can be generated by each of the front and rear wheels (Fr), (Fr)
are Fr = 74Wr and Fr = IAWr.

Therefore, the brake force distribution that locks the front and rear at the same time (Bro
/Bro) is BrOFr wr BrOFr Wr Therefore, in order to lock the front wheels first, Br
It needs to be wr.

(Problem to be solved by the invention) However, in a 4WD vehicle in which the front and rear wheels are directly connected as shown in Fig. 4, the front and rear wheels rotate at the same speed, so the tire slip rate (S) is , -RW ■ However, V: road surface speed R: tire radius W: tire rotational speed, and if the tire radius is the same for the front and rear wheels, the slip ratio (S) will be the same for the front and rear wheels. Here, braking force (B)
is BccSXW, where W: tire load, so in a direct-coupled 4WD vehicle, it is not Br Wr but always Br Wr Br wr .

This means that the rear wheels are locked at the same time as the front wheels are locked, and at the same time the vehicle becomes unstable, making it impossible to ensure braking stability.

Therefore, an object of the present invention is to prevent the dynamic braking of the electric motor that transmits rotational torque to the driven wheels from being performed when the vehicle is braked, thereby releasing the restraint on the rotation of the front and rear wheels during the brake operation and reducing the braking force. To provide a power transmission device for a 4WD vehicle in which distribution can be performed advantageously.

(Means for Solving the Problems) In order to achieve the above object, the present invention directly connects and transmits the rotational torque of the drive device (1) to the main drive wheels (4), (4), and The wheels (7), (7) are equipped with a control device (21) that limits the output current of the electric motor (11) to almost zero when the brakes of the vehicle are operated in a 4WD vehicle that transmits power through the electric motor (11). It is characterized by having been established.

(Function) Since the output current of the electric motor (11) is limited to almost zero during brake operation, the electric motor (11) hardly performs dynamic braking, and the restraint on the rotation of the front and rear wheels is removed. This makes it possible to set an appropriate brake force distribution between the front and rear wheels.

(Example) Fig. 1 shows an example of a power train of a 4WD vehicle to which the present invention is applied, in which (1) is a drive device consisting of an engine and a transmission, (2) is a propulsion shaft, (3) is a front differential, ( 4) is the left and right front wheels that form the main drive wheels, (5) is the drive shaft thereof, (8) is the rear differential, (7) is the left and right rear wheels that are the slave drive wheels, (8) is the drive shaft, The propulsion shaft (2) is divided in front of the rear differential (8), and an electric motor (11) is interposed in the divided portion.

The electric m (11) consists of a rotor (12), a stator (13) forming its housing, and a resistor (15) connected to an output terminal (14) provided on the rotor (12). ,
The stator (13) is connected to the drive device (1) side. According to this, the stator (13) is the input shaft and the rotation shaft (12)
Activated braking is performed according to the load resistance (R) of the resistor (15) using the output shaft as the output shaft, and the output torque (T) is generally generated according to the differential rotation (in - w2) between the input and output shafts.

A brake pedal switch (16) is connected in series with the resistor (15) to constitute a control device (21).

The brake pedal (17) is connected to work in conjunction with the brake pedal (17), and is normally in the ON state, but the brake pedal (17)
When the driver depresses the movable contact (tea), the movable contact (tea) separates from the fixed contact (18b) and the switch (1B) becomes OFF.

Thus, during normal driving, the brake pedal switch (1B)
is kept ON and electric braking is performed by electric a (11). However, when the driver depresses the brake pedal (17) and performs a brake operation, the brake pedal switch (
1B) is turned off, and the output current of electric motor 11 (11) (
Since i) becomes zero, the electric motor (11) no longer performs dynamic braking. Therefore, the front wheels (4), (4) and the rear wheels (7),
The rotation restraint with (7) is separated, and the rear wheels (7), (7)
Since the rotation of the wheel becomes free, it is possible to set the optimum brake force distribution between the front and rear wheels based on the above-mentioned relationship of Br Wr.

Next, a control device using a microcomputer will be explained based on FIG. 2.

This control device (21) includes a microcomputer (22
), a digital-to-analog converter (26), an amplifier (28) constituting a constant current circuit (27), a field effect transistor (28), the resistor (15), and a motor (1
1) Differential amplifier (18) that amplifies the terminal voltage (M)
and a brake switch (18). The microcomputer (22) has a ROM (23), a CPU (2
4) and an input/output circuit (25), etc.
) is taken into the microcomputer (22) from the differential amplifier (1B) via the input/output circuit (25). In addition, the brake switch (13) is activated by detecting the brake oil pressure, and is always kept ON as described above, but is turned OFF when the brake is operated, so this switch (18) is set to 0.
N10FF is also taken into the microcomputer (22) in the same way.

The constant current circuit (27) is connected to the microcomputer (22) via a digital-to-analog converter (2B).
resistor (15) according to the control voltage (Ma2) output from
) of the electric motor (11) is controlled. The control voltage (Ma2) is accessed by a signal corresponding to the terminal voltage (Ma1) and is output to the constant electric wave circuit (27). Therefore, when the brake switch (19) is ON, the output current (i) is maintained in the relationship of i = v s / R, and when the brake switch (19) is OFF, the output current (i) is maintained at or near zero. The control voltage (Ma2) is set in advance so as to limit the voltage.

Incidentally, it is also possible to connect an acceleration detector that detects the longitudinal acceleration (G) of the vehicle in place of the switch that responds to the brake operation, and to perform current control according to the longitudinal acceleration (G).

Note that the input/output relationship between the power train and electric motor of the 4WD vehicle is not limited to the structure of the embodiment.

(Effects of the Invention) As described above, according to the present invention, in a 4WD vehicle in which the rotational torque of the drive device is directly connected and transmitted to the main drive wheels, and is transmitted to the slave drive wheels via an electric motor, By installing a control device that limits the output current of the electric motor to almost zero when the vehicle brakes are operated, it is possible to remove the restraint on the rotation of the front and rear wheels when the brakes are operated, thereby setting the optimal brake force distribution between the front and rear wheels. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a power train diagram showing an example of a 4WD vehicle to which the present invention is applied, Fig. 2 is a configuration diagram of an electric motor and a control device according to the second embodiment, and Fig. 3 is a side view showing braking force distribution of the vehicle. , FIG. 4 is a powertrain diagram of a direct-coupled 4WD vehicle. In the drawings, (1) is the drive device, (2) is the propulsion shaft, and (3
) is the front differential, (4) is the main drive wheel, (5) is the drive shaft, (8) is the rear differential, (7) is the slave drive wheel, (8) is the driving shaft, (11) is the electric motor, (12) ) is the rotor, (13) is the stator, (14) is the output terminal, (15) is the resistor, (
1B), (111) is a switch, (17) is a brake pedal, (18) is a differential amplifier, (21) is a control device, (
22) is a microcomputer, (26) is a digital
An analog converter, (27) a constant current circuit, (28) an amplifier, and (211) a field effect transistor. Figure 2

Claims (2)

[Claims] (1) The rotational torque of the drive device is directly connected to the main drive wheels for transmission, and the sub drive wheels are equipped with an electric motor that is connected to an output terminal on either the rotor or the stator. What is claimed is: 1. A power transmission system for a four-wheel drive vehicle, characterized in that the four-wheel drive vehicle is equipped with a control device that limits the output current of the electric motor to approximately zero when the vehicle brakes are operated. (2) The power transmission system for a four-wheel drive vehicle as set forth in claim 1, wherein detection of brake operation is performed by detecting a brake pedal switch, brake oil pressure, or longitudinal acceleration of the vehicle.