JPS63137025A - Power transmitting device for four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To dissolve a tight corner braking phenomenon by providing a control device setting the output current of a motor to zero when front wheels generate a braking force in a 4WD vehicle transmitting the driving force to front wheels via the motor. CONSTITUTION:A motor 11 is constituted of a rotor 12, a stator 13, and a resistor 15 connected to an output terminal 14 provided on the rotor 12, and the stator 13 is connected to the driving device 1 side. A diode 16 is connected in series with the resistor 15 to constitute a control device 21. When the rotating speed of front wheels exceeds that of rear wheels and front wheels generate a braking force, the diode 16 cuts off the reverse current generated in the motor 11. At the time of low-speed turn, when the rotating speed of front wheels exceeds that of rear wheels and front wheels generate a braking force, the reverse current tends to flow, but this current is cut off by the diode 16, thus the power generation braking by the motor 11 is prevented, and the rotation restraint of front wheels and rear wheels is cut off.

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 (in Japanese Patent Application No. 61-215375) proposed that the rotational torque of the drive device is directly connected to the main drive wheels and transmitted, and that the subordinate drive wheels have either a rotor or a stator. We have proposed a power transmission device for a four-wheel drive vehicle (hereinafter referred to as 4WD vehicle) in which power is transmitted through an electric motor with a resistor connected to an output terminal provided on one side.According to this. ,
Electric! I] The differential rotation-transmission torque characteristics can be easily changed over a wide range by dynamic braking of the machine.

By the way, in a general two-wheel drive vehicle (rear-wheel drive vehicle in the illustration) as shown in FIG. 6, when turning at a low speed, the number of revolutions (W) of each wheel and the distance from the turning center are 11111 (R).
) is as follows. In other words, at low speeds, the turning trajectory of the front wheels is greater than that of the rear wheels, and the rotation speed of the front wheels is higher than that of the rear wheels.

(Problems to be Solved by the Invention) However, in a 4WD vehicle in which the front wheels and rear wheels are directly connected as shown in FIG. Since the relationship is +w2 w, +w4, when turning at low speed, a braking force (N) is generated at the front wheels and a driving force (F) is generated at the rear wheels, as shown in the figure.

Therefore, in order to turn a vehicle, in addition to the driving force originally required for turning, a driving force to overcome the braking force of the front wheels is required, and this amount becomes a horsepower loss. However, if the horsepower generated by the engine is smaller than this loss horsepower, the vehicle will not be able to turn, which is called a tight corner braking phenomenon, and has been a major weakness of direct-coupled 4WD vehicles.

Therefore, an object of the present invention is to prevent the dynamic braking of the electric motor that transmits rotational torque to the front wheels from being performed when the front wheels generate braking force, thereby releasing the restraint on the rotation of the front and rear wheels when the vehicle is turning at low speed. 4W that eliminates the tight corner braking phenomenon and enables smooth turns.
To provide a power transmission device for D vehicles.

(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 rear wheels (4), (4), while the front wheels (7) ), (7) is a 4WD vehicle in which power is transmitted via an electric motor (11).
).

(7) is characterized in that it is provided with a control device (21) that limits the output current of the electric motor (11) to approximately zero when generating braking force.

(Function) Since the output current of the electric motor (11) is limited to almost zero when the front wheels (7), (7) generate braking force,
The electric motor (11) hardly performs dynamic braking, and the restraint on rotation of the front and rear wheels is removed. This makes it possible to eliminate the tight corner braking phenomenon.

(Example) Examples will be described below based on the accompanying drawings.

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 rear differential, and (3) is a rear differential.
(4) is the left and right rear wheels that form the main drive wheels, (5) is its drive shaft, (6) is the front differential, (7) is the left and right front wheels that are the slave drive wheels, and (8) is its drive shaft. The propulsion shaft (2) is divided before the front differential (6), and an electric motor (11) is interposed in the divided portion.

The electric motor (11) consists of a rotor (12), a stator (13) forming a housing thereof, 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 a manual axis, a rotation axis (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 (WI W2) between the input and output shafts.

A diode (16) is connected in series with the resistor (15) to constitute a control device (21). This diode (
16), the rotation of the front wheels (7) and (7) is the same as that of the rear wheels (4).
, (4), and reduces the current in the opposite direction generated in the electric wjer (11) when the front wheels (7), (7) generate braking force.

Thus, during normal running, the electric motor (11) performs dynamic braking because the current (i) is allowed to flow in the forward direction of the diode (16) as shown in the figure. Then, when the driver performs a turning operation at low speed, the front wheels (7), (7) rotate faster than the rear wheels (4), (4), and the front wheels (7), (7) rotate faster than the rear wheels (4), (4).
7) When (7) generates braking force, a current in the opposite direction tries to flow, but this is cut by the diode (16) and the output current (i) of the motor (11) becomes zero, so The electric motor (11) no longer performs dynamic braking. Therefore, the rear wheels (4), (4) and the front wheels (7),
(7) The rotation restraint between the front wheel (7) and the front wheel (7) is separated.
, (7) is free to rotate, which eliminates the tight corner braking phenomenon and enables smooth turns.

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 the constant current circuit (27), a field effect transistor (29), and the resistor (15).
A differential amplifier (17) amplifies the terminal voltage (V, ) of
). Microcomputer (22) is ROM
(23), CPU (24) and input/output circuit (25)
The terminal voltage (V, ) is transmitted from the differential amplifier (17) to the microcomputer (2) via the input/output circuit (25).
2).

The constant current circuit (27) is connected to the microcomputer (22) via a digital-to-analog converter (26).
The resistor (15
) of the electric motor (11) is controlled. The control voltage (v2) is accessed by a signal corresponding to the terminal voltage (vl) and is output to the constant current circuit (27). Therefore, when the generated terminal voltage (vl) is positive, the output current (i) is maintained in the relationship of i = v, /R, and when the terminal voltage (vl) is negative, the output current (i) is set to zero. The control voltage (v2) is set in advance so as to limit the voltage to or near the voltage.

FIG. 3 shows a third embodiment of the control device (21). In this embodiment, instead of the differential amplifier (17), the input/output rotation speed of the electric motor (11) is detected by a rotation speed detector (18), ( 19), the differential rotation is detected, and the same control is performed thereafter.

By the way, in the above embodiment, when the vehicle is reversing, the front wheels (7)
, (7) No driving force is generated.

Therefore, as shown in FIG. 4, a changeover switch (31) is provided downstream of the diode (16), and its movable contact (31a
) when moving forward, the fixed contact (31b) on the diode (16) side
) as shown in the solid line, and when retracting, connect the diode (16)
It was connected to the bypass path (32) parallel to the broken line as shown by the broken line. As a result, a forward current (if) flows through the diode (16) when moving forward, and a forward current (if) flows through the diode (16) when moving backward.
16) and the current (ir) in the opposite direction flows, it is possible to generate driving force to the front wheels (7), (7) even when reversing.

However, this time a tight corner braking phenomenon occurs when turning backwards. Therefore, as shown in Fig. 5, another diode (33) is installed in parallel to cut the forward direction current (jf) when the front wheels (7), (7) generate braking force even when reversing. The movable contact (31a) of 31) is connected to the fixed contact (31c) on the diode (33) side as shown by the broken line when retracting.

This causes the front wheels (7) when reversing.

When turning while obtaining the driving force (7), the current (if) is cut by the diode (33), so the tight corner braking phenomenon when turning backward can also be eliminated.

Next, a sixth embodiment will be described.

In the sixth embodiment, the front @ (7), (
7) generates driving force and eliminates the tight corner braking phenomenon without switching between forward and reverse. Specifically, in the control device (21) in Fig. 3, the rotation speed (wl) of the rear wheels (4), (4) picked up by the rotation speed detectors (18), (19), respectively.
Based on the absolute value of the rotation speed (w2) of the front wheels (7) and (7), that of the heavy wheels (7) and (7) is the rear wheel (4).
, the current (i) is cut when it is larger than that in (4).

The method of controlling the current is shown in the table below. In the control table, a positive sign e is given to each rotational speed for forward movement, and a negative sign e is given for backward movement.

Control Table〉 By controlling the current in this way, it is possible to eliminate the tight corner braking phenomenon during low-speed turns without switching between forward and reverse, even though 4WD is used during normal driving both forward and backward. .

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 rear wheels, and is transmitted to the front wheels via an electric motor, the front wheels are controlled. By installing a control device that limits the output current of the electric yJJa& to almost zero when generating power, it is possible to remove the restraint on the rotation of the front and rear wheels when the vehicle turns at low speeds, eliminating the tight corner braking phenomenon, and therefore making it smoother. You can make sharp turns.

[Brief explanation of the drawing]

Fig. 1 is a powertrain 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 diagram showing the third embodiment and the sixth embodiment of the same. The configuration diagram of the example, FIGS. 4 and 5 are power train diagrams similar to FIG. 1 showing the fourth embodiment and the fifth embodiment, respectively,
Figure 6 is a powertrain diagram showing the turning state of a ZWD vehicle;
FIG. 7 is a powertrain diagram showing a turning state of a direct-coupled 4WD vehicle. In the drawings, (1) is the drive device, (2) is the propulsion shaft, and (3
) is the rear differential, (4) is the rear wheel, (5) is the drive shaft, (6)
is the front differential, (7) is the front wheel, (8) is the drive shaft, (1
1) is an electric motor, (12) is a rotor, (13) is a stator,
(14) is the output terminal, (15) is the resistor, (18),
(33) is a diode, (17) is a differential amplifier, (1
8), (19) is a rotation speed detector, (21) is a control device, (22) is a microcomputer, (26) is a digital-to-analog converter, (27) is a constant current circuit, (28)
) is an amplifier, (29) is a field effect transistor, (31
) is a changeover switch. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Part 2 1) Yong-Immediate Question Patent Attorney
Kuni Ohashi Production volume Patent attorney Small
Yama Yuyuki Patent Attorney No 1)
Shigeru Figure 2 Figure 3 Figure 6

Claims (6)

[Claims] (1) The rotational torque of the drive device is directly connected to the rear wheels and transmitted to the front wheels via an electric motor that is connected to a resistor to an output terminal provided on either the rotor or the stator. 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 front wheels generate braking force. (2) The power transmission device for a four-wheel drive vehicle according to claim 1, wherein the output current is limited depending on the direction in which the current flows. (3) The power transmission device for a four-wheel drive vehicle according to claim 1, wherein the output current is limited depending on whether the voltage generated by the electric motor is positive or negative. (4) The power transmission device for a four-wheel drive vehicle according to claim 1, wherein the output current is limited in accordance with a difference in rotational speed between front wheels and rear wheels. (5) A power transmission device for a four-wheel drive vehicle according to any one of claims 2 to 4, characterized in that when the vehicle is reversing, the output current restriction is canceled or reversed. . (6) The power transmission device for a four-wheel drive vehicle according to claim 1, wherein the output current is limited according to a difference in absolute values of rotational speeds of front wheels and rear wheels.