JPS63137024A - Power transmitting device for four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To cut off the restraint of rotation of front and rear wheels so as to prevent a lock of rear wheels at the time of brake operation of a vehicle by providing a control device restricting the output current of a motor to nearly zero when the rotation of rear wheels is going to exceed the rotation of front wheels. CONSTITUTION:A motor 11 is constituted of a rotor 12, a stator 13, and a resistor 15, 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 rotation of rear wheels is going to exceed the rotation of front wheels 4, the diode 16 cuts off the reverse current generated in the motor 11. At the time of brake operation, the rotation of rear wheels is going to exceed the rotation of front wheels by the brake force distribution and feed the reverse current when front wheels are locked, but this current is cut off by the diode 16 to prevent the power generation braking by the motor 11. Accordingly, the rotation restraint of front wheels and rear wheels is cut off, and a lock of rear wheels is prevented.

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 wheels and transmitted to the slave drive wheels via an electric motor that is connected to a resistor to the output terminal provided on either the two rotors 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 (To), as shown in Figure 5.

(Wr), and the road surface friction coefficient (Hiro) is the maximum braking force that can be generated by each of the front and rear wheels (Fr), (Fr
) is F(=aWr, Fr=Jiwr. Therefore, the brake force distribution (Bro /
Bro) is Bro Fr Wr Elro Fr Wr, so to lock the front wheels first, r w
It is necessary to set it to r.

(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. 6, the front and rear wheels rotate at the same speed, so the tire slip rate (S) is , ■ However, V: Road surface speed R: Tire radius W: Tire rotation 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)
Since there is a relationship between 4i and B (X: SXW, where 1w: tire load), in a direct 4WD vehicle, it will not be r wr but will always be BrW ( r wr ).

This means that the rear wheels lock at the same time as the front wheels lock, 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 rear wheels from being performed when the rotation of the rear wheels attempts to exceed the rotation of the front wheels. To provide a power transmission device for a 4WD vehicle, which prevents rear wheels from locking by removing restraints on wheel rotation, and enables advantageous distribution of brake force.

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

The present invention is characterized by the provision of a control device (21) that limits the output current of the electric motor (!) to almost zero when the rotation of (7) is about to exceed the rotation of the front wheels (4), (4).

(effect) Brake force distribution between front wheels (4) and (4) to rear wheels (7).

(7) When operating the brake set higher than the side,
The rotation of the rear wheels (7), (7) tries to exceed the rotation of the front wheels (4), (4), but in that case, the output current of the electric motor (11) is limited to almost zero, so the electric motor (11)
In this case, almost no dynamic braking is performed, and the restraint on the rotation of the front and rear wheels is removed. This makes it possible to set the optimum brake force distribution for the front and rear wheels and prevent rear wheel locking.

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

FIG. 1 shows an example of the 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, and (2) is a propulsion shaft.

(3) is the front differential, (4) is the left and right front wheels that form the main drive wheels, (5) is the drive shaft, (6) is the rear differential, (7)
are the left and right rear wheels forming the slave drive wheels, (8) is the drive shaft thereof, the propulsion shaft (2) is divided in front of the rear differential (8), and the electric motor (11) is interposed in the divided part. .

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 the input shaft and the rotation shaft (12)
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 (w+ -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 rear wheels (7), (7) is the same as that of the front wheels (4), (
This is to cut the current in the opposite direction that is generated in the motor (11) when the motor (11) attempts to exceed the rotation speed of the motor (11).

In the above, the brake force distribution on the front wheels (4), (4) side is set higher than on the rear wheels (7), (7) side.

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. When the brake is operated, the brake force is distributed to the rear wheels (7),
The rotation of (?) exceeds the rotation of front wheels (4), (4),
When the front wheels are locked, a current tries to flow in the opposite direction, but this is cut by the diode (16) and the electric current m (1
Since the output current (i) of the motor (1) becomes zero, the electric motor (1) does not perform dynamic braking. Therefore, the front wheels (4), (
4) and the rear wheels (7), the rotational restraints of (7) are separated,
Since the rear wheels (7) and (?) are free to rotate, it is possible to prevent the rear wheels from locking by setting the optimal brake force distribution between the front and rear wheels based on the above-mentioned relationship of r 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 (29), the resistor (15), and a motor (1
A differential amplifier (17) that amplifies the terminal voltage (vl) of 1)
It consists of Microcomputer (22) is ROM
(23), CPU (24) and input/output circuit (25)
The terminal voltage (1) is connected to the microcomputer (22) via the input/output circuit (25) from the differential amplifier (17).
).

The constant current circuit (27) is connected to the microcomputer (22) via a digital-to-analog converter (26).
resistor (15) according to the control voltage (Ma2) output from
) of the electric motor (11) is controlled. The control voltage (v2) is accessed by a signal corresponding to the terminal voltage (ma1) and is output to the constant current circuit (27). Therefore, when the generated terminal voltage (Mai) is positive, the output current (1) is maintained in the relationship 1 = vl/R, and when the terminal voltage (Ma1) is negative, the output current (i) is The control voltage (Ma2) is set in advance so as to be limited to zero or its vicinity.

FIG. 3 shows a third embodiment of the control device t(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 (1B), ( 19), the differential rotation is detected, and the same control is performed thereafter.

By the way, in one or more embodiments, when the vehicle is reversing, the rear wheels (7)
, (7), the driving force is no longer generated.

Therefore, as shown in Fig. 4, a changeover switch (31) is provided in front of the diode (IB), and its movable contact (31a)
When moving forward, the fixed contact (31b) on the diode (16) side
When reversing, it is connected to the bypass path (32) parallel to the diode (1B) as shown by the broken line. As a result, a forward current (it) flows through the diode (IB) when moving forward, and a forward current (it) flows through the diode (IB) when moving backward.
Since the current (IR) in the opposite direction flows by bypassing 6), driving force can be generated to the rear wheels (7) even when reversing.

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 front wheels, and transmitted to the rear wheels via an electric motor, A control device is installed that limits the output current of the electric motor to almost zero when the front wheels attempt to rotate, so it is possible to release the restraint on rotation of the front and rear wheels and prevent the rear wheels from locking when the vehicle's brakes are applied. Therefore, it is possible to set the optimum brake force distribution between the front and rear wheels.

[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 configuration diagram of the third embodiment. FIG. 4 is a power train diagram similar to FIG. 1 showing the fourth embodiment;
FIG. 5 is a side view showing the brake force distribution of the vehicle, and FIG. 6 is a power train 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 front wheel, (5) is the drive shaft, (
6) is the rear differential, (7) is the rear wheel, (8) is the drive shaft, (
11) is the electric motor, (12) is the rotor, (13) is the stator, (14) is the output terminal, (15) is the resistor, (16) is the guide, (+7) is the differential amplifier, (18) , (I
EI) is the rotation speed detector, (21) is the 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, and (31) is a changeover switch. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney 2 1) Yu-Duma Patent Attorney
Kuni Ohashi, Patent Attorney Udo Koyama, Patent Attorney No [1]
Fig. 2 Fig. 3

Claims (5)

[Claims] (1) The rotational torque of the drive device is directly connected to the front wheels and transmitted to the rear wheels via an electric motor that is connected to a resistor to an output terminal provided on either the rotor or the stator. A four-wheel drive vehicle characterized by comprising: a control device that limits the output current of the electric motor to approximately zero when the rotation of the rear wheels attempts to exceed the rotation of the front wheels. power transmission device. (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. .