JP2000264086A - Four-wheel drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite electric automobile capable of realizing part- time four-wheel drive in an extremely simple constitution. SOLUTION: An induction motor 8 is provided for driving rear wheels 7, and the induction motor 8 is driven by AC power generated by a power generator 6 provided on the side of front wheels 1. Based on its characteristics, the induction motor 8 generates torque by deflection of a rotation field generated by a stator and rotation speed of a rotor to rotate and drive the rotor, so in a traveling condition where the front wheels 1 of an automobile are rotated without slipping, the rear wheels 7 are also rotated to follow them at the same rotation speed with the front wheels 1 without causing the induction motor 8 to become a resistance, or generating rotation torque. However, once the front wheels 1 slip, deflection is generated between the rotation field generated at the stator of the induction motor 8 and the rotation speed of the rotor by AC power generated by the power generator 6, when drive torque to the rear wheels 7 is generated to make a four-wheel drive condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a four-wheel drive device for an electric vehicle.

[0002]

2. Description of the Related Art Conventionally, for example, in a compound electric vehicle in which one of front and rear wheels (hereinafter, referred to as a front wheel) is rotationally driven by a prime mover, when a four-wheel drive device is configured, the prime mover drives the front wheel shaft. The generator is rotated and the generator is rotated, and the AC power generated by the generator is converted to AC power.
In this configuration, the DC power is converted to DC and stored in a capacitor or a storage battery, and the stored power is DC-AC converted and supplied to an AC motor for driving the rear wheels. The AC motor rotates the rear wheel shaft.

[0003]

However, in the case of such a conventional four-wheel drive system of a composite electric vehicle, the torque distribution between the drive torque of the front wheels by the prime mover and the drive torque of the rear wheels by the AC motor is controlled according to the driving situation. Therefore, a converter for performing AC-DC conversion, an inverter for performing DC-AC conversion, and a capacitor or storage battery for storing electricity are indispensable, and appropriate control of the converter and the inverter is necessary. Therefore, there is a problem that a controller for executing complicated arithmetic control is required, and the circuit configuration becomes complicated and the cost becomes high.

The present invention has been made in view of such conventional problems, and can be constructed with a simple structure, at a low cost, and reliably in a driving situation requiring four-wheel drive. It is an object of the present invention to provide a four-wheel drive device capable of driving.

[0005]

According to a first aspect of the present invention, there is provided a four-wheel drive system comprising: a first wheel drive shaft and a second wheel drive shaft;
A prime mover, a generator for generating AC power by a rotational driving force of the prime mover, and a rotational driving force of the prime mover of the first type.
A first transmission that transmits the rotation to the wheel drive shaft of the first motor, an induction motor that receives the AC power of the generator and is driven to rotate, and a rotation driving force of the induction motor that is driven by the second wheel drive. A second transmission that transmits the rotation to the shaft and drives the rotation.

In the four-wheel drive device according to the first aspect of the present invention, the second
The motor provided for driving the wheel axle is an induction motor. Due to its characteristics, the induction motor generates torque by causing a difference between a rotating magnetic field generated by a stator and a rotating speed of the rotor, thereby causing rotation. In a running state in which the wheels of the first wheel drive shaft of the automobile are rotating without causing slip, the wheels of the second wheel drive shaft are the same as the wheels of the first wheel drive shaft. The motor is driven to rotate at the rotation speed, and the induction motor does not become a resistance and does not generate a rotational torque, and therefore runs in a two-wheel drive state.

However, the first wheel drive shaft, such as when traveling on a slippery road surface or when the wheels are driven when the first wheels are stuck, for example, in a traveling condition that requires the original four-wheel drive. When the wheel of the first wheel drive shaft slips, the rotation speed of the wheel of the first wheel drive shaft becomes higher than the rotation speed of the wheel of the second wheel drive shaft, and a speed difference occurs. As a result, the rotating magnetic field of the stator of the induction motor becomes faster than the rotation speed of the rotor, causing slippage, and generating a rotating torque in the induction motor, thereby applying a rotational driving force to the second wheel drive shaft. To rotate the wheels to a four-wheel drive state.

[0008] As a result, the vehicle can run stably on a slippery road surface by the grip force of the wheels of the second wheel drive shaft that does not slip, and can escape from the stack.

[0009]

According to the first aspect of the present invention, a complicated circuit configuration as in the prior art is eliminated, and no expensive circuit components are required. In a driving situation requiring four-wheel drive, a part-time four-wheel drive device that can automatically shift to four-wheel drive reliably can be configured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows one embodiment of a four-wheel drive device in a hybrid electric vehicle. Hereinafter, for the sake of simplicity, the first wheel drive shaft will be described as a front wheel drive shaft, and the second wheel drive shaft will be described as a rear wheel drive shaft. However, practically, it does not matter that the order is changed.

The four-wheel drive includes a drive shaft 2 of a front wheel 1.
(ENG) 3, a transmission (T / M) 4 for transmitting the rotational driving force of the prime mover 3, and a differential gear for transmitting the rotational output of the transmission 4 to the left and right front wheels 1. (Diff) 5 and a generator (G) that is directly driven to rotate by the rotation driving force of the prime mover 3 to generate three-phase AC power
6 are provided. Here, the generator 6 may be connected to be rotationally driven by the rotational output of the transmission 4 that is rotationally driven by the prime mover 3.

The four-wheel drive device also includes an induction motor (M) 8 as a rotary drive mechanism for the rear wheel 7, a transmission (T / M) 9 for transmitting the rotational drive force of the induction motor 8, A differential gear (Diff) 11 for transmitting the rotational output of the transmission 9 to the rear wheels 7 via the left and right rear wheel drive shafts 10 is provided.

The front generator 6 and the rear induction motor 8 are connected by a three-phase high-current line 12. The generator 6 and the induction motor 8 have basically the same specifications, and one is used as a generator and the other is used as an induction motor. Therefore, the mechanical size and electrical characteristics of the rotor and the stator are the same. Then, the three-phase AC power generated by the generator 6 is supplied to the stator of the induction motor 8 through the three-phase high-power line 12.

Next, the operation of the four-wheel drive device having the above configuration will be described.

<Normal Travel> Normal travel in a state where no slip occurs in the front and rear wheels is as follows. Prime mover 3
Is transmitted to the front wheel drive shaft 2 via the transmission 4 and the differential gear 5 to drive the front wheels 1 to rotate and drive the automobile.

In this running state, the front and rear wheels 1, 7 are rotating at a constant speed because no slip has occurred in the front wheel 1, which is the driving wheel. Therefore, both the rotor of the generator 6 and the rotor of the induction motor 8 rotate at a constant speed. In the case of this constant-speed rotation, the generator 6 supplies the generated power of the curve B in FIG. 2A to the stator of the induction motor 8 through the three-phase high-power line 12. However, the rotor of the induction motor 8 has the same speed as the rotating magnetic field generated by the AC power supplied to the stator, and does not receive the rotating driving force from the rotating magnetic field. As indicated by the dots, the traction of the rear wheel 7 is almost zero.

That is, in a running state where there is no speed difference between the front and rear wheels 1 and 7, the vehicle runs in a two-wheel drive system in which the front wheel 1 is used as a driving wheel. Since the driving torque is generated only on the drive shaft on the generator 6 side (here, the front wheel drive shaft 2), the wheels (rear wheels 7) on the drive shaft side (here, the rear wheel drive shaft 10) on the induction motor 8 side. Does not slip.

<Slip on the front wheels> When the vehicle suddenly starts, runs on a slippery road surface, or when the front wheels 1 are stuck, the front wheels 1 slip and suddenly rotate. The speed increases, and a rotation speed difference is generated between the rear wheel 7 and the vehicle.

If such a speed difference occurs, the motor 3
, The front wheel drive shaft 2 rotates at high speed, and the rotation speed of the rotor of the generator 6 increases. As a result, the power output of the generator 6 is converted into a high-frequency three-phase alternating current and supplied to the stator of the induction motor 8 on the rear wheel side through the three-phase high-power line 12.

On the other hand, in the induction motor 8, since the rotation speed of the rear wheel 7 is lower than the rotation speed of the front wheel 1, the rotation speed of the rotor is also the same as the rotation speed of the rotor of the generator 6 on the front wheel side. It will be lower by the ratio. As a result, the induction motor 8
The rotation speed of the rotor is delayed with respect to the rotating magnetic field generated by the stator, and the rotor receives a driving torque as shown by a curve C in FIG. The shaft 10 and the rear wheel 7 are driven to rotate by the driving torque.

That is, when a slip occurs in the front wheel 1 and a rotational speed difference is generated between the front wheel 1 and the rear wheel 7, the induction motor 8 generates a driving torque corresponding to the speed difference, thereby causing the rear wheel 7 to rotate. It is driven to rotate, resulting in a temporary four-wheel drive state. As a result, if the front wheel 1 has a stack, the vehicle can get out of the stack, and even on a slippery road surface, stable driving can be achieved by four-wheel drive. Start acceleration will be obtained.

FIG. 2 (a) shows the range of the power generated by the generator 6 with respect to the output shaft rotation speed of the transmission 4 on the front wheel 1 side. Curve A shows the case where the front wheel 1 has a large slip. Shows the power generated by the generator 6 after the adjustment by the regulator, and the curve B shows the power generated by the generator 6 when the front and rear wheels 1, 7 are rotating at a constant speed.

The curve C in FIG. 2B shows the difference between the input shaft rotations of the front and rear wheel transmissions 4 and 9 (that is, the rotor rotation difference between the generator 6 and the induction motor 8).
0 shows the change in traction occurring at 0 (therefore, the rear wheel 7). As a result, the more the front wheel 1 is subjected to a larger slip, the greater the traction generated on the rear wheel 7, the greater the load on the front wheel 1 is, the less the traction is, the greater the effect of terminating the slip and re-adhering. Will work.

As described above, in the four-wheel drive device of this embodiment, in the hybrid electric vehicle, the power of the generator 6 driven by the prime mover 3 for driving the front wheels 1 is stored in a capacitor or a storage battery. The electric power of the generator 6 is directly supplied to the induction motor 8 as compared with a conventional four-wheel drive device that drives the rear wheel 7 by rotating the rear wheel driving motor using the stored power. Since the rear wheel 7 is driven to rotate, expensive and complicated circuit supplies for power conversion are not required, and a simplified configuration can be realized at low cost.

In normal running, the vehicle is driven by two wheels. When the vehicle is in a running state in which four-wheel drive is really required, the vehicle is automatically switched to four-wheel drive, and fuel efficiency can be improved.

Also, since the induction motor 8 for driving the rear wheels is basically driven by the electric power generated by the generator 6 on the front wheel 1 side, which is the first wheel drive shaft, the rear wheels 7 are larger than the front wheels 1. There is no possibility that the rear wheel 7 slips first, that is, in a state of fast rotation.

Further, this is a mechanism for turning the surplus of the front wheel drive output for rear wheel drive. The greater the slip of the front wheel 1, the greater the load on the rear wheel 7, which results in a decrease in the driving force of the front wheel 1. , TCS without any special equipment
(Torque Control System), which inherently has the function of realizing stable driving.

In addition, since the front wheel drive mechanism and the rear wheel drive mechanism are only connected by the high-power line 12,
Space saving can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention.

FIG. 2 is a graph showing a front-wheel rotation speed-generated power characteristic of the generator and a graph showing a difference in rotational speed between front and rear wheels-rear wheel traction characteristics in the embodiment.

[Explanation of symbols]

 Reference Signs List 1 front wheel 2 front wheel drive shaft 3 prime mover 4 transmission 5 differential gear 6 generator 7 rear wheel 8 induction motor 9 transmission 10 rear wheel drive shaft 11 differential gear 12 three-phase high-power line

Claims (1)

[Claims] A first wheel drive shaft and a second wheel drive shaft; a prime mover; a generator for generating AC power by a rotational drive force of the prime mover; A first transmission device that transmits the rotation to a wheel drive shaft, an induction motor that receives the AC power from the generator and is driven to rotate, and a rotation drive force of the induction motor that is the second wheel drive shaft Four-wheel drive device comprising: a second transmission that transmits the rotation to the second transmission.