JPH08237811A - Front-and-rear-wheel-drive vehicle - Google Patents

Abstract

PURPOSE: To provide a front-and-rear-wheel-drive vehicle in which the drop in a torque in the high-rotation region of an electric motor can be suppressed as far as possible by a method wherein the electric motor is constituted of a DC motor, a plurality of batteries which supply electric power to the electric motor are installed and a changeover means which connects the batteries in parallel in the low-rotation region of the electric motor and which connects them in series in the high-rotation region is installed. CONSTITUTION: An electric motor 5 is constituted of a DC motor, electric power from both batteries 91 , 92 is supplied to the electric motor 5 via a switch 10 and an advance and reverse changeover circuit 11, and a clutch 7 is turned on and off by the switch 10. In addition, switches 12a, 12b, 12c for a connection changeover circuit 12 are controlled so as to be turned on and off by an electronic control unit(ECU) 13. Both batteries 91 , 92 are connected in parallel in the low-rotation region of the electric motor 5 and both batteries 91 , 92 are connected in series in the high-rotation region. Thereby, the torque of a front- and-rear-wheel-drive vehicle can be increased in the low-rotation region, and the drop in the torque in the high-rotation region can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front and rear wheel drive vehicle in which one of the front and rear wheels is driven by an engine and the other is driven by an electric motor.

[0002]

2. Description of the Related Art Conventionally, in this type of front and rear wheel drive vehicle, an induction motor is used as an electric motor, and it is known that an electric motor can be operated over the entire vehicle speed range by inverter control (Japanese Patent Laid-Open No. Hei 10 (1999) -242977). 3-159502).

[0003]

In order to cover the entire vehicle speed range as in the above-mentioned conventional example, the electric motor needs to have a large output, and further, an inverter circuit is required, resulting in a high cost. . By the way, in order to limit the purpose of use of the electric motor to start assistance on slippery roads such as snowy roads,
If the electric motor is operated only when the vehicle speed is equal to or lower than the set value, an inexpensive DC motor used as a cell motor or the like can be used. However, in the DC motor, since the generated torque is inversely proportional to the rotation speed, there is a problem that the torque in the high rotation range becomes insufficient and tends to occur. The present invention
In view of the above points, it is an object of the present invention to provide a front-and-rear-wheel drive vehicle that uses a DC motor as an electric motor to reduce costs and to suppress a torque decrease in a high rotation range as much as possible. There is.

[0004]

In order to achieve the above object,
The present invention relates to a vehicle in which one of the front and rear wheels is driven by an engine and the other is driven by an electric motor, in which the electric motor is a DC motor, a plurality of batteries for supplying electric power to the electric motor are provided, and these batteries are It is characterized in that switching means for connecting in parallel in a low rotation range of the motor and connecting in series in a high rotation range is provided.

[0005]

When the batteries are connected in parallel, the torque increases in the low speed range, but the torque decreases significantly in the high speed range. On the other hand, when the batteries are connected in series, the torque in the low speed range does not increase as much as in the left, but the torque does not decrease much even in the high speed range, and the torque in the high speed range becomes greater than that in the parallel connection. Therefore, according to the present invention, it is possible to increase the torque in the low rotation range and suppress the decrease in the torque in the high rotation range.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated embodiment is a four-wheeled vehicle having a pair of front wheels 1 and a pair of rear wheels 2, one pair of left and right front wheels 1 being an engine 3.
Driven by a transmission 4 and a pair of left and right rear wheels 2 is driven by an electric motor 5 to reducer 6, clutch 7 and differential gear 8
Driven through and.

The electric motor 5 is composed of a DC motor. Two batteries 9 ₁ and 9 ₂ are provided for the motor, and electric power from both batteries 9 ₁ and 9 ₂ is supplied to a switch 10 and a forward / reverse switching circuit 11. Connection to the electric motor 5 via the switch 10 to turn the clutch 7 on and off by turning the switch 10 on and off, and to switch between both batteries 9 ₁ and 9 ₂ connected in parallel and in series. The switching circuit 12 is provided.

The switch 10 and the forward / reverse switching circuit 1
1, an electronic control unit (ECU) 13 for controlling the connection switching circuit 12 is provided, and the ECU 13 is provided with a signal from the speed sensor 14 of the front wheel 1, a signal from the speed sensor 15 of the rear wheel 2, and a forward / backward movement linked with the shift lever. The vehicle speed calculated by the signal of the speed sensor 15 is less than or equal to a set value, for example, 15 km / h or less, and the front wheel 1 slips due to the difference in rotational speed between the front and rear wheels 1 and 2. When it is determined that the vehicle is running, the forward / reverse switching circuit 11 is switched according to the determination switch 16, the switch 10 is turned on, and the rear wheel 2 is driven by the operation of the electric motor 5 to assist the vehicle in starting.

The connection switching circuit 12 includes both batteries 9
_{A first} switch 12a for connecting the positive electrodes of ₁ and 9 ₂ to each other, a second switch 12b for connecting the negative electrode of battery 9 _{1 to} the positive electrode of battery 9 ₂ , and a first switch 12a for connecting the negative electrodes of both batteries 9 ₁ and 9 ₂ . 3 switches 12c are provided, and both batteries 9 ₁ and 9 ₂ are connected in parallel when the first switch 12a and the third switch 12c are turned on and the second switch 12b is turned off. 3 switch 12
Both batteries 9 ₁ and 9 ₂ are connected in series when c and c are turned off and the second switch 12b is turned on. Then, the ECU 13 causes the first to third switches 12a, 1
The on / off control of 2b and 12c is performed to switch between parallel connection and series connection.

An ordinary vehicle battery of 12 V is used as both batteries 9 ₁ and 9 ₂ , a DC magnet type motor having a rated output of 2 KW is used as the electric motor 5, and a speed reducer 6 is used.
When the experiment was conducted with a gear ratio of 103, the relationship between the rear wheel speed and the motor terminal voltage was found to be that of both batteries 9 ₁ , 9 ₂
When connected in parallel, line a in Fig. 2, both batteries 9 ₁ , 9 ₂
The look like the line b of FIG. 2 when connected in series, The relationship between the rear wheel speed and motor current, both the battery 9 _1,
When 9 ₂ are connected in parallel, line a in FIG. 3, both batteries 9 ₁ ,
When 9 ₂ is connected in series, it becomes like the line b of FIG. 3, and the relationship between the rear wheel speed and the driving torque of the rear wheel is as shown in the line a of FIG. 4 when both batteries 9 ₁ and 9 ₂ are connected in parallel. become,
When both batteries 9 ₁ and 9 ₂ were directly connected, it became like the line b in FIG. The lines c in FIGS. 2, 3 and 4 show the characteristics when one battery is used.

As shown in FIG. 5, the voltages and internal resistances of the batteries 9 ₁ and 9 ₂ are Eb and Rb, the wiring resistance between the batteries 9 ₁ and 9 ₂ is R ₁ , and the battery 9 ₂ and the electric motor. 5 is R ₂ and the internal resistance of the electric motor 5 is Rm, the motor current Im when the motor rotation speed is zero is equal to that of the batteries 9 ₁ and 9 ₂ as shown in FIG. When connected in parallel, Im = Eb / {2R ₂ + Rm + (2R ₁ + Rb) · Rb /
(2R ₁ + 2Rb)}, and when batteries 9 ₁ and 9 ₂ are connected in series as shown in FIG. 5B, Im = 2Eb / (2Rb + 2R ₁ + 2R ₂ + Rm).

According to the measured values, Eb = 12.3V, Rb
= 6.11 mΩ, Rm = 3.44 mΩ, and when the batteries 9 ₁ and 9 ₂ are connected in parallel, R ₁ = 7.10 and R ₂
= 1.63, and when batteries 9 ₁ and 9 ₂ are connected in series, R ₁ = 7.10 mΩ and R ₂ = 4.44 mΩ.
Therefore, when the motor current Im is obtained by substituting these measured values into the above equations, Im = 1080 (A) when the batteries 9 ₁ and 9 ₂ are connected in parallel, and the batteries 9 ₁ and 9 ₂ are connected in series. At time Im = 635 (A).

As is apparent from FIGS. 2, 3 and 4, when the rear wheel speed is 62 rpm (6.6 km / h in terms of vehicle speed), the motor terminal voltage, motor current and drive torque are connected in parallel and in series. The drive torque is equal to 62 rpm when connected.
In the low rotation speed range below, the parallel connection is larger and 62rp
In the rotation range of m or more, the serial connection becomes larger.

Therefore, the ECU 13 controls the connection switching circuit 1
The first to third switches 11a, 11b, 11c of No. 1 are on / off controlled as described above, and both batteries are connected in parallel in the low rotation range of the electric motor 5 (rear wheel speed is 62 rpm or less), so that the electric motor 5 High rpm range (rear wheel speed is 6
In the range of 2 rpm or more), both batteries 9 ₁ and 9 ₂ are connected in series to increase the torque in the low speed range and suppress the decrease in the torque in the high speed range.

Both batteries 9 ₁ and 9 ₂ are always connected in parallel, and both batteries 9 ₁ and 9 ₂ are charged by the generator 17 driven by the engine 3 via the belt 17a.
Moreover, also used in the battery for supplying power to one of the battery 9 ₁ generally electrical equipment 18.

Although the embodiment using the _two batteries 9 ₁ and 9 ₂ has been described above, the present invention can be similarly applied to the case where three or more batteries are used. Further, although the front wheels 1 are driven by the engine 3 in the above embodiment,
The present invention can be similarly applied to a vehicle in which the rear wheels 2 are driven by the engine 3 and the front wheels 1 are driven by the electric motor 5.

[0017]

As is apparent from the above description, according to the present invention, the cost can be reduced by using the DC motor as the electric motor for driving the wheels, and the DC motor can be used in the high rotation range which is a problem. The torque decrease can be suppressed, and the start assist by the electric motor can be reliably performed.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing an example of implementation of the present invention.

FIG. 2 is a graph showing change characteristics of motor terminal voltage.

FIG. 3 is a graph showing change characteristics of motor current.

FIG. 4 is a graph showing torque change characteristics.

5A is a diagram showing a circuit resistance when the batteries are connected in parallel, and FIG. 5B is a diagram showing a circuit resistance when the battery is connected in series.

[Explanation of symbols]

1 Front Wheel 2 Rear Wheel 3 Engine 5 Electric Motor 9 ₁ , 9 ₂ Battery 12 Connection Switching Circuit 13 ECU

Claims (1)

[Claims] 1. In a vehicle in which one of front and rear wheels is driven by an engine and the other is driven by an electric motor, the electric motor is constituted by a DC motor, and a plurality of batteries for supplying electric power to the electric motor are provided, and these batteries are connected to each other. A front-rear-wheel drive vehicle provided with switching means for connecting the electric motors in parallel in a low rotation range and connecting them in series in a high rotation range.