JPS6123728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forward/reverse switching device for an electric vehicle that uses a plurality of magnetic switches to switch the armature winding or field winding of a DC motor for driving the electric vehicle.

In conventional models, when the forward/reverse lever of an electric car is switched too quickly, the normally closed contact of the forward/reverse magnetic switch may cut off the current, so arc-resistant contact materials with excellent arc resistance are used. It was getting worse. In other words, in order to prevent the contacts from being worn out and melted by the arc that occurs when the contacts close and open, silver-based (mainly cadmium monoxide-based and silver-based) arc-resistant contact materials are used.
Since it used extremely expensive materials such as nickel (nickel, etc.), it had the disadvantage of being expensive.

In order to solve the above-mentioned drawbacks, the present invention forms an excitation circuit for the magnetic switch only when each normally open contact of the forward/reverse magnetic switch is open, thereby preventing arcing on the normally closed contact side. The object of the present invention is to provide a practical forward/reverse switching device for an electric vehicle that completely prevents any driving operation and allows the use of inexpensive current-carrying contact materials for normally closed contacts.

Embodiments of the present invention will be described below with reference to the drawings.

1 is a DC power supply, 2 is a DC motor for driving, and 3,4
are the field winding and armature winding of the motor, respectively.
5 is an electric motor control device that controls the rotation speed of the electric motor for driving to make the traveling speed of the electric vehicle variable;
For example, it may be a resistance-type control device that short-circuits resistors in sequence, or a semiconductor chopper-type control device that changes the conduction rate by turning on and off a semiconductor switch. 61 and 71 are the excitation coil and main contact portion of the forward magnetic switch, respectively, and this main contact portion 71 is connected to the normally open contacts 81 and 9.
The contact points 91 and 101 are normally soldered to a movable piece 121, and the movable piece 121 is made movable by a fulcrum 131. When the excitation coil 61 is not energized, the main contacts 71 are connected as shown, but when the excitation coil 61 is energized, the normally open contacts 81 and 91 are closed and the normally closed contacts 101 and 111 are closed. It becomes open.

Similarly, 62 and 72 are the excitation coil and main contact portion of the reverse magnetic switch, respectively, and the main contact portion 72 is the normally open contacts 82 and 92 and the normally closed contact 10.
The control points 92 and 102 are attached to the movable piece 122, and the control points 92 and 102 are attached to the movable piece 122.
is movable by a fulcrum 132. When the excitation coil 62 is not energized, the main contact portion 72 is connected as shown in the figure.
2 is energized, normally open contacts 82, 9, contrary to the illustration.
2 is closed, and the normally closed contacts 102 and 112 are opened.

Reference numeral 14 is a forward/reverse changeover switch for the excitation circuit, which is composed of a forward switch 15 and a reverse switch 16. Generally, switches 15 and 16 are opened in the neutral state by manual operation by the driver, and switch 15 is opened in forward motion. When the vehicle is moving in reverse, the switch 16 is closed. Further, 17 is a key switch. Further, diodes 18 and 19 are provided in parallel with the excitation coils 61 and 62 of the forward and backward magnetic switches, respectively, to absorb back electromotive force when the excitation coils are de-energized.

Further, 30 is a normally open contact open detection circuit for detecting that both forward and reverse normally open contacts are open, 21 is a thyristor, 31 is a transistor,
32, 33, 34, and 35 are resistors, and the base of the transistor 31 is connected to the normally closed contacts 111, 112 on the fixed side of the magnetic switch via the resistor 35.
connected to the common terminal of

In the above configuration, the key switch 17 is closed,
When the forward/reverse selector switch 14 is set to the forward side, for example, the switch 15 is closed, and at this point, the normally open contacts 81, 91 and 82 of the magnetic switch are closed.
If 92 is open, the transistor 31 is cut off, and a gate current flows through the resistor 32 to the gate of the thyristor 21, making it conductive and energizing the excitation coil 61 of the forward magnet switch.As a result, the forward magnet switch is energized. The connection of the main contact part 71 of the network switch is reversed from the illustration, and the normally open contacts 81, 9 are connected.
1 is closed, and normally closed contacts 101 and 111 are opened.

On the other hand, regarding the main contact portion 72 of the reverse magnetic switch, as shown in the figure, current flows in the field winding 3 of the traveling motor from the fulcrum 131 to the fulcrum 132, causing the motor 2 to rotate in the forward direction. do.

In the case of backward movement, contrary to the above, the field winding 3 has fulcrum 1.
Current flows from 32 to the fulcrum 131 of the motor 2
rotates in the backward direction.

On the other hand, in the neutral state, neither of the magnetic switches is energized, the main contact portions 71 and 72 are as shown, and the electric motor 2 is not energized, so that the electric motor 2 does not rotate.

By the way, when the forward/reverse selector switch 14 is set to the forward side, the normally open contacts 81, 91 of the forward magnetic switch are closed;
As a result, an arc is generated between the contacts 81 and 91. On the other hand, normally closed contacts 101, 11
When 1 is open, no current is flowing, so no arc occurs.

On the other hand, when changing from the forward state to the neutral state, the switch 15 of the forward/reverse selector switch 14 is opened, cutting off the current between the normally open contacts 81 and 91, generating an arc, and at the same time, the normally closed contacts 101 and 111 are closed. However, at this time, since no current is applied between the normally closed contacts 101 and 111, no arc occurs. Similarly, in the reverse magnetic switch, the normally open contact 82,
92 directly interrupts the current both when closed and when opened, so an arc occurs, but normally open contacts 102 and 112
No arc is generated. Note that if the driver operates the forward/reverse selector switch 14 from the forward side to the neutral side and then to the reverse side extremely quickly, the switch 16 will close almost at the same time as the switch 15 opens. While the normally open contacts 81 and 91 of the forward magnetic switch are closed, the transistor 31 of the normally open contact open detection circuit 30 is conductive and the thyristor 21 is kept in the cut-off state, so the excitation coil 62 is not excited. Normally closed contacts 102 and 112 of the reverse magnetic switch remain closed.

Next, normally open contact 8 of the forward magnetic switch
1,91 opens, the normally open contact open detection circuit 3
Since the transistor 31 of 0 is cut off and the thyristor 21 is conductive, an excitation circuit of the excitation coil 62 is formed, and the normally closed contact 1 of the reverse magnetic switch 72 is closed.
02,112 opens without interrupting the current,
Normally open contacts 82, 92 close. At this time, when the normally open contacts 82 and 92 are closed, a current flows and an arc is generated. Also, no arc occurs at the normally closed contacts 101 and 121 when switching quickly from the reverse side to the forward side.

That is, the excitation circuit of the magnetic switch is formed only when each normally open contact of the forward/reverse magnetic switch is open, completely preventing the occurrence of arcing on the normally closed contact side in any driving operation. This has the advantageous effect that inexpensive current-carrying contact materials can be used for normally closed contacts.

[Brief explanation of the drawing]

The drawing is a wiring diagram showing an embodiment of the device of the present invention. 1...DC power supply, 2...DC motor for driving, 5...
Electric motor control device, 14... Forward/forward selector switch, 6
1, 62... Excitation coil of forward and reverse magnetic switch, 71, 72... Main contact part, 30...
Normally open contact open detection circuit, 101, 102, 11
1,112...Normally closed contact.

Claims (1)

[Claims] 1. A forward/reverse switching device for an electric vehicle, which connects a DC power source, a plurality of magnetic switches, and a DC motor for driving in series, and connects the plurality of magnetic switches so that the direction of rotation of the DC motor is reversible. A forward/reverse switching device for an electric vehicle, wherein the excitation circuits of the plurality of magnetic switches are energized only when at least each normally open contact of the plurality of magnetic switches is open.