JPS6211123Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control device for a motor used in an electric vehicle such as a battery forklift, and more particularly to a small and simple braking control device for a DC motor for an electric vehicle.

Conventionally known control devices for the driving motors of electric vehicles such as battery forklifts use mostly electric braking methods called plugging braking, in which the driving electric motor is switched to a generator during braking to generate the vehicle's motion. The energy was converted into generated energy, and all of the generated energy was consumed in the braking circuit including the armature. Furthermore, in a so-called resistance control method in which the running speed is controlled by partially switching the resistance, most of the generated energy is consumed by the running control resistor. Furthermore, a regenerative braking system has been used in which the running motor of an electric vehicle is equipped with a special braking resistor and the generated energy is consumed by the resistor, or the energy is returned to the power source using a large number of changeover switches.

Here, the plugging braking system used in conventional electric vehicles such as battery forklifts uses the driving electric motor to convert all of the kinetic energy of the vehicle into heat energy and consume it. Electric cars, which are frequently started, braked, and reversed, have the disadvantage that the electric motor needs to have a very large heat capacity. Furthermore, energy is consumed by short-circuiting the armature, and in this case, from the viewpoint of braking feeling, it is necessary to limit the field current to a very small value. The drawback was that the rectification conditions deteriorated due to secondary reactions. In addition, the resistance control method uses a resistor for running control, and has the disadvantage that power loss is large during both powering and braking, and speed control is stepwise. Furthermore, the dynamic braking system and regenerative braking system used in trains require large capacity resistors or a large number of changeover switches.
The disadvantage is that these controls are complicated, and it is not suitable for electric vehicles such as battery forklifts, which require compactness and low cost and are powered by a finite energy source. .

The present invention is a simple motor control system for an electric vehicle equipped with at least one of a conventional regenerative braking device and a plugging braking device, by simply adding one small-capacity resistor for pre-excitation in parallel to the main switching means. It is an object of the present invention to provide a motor control device for an electric vehicle that is configured to save energy and eliminate problems such as armature reaction of the motor.

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

In the accompanying drawings, reference number 1 indicates a DC power supply, 2
The motor is a DC series-wound motor and includes an armature 21 and a field winding 22. Reference numeral 3 indicates a chopper device such as a thyristor or a transistor, and 4 is an electromagnetic switch which is main switching means and is turned on by excitation of an excitation coil 41. 5 and 6 are first and second diodes, respectively, 7 is a resistor, 8 and 9 are electromagnetic switches whose contact directions are switched by excitation of excitation coils 81 and 91, respectively; This is an electromagnetic switch for configuring a forward/reverse excitation current switching circuit that switches the connection direction and switches the excitation direction of the field winding. In the electromagnetic switches 8 and 9, the movable contacts are normally in contact with the lower fixed contacts shown in the figure, which are normally closed contacts. Reference numeral 10 denotes a starting switch comprised of a key switch, an accelerator operation switch, or the like. 11 is a forward/reverse changeover switch having a neutral terminal 12, a forward terminal 82, and a backward terminal 92; 13 and 16 are transistors; 14 and 17 are surge absorbers such as varistors; 15 is a drive circuit; and 83 and 93 are diodes. It is.

Next, the operation of the electric vehicle motor control device according to the present invention will be explained with reference to the illustrated embodiment.

First, the transistor 13 becomes non-conductive and disconnects the motor 2 from the main circuit when the chopper device 3 is in an abnormal state such as a short circuit during startup, or when the chopper device 3 is in an abnormal state such as being unable to shut off during operation. This is a safety device to stop the vehicle. The drive circuit 15 is for driving the transistor 16, and normally operates to make the transistor 16 conductive when the start switch 10 and the forward/reverse selector switch 11 are closed. However, when the starting switch 10 and the forward/reverse selector switch 11 are closed, a voltage with a polarity opposite to that shown in the diagram is induced in the armature 21, and the current flowing through the motor 2 exceeds the specified value. It operates to render transistor 16 non-conductive when detected. Also, the chiyotsupa device 3 is. It operates intermittently in response to a control signal generated in response to a signal corresponding to the movement of an output instruction device such as an accelerator pedal (not shown), and applies an average voltage ranging from several percent to 100% of the power supply voltage to the electric motor 2. The speed is controlled by applying a voltage (sometimes with a bypass contactor arranged to short-circuit the chopper device 3). In addition, the aforementioned control signal generating device (not shown) may be attached with a device that gradually increases the voltage applied to the motor using a chopper device, which is a device called a known soft start device when the vehicle is suddenly accelerated by an accelerator pedal or the like.

Close the start switch 10 and turn the forward/reverse switch 1
When the switch 1 is closed to the forward side 82 (or reverse side 92), if the result of the start-up check of the chopper device 3 is normal, the transistor 13 is made conductive. Then, the exciting coil 81 (or 91) is excited, and the movable contact of the switch 8 (or 9) is closed to the fixed contact side at the top of the figure. Next, the chopper device 3 gradually starts chopping operation in response to a control signal from the control device (not shown). From this point on, the drive circuit 15 checks the polarity of the voltage between both terminals of the armature 21 and the magnitude of the current in the motor 2. During power running, a voltage of the polarity shown in the figure is induced between both terminals of the armature 21, so the transistor 16 is made conductive, the exciting coil 41 is energized, and the main switch means 4 is closed. As a result, the motor 2
One side of the diode 6 is directly connected to the power source 1, and the chopping action of the chopper device 3 controls the speed of the motor 2 when it is powered. At the same time, the second diode 6 is connected in inverse parallel to the circuit of the motor 2 and operates as a flywheel diode. There are also cases where the chopper 3 is short-circuited by closing the aforementioned bypass contactor (not shown) to apply the full voltage of the DC power source 1 to the motor 2. In this way, speed control is performed from low to high speeds when an electric vehicle such as a battery-operated crimp is powered. Now, for example, when the vehicle is powered forward through the above-mentioned process, the forward/reverse switch 11 is turned on in order to brake at a certain point in time.
When switching from side 82 to side 92, i.e., from forward to reverse, both transistors 13 and 16 become non-conductive once, and the main switch means 4 remains open, with the movable contacts of the electromagnetic switches 8 and 9 both contacting the lower fixed contacts, but the transistor 13 is made conductive after it is confirmed that there is no abnormality in the chopper 3. Then, as the excitation is switched from coil 81 to 91, the movable contact of the electromagnetic switch 8 closes to the lower fixed contact side and the movable contact of 9 closes to the upper fixed contact side, and the chopper 3 starts chopping again. At this time, the chopper 3 is controlled by a control signal from a control device (not shown), and starts chopping from an output smaller than the output commanded by the accelerator, etc., and gradually increases the output to the commanded amount. At this time, the connection direction of the field winding 22 in the motor 2 is switched, and since the chopper 3 is chopped, the direction of the field magnetic flux is switched by the current passing through the resistor 7 from the power source 1, and while the vehicle is moving forward due to inertia, an electromotive force in the direction opposite to that shown in the figure is generated in the armature 21, and the motor 2 operates as a generator.
The first diode 5 is short-circuited through the second diode 5, and dynamic braking is performed, and the current flowing through the closed circuit increases. Next, when the chopper 3 becomes non-conductive,
When the generated voltage of opposite polarity to that shown in the figure generated in the armature 21 is greater than the total voltage of the power source 1, the current generated by the electromagnetic energy of the generator circuit flows through a closed circuit of the armature 21 → the second diode 6 → the power source 1 → the first diode 5 → the field winding 22, thereby performing regenerative braking.
In this case, and also when the generated voltage of the armature 21 becomes lower than the total voltage of the power source 1, at the same time, a part of the electromagnetic energy of the generator 2 generates a current that shunts through the closed circuit of the armature 21 → diode 6 → resistor 7 → field winding 22, and this electromagnetic energy is consumed in the resistor 7, thereby performing a dynamic braking operation. During this time, the drive circuit 15 detects the direction of the electromotive force induced in the armature 21 during forward rotation by the field flux generated by the current flowing through the field winding 22, thereby making the transistor 16 non-conductive during the braking period and maintaining the main switch means 4 in an open state. During the dynamic braking by the above-mentioned short circuit via the second diode 5, while the chopper 3 is conductive, the braking torque is controlled by controlling the current flowing through the chopper 3 to a specified value. Once dynamic braking has been performed by short-circuiting through the second diode 5, transition from dynamic braking to regenerative braking and further in the reverse direction can be achieved by controlling the conduction or non-conduction of the chopper 3. When the vehicle speed subsequently decreases and the generated voltage of the generator 2 decreases to the point where it is no longer possible to flow the specified current, the drive circuit 15 causes the transistor 16 to conduct, closing the main switch means 4 and shorting out the resistor 7. As a result, the vehicle comes to a complete halt and starts to move backwards. From then on, the armature 2
Since a voltage in the illustrated direction is induced in the second switching means 1, the transistor 16 continues to be conductive and the main switching means 4 is kept in the on state.
The diode 6 functions as a flywheel diode for the motor 2. As can be seen from the above explanation, during the power generation and regenerative braking period when the main switch means 4 is open, the field magnetic flux for generating an electromotive force of a reverse polarity in the armature 21 so as to generate a braking current is supplied from the power source 1 to the field winding 2 through the resistor 7.
Since the excitation current is obtained from the excitation current supplied to the power supply 2, there is no need to provide a separate excitation winding for external excitation and associated circuits and auxiliary elements. The surge absorbing devices 14 and 17 shown in the figure are for absorbing surge voltages generated by the exciting coils 81, 91 and 41 or wiring inductances, etc., at the moment when the transistors 13 and 16 are made non-conductive, thereby protecting the transistors 13 and 16. In the circuit shown in the figure, the chopper device 3 is connected to the negative side of the power supply 1, and the main switch means 4 is connected to the negative side of the power supply 1.
and resistor 7 are connected to the positive side of power supply 1, but it is clear that the same action and effect can be obtained even if the positions are reversed, or if the forward/reverse excitation current switching circuit and armature 21 are swapped up and down.

As explained above, according to the present invention, the electric motor 2
A parallel circuit of main switch means 4 and resistor 7 is provided in series with the circuit of
By shorting the resistor 7 and connecting the motor 2 and the chopper device 3 in series to the power source 1, the chopper device 3 is connected.
Power running control is carried out by this, and at this time, the second diode 6 is connected in antiparallel to the circuit of the electric motor 2 and acts as a flywheel diode. Next, during braking, the main switch means 4 is cut off and initial excitation is performed by the resistor 7, so that the electric motor 2 can be sufficiently operated as a generator even from relatively low speed rotation. Note that during braking, a part of the electromagnetic energy of the generator 2 is divided into the field winding 22 and the resistor 7 as a braking current. However, this resistor 7 is short-circuited as soon as the vehicle starts powering, so no power loss occurs during powering. Further, the first diode 5 operates as a short-circuiting diode for the generator circuit in the case of normal dynamic braking, and is not added specifically for regenerative braking. Rather, since the braking current is not a short-circuit current due to plugging braking but a regenerative braking current, the capacitance of the first diode 5 can be small. Further, since the armature current and the field current are always equal, rectification as a generator is good and the size of the electric motor 2 can be reduced. After all, according to the invention of the present invention, it is possible to save energy simply by adding a small-capacity resistor 7 in parallel to the main switch means 4, and an improved motor control device that can downsize the motor can be obtained. This has an excellent effect.

[Brief explanation of the drawing]

The accompanying drawing is a circuit diagram of a motor control device according to the present invention. 1 is a DC power supply, 2 is an electric motor (generator during braking), 3 is a chopper device, 4 is a main switch means,
5 and 6 are first and second diodes, respectively, 7 is a resistor, and 8 and 9 are electromagnetic switches as main stages for forward/reverse switching.

Claims (1)

[Scope of utility model registration request] One end of the series circuit of the forward/reverse excitation current switching circuit of the DC series motor and the armature and one end of the parallel circuit of the main switch means and the resistor are connected at a first connection point, and the other end of the parallel circuit The other end of the series circuit of the forward/reverse excitation current switching circuit and the armature is connected to one main terminal of the chopper device at a second connection point, and the chopper device is connected to one end of the DC power source. The other main terminal of the device is connected to the other end of the DC power supply, and a first diode is connected between the first connection point and the other main terminal of the chopper device, and the first diode is connected to the other end of the DC power supply. A second diode is connected between the second connection point and one end of the DC power supply. A motor control device for an electric vehicle configured to supply excitation current for a DC series motor.