JPH0435963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a braking control device for an electric vehicle that uses DC as a power source and includes a variable voltage variable frequency inverter and an induction motor.

A conventional electric car was constructed as shown in Figure 1. In the figure, 1 is a pantograph that collects and distributes DC voltage from overhead wires, and 2 is a controlled rectifying element such as a thyristor, which converts DC voltage into polyphase AC of any voltage and frequency, and generates polyphase AC through regeneration. A variable voltage variable frequency inverter (hereinafter referred to as inverter) that can also reversely convert alternating current to direct current, 3 is an induction motor whose speed is controlled by inverter 2 (hereinafter referred to as IM), 4 is the shaft end of IM3 A pulse sensor 5 is provided to detect the rotational frequency (f _M ), and 5 is a control device that outputs an ignition command for the inverter 2 according to power running and electric brake commands and forward and reverse commands.

In such an electric vehicle, the rotation direction of the IM3 is determined so that the electric vehicle travels in a predetermined direction based on a forward or reverse command from the driving vehicle or automatic driving device (hereinafter referred to as the driver). ,moreover,
The phase order of the output voltage of the inverter 2 is specified by the control device 5 so as to generate a rotating field in the same direction as the rotation direction of the IM 3.

In addition, to change the rotation direction of IM3 to the opposite direction,
Since the direction of the rotating field can be reversed, the phase relationship of the output voltage can be changed between the U, V, and W phases.
This is accomplished by reversing between the two output lines.
For example, in FIG. 1, if the phase order for forward movement is U-V-W, then reverse movement can be achieved by changing the phase order to U-W-V.

Next, the voltage and frequency of the inverter 2 are controlled by the control device 5 in response to a power running command from the driver so that a preset torque is achieved.

Generally, the torque (T) generated by the IM3 in a region where the slip frequency (f _S ) is small is expressed by equation (1).

T=k (V/f _I ) ² f _S ...(1) V: IM voltage f _I : Inverter frequency, that is, rotating field frequency f _S : Slip frequency k: Proportionality constant Here, the slip frequency (f _S ) is , the inverter frequency (f _I ) and the IM rotation frequency (f _M ) detected by the pulse sensor 4 and fed back to the control device 5.
This is the difference between the

f _S = f _I − f _M ...(2) From equation (1), the slip frequency (f _S ) during power running is
The inverter frequency (f _I ) is operated higher than the IM rotation frequency (f _M ) so that IM3 is positive.
generates positive torque.

Furthermore, when stopping a running electric vehicle, the driving vehicle issues a forward or reverse command as well as a brake command. This causes the control device 5 to control the inverter 2.
The phase order of the output voltage is determined to correspond to the driving direction based on the judgment of the driving vehicle, and the inverter frequency (f _I ) is set lower than the IM rotation frequency (f _M ) so that the slip frequency (f _S ) is negative. The electric brake is activated by generating negative torque in IM3.

Now, brakes for electric cars can be roughly divided into the above-mentioned electric brakes and mechanical brakes that apply mechanical frictional force. For example, mechanical brakes use the friction force generated by pressing brake shoes against the wheels.
This suppresses the rotation of the wheels. Due to its nature, this mechanical brake can be applied regardless of the direction in which the electric vehicle is traveling.

However, in the case of electric brakes, when a brake command is given while the electric vehicle is coasting in a predetermined direction, if a travel command is given in the opposite direction to the traveling direction, the slip frequency (f _S ) can be determined from equation (2). , since the inverter frequency (f _I ) and the IM rotation frequency (f _M ) have opposite rotation directions, the signs of the IM rotation frequency (f _M ) are opposite. Therefore, as shown in equation (3), the magnitude of the slip frequency (f _S ) becomes the sum of the absolute values of each frequency (f _I ) and (f _M ), and becomes excessive.

|f _S |=|f _I |+|f _M | ...(3) In this case, equation (1) does not hold. This is generally detailed in the literature and will therefore be omitted. This makes it impossible to generate negative torque beyond the stall torque point indicating the maximum torque on the IM torque curve shown in FIG. Therefore, the electric brake cannot be applied, resulting in a dangerous situation.

This invention was made in view of the above, and when a brake command is issued to the electric vehicle while the rotor of the induction motor is rotating in a predetermined direction, the rotation direction of the rotating field of the induction motor changes to the rotation direction of the rotor. To provide a brake control device for an electric vehicle, which controls the phase order of the output voltage of a variable voltage variable frequency inverter so as to match the phase order of the output voltage of a variable voltage variable frequency inverter.

The figures will be explained below.

In FIG. 3, (1) to (3) are the same as the conventional one.
Reference numeral 6 denotes a pulse sensor attached to the rotor of the IM 3, which is configured to output a signal indicating the IM rotation frequency (f _M ) and the rotation direction of the rotor. For example, as shown in FIG. 4, the signal in the rotational direction is generated by rotating pulse elements 6a and 6b, which are provided at different distances from the center of rotation, depending on which one passes the detection point first. Direction is detected. 7 is a control device that outputs a firing command to the inverter 2, and has a function of outputting an output voltage in a predetermined phase order according to a power running command and a forward or reverse command, and a function of outputting a brake command and IM3.
It has a function of outputting output voltages in a predetermined phase order based on a signal indicating the rotation direction of the rotor.

In the electric vehicle shown in FIG. 3, during power running, the control device 7 outputs a power running command and a forward or reverse command in order of the phase of the instructed output voltage, for example, in the case of a forward command, as U-V-W. , outputs a firing command for the inverter 2.

On the other hand, when a brake command is issued while the electric vehicle is running, that is, while the rotor of the IM 3 is rotating, the control device 7 outputs an inverter output based on this brake command and the rotation direction signal sent from the pulse sensor 6. The voltage phase order is determined and an ignition command is output to the inverter 2.

According to this invention, when a brake command is issued to the electric vehicle while the rotor of the induction motor is rotating, the variable voltage variable frequency inverter is activated so that the direction of rotation of the rotating field of the induction motor matches the direction of rotation of the rotor. Since the phase sequence of the output voltage is controlled, the electric brake can be safely activated even if, for example, a forward or reverse command cannot be output due to a mechanical failure, or if the driver makes a mistake in operating the direction of travel. can be done. This improves the reliability of the electric brake of an electric vehicle.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a brake control device for an electric vehicle.
FIG. 2 is a torque curve diagram of an induction motor, FIG. 3 is a configuration diagram showing an embodiment of the present invention, and FIG. 4 is a detailed diagram of a sensor for detecting the rotor rotation direction. In the figure, 2 is an inverter and 3 is an induction motor. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A braking control device for an electric vehicle having a pulse sensor 6 and a control device 7. Therefore, the operation is controlled. The pulse sensor 6 is attached to the rotor of the induction motor 3 and detects the rotation frequency and rotation direction of the rotor. The control device 7 controls the pulse sensor 6. a detection signal;
A brake command signal is input, and with respect to the rotational direction and rotational frequency detected by the pulse sensor 6, a rotational frequency that has a phase order of the rotational direction that matches the rotational direction and a negative slip frequency that generates an appropriate braking force. A braking control device for an electric vehicle which determines the following and outputs a control signal to a variable voltage variable frequency inverter 2.