JPS6352602A - Braking controller for electric automobile - Google Patents

Abstract

PURPOSE:To miniaturize and lighten a mechanical braking means by ON-OFF controlling a switching element so that said element supplies an induction motor with a dynamic braking DC power when it receives a fault signal of said switching element. CONSTITUTION:If the title apparatus is in good order, switches 18a, 20a, 22a are connected to an output terminal side of a function generator 16 for normal travel and respective semiconductor devices 28a, 28b, 30a, 30b, 32a, 32b of a power converter 26 are ON-OFF controlled so that a motor drive corresponding to a torque command T is performed. If a fault detector 44 detects any trouble, a defective semiconductor device is decided and a DC braking mode is selected. On the basis of said decision and selection, the fault detector 44 changes the switches 18a, 20a, 22a to an output terminal side of the function generator 46. Consequently, a switching signal for DC braking of a motor 42 is obtained as the output of comparators 18, 20, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake control device for an electric vehicle, and particularly to a brake INII+ control device that controls a drive motor using an electric braking force.

[Prior Art] An electric vehicle is provided with a power conversion section that converts battery power into alternating current and supplies it to a motor, and this power conversion section uses a semiconductor element as a switching element. .

However, the reliability of this semiconductor element has not yet been sufficiently ensured, and if the semiconductor element fails, it may cause problems in operation and create a dangerous situation. Is required.

Conventionally, mechanical braking means such as hydraulic brakes are generally used as emergency control means to safely stop a vehicle when a semiconductor element fails.

[Problems to be Solved by the Invention] However, when the safe stopping control of the vehicle in the event of a failure of the semiconductor element of the power conversion section relies solely on the braking force of a mechanical hydraulic brake, etc. as in the past, , mechanical braking means are designed without expecting electrical braking by the motor.

Therefore, even if electrical braking of the motor can be expected, the volume and weight of mechanical braking means such as a hydraulic brake are large.

That is, since the electric braking force unique to electric vehicles is not fully utilized, there is a problem in that the distance traveled by the vehicle on one charge is shortened due to the mm of the mechanical braking means.

The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the size and weight of the mechanical braking means by effectively electrically braking the drive motor when a switching element fails, thereby improving the vehicle performance. An object of the present invention is to provide an 11ftil braking device for an electric vehicle that can extend the mileage per charge.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a mino-J converter that converts battery power into alternating current using a plurality of switching elements and supplies the alternating current to an induction motor for driving a vehicle; and a switching element control circuit that controls each switching element on and off so that alternating current power according to a torque command determined based on running conditions is supplied to the induction motor. a failure detection unit that detects whether there is a failure in the switching element control circuit;
a braking signal generating section that controls on/off of each of the switching elements so that DC power for driving is supplied to the induction motor, and the induction motor is dynamically braked when a switching element fails.

[Operation] According to the above configuration, first, the failure detection section quickly detects a failure that occurs in each switching element, and supplies a signal indicating that there is a failure to the switching element control circuit.

By supplying this signal, a braking signal generator provided in the switching element control circuit is activated, and each switching element is controlled to be turned on or off so that DC power is supplied to the induction motor.

The induction motor supplied with DC power will be dynamically braked.

In this way, the induction motor can be effectively electrically braked in the event of a failure of the switching element, thereby making it possible to reduce the size and weight of the mechanical braking means.

[Embodiment] FIG. 1 is a schematic circuit diagram showing a preferred embodiment of the present invention, in which a vehicle control unit 1o generates a torque command T based on driving commands from a forward/reverse switch, an accelerator sensor, an accelerator switch, a brake sensor, etc. Output. The torque command T is supplied to the vector calculation unit 14 in the switching element control circuit. An operation is performed. This calculation result 14a is sent to a function generator 16 for normal running, and a sine wave corresponding to the torque command T is obtained in this function generator 16.

The output of the function generator 16 is a U phase whose phase is shifted by 120°,
The signals are supplied to one terminal of the comparator 18, 20, and 22 as the (1) phase and the W phase via switches 18a, 20a, and 22a, respectively.

The output of a comparison sawtooth wave generator 24 is supplied to the other terminal of each comparator 18, 20.22.

The output of each comparator 18, 20.22 is 18b, 2
Three pairs of semiconductor elements 32a forming the power conversion section 26 are connected to each other via 0b and 22b.

The signal is supplied to 32b, 30a, 30b, 28a, and 28b via their respective drive circuits, and serves as an on/off control signal for each semiconductor element.

Between the switches 18b, 20b, 22b and each of the three pairs of semiconductor elements, an inverter 34 is connected on one side of the branched line.
36 and 38 are provided to invert the output from each comparator, and are connected so that mutually inverted on/off signals are supplied to multiple pairs of semiconductor elements.

The voltage of the battery 40 is applied to the induction motor 42 via each drive circuit and semiconductor element, which are controlled on and off by the switching element control circuit 12.

Furthermore, this device is provided with a failure detection section 44, which is a feature of the present invention, and each semiconductor element 28a, 28b, 3 which is a switching element constituting the power conversion section 26
0a, 30b, 32a.

The presence or absence of a failure in each of 32b is detected.

Further, the switching element control circuit 12 is provided with a control signal generating section for controlling each semiconductor element so that DC power is supplied to the induction motor 42 when a semiconductor element fails. That is, in this example, a DC braking function generator 46 is provided, and its output terminal is connected to the switches 18a and 20a.
, 22a is the other switching terminal.

FIG. 2 is a flowchart showing the operation of the embodiment shown in FIG. 1. First, the presence or absence of a failure is detected in the failure detection section 44 (3101).

If there is no failure, ii control for normal running is performed (8102>. That is, in FIG. 1, switch 18a,
20a and 22a are connected to the output terminal side of the function generator 16 for normal running, and perform on/off control of each semiconductor element of the power converter 26 so that the motor drive corresponding to the torque command T is performed.

If there is no failure in each semiconductor element, this normal control is repeated.

When the failure detection unit 44 detects a failure, it determines the failed semiconductor element and selects a DC braking mode for dynamically braking the induction motor 42 by supplying DC power (8103 ). Based on this determination and selection, the failure detection unit 44 detects the switches 18a, 20
a, 22a, and each of these switches is switched to the output terminal side of the function generator 46.

Thereby, a switching signal for DC braking of the motor is obtained as the output of the comparators 18, 20, 22.

For example, if the semiconductor element 28a is short-circuited and has failed, the paired semiconductor element 28b needs to be left open, and the failure detection unit 44 switches the switch 22b to the LOW side by supplying a switching signal ( 5104)
.

Therefore, when the semiconductor element 28a is short-circuited, the semiconductor element 28b is always maintained in a non-conductive state. Further, semiconductor elements 30a and 32a are turned off, 30
By performing switching control so that b and 32b are turned on, ii! ! DC power is supplied to the induction motor 42, and dynamic braking is applied (3105).

Through the above operations, a failure of the switching element while the vehicle is running is quickly detected, and this failure detection signal causes circuit switching in the switching element control circuit 12 to effectively perform electrical braking of the induction motor 42. .

In this way, it is possible to automatically brake the induction motor 42, but the braking force can be made variable by changing the output of the function generator 46 in proportion to the depression rate or pedal force of the brake sensor. It is also possible.

[Effects of the Invention] As explained above, according to the braking control device for an electric vehicle according to the present invention, when the semiconductor element (switching element) used in the power conversion section fails while the vehicle is running, the induction Electrical braking force can be effectively applied to the motor, and the braking force that should be secured by mechanical braking means, such as a hydraulic brake, can be reduced to a small value.

That is, it is also possible to reduce the volume of the mechanical braking means and to reduce the weight of the weight.

This makes it possible to increase the travel distance of an electric vehicle on a single charge, or to downsize the driving battery while ensuring the same travel distance on a single charge as before.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram showing a preferred embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the embodiment shown in FIG. 12... Switching element control circuit 14...
Vector calculation unit 16...Normal running function generator 18.20.22...Comparator 26...
- Power conversion sections 18a, 18b, 30a, 32a, 32b --- Switching element 42 --- Induction motor 44 --- Failure detection section 46 --- DC braking function generator FIG.

Claims (1)

[Claims] (1) A power converter that converts battery power into alternating current using multiple switching elements and supplies it to the induction motor for driving the vehicle; and a power converter that converts battery power into alternating current and supplies it to the induction motor for driving the vehicle; a switching element control circuit that controls on/off of each of the switching elements so that the switching element is supplied to the electric vehicle; a braking signal generating section configured to control each of the switching elements on and off so that DC power for dynamic braking is supplied to the induction motor only when a signal indicating a failure is received from the failure detection section; A braking control device for an electric vehicle, which performs dynamic braking on an induction motor when a failure occurs.