JP2671308B2 - Braking device for electric vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric vehicle, and more particularly, to an electric vehicle that prevents abnormal braking operation and burnout of a brake lining in a non-excitation actuated automatic magnet brake. The present invention relates to a braking device. [Prior Art] FIGS. 3 to 4 show a conventional example. Of these, FIG. 3 shows an example of a control circuit in a conventional automatic magnet brake device, and FIG. 4 shows signals of respective parts in the circuit of FIG. FIG. 3 shows the case of the 2CH system having two drive motors. The conventional example shown in FIG. 3 is CH
An AND circuit 1 that calculates the logical product of the accelerator signals for the motors of CH1 and CH2, an integrating circuit 3 including a diode 2, a resistor R ₁ and a capacitor C ₁ and the output of this integrating circuit 3 is compared with a fixed threshold value. Output of the integrator circuit 6, an integrator circuit 6 including a diode 5, a resistor R ₂ and a capacitor C ₂ , an oscillator 7 for generating a reference triangular wave (or a sawtooth wave), and an output of the integrator circuit 6. And a reference triangular wave to generate an output, a AND circuit 9 for calculating a logical product of the output of the comparator 4 and the output of the comparator 8, a magnet brake coil 10, a battery 11, and a magnet. A transistor 12 that controls the energization of the brake coil 10 from the battery 11 and a power supply circuit 1 that supplies power Vcc to each part.
It is composed of 3 and. In the conventional device shown in FIGS. 2 and 3, when the accelerator is not stepped on, two driving motors are used.
The accelerator signals of CH1 and CH2 are "H" indicating neutral. Output signal v ₁ of the AND circuit 1, "H" indicating the stop time of both the accelerator signal are both "H", and "L" indicating the traveling otherwise. Signal v ₁ is diode 2
A signal v ₂ is generated through the integrator circuit 3 and the rising edge with a rising delay according to the time constant R ₁ C _{1 at the} rising edge and immediately falling at the falling edge. The comparator 4 outputs the signal v ₄ which becomes “L” when the signal v ₂ exceeds the threshold value v ₃ and becomes “H” otherwise.
The signal v ₄ passes through the diode 5 and the integrator circuit 6 and has a time constant R ₂ C ₂ at the time of rising, with a rising delay, and produces a signal v ₅ which immediately falls at the time of falling. The comparator 8 outputs the signal v ₆ of the reference triangular wave of the oscillator 7 to the signal v ₅
A signal v ₇ that is “H” when the value exceeds and is “L” otherwise is output. The AND circuit 9 outputs a signal v ₈ which is the logical product of the signals v ₄ and v ₇ . Transistor 12 is rendered conductive in accordance with the signal v _8, whereby a current from the battery 11 to the magnet brake coil 10 is energized by the flow. The signal v ₈ is as shown in FIG. 4, and the magnet brake is of the non-excitation actuated type. Therefore, when the vehicle is stopped, the vehicle is in a non-excited state and is in a braking state, and when the vehicle starts traveling, the vehicle is fully conducted for a certain period of time, and the entire voltage is applied to the magnet brake coil, the brake disc is attracted and the brake is turned off. After that, the chopping operation is started and the current is intermittently energized, the non-conduction period gradually increases, and finally the intermittent energization of about 50% duty is performed to maintain the brake off state during running. To be done. This operation is performed because the magnet brake has a hysteresis characteristic.
When (V), the minimum on-voltage is 0.7E, and the maximum off-voltage is 0.3E. [Problems to be Solved by the Invention] A non-excitation actuated type magnet brake is excellent in terms of fail-safe because it is always brought into a braking state when there is no voltage for some reason. However, in order to have a predetermined braking torque, about twice the electric power is required as compared with the excitation type, and the cost increases. Therefore, it is generally not possible to allow the braking torque to have a sufficient margin. The fourth brake that is currently running and the brake is released
In the state shown by A in the figure, if the brake disc is opened (brake on) for some reason despite being energized, the chopping operation is performed, and therefore the brake off state is not restored. On the other hand, since there is no margin in the braking torque, a situation may occur in which the vehicle continues to run in the braking state even if the speed is slightly reduced. When this happens, the vehicle cannot be returned to normal unless it is temporarily stopped as shown by B in FIG. The lining (facing) will be burnt out. Note that the above problems are the same when the number of drive motors is only one. An object of the present invention is to solve the problems of the prior art as described above, and to brake an electric vehicle having a non-excitation actuated type magnet brake which adopts a chopping operation system. It is an object of the present invention to provide a braking device for an electric vehicle that can automatically return to a normal state when the brake is turned on for some reason during traveling and prevent burnout of the brake lining. Is. [Means for Solving the Problems] A braking device for an electric vehicle according to the present invention is a non-excitation type, and after the brake coil is turned off by continuous energization of the brake coil, the energization of the brake coil is interrupted intermittently. In a braking device for an electric vehicle equipped with a magnet brake that maintains a brake off state by a chopping operation, an overcurrent detection unit that generates an overcurrent detection signal when the drive current of a drive motor becomes an overcurrent state, and the overcurrent detection unit. Control means is provided for prohibiting the chopping operation by the detection signal and for continuously energizing the brake coil to restore the brake-off state. [Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Here, the same symbols are used for the same configurations as the above-described conventional example. The embodiment shown in FIG. 1 is an overcurrent detection circuit including a 2CH drive motor 14 and 15 including a drive circuit, a motor current detection resistor R ₃ , a threshold voltage setting resistor R ₄ and a comparator COM. 16 and 17 and diodes 18 and 19 are provided. FIG. 2 shows signals at various parts in the circuit of FIG. 1 and explains the operation of the magnet brake device of the present invention. When the transistor Tr is turned on, the drive motors 14 and 15 are supplied with current from the battery 11 to rotate the motor M, thereby rotating wheels of an electric vehicle or the like to generate a driving force. . During operation of the drive motors 14 and 15, a voltage is generated in the current detection resistor R ₃ in each of the overcurrent detection circuits 16 and 17. Overcurrent detection circuit 1
In 6 and 17, the voltage of the resistor R ₃ is compared with the set voltage of the threshold setting resistor R ₄ to generate output signals v ₁₁ and v ₁₂ . The signals v ₁₁ and v ₁₂ are "L" only in the overcurrent state of the drive motors 14 and 15 as shown in FIG. 2, and are "H" in other cases. In the overcurrent detection circuits 16 and 17, the comparator COM is an operational amplifier, and its output resistance is sufficiently smaller than the resistance R ₂ in the integration circuit 6. Therefore, when either of the signals v ₁₁ and v ₁₂ becomes "L", the output signal v5 of the integrating circuit 6 is lowered to "L". Therefore, the output signal v ₇ of the comparator 8 accordingly becomes “H”, and therefore the drive signal v ₈ for the transistor 12 also becomes “H” during this period. Therefore, when abnormal release of the brake disc occurs at point A in FIG. 2, a signal that detects the overcurrent of the drive motor based on this is used to temporarily energize the brake coil continuously and brake. The control is performed so that the chopping operation is resumed after the overcurrent state is canceled after the off state. Therefore, as shown by B → C in FIG. 4, the normal state is immediately restored without controlling the magnet brake by the stop and restart operations. [Effects of the Invention] As described above, according to the present invention, in the braking device for an electric vehicle having a non-excitation actuated magnet brake, when an abnormal state in which the brake is turned on during traveling occurs, the brake is automatically turned off. Since it returns to the normal state by returning to, the abnormal reduction of the magnet supply voltage is effectively prevented from abnormal braking during running caused by unstable brake disc adsorption due to an excessive gap between the brake coil part and the disc part. At the same time, it is possible to provide a conventional excellent control device for an electric vehicle that can prevent the brake lining from burning.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing signals at respective parts in the circuit of FIG. 1,
FIG. 3 is a diagram showing a circuit configuration of a conventional magnet brake device, and FIG. 4 is a time chart showing signals at respective parts in the circuit of FIG. 1,9 …… AND circuit, 2,5,18,19 …… Diode, 3,6…
… Integrator circuit, 4,8 …… Comparator, 7 …… Oscillator, 10 …… Magnet brake coil, 11 …… Battery, 12 …… Transistor, 13 …… Power supply circuit, 14,15 …… Drive motor, 1
6,17 …… Overcurrent detection circuit.

Claims (1)

(57) [Claims] A non-excitation type of electric vehicle equipped with a magnetic brake that turns off the brake by continuously energizing the brake coil and then maintains the brake off state by a chopping operation that intermittently interrupts the energization of the brake coil. In a braking device, an overcurrent detection unit that generates a predetermined overcurrent detection signal when the drive current of a drive motor is in an overcurrent state, and the chopping operation is prohibited by the overcurrent detection signal to continuously energize a brake coil. And a control means for returning to the brake-off state by performing the above-mentioned operation.