JPS60134703A - Brake control circuit of dc electric railcar - Google Patents

Abstract

PURPOSE:To obtain a decision for controlling a suitable return by deciding the return of a plugging from the regeneration by detecting an armature current at regenerative braking time. CONSTITUTION:Contactors 2A, 3A are switched complementarily reversely at a plugging time to flow a plugging current to an armature 1. When the current of a diode 10 or 11 is a constant value or higher and continued for one period or longer of a chopper main circuit, the operation of a chopper controller is suppressed, and a regenerative switching electromagnetic cntactor 7 is controlled OFF. When a contactor 7A is separated, a regenerative state detector 24 starts regenerative braking due to the chopper operation. A plugging return controller 33 excites the contactor 7 when the rotation of the armature 1 falls so that the regenerative current becomes a set value or lower, and returns to the plugging brake.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a brake control circuit for a DC electric vehicle using a DC motor as a drive source, and particularly to a brake control circuit that uses both plugging and regeneration.

(Prior Art and Problems) Plugging braking is generally widely used for braking DC electric vehicles such as battery forklifts, but recently, various methods have been proposed in which plugging braking is combined with regenerative braking. In regenerative braking, the electric motor acts as a generator when switching between forward and backward motions, converting the braking energy of the electric vehicle into power generated by the electric machine and recovering it as battery charging energy. This regenerative braking does not work when the rotational speed of the electric motor is lower than the rotational speed that can be achieved as a generator, and the vehicle coasts.

Therefore, conventionally, when switching between forward and reverse, a pre-excitation current is passed through the field coil (field) of the motor, and it is determined from the current value of the motor whether the motor can function as a generator or not, and regenerative braking and plugging braking are selectively used. something is proposed. (For example, JP-A-57-6502).

In this conventional method, preliminary excitation is performed to determine plugging and regeneration, and to switch the regenerative braking contactor to the regenerative side. The current is decreasing. Therefore, at the time when the judgment output for switching the contactor to regeneration is obtained, the field current is considerably larger than the current value required to actually enter regeneration, and the amount of energy that can be regenerated from the 111 motor is small and is consumed by plugging. There was a problem in that the contactor needed to have a large contact capacity, which resulted in a large amount of energy being collected, which prevented efficient energy recovery.

In order to solve these problems, the applicant has also proposed a system that stops the chopper operation by detecting the plugging state, waits for the motor's power generation flow to decrease, forms a regenerative circuit, and then performs pre-excitation to start the regenerative operation. ing.

In this improved circuit, when the vehicle speed decreases due to regenerative braking, the regenerative braking becomes insufficient in torque, so the system returns to plugging braking. In order to determine the return from regeneration to plugging, the reduction in power generation capacity of the 11L motor was detected based on the commutating capacitor voltage of the chopper main circuit and the chopper conductivity, which are correlated with the reduction in the field's direct current.

The former type of detection based on the commutating capacitor voltage commutates the chopper main thyristor with the oscillating current generated by the commutating capacitor and the axle, so the detected voltage will differ depending on the constants of the capacitor and the axle, and the control circuit This increases the amount of effort required for adjustment, and in some cases requires design changes that change the circuit specifications. The latter detection based on chopper conduction rate has the same drawback as the former because the correspondence between braking torque and conduction rate changes when the motor capacity and characteristics change. In other words, it is difficult to provide generality to the control circuit using conventional detection means, and unless appropriate adjustments or design changes are made, a smooth transition of braking torque from regeneration to plugging control cannot be achieved, resulting in poor deceleration feedback. There was a problem with the ring going bad.

(Object of the invention) The present invention has been made in view of the above-mentioned circumstances.
It is an object of the present invention to provide a braking control circuit for a DC electric vehicle that can obtain an appropriate judgment for controlling the return from regeneration to plugging.

(Summary of the Invention) The present invention is characterized in that a return from regeneration to plugging is determined by directly detecting the current flowing through the armature during regenerative braking.

(Embodiment) The figure is a circuit diagram showing an embodiment of the present invention. The field coil 4 is connected to the armature 1 via the forward march, the contactor 42 of the magnetic contactor 2, or the contactor 3A of the reverse magnetic contactor 3.
are connected in series, and further a chopper main circuit 5 is connected in series. One of the contactors 2A and 3A is switched from the illustrated state when the electric vehicle is switched between forward and reverse, and the field coil 4
Switch the current polarity. The conductivity of the chopper main circuit 5 is controlled by a later-described chopper control circuit according to the amount of accelerator pedal depression, etc., and controls the current of the electric motor provided with the contactors 2A and 3Ar.

A contactor 7A of a regeneration switching electromagnetic contactor 7 is provided between the armature 1 and the battery 6 serving as its DC power source. In the contactor 7A, the normally open contact a is connected to the armature 1 side, and the normally closed contact is connected to the pre-excitation switch means 8 side, so that the connection between the battery 6 and the armature 1 is disconnected during regeneration. The switch means 8 has transistors Tr and f as switching elements, and has a pre-excitation current setting resistor 9 in series, which is connected to the other end of the armature 1, and is connected to the contact point of the battery 6 during regeneration. A pre-excitation current path to the field coil 4 is formed via bt.

Diodes 10 and 11 are provided from both ends of the field coil 4 to the positive electrode side of the battery 6, respectively. These pair of diodes i0 and 11 are used to form a circulating current path in the armature 1 or to form a flywheel current path between the armature 1 and the field coil 4, depending on the switching state of the contactors 2A and 3A during the OFF period of the chopper main circuit 5. It is used for both purposes. A regeneration diode 12 is provided with a shunt resistor 12A in series at one end of the armature 1 (on the contactor 7A side) and on the reference potential side (negative electrode side) of the battery 6. This diode 12 is used to form a charging path for the battery 6 and an excitation current path for the chopper main circuit 5 with the generated current of the DC motor during regeneration. The shunt resistor 12A detects the diode 12 as a suitable lftft electronic current pressure signal, which is converted into a return current detection signal for regenerative operation and regeneration to boolaging as described below.

A contactor 13 is installed in parallel with the chopper main circuit 5, and the contactor 13 is provided for maximum speed operation in which the entire voltage of the battery 6 is applied to the electric motor in place of the chopper.

In this main circuit configuration, during normal operation (power running), the contactor 7 is connected to the forward/reverse selector switches 14F and 14R.
When energized, the contactor 7A is connected to the contact a side, the two contactors are connected to the contact a side, and the conductivity of the chopper main circuit 5 is controlled p'l11 according to the amount of accelerator depression, and forward variable speed operation is performed. It will be done. On the other hand, when the contactor 3A is connected to the contact a side, reverse variable speed operation is performed. During this normal operation, during the OFF period of the chopper main circuit 5, the diode 1O acts for the flywheel and the diode 11 acts for the circulating current in forward movement, and the diodes 10 and 11 act in the opposite manner in reverse movement.

Next, when plugging, contactor 2 is
A and 3A are switched complementary to each other in the opposite direction, the field coil 4 is switched to the reverse direction, nine currents are caused to flow in accordance with the chopper conductivity, and an electromotive force is generated in the armature 1 in the opposite direction. This electromotive force is transferred to a diode 10 or 11 inserted in parallel with the armature 1.
By short-circuiting, a plugging current flows through the armature 1, and as a result, plugging braking with a strong braking torque determined by the product of the field current flowing through the field coil 4 and the armature current is applied. At this time, the kinetic energy acting on the armature 1 is dissipated in the nt armature winding, the diode, the brush, and the contact resistance between the brush and the commutator. Therefore, plugging braking not only damages the surfaces of the brushes and commutator, but also wastes kinetic energy.

Therefore, instead of plugging, a regeneration control circuit is provided with the configuration shown below to enable regenerative braking with a relatively small armature current and to use both plugging and regenerative braking.

As a regeneration control circuit, the main circuit is provided with the contactor 7A, the switch means 8, the resistor 9, and the diode 12 as shown in the figure, as described above. A current detection circuit 15 is provided between the cathodes of the diodes 10 and 11 and one end of the armature 1 (field coil side), and detects a circulating current flowing from the armature 1 to the diode 1O or 11. Comparator 16
is a comparison input using the detected current of the current detection circuit 15 as a voltage signal, and a voltage VRI corresponding to the current required for regenerative braking is given as a comparison reference, and it is detected that the circulating current of the armature 1 is at the regenerative level. . The timer 17H is used to determine whether the detection output of the comparator 16 continues beyond the time limit of the timer, and appears in the circulating current of the armature 1 as a current accompanied by a spike current when the chopper main circuit 5 is turned off even during normal operation. Therefore, in order to distinguish between normal operation and plugging, the time period is set to be longer than one cycle of the chopper main circuit.

Therefore, the plugging state detection circuit consisting of circuits 15 to 17 obtains an output that determines the plugging state when the current of the diode 10 or 11 is above a certain value and continues for one cycle or more of the chopper main circuit. In other words, the plugging state is quickly detected every cycle of the chopper main circuit 5 by switching the contactors 2A and 3A.

Flip-flop 18 is set by the plugging detection signal output from timer 17 and stores the plugging state. The chopper stop circuit 19 is a set of flip-flops 18 that suppresses the operation of a chopper control circuit, which will be described later, and prevents the motor current from flowing until preliminary excitation. The timer 20 operates to measure time by setting a flip-flop 18, and the time limit is determined by the chopper stop circuit 19 stopping the chopper operation, that is, stopping the electric motor from generating electricity. is set to the required time. The flip-flop 21 is set by the output of the timer 2O, and obtains the set output as a regeneration command.

The driver 22 turns off the control transistor 23 of the regeneration switching electromagnetic contactor 7 using the set output of the flip-flop 21 .

Therefore, the switching means of the regeneration switching electromagnetic contactor 7 consisting of circuits 18 to 23 stops the operation of the chopper main circuit in response to the plugging state detection signal, and after the time when the generated current of the DC motor decreases, the regeneration switching electromagnetic contactor 7 contactor 7 of contactor 7
Let A fall off and switch the main circuit to regeneration mode. In this switching, after waiting for the generated current to decay, the contactor 7A
By dropping the contactor 7A, the breaking current of the contactor 7A is small, and the capacity of the contactor 7 can be small. This is because the longer the timer 20 is set, the smaller the cut-off current becomes, but the time it takes to switch from plugging to regeneration becomes longer, and during this time there is a pause period for plugging braking and regenerative braking, which affects the braking feeling. Since this leads to a decrease in the braking force, the time period is determined based on the balance between the cutoff current of the contactor 7A and the braking feeling.

The regeneration state detection circuit 24 detects detachment of the contactor 7A based on the voltage generated by the battery 6 at its contact point.

This detection signal is taken out at the change to the high level Kara T:1- level. The pre-excitation timer 25 starts counting with the detection output of the detection circuit 24, and sets the flip-flop 26 at the rising edge of the clock. This flip-flop 26 resets the flip-flop 18 with its set output. Therefore, by resetting the flip-flop 18, the chopper operation stop of the chopper control circuit n is canceled through the chopper stop circuit 19.

The flip-flop 26 is provided to limit one regeneration operation to one operation of forward/reverse switching, and after being set by the timer 25 upon detection of the regeneration state, the reset circuit 28 performs an initial reset and forward/reverse operation. The set state is maintained until reset by operating the direction switches 14F and 14H, and the flip-flop 18 is forcibly reset.

The chopper control circuit 27 has a variable current source Cl-4 whose output current is controlled by a potentiometer PM corresponding to the amount of accelerator depression, and the voltage of the capacitor CT charged with this output current is the set voltage of the programmable unijunction transistor PUT. When the voltage reaches 9, the output test circuit GC of the transistor PUT ignites the main thyristor SMi of the chopper main circuit 5. As a result, the transistor PUT fires the main iris switch SM=i at a period corresponding to the amount of depression of the accelerator. Then, the chopper main circuit 5 turns on the auxiliary thyristor SS after a certain period of time from the firing of the main thyristor SMO, and performs forced commutation of the main thyristor SM by the commutation capacitor C1. Therefore, the chopper main circuit 5
conduction rate control is performed such that the on-period has a constant width and the off-period changes depending on the amount of accelerator depression. Such a chopper control circuit is provided with a transistor Tr that can stop the operation of the variable current source CI. This transistor Tr is turned off in response to a detection signal from the regeneration state detection circuit 24 to suppress the operation of the current source CI. Therefore,
Capacitor CT is not charged by current source CI.

As described above, the chopper operation by the current source CI of the chopper control circuit is suppressed by the regeneration width detection by the regeneration state detection circuit 24, and the chopper operation is canceled by the chopper operation stop circuit 19 (charging of the capacitor CT) by the output of the pre-excitation timer 25. permissible) is made.

In this state, the regenerative braking output section 29 is activated by the output of the detection circuit 24, and the transistor Tr, which is on during plugging, is turned off, and the capacitor CT of the chopper control circuit 27 is charged with the current determined by the resistor R□. Have them do the action. In this chopper operating state, the pre-excitation timer 25 turns on the switch means 8 for that period of time to cause the field coil 4 to turn on.
The pre-excitation current is controlled to flow. This pre-excitation current is battery 6 → contactor 7A → switch means 8 → resistor 9
The flow follows the chopper operation in the following path: → 2 contactors (or 3A) → Field coil 4 → Contactor 3A (or H2A) → Chopper main circuit 5.

The armature 1 acts as a generator by pre-excitation only for the tie 1250 time period, and after the pre-excitation ends, regenerative braking is performed.

This regenerative braking is applied to armature 1 during the off period of the chopper main circuit.
The batch IJ 6 f: is charged by passing the generated 11L current through the contactor 2 or 3A → diode IO or 11 → battery 6 → diode 12 (shunt resistor 12A), and during the ON period of the chopper main circuit 5, the armature 1 The origin of W,
[Flow contactor 2A or 3A → Field coil 4 → Contactor 3A or 2A → Chopper main circuit 5 → Diode 12
(Shunt resistor 12A) Flow through the O path to excite,
Braking energy is recovered as regenerative power to the battery 6 while repeating battery charging and excitation.

In this regenerative braking, the regenerative acid flow detection circuit 30 amplifies the voltage signal of the shunt resistor 12A, and the comparator 31
compares the voltage of the potentiometer PM of the chopper control circuit n with the detection signal of the detection circuit 3O, and controls the output section 29 to be turned on or off. Therefore, the regenerative braking circuit consisting of 29 to 31 performs regenerative braking while controlling the conductivity of the chopper operation according to the degree of depression of the accelerator.

Similar to the circuit 30, the motor current detection circuit 32 amplifies the voltage signal of the shunt resistor 12A and uses it as a comparison input of the plugging return control circuit 33. The plugging return control circuit 33 has a comparator, and a voltage corresponding to the armature current that requires returning from regeneration to plugging is applied to its comparison standard (1), and when the armature current decreases to below this comparison standard VL. The flip-flop 21 is reset to .

Therefore, when the regenerative braking progresses and the armature 10 revolutions decreases, the plugging return control means 32 and 33 detects from the armature current (field current) as a decrease in the power generation capacity of the motor. Reset the driver 22, turn on the transistor 23, and return the contact 4Z7Af to the contact a side to return to plugging braking. 34 is a control power source.

(Effects of the Invention) According to the present invention, in the return control from regeneration to plugging,
To detect a decrease in the power generation capacity of the motor, the armature current that correlates to the braking torque is directly detected in order to use it as a detection signal for a current detector such as a shunt resistor (12A) installed in the current path flowing through the armature during regeneration. By detecting this, a determination for appropriate return control can be obtained. In other words, with conventional detection based on commutator capacitor, pressure, and chopper conductivity, the correspondence between braking torque and these detection signals changes due to changes in the specifications and design of the motor, etc., and the return control circuit needs to be changed or readjusted. In contrast, in the present invention, the conventional problem can be solved by determining - from the armature current that is directly connected to the braking torque.

In addition, in the present invention, the 11 current detection shunt resistor (12A) for regeneration control can also be used for plugging return control, and 'Wj' for plugging return control.
There is no need to provide a special Lf&detector.

Furthermore, in the present invention, since a current detector (a shunt resistor in the embodiment) for armature current detection is provided in series with the regenerative flywheel 12, there is no current detection in the plugged state, which eliminates the risk of incorrect return control determination. It disappears.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. ■...'armature, 2...magnetic contactor for forward movement, 3...
・Magnetic contactor for reverse movement, 4... Field coil, 5... Chopper main circuit, 7... Magnetic contactor for regeneration switching, 8...
- Pre-excitation switch means, 12... Regeneration diode, 15... Electric θ(t detection circuit, 16... Comparator, 17, 20, 25... Timer, 19...
- Chopper operation stop circuit, 24... Regeneration state detection circuit, 27... Chopper control circuit, 28... Reset circuit, 33... Plugging return control circuit.

Claims (1)

[Claims] Plugging is controlled by switching the field coil polarity of a DC motor for driving an electric vehicle between forward and reverse, and the field coil is pre-excited by detecting the plugging state. In the braking control circuit of a DC electric vehicle, the iM current motor is regeneratively braked by the conductivity control of the chopper main circuit, and then returned to plugging braking when a decrease in the power generation capacity of the motor is detected due to regenerative braking. 1. A braking control circuit for a DC electric vehicle, characterized in that whether or not to return plugging is determined based on a detection signal from a current detector provided in a current path flowing through the coil.