JPH0793765B2 - Braking control circuit for DC electric vehicles - Google Patents

Abstract

PURPOSE:To effectively switch rapidly from plugging brake to a regenerative brake by switching to a regenerative brake when a plugging current is continued from a regenerative brake when a plugging current is continued from a regenerative brake enabling level or higher state to a regeneration brake for the prescribed time or longer. CONSTITUTION:When entering a plugging mode, a microcomputer 15 compares a plugging current Ip with a set value Is. When the state of Ip>=Is continues for the prescribed time Tp or longer, a regeneration possible is judged, a chopper operation is stopped, and a contactor 7A is separated to a regeneration side after a time required for attenuating the armature current. When the contactor 7A is separated, a preliminary excitation is performed, and is then moved to a regenerative brake. When a current is moved down to regenerative brake disabling level, the contact 7A of the contactor 7 is switched to a contact (a) side, and returned to a plugging brake.

Description

TECHNICAL FIELD The present invention relates to a braking control circuit for a DC electric vehicle that uses a DC motor as a drive source, and more particularly to a braking control circuit that uses both plugging and regeneration.

(Prior art and problems) As for braking of a DC electric vehicle such as a battery forklift, plugging braking is generally widely used, but recently, various combinations of plugging braking and regenerative braking have been proposed. In regenerative braking, when switching between forward and reverse, the electric motor acts as a generator to change the braking energy of the electric vehicle into the electric power generated by the electric motor and recover it as battery charging energy. In this regenerative braking, when the number of rotations of the electric motor is equal to or less than the number of rotations that is satisfied as a generator, the regenerative braking cannot be performed and the vehicle coasts.

Therefore, conventionally, when switching between forward and reverse, a pre-excitation current is passed through the field coil of the electric motor, and it is judged from the electric current value of the electric motor whether the electric motor is established as a generator, and regenerative braking and plugging braking are used properly. Some have been proposed (for example, JP-A-57-6502).

In this conventional method, it is determined from the magnitude of the current when pre-excitation is performed whether regenerative braking is possible or plugging braking should be performed, and if regenerative braking is possible, the contactor is switched to the regenerative braking side, and then the chopper is started. To do. Therefore, when switching the electric vehicle from forward to reverse, the accelerator is turned on to start the contactor on the regeneration side when starting in reverse from the stopped state where braking is completed until forward, and before the chopper is started. There was a problem that the excitation and the subsequent determination, the contactor switching, and the delay until the chopper was first turned on deteriorated the starting (reverse) feeling.

As a solution to such a problem, the applicant of the present application has already proposed that the chopper operation is stopped by the plugging state detection, the regenerative circuit is formed after the generation current of the motor is reduced, and then the pre-excitation is performed to perform the regenerative operation. There is.

In this improved circuit, if the regenerative braking is immediately detected by detecting the plaking state, the electric power generation capacity of the electric motor is low depending on the operating conditions such as the speed and inertial force of the electric vehicle, and the regenerative braking immediately returns to the plugging braking. Conceivable. In such braking control, there is a waste of electric power required for pre-excitation to enter regeneration, and braking torque changes by changing pre-excitation from strong braking to pre-excitation → regenerative braking from weak braking → within a short period of plugging braking. Changes greatly and the deceleration feeling becomes worse. In particular, if the power generation capacity necessary for regeneration cannot be obtained even by the pre-excitation, the pre-excitation returns to the plugging again, and the fluctuation of the braking torque becomes large.

(Object of the Invention) The present invention has been made in view of the above circumstances, and provides a braking control circuit for a DC electric vehicle that achieves efficient braking control with a small variation in braking torque when using both plugging braking and regenerative braking. The purpose is to provide.

(Summary of the Invention) The present invention performs regenerative braking only when it is determined by plugging braking that the power generation capacity of the motor is sufficient for regenerative braking. For this determination, the plugging current is equal to or higher than a level at which regenerative braking is possible and the chopper main circuit The feature is that the determination is performed quickly from the time ratio within one cycle.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention. A field coil 4 is connected in series to the armature 1 via a contactor 2A of the forward electromagnetic contactor 2 or a contactor A of the backward electric contactor 3, and a chopper main circuit 5 is further connected in series.
One of the contactors 2A and 3A is switched from the illustrated state by the forward / backward switching of the electric vehicle, and the current polarity of the field coil 4 is switched. The chopper main circuit 5 has its conductivity controlled by a chopper control circuit, which will be described later, in accordance with the accelerator depression amount and the like, and controls the electric current of the electric motor via the contactors 2A and 3A.

A contactor 7A of a regenerative switching electromagnetic contactor 7 and a shunt resistor 1A for detecting an armature current are provided between the armature 1 and a battery 6 serving as a DC power source. In the contactor 7A, the normally open contact a is connected to the armature 1 side via the shunt resistor 1A, and the normally closed contact b is connected to the pre-excitation switch means 8 side, and the connection between the battery 6 and the armature 1 during regeneration. Let go. The switch means 8 has a transistor Tr ₁ as a switch element, has a pre-excitation current setting resistor 9 in series, and is connected to the other end of the armature 1. During regeneration, from the battery 6 via the contact b of the contactor 7A. A pre-excitation current path to the field coil 4 is formed.

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 10,
Reference numeral 11 serves to form a circulating current path of the armature 1 or to form a flywheel current path of the armature 1 and the field coil 4 in accordance with the switching state of the contactors 2A and 3A while the chopper main circuit 5 is off. A regenerative diode 12 is provided on one end of the armature 1 (on the side of the shunt resistor 1A) and on the reference potential side (on the side of the negative electrode) of the battery 6. This diode 12 is used for forming a charging path to the battery 6 and an exciting current path to the chopper main circuit 5 for the generated current of the DC motor during regeneration. Shunt resistance 1A
Detects the current flowing through the armature 1 as a voltage signal, and this detection signal is used to determine that the armature current has dropped below a certain value when switching from plugging to regeneration, as will be described later.

The chopper main circuit 5 is provided with a contactor 13 in parallel,
The contactor 13 is replaced by a chopper, an electric motor and a battery 6
It is prepared for the highest speed operation in which the full voltage is applied.

In such a main circuit configuration, the contactor 7A is connected to the contact a side and the contactor 2A is connected to the contact a side by energizing the contactor 7 through the forward / reverse selector switches 14F and 14R in the normal operation (power line). The conduction ratio of the chopper main circuit 5 is controlled according to the accelerator depression amount, and the forward variable speed operation is performed. On the contrary, when the contactor 3A is connected to the contact a side, the backward (reverse) variable speed operation is performed. In this normal operation, when the chopper main circuit 5 is off, the diode 10
Acts as a flywheel and the diode 11 acts as a circulating current, and in reverse, the diodes 10 and 11 act in reverse.

Next, during plugging, the contactor 2
A and 3A are switched in the opposite direction to the previous state, the current of the field coil 4 is switched to the reverse rotation side, and the chopper main circuit 5 is operated.

At this time, during the ON period of the chopper main circuit 5, the battery 6
To contactor 7A → shunt resistor 1A → armature 1 → contactor 2A or 3A → field coil 4 → contactor 3A or 2A → chopper main circuit 5 to flow exciting current If, thereby increasing current Ia to armature 1 Generate an induced voltage in the direction of Then, in the off period of the chopper main circuit 5, the increased current of the armature 1 is applied to the contactor 2A or 3A → diode.
10 or 11 → Contactor 7A → Shunt resistor 1A. 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 lost to the armature winding, the diode, the brush, and the contact resistance between the brush and the commutator. Therefore, plugging braking not only damages the surface of the brush and commutator, but also dissipates kinetic energy. Therefore, instead of plugging, a braking control circuit for using both plugging and regenerative braking, which enables regenerative braking with a relatively small armature current, is provided with the following microcomputer as a control center.

The microcomputer 15 includes a parallel input / output circuit (PIO) 16 and a bus buffer 17, which are connected to each other by a bus.
Power operation, plugging, and regenerative operation control signals are transmitted and received via. The parallel input / output circuit 16 takes in as a digital signal from the potentiometer 18 that becomes an output proportional to the accelerator depression amount through the analog-digital converter 19.
In response to this digital signal, the microcomputer 15
The CPU obtains a chopper on-timing signal and gives an on signal of the main thyristor SM to the chopper control circuit 20 through the parallel input / output circuit 16. The chopper control circuit 20 turns on the main thyristor SM of the chopper main circuit 5 by the chopper turn-on timing signal, and turns off the main thyristor SM by turning on the auxiliary thyristor SS after a certain period of time. Therefore, the chopper conduction rate is constant during the ON period, and the OFF period is controlled from the microcomputer side, so that the conduction rate is controlled according to the accelerator depression amount.

The parallel input / output circuit 16 is connected to the driver 21 so as to output bit data, and enables operation control of the electromagnetic contactors 2, 3 and 7 via the driver 21 and its output circuits 22 and 23.
The output circuit 22 is normally on-controlled, and is off-controlled when circuit protection such as commutation failure of the chopper main circuit and failure detection. The output circuit 23 is ON-controlled in normal operation to leave the contactor 7A on the contact a side and separates the contactor 7A OFF-controlled during the circuit braking period including pre-excitation. These controls are performed under the control of the microcomputer 15. The control in the power running operation is performed by the configuration and the operation thereof described above.

Next, the configuration and operation of plugging and regenerative braking will be described with reference to the flowchart of FIG. In the powering state (step S1), when it is detected that the forward / reverse selector switches 14F and 14R have been switched to the reverse rotation side (step S2), the microcomputer 15 enters the plugging control mode by this detection (interruption). (Step S
3). In this plugging mode, the microcomputer 15 takes in a determination signal as to whether or not the plugging current Ip ₁ g is equal to or more than the set value Is (step S4).

This determination signal is taken in from the parallel input / output circuit 16 as the output of the current detection circuit 24. Current detection circuit 24 is diode 1
It is provided between the cathodes of 0 and 11 and one end of the armature 1 (on the side of the field coil) to detect the circulating current flowing from the armature 1 to the diode 10 or 11, and this detection signal sets the current Is. The judgment output of whether or not the value is exceeded is obtained.

When this judgment signal is Ip ₁ g <Is, the microcomputer
The 15 restarts the chopper operation to continue the plugging braking (step S5), determines from the state of the switches 14F and 14R whether or not it is the plugging mode (step S6), and returns to step S4 if the plugging mode is continued. The operation called plugging current determination is repeated, and the system returns to power running when the plugging mode is released (step S7).

If it is determined in step S4 that the plugging current Ip ₁ g is in a regenerable current, the microcomputer 15 measures the time Tp ₁ g when the plugging current Ip ₁ g is larger than the set value Is (step S8). This time Tp ₁ g is measured by the plugging current Ip
_As shown in Fig. 3, ₁ g is measured as the time it takes for the chopper main circuit 5 to turn off during the off period and exceed the set value Is and become Is or less again. Ip ₁ g ₁ in the figure is when the braking torque is small. And Ip ₁ g ₂ shows the case where the braking torque is large.

Next, the microcomputer 15 determines whether or not the measurement result of the time Tp ₁ g is longer than the set time Ts (step S
9). The set time Ts is calculated with a predetermined ratio with respect to one cycle of the chopper operation, and serves as a criterion for determining that regenerative operation is possible when the time Ts is exceeded.

When Tp ₁ g <Ts is satisfied in the determination in step S9, the microcomputer 15 returns to step S5 and continues plugging braking. When Tp ₁ g ≧ Ts, the microcomputer 15 enters regenerative control (step S10), and returns to plugging control when the electric power generation capacity of the electric motor decreases (step S11).

The control in steps S10 and S11 is as follows.

At the time of starting the regenerative control, the microcomputer 15 temporarily stops the chopper operation output, and after the time required for the armature current to decay, the output circuit 23 is changed from the on state to the off state through the parallel input / output circuit 18 and the driver 21. Switching and regenerative switching magnetic contactor 7 is returned to contactor 7A.
To the regenerative side (contact b). The detachment of the contactor 7A is detected by the voltage detection circuit 25 as the voltage generation at the contact b of the contactor 7A, and the microcomputer 15 confirms from the detection signal of the voltage detection circuit 25. After this confirmation is obtained, the microcomputer 15 gives an operation command of a constant cycle to the chopper control circuit 20 to restart the chopper operation, turns on the photocoupler 26 for a certain time, and turns on the switch means 8 by its output transistor. To perform pre-excitation for a certain time. This pre-excitation current is battery 6 → contactor 7A → switch means 8 → resistor 9 → contactor 2A (or 3A) → field coil 4 → contactor 3A (or
2A) → Flows in the path of the chopper main circuit 5 according to the chopper operation.

By this pre-excitation, the armature 1 acts as a generator,
After the completion of the pre-excitation, the microcomputer 15 confirms from the armature current that it can regenerate. For this confirmation, the voltage signal of the shunt resistor 1A is taken into the current judging circuit 27, and the output of the judging circuit 27 is taken into the microcomputer 15 through the parallel input / output circuit 16. In the current determination circuit 27, the comparator 27A compares the determination reference from the multiplexer 27B with the shunt resistance voltage signal, and the comparison result is taken out as the output of the transistor 27C at the logic level. The multiplexer 27B receives its input V by the microcomputer 15.
_A , V _B , and V _C are selectively output, and at this time, the microcomputer 15 selects the regenerability determination reference voltage V _A via the parallel input / output circuit 16.

When the microcomputer 15 confirms that the regenerative operation is possible, the regenerative braking is started. A microcomputer is used for this regenerative braking.
Reference numeral 15 controls the chopper conduction ratio according to the output of the potentiometer 18. During the off period of the chopper main circuit, the generated current of the armature 1 is made to flow through the path of the contactor 2A or 3A → diode 10 or 11 → battery 6 → diode 12 When the battery 6 is charged and the chopper main circuit is on, the generated current of the armature 1 is changed from the contactor 2A or 3A to the field coil 4 to the contactor 3A.
Alternatively, 2A → chopper main circuit 5 → diode 12 is passed through the path for excitation, and the braking energy is recovered as regenerative power to the battery 6 while repeating battery charging and excitation.

For regenerative braking, the microcomputer 15 determines whether or not regenerative braking is possible from the output of the current determination circuit 27 for each cycle of the chopper, and if regenerative is possible, continues regenerative braking and determines that the current level (V _A ) is not regenerative. When this is done, the output circuit 23 is turned on and the contactor 7A of the contactor 7 is returned to the contact a side, thereby controlling the plugging.

(Effects of the Invention) As described below, according to the present invention, regenerative braking is performed only when it is determined that the power generation capacity of the electric motor is sufficient for regenerative braking, and plugging braking is continued when insufficient. There is no useless power consumption such as pre-excitation during the above condition, and there is an effect that abrupt fluctuations in the braking torque are reduced.
In addition, since the time when the plugging current exceeds the set value is determined within one cycle of the chopper operation to determine whether regeneration is possible, there is an effect that the determination can be made surely and quickly, and the plugging can surely and promptly enter regeneration. is there.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a flow chart of the microcomputer in the figure, and FIG. 3 is a waveform diagram for explaining the regenerative ability determination in FIG. 1 ... Armature, 1A ... Shunt resistance, 2 ... Forward electromagnetic contactor, 3 ... Reverse electromagnetic contactor, 4 ... Field coil,
5: Chopper main circuit, 7: Regenerative switching magnetic contactor,
8 ... Pre-excitation switch means, 12 ... Regeneration diode, 15 ... Microcomputer, 16 ... Parallel input / output circuit, 17 ... Bus buffer, 19 ... Analog-digital converter, 20 ... Chopper control Circuit, 21 …… driver, 24
...... Current detection circuit, 25 ...... Voltage detection circuit, 27 ...... Current judgment circuit.

Claims (1)

[Claims] 1. A main circuit comprising an armature (1) of a series-wound DC motor for driving an electric vehicle, a field coil (4), forward / reverse electromagnetic contactors (2, 3), and a chopper main. The circuit (5), the battery (6), the regenerative switching electromagnetic contactor (7), the diode (10, 11, 12), and the switch means (8), the control circuit, the current detection circuit (24) and voltage detection circuit (2
5), current determination circuit (1A, 27), braking control means (1
5, 16, 17, 21), and the forward / reverse electromagnetic contactor (2, 3) has the armature (1) and the field coil (4) connected in series in the electric vehicle. The chopper main circuit (5) includes a contactor that switches in the opposite direction depending on whether the vehicle is moving forward or backward.
3) is connected in series to the field coil (4) to control the conductivity, and the regenerative switching magnetic contactor (7) is disconnected when the DC motor is regeneratively braked. 6) and the armature (1) are disconnected from each other, and the pair of diodes (10, 11) are connected to the positive electrode side of the battery (6) from both ends of the field coil (4). 1) forms a circulating current path and a field coil (4) flywheel current path, and the diode (12) regenerates from the negative side of the battery (6) to the armature (1). The switch means (8) forms a current path, and the switch means (8) is connected to the regenerative switching electromagnetic contactor (7) via the forward / reverse electromagnetic contactors (2, 3) from the separated terminal. It forms a pre-excitation current path to the field coil (4). The detection circuit (24) detects a circulating current flowing from the armature (1) to the pair of diodes (10, 11) and obtains a judgment output as to whether or not the current exceeds a plugging current set value Is. The voltage detection circuit (25) is for detecting disconnection of the regenerative switching magnetic contactor (7), and the current determination circuit (1A, 27) is for detecting the current detection signal of the armature (1). Is for determining whether the regenerative braking is possible or higher, and the braking control means (15, 16, 17, 21) is used for the forward movement.
When switching the reverse electromagnetic contactors (2, 3) in the reverse direction (S
2) Enter the plugging control mode (S3) and continue the plugging braking by the control of the chopper main circuit (5) while the current detection circuit (24) outputs the judgment output smaller than the set value Is (S4, S5). , S6), when the judgment output is larger than the set value, the time Tpig for the judgment output is measured (S6).
8) When the time Tpig is smaller than the set time Ts that is a predetermined ratio with respect to one cycle of the chopper main circuit (5), the plugging control is continued, and when the time Tpig is larger, the regenerative control is started (S9). In the control, the chopper main circuit (5) is temporarily stopped to attenuate the current of the armature (1), and then the regenerative switching electromagnetic contactor (7) is separated, and the separation is detected by the voltage detection circuit ( When it is confirmed by the detection of 25), the chopper main circuit (5) is started and pre-excited by the ON control of the switch means (8), and after completion of the pre-excitation, the current determination circuit (1A, 27) It is confirmed from the output that regeneration is possible, regenerative braking is performed by controlling the conductivity of the chopper main circuit (5) (S10), and the output of the current determination circuit (1A, 27) is regenerated while continuing the regenerative braking. When it is judged as impossible, the regenerative switching electromagnetic contact A braking control circuit for a DC electric vehicle, characterized by returning the contactor (7) to return to plugging braking (S11).