JPH0993726A - Method for controlling electric rolling stock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the torque of an electric rolling stock sufficiently large when the stock goes up grades by identifying whether the drive mode of the stock is a reverse rotation braking mode or a grade starting mode, and making the braking force appropriate when the stock makes reverse rotation by controlling a chopper at a duty ratio preset to each mode. SOLUTION: The reverse rotation braking mode and the grade starting mode of an electric rolling stock are discriminated from each other by utilizing a forward movement holding signal S4 and backward movement holding signal S5 . That is, the reverse rotation braking mode is detected when both holding signals S4 and S5 are in 'H' states where a DA current detecting signal S3 rises. A reverse rotation braking discriminating signal S6 limits the brake power caused by reverse rotation by making the duty ratio of a chopper relatively smaller while the signal S6 is in an 'H' state. Even when the signal S3 rises, a prescribed torque is secured for going up grade by making the duty ratio relatively larger before the signal S3 falls while an up-grade discriminating signal S7 is maintained in an 'H' state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle control method, and is particularly useful when applied to an electric vehicle such as a battery forklift that uses a DC motor driven by a battery that is a DC power source as a drive source.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram of a drive system of an electric vehicle such as a battery forklift truck which uses a DC electric motor driven by a battery which is a DC power source as a drive source. In the figure, 1 is a battery which is a DC power source, 2 is a DC motor,
It has an armature 2a and a field winding 2b. 3 is a chopper formed of a transistor, MF and MR are contactors which are switch means, DA is an amateur diode, and DF
Is a flywheel diode, and CS is a current sensor.

In such a drive system, the contactor MF
Is brought into contact with the contact on the right side in the figure, and the contactor MR comes into contact with the contact on the left side in the figure (hereinafter, this state is referred to as the forward mode), whereby the battery 1 is connected to the armature 2a and the field winding 2
b, a closed circuit that returns to the battery 1 through the chopper 3 is configured. As a result, the DC motor 2 is driven to move the electric vehicle forward.

On the contrary, the contactor MF makes contact with the contact on the left side of the drawing and the contactor MR makes contact with the contact on the right side of the drawing (hereinafter, this state is referred to as the reverse mode) to move the electric vehicle backward.

The speed of the electric vehicle at this time is controlled by the duty ratio of the chopper.

On the other hand, reverse braking is used when braking an electric vehicle. That is, for example, during the forward movement, the contactors MF, M
The DC motor 2 is caused to function as a generator by switching R from the forward mode to the reverse mode, and the rotational energy of the DC motor 2 is consumed by causing the current in the path A to flow through the armature diode DA.

At this time, to prevent the braking from becoming too strong,
When the conduction of the armature diode DA is detected, the duty ratio of the chopper 3 is reduced to suppress the field current in the path B, thereby limiting the current generated by the armature 2a and limiting the braking force to an appropriate value. The conduction of the amateur diode DA can be detected by monitoring the forward voltage of the amateur diode DA. That is, when the forward voltage is about 1.0 V, it is in a conductive state.

[0008]

In the control method according to the prior art as described above, when reverse braking is performed by switching the contactors MF and MR, it is detected that the armature diode DA becomes conductive at this time, and the armature is detected. Although the current flowing in 2a is limited to obtain an appropriate braking force, when the brake pedal is changed while the electric vehicle starts on a slope, the electric vehicle slips down, that is, the DC motor 2 moves backward. Since the chopper 3 operates in the state of rotating to, the field is excited in the opposite direction to the rotating direction of the DC motor 2 to generate power, and conduction of the amateur diode DA is detected.

Therefore, the chopper 3 operates in the same manner as during reverse braking. That is, the duty ratio is reduced to limit the field current. As a result, the torque required for climbing the hill is not generated, which causes a problem that the electric vehicle slides down a slope.

In order to avoid such a phenomenon, if the duty ratio in this case is increased, the braking force at the time of reverse braking becomes too large, and a sudden braking force causes an impact on the electric vehicle.

The present invention has been made in view of the above-mentioned problems of the prior art,
An object of the present invention is to provide a control method for an electric vehicle that can not only make the braking force at the time of reverse braking appropriate but also make the torque at the time of climbing sufficiently large.

[0012]

The structure of the present invention that achieves the above-mentioned object includes a chopper, a DC motor which controls the rotation speed by the chopper and serves as a drive source of an electric vehicle, and an armature of the DC motor. The field windings are connected in series and the direction of the field current supplied to the field windings is switched so as to switch the direction of rotation of the DC motor according to the forward and backward modes of the electric vehicle. Switch means for holding the neutral mode, which is a state in which the field current that is neither of the modes is cut off,
In a method of controlling an electric vehicle having an armature diode connected in anti-parallel to an armature so as to pass an armature current during reverse braking, the armature diode is conducting, and the forward mode or reverse mode transition or retraction When the shift from the mode to the forward mode is detected, the chopper is controlled so that the duty ratio of the chopper becomes relatively small, while the forward mode is detected even if the amateur diode is detected to be conducting. When the shift to the reverse mode or the shift from the reverse mode to the forward mode is not detected, the chopper is controlled so that the duty ratio of the chopper becomes relatively large.

Further, when it is detected that the amateur diode is conducting, and the transition from the forward mode to the reverse mode or the transition from the reverse mode to the forward mode is detected, the predetermined minimum holding time is at least the same state. May be held. By doing so, it is possible to avoid the influence of this operation even when the operation of turning on / off the switch means is repeated in a short time between the neutral mode and the reverse braking mode.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

The present embodiment is realized by the circuit shown in FIG. 2, and FIG. 1 is a waveform diagram for realizing the embodiment.

As shown in FIG. 1, the forward movement command S ₁ and the backward movement command S ₂ are signals for controlling the operations of the contactors MF and MR. When the forward movement command S ₁ is in the H state, the contactors MF and MR are in the forward movement mode. In addition, when the reverse command S ₂ becomes the H state, the reverse mode is set.

The DA current detection signal S ₃ is a signal for detecting the conduction of the amateur diode DA, and is detected by the DC motor 2 functioning as a generator during reverse braking and when starting on a slope. It is a signal to hold. The conduction of the amateur diode DA is the forward voltage (about 1.0) across the amateur diode DA.
V).

The forward hold signal S ₄ is at a rise of the forward command S ₁ rise, holds the same state when the forward command S ₁ is the H state, the DA current detection signal S ₃ even down forward command S ₁ is standing DA current detection signal S ₃ during H state
It is a signal that holds the same state as that of the above and falls with the fall of the DA current detection signal S ₃ . Further, the reverse hold signal S ₅ is a signal corresponding to the forward hold signal S ₄ in relation to the reverse command S ₂ . These forward or backward holding signals S ₄ , S
₅ is formed based on the forward movement command S ₁ , the backward movement command S ₂ and the DA current detection signal S ₃ .

In this embodiment, the forward rotation holding signal S ₄ and the backward movement holding signal S ₅ are used to distinguish between the reverse braking mode and the slope starting mode. That is, when the DA current detection signal S ₃ climbed standing, detects that the plugging mode with a possible forward and reverse hold signal S _4, S ₅ are both in the H state. This is because such a state occurs only when the contactors MF and MR shift from the normal rotation mode to the reverse rotation mode or vice versa.

As described above, the reverse rotation braking mode means that the forward command S _{1 is} issued when the DA current detection signal S ₃ rises.
It is sufficient that the signal caused by the forward command S ₁ and the signal caused by the backward command S ₂ are in the same state. Therefore, another signal that rises due to the fall of the forward command S ₁ or the backward command S ₂ and lasts for a certain period of time. Is made by, for example, a one-shot multivibrator, and this signal and the backward command S ₂ or the forward command S ₁
It can be detected by comparing with.

The reverse braking determination signal S ₆ is the forward / reverse holding signals S ₄ , S ₅ when the DA current detection signal S ₃ rises.
Rises on the condition that H is in the H state, and DA
It is a signal that falls with the fall of the current detection signal S ₃ .
That is, this reverse rotation braking determination signal S ₆ is a signal representing the reverse rotation braking mode, and while this is in the H state, the chopper 3
The duty ratio is relatively reduced to limit the braking force by reverse braking.

In this embodiment, the reverse braking determination signal S ₆
Once rises, the H state is maintained for a predetermined minimum holding time t. As a result, during reverse braking, the contactor MF, MR is returned to the neutral position in order to reduce the impact due to braking, and the reverse braking determination signal S ₆ does not fall even if this operation is repeated for a short period of time (FIG. 1). See A).

The slope determination signal S ₇ is the reverse braking determination signal S ₆
It is a signal that has the opposite relationship to. Thus, even if the DA current detection signal S ₃ rises, if the slope determination signal S ₇ maintains the H state, it is determined that the vehicle is in the slope start mode and D
By the time the A current detection signal S ₃ falls, the duty ratio of the chopper 3 is relatively increased to secure a predetermined torque for climbing.

In the slope start mode, the contactors MF and MR shift from their neutral positions to the forward mode (reverse mode in some cases). So forward,
Retraction hold signal S _4, S ₅ is not that guests either one deer stand. Therefore, even when the DA current detection signal S ₃ is detected, the slope start mode can be specified by the fact that the forward and backward holding signals S ₄ and S ₅ are not in the H state at the same time. FIG.
Among them, S ₃ ′ is a DA current detection signal in the related art, and the motor rotation direction according to the related art corresponding to the DA current detection signal S ₃ ′ is shown below. In this motor rotation direction, the motor rotation direction in the prior art indicates that when the vehicle starts on a slope, it cannot move to powering until it has slipped down and the slope slope is gentle, and it is climbing from below the slope (see FIG. 1). (See B). On the other hand, in the present application, even if the vehicle is slipped down once and the generated current flows, it is possible to immediately shift to power running and climb uphill (see C in FIG. 1).

[0025]

As described above in detail with reference to the embodiments, according to the present invention, it is detected whether the mode is the reverse braking mode or the hill start mode, and the chopper has a predetermined duty ratio according to each mode. Therefore, the braking force can be appropriately limited in the reverse braking mode, and sufficient torque can be obtained in the slope start mode.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a control waveform that realizes an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a circuit of a drive system of an electric vehicle.

[Explanation of symbols]

 1 Battery 2 DC Motor 2a Armature 2b Field Winding 3 Chopper DA Amateur Diode

Claims (2)

[Claims] 1. A chopper, a DC motor that controls the rotation speed by the chopper and serves as a drive source for an electric vehicle, a field winding is connected in series to an armature of the DC motor, and the forward movement of the electric vehicle is performed. Depending on the mode and reverse mode,
To switch the direction of the field current supplied to the field winding so as to switch the rotation direction of the DC motor, and to maintain the neutral mode in which the field current that is neither in forward mode nor backward mode is cut off. In the control method of the electric vehicle having the switch means and the armature diode antiparallel connected to the armature so as to pass the armature current at the time of reverse braking, the armature diode is conducting, and the forward mode to the reverse mode. When the transition to the reverse mode or the transition from the backward mode to the forward mode is detected, the chopper is controlled so that the duty ratio of the chopper becomes relatively small, while it is detected that the armature diode is conducting. However, the transition from the forward mode to the reverse mode or the transition from the reverse mode to the forward mode is not detected. In this case, the electric vehicle control method characterized by duty ratio of the chopper controls the chopper so that relatively large. 2. The predetermined minimum holding time is at least the same state when it is detected that the armature diode is conducting, and the transition from the forward mode to the backward mode or the transition from the backward mode to the forward mode is detected. The method for controlling an electric vehicle according to claim 1, characterized in that