JP3227622B2 - Travel control device for electric industrial vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control device for an electric industrial vehicle in which a pair of drive wheels are driven by two independent motors, and more particularly, to stabilizing the travel when turning.

[0002]

2. Description of the Related Art In an electric industrial vehicle such as a battery forklift, which travels with a pair of driving wheels and a steering wheel, two motors corresponding to each driving wheel are connected in parallel to a battery, and the two motors are connected in accordance with an accelerator operation amount. A traveling current flowing through both motors is controlled by a traveling transistor having a variable chopper operation rate.

At the time of starting, the chopper operation of the running transistor is soft-started irrespective of the accelerator operation amount in order to slowly start the rotation of both motors from the stop state. As a result, the motor current is gradually increased to prevent sudden start, thereby stabilizing traveling. By the way, in the electric industrial vehicle, one of the two motors is turned off with respect to the battery or the connection polarity is switched at the time of turning in accordance with the steering angle.

That is, when turning, as shown in Table 1, switching points are set at, for example, steering angles of 45 ° and 75 °, and the connection state of a predetermined contactor is switched at each switching steering angle.

[0005]

[Table 1] For example, in the case of a left forward turn, Table 1 shows a two-wheel drive mode in which the left and right forward contactors are turned on and current flows to the respective traveling motors in a steering angle section of 0 to 45 °, and an inner wheel in the section of 45 ° to 75 ° The forward contactor on the driving wheel side is turned off, and a single-wheel drive mode in which current flows only to the right running motor
In the section of 5 ° to 90 °, the reverse drive mode in which the reverse contactor on the left drive wheel side is turned on from OFF to supply reverse current to the left traveling motor is shown. Note that the right reverse contactor maintains OFF. FIG. 7 shows the relationship between the current flowing through the two traveling motors and the chopper operation rate when switching from the two-wheel drive mode to the one-wheel drive mode during the left turn. When the steering angle becomes 45 ° during a left turn (time t1), the left forward contactor is turned off, and the chopper operation is stopped regardless of the accelerator operation. This is to avoid in advance the impact on the vehicle body caused by the sudden change (cutoff or reversal of polarity) of the current due to the switching operation of the contactor. The control signal shown in FIG. 7 (C) is a signal for determining the chipper operation rate based on the level thereof. At time t1, for example, the control signal reaches a level A at which the duty cycle of the chopper operation pulse signal is 0% (chopper operation is stopped). Be lowered. This allows
The currents flowing through the left and right traveling motors are as shown in FIG.
As shown in (B), both are once dropped to zero. Thereafter, at time t2 after the elapse of the operation period Ta of the contactor, the control signal is changed to the level A in order to supply current to the traveling motor of the right driving wheel.
Further, the level is changed to the original level B by a gradient (BA) / Tb. At this time, since the traveling motor of the left driving wheel is separated from the traveling circuit, a current ia according to the gradient of the control signal flows through the traveling motor of the right driving wheel. A period Tb from time t2 to t3 at which the current ia reaches a peak is a so-called soft start period. Level B is a voltage corresponding to the accelerator operation amount, and in this case, is the same as before the stop of the chopper operation.

The reason why the control signal is gradually changed at a certain gradient is the same as the reason for avoiding sudden start at the time of starting. When the accelerator operation amount at the time of turning is large, the chopper operation rate is changed from low. The rotation of the traveling motor is slowly started by continuously changing at a high predetermined inclination to prevent the vehicle body from swinging due to sudden acceleration. The soft start control is also performed in switching between other modes.

[0007]

However, in the above-described conventional apparatus, the slope of the change characteristic of the soft start control is uniformly set to the same value (BA) / Tb as at the time of starting. Although sudden start is sometimes avoided, the rise of the motor torque due to the soft start is delayed for both drive wheels that are traveling inertia during turning, and the traveling is slow. In other words, immediately after pausing the chopper operation, the speed of both drive wheels gradually decreases due to inertia.However, since the increase curve of the motor torque due to the soft start is slower than this deceleration curve, it takes a long time to start acceleration. It takes time.

For example, when the mode is switched to the one-wheel drive mode, the inner wheels run inertially in a play state without a soft start. However, since a soft start is applied to the outer wheel, the rise of the running torque by the outer wheel is delayed with respect to the inner and outer wheels running by inertia, and the running is delayed. In addition, when switching to the reverse rotation drive mode, the directions of the running rotations are different from each other, and the running is sluggish due to the soft start applied to both drive wheels at that time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a travel control device for an electric industrial vehicle in which inner and outer wheels travel smoothly even by a soft start during turning.

[0010]

According to the present invention, a soft start control for changing a chopper operation rate of the running transistor from low to high at the time of starting is performed, and at the time of switching between modes during turning, the soft start control is performed at the time of starting. Control means is provided for performing rapid soft start control with characteristics faster than the change characteristics of the soft start control.

[0011]

According to the present invention, the characteristic of the soft start control during turning is steeper than the characteristic at the time of starting, so that the torque is increased in a short time for both driving wheels that are decelerated by inertia. The time required from the stop of the operation to the start of acceleration can be shortened. Therefore, the backlash of traveling is reduced, and smooth turning is achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment shown in FIG. In FIG. 1, a first electrode V ₁ for deriving, for example, a positive potential of a battery 11 is connected to a left forward contactor 1 _L
They are respectively connected to the switching terminal a of the switching terminal a and the right forward contactor 1 _R switching terminal a and the left reverse contactor 2 _L of the switching terminal a and the right reverse contactor 2 _R a. Between the common terminal c of the common terminal c and left reverse contactor 2 _L of the left forward contactor 1 _L, the armature 4 _L of the first travel motor 12 is inserted, the right and the common terminal c of the right forward contactor 1 _R between the common terminal c of the reverse contactor 2 _R, armature 4 _R of the second travel motor 13 is inserted. The switching terminal b of the left forward contactor 1 _{L and} the switching terminal b of the left reverse contactor 2 _L are commonly connected, and the connection point is connected to the collector of the traveling transistor 6 via the field winding 5 _L. 1 switching terminal b of the switching terminal b and the right reverse contactor 2 _R of _R is also commonly connected, the connection point is connected to the collector of the driving transistor 6 through the field winding 5 _R. The emitter of the traveling transistor 6 is connected to a second electrode V ₀ for deriving a negative potential of the battery 11.

A flywheel diode 14 is connected between the first electrode V ₁ of the battery 11 and the switching terminal b of the left forward contactor 1 _L , and switches between the first electrode V ₁ and the right forward contactor 1 _R. A diode 15 for the same purpose is connected between the terminal 15 and the terminal b. Further, a protection diode 16 for the traveling transistor 6 is connected between the first electrode V ₁ of the battery 11 and the collector of the traveling transistor 6.

The above configuration is a general three-wheel battery fork.
This is the travel circuit of the lift.
Operation of each forward contactor 1_L, 1_RIs switching
Connected to the terminal a and connected to each reverse contactor 2
_L, 2_RAre switched and connected to the switching terminal b side. Running tiger
The base of the transistor 6 has a data proportional to the accelerator operation amount.
The duty cycle pulse signal 7a is supplied,
Thus, each of the traveling motors 12, 13 is controlled by the pulse signal 7a.
Driven by the determined current. The pulse signal 7a is
Pulse whose cycle is determined by the accelerator operation amount
Signal. When moving backwards, operate the reverse switch
Reverse contactor 1_L, 1_RAnd 2_L, 2 _RIs opposite to the above
Switching connection state. Therefore, the left and right traveling motors 1
A current of the opposite polarity to that at the time of forward flow flows in 2 and 13 and goes backward.
You.

The pulse signal 7a is supplied to the running transistor 6 from the control means 7 according to the present invention. The control means 7 controls the switching of each contactor by a signal 8a from a steering angle sensor 8 attached to the rear axle shaft, for example, and controls the duty cycle of the pulse signal 7a by an internally generated control signal.

The operation of the control means 7 will now be described with reference to FIGS.
It will be described in detail based on. When the power of the vehicle is turned on, FIG.
Is started. The control means 7
After the initial setting (not shown), it is determined in step S1 that, for example, one of the switches related to traveling has been operated, and it is determined whether or not the vehicle has started. If the vehicle is not a start, the process proceeds to another process such as a cargo handling process.

The characteristic of the control signal selected in step S2 is, as shown by the dotted line in FIG.
Is changed to (BA) / Tb.
As a result, at the time of start (including forward and reverse or start from a turning state), a soft start in which the chopper operation rate is changed by the inclination (BA) / Tb is applied. Next, the control means 7 reads and decodes the signal 8a from the steering angle sensor 8 in step S3 to recognize the steering angle, and determines in next steps S4 and S5 whether to switch between modes based on the recognized steering angle. Judge. Step S4 is a process for determining switching between the two-wheel drive mode and the one-wheel drive mode, and step S5 is a process for determining switching between the one-wheel drive mode and the reverse rotation drive mode. Steps S4 and S
In the case of YES at 5, the process proceeds to step S6 to select the characteristics of the control signal. That is, the slope of the control signal is
It is (BA) / Tc in FIG. 3C. This inclination is steeper than the inclination at the start because Tc <Tb as is clear from FIG. 3C. Note that the inclination (BA) / Tc at the time of turning is the inclination (BA) / T at the time of starting.
If b is set to 1, a good running feeling can be obtained when the ratio is usually set to 3 to 7.

When the inclination of the soft start control used at the time of turning is set, the control means 7 performs a contactor switching process as shown in Table 1 in step S7. Switching process of the contactor, for example, when the two wheels driving mode at the right turning of the switch to one wheel drive mode, the driving current I _F from the state of FIG. 4, which switches as shown in FIG. 5, one wheel driving Switching from the mode to the reverse rotation drive mode is to switch from the state of FIG. 5 to the state of FIG.

FIG. 3 shows switching from the two-wheel drive mode to the one-wheel drive mode. At time t1, the control signal is lowered to the A level, and the running current _IF is temporarily reduced to zero. As a result, no current flows to the two traveling motors 4 _L and 4 _R , and during that time the left forward contactor 1 _L is turned off as shown in FIG.
I do. During this operation period Ta, both drive wheels run with inertia.

At time t2, the control signal becomes lower than level A.
B, the right traveling motor 1 _RRunning current I_FBut
Flows. The running current I at this time_FIs selected in step S6
The slope of the control signal increases as shown by ia ',
It increases faster than the current ia at the start shown in FIG. Therefore,
In contrast to the left drive wheel that is inertia running in play, the right drive wheel
Luk rises in a short time, and the running is eliminated.

Next, when the contactors are switched,
The control means 7 determines whether or not the accelerator operation has been suspended in step S8. If it is determined that the accelerator operation has been performed as it is, the above processing is repeated again from step S3, and it is determined that the accelerator operation has been suspended. If it is determined, the process returns to step S1. Thus, this embodiment is
When the running current is increased by the soft start at the drive mode switching point at the time of turning, a soft start with a steeper slope than at the start is applied, and the contactor operating period during which the running current is temporarily reduced to zero The torque increase by the soft start is faster than the inertia running.

In the above embodiment, the switching steering angle between the drive modes is set to 45 ° and 75 °, but the present invention is not limited to this value.

[0023]

As described above, according to the present invention, the soft start at the time of starting is performed at the switching steering angle between the two-wheel drive mode and the one-wheel drive mode and the switching steering angle between the one-wheel drive mode and the reverse rotation drive mode. Since the soft start having a characteristic steeper than the characteristic is performed, the torque can be quickly increased for the drive wheel that is traveling by inertia, and there is an effect that the backlash of the traveling is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a travel control device for an electric industrial vehicle according to the present invention.

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a timing chart illustrating a soft start according to the present invention.

FIG. 4 is an explanatory diagram showing a traveling current path in a two-wheel drive mode.

FIG. 5 is an explanatory diagram showing a traveling current path in a one-wheel drive mode.

FIG. 6 is an explanatory diagram showing a traveling current path in a reverse rotation drive mode.

FIG. 7 is a timing chart illustrating a conventional soft start.

[Explanation of symbols]

1 _L ... left forward contactor, 1 _R ... right forward contactor, 2
_L … Left reverse contactor, 2 _R … Right reverse contactor, 4 _L
... left travel motor, 4 _R ... right travel motor, 5 _L, 5 _R ... field winding 6 ... travel transistors, 7 ... control unit, 8 ... steering angle sensor.

Claims (1)

(57) [Claims] A first and a second traveling motor corresponding to left and right driving wheels are connected in parallel to a battery, and a collector-emitter passage is connected to both of the traveling motors in series. 1st and 2nd
A two-wheel drive mode in which the magnitude of the current to the traveling motor is controlled, and a current is supplied to the first and second traveling motors in accordance with the steering angle at the time of turning. In a travel control device for an electric industrial vehicle, which is switched between a wheel drive mode and a reverse drive mode in which a reverse current flows to an inner wheel side motor, a soft start for continuously changing a chopper operation rate of the travel transistor from low to high when starting. A travel control device for an electric industrial vehicle, further comprising control means for performing control and performing rapid soft start control having a characteristic faster than a change characteristic of the soft start control at the time of starting when switching between the modes.