JP3377343B2 - How to prevent front motor burnout - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reach type forklift truck capable of grasping overwork of a front motor that is linked to the front wheel and auxiliary drives the front wheel, and can prevent burnout of the motor. A method for preventing burnout.

[0002]

2. Description of the Related Art As shown in FIG. 7, conventionally, a reach-type forklift truck (hereinafter, simply referred to as a forklift) F is located behind a vehicle body 2 and has one rear steering wheel which is steered by steering a steering wheel 5. Wheel 3
With two front wheels 4L, 4R
A mast 15 that locks the cargo handling tools 14, 14 such as a fork that can be moved up and down by a lift cylinder 13 is provided between the straddle arms 12, 12 that rotatably support the.

The vehicle body 2 is provided with various hydraulic operation levers 16, an accelerator 8 for rotatably driving a rear wheel 3, and a battery BA. Further, the rear wheel 3 is a traveling electric motor (via a gear reducer). By cooperating with both (not shown), it is rotationally driven according to the operation amount of the accelerator 8.

By the way, when the mast 15 is forwarded in a state where a load is loaded on the cargo handling tool 14, the center of gravity moves to the front of the vehicle, and the axle weight acting on the rear wheel 3 decreases. In such a state, even if the forklift F is made to travel on a road surface having a low coefficient of friction, for example, wet concrete, a frozen frozen warehouse floor surface, etc., the rear wheel 3 slips, and in particular, it becomes impossible to travel. .

Therefore, when the vehicle starts running, the accelerator 8
Regardless of the operation amount of the
A slip countermeasure has been proposed which prevents a slip due to a sudden start by suppressing the torque generated by the electric motor.

However, when the current to the traveling electric motor is reduced, although some effect can be expected in slip prevention, it takes time to start the forklift truck, which reduces the cycle time of the cargo handling work, resulting in workability. There is a problem of damaging. In addition, there is a problem that the forklift truck cannot be started and gets stuck due to insufficient torque on an uphill or the like.

In order to solve one of the above problems, an auxiliary electric motor is attached to each of the two front wheels, and the rear wheels are driven at the time of start-up. Therefore, slippage is limited immediately after start-up. It has been proposed to drive the front wheel only for a certain period of time.

[0008]

However, in the structure described above, the auxiliary electric motor cannot be driven even if slip occurs due to, for example, climbing a hill while the vehicle continues to travel after the elapse of the predetermined time, and the slip state is reduced. There is a problem of continuing.

On the other hand, if the drive of the auxiliary electric motor is continued in the state where the rear wheels continue to slide, the operation will exceed the rated value of the auxiliary electric motor and there is a risk that the auxiliary electric motor will be burned.

According to the present invention, the work of each front motor engaged in the front hole can be calculated, and based on the work value, the front motor can be prevented from being burned on the basis of turning on or off the front motor. Another object of the present invention is to provide a method of preventing burnout of a front motor, which allows an operator to recognize an overload condition and prevent accidents.

[0011]

According to the present invention, there are provided a rear wheel which is arranged on the rear side of a vehicle body, is turned by a steering operation and is driven by a drive motor, and a front motor which is arranged on both front sides of the vehicle body. A method for preventing burnout of a front motor in a reach-type forklift truck having associated front wheels, comprising a steering angle θ of a rear wheel, a rotation speed Vs of a rear wheel, and rotation speeds V ₁ , V of both front wheels.
₂ and the steering angle θ of the rear wheel,
Predicted speeds Vo ₁ and Vo ₂ of each front wheel are obtained from the rotational speed Vs of the rear wheel, and the difference between the rotational speed and the predicted speed | V ₁ −Vo ₁ |
When a current value that reduces | V ₂ −Vo ₂ | is given, the work amount value of each front motor is calculated, and when the work amount value of each front motor exceeds a reference value for preventing burnout of the front motor, A front motor burnout prevention method is characterized in that the current to the front motor is cut off.

The work amount value can be displayed as the product of the square value of the current value of the front motor and the resistance value of the front motor. Further, it is preferable that this work amount is integrated while the drive motor is being driven by the accelerator.

According to the present invention, by having the above structure,
Even on an uphill road or on a slippery road surface, the front motor can suppress the amount of heat generated by one run to a certain value or less, which can prevent burnout of the two motors on both sides. Further, when the work amount exceeds a certain value, the driving of the front motor is stopped, so that the driver can recognize the road surface condition, which is also useful for preventing a driving accident.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings, using a case where a battery type reach type forklift truck is adopted.

The reach type forklift truck F is shown in FIG.
As shown in FIG. 3, a rear wheel 3 is arranged behind the vehicle body 2 and is steered by an operation of a steering wheel 5 and driven by a drive motor 6, and a front motor 7R7L arranged on both front sides of the vehicle body 2. And a pair of front wheels 4R and 4L which are associated with each other. The front wheels 4R and 4L do not swing, and straddle arms 1 arranged on both front sides of the vehicle body 2
It is axially supported so as to be capable of traveling in the longitudinal directions of 2 and 12.

The front motors 7L and 7R and the drive motor 6 are both formed as a DC series-wound electric motor using a battery BA mounted on the vehicle body 2 as a power source in this embodiment. The output speeds of the front motors 7L and 7R and the drive motor 6 are individually controlled by the front motor speed controllers 17L and 17R and the rear motor speed controller 18, which are chopper circuits, as shown in FIG. .

The drive mechanism for the front wheel 4L located on the left side in FIG. 1 uses one plate 20 for the straddle arm 12 as shown in FIG. 2 (the front wheel 4R on the right side also has the same structure). The gearbox 21 that internally supports the gear reduction mechanism is fixedly attached, thereby suppressing an increase in the width of the straddle arm 12.

A transmission shaft 25 having an idle gear 24 meshing with a pinion gear 23 fixed to the output shaft 22 of the front motor 7L is arranged in the gear box 21, and a bevel pinion gear 26 at the other end of the transmission shaft 25 is arranged. , Engages with the bevel gear portion 27 of the idle shaft body 29.

The spur gear portion 28 at the other end of the idle shaft body 29 is meshed with the final gear 31 of the drive shaft 32 via the intermediate spur gear 30. The drive shaft 32 is
It is supported on the cylindrical portion 33 of the gear box 21 by tapered roller bearings B, B assembled on the back surface. The gear box 21 is filled with gear oil, and the gap with the plate 20 is oil-tight.

Therefore, the front wheels 4L, 4R are driven together with the rotation of the front motors 7L, 7R by energizing the front motors 7L, 7R, and idle as free wheels when the front motors are not energized.

Each slide arm 12, 12 has a
Front wheel rotation speed sensors 34L, 34 for detecting respective rotation speeds of the front wheels 4L, 4R.
R is arranged, and each front wheel current sensor 35 capable of detecting the drive current of each of the front motors 7L and 7R.
L and 35R are arranged.

On the other hand, on the vehicle body 2, a rear wheel turning sensor 36, which is provided to the steering wheel 5 and detects a turning angle θ which is an inclination angle of the rotation axis of the rear wheel 3 with respect to the forward direction of the reach type forklift truck F, a rear wheel turning sensor 36. A rear wheel rotation speed sensor 37 that detects the rotation speed of the wheel 3 and a control device 10 that performs calculation based on the output signals of these sensors are provided.

Further, in this example, as shown in the control block diagram of FIG. 3, the accelerator 8 is provided with accelerator lever operation amount detecting means capable of detecting the operation amount thereof. In the present embodiment, this means comprises, for example, a potentiometer 39 that detects the amount of rotation of the cam piece 8B that rotates with the accelerator lever 8A.
Send to.

In addition to the signals for forward and backward movements by operating the accelerator lever 8A, the control device 10 controls the steering angle signal from the rear wheel turning sensor 36, the speed signal from the rear wheel rotation speed sensor 37, and each front. Speed signals of the left and right front wheels 4L and 4R from the wheel rotation sensors 34L and 34R are input and calculated to calculate a turning center point P of the vehicle body 2 as shown in FIG.
And front wheels 4L, 4 from this turning center point P
Turning radius L1, L2, L3 to the R and the rear wheel 3
And calculate.

Under the turning conditions, the theoretical speeds of the front wheels 4L, 4R with the rear wheel 3 as a reference are in a proportional relationship shown in the equation. _{L1: L2: L3 = Vo 1} : Vo 2: Vs

Therefore, the theoretical speed Vo ₁ of the first front wheel 4L is calculated from the turning radii L1 and L3, and the theoretical speed Vo ₂ of the second front wheel 4R is the turning radius L.
2, calculated by L3.

The first and second front wheels 4L, 4
The difference between the actual velocities V ₁ and V _{2 of} R and the theoretical velocities Vo ₁ and Vo ₂ , S ₁ and S ₂ are S ₁ = | V ₁ −Vo ₁ | 2nd front in the first front wheel 4L. It is calculated by S ₂ = | V ₂ −Vo ₂ | in the wheel 4R.

However, when the reach type forklift truck F travels normally, the front wheels 4L, 4R are
The front motors 7L and 7R are in the idling state without being energized, and the drive motor 6 drives to drive only the rear wheel 3.

When the reach type forklift truck F is climbing a hill or is overloaded, the front wheel 4
When the load is concentrated on L and 4R, speed differences S ₁ and S ₂ due to slippage occur between the rear wheel 3 and the first and second front wheels 4L and 4R. This speed difference S ₁ , S
₂ is calculated by the control device 10 in consideration of the occurrence of a speed difference due to turning as described above, and is compared with a predetermined reference value So. If the reference value So is exceeded, the first and second values are obtained. A current is applied to each of the front motors 7L and 7R that engage with the two front wheels 4L and 4R, and the two front wheels 4L and 4R are individually driven.

The speed differences S ₁ and S ₂ are based on the reference value So.
When it is less than, the drive motors 7L and 7R are not energized and the front wheels 4L and 4R are free wheels.

The front motors 7L and 7R are set to speed ratios corresponding to the turning radii L1 and L2 ratios respectively, and the speeds are set by the front motor speed controllers 17L and 1L.
Each chopper ratio of 7R is set to a ratio corresponding to the turning radii L1 and L2 ratios, so that so-called three-wheel drive can enhance traction with the road surface.

However, since the front motors 7L and 7R are installed on the narrow straddle arms 12 and 12 as described above and are driven auxiliary and intermittently, a small motor having a low rating is used. Therefore, if the front motors 7L and 7R are continuously used for a long time, there is a risk that the front motors 7L and 7R will be heated and burned due to overheating.

In order to eliminate the danger of the front motors 7L and 7R, it is necessary to individually restrict the power supply to the front motors 7L and 7R.

The current value Il flowing through the first front motor 7L is detected for each unit time dt pitch and input to the control device 10, and the current value I within the fixed time T is also detected.
₁ squared value (I ₁ ) ² and resistance value R of the front motor 7L
By integrating the product of ₁ and ₁ as shown in the equation during the fixed time T, the first front motor 7L
The work amount W1 within the constant time T of is calculated. Wl = ∫ _O ^T (I ₁ ) ² · R ₁ dt

It should be noted that the fixed time T is equal to
It is preferable that the value is equal to or less than the rated value of L. Further, also for the second front motor 7R, the work amount W2 within the fixed time T is calculated from the current value I ₂ and the resistance value R ₂ by the following formula by the same method. W2 = ∫ _O ^T (I ₂ ) ² · R ₂ dt

Further, the control device 10 is preset with a reference value Wo for the work amount for preventing the front motors 7L, 7R from being burnt out.

After a certain time T has passed, the reference value W
o and cumulative work ΣW of each front motor 7L, 7R
1 and ΣWr are compared with each other over time, and when one of the front motor 7L (7R) cumulative work value ΣW1 (ΣW2) exceeds the reference value Wo, It is formed so as to cut off the current to the front motor 7L (7R).

When the accelerator 8 is returned, the work amount values W1 and W2 are zero. The above-mentioned operation procedure is shown as a flow chart in FIGS.

Therefore, the first and second front wheels run under different conditions such as when the vehicle body turns, not only when the first and second front wheels run under substantially equal 4L and 4R conditions. Even when one of the front motors has a larger load than the other front motor as in the case, the front motor on the side with the larger load is used to judge and stop the front motors 7L and 7R. Front motor 7 without being affected by
Burnout of L and 7L can be prevented.

Further, by stopping the front motors 7L and 7R, it is possible to notify the driver of the abnormal state of loading, the state of the road surface, and the abnormal state of driving.

In the present invention, instead of measuring the current value of the front motor, the integrated electric power value can be measured, and the present invention can be modified into various modes.

[0042]

As described above, the method of preventing burnout of the front motor according to the present invention has the above-mentioned configuration, so that the heat generation amount of the front motor can be regulated even when the rear wheel is in a slippery running condition. You can limit it to below the value,
The front motor can be prevented from being burnt out, the reach of the reach truck can be prevented from being damaged, and the operating rate can be increased.

Further, by stopping the driving of the front motor, the driver can be made aware of the condition of the road surface and abnormalities in loading and operation, and the occurrence of an accident can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of an embodiment of the present invention.

FIG. 2 is a sectional view illustrating a drive mechanism of a front wheel.

FIG. 3 is a control block diagram of the present invention.

FIG. 4 is a plan view illustrating a turning radius of each wheel.

FIG. 5 is a block diagram showing a first half of a control procedure.

FIG. 6 is a block diagram showing the latter half of the control procedure.

FIG. 7 is a side view for explaining a conventional reach type forklift truck.

[Explanation of symbols]

2 car body 3 rear wheel 4L, 4R front wheel 5 steering 6 drive motor 7L, 7R front motor 8 accelerator

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-162996 (JP, A) JP-A-8-265917 (JP, A) JP-A-7-163018 (JP, A) JP-A-7- 163019 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60L 3/00 B60L 15/20 B66F 9/24

Claims (3)

(57) [Claims] 1. A reach having rear wheels arranged at the rear of the vehicle body, which are steered by a steering operation and driven by a drive motor, and front wheels arranged at both front sides of the vehicle body and linked to the front motor. A method for preventing a front motor from burning in a forklift truck, the steering angle θ of the rear wheel, and the rotation speed V of the rear wheel.
s, the rotational speeds V ₁ and V ₂ of the front wheels on both sides are obtained, and the predicted speeds Vo ₁ and Vo of the front wheels are calculated from the steering angle θ of the rear wheel and the rotational speed Vs of the rear wheel.
₂ is obtained, and a current that reduces the difference | V ₁ −Vo ₁ |, | V ₂ −Vo ₂ | between the rotation speed and the predicted speed is given to each front motor, and the work amount value of each front motor is calculated. Then, when the work value of each front motor exceeds a reference value for preventing the burnout of the front motor, the current to the front motor is shut off. 2. The method for preventing burnout of a front motor according to claim 1, wherein the work value is a product of a square value of a current value of the front motor and a resistance value of the front motor. 3. The work value is integrated while the drive motor is being driven by the accelerator, and the work value is 0 when the accelerator is returned. The method for preventing the front motor from burning as described above.