JP2007076749A - Cargo handling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cargo handling device capable of maintaining the number of revolution of a motor constant regardless of magnitude of load and difference in individual motors or the like without complex operation. <P>SOLUTION: In initial adjustment, the number of revolution and a current of the motor are measured in no-load state and loaded state respectively and a characteristic curve of the motor is determined from the measured number of revolution and current and is stored. In usual driving, a motor voltage for obtaining the desired number of revolution is calculated based on the desired number of revolution of the motor determined by an operation angle of an operation lever, a motor current detected by a current detector and a motor characteristic curve previously stored and the motor is driven by that voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cargo handling apparatus such as a forklift provided with an electric cargo handling mechanism, and more particularly to a control technology of a motor that drives the cargo handling mechanism.

  Some forklifts include a side shift mechanism and a rotate mechanism as an electric cargo handling mechanism. The side shift mechanism is a mechanism for moving the fork laterally with respect to the traveling direction of the vehicle body, and the rotate mechanism is a mechanism for rotating the fork relative to the vehicle body. A forklift provided with a side shift / rotate mechanism is described in, for example, Patent Document 1 described later.

  In the forklift as described above, a motor for driving an electric side shift / rotate mechanism is mounted. As this motor, a DC (direct current) motor is generally used. By adjusting the voltage applied to the motor by chopping it with a chopper circuit, the rotational speed of the motor is changed and the operation speed of the side shift / rotate mechanism is controlled. I am doing so.

  FIG. 4 shows a schematic configuration of a conventional forklift provided with an electric cargo handling mechanism. 50 is a tiltable operation lever provided in the driver's seat, 51 is a control unit including a CPU and a memory, 52 is a chopper output unit that outputs a chopped voltage, and M is a voltage output from the chopper output unit 52. , 53 is a speed reduction mechanism in the side shift / rotation mechanism driven by the motor M, and 54 is a fork driven by the motor M via the speed reduction mechanism 53. The chopper output unit 52 outputs a voltage corresponding to the operation amount of the operation lever 50, the number of rotations of the motor M is adjusted according to the operation angle of the operation lever 50, and the side shift / rotate operation of the fork 54 is performed. Speed is controlled.

  FIG. 5 is a characteristic curve showing the characteristics of the motor M. If the applied voltage of the motor M is constant, when the load is small, the rotational speed N of the motor M is increased and the current I is decreased. When the load is large, the rotational speed N of the motor M is decreased and the current is decreased. I increases. Further, if the load is the same, when the applied voltage V of the motor M is changed as indicated by a broken line, the rotational speed N of the motor M changes, and the rotational speed N increases as the applied voltage V increases. The applied voltage V can be adjusted by the operation angle of the operation lever 50.

  In the case of a conventional forklift, as is apparent from FIG. 5, when the load to be loaded is heavy, the load (current value) increases and the rotational speed decreases, and when the load to be loaded is light, the load (current value) ) Decreases and the rotation speed increases, so the rotation speed of the motor M increases and decreases according to the weight of the load. As a result, the speed of the side shift / rotate operation of the fork 54 varies depending on the load to be loaded. Further, since there are individual differences in motor characteristics, even the same motor M does not have exactly the same characteristics as in FIG. 5, and the rotational speed with respect to the motor current varies among individual motors. For this reason, even if the forklifts are equipped with the same motor M, the side shift / rotate operation speed varies. Further, in addition to such individual differences in motor characteristics, the load state varies depending on individual differences such as the resistance of the gear tooth surface and the lubrication state in the speed reduction mechanism 53, and the rotational speed of the motor M varies.

  As described above, in the conventional apparatus, the rotational speed of the motor M changes with load fluctuations due to motor characteristics, and the rotational speed of the motor M also depends on individual differences of the motor M and the speed reduction mechanism 53. Due to the variation, there is a problem that the speed of the side shift / rotate operation cannot be made constant. As described above, the number of rotations can be adjusted by changing the voltage applied to the motor M according to the angle of the operation lever 50, but the voltage value is determined by the angle of the operation lever 50. Therefore, it was not possible to always obtain the same motor speed for the same lever angle.

  On the other hand, Patent Document 2 described later is provided with a mode switch for arbitrarily selecting a speed characteristic of the motor with respect to load / no load, and the speed characteristic according to the weight and size of the load with this mode switch. A lift control device for a forklift that controls the motor to a predetermined speed based on the selected speed characteristic is described.

  In Patent Document 3 described later, a basic duty determined by a ratio between the maximum operation amount of the operation lever (accelerator) and the actual operation amount is calculated, and the current amateur current and the maximum speed of the forklift are calculated as the basic duty. A speed control device for an electric vehicle is described in which a chopper is turned on at a duty obtained by adding a current correction duty proportional to a difference from an amateur current at the time of traveling, so that the vehicle travels at a constant speed regardless of load fluctuations. Yes.

Japanese Patent Laid-Open No. 11-228095 JP-A-6-64899 JP-A-11-122720

  The apparatus disclosed in Patent Document 2 has a drawback that the speed characteristics must be set by operating the mode switch every time the weight or size of the load changes, and the operation is complicated. Moreover, in this patent document 2, the problem of the dispersion | variation in the motor rotation speed by individual differences, such as a motor and a deceleration mechanism, cannot be solved. On the other hand, in the apparatus of Patent Document 3, since the motor rotation speed is controlled to be constant according to the operation amount of the operation lever, the complexity of operation as in Patent Document 2 is eliminated. The problem of variation in the motor rotation speed due to individual differences cannot be solved even by this Patent Document 3.

  Accordingly, an object of the present invention is to provide a cargo handling apparatus that can maintain a constant motor rotation speed regardless of the magnitude of load and individual differences of motors, etc., without performing complicated operations.

  The present invention relates to a loading / unloading apparatus equipped with an electric loading / unloading mechanism driven by a motor, applying a predetermined voltage to the motor in two different loading states, and measuring the rotational speed and current of the motor in each loading state. Measurement means, calculation means for obtaining a characteristic curve of the motor based on the rotation speed and current measured by the measurement means, storage means for storing the motor characteristic curve obtained by the calculation means, and during normal operation A determining means for determining a desired rotational speed of the motor based on an operation amount of the operating lever; a current detecting means for detecting a current flowing through the motor during normal operation; and a desired rotational speed and current detecting means determined by the determining means. Based on the detected current and the motor characteristic curve stored in the storage means, the motor power for obtaining the desired number of rotations according to the operation amount of the operation lever. A voltage calculation means for calculating, in which a motor driving means for driving the motor by outputting a motor voltage calculated by the voltage calculation means.

  In the present invention, during the initial adjustment, the motor characteristic curve is obtained by measuring the motor rotation speed and current in two different loading states and stored. During normal operation, the motor voltage for obtaining the desired rotational speed is calculated using the above characteristic curve based on the desired rotational speed corresponding to the operation amount of the operation lever and the detected motor current, and the motor is driven with this voltage. Like to do. For this reason, once the motor characteristic curve is calculated and stored, the motor rotation speed becomes a constant value according to the operation amount of the operation lever with reference to this characteristic curve at the next normal operation. The motor voltage is automatically adjusted according to the load (motor current). Therefore, if the operating amount of the operating lever is the same, the same motor speed can be obtained regardless of the load, so the operator only has to operate the operating lever to achieve the desired speed, which makes the driving operation extremely difficult. It will be clear and easy to understand. In addition, the motor characteristic curve is obtained for each individual cargo handling device in the initial adjustment, and the motor voltage is calculated based on this, so even if there are variations in the motor rotation speed due to individual differences such as the motor and the speed reduction mechanism, this Variations can be absorbed. As a result, even when switching to another type of cargo handling device equipped with the same type of cargo handling mechanism, the motor speed is always the same if the amount of operation of the control lever is the same. You can drive at.

  In the present invention, switching means for switching the operation mode of the cargo handling device between the normal operation mode and the initial adjustment mode can be provided. When the initial adjustment mode is set by the switching means, the rotation speed and current of the motor are measured by the measurement means, the motor characteristic curve is calculated by the calculation means, and the motor characteristic curve is stored in the storage means. Further, when the normal operation mode is set by the switching means, determination of the desired rotation speed by the determination means, detection of current by the current detection means, calculation of the motor voltage by the voltage calculation means, and driving of the motor by the motor drive means Is done. The switching means is constituted by a switch that is manually switched, for example.

  Further, in the present invention, when measuring the rotational speed and current of the motor in two different load loading states, if the measurement is performed in each of the empty load state and the load loaded state, Can be done only once, and the initial adjustment can be performed efficiently.

  According to the present invention, if the operation amount of the operation lever is the same, the same motor rotation speed is always obtained regardless of the magnitude of the load or the individual difference of the motor, etc. Without this, it becomes possible to keep the rotation speed of the motor constant.

  FIG. 1 shows a schematic configuration of a forklift of the present invention provided with an electric cargo handling mechanism. 10 is a tiltable operation lever provided in the driver's seat, 11 is an adjustment switch also provided in the driver's seat, 12 is a control unit composed of a CPU and a memory, and 13 is a chopper output unit that outputs a chopped voltage. , M is a motor driven by the voltage output from the chopper output unit 13, 14 is a current detector (current sensor) for detecting the current of the motor M, and 15 is a side shift / rotate mechanism (illustrated) driven by the motor M. (Omission) is a speed reduction mechanism, 16 is a fork driven by the motor M via the speed reduction mechanism 15, and 17 is an encoder for detecting the rotational speed of the motor M.

  The operation lever 10 is operated by an operator, and the rotation speed of the motor M is uniquely determined according to the operation amount of the lever (angle from the initial position) as will be described later. The adjustment switch 11 is a switch that is manually switched. When the switch is OFF, the operation mode is a normal operation mode. When the switch is turned ON by an operator, the operation mode is an initial adjustment mode.

  The memory of the control unit 12 stores a motor characteristic curve described later. As will be described later, the control unit 12 is based on the number of rotations determined by the operation amount of the operation lever 10 (desired number of rotations), the motor current detected by the current detector 14, and the motor characteristic curve stored in the memory. Then, a motor voltage for obtaining a desired rotational speed corresponding to the operation amount of the operation lever 10 is calculated.

  The chopper output unit 13 includes a known PWM (Pulse Width Modulation) circuit, and outputs a pulse voltage with a duty corresponding to the motor voltage calculated by the control unit 12. The motor M is a DC motor driven by a pulse voltage output from the chopper output unit 13, and drives the fork 16 via a speed reduction mechanism 15 of a side shift / rotate mechanism.

  The current detector 14 is made of, for example, a resistor, and detects a current flowing through the motor M based on a voltage drop generated across the resistor. The detection output of the current detector 14 is given to the control unit 12. The encoder 17 is a rotary encoder that outputs a pulse proportional to the rotation speed of the motor M, and the detection output of the encoder 17 is given to the control unit 12.

  In the above, the adjustment switch 11 is an example of a switching unit in the present invention, the control unit 12 is an example of a calculation unit, a storage unit, a determination unit, and a voltage calculation unit in the present invention, and the chopper output unit 13 is a motor in the present invention. It is an example of a drive means, and the current detector 14 is an example of a current detection means in the present invention. Further, the current detector 14 and the encoder 17 are an example of measuring means in the present invention.

FIG. 2 is a characteristic curve showing the characteristics of the motor M. A is a characteristic curve showing the relationship between the motor current I and the rotational speed N when a rated voltage V _m (for example, 48 V) is applied, and B is the motor current I and the rotational speed N when the voltage V ₁ is applied. characteristic curve representing the relationship, C is a characteristic curve showing a relationship between the motor current I and the rotational speed N at the time of applying a voltage V _2. There is a relationship of V ₁ <V ₂ <V _m among V _m , V ₂ , and V ₁ . If the applied voltage of the motor M is constant, when the load is small, the rotational speed N of the motor M is increased and the current I is decreased. When the load is large, the rotational speed N of the motor M is decreased and the current is decreased. I increases. Further, if the load is the same, when the applied voltage V of the motor M is changed, the rotational speed N of the motor M changes, and the rotational speed N increases as the applied voltage V increases. In the present invention, even if the load fluctuates, the applied voltage V is automatically shifted in accordance with the motor current so that the same rotation speed is always obtained if the operation angle of the operation lever 10 is the same. Will be described later.

Next, the operation of the forklift shown in FIG. 1 will be described based on the flowchart shown in FIG. In step S1, the control unit 12 determines whether or not the adjustment switch 11 is turned on. If the adjustment switch 11 is OFF (step S1: NO), the process proceeds to the normal operation mode after step S11. Details of the normal operation mode will be described later. On the other hand, when the operator turns on the adjustment switch 11 (step S1: YES), the operation mode becomes the initial adjustment mode. In the initial adjustment mode, after the forklift is in an empty state in step S2, that is, no load is loaded on the fork 16, the operation of the operation lever 10 is started (step S3). The side shift / rotate mechanism starts operating in an empty state (step S4). Then, the control unit 12 determines whether or not the operation amount (angle) of the operation lever 10 is maximized (step S5). If the operation amount is maximized (step S5: YES), the rated voltage V is applied to the motor M. _m (FIG. 2) is applied to operate the side shift / rotate mechanism of the forklift (step S6). Then, the rotational speed and current of the motor M at this time are measured (step S7). The rotation speed of the motor M can be measured based on the output of the encoder 17, and the current flowing through the motor M can be measured by the current detector 14. The measured number of revolutions is N ₁ in FIG. 2, and the current is I ₁ in FIG. The values of the rotation speed N ₁ and the current I ₁ are stored in the memory of the control unit 12.

Next, it is determined whether or not the rotation speed and current of the motor M have been measured twice (step S8). In this case, since the rotation speed and current are measured only once, the determination in step S8 is NO, and the process proceeds to step S10. In step S10, the forklift is loaded, that is, the fork 16 is loaded. Then, it returns to step S3 and repeats steps S3-S7 according to the procedure mentioned above. That is, when the operation lever 10 is operated (step S3), the motor M rotates and the side shift / rotate mechanism starts operating in a loaded state (step S4), and when the lever operation amount becomes maximum (step S5). : YES), by applying a rated voltage _{V m} to the motor M to operate the side shifting / Roteito mechanism (step S6), and measuring the rotational speed and current of the motor M (step S7). The measured rotation speed is N ₂ in FIG. 2, and the current is I ₂ in FIG. The values of the rotation speed N ₂ and the current I ₂ are stored in the memory of the control unit 12.

Thereafter, it is again determined whether or not the rotation speed and current of the motor M have been measured twice (step S8). In this case, since the rotation speed and current are measured twice, the determination in step S8 is YES, and the process proceeds to step S9. In step S9, based on the values of the rotational speeds N ₁ and N ₂ and the currents I ₁ and I ₂ measured twice in step S7, the control unit 12 obtains a characteristic curve of the motor M (characteristic curve A in FIG. 2). Calculate and store. The characteristic curve A is obtained as a linear function as follows.
N _A = N ₀ −a · I (1)
Here, a is an inclination and is represented by a = (N ₂ −N ₁ ) / (I ₂ −I ₁ ). I is a motor current flowing through the motor M, and N ₀ is the number of rotations of the motor M when I = 0. The control unit 12 stores the motor characteristic curve represented by the above formula (1) in a memory.

  In this way, the characteristic curve A of the motor M is automatically calculated based on the rotational speed and current of the motor M measured in the empty state and the loaded state, and is stored in the memory. The initial adjustment work is completed.

  Next, the procedure in the case of normal operation will be described. If the adjustment switch 11 is OFF in step S1 (step S1: NO), the process shifts to the normal operation mode. In normal operation, when the operation of the operation lever 10 is started (step S11), the motor M rotates and the forklift side shift / rotate mechanism starts operation (step S12). Then, the desired rotational speed of the motor M is determined from the operation angle of the operation lever 10 (step S13). The operation angle of the operation lever 10 can be detected by, for example, a potentiometer, and the desired rotation speed of the motor M is uniquely determined in accordance with the detected operation angle. Subsequently, the current of the motor M is detected by the current detector 14 (step S14). Based on the desired rotational speed and motor current obtained in this way, the control unit 12 outputs the motor voltage V for obtaining the desired rotational speed from the above-described characteristic curve A stored in the memory, that is, output from the chopper output unit 13. Output voltage is calculated (step S15). This will be described in detail below.

In FIG. 2, the characteristic curve B represents the characteristic when the voltage V ₁ is applied to the motor M, and is represented by N _B = n ₀ −a · I as in the equation (1). The following relationship is established between the characteristic curve B and the characteristic curve A.
_{V 1 / V m = N B} / N A ... (2)
Now, the desired rotational speed determined by the operation angle of the operating lever 10 and n ₁ in FIG. 2, when the motor current at this time is assumed to be I _1, the motor voltages V ₁ for obtaining a desired rotational speed n ₁ is From the formula (1) and the formula (2), it is calculated by the following formula as I = I ₁ and N _B = n ₁ .
V ₁ = n ₁ / (N ₀ −a · I ₁ ) × V _m (3)
Here, when the motor current load of the motor M is increased becomes I _2, to obtain the same desired rpm n _1, from 2, that may be increased motor voltage from V ₁ to V ₂ Recognize. The motor voltage V ₂ is expressed by the following equation.
V ₂ = n ₁ / (N ₀ −a · I ₂ ) × V _m (4)
From the equations (3) and (4), the motor voltage V for obtaining the same desired rotational speed n irrespective of the load change can be expressed by the following equation.
V = n / (N ₀ −a · I) × V _m (5)

In equation (5), the desired rotational speed n is determined by the operating angle of the operating lever 10, the motor current I is determined by the detected value of the current detector 14, and each value of N ₀ , a, V _m is preliminarily expressed as a characteristic curve A Stored in memory. Therefore, in step S15 of FIG. 3, the operation of the operation lever 10 is performed by performing the calculation of the above equation (5) using the desired rotational speed n determined in step S13 and the motor current I detected in step S14. A motor voltage V for automatically obtaining a desired rotational speed n corresponding to the angle is automatically calculated. And this voltage is output from the chopper output part 13, and is applied to the motor M (step S16). As a result, the motor M always rotates at the same rotation speed with respect to the same lever operation angle regardless of the magnitude of the load.

  As described above, in the above-described embodiment, during the initial adjustment, the motor characteristic curve is obtained from the rotational speed and current of the motor M measured in the empty state and the loaded state, and stored, and this is stored during normal operation. Based on the desired rotational speed n corresponding to the operation amount of the operation lever 10 and the detected motor current I, a motor voltage V for obtaining the desired rotational speed n is calculated using a motor characteristic curve, and the motor M is calculated with this voltage. I try to drive it. For this reason, once the motor characteristic curve is calculated and stored, the motor rotation speed becomes a constant value corresponding to the operation amount of the operation lever 10 with reference to this characteristic curve during the next normal operation. The motor voltage V is automatically adjusted according to the load (motor current). Therefore, if the operation amount of the operation lever 10 is the same, the same motor rotation speed is always obtained regardless of the load, so that the operator only has to operate the operation lever 10 to obtain the desired rotation speed. Is very clear and easy to understand.

  In addition, a motor characteristic curve is obtained for each individual forklift in the initial adjustment, and the motor voltage V is calculated on the basis of the motor characteristic curve. Therefore, even if the motor rotation speed varies due to individual differences such as the motor M and the speed reduction mechanism 15. This variation can be absorbed. As a result, even when driving by changing to a forklift of another model equipped with the same type of cargo handling mechanism, the motor speed is always the same if the operation amount of the operation lever 10 is the same, so the operator has the same operation feeling regardless of the model. You can drive at.

  In addition, when obtaining the motor characteristic curve in the initial adjustment, the rotation speed and current of the motor M are measured twice in the above-described embodiment in the empty load state and the load state. You may measure twice. However, when one side is in an empty state as in the above embodiment, the load can be loaded only once, so that the initial adjustment can be performed efficiently.

  In the above embodiment, a forklift provided with a side shift mechanism and a rotation mechanism is taken as an example of an electric cargo handling mechanism, but the present invention is not limited to this. For example, the present invention can also be applied to a forklift provided with a reach mechanism or a lift mechanism driven by an electric motor. Furthermore, the present invention can be applied not only to forklifts but also to cargo handling devices such as cranes.

It is a figure which shows schematic structure of the forklift of this invention provided with the electrically-driven cargo handling mechanism. It is the characteristic curve which showed the characteristic of the motor. It is the flowchart which showed operation | movement of a forklift. It is a figure which shows schematic structure of the conventional forklift provided with the electrically-driven cargo handling mechanism. It is the characteristic curve which showed the characteristic of the motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Operation lever 11 Adjustment switch 12 Control part 13 Chopper output part 14 Current detector 15 Deceleration mechanism 16 Fork 17 Encoder M Motor A, B, C Motor characteristic curve

Claims (3)

In a cargo handling apparatus equipped with an electric cargo handling mechanism driven by a motor,
Measuring means for applying a predetermined voltage to the motor in two different loading states and measuring the rotational speed and current of the motor in each loading state;
Calculation means for obtaining a characteristic curve of the motor based on the rotation speed and current measured by the measurement means;
Storage means for storing the motor characteristic curve obtained by the calculation means;
A determining means for determining a desired rotational speed of the motor based on an operation amount of an operation lever during normal operation;
Current detection means for detecting current flowing in the motor during normal operation;
Based on the desired rotation speed determined by the determination means, the current detected by the current detection means, and the motor characteristic curve stored in the storage means, a desired rotation speed corresponding to the operation amount of the operation lever is obtained. Voltage calculating means for calculating a motor voltage to obtain;
Motor driving means for driving the motor by outputting the motor voltage calculated by the voltage calculating means;
A cargo handling apparatus characterized by comprising: The cargo handling device according to claim 1,
Provide a switching means for switching the operation mode of the cargo handling device between the normal operation mode and the initial adjustment mode,
When the initial adjustment mode is set by the switching means, the rotational speed and current of the motor are measured by the measurement means, the motor characteristic curve is calculated by the calculation means, and the motor characteristic curve is stored in the storage means. ,
When the normal operation mode is set by the switching means, the determination means determines the desired rotation speed, the current detection means detects the current, the voltage calculation means calculates the motor voltage, and the motor drive means drives the motor. A cargo handling device characterized in that In the cargo handling apparatus according to claim 1 or 2,
The cargo handling device, wherein the measuring means measures the rotational speed and current of the motor in each of an empty load state and a load loaded state.

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