Motor control system

Abstract

In electric hoists, electric chain blocks, overhead cranes, and arm-type cranes, inching (shortening) operations are used to move the gripped load in minute increments for positioning and alignment work. This invention provides a control method for electric motors that improves the operability and functionality of this inching operation for positioning and alignment work. [Solution] If the ON / OFF operations of the lifting push switches 2-5, input from the manual operation switch 1, are performed continuously within a predetermined time, it is determined to be a continuous ON / OFF inching operation mode. By driving the electric motor 10 at a specified constant speed (extremely low speed) in this mode, the electric motor 10 is driven more accurately and stably, improving the workability of alignment work and positioning operations.

Description

Technical Field

[0001] The present invention relates to a control method for an electric motor, and particularly to an electric hoist, an electric chain block, and an electric winch having a driving function by an electric motor in the vertical direction, a ceiling crane having a driving function by an electric motor in the horizontal direction in addition to the vertical direction, and an electric motor which is a driving source of a device involving an inching operation such as an industrial robot. It is useful when applied to the drive control of the electric motor.

Background Art

[0002] Regarding the conventional technology, an electric hoist will be taken as an example for explanation. When looking at the electric motor control of a conventional electric hoist from the electric motor drive unit, it can be divided into two types. One is configured by using an electromagnetic contactor in the electric motor drive unit, and by opening and closing the electromagnetic contactor in response to a lifting and lowering command from the operation unit, a three-phase AC power supply is directly supplied to the electric motor through the electromagnetic contactor to drive the electric motor and perform a lifting and lowering operation (hereinafter referred to as an electric hoist of the electromagnetic contactor method), and the other is configured by a high-performance inverter drive circuit that can vary the rotation speed of the electric motor in the electric motor drive unit. At the start, in response to a lifting and lowering command from the operation unit Acceleration control is performed to move at a specified lifting and lowering speed, and also has a function of performing deceleration control from the specified lifting and lowering speed to stop at the time of stopping, and performs a lifting and lowering operation (hereinafter referred to as an electric hoist of the inverter method).

[0003] Figs. 10 to 12 are explanatory diagrams showing various manual operation switches applied to a control system of a conventional electric hoist having a lifting electric motor as a control object. As shown in Fig. 10, a manual operation switch 30 showing an operation panel specification B has a push switch 31 for upward operation and a push switch 32 for downward operation.

[0004] As shown in Fig. 11, a manual operation switch 33 showing an operation panel specification C has a push switch 34 for high-speed upward operation, a push switch 35 for high-speed downward operation, a push switch 36 for low-speed upward operation, and a push switch 37 for low-speed downward operation.

[0005] As shown in Figure 12, the manual operation switch 38, which is part of the operation panel specification D, has a push switch 39 for upward operation in two modes, high speed and low speed, and a push switch 40 for downward operation in two modes, high speed and low speed. Here, the push switches 39 and 40 are two-stage action switches, where a light press activates the low-speed mode and a deeper press activates the high-speed mode.

[0006] Figure 13 shows a control system circuit for a conventional electric hoist having an electric motor for lifting and lowering as the controlled object. As shown in the figure, manual operation switches 30, 33, and 38 are used in this electric hoist, and predetermined ON / OFF signals corresponding to the operation are sent from each manual operation switch 30, 33, and 38 to the electric hoist control circuit.

[0007] The electric motor 10 is powered by a single-phase / three-phase (three-phase in Figure 13) AC power supply 6 and driven via the electric motor drive circuit 41. Here, the electric motor drive circuit 41 includes both electromagnetic contactor type and inverter type electric motor drive circuits. A reduction gear 11 is directly connected to the electric motor 10, converting its output from high-speed rotation to low-speed rotation to enable high torque output, and a wire drum 14 is further connected to its output shaft. A wire rope 16 is wound around the wire drum 14, and a load 18 suspended by a hook 17 attached to the lower end of the wire rope 16 can be raised and lowered. If a load chain is used instead of the wire rope 16, a chain wheel is used instead of the wire drum 14, and in this case, the load chain is stored in a chain storage box 15.

[0008] Next, the characteristics and problems of the electromagnetic contactor type electric hoist will be explained. In the control system of the electric hoist shown in Figure 13, manual operation switches 30, 33, and 38 (see Figure 13, the same applies hereafter) are generally used for vertical movement. These manual operation switches 30, 33, and 38 include wireless manual operation switches that are operated wirelessly and wired manual operation switches that are operated by connecting the manual operation switches to the electric hoist body with an electric wire. However, in the electromagnetic contactor type electric hoist described here, regardless of whether it is wired or wireless, it is assumed that the manual operation switch 30 of operation panel specification B, which has an up and down switch as shown in Figure 13, is connected.

[0009] Figure 14 shows the operating state of the lift switch and the timing of the lifting and stopping operations when the manual operation switch 30 is connected to the electromagnetic contactor type electric hoist and the push switch 31 for lifting operation is operated. As shown in the figure, in the motor control system using the electromagnetic contactor, when the push switch 31 for lifting operation of the manual operation switch 30 is turned ON, the electromagnetic contactor for motor drive turns ON, and drive current is supplied to the motor 10, causing it to operate in the upward direction. When the push switch 31 is turned OFF, the electromagnetic contactor turns OFF, and as a result, the drive current to the motor 10 is cut off, and the motor 10 stops.

[0010] In this motor drive control system using electromagnetic contactors, the ON / OFF operation (inching operation) of the push switch 31 and the push switch 32 for lowering is performed in a short time, thereby shortening the time that drive current is supplied to the motor 10, reducing the amount of movement of the lower end hook 17, and enabling alignment and positioning operations.

[0011] In the lifting speed timing diagram in Figure 14, the shaded area indicates the amount of movement (travel distance) by the electric motor. The smaller the area of ​​the shaded part, the smaller the amount of movement during lifting. Therefore, a problem with the electromagnetic contactor system is that when the electric motor drive electromagnetic contactor in the electric motor drive circuit 41 is opened and closed, an excessive current flows through the electromagnetic contactor contacts and the electromagnetic contactor drive circuit, and an arc is generated between the contacts when the contacts are opened and closed. As a result, if the frequency of opening and closing of the electric motor drive electromagnetic contactor increases, the contacts of the electromagnetic contactor wear out and their lifespan is shortened. Furthermore, since the motor is driven by the opening and closing (ON / OFF) control of the electromagnetic contactor, acceleration and deceleration control of the motor is not possible. Consequently, if inching operations are performed repeatedly in a short period of time, the ON / OFF operation of the electric motor may induce vibrations in the mechanical part to which the electric hoist body is attached, which is a disadvantage as it makes alignment work and positioning operations difficult.

[0012] Next, the characteristics and problems of inverter-type electric hoists are described below. In this type of electric hoist, the manual operation switch 33 of the operation panel specification C in Figure 11 is generally used. Figure 15 shows the timing diagram of the upward movement of the electric hoist when the upward switch (push switch 34 for high-speed upward movement or push switch 36 for low-speed upward movement) of the inverter-type electric hoist is operated. In the case of motor control of an inverter-type electric hoist, the upward and downward movement speed of the motor can be variably controlled. Therefore, when the upward switch (push switch 34 for high-speed upward movement or push switch 36 for low-speed upward movement) is turned ON to cause the motor 10 to move upward, acceleration control is performed for a specified acceleration time until the specified upward speed is reached. Also, when the manual switch 33 is turned OFF to stop, deceleration control is performed for a specified deceleration time to stop the hoist.

[0013] The above explanation describes the upward movement when the upward switch (push switch 34 for high-speed upward movement or push switch 36 for low-speed upward movement) is operated. However, similarly, when the downward switch (push switch 35 for high-speed downward movement or push switch 37 for low-speed downward movement) is operated, acceleration and deceleration control can be used to start and stop the downward movement as well.

[0014] One advantage of the inverter system is that, compared to the motor drive control system using electromagnetic contactors, the inverter system allows for acceleration and deceleration control, preventing excessive motor current flow or torque generation during motor startup and shutdown. Furthermore, acceleration and deceleration control results in smoother motor operation, making it very gentle on the motor drive circuit and the mechanical parts connected to the motor. However, even in inching operations, acceleration and deceleration are involved during startup and shutdown. Therefore, even when the lifting switch is turned OFF from an operating state, the motor does not stop immediately but continues to move due to deceleration control after being turned OFF. This presents a problem in that it becomes difficult to finely adjust the amount of movement even with inching operations.

[0015] Furthermore, Patent Documents 1 to 3 are publicly known as prior art documents related to the present application. In the electric hoist described in Patent Document 1, an electromagnetic contactor type electric hoist is employed, which can be realized with low component costs, and when the low-speed operation switch is pressed, the intervals between the operation (ON control) and stopping (OFF control) of the electric motor are automatically controlled by timers. In this case, as described in Patent Document 1, the electromagnetic contactor type is inexpensive, but unlike the inverter type, the electric motor is started and stopped frequently by the ON / OFF operation of the electromagnetic contactor, so the problems of inching operation of the electromagnetic contactor type, which have been pointed out in the past, remain unresolved, such as the problem of damaging the electric motor, electromagnetic contactor and electromagnetic brake, shortening their lifespan, and the problem of inducing vibrations in the mechanical parts to which the electric hoist body is attached and the load being handled due to frequent sudden acceleration and sudden stopping, making alignment work difficult and causing the lifted load to collapse.

[0016] In the inverter-type electric hoist described in Patent Document 2, in order to improve the instability during inching operations (switch ON / OFF operations) and stabilize the inching operation, the motor drive time and motor rest time for each inching operation are predetermined, so that the inching operation is performed with the same motor drive time and motor rest time regardless of what operation the operator performs during the inching operation, thereby fixing the amount of movement per operation and stabilizing the inching operation.

[0017] While this control method is thought to stabilize the motor's operation during inching compared to other control methods that do not manage the ON / OFF time during inching, it has drawbacks. Since the amount of movement during inching is predetermined, it is necessary to repeat the inching operation multiple times if the travel distance is long. Furthermore, because the control method described in the patent has a predetermined minimum travel distance, it becomes impossible to perform positioning work using inching if a distance smaller than the minimum travel distance is required.

[0018] To solve the problems caused by the inching operation and motor inching motion described above, an inverter-type electric hoist has been proposed that completely eliminates the use of the inching operation and motor inching motion described in Patent Document 3. In this inverter-type electric hoist, the push switches 31 and 32 of the manual operation switch 38, which is the operation panel specification D shown in Figure 12, are operated to enable two-stage switching between high speed and low speed by the amount of the push down of the two-action operation, and by adding a low-speed operation mode, the inching operation is made unnecessary.

[0019] In the electric hoist described in Patent Document 3, acceleration control is retained when the lifting switch is turned ON, but deceleration control is not performed when the switch is turned OFF. This suppresses the flow of the load when the switch is OFF, making alignment and positioning operations easier. However, because the deceleration operation, which is an advantage of the inverter system, is prohibited, there is a disadvantage in that it is more likely to induce mechanical vibration. Furthermore, because it uses a special long-stroke button switch with a two-stage action operation, the manual operation switch on which this button switch is mounted has a special structure, and there are problems in that there are few types of switches with two-stage operation functionality and they are difficult to obtain. In addition, because the switch structurally requires a long-stroke mechanical structure, it cannot be used in thin, small manual operation switches on which surface-mount switches such as membrane switches are mounted. [Prior art documents] [Patent Documents]

[0020] [Patent Document 1] Japanese Patent Publication No. 2004-175464 [Patent Document 2] Japanese Patent Publication No. 9-323888 [Patent Document 3] Japanese Patent Publication No. 4-260600 [Overview of the project] [Problems that the invention aims to solve]

[0021] In both the electromagnetic contactor type electric hoist of Patent Document 1 and the inverter type electric hoist of Patent Document 2, when the motor drive unit is ON, the motor rotates by operating the lifting switch of the manual operation switch, and when the drive unit is OFF, the motor stops, which remains unchanged. The operator observes the movement (amount of movement) of the hook at the lower end of the electric hoist or the cargo handling object when the electric motor is in the ON operation (rotation operation) and OFF operation (stop operation), and performs the inching operation (ON / OFF operation) of the lifting switch of the manual operation switch. However, when the hook or the cargo handling object at the lower end of the electric hoist vibrates or swings due to the inching operation, or flows due to the deceleration operation, it becomes difficult to perform the alignment work and the positioning operation, and there is a problem that the work takes a long time. Furthermore, when the amount of movement per inching operation is large compared to the small amount of movement to the target position, there are also problems such as difficulty in performing the alignment work.

[0022] In view of the above prior art, an object of the present invention is to provide a control method for an electric motor that can favorably control the electric motor as a drive source of an object and efficiently and favorably execute the positioning etc. of the object.

Means for Solving the Problems

[0023] The present invention for solving the above problems is characterized by the following points. The first aspect of the present invention is in a control method for an electric motor including an electric motor driven by inverter control and a manual operation switch for driving or stopping the electric motor, continuous ON / OFF inching operation detection means for detecting that ON operation and OFF operation are continuously operated within a preset time by the manual operation switch, and continuous ON / OFF inching operation count means for counting the continuous ON / OFF inching operations detected by the continuous ON / OFF inching operation detection means. While the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation counting means exceeds the preset continuous ON / OFF operation setting count value, it is determined as the continuous inching operation mode, and the motor is configured to be driven at a specified constant operation speed.

[0024] The second aspect of the present invention is In the motor control method described in the first aspect, in the continuous ON / OFF inching operation detection means, when determining whether the ON operation state time and OFF operation state time of the manual operation switch are within the set operation time, the ON operation determination time and OFF operation determination time can be arbitrarily set respectively.

[0025] The third aspect of the present invention is In the first or second aspect, when determining whether the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation counting means exceeds the continuous ON / OFF operation setting count value, the continuous ON / OFF operation setting count value can be arbitrarily set.

[0026] The fourth aspect of the present invention is In any one of the first to third aspects, when it is detected by the continuous ON / OFF inching operation detection means that the ON state time of the operation switch exceeds the ON operation determination time, it is determined as the normal operation mode, and the motor is driven at the specified operation speed in the normal operation mode. At the same time, when it is detected by the continuous ON / OFF inching operation detection means that the OFF state time of the operation switch exceeds the OFF operation determination time, it is determined that the motor is in the operation stop mode, and the driving of the motor is stopped.

[0027] The fifth aspect of the present invention is In any one of the first to fourth embodiments, if the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation count means is smaller than the continuous ON / OFF operation setting value, it is determined that the system is in an intermediate operation mode before transitioning to the continuous inching operation mode, and the system is equipped with a function to operate the motor at a specified operating speed in the intermediate operation mode by performing acceleration control of the motor when the operation switch is turned ON, and deceleration control of the motor when the operation switch is turned OFF.

[0028] A sixth aspect of the present invention is: In any one of the first to fifth embodiments, when a continuous inching operation is being performed, if the continuous ON / OFF inching operation detection means detects that the ON / OFF inching operation by the switch operation has been interrupted, the system is configured to transition from the continuous inching operation mode to the operation stop mode and perform rapid stop control without deceleration. [Effects of the Invention]

[0029] According to the present invention, even when inching is performed using an operating switch, the stopping operation of the electric motor can be smoothly controlled. Therefore, for example, a load suspended by a hook at the lower end of a cargo handling device such as an electric hoist can be lifted and lowered smoothly and stably at a constant lifting speed. As a result, positioning and alignment operations can be performed accurately and quickly without causing the electric hoist to vibrate or shake.

[0030] Such effects can be applied to the control of electric motors in devices whose drive is controlled by the control method according to the present invention and which are used for positioning, such as industrial robots and all other devices that perform positioning accompanied by inching operations. [Brief explanation of the drawing]

[0031] [Figure 1] An explanatory diagram showing specification A of the control panel for a manual operation switch used in an electric hoist to which an embodiment of the present invention is applied. [Figure 2] A diagram illustrating the configuration of an electric hoist to which the electric motor control method according to an embodiment of the present invention is applied. [Figure 3A] A diagram illustrating the timing of the operation when transitioning from the normal operation mode to the continuous inching operation mode via the intermediate operation mode according to an embodiment of the present invention. [Figure 3B] An operation timing diagram for detecting continuous ON / OFF inching operations from the ON state of a low-speed lifting switch according to an embodiment of the present invention. [Figure 4A] A diagram illustrating the timing of the operation when transitioning from the operation stop mode to the continuous inching operation mode via the intermediate mode, according to an embodiment of the present invention. [Figure 4B] An operation timing diagram for detecting continuous ON / OFF inching operations from the OFF state of a low-speed lifting switch according to an embodiment of the present invention. [Figure 5] A main control flow diagram according to an embodiment of the present invention. [Figure 6] A control flow diagram of the execution mode setting process based on the operation state of the lifting switch according to an embodiment of the present invention. [Figure 7] A flow diagram of an intermediate operation mode control according to an embodiment of the present invention. [Figure 8] A control flow diagram for a continuous inching operation mode according to an embodiment of the present invention. [Figure 9] A control flow diagram of the normal operation mode according to an embodiment of the present invention. [Figure 10] Diagram B shows the specifications of the control panel for a manual operation switch used in a conventional electric hoist. [Figure 11] Diagram C shows the specifications of the control panel for the manual operation switch used in conventional electric hoists. [Figure 12] Diagram D shows the specifications of the control panel for a manual operation switch used in a conventional electric hoist. [Figure 13] A diagram illustrating the configuration of a conventional electric hoist. [Figure 14] A diagram illustrating the timing of the lifting operation input and the lifting speed of a conventional electric hoist using an electromagnetic contactor system. [Figure 15]A diagram illustrating the timing of the lifting operation input and the lifting speed of a conventional inverter-type electric hoist. [Modes for carrying out the invention]

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, using the application of the present invention to an electric hoist as an example.

[0033] Figure 1 is an explanatory diagram showing a manual operation switch applied to a control system for an electric hoist having an electric motor for lifting and lowering as the controlled object. As shown in Figure 1, the manual operation switch 1, which shows operation panel specification A, has a push switch 2 for high-speed lifting operation, a push switch 3 for high-speed lowering operation, a push switch 4 for low-speed lifting operation, and a push switch 5 for low-speed lowering operation. Here, the surfaces of the push switches 4 and 5 for low-speed lifting operation and low-speed lowering operation in Figure 1 are marked with two arrows: a long arrow and a short, broken arrow. This indicates that each push switch 4 and 5 can be operated in two modes (low speed and very low speed) for lifting and lowering. In this marking, the longer arrow indicates that it can be operated in low-speed operation mode, and the short, broken arrow indicates the very low-speed operation mode by continuous ON / OFF inching operation. Such push switches 4 and 5 can be well formed as membrane switches.

[0034] When using push switches 4 and 5, even when using inexpensive, commonly available single-action push switches or thin, surface-mount switches like membrane switches, instead of special long-stroke switches such as two-action push switches 39 and 40, the alignment and positioning operations described later can be performed smoothly and quickly.

[0035] Figure 2 is a diagram of the configuration of an electric hoist to which the motor control method according to an embodiment of the present invention is applied. In this figure, the same components as those in the conventional electric hoist shown in Figure 13 are not described. The AC voltage supplied from the single-phase / three-phase AC power supply 6 is converted from AC to DC by the converter circuit 7 and converted to a DC voltage. The converted DC voltage is smoothed by the smoothing capacitor 8 and supplied to the inverter-type motor drive circuit 9. The inverter-type motor drive circuit 9 uses the DC voltage output from the converter circuit 7 as a drive power source and, based on the PWM drive signal from the inverter control circuit 13, converts it into an AC voltage (AC current) that drives the motor 10 at a predetermined rotational speed and supplies it to the motor 10.

[0036] The inverter control circuit 13 receives either a wired switch press signal, which is an ON / OFF signal transmitted via a wire from the manual operation switch 1, or a wireless switch press signal, which is an ON / OFF signal transmitted wirelessly from the wireless receiving circuit 12 to the manual operation switch 1, performs predetermined processing, and controls the drive of the motor 10 via the motor drive circuit 9. Thus, in this example, the motor control method according to the present invention is configured with a wired manual operation switch 19 and a wireless manual operation switch 20 having the switch configuration of the manual operation switch 1, and the inverter control circuit 13.

[0037] More specifically, the inverter control circuit 13, although not shown in the diagram, includes a continuous ON / OFF inching operation detection means and a continuous ON / OFF inching operation counting means. The continuous ON / OFF inching operation detection means detects whether the manual operation switch 1 has been continuously operated ON and OFF within a preset time. The continuous ON / OFF inching operation counting means counts the number of consecutive ON / OFF inching operations detected by the continuous ON / OFF inching operation detection means.

[0038] Here, in the continuous ON / OFF inching operation detection means, the ON operation determination time and OFF operation determination time used to determine whether the time of the ON operation state and the time of the OFF operation state of the manual operation switch 1 are within the set operation time are configured to be arbitrarily set. Furthermore, when determining whether the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation count means exceeds the continuous ON / OFF operation setting value, the continuous ON / OFF operation setting value is configured to be arbitrarily set.

[0039] Thus, the inverter control circuit 13 determines that the system is in continuous inching mode as long as the continuous ON / OFF inching operation count value, counted by the continuous ON / OFF inching operation count means, exceeds a preset continuous ON / OFF operation setting value, and drives the electric motor 10 at a specified constant operating speed.

[0040] Furthermore, the inverter control circuit 13 in this embodiment also has the following determination or control functions.

[0041] 1. The continuous ON / OFF inching operation detection means detects the ON state time of the manual operation switch 1. If it is detected that the ON operation judgment time has been exceeded, the system determines that it is in normal operation mode. In this normal operation mode, the inverter control unit 13 drives the motor 10 at the specified operating speed for normal operation mode.

[0042] 2. If the continuous ON / OFF inching operation detection means detects that the OFF state time of the manual operation switch 1 exceeds the OFF operation determination time, it is determined that the device is in operation stop mode, and the electric motor 10 is stopped.

[0043] 3. If the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation count means is smaller than the continuous ON / OFF operation setting value, it is determined that the system is in an intermediate operation mode before transitioning to the continuous inching operation mode. In this intermediate operation mode, the inverter control unit 13 controls the acceleration of the motor 10 when the manual operation switch 1 is turned ON, and controls the deceleration of the motor 10 when it is turned OFF, driving the motor 10 at the specified operating speed for the intermediate operation mode.

[0044] 4. When continuous inching operation continues, if the continuous ON / OFF inching operation detection means detects that the ON / OFF inching operation by the manual switch 1 has been interrupted, the system will switch from continuous inching operation mode to operation stop mode and perform rapid stop control without deceleration.

[0045] In Figure 2, Figures 3A and 4A show the operating state of the push switch 4 for low-speed ascent of the manual operation switch 1, and the timing diagrams of the ascent speed of the electric motor 10 at that time.

[0046] Figures 3A and 4A both show the relationship between the operating state when the push switch 4 for low-speed lifting is pressed and the lifting speed in operation timing diagrams. However, the difference between the two figures is that Figure 3A shows the operation timing diagram when transitioning from the normal operation mode to the continuous inching operation mode via the intermediate mode, while Figure 4A shows the operation timing diagram when transitioning from the operation stop mode to the continuous inching operation mode via the intermediate mode.

[0047] Furthermore, Figures 3A and 4A (a) show the operating state of the low-speed lifting switch, and (b) shows the corresponding operating timing diagram of the lifting speed characteristics of the electric motor 10.

[0048] When the push switch 4 for low-speed ascent of the manual operation switch 1 is operated, the operating state of the push switch 4 for low-speed ascent as seen from the inverter control circuit 13 according to the embodiment of the present invention can be one of the following three states. (a) Switch ON operation state: The state in which the push switch 4 is held in the ON position for a predetermined set time Ton or longer. (i) Switch OFF operation state: A state in which the push switch 4 is held in the OFF state for a predetermined set time Toff. (c) Switch INCH operation state: A state in which the push switch 4 is continuously operated in the ON state and the OFF state within a predetermined set time (Ton, Toff) (hereinafter referred to as the continuous ON / OFF inching operation state).

[0049] In the switch operation states 1 to 3 described above, the predetermined setting times Ton and Toff are times set in advance in this device, and are usually set to approximately 0.3 to 0.8 seconds, respectively.

[0050] Furthermore, as mentioned above, the operating modes of this device when a switch is operated can be divided into the following four operating modes. (a) Normal operation mode: With the push switch 4 for low-speed ascent turned ON, acceleration control is performed up to a preset specified lifting speed, and once the specified lifting speed is reached, the operation is performed at the lifting speed (constant speed) specified for that operation mode. (b) Operation stop mode: An operating mode in which the operation of the electric motor 10 is stopped with the push switch 4 for low-speed ascent turned OFF. (c) Continuous inching operation mode: An operation mode in which the push switch 4 for low-speed lifting is operated in the INCH position, and the number of continuous ON / OFF inching operations exceeds a predetermined number of continuous ON / OFF operation settings Ni, and the motor 10 is operated at the lifting speed specified for that operation mode (a constant speed slower than the normal operation mode), regardless of the ON / OFF operation of the push switch 4. (d) Intermediate operation mode: When the low-speed lifting switch is operated in the INCH position of the switch described in (c) above, and the number of continuous ON / OFF inching operations does not exceed a predetermined set number of continuous ON / OFF operations Ni, when the switch is ON, acceleration control is performed until the specified lifting speed is reached, and when the switch is OFF, deceleration control is performed from the current operating speed until it stops.

[0051] Table 1 summarizes the presence or absence of acceleration / deceleration control and the specified speed for each of the above operating modes (a) to (d). [Table 1]

[0052] To briefly explain the specified speeds in Table 1 above, the specified speeds in intermediate operation mode and continuous inching operation mode are set to be considerably slower than the corresponding speeds in normal operation mode. This is to make it easier to make subtle adjustments to the movement distance during operation in continuous inching mode, and to facilitate alignment and positioning operations.

[0053] Next, we will explain the operation timing diagrams for switching from the normal operation mode (Figure 3A) to the continuous inching operation mode via the intermediate operation mode, and for switching from the operation stop mode (Figure 4A) to the continuous inching operation mode via the intermediate operation mode. First, we will explain the parts that are common to both figures.

[0054] In Figures 3A and 4A, "(1) Switching processing unit to normal operation mode" indicates the timing of operation when the low-speed lifting switch transitions from the (i) switch OFF state to the (a) switch ON state. In this operation, when the low-speed lifting switch is turned ON from the stopped state, the device first switches from the stopped operation mode to the intermediate operation mode and starts the lifting operation. In this intermediate operation mode, the operating speed is limited to the extremely low speed Vc of the specified speed according to Table 1. Subsequently, when the device detects that the low-speed lifting switch is in the (a) switch ON state, that is, that the ON state of the low-speed lifting switch has exceeded the ON state detection time Ton, the device switches from the intermediate operation mode to the normal operation mode and accelerates until it reaches the specified lifting speed Vr of the normal operation mode.

[0055] In this case, when the low-speed lift switch is held down, the acceleration control at startup will be a two-stage acceleration operation as shown in Figures 3A and 4A. However, immediately after the low-speed lift switch is turned ON, it is unclear whether the operator wants to operate in normal operation mode or continuous inching operation mode, so it will start in an intermediate operation mode that can be switched to either operation mode. In actual equipment, when the low-speed lift switch is pressed and the system switches to normal operation mode via the intermediate operation mode, there is only a slight delay in operation during acceleration, and since the acceleration control is continuous, there is no sense of discomfort in operation.

[0056] Next, the continuous ON / OFF inching operation detection process will be explained. In Figure 3A, "(2) Continuous ON / OFF inching operation detection process A" shows the case where the system detects the switch INCH operation state from the normal operation mode with the switch ON state and transitions to the continuous inching operation mode, whereas in Figure 4A, "(2) Continuous ON / OFF inching operation detection process B" shows the case where the system detects the switch INCH operation state from the operation stop mode with the switch OFF state and transitions to the continuous inching operation mode.

[0057] Figure 3B is a detailed explanatory diagram of "(2) Continuous ON / OFF inching operation detection process A" in Figure 3A. Figure 3B shows a case where continuous ON / OFF inching operation is determined to have occurred when the OFF state of continuous ON / OFF inching operation is detected first, followed by the ON state (a total of two times), and then the system switches from the intermediate operation mode to the continuous inching operation mode upon the detection of the next OFF state.

[0058] Figure 4B is a detailed explanatory diagram of "(2) Continuous ON / OFF Inching Operation Detection Processing Section B" in Figure 4A. Figure 4B shows a case where, after detecting the ON state of continuous ON / OFF inching operation first, and then the OFF state in succession (a total of two times), it is determined that continuous ON / OFF inching operation is occurring, and from the next detection of the ON state, the system switches from the intermediate operation mode to the continuous inching operation mode.

[0059] In the examples in Figures 3B and 4B, when the number of consecutive ON / OFF operations Ni is set to 2, that is, consecutive short-duration inching operations are counted as one ON / OFF state each (a total of 2 times), and the switch to the continuous inching operation mode is performed from the next switch state (count number 3). To ensure a reliable switch to the continuous inching operation mode, the number of consecutive ON / OFF operations Ni may be increased, but in that case, the switch to the continuous inching operation mode will be delayed.

[0060] Next, we will explain "(3) Stop Processing Unit for Continuous Inching Operation Mode," which is common to both Figure 3A and Figure 4A. When the continuous inching operation mode ends, the stop process is executed immediately without deceleration control. When the continuous inching operation mode ends, the switch is in the OFF state, but even in this state, the predetermined set time Toff is still operating. Therefore, when switching from the continuous inching operation mode to the stop operation mode, for example, a rapid stop is performed to minimize the flow distance of the hook 17 at the lower end of the electric hoist (see Figure 2; the same applies hereafter). This is why the deceleration control for the continuous inching operation mode is set to "none" in Table 1. Furthermore, if it is necessary to reduce the amount of flow movement when the continuous inching operation mode ends, it is necessary to set the detection time Toff for the switch OFF state to a shorter value.

[0061] As can be seen from Figures 3A and 4A, the lifting speed in continuous inching operation mode is at a constant, extremely low speed, even when the low-speed lifting switch is being used for inching. In conventional electric hoist inching operations, the electric motor 10 was started and stopped during the inching operation, making it impossible to move the load suspended by the lower hook 17 in a stable manner. However, in the present invention, the lifting operation can be performed at a constant, extremely low speed set by the user, so the load lifted by the electric hoist can be moved stably even during inching operations.

[0062] The conventional manual operation switch 33 shown in Figure 13 could operate at two stable lifting speeds (high speed / low speed) in either the upward or downward direction. However, when extremely low-speed operation is required for alignment work or positioning operations, the high-speed and low-speed lifting switches of the conventional manual operation switch 33 alone are insufficient. It is necessary to add an extremely low-speed operation switch to the manual operation switch 33, which enables extremely low-speed operation. As a result, the lifting switch had to be a panel specification equipped with a total of six lifting switches, three types (high speed / low speed / extremely low speed) for both the upward and downward directions.

[0063] On the other hand, if the manual operation switch 1 equipped with a continuous inching operation mode according to the embodiment of the present invention shown in Figure 1 is used, it is possible to provide a stable, extremely low-speed lifting operation function even with the same lifting switch hardware configuration as the manual operation switch 33 shown in Figure 11. Furthermore, even if the manual operation switch 30 is equipped with only one push switch each for lifting and lowering operations, it is possible to provide a stable, low-speed lifting operation function by incorporating the continuous inching operation mode function according to the present invention.

[0064] Next, let's consider the actual device and set the speeds of the push switches 2-5 for lifting and lowering the manual operation switch 1 shown in Figure 1. For example, let's assume that the lifting speed setting for the high-speed lift switch is set to 100% (the highest possible speed), the lifting speed setting for the normal operation mode of the low-speed lift switch is set to 10%, and the lifting speed setting for the continuous inching operation mode is set to 1%. With these speed settings, if we assume that the maximum lifting speed when operating the high-speed lift and high-speed lower switches in this device is 20 m / min (100%), then when the low-speed lift / low-speed lower switch is operated in normal operation mode, the set lifting speed will be 20 m / min × 10% = 2 m / min. Furthermore, when the same switch is operated in continuous inching operation mode, the set lifting speed will be 20 m / min × 1% = 0.2 m / min. The results above are summarized in Table 2.

[0065] [Table 2]

[0066] In Table 2 above, the set lifting speed is shown as a percentage of the maximum lifting speed. A positive percentage represents upward movement, and a negative percentage represents downward movement.

[0067] Table 2 shows the same lifting / lowering speed set for both the high-speed ascent / high-speed descent switch and the low-speed ascent / low-speed descent switch, but it is of course possible to set different speeds for each direction depending on the work being done.

[0068] In the example settings in Table 2, the continuous inching operation mode was not set for the high-speed lift (up / down) switch. However, by adding the continuous inching operation mode to this switch, it is possible to set four stable lifting speeds for each of the two operation switches in the vertical direction.

[0069] Next, the control flow of the operating mode of an electric hoist to which an embodiment of the present invention is applied will be described. Figure 5 shows the main control processing flow of this control process. First, in the initialization process, the continuous ON / OFF inching operation counter, which determines whether or not to switch to the continuous inching operation mode, is cleared to 0 (ST(a)). Next, the state of the lifting switch (including the up switch and down switch) can be one of the switch operation states (a) to (c), and the state of each lifting switch is detected to set the operating mode to be executed in the next process (one of continuous inching operation mode, normal operation mode, intermediate operation mode, or operation stop mode) (ST2). If the continuous inching operation mode is set as a result of setting the execution operating mode, the continuous inching operation mode process (ST4) is executed; if the normal operation mode is set, the normal operation mode process (ST5) is executed; if the intermediate operation mode is set, the intermediate operation mode process (ST6) is executed; and if the operation stop mode is set, the immediate stop process (ST7) is executed. When the processing of any of the operating modes ST4 to ST7 is completed, the process returns to ST2.

[0070] Next, the control flow for setting the execution mode based on the operation status of the lift / lower switch (SW) in Figure 6 will be explained. In this control flow, the state of pressing the lift / lower switch is input, and the execution mode to be executed is set based on that switch press information. First, the state of pressing the lift switch and the lower switch is read (ST201). It is checked whether the lift or lower switch is in the ON state (ST202), and if the switch is in the ON state, it is checked whether the ON switch is the same switch as the previous one (ST203), and if it is the same, the process proceeds to the decision process ST205. If the switch being pressed in the decision process ST203 is different from the switch that was pressed last time, the continuous ON / OFF inching operation counter is set to 1 (ST211), the execution mode is set to "intermediate operation mode" (ST210), and this process is terminated. If the switch remains pressed for a predetermined amount of time during the decision process ST205, the continuous ON / OFF inching operation counter is reset to 0 (ST212), the execution mode is set to "normal operation mode" (ST213), and this process is terminated.

[0071] In decision processing ST205, if the switch has not been in the ON state for a predetermined time Ton, the next decision processing ST206 checks whether the current ON or OFF state of the switch is different from the previous ON state. If the ON / OFF pressing state is different, the continuous ON / OFF inching operation counter is incremented by 1 (ST207). If it is the same, the counter is not incremented, and the next decision processing ST208 is executed. ST208 checks whether the continuous ON / OFF inching operation counter exceeds the preset number of continuous ON / OFF operations Ni. If it exceeds the set number Ni, the execution operation mode is set to "continuous inching operation mode" (ST209), and this process is terminated. If it does not exceed the set number Ni, the execution operation mode is set to "intermediate operation mode" (ST210), and this process is terminated. The continuous inching operation mode detection process example shown in Figures 3B and 4B is when the set number Ni is 2.

[0072] If the switch is in the OFF state in ST202, it is checked whether a predetermined time has elapsed since the switch was in the OFF state (ST204). If so, the continuous ON / OFF inching operation counter is reset to 0 (ST214), the execution mode is set to "operation stop mode" (ST215), and this process is terminated. If the switch has not been in the OFF state since ST204, the process is moved to the decision process ST206, as it may be in continuous inching operation mode or intermediate operation mode. The following is the same as the explanation of the decision process ST206 described above.

[0073] Next, the intermediate operation mode processing shown in Figure 7 will be explained. First, it is checked whether the up or down switch is in the ON state (ST601). If either of the switches is in the ON state, the determination process ST602 checks whether the up switch or the down switch is in the ON state. If the up switch is in the ON state, the intermediate operation mode movement flag is set to the "up flag" (ST603), and it is then checked whether the device is operating at the specified up speed Vc during continuous inching operation mode (ST604). If the speed has been reached, this process is terminated; otherwise, acceleration control is performed in the upward direction (ST605), and this process is terminated.

[0074] On the other hand, if the descent switch is ON in ST602, the intermediate operation mode movement flag is set to the "descent flag" (ST608), and it is further checked whether the device is descending at the specified descent speed Vc in continuous inching operation mode (ST609). If the speed has been reached, this process is terminated; otherwise, acceleration control is performed in the descent direction (ST610), and this process is terminated.

[0075] In the judgment process ST601 described above, if both the up / down switches are in the OFF state, it is checked whether the unit is in a stopped state (ST606). If it is stopped, this process is terminated; otherwise, deceleration control is performed (ST607), and this process is terminated. The intermediate operation mode shift flag set in this process will be used in the next continuous inching operation mode process.

[0076] Next, the continuous inching operation mode processing shown in Figure 8 will be explained. First, the intermediate operation mode movement flag is checked (ST401). If the upward flag is set, it is checked whether the machine is operating upward at the specified speed Vc of the continuous inching operation mode (ST403). If the speed has been reached, this process is terminated. If the speed has not been reached, acceleration control is performed in the upward direction for a predetermined acceleration time (ST404), and this process is terminated. In the decision process ST401, the intermediate operation mode movement flag is checked. If the downward flag is set, it is checked whether the machine is operating downward at the specified speed Vc of the continuous inching operation mode (ST405). If the speed has been reached, this process is terminated. If the speed has not been reached, acceleration control is performed in the downward direction for a predetermined acceleration time (ST406), and this process is terminated.

[0077] Next, the normal operation mode processing shown in Figure 9 will be explained. First, the pressing state of the up or down switch is checked (ST501). If the up switch is ON, it is checked whether the device is moving upward at the specified speed Vr for the normal operation mode (ST502). If the speed has been reached, this process is terminated. If the speed has not been reached, acceleration control is performed in the upward direction for a predetermined acceleration time (ST503), and this process is terminated. In the decision process ST501, the pressing state of the up or down switch is checked (ST502). If the down switch is ON, it is checked whether the device is moving downward at the specified speed Vr for the normal operation mode (ST504). If the speed has been reached, this process is terminated. If the speed has not been reached, acceleration control is performed in the downward direction for a predetermined acceleration time (ST505), and this process is terminated.

[0078] The embodiments of the present invention have been described above using an electric hoist as an example. However, the electric motor control method according to the present invention can be widely applied as a control system for controlling electric motors that serve as the drive source for mechanical devices realized in a wide range of industrial fields, such as those used for positioning objects and handling cargo. In other words, it can be applied not only to electric hoists, but also to electric chain blocks and electric hoists that are electric motor-driven and equipped with lifting speed adjustment functions such as inverters. Furthermore, in addition to devices that have an electric motor drive function in the vertical direction, the embodiments of the present invention can also be applied to devices that have an electric motor drive function in the horizontal direction, such as overhead cranes and arm-type cranes that have an electric motor drive function for handling cargo in a three-dimensional direction, and robots that can be operated manually for inching.

[0079] As described above, the present invention offers the advantage of enabling smooth and accurate inching operations for alignment and positioning operations by incorporating a continuous inching operation mode function, compared to conventional motor-driven devices that have a switch for manually driving an electric motor mounted on the device and have performed alignment and positioning operations by inching operations of the switch. [Explanation of symbols]

[0080] 1. Manual operation switch 2. Push switch for high-speed lifting 3. Push switch for high-speed descent 4. Push switch for low-speed ascent 5. Push switch for slow descent 6. Single-phase / Three-phase AC power supply 7. Converter (AC to DC conversion) circuit 8. Power supply smoothing capacitors 9. Inverter-type motor drive circuit 10 Electric motor 11 Reducer 12 Wireless receiving circuit 13 Inverter control circuit 14. Wire drum (chain wheel in the case of a load chain) 15 Chain storage box 16. Wire rope (or load chain) 17 hooks 18. Cargo handling equipment 19 Wired manual operation switch 20 Wireless manual operation switch via manual operation switch 21 Electric hoist body

Claims

1. In a control system for an electric motor comprising an electric motor driven by inverter control and a manual operation switch for driving or stopping the electric motor, The manual operation switch is used to detect whether the ON and OFF operations are performed consecutively within a preset time, and the system includes a continuous ON / OFF inching operation detection means. The system includes a continuous ON / OFF inching operation counting means for counting consecutive ON / OFF inching operations detected by the continuous ON / OFF inching operation detection means, A motor control method characterized in that, as long as the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation count means exceeds a preset continuous ON / OFF operation setting value, it is determined to be in continuous inching operation mode, and the motor is driven at a specified constant operating speed.

2. The control method for an electric motor according to claim 1, characterized in that the continuous ON / OFF inching operation detection means allows arbitrary setting of the ON operation determination time and the OFF operation determination time when determining whether the time of the ON operation state and the time of the OFF operation state of the manual operation switch are within a set operation time.

3. The control method for an electric motor according to claim 1 or 2, characterized in that when determining whether the continuous ON / OFF inching operation count value, which has been counted by the continuous ON / OFF inching operation count means, exceeds the continuous ON / OFF operation setting value, the continuous ON / OFF operation setting value can be arbitrarily set.

4. If the continuous ON / OFF inching operation detection means detects that the ON state time of the operation switch exceeds the ON operation determination time, it is determined to be in normal operation mode, and the motor is driven at the specified operating speed in the normal operation mode, The motor control method according to any one of claims 1 to 3, characterized in that, if the continuous ON / OFF inching operation detection means detects that the OFF state time of the operation switch exceeds the OFF operation determination time, it is determined that the motor is in operation stop mode and the motor is stopped.

5. The motor control method according to any one of claims 1 to 4, characterized in that, if the continuous ON / OFF inching operation count value counted by the continuous ON / OFF inching operation count means is smaller than the continuous ON / OFF operation setting value, it is determined that the motor is in an intermediate operation mode before transitioning to the continuous inching operation mode, and the motor is accelerated when the operation switch is turned ON, and decelerated when the operation switch is turned OFF, thereby moving the motor at the specified operating speed in the intermediate operation mode.

6. A control method for an electric motor according to any one of claims 1 to 5, characterized in that, when a continuous inching operation is continued, if the continuous ON / OFF inching operation detection means detects that the ON / OFF inching operation by the switch operation has been interrupted, the motor transitions from the continuous inching operation mode to the operation stop mode and performs rapid stop control without deceleration operation.

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