A work machine, a control system for a work machine, and a method for controlling a work machine.

Abstract

In a work machine having a work tool that performs holding and releasing operations for an object, an abnormality in the release permission switch for the work tool is determined. [Solution] The forklift 1 includes an operating lever 21 that is operated to operate the clamping device 10, a drive system 40 capable of driving the clamping device, a release permission switch 23 for allowing or prohibiting the release operation of the clamping device, and a controller 30 that controls the drive system to allow the clamping device to perform a release operation when the release permission switch is on, and controls the drive system to prohibit the release operation of the clamping device when the release permission switch is off. The release permission switch includes first and second switches sw1 and sw2, and the controller is supplied with first and second input signals s1 and s2 from the first and second switches, and determines an abnormality of the release permission switch based on the relationship between these signals.

Description

[[Technical Field]]

[0001] The present invention relates to the technical field of a working machine having a working tool capable of performing a holding operation for holding an object and a releasing operation for releasing the held object. [[Background Art]]

[0002] This type of technology is described, for example, in Patent Document 1. Specifically, Patent Document 1 describes a technology related to a clamp device as a working tool (attachment) applicable to a forklift. This clamp device is configured to switch between a holding operation for holding (clamping / gripping) an object and a releasing operation for releasing (releasing) the held object. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2005-263410 [[Brief Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In the working machine having a working tool (clamp device) capable of performing a holding operation and a releasing operation of an object as described above, if the working tool erroneously performs the releasing operation while holding the object, the object will be dropped. Therefore, in general, a release permission switch for permitting or prohibiting the releasing operation of the working tool is provided. Accordingly, the releasing operation of the working tool is permitted only when the release permission switch is on, and when the release permission switch is off, the releasing operation of the working tool is prohibited, thereby preventing the working tool from erroneously performing the releasing operation. However, when an abnormality occurs in such a release permission switch, unintended releasing operation may not be prevented in some cases.

[0005] Therefore, the present invention aims to determine an abnormality in a release permission switch that permits the release operation of a work tool in a work machine having a work tool capable of holding and releasing an object. [Means for solving the problem]

[0006] In one aspect of the present invention, the work machine comprises a main body; a work tool that is operable relative to the main body and capable of performing a holding operation for holding an object and a release operation for releasing the held object; a drive system for operating the work tool; an operating device for receiving operations for operating the work tool; a release permission switch that includes a plurality of switches and is switched on and off to permit or prohibit the release operation of the work tool, with the state of each of the plurality of switches switching according to the on or off switch; and a controller that controls the drive system to cause the work tool to perform a release operation in response to the operation of the operating device when the release permission switch is on, and controls the drive system to prohibit the release operation of the work tool when the release permission switch is off, and is configured to receive a plurality of signals from the plurality of switches of the release permission switch and determine an abnormality of the release permission switch based on the relationship of the plurality of signals. [Effects of the Invention]

[0007] According to the above embodiment, in a work machine having a work tool capable of holding and releasing an object, it is possible to determine an abnormality in the release permission switch that permits the release operation of the work tool. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of a forklift according to an embodiment of the present invention. [Figure 2] This is a perspective view from above of a clamping device according to an embodiment of the present invention. [Figure 3] This is a block diagram showing the electrical configuration of a forklift according to an embodiment of the present invention. [Figure 4]This is a schematic diagram of the release permission switch according to an embodiment of the present invention. [Figure 5] This is an explanatory diagram of a method for determining abnormalities in a release permission switch according to an embodiment of the present invention. [Figure 6] This flowchart shows a control method according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. In all drawings used to illustrate the embodiments, the same reference numerals are generally used for the same components, and repeated descriptions of them will be omitted.

[0010] [Overall configuration of a forklift] First, the configuration of the forklift according to this embodiment will be described with reference to Figures 1 and 2. In this embodiment, a forklift is used as an example of the work machine. Figure 1 is a side view of the forklift according to this embodiment, and Figure 2 is a perspective view of the clamping device according to this embodiment.

[0011] As shown in Figure 1, the forklift 1 mainly consists of a main body 2, which includes a driver's seat 2C where an operator is seated and a vehicle 2R, and a work implement 3 located at the front of the main body 2. The work implement 3 has a clamping device 10 as a work tool (attachment) that can switch between a holding operation for holding (clamping / gripping) an object and a release operation for releasing the held object. The work implement 3 also has a mast 5 that extends vertically and a mast lift cylinder 6 that can be driven to raise and lower the clamping device 10 along the mast 5.

[0012] As shown in Figure 1, the forklift 1's main body 2 is equipped with a battery 7 as a power source, a drive motor 8 for driving the vehicle 2R using the power of the battery 7, a work motor 9 for operating the clamping device 10 using the power of the battery 7, an accelerator pedal 19 for receiving input to drive the vehicle 2R, a lift lever 20 for receiving input to raise and lower the clamping device 10, an operation lever 21 for receiving input to hold or release the clamping device 10, and a controller 30 for performing various controls on the forklift 1. The controller 30 controls the drive motor 8 based on the operation of the accelerator pedal 19 to drive the drive wheels 4 of the vehicle 2R. The controller 30 also controls the work motor 9 based on the operation of the lift lever 20 and the operation lever 21 to raise and lower the clamping device 10, or to hold or release the clamping device 10. Furthermore, the forklift 1 is not limited to being driven by batteries 7 and motors 8 and 9, but may also be driven by power generated from various power sources such as internal combustion engines and fuel cells.

[0013] Next, as shown in Figure 2, the clamping device 10 includes a clamping base 11 extending in the left-right direction, a pair of left and right clampers 12L and 12R disposed on the clamping base 11, and clamping cylinders 13L and 13R configured to drive the clampers 12L and 12R, respectively. More specifically, the clamping base 11 has a guide rail 11G extending in the left-right direction, and the clampers 12L and 12R each have a guide arm 12G slidably supported by the guide rail 11G and a clamping arm 12A disposed at one end of the guide arm 12G and extending in the front-rear direction. In the clampers 12L and 12R, the guide arm 12G is moved horizontally in the left-right direction by the clamping cylinders 13L and 13R, respectively, so that the opposing clamping arms 12A and 12A open and close in the left-right direction. As a result, the clamping device 10 is able to hold and release objects.

[0014] The mast lift cylinder 6 and clamp cylinders 13L and 13R are driven using hydraulic power. On the other hand, the traveling body 2R of the main unit 2 is configured to be driven and controlled independently of these mast lift cylinders 6 and clamp cylinders 13L and 13R.

[0015] [Electrical configuration of a forklift] Next, with reference to Figure 3, the electrical configuration of the forklift 1 according to this embodiment will be described. As shown in Figure 3, the forklift 1 includes an accelerator pedal 19 for driving the vehicle 2R, a lift lever 20 for raising and lowering the clamping device 10, an operating lever 21 for holding or releasing the clamping device 10, a release permission switch 23 for allowing or prohibiting the release of the clamping device 10, a seat pressure sensor 25 configured to detect the operator's seat 2C, a seat belt sensor 26 configured to detect the operator wearing a seat belt, a display device 27 including a touch panel 28 that displays various screens and can be operated by the operator, a controller 30 configured to perform various controls on the forklift 1, and a drive system 40 configured to drive the vehicle 2R and work tools (attachments) such as the clamping device 10 based on the control of the controller 30.

[0016] The release permission switch 23 is configured to be switchable between on and off by the operator. The operator switches the release permission switch 23 from off to on when they want the clamping device 10 to perform a release operation, thereby permitting the release operation of the clamping device 10. Conversely, when the release permission switch 23 is set to off (for example, when operated by the operator to switch it from on to off), the release operation of the clamping device 10 is prohibited. In one example, the release permission switch 23 is configured as a button or the like that is on when pressed and off when released, and is provided at the tip of the operating lever 21.

[0017] Note that, in addition to the lift lever 20 and the operation lever 21, the forklift 1 also includes a tilt lever or the like for tilting the mast 5 in the front-rear direction. Further, the forklift 1 may have two or more operation levers 21. The operation lever 21 corresponds to an example of the "operation device" in the present invention, and the display device 27 corresponds to an example of the "notification device" in the present invention.

[0018] Here, with reference to Fig. 4, a specific configuration of the release permission switch 23 according to the present embodiment will be described. Fig. 4 is a schematic diagram showing an electrical configuration of the release permission switch 23 according to the present embodiment.

[0019] As shown in Fig. 4, the release permission switch 23 is configured as a so-called c-contact type switch including an a-contact and a b-contact, and includes a common terminal 23c, a normally closed terminal 23nc, a normally open terminal 23no, and a switch unit 23sw. Specifically, in the release permission switch 23, the connection between the common terminal 23c and the normally closed terminal 23nc via the switch unit 23sw forms a b-contact (see reference sign x1), and the connection between the common terminal 23c and the normally open terminal 23no via the switch unit 23sw forms an a-contact (see reference sign x2).

[0020] In the release permission switch 23, the circuit in which connection / disconnection between the common terminal 23c and the normally closed terminal 23nc is switched by the switch unit 23sw constitutes a first switch sw1, and this first switch sw1 corresponds to the "normally closed type switch" in the present invention. Further, the circuit in which connection / disconnection between the common terminal 23c and the normally open terminal 23no is switched by the switch unit 23sw constitutes a second switch sw2, and this second switch sw2 corresponds to the "normally open type switch" in the present invention. As described above, the release permission switch 23 is configured by two switches (the first and second switches sw1, sw2). Furthermore, the release permission switch 23 is not limited to being composed of two switches; it may also be composed of three or more switches. In that case, the release permission switch 23 can be composed of a combination of normally closed switches and normally open switches as appropriate.

[0021] Furthermore, the release enable switch 23 ensures that a first input signal s1 is supplied to the controller 30 from the normally closed terminal 23nc of the first switch sw1, and a second input signal s2 is supplied to the controller 30 from the normally open terminal 23no of the second switch sw2. These first and second input signals s1 and s2 correspond to the current or voltage values ​​input to the controller 30, and indicate the state of the first and second switches sw1 and sw2, respectively, i.e., the closed state (connected state) or the open state (disconnected state / unconnected state). Basically, the current or voltage values ​​corresponding to the first and second input signals s1 and s2 are higher when the first and second switches sw1 and sw2 are in the closed state than when the first and second switches sw1 and sw2 are in the open state. In a typical example, when the first and second switches sw1 and sw2 are in the open state, the current or voltage values ​​are approximately 0.

[0022] Furthermore, as described above, the release permission switch 23 is turned off when the switch is not operated by an operator (for example, when the button is in the released state). When the release permission switch 23 is off, the common terminal 23c and the normally closed terminal 23nc are connected via the switch unit 23sw. In this case, the first input signal s1 indicates that the first switch sw1 is in the closed state, and the second input signal s2 indicates that the second switch sw2 is in the open state. On the other hand, the release permission switch 23 is turned on when the switch is operated by an operator (for example, when the button is pressed). When the release permission switch 23 is on, the common terminal 23c and the normally open terminal 23no are connected via the switch unit 23sw. In this case, the first input signal s1 indicates that the first switch sw1 is in the open state, and the second input signal s2 indicates that the second switch sw2 is in the closed state.

[0023] Returning to Figure 3, the controller 30 and drive system 40 of the forklift 1 will be described in detail. The controller 30 is a computer comprising one or more processors 31 (typically CPUs) and memory 35 such as ROM or RAM for storing various programs (including basic control programs such as the OS and application programs launched on the OS to realize specific functions) and various data that are interpreted and executed on the processor 31. Specifically, the processor 31 of the controller 30 has a solenoid control unit 32 for controlling the drive system 40 (particularly the open-side solenoid valve 41 and the closed-side solenoid valve 42 in the drive system 40) to hold or release the clamp device 10 in response to the operation of the operating lever 21, and a release control unit 33 for controlling the solenoid control unit 32 to allow or prohibit the release operation of the clamp device 10 in response to the on / off state of the release permission switch 23 (i.e., in response to the first and second input signals s1 and s2 input from the release permission switch 23).

[0024] The drive system 40 mainly comprises a drive motor 8 powered by the battery 7, a drive drive unit 46 that drives the vehicle 2R using the power of the drive motor 8, a motor 9 for the work equipment powered by the battery 7, and a hydraulic drive unit 44 that drives the clamping device 10 using the power of the motor 9. The controller 30 controls the drive motor 8 based on the operation of the accelerator pedal 19, thereby driving the drive wheels 4 of the vehicle 2R via the drive drive unit 46. This accelerates or decelerates the vehicle 2R. The controller 30 also controls the motor 9 based on the operation of the lift lever 20 and the operating lever 21, thereby raising and lowering the clamping device 10, or performing a holding or releasing operation of the clamping device 10 via the hydraulic drive unit 44. In this case, the controller 30 drives the mast lift cylinder 6 and clamp cylinders 13L and 13R of the clamping device 10 via the hydraulic drive unit 44 (Figures 1 and 2). Furthermore, in the drive system 40, the hydraulic drive unit 44 and the traction drive unit 46 are configured independently and are mainly composed of hydraulic pumps and the like. In this example, the hydraulic drive unit 44 and the travel drive unit 46 are configured independently, meaning that the travel body 2R and the work implement 3 use independent drive units. However, in other examples, a common drive unit may be used for both the travel body 2R and the work implement 3. In this case as well, the drive control can be performed independently for both the travel body 2R and the work implement 3. Furthermore, in yet another example, instead of configuring such a drive unit with a hydraulic system, the drive unit may be configured with any system such as an electric motor.

[0025] In this embodiment in particular, the drive system 40 includes an open-side solenoid valve 41 for releasing the clamping device 10 (i.e., opening the clamping arms 12A of the clampers 12L and 12R) and a closed-side solenoid valve 42 for holding the clamping device 10 (i.e., closing the clamping arms 12A). The hydraulic drive unit 44 drives the clamping device 10 using hydraulic pressure according to the state of these open-side solenoid valves 41 and closed-side solenoid valves 42. The opening degree of the open-side solenoid valves 41 and 42 is controlled according to the current supplied from the solenoid control unit 32 of the controller 30. The hydraulic drive unit 44 includes various pumps, valves, and oil passages, and supplies hydraulic fluid to the clamping cylinders 13L and 13R of the clamping device 10 and recovers hydraulic fluid from the clamping cylinders 13L and 13R.

[0026] In this embodiment, the release control unit 33 of the controller 30 determines whether the release permission switch 23 is on or off based on the first and second input signals s1 and s2 from the release permission switch 23, and in particular based on the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2. Specifically, the release control unit 33 determines that the release permission switch 23 is off if the first input signal s1 indicates that the first switch sw1 is in a closed state, and the second input signal s2 indicates that the second switch sw2 is in an open state. In this case, the release control unit 33 controls the solenoid control unit 32 to prevent the clamp device 10 from performing a release operation, regardless of the operation of the operating lever 21, in order to prohibit the release operation of the clamp device 10. As a result of this control, current is no longer supplied from the solenoid control unit 32 to the open-side solenoid valve 41 of the drive system 40, and the open-side solenoid valve 41 does not open, so the release operation of the clamp device 10 is prevented.

[0027] On the other hand, the release control unit 33 determines that the release permission switch 23 is ON if the first input signal s1 indicates that the first switch sw1 is open and the second input signal s2 indicates that the second switch sw2 is closed. In this case, the release control unit 33 permits the release operation of the clamp device 10 and controls the solenoid control unit 32 to cause the clamp device 10 to perform a release operation in response to the operation of the operating lever 21. As a result of this control, current is supplied from the solenoid control unit 32 to the open-side solenoid valve 41 of the drive system 40, and the open-side solenoid valve 41 opens, causing the clamp device 10 to perform a release operation.

[0028] Furthermore, in addition to the components described above, the forklift 1 has an abnormality detection sensor capable of detecting abnormalities such as wire breaks, ground faults, ceiling faults, and contact welding within the forklift 1, more specifically in the clamping device 10, etc. The controller 30 has a GND cut control unit configured to prohibit the supply of control signals from the solenoid control unit 32 to the open-side solenoid valve 41 and the closed-side solenoid valve 42 when the abnormality detection sensor detects an abnormality. In addition, a GND relay may be provided to stop the supply of current from the solenoid control unit 32 to the open-side solenoid valve 41 when the supply of control signals to the open-side solenoid valve 41 is prohibited by the GND cut control unit.

[0029] [Abnormal detection of the release permission switch] Next, in this embodiment, the abnormality detection of the release permission switch 23 by the controller 30 will be described. First, the reason for performing the abnormality detection of the release permission switch 23 will be explained.

[0030] In a forklift 1 equipped with a clamping device 10 capable of holding and releasing objects, if the clamping device 10 accidentally performs a release operation while holding an object, the object will be dropped. Therefore, conventionally, forklifts 1 are equipped with a release permission switch 23 to allow or prohibit the release operation of the clamping device 10. This prevents the clamping device 10 from accidentally releasing by allowing the release operation of the clamping device 10 only when the release permission switch 23 is on, and prohibiting the release operation of the clamping device 10 when the release permission switch 23 is off.

[0031] However, if a malfunction occurs in the release permission switch 23, it may not be possible to prevent unintended release operations. In particular, if a malfunction occurs that causes the release permission switch 23 to be mistakenly judged as always being in the ON state, the clamp device 10 will perform a release operation even without the operator performing the operation to switch the release permission switch 23 to ON. Furthermore, in this case, since the clamp device 10 will perform the release operation by operating the operating lever 21, it is difficult for the operator to notice the malfunction of the release permission switch 23. For these reasons, in this embodiment, a malfunction of the release permission switch 23 is detected.

[0032] Now, with reference to Figure 5, the method for determining abnormalities in the release permission switch 23 according to this embodiment will be described. Figure 5 shows the relationship between the states (closed state or open state) of the first and second switches sw1 and sw2, respectively, indicated by the first and second input signals s1 and s2 supplied from the release permission switch 23 to the release control unit 33 of the controller 30, and the abnormality determination result of the release permission switch 23 based on these states.

[0033] As shown in Figure 5, in this embodiment, the release control unit 33 of the controller 30 determines that the release enable switch 23 is abnormal when the states of the first and second switches sw1 and sw2, indicated by the first and second input signals s1 and s2, are the same. Specifically, the release control unit 33 determines that the release enable switch 23 is abnormal when the first and second input signals s1 and s2 indicate that both the first and second switches sw1 and sw2 are open, or that both the first and second switches sw1 and sw2 are closed.

[0034] In the release-to-open switch 23, the common terminal 23c is selectively connected by the switch unit 23sw to either the normally closed terminal 23nc or the normally open terminal 23no (Figure 4). Therefore, in principle, one of the first and second switches sw1 and sw2 will be in a closed state, and the other in an open state. Consequently, if the release-to-open switch 23 is functioning correctly, the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 will not be the same, except during switch switching. In other words, if the states indicated by the first and second input signals s1 and s2 are the same, it indicates that the release-to-open switch 23 is malfunctioning. For example, in this case, it can be determined that a short circuit, ground fault, or open circuit has occurred inside the release-to-open switch 23 or in the wiring from the release-to-open switch 23 to the release-to-open control unit 33 of the controller 30. Therefore, the release-to-open control unit 33 determines that the release-to-open switch 23 is malfunctioning if the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 are the same. Even if the release-to-enable switch 23 is functioning correctly, chattering or momentarily passing through an intermediate position during switch switching can cause the states of the first and second switches sw1 and sw2, indicated by the first and second input signals s1 and s2, to become the same. In such cases, i.e., during transitions, the state may be determined separately.

[0035] On the other hand, the release control unit 33 determines that the release enable switch 23 is normal if the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 are different. Specifically, the release control unit 33 determines that the release enable switch 23 is normal if the first input signal s1 indicates that the first switch sw1 is closed and the second input signal s2 indicates that the second switch sw2 is open. In this case, the release enable switch 23 is in the off state. Also, the release control unit 33 determines that the release enable switch 23 is normal if the first input signal s1 indicates that the first switch sw1 is open and the second input signal s2 indicates that the second switch sw2 is closed. In this case, the release enable switch 23 is in the on state.

[0036] Next, with reference to Figure 6, the overall flow of the control performed in this embodiment will be described. Figure 6 is a flowchart of the control method according to this embodiment. This flow is repeatedly executed by the controller 30 at a predetermined period. Specifically, the processor 31 in the controller 30 reads a program stored in the memory 35 and executes the program, thereby realizing the control and processing related to this flow.

[0037] First, in step S11, the controller 30 acquires signals from the operating lever 21, the release permission switch 23, the seat pressure sensor 25, the seat belt sensor 26, the touch panel 28 of the display device 27, etc. In this case, the controller 30 acquires the first and second input signals s1 and s2 from the release permission switch 23.

[0038] Next, in step S12, the controller 30 (release control unit 33) performs an abnormality determination of the release permission switch 23 based on the relationship between the first and second input signals s1 and s2 from the release permission switch 23. Specifically, the controller 30 compares the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2. If the controller 30 determines that the release permission switch 23 is abnormal (step S13: Yes), it proceeds to step S14. The controller 30 determines that the release permission switch 23 is abnormal if the states (closed state or open state) of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 are the same (Figure 5).

[0039] In step S14, the controller 30 controls the display device 27 to notify that the release permission switch 23 is malfunctioning. In this case, the controller 30 causes the display device 27 to display a screen indicating that the release permission switch 23 is malfunctioning. After step S14, the controller 30 exits the flow shown in Figure 6. In addition to displaying that the release permission switch 23 is malfunctioning, the controller 30 may also notify that the release permission switch 23 is malfunctioning by voice instead of displaying it.

[0040] On the other hand, if the controller 30 does not determine that the release enable switch 23 is abnormal (step S13: No), that is, if it determines that the release enable switch 23 is normal, it proceeds to step S15. The controller 30 determines that the release enable switch 23 is normal if the states (closed state or open state) of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 are different (Figure 5).

[0041] In step S15, the controller 30 determines whether the forklift 1 is in a predetermined state. Specifically, the controller 30 determines that the predetermined state is either when the controller 30 is started (in other words, when the engine of the forklift 1 is started (when the key switch is turned on)) or when the operator has left the driver's seat 2C and returned. For example, the controller 30 determines whether the operator has left the driver's seat 2C and returned based on the detection signals of the seat pressure sensor 25 and / or the seat belt sensor 26. If, as a result of step S15, the controller 30 determines that the forklift 1 is in a predetermined state (step S15: Yes), that is, when the controller 30 is started or when the operator has left the driver's seat 2C and returned, the process proceeds to step S16.

[0042] In step S16, the controller 30 determines whether the release-to-open switch 23 is ON or OFF based on the first and second input signals s1 and s2 from the release-to-open switch 23. If the controller 30 determines that the release-to-open switch 23 is ON as a result of step S16 (step S16: Yes), it proceeds to step S17. The controller 30 determines that the release-to-open switch 23 is ON if the first input signal s1 indicates that the first switch sw1 is in an open state, and the second input signal s2 indicates that the second switch sw2 is in a closed state.

[0043] On the other hand, if the controller 30 does not determine that the forklift 1 is in the predetermined situation described above (step S15: No), it exits the flow shown in Figure 6. Also, if the controller 30 does not determine that the release permission switch 23 is on (step S16: No), that is, if the release permission switch 23 is off, it exits the flow shown in Figure 6. The controller 30 determines that the release permission switch 23 is off when the first input signal s1 indicates that the first switch sw1 is in a closed state, and the second input signal s2 indicates that the second switch sw2 is in an open state.

[0044] Next, in step S17, the controller 30 prohibits the release operation of the clamping device 10. Specifically, the release control unit 33 of the controller 30 controls the solenoid control unit 32 of the controller 30 to prevent the clamping device 10 from performing a release operation, regardless of the operation of the operating lever 21, in order to prohibit the release operation of the clamping device 10. Then, the controller 30 proceeds to step S18 and determines whether the release permission switch 23 has been turned off based on the first and second input signals s1 and s2 from the release permission switch 23. If, as a result of step S18, the controller 30 determines that the release permission switch 23 has been turned off (step S18: Yes), it exits the flow shown in Figure 6. On the other hand, if the controller 30 does not determine that the release permission switch 23 has been turned off (step S18: No), that is, if the release permission switch 23 remains on, it returns to step S17. The controller 30 repeats steps S17 and S18 until the release permission switch 23 is turned off. In this way, the controller 30 continues to prohibit the release operation of the clamping device 10 until the release permission switch 23 switches from on to off.

[0045] The reason for prohibiting the release operation of the clamping device 10 is as follows: When the controller 30 is started up, or when the operator leaves the driver's seat 2C and returns, if the release permission switch 23 is on, it is thought that some kind of mechanical welding (such as being stuck or being kept pressed down by tape) has occurred in the release permission switch 23. In this case, the clamping device 10 will release even if the release permission switch 23 is not switched on. Therefore, in this embodiment, when the controller 30 is started up, or when the operator leaves the driver's seat 2C and returns, if the release permission switch 23 is on, the release operation of the clamping device 10 is prohibited until the release permission switch 23 is switched from on to off.

[0046] [Mechanism of Action and Effects] Next, the operation and effects of the forklift 1 according to this embodiment will be described. In this embodiment, the forklift 1 has a main body 2 and a work machine 3 which includes a clamping device 10 disposed on the main body 2 and capable of performing a holding operation for holding an object and a releasing operation for releasing the held object. The forklift 1 includes an operating lever 21 which is operated by an operator to operate the clamping device 10, a drive system 40 configured to drive the clamping device 10, a release permission switch 23 which can be switched on and off to allow or prohibit the release operation of the clamping device 10, and a controller 30 configured to control the drive system 40 to operate the clamping device 10. When the release permission switch 23 is on, the clamping device 1 The system includes a controller 30 configured to control the drive system 40 to perform a release operation when the release permission switch 23 is off, while controlling the drive system 40 to prohibit the release operation of the clamp device 10 when the release permission switch 23 is off. The release permission switch 23 includes first and second switches sw1 and sw2, which are configured to switch states depending on whether the release permission switch 23 is on or off. The controller 30 receives first and second input signals s1 and s2 from the first and second switches sw1 and sw2 and is configured to determine an abnormality in the release permission switch 23 based on the relationship between the first and second input signals s1 and s2.

[0047] In this embodiment, the release permission switch 23 is configured with two first and second switches sw1 and sw2, whose respective states (open state / closed state) switch depending on whether the switch is on or off. First and second input signals s1 and s2 from these first and second switches sw1 and sw2 are supplied to the controller 30. As a result, the controller 30 can accurately determine if there is an abnormality in the release permission switch 23 based on the relationship between the first and second input signals s1 and s2 from the first and second switches sw1 and sw2. Therefore, it is possible to avoid malfunctions caused by an abnormality in the release permission switch 23.

[0048] Furthermore, in this embodiment, the release permission switch 23 includes a normally closed first switch sw1 and a normally open second switch sw2, and the controller 30 is configured to determine that the release permission switch 23 is abnormal when the first and second input signals s1 and s2 indicate that the first and second switches sw1 and sw2 are in the same state.

[0049] In a release-to-open switch 23, which consists of a normally closed first switch sw1 and a normally open second switch sw2, in principle, one of the first and second switches sw1 and sw2 will be in a closed state (connected state), and the other will be in an open state (disconnected state / unconnected state). Therefore, if the release-to-open switch 23 is functioning correctly, the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2 will never be the same. In other words, if the states indicated by the first and second input signals s1 and s2 are the same, it indicates that the release-to-open switch 23 is malfunctioning. Thus, by making a determination based on the states of the first and second switches sw1 and sw2 indicated by the first and second input signals s1 and s2, it is possible to accurately determine if the release-to-open switch 23 is malfunctioning.

[0050] Furthermore, in this embodiment, the forklift 1 also has a display device 27 configured to notify the operator by display, and the controller 30 is configured to control the display device 27 to notify the operator that the release permission switch 23 is abnormal when it determines that the release permission switch 23 is abnormal. This ensures that the operator is reliably aware that the release permission switch 23 is abnormal.

[0051] Furthermore, in this embodiment, the controller 30 is configured to prohibit the release operation of the clamping device 10 until the release permission switch 23 is switched from on to off when the release permission switch 23 is on when the forklift 1 is in a predetermined state, specifically when the controller 30 is started or when the operator leaves the driver's seat 2C and returns. When the controller 30 is started or when the operator leaves the driver's seat 2C and returns, if the release permission switch 23 is on, it is thought that some kind of mechanical welding has occurred in the release permission switch 23. In this case, the clamping device 10 will release even if the release permission switch 23 is not switched on. Therefore, in this embodiment, it is possible to avoid such problems by prohibiting the release operation of the clamping device 10 until the release permission switch 23 is switched from on to off.

[0052] Furthermore, in this embodiment, the controller 30 is configured to determine whether the release permission switch 23 is on or off based on the relationship between the first and second input signals s1 and s2. By using the first and second input signals s1 and s2 from the first and second switches sw1 and sw2 of the release permission switch 23 configured as described above, it is possible to accurately determine whether the release permission switch 23 is on or off.

[0053] Furthermore, in this embodiment, the main body 2 includes a traveling body 2R, and the traveling body 2R is configured to be driven and controlled independently of the work machine 3, which includes the clamping device 10. In a forklift 1 including such a traveling body 2R, if the clamping device 10 mistakenly performs a release operation, an object will fall off while the forklift is in motion. However, according to this embodiment, since the abnormality of the release permission switch 23 is accurately detected as described above, such a problem can be reliably avoided.

[0054] [Differentiation] Next, a modified example of the above-described embodiment will be explained.

[0055] In the embodiment described above, the controller 30 notified the display device 27 when it determined that the release permission switch 23 was abnormal. However, in the modified example, the controller 30 may, in addition to notifying in this way, or instead prohibit the release operation of the clamp device 10. This makes it possible to reliably avoid malfunctions caused by an abnormality in the release permission switch 23.

[0056] Furthermore, although the above-described embodiment applied the present invention to a forklift 1 having a clamping device 10, the present invention is applicable to various work machines having work tools (attachments) capable of holding and releasing objects. For example, the present invention is applicable to hydraulic excavators, log loaders, wheel loaders, and the like.

[0057] Furthermore, while the present invention was applied to a work machine (forklift 1) in the above-described embodiment, in a modified example, the present invention may also be applied to a control system for a work machine configured to allow an operator to operate the work machine from the outside, where the operating device (remote control) of the work machine is located externally, or to a control system for a work machine configured to allow operation of the work machine by operation commands from an external controller such as a control system.

[0058] As described above, the embodiments and modifications described are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments and modifications. The present invention can be implemented in various forms without departing from its spirit.

[0059] (Note 1) The main unit and A work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a releasing operation for releasing the held object, A drive system for operating the aforementioned work tool, An operating device that receives commands to operate the aforementioned work tool, A release permission switch, which includes multiple switches, is switched on and off to allow or prohibit the release operation of the work tool, and the state of each of the multiple switches switches in accordance with the on or off switching, A controller configured to control the drive system to cause the work tool to perform the release operation in response to the operation of the operating device when the release permission switch is ON, while controlling the drive system to prohibit the release operation of the work tool when the release permission switch is OFF, and to determine an abnormality of the release permission switch based on the relationship between the multiple signals from the multiple switches of the release permission switch, A machine used for working on cars. (Note 2) The plurality of switches include normally open type switches and normally closed type switches, where when one is closed, the other is open, and they have different output characteristics. The controller is configured to determine that the release enable switch is abnormal when the multiple signals from the multiple switches indicate that the multiple switches are in the same state. The work machines described in Appendix 1. (Note 3) The aforementioned work machine further includes a notification device configured to notify the worker by display and / or sound, The controller is configured to control the notification device to notify that the release permission switch is abnormal when it determines that the release permission switch is abnormal. The work machines described in Appendix 1 or 2. (Note 4) The work machine according to any one of the appendices 1 to 3, wherein the controller is configured to prohibit the release operation of the work tool when it determines that the release permission switch is abnormal. (Note 5) The work machine according to any one of the appendices 1 to 4, wherein the controller is configured to prohibit the release operation of the work tool when the release permission switch is on while the work machine is in a predetermined state, until the release permission switch is switched from on to off. (Note 6) The work machine according to any one of the appendices 1 to 5, wherein the controller is configured to determine whether the release permission switch is on or off based on the relationship between the plurality of signals. (Note 7) The work machine described in any one of the appendices 1 to 6, wherein the work machine comprises a work machine disposed on the main body and including the work tool, the main body includes a traveling body, and the traveling body is configured to be driven and controlled independently of the work tool. (Note 8) The work machine is a forklift, and the work tool is a clamping device for the forklift, as described in any one of Appendix 1 to 7. (Note 9) The main unit and A work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a releasing operation for releasing the held object, A drive system for operating the aforementioned work tool, An operating device that receives commands to operate the aforementioned work tool, A release permission switch, which includes multiple switches, is switched on and off to allow or prohibit the release operation of the work tool, and the state of each of the multiple switches switches in accordance with the on or off switching, A controller configured to control the drive system to cause the work tool to perform the release operation in response to the operation of the operating device when the release permission switch is ON, while controlling the drive system to prohibit the release operation of the work tool when the release permission switch is OFF, and to determine an abnormality of the release permission switch based on the relationship between the multiple signals from the multiple switches of the release permission switch, A control system for a work machine equipped with [a specific feature / equipment]. (Note 10) A work machine comprising a main body, a work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a release operation for releasing the held object, a drive system for operating the work tool, an operating device for receiving operations for operating the work tool, and a release permission switch that includes a plurality of switches, which is switched on and off to permit or prohibit the release operation of the work tool, and the state of each of the plurality of switches is switched according to the on or off switching, wherein a control method for the work machine is performed by a controller for operating the work machine, When the release permission switch is ON, the drive system is controlled to cause the work tool to perform the release operation in response to the operation of the operating device, while when the release permission switch is OFF, the drive system is controlled to prohibit the release operation of the work tool. Multiple signals from the multiple switches are input to the release enable switch, and an abnormality of the release enable switch is determined based on the relationship between the multiple signals. A method for controlling a work machine equipped with a control device. [Explanation of symbols]

[0060] 1...Forklift, 2...Main body, 2R...Travel body, 3...Work equipment, 5...Mast, 10...Clamping device, 21...Operating lever, 23...Release permission switch, 23c...Common terminal, 23nc...Normally closed terminal, 23no...Normally open terminal, 23sw...Switch unit, 27...Display device, 30...Controller, 31...Processor, 32...Solenoid control unit, 33...Release control unit, 40...Drive system, 41...Open solenoid valve, 42...Closed solenoid valve, 44...Hydraulic drive device, s1...First input signal, s2...Second input signal, sw1...First switch, sw2...Second switch

Claims

1. The main unit and A work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a releasing operation for releasing the held object, A drive system for operating the aforementioned work tool, An operating device that receives commands to operate the aforementioned work tool, A release permission switch, which includes multiple switches, is switched on and off to allow or prohibit the release operation of the work tool, and the state of each of the multiple switches switches in accordance with the on or off switching, A controller configured to control the drive system to cause the work tool to perform the release operation in response to the operation of the operating device when the release permission switch is ON, while controlling the drive system to prohibit the release operation of the work tool when the release permission switch is OFF, and to determine an abnormality of the release permission switch based on the relationship between the multiple signals from the multiple switches of the release permission switch, A machine used for working on cars.

2. The plurality of switches include normally open type switches and normally closed type switches, where when one is closed, the other is open, and they have different output characteristics. The controller is configured to determine that the release enable switch is abnormal when the multiple signals from the multiple switches indicate that the multiple switches are in the same state. The work machine according to claim 1.

3. The aforementioned work machine further includes a notification device configured to notify the worker by display and / or sound, The controller is configured to control the notification device to notify that the release permission switch is abnormal when it determines that the release permission switch is abnormal. The working machine according to claim 1 or 2.

4. The work machine according to claim 1 or 2, wherein the controller is configured to prohibit the release operation of the work tool when it determines that the release permission switch is abnormal.

5. The work machine according to claim 1 or 2, wherein the controller is configured to prohibit the release operation of the work tool when the release permission switch is on while the work machine is in a predetermined state, until the release permission switch is switched from on to off.

6. The work machine according to claim 1 or 2, wherein the controller is configured to determine whether the release permission switch is on or off based on the relationship between the plurality of signals.

7. The work machine according to claim 1 or 2, wherein the work machine comprises a work machine disposed on the main body and including the work tool, the main body includes a traveling body, and the traveling body is configured to be driven and controlled independently of the work tool.

8. The work machine according to claim 1 or 2, wherein the work machine is a forklift, and the work tool is a clamping device for the forklift.

9. The main unit and A work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a releasing operation for releasing the held object, A drive system for operating the aforementioned work tool, An operating device that receives commands to operate the aforementioned work tool, A release permission switch, which includes multiple switches, is switched on and off to allow or prohibit the release operation of the work tool, and the state of each of the multiple switches switches in accordance with the on or off switching, A controller configured to control the drive system to cause the work tool to perform the release operation in response to the operation of the operating device when the release permission switch is ON, while controlling the drive system to prohibit the release operation of the work tool when the release permission switch is OFF, and to determine an abnormality of the release permission switch based on the relationship between the multiple signals from the multiple switches of the release permission switch, A control system for a work machine equipped with [a specific feature / equipment].

10. A work machine comprising a main body, a work tool that is operable with respect to the main body and capable of performing a holding operation for holding an object and a release operation for releasing the held object, a drive system for operating the work tool, an operating device for receiving operations for operating the work tool, and a release permission switch that includes a plurality of switches, which is switched on and off to permit or prohibit the release operation of the work tool, and the state of each of the plurality of switches is switched according to the on or off switching, wherein a control method for the work machine is performed by a controller for operating the work machine, When the release permission switch is ON, the drive system is controlled to cause the work tool to perform the release operation in response to the operation of the operating device, while when the release permission switch is OFF, the drive system is controlled to prohibit the release operation of the work tool. Multiple signals from the multiple switches are input to the release enable switch, and an abnormality of the release enable switch is determined based on the relationship between the multiple signals. A method for controlling a work machine equipped with a control device.

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