WORKING VEHICLE

Abstract

 A working vehicle (1) includes a control valve unit (10) with a service actuator control valve (13a), a first drive unit (15), a travel unit (6), a lower body (2), an upper body (3), a cab (4), a plurality of work units (7, 14) and a plurality of hydraulic traveling motors (17a, 17b), an operation unit (5), a quick hitch (55), an attachment (51d), a trigger-switch (30), a plurality of solenoid valves (71a, 71b) and a plurality of pipelines (73, 74), and a controller (9). The controller (9) performs control that, in a case where the controller (9) receives the trigger signal from the trigger-switch (30) to release the lock of the quick hitch (55), the pressure oil in the plurality of pipelines (73, 74) is returned to the hydraulic oil tank (54) by energizing the plurality of solenoid valves (71a, 71b) with the first drive unit (15) stopped.

Description

Technical Field

[0001] The present invention relates to a working vehicle.

Background Art

[0002] Conventionally, a working vehicle having a configuration in which a quick hitch attached to an arm locks an attachment is known (PTL 1: JP2017-187144A).

Summary of Invention

Technical Problem

[0003] According to the conventional configuration, a dedicated service pipe and a dedicated solenoid valve are used to return pressure oil in a pipeline for a service actuator. The conventional configuration thus presents a problem that the cost of components is high and the piping layout is complicated.

Solution to Problem

[0004] The present invention is made in view of the above-described circumstances. Therefore, an object of the present invention is to provide a working vehicle that has a simple configuration with no dedicated service pipe and no dedicated solenoid valve and is also capable of automatically returning pressure oil in a pipeline for a service actuator when operation for releasing its lock of a quick hitch is performed.

[0005] The present invention has been accomplished under the solutions as disclosed below.

[0006] The present invention relates to a working vehicle. The working vehicle comprises a control valve unit with a service actuator control valve, a first drive unit supplying hydraulic oil to a primary side of the control valve unit, a travel unit, a lower body provided with the travel unit, an upper body slewably disposed on the lower body, a second drive unit causing the upper body to slew, a cab disposed in the upper body, a plurality of work units and a plurality of hydraulic traveling motors driven by pressure oil from secondary side of the control valve unit, an operation unit operated by an operator, a quick hitch that is driven by the pressure oil to lock in a state of being attached to an arm of the working unit, an attachment that comes to connect to the arm in response to the locking, a trigger-switch for sending a trigger signal according to operation by the operator, a plurality of solenoid valves of the service actuator control valve, a plurality of pipelines connected to the service actuator control valve, a hydraulic oil tank, and a controller. The controller performs control that, in a case where the controller receives the trigger signal from the trigger-switch to release the lock of the quick hitch, the pressure oil in the plurality of pipelines is returned to the hydraulic oil tank by energizing the plurality of solenoid valves with the first drive unit stopped.

[0007] According to the configuration, with the first drive unit stopped, the controller uses a pressure in an accumulator and performs a series of control that a spool is reciprocated by the solenoid valve of the control valve for a service actuator to return the hydraulic oil fed to the pipeline for a service actuator to a hydraulic oil tank. This configuration eliminates the need for a dedicated service pipe and a dedicated solenoid valve, so that the cost of components can be reduced, the piping layout is simplified, and the pressure oil can be automatically returned.

[0008] As an example, the controller performs control that the pressure oil is returned by alternately energizing the plurality of solenoid valves provided on both sides of a spool of the service actuator control valve. This configuration enables returning the pressure oil in the pipeline for a service actuator more reliably.

[0009] As an example, the controller performs control that the first drive unit is operated and the lock of the quick hitch is released after a first term required for returning the pressure oil has elapsed. This configuration enables returning the pressure oil more reliably at the time of releasing the lock of the quick hitch.

[0010] As an example, the controller performs control that operation of a service actuator connected to the service actuator control valve is not received in a second term in which the trigger-switch operating. This configuration makes it possible to prevent the pressure oil from being fed to the pipeline for a service actuator during a period between returning the pressure oil in the pipeline for a service actuator and releasing the lock of the quick hitch, even when the operator performs incorrect operation. Thus, the working vehicle with higher safety can be achieved.

[0011] As an example, the working vehicle includes a travel unit, a lower body to which the travel unit is attached, an upper body provided on the lower body, and a cab provided on the upper body. As an example, the trigger-switch includes a first button and a second button that are provided in the cab, and the trigger-switch sends the trigger signal by pressing both the first button and the second button. This configuration makes it possible to prevent the lock of the quick hitch from being released due to a malfunction. Thus, the working vehicle with higher safety can be achieved.

Advantageous Effects of Invention

[0012] According to the present invention, it is possible to achieve the working vehicle that has a simple configuration with no dedicated service pipe and no dedicated solenoid valve and is also capable of automatically returning the pressure oil in the pipeline for a service actuator when operation for releasing the lock of the quick hitch is performed.

Brief Description of Drawings

[0013] 

Fig. 1 is a schematic perspective view showing an example of a working vehicle according to an embodiment.

Fig. 2 is a schematic circuit diagram showing an example of a drive control system in the working vehicle shown in Fig. 1.

Fig. 3 is a schematic flowchart showing an operation procedure for control on returning pressure oil in a pipeline for a service actuator in the working vehicle shown in Fig. 1.

Fig. 4 is a schematic timing chart showing control on returning pressure oil in a pipeline for a service actuator in the working vehicle shown in Fig. 1.

Fig. 5A is a schematic circuit diagram schematically showing a first state in which pressure oil is returned in a pipeline for a first service actuator in the working vehicle shown in Fig. 1 and a second state in which pressure oil is returned in the pipeline for the first service actuator in the working vehicle shown in Fig. 1. Fig. 5B is a schematic circuit diagram schematically showing a first state in which pressure oil is returned in a pipeline for a second service actuator in the working vehicle shown in Fig. 1 and a second state in which pressure oil is returned in the pipeline for the second service actuator in the working vehicle shown in Fig. 1.

Description of Embodiments

[0014] Hereinafter, an embodiment of the invention will be explained in detail with reference to the drawings. Fig. 1 is a schematic view showing an example of a working vehicle 1 according to the embodiment, and is a perspective view from the upper left rear. As an example of the working vehicle 1 of the embodiment, a hydraulic excavator is described herein. As a configuration other than the above, the working vehicle 1 may be a track loader or a tracked dumper. Incidentally, for the purpose of illustration, up and down, left and right, and front and rear directions may be represented by arrows in the diagrams. Further, in all of the diagrams for use in describing the embodiment, members having the same functions are assigned the respective same reference characters, and the repetitive description thereof may be omitted.

[0015] The working vehicle 1 includes an on-board charger that supplies electric power to a plurality of electric motors and so on and a display unit 98 that is configured to display information on operation of a drive unit, information on remaining battery capacity, and other known vehicle information. Incidentally, devices for use in travel motion and work in the working vehicle 1 are common to those in a known working vehicle, and the detailed description thereof is omitted.

[0016] As shown in Fig. 1, the working vehicle 1 includes a lower body 2 that is configured to travel and an upper body 3 that is provided on the lower body 2 and configured to slew. The lower body 2 includes a travel unit 6, and the travel unit 6 has a left and right pair of crawlers (tracks), as an example. The upper body 3 includes a cab 4, and the cab 4 has, in the front, operating units 5 for an operator riding on the vehicle to operate driving and work operations. A part enclosed by a broken line P2 in the drawing shows a schematic configuration of the operating units 5. The travel unit 6 includes a hydraulic motor 17a for travelling in a left travel body and a hydraulic motor 17b for travelling in a right travel body. As a configuration other than the above, the travel unit 6 may be a travel unit having tires.

[0017] The working vehicle 1 includes a slewing unit 8 driven by a second drive unit 16. As an example, the second drive unit 16 has an electric motor 16a to which a speed reducer 16c is assembled and has a configuration in which a pinion gear of the speed reducer 16c is engaged with a slewing bearing of the lower body 2 (not shown). As a configuration other than the above, a slewing unit provided with a hydraulic motor can be used.

[0018] The working vehicle 1 is provided with a plurality of working units including a working unit 7 and a working unit 14, and the plurality of working units is configured to be operated hydraulically (by hydraulic oil at a predetermined pressure). The working unit 14 includes a blade 51a, for example. The blade 51a is attached to the lower body 2 as to swing in the up-down direction and in the up-down direction including the front and rear components.

[0019] The working unit 7 includes, as an example, a boom 51b, an arm 51c, and an attachment 51d such as a bucket. The attachment 51d is, however, not limited to the bucket and a known attachment can be used. The boom 5 1b is attached to the upper body 3 as to swing in the up-down direction and in the up-down direction including the front and rear components. In the embodiment, a boom bracket is provided (not shown) between the upper body 3 and the boom 51b. The boom bracket enables the boom 51b to swing in the left-right direction and in the left-right direction including the front and rear components with respect to the upper body 3. Incidentally, the boom bracket is sometimes omitted. The arm 51c is attached to the boom 51b as to swing in the up-down direction and in the up-down direction including the front and rear components. The attachment 51d (bucket) is attached to the arm 51c as to swing in the up-down direction and in the up-down direction including the front and rear components. In the embodiment, the attachment 51d is caught and locked by a quick hitch 55 attached to the arm 51c. A part enclosed by a broken line P1 in the drawing shows a schematic configuration of the quick hitch 55.

[0020] As an example, the blade 51a is configured to swing, by a blade cylinder 18a, in the up-down direction with respect to the lower body 2. As an example, the arm 51c is configured to swing, by an arm cylinder 18b, in the up-down direction with respect to the boom 51b. As an example, the attachment 51d (bucket) is configured to swing, by a bucket cylinder 18c, in the up-down direction with respect to the arm 51c. As an example, the boom 51b is configured to swing, by a boom cylinder, in the up-down direction with respect to the upper body 3 (not shown). As an example, the boom 51b is configured to swing, by a swing cylinder, in the left-right direction with respect to the upper body 3 (not shown).

[0021] As an example, the quick hitch 55 includes a fixed claw 55a, a movable claw 55b, and a quick hitch cylinder 56 (quick hitch actuator) for pivoting the movable claw 55b. In order to lock the quick hitch 55, the operator operates the operating unit 5 to attach the fixed claw 55a to a first pin 57a provided in the attachment 51d (bucket), and then, to attach the movable claw 55b to a second pin 57b provided in the attachment 51d (bucket). Then, the quick hitch cylinder 56 is extended to lock the attachment 51d. In order to release the quick hitch 55, the operator operates the operating unit 5 to retract the quick hitch cylinder 56, and the attachment 51d is released. The quick hitch 55 is not limited as above construction.

[0022] The plurality of operating units 5 (operating levers) operated by the operator are provided in the cab 4. As an example, a trigger switch 30 includes a first button 31a (hand button) in the left operating unit 5 and a second button 31b (foot button) provided on the floor of the cab 4. In a case where the operator presses both the first button 31a and the second button 31b, a trigger signal is sent to a controller 9, and control is carried out to release the quick hitch 55. In addition to the configuration described above, as an example, the working vehicle 1 includes a plurality of switches such as a key switch and a push switch for both starting and stopping the working vehicle 1 (not shown).

[0023] As an example, a service actuator such as a breaker is connected to a port 19a for the first service actuator. As an example, a service actuator such as a swing actuator for rotating the quick hitch 55 around the longitudinal axis is connected to a port 19b for the second service actuator. The quick hitch cylinder 56 (quick hitch actuator) is connected to a port 19c for the third service actuator (port for the quick hitch actuator).

[0024] Fig. 2 is a schematic circuit diagram showing an example of a drive control system in the working vehicle 1. The working vehicle 1 includes a first drive unit 15 for supplying hydraulic oil at a predetermined pressure to the hydraulic motors 17a, 17b for travelling, the hydraulic cylinders 18a, 18b, 18c, and the ports 19a, 19b, 19c for the service actuators. The working vehicle 1 also includes the second drive unit 16 for operating the electric swing unit 8. The ports 19a, 19b, 19c for the service actuators are connection ports for hydraulically operating the individual attachments optionally attached. Incidentally, in the circuit diagram of Fig. 2, some notations except for the main parts are omitted.

[0025] The working vehicle 1 includes a battery pack 47. The battery pack 47 has a battery management system 48 and a lithium-ion rechargeable battery 49. The lithium-ion rechargeable battery 49 is formed by combining many cells, and power supply voltage of the lithium-ion rechargeable battery 49 is 70 to 600 [V], for example. The battery pack 47 is removable attached to the working vehicle 1. The battery pack 47 contains various sensors therein, and a wiring diagram thereof is omitted. As an example, the working vehicle 1 has a lead-acid battery 46 for supplying electric power to the battery management system 48 at the time of starting of the working vehicle 1.

[0026] The first drive unit 15 includes a first hydraulic pump 22a that draws in hydraulic oil stored in a hydraulic oil tank 54 to discharge the hydraulic oil, a first electric motor 21a for driving the first hydraulic pump 22a, and a first inverter 25a for supplying electric power to the first electric motor 21a according to a command from the controller 9. Further, the first drive unit 15 includes a second hydraulic pump 22b that draws in hydraulic oil stored in the hydraulic oil tank 54 to discharge the hydraulic oil, a second electric motor 21b for driving the second hydraulic pump 22b, and a second inverter 25b for supplying electric power to the second electric motor 21b according to the command. The first drive unit 15 is configured to combine a first output unit of the first hydraulic pump 22a with a second output unit of the second hydraulic pump 22b to feed the hydraulic oil to a primary side of a control valve unit 10.

[0027] The control valve unit 10 has a configuration in which primary sides of a plurality of control valves are connected in parallel. In the example of Fig. 2, primary sides of control valves 11a, 11b for the hydraulic motors, of control valves 12a, 12b, 12c for the hydraulic cylinders, and of control valves 13a, 13b, 13c for the service actuators are connected in parallel. The number of control valves constituting the control valve unit 10 sometimes increases or decreases. Further, the control valve unit 10 includes a relief valve 43, and a primary side of the relief valve 43 is connected in parallel to the primary side of each of the control valves. A secondary side of the relief valve 43 serves as a return passage for the secondary side, and hydraulic oil exceeding a set pressure is returned to the hydraulic oil tank 54.

[0028] The first drive unit 15 includes a first check valve 41a and a second check valve 41b. In the embodiment, a configuration is provided in which a primary side of the first check valve 41a is connected to the output side of the first hydraulic pump 22a, a primary side of the second check valve 41b is connected to the output side of the second hydraulic pump 22b, and a secondary side of the first check valve 41a is combined with a secondary side of the second check valve 41b to be connected to the primary side of the control valve unit 10. According to the embodiment, backflow of the pressure oil from the first hydraulic pump 22a to the second hydraulic pump 22b can be prevented, and backflow of the pressure oil from the second hydraulic pump 22b to the first hydraulic pump 22a can be also prevented.

[0029] The first hydraulic pump 22a and the second hydraulic pump 22b are both fixed displacement gear pumps. The first electric motor 21a and the second electric motor 21b are both synchronous motors and are both magnets-embedded motors (IPM motors). According to the above configuration, it is possible to quickly follow the increase in required flow quantity of the pressure oil. As an example, a rated output of the first hydraulic pump 22a is the same as a rated output of the second hydraulic pump 22b. As an example, maximum torque of the first electric motor 21a is the same as maximum torque of the second electric motor 21b.

[0030] The first drive unit 15 includes a rotation speed sensor 45a for detecting a rotation speed of the first electric motor 21a, and a rotation speed sensor 45b for detecting a rotation speed of the second electric motor 21b. The first drive unit 15 includes a temperature sensor 44 for detecting a temperature of the hydraulic oil in the hydraulic oil tank 54. The second drive unit 16 includes the electric motor 16a to which the speed reducer 16c is assembled and an inverter 16b that supplies electric power to the electric motor 16a according to the command. The second drive unit 16 includes a rotation speed sensor 45c for detecting a rotation speed of the electric motor 16a.

[0031] The cab 4 is provided with an air conditioner 26. The air conditioner 26 includes an electric motor 26a and an inverter 26b that supplies electric power to the electric motor 26a according to a command from the controller 9.

[0032] The operator operates the operating units 5 implemented by an operating lever, a joystick, or to operate the travel unit 6, the working unit 7, the slewing unit 8, the working unit 14, and so on. In response to the operating unit 5 operated, an operation signal is output to the controller 9.

[0033] Fig. 3 is a schematic flowchart showing an operation procedure for control on returning the pressure oil in a pipeline for the service actuator in the working vehicle 1. Fig. 4 is a schematic timing chart showing control on returning the pressure oil in the pipeline for the service actuator in the working vehicle 1. Fig. 5A is a schematic circuit diagram schematically showing a state in which the pressure oil is returned in a pipeline 73 for a first service actuator and a state in which the pressure oil is returned in a pipeline 74 for a first service actuator in the working vehicle 1. Fig. 5B is a schematic circuit diagram schematically showing a state in which the pressure oil is returned in a pipeline 77 for a second service actuator and a state in which the pressure oil is returned in a pipeline 78 for a second service actuator in the working vehicle 1. Next, the operation procedure for the control on returning the pressure oil is described below.

[0034] In step S1 of Fig. 3, the controller 9 determines whether a trigger signal has been received. According to the work, where the attachment 51d is replaced with another attachment, the operator presses both the first button 31a (hand button) of the operating unit 5 (operating lever) and the second button 31b (foot button) provided on the floor of the cab 4. In response to the trigger-switch 30 pressed, a trigger signal is sent to the controller 9. In a case where the controller 9 receives the trigger signal, the processing proceeds to step S2.

[0035] In step S2 of Fig. 3, the controller 9 stops the first drive unit 15. As shown in Fig. 4, the controller 9 controls the first electric motor 21a and the second electric motor 21b to change from the idling state corresponding to the minimum rotation speed V0 to a state in which the rotation speed is zero, and stops the first electric motor 21a and the second electric motor 21b. Then, the processing proceeds to step S3.

[0036] In step S3 of Fig. 3, the controller 9 sets a state in which operation of the service actuators is not received. To be specific, the controller 9 sets a state in which operation of a service actuator connected to the port 19a for the first service actuator is not received and sets a state in which operation of a service actuator connected to the port 19b for the second service actuator is not received. The processing then proceeds to step S4.

[0037] In step S4 of Fig. 3, the controller 9 performs control that the pressure oil is returned in the pipeline 73 for the first service actuator, the pipeline 74 for the first service actuator, the pipeline 77 for the second service actuator, and the pipeline 78 for the second service actuator.

[0038] As shown in Figs. 4 and 5A, the controller 9 moves a spool forward by controlling a solenoid valve 71a of the first service actuator control valve 13a to return the pressure oil in the pipeline 73 for the first service actuator, and then the controller 9 stops energizing the solenoid valve 71a. In Fig. 5A, a down arrow 73a indicates the direction of returning the pressure oil. Next, the controller 9 moves the spool backward by controlling a solenoid valve 71b of the first service actuator control valve 13a to return the pressure oil in the pipeline 74 for the first service actuator, and then the controller 9 stops energizing through the solenoid valve 71b. In Fig. 5A, a down arrow 74a indicates the direction of returning the pressure oil.

[0039] Further, as shown in Figs. 4 and 5B, the controller 9 moves a spool forward by controlling a solenoid valve 75a of the control valve 13b for the second service actuator to return the pressure oil in the pipeline 77 for the second service actuator, and then the controller 9 stops energizing the solenoid valve 75a. In Fig. 5B, a down arrow 77a indicates the direction of returning the pressure oil. Next, the controller 9 moves the spool backward by controlling a solenoid valve 75b of the control valve 13b for the second service actuator to return the pressure oil in the pipeline 78 for the second service actuator, and then the controller 9 stops energizing the solenoid valve 75b. In Fig. 5B, a down arrow 78a indicates the direction of returning the pressure oil. The controller 9 returns the pressure oil in the pipelines for the service actuators through the series of operation. The processing then proceeds to step S5.

[0040] In step S5 of Fig. 3, the controller 9 determines whether a first term T1 has elapsed. If the first term T1 has elapsed, then the processing proceeds to step S6.

[0041] In step S6 of Fig. 3, the controller 9 releases the lock of the quick hitch 55.

[0042] As shown in Fig. 4, when the first term T1 has elapsed, the controller 9 performs control that the rotation speed of the first electric motor 21a is increased to the rotation speed V1, moves the spool by controlling a solenoid valve to release the lock in the control valve 13c for the third service actuator (control valve for the quick hitch actuator), releases the lock of the quick hitch 55, and then the controller 9 stops energizing the solenoid valve to release the lock. The controller 9 releases the lock of the quick hitch 55 through the series of operation, and the processing proceeds to step S7.

[0043] The operator engages the quick hitch 55 with an attachment to be used, with both the first button 31a (hand button) and the second button 31b (foot button) pressed. Then, when both the first button 31a (hand button) and the second button 31b (foot button) are released, the trigger signal is finished and the second term T2 elapses. In step S7 of Fig. 3, the controller 9 determines whether the second term T2 has elapsed. If the second term T2 has elapsed, then the processing proceeds to step S8.

[0044] In step S8 of Fig. 3, if the second term T2 has elapsed, then the controller 9 finishes the state in which operation of the service actuator is not received.

[0045] According to the embodiments described above, the working vehicle 1 is achieved which has a simple configuration with no dedicated service pipe and no dedicated solenoid valve and is also capable of automatically returning the pressure oil in the pipeline 73 for the first service actuator and the pipeline 74 for the first service actuator and of automatically returning the pressure oil in the pipeline 77 for the second service actuator and the pipeline 78 for the second service actuator in synchronization with the operation for releasing the lock of the quick hitch 55.

[0046] The configuration of the working vehicle 1 is not limited to the combination of the first electric motor and the second electric motor. The working vehicle 1 may use one electric motor, or use an engine along with the electric motors. Further, the battery to supply DC power to the inverters is not limited to the lithium-ion rechargeable battery, and a secondary battery such as a nickel-metal hydride battery can be used. In this way, the working vehicle 1 is sometimes modified appropriately according to the specifications and so on.

[0047] A working vehicle (1) includes a control valve unit (10) with a service actuator control valve (13a), a first drive unit (15), a travel unit (6), a lower body (2), an upper body (3), a cab (4), a plurality of work units (7, 14) and a plurality of hydraulic traveling motors (17a, 17b), an operation unit (5), a quick hitch (55), an attachment (51d), a trigger-switch (30), a plurality of solenoid valves (71a, 71b) and a plurality of pipelines (73, 74), and a controller (9). The controller (9) performs control that, in a case where the controller (9) receives the trigger signal from the trigger-switch (30) to release the lock of the quick hitch (55), the pressure oil in the plurality of pipelines (73, 74) is returned to the hydraulic oil tank (54) by energizing the plurality of solenoid valves (71a, 71b) with the first drive unit (15) stopped.

Claims

1. A working vehicle (1) comprising:

a control valve unit (10) with a service actuator control valve (13a);

a first drive unit (15) supplying hydraulic oil to a primary side of the control valve unit (10);

a travel unit (6);

a lower body (2) provided with the travel unit (6);

an upper body (3) slewably disposed on the lower body (2);

a second drive unit (16) causing the upper body (3) to slew;

a cab (4) disposed in the upper body;

a plurality of work units (7, 14) and a plurality of hydraulic traveling motors (17a, 17b) driven by pressure oil from secondary side of the control valve unit (10);

an operation unit (5) operated by an operator;

a quick hitch (55) that is driven by the pressure oil to lock in a state of being attached to an arm (51c) of the working unit (7);

an attachment (51d) that comes to connect to the arm (51c) in response to the locking;

a trigger-switch (30) for sending a trigger signal according to operation by the operator;

a plurality of solenoid valves (71a, 71b) of the service actuator control valve (13a);

a plurality of pipelines (73, 74) connected to the service actuator control valve (13a);

a hydraulic oil tank (54); and

a controller (9),

wherein the controller (9) performs control that, in a case where the controller (9) receives the trigger signal from the trigger-switch (30) to release the lock of the quick hitch (55), the pressure oil in the plurality of pipelines (73, 74) is returned to the hydraulic oil tank (54) by energizing the plurality of solenoid valves (71a, 71b) with the first drive unit (15) stopped.

2. The working vehicle (1) according to claim 1,
wherein the controller (9) performs control that the pressure oil is returned by alternately energizing the plurality of solenoid valves (71a, 71b) provided on both sides of a spool of the service actuator control valve (13a).

3. The working vehicle (1) according to claim 2,
wherein the controller (9) performs control that the first drive unit (15) is operated and the lock of the quick hitch (55) is released after a first term (T1) required for returning the pressure oil has elapsed.

4. The working vehicle (1) according to claim 3,
wherein the controller (9) performs control that operation of a service actuator connected to the service actuator control valve (13a) is not received in a second term (T2) in which the trigger-switch (30) is operated.

5. The working vehicle (1) according to any one of claims 1 to 4,
wherein the trigger-switch (30) includes a first button (31a) and a second button (31b) that are provided in the cab (4), and the trigger-switch (30) sends the trigger signal in response to both the first button (31a) and the second button (31b) pressed.

Drawing