JP2013169931A - Transport vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transport vehicle capable of compatibly suppressing the contact of a vessel with the ceiling of a building or the like and securing smooth work for discharging cargoes.SOLUTION: Supply/drain of pressure oil to/from a hoist cylinder 15 which lifts a vessel 3 is performed via a control valve device 21 which has a plurality of changeover positions including a raising position (R), a lowering position (L), a floating position (F) and a neutral position (N). The changeover position of the control valve device 21 is detected by a lever sensor 40. Loads on the vessel 3 are detected by a suspension pressure sensor 42. The inclination position of the vessel 3 is detected by an angle sensor 41. A controller 43 controls the control valve device 21 to be changed over from the raising position (R) to the neutral position (N), when determining that the changeover position of the control valve device 21 is the raising position (R), the vessel 3 is unladen, and the inclination position of the vessel 3 reaches an unladen upper limit inclination angle θb.

Description

  The present invention relates to a transport vehicle such as a dump truck that is suitably used for transporting, for example, crushed stones mined in open-pit mines, quarries, mines, etc., or excavated earth and sand.

  In general, a large transport vehicle called a dump truck has a vessel (loading platform) on the body frame, and a large amount of luggage (for example, crushed stone or earth and sand) to be transported is loaded on the vessel. It is transported and transported toward a transport destination such as an unloading site and a pickup site (see, for example, Patent Document 1).

  This type of conventional transport vehicle includes a self-propelled vehicle body, a vessel provided on the vehicle body that can be tilted (raised and lowered) with a rear end side as a fulcrum and on which a load is loaded, and the vessel and the vehicle body. A hoist cylinder that is provided so as to extend and contract between the hoist cylinder, and tilts the vessel obliquely rearward of the vehicle body, a hydraulic pressure source that supplies and discharges pressure oil to the hoist cylinder to extend or reduce the hoist cylinder, A control valve device that is provided between the hydraulic pressure source and the hoist cylinder and controls the supply and discharge of the pressure oil to and from the hoist cylinder is roughly constituted.

  The control valve device used in such a transport vehicle supplies and discharges the pressure oil from the hydraulic source in one direction to extend the hoist cylinder to lift the vessel, and the pressure oil in the other direction. Supplying / discharging the hoist cylinder by reducing the hoist cylinder and lowering the vessel (turning downward), floating position allowing the hoist cylinder to contract by its own weight and allowing the vessel to fall by its own weight, and supply of pressure oil , There are a total of four switching positions consisting of a neutral position for stopping the discharge and stopping the movement of the hoist cylinder and holding the vessel.

  Here, the control valve device is selectively switched to any one of a total of four switching positions according to a manual operation of an operation lever operated by the operator. The transport vehicle then self-travels to the transport destination with the load loaded in the vessel, and then the hoist cylinder is extended to lift the vessel diagonally backward, and this lifting operation loads the load along the inclination direction of the vessel. Discharge to the landing site.

  That is, when the control valve device is switched from the neutral position to the raised position by the operation of the operation lever by the operator, the pressure oil from the hydraulic source is supplied and discharged in one direction toward the hoist cylinder. As a result, the hoist cylinder extends and lifts the vessel so that it tilts greatly toward the rear of the vehicle body, and the load in the vessel is discharged (soiled out) so as to slide down.

  On the other hand, after such a cargo discharge operation is completed, when the control valve device is switched from the raised position to the floating position, for example, by operating the operation lever, the hoist cylinder is reduced by its own weight on the vessel side. As a result, the vessel lies down so that it gradually descends due to its own weight to a position where it is seated on the vehicle body.

  By the way, the lifting operation of the vessel is configured to stop when reaching a preset upper limit height. Specifically, for example, the configuration in which the lifting operation is mechanically stopped when the hoist cylinder reaches the stroke end, or the inclination angle by the angle sensor that detects the inclination angle of the vessel corresponds to a preset upper limit height. A configuration is adopted in which when the inclination angle is reached, the lifting operation is stopped by performing control to automatically switch the control valve device from the raised position to the neutral position.

Japanese Utility Model Publication No. 3-107345

  According to the prior art, for example, when performing a lifting operation of the vessel in the building for the purpose of maintenance, inspection, maintenance, etc. of the transport vehicle, if the preset upper limit height of the vessel is higher than the ceiling height of the building, There is a risk that the vessel touches the ceiling. In this case, the operator needs to manually stop (suspend) the lifting operation while confirming the inclination angle and height of the vessel in order to stop the lifting operation of the vessel at a height lower than the ceiling height.

  However, when the operator manually stops the lifting operation in this way, it is necessary to determine the stopping position of the lifting operation while checking the inclination angle and height of the vessel, and it takes time for the checking operation. There is a risk that the operation becomes complicated. In addition, there is a possibility that the operator may mistakenly measure the inclination angle and height of the vessel, and in such a case, the vessel may come into contact with the ceiling.

  On the other hand, it is conceivable to set the upper limit height of the vessel lower than the ceiling height of the building. However, in this case, the upper limit height of the vessel when discharging the cargo is also limited, and there is a possibility that the discharge performance is lowered. That is, the angle of inclination of the vessel when discharging the baggage cannot be made sufficiently large, and the baggage tends to stay in the vessel. As a result, it is not possible to perform a smooth baggage discharging operation, which may cause a problem that the discharging operation takes time.

  The present invention has been made in view of the above-described problems of the prior art, and is a transport vehicle that can achieve both the prevention of the vessel from coming into contact with the ceiling of the building and the like and the ensuring of a smooth cargo discharge operation. The purpose is to provide.

  In order to solve the above-described problems, the present invention is provided with a self-propelled vehicle body, a vessel provided on the vehicle body so as to be tiltable and on which a load is loaded, and extendable between the vessel and the vehicle body. A hoist cylinder that inclines the vessel by extending, a hydraulic source that supplies and discharges pressure oil to and from the hoist cylinder, and a control valve device that controls supply and discharge of pressure oil to and from the hoist cylinder. The valve device is a lifting position for extending the hoist cylinder by supplying and discharging the pressure oil and lifting the vessel, and a lowering position for lowering the vessel by reducing the hoist cylinder by supplying and discharging the pressure oil, The hoist cylinder is contracted by its own weight on the vessel side and the floating position allowing the vessel to fall by its own weight, and the supply and discharge of the pressure oil are stopped, and the It is applied to a transport vehicle comprising a plurality of switching positions consisting of a neutral position for holding the vessel stop moving ist cylinder.

  A feature of the configuration adopted by the invention of claim 1 is that a switching position detecting means for detecting which position of the plurality of switching positions the control valve device is switched to, and a load of the vessel. The control valve device is in the raised position by detection signals from the load detection means to detect, the inclination position detection means to detect the inclination position of the vessel, the switching position detection means, the load detection means and the inclination position detection means. The vessel is empty, and the inclined position of the vessel has reached the empty upper limit inclined position lower than the loading upper limit inclined position when a load is loaded on the vessel. The control means is configured to include control means for performing control to switch the control valve device from the raised position to the neutral position when it is determined.

  The invention of claim 2 comprises parking detection means for detecting whether or not the vehicle body is parked, wherein the control means is in addition to detection signals from the switching position detection means, load detection means and tilt position detection means. According to a detection signal from the parking detection means, the control valve device is in the raised position, the vessel is empty, and the vehicle body is parked, and the inclined position of the vessel is the upper limit at the time of empty load. When it is determined that the tilt position has been reached, the control valve device is controlled to be switched from the raised position to the neutral position.

  According to a third aspect of the present invention, the parking detection means comprises a parking brake switch that is provided near the driver's seat of the vehicle body and operates a parking brake.

  The invention of claim 4 includes a vessel lifting limit release switch for enabling the vessel to be lifted to the upper-limit inclined position at the time of loading even when the vessel is determined to be empty. It is in.

  According to a fifth aspect of the present invention, the switching position detecting means comprises a lever sensor that detects a lever position of an operating lever device that is provided near the driver's seat of the vehicle body and performs the switching operation of the control valve device. is there.

  The invention of claim 6 is provided with a suspension for suspending the vehicle body between wheels, and the load detecting means is constituted by a pressure sensor for detecting a change in internal pressure of the suspension due to a change in the amount of product load.

  The invention according to claim 7 is that the tilt position detecting means is constituted by an angle sensor for detecting the tilt angle of the vessel with respect to the vehicle body or a stroke sensor for detecting the extension length of the hoist cylinder.

  According to the first aspect of the present invention, it is possible to satisfy both of suppressing the contact of the vessel with the ceiling of the building and the like and ensuring a smooth discharge operation of the load.

  That is, for example, when the vessel is lifted in the building for the purpose of maintenance, inspection, maintenance, etc. of the transport vehicle, the vessel is empty. In this case, when the vessel reaches the upper limit tilt position when empty, the control valve device is switched from the raised position to the neutral position by the control means, and the lifting operation of the vessel is stopped. For this reason, by setting the upper limit tilt position at the time of unloading to a height lower than the ceiling height of the building, for example, the confirmation work is not time consuming or complicated during the lifting operation of the vessel. The vessel can be prevented from coming into contact with the ceiling of the building. On the other hand, when a load is loaded on the vessel, the vessel can be lifted up to the loading upper limit tilt position that is higher than the empty upper limit tilt position. For this reason, the inclination angle of the vessel can be sufficiently increased, and a smooth discharge operation can be ensured.

  According to the invention of claim 2, when the vessel is empty and the vehicle body is parked, the control means moves the control valve device from the raised position to the neutral position when the vessel reaches the empty upper limit tilt position. Switched. That is, when performing the lifting operation of the vessel in the building for the purpose of maintenance, inspection, maintenance, etc. of the transport vehicle, the vessel is empty and the vehicle body is parked. For this reason, when these two conditions are satisfied, the lifting operation of the vessel stops at the empty upper limit tilt position. As a result, it is possible to achieve both the suppression of the vessel coming into contact with the ceiling of the building and the like, and ensuring a smooth discharge operation. In addition, when it is determined that the vehicle body is not parked, the vessel can be lifted to a position higher than the upper-limit inclined position when empty, even if the vessel is empty. Thereby, the freedom degree of raising operation of the vessel when the vessel is empty can be increased.

  According to the invention of claim 3, since the parking detection means is constituted by the parking brake switch, it is possible to stably detect whether or not the vehicle body is parked depending on whether or not the parking brake switch is turned on. Can do.

  According to the fourth aspect of the present invention, there is provided a configuration including a vessel raising limit release switch for enabling the vessel to be lifted to the upper limit tilt position during loading even when the vessel is empty. For this reason, even when the vessel is empty, for example, when it is necessary to lift the vessel to a position higher than the upper-limit tilt position when empty, by turning on the vessel lifting limit release switch, It can be lifted to a position higher than the upper limit tilt position. Thereby, the freedom degree of the raising operation | movement of a vessel can be raised, suppressing that a vessel contacts the ceiling of a building, etc.

  According to the invention of claim 5, since the switching position detecting means is constituted by the lever sensor, it is possible to stably detect which switching position the control valve device is switched to.

  According to the invention of claim 6, since the load detecting means is constituted by the pressure sensor for detecting the change in the internal pressure of the suspension, it is possible to determine whether the vessel is loaded, that is, whether the vessel is loaded or empty. It can be detected accurately and stably.

  According to the seventh aspect of the present invention, since the tilt position detection means is constituted by an angle sensor or a stroke sensor, the tilt position of the vessel can be detected with high accuracy and stability.

It is a front view which shows the dump truck by 1st Embodiment. It is a front view which shows the state which inclines the vessel | bessel of a dump truck diagonally back and discharges | loads a load. It is a front view which shows the state which inclines the vessel | bessel of a dump truck diagonally back in a building, and performs maintenance, inspection, etc. It is a control circuit diagram including a hydraulic circuit for driving and controlling the hoist cylinder. It is a flowchart which shows the switching control process of the control valve apparatus by the controller in FIG. FIG. 6 is a control circuit diagram including a hydraulic circuit for driving and controlling a hoist cylinder according to a second embodiment. It is a flowchart which shows the switching control process of the control valve apparatus by the controller in FIG. FIG. 6 is a control circuit diagram including a hydraulic circuit for driving and controlling a hoist cylinder according to a third embodiment. It is a flowchart which shows the switching control process of the control valve apparatus by the controller in FIG. It is the same front view as FIG. 3 which shows the dump truck by 4th Embodiment. It is a control circuit diagram including a hydraulic circuit for driving and controlling the hoist cylinder. It is a flowchart which shows the switching control process of the control valve apparatus by the controller in FIG.

  Hereinafter, a transport vehicle according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a crushed stone mined in a mine and a dump truck for transporting earth and sand.

  1 to 5 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a dump truck which is a large transport vehicle. The dump truck 1 includes a vehicle body 2 capable of self-propelling, and a vessel (loading platform) 3 provided on the vehicle body 2 so as to be able to tilt (raise and lower). It is roughly constituted by.

  The vessel 3 is formed as a large container having a total length of 10 to 13 m (meters) for loading a large amount of loads such as crushed stones and earth and sand (hereinafter referred to as earth and sand 4). The rear bottom portion of the vessel 3 is connected to the rear end side of the vehicle body 2 via a connecting pin 5 so as to be tiltable. Further, on the upper front side of the vessel 3, a flange 3 </ b> A that covers a cab 6 described later from above is integrally provided.

  That is, the bottom side of the vessel 3 is rotatably supported by the connecting pin 5 on the rear side of the vehicle body 2. The front side (the flange 3A side) of the vessel 3 is lifted up and down with the position of the connecting pin 5 as a fulcrum by extending or reducing a hoist cylinder 15 described later. Thereby, the vessel 3 is rotated between the transport position shown in FIG. 1 and the discharge position shown in FIG. For example, at the discharge position shown in FIG. 2, a large amount of earth and sand 4 loaded on the vessel 3 is discharged to a predetermined unloading site so as to slide down from the vessel 3 inclined backward in the arrow Y direction.

  Reference numeral 6 denotes a cab provided on the front side of the vehicle body 2 at the lower side of the flange portion 3A. The cab 6 forms a driver's cab in which the operator of the dump truck 1 gets on and off, and has a driver's seat, an accelerator pedal, a brake pedal, a parking brake switch for parking, and an unloading (discharge). A load dump brake switch to be used, a steering handle (both not shown), an operation lever 39A (see FIG. 4) described later, and the like are provided.

  The collar portion 3A of the vessel 3 covers the cab 6 almost completely from the upper side, thereby protecting the cab 6 from flying stones such as rocks. Further, the flange portion 3A of the vessel 3 has a function of protecting the operator in the cab 6 when the vehicle (dump truck 1) falls.

  Reference numeral 7 denotes left and right front wheels (only one is shown) rotatably provided on the front side of the vehicle body 2. These front wheels 7 constitute steering wheels that are steered (steered) by an operator of the dump truck 1. The front wheel 7 is formed with a tire diameter (outer diameter dimension) of, for example, 2 to 4 meters, as with the rear wheel 9 described later. A front suspension 8 made of, for example, a hydraulic shock absorber or the like is provided between the front portion of the vehicle body 2 and the front wheel 7. The front suspension 8 suspends the front portion side of the vehicle body 2 between the front wheel 7 and the front wheel 7. It is. The front suspension 8 is provided with a suspension pressure sensor 42 described later.

  Reference numeral 9 denotes left and right rear wheels (only one is shown) rotatably provided on the rear side of the vehicle body 2. These rear wheels 9 constitute driving wheels of the dump truck 1 and are rotationally driven by a travel drive device (not shown). A rear suspension 10 made of, for example, a hydraulic shock absorber is provided between the rear wheel 9 and the rear portion of the vehicle body 2. The rear suspension 10 suspends the rear portion side of the vehicle body 2 from the rear wheel 9. It is. The rear suspension 10 is provided with a suspension pressure sensor 42 described later.

  Reference numeral 11 denotes a left and right front wheel brake device (only one is shown) that applies a braking force to the left and right front wheels 7, and 12 denotes a left and right rear wheel that applies a braking force to the left and right rear wheels 9. A brake device (only one shown) is shown. These brake devices 11 and 12 are used as service brakes (service brakes), and are configured as, for example, hydraulic brake devices. Each of the brake devices 11 and 12 applies a braking force to the front wheels 7 and the rear wheels 9 based on, for example, an operation of a brake pedal by an operator.

  Further, the rear wheel brake device 12 applies a braking force to the rear wheel 9 based on the operation of the load dump brake switch by the operator when the load is discharged from the vessel 3 at an unloading place or the like. Thereby, when discharging a load from the vessel 3, the dump truck 1 can be prevented from moving from the stop position.

  Reference numeral 13 denotes a left and right parking brake device (only one is shown) that applies a braking force to the left and right rear wheels 9 when the dump truck 1 is parked. The parking brake device 13 can be configured as a brake device having a smaller capacity than the left and right rear wheel brake devices 12, for example. The parking brake device 13 applies a braking force to the rear wheel 9 based on the operation of the parking brake switch by the operator when the dump truck 1 is parked.

  Reference numeral 14 denotes an engine as a prime mover, and the engine 14 is composed of, for example, a large diesel engine. The engine 14 is provided in the vehicle body 2 at the lower side of the cab 6 and rotationally drives a hydraulic pump 16 (see FIG. 4) described later.

  Reference numeral 15 denotes a pair of left and right hoist cylinders (only one is shown) provided in a stretchable manner between the vessel 3 and the vehicle body 2. The hoist cylinder 15 is composed of a multistage (for example, two-stage) hydraulic cylinder, and as shown in FIG. 4, an outer cylinder portion 15A located on the outer side and an outer cylinder portion 15A that is extendable and retractable. The inner cylinder portion 15B, and a piston rod 15C and a piston 15D which are provided in the inner cylinder portion 15B so as to be extendable and contractable. And the inside of the outer cylinder part 15A of the hoist cylinder 15 is defined by the inner cylinder part 15B, the piston rod 15C and the piston 15D into three chambers of rod side oil chambers 15E and 15F and a bottom side oil chamber 15G.

  At this time, the rod-side oil chamber 15F communicates with either the rod-side oil chamber 15E or the bottom-side oil chamber 15G via a port 15H provided in the inner cylinder portion 15B. That is, when the piston 15D of the hoist cylinder 15 is slidably displaced in the axial direction (upward and downward) in the inner cylinder portion 15B so that the piston 15D is positioned above the port 15H, as shown in FIG. When the rod side oil chamber 15F is communicated with the rod side oil chamber 15E via the port 15H and the piston 15D is displaced to a position below the port 15H, the rod side oil chamber 15F is connected via the port 15H. The bottom side oil chamber 15G is communicated.

  When the pressure oil is supplied into the bottom side oil chamber 15G from the hydraulic pump 16 described later, the hoist cylinder 15 extends downward together with the piston rod 15C, and the inner cylinder portion 15B When the maximum extension occurs, only the piston rod 15C further extends downward. Thereby, the hoist cylinder 15 rotates the vessel 3 to the raising position (soil discharging position) inclined obliquely rearward with the connecting pin 5 as a fulcrum.

  On the other hand, in the hoist cylinder 15, when pressure oil is supplied from the hydraulic pump 16 into the rod side oil chamber 15 </ b> E with the piston rod 15 </ b> C extended to the maximum, only the piston rod 15 </ b> C is first contracted, and thereafter the inner cylinder portion 15 </ b> B. Is reduced together with the piston rod 15C. Accordingly, the hoist cylinder 15 rotates the vessel 3 to the lowered position (transport position) with the connecting pin 5 as a fulcrum.

  Next, a hydraulic circuit for driving the hoist cylinder 15 will be described with reference to FIG.

  Reference numeral 16 denotes a hydraulic pump. The hydraulic pump 16 constitutes a hydraulic source that supplies and discharges pressure oil to and from the hoist cylinder 15 together with a hydraulic oil tank 17 (hereinafter referred to as a tank 17). For example, as shown in FIG. 1, the tank 17 is positioned below the vessel 3 and attached to the side surface of the vehicle body 2. Here, the hydraulic oil (oil) stored in the tank 17 is sucked into the hydraulic pump 16 when the hydraulic pump 16 is rotationally driven by the engine 14. High pressure oil is discharged into the pump line 18 from the discharge side of the hydraulic pump 16. The return oil from the hoist cylinder 15 is discharged to the tank 17 through the low-pressure tank pipe line 19.

  Reference numerals 20A and 20B denote hydraulic pipes constituting a pair of main pipes connected to the bottom side oil chamber 15G and the rod side oil chambers 15E and 15F of the hoist cylinder 15. The hydraulic pipes 20A and 20B are connected to a hydraulic power source (hydraulic pump 16, tank 17) via a control valve device 21 to be described later, and the tip side thereof passes through the inside of the piston rod 15C of the hoist cylinder 15 and is hoisted. The cylinder 15 is connected to the bottom side oil chamber 15G and the rod side oil chamber 15E. Further, the rod-side oil chamber 15F of the hoist cylinder 15 is communicated with the rod-side oil chamber 15E or the bottom-side oil chamber 15G via the port 15H according to the sliding position of the piston 15D. The hydraulic lines 20A and 20B supply the pressure oil from the hydraulic pump 16 to the bottom side oil chamber 15G, the rod side oil chamber 15E and / or the rod side oil chamber 15F of the hoist cylinder 15. Further, the pressure oil in the bottom side oil chamber 15G, the rod side oil chamber 15E and / or the rod side oil chamber 15F is discharged to the tank 17 through one of the hydraulic lines 20A and 20B.

  Reference numeral 21 denotes a control valve device provided between the hydraulic pump 16, the tank 17 and the hoist cylinder 15. The control valve device 21 controls supply and discharge of pressure oil to and from the hoist cylinder 15. For example, the high pressure side oil passage 22, the low pressure side oil passages 23 </ b> A and 23 </ b> B, the center bypass oil passage 24, and the first directional control valve 25. And a second directional control valve 26. The first directional control valve 25 and the second directional control valve 26 are connected in parallel to each other via the high-pressure side oil passage 22, the low-pressure side oil passages 23 </ b> A and 23 </ b> B, and the center bypass oil passage 24.

  The high-pressure side oil passage 22 is connected to the discharge side of the hydraulic pump 16 via the pump pipe 18, and a branch pipe 33 described later is connected to the middle portion. The low-pressure side oil passage 23 </ b> A is disposed on the first directional control valve 25 side, and connects actuator side oil passages 27 </ b> A and 27 </ b> B, which will be described later, to the tank 17 via the tank conduit 19. The low pressure side oil passage 23 </ b> B is disposed on the second directional control valve 26 side, and connects actuator side oil passages 28 </ b> A and 28 </ b> B, which will be described later, to the tank 17 via the tank conduit 19. The center bypass oil passage 24 allows the pump line 18 and the tank line 19 to communicate with each other when both the first and second directional control valves 25 and 26 are in the neutral position (N). As a result, the hydraulic pump 16 is unloaded, and the discharge pressure (pressure in the pump line 18) is maintained at a low pressure close to the tank pressure.

  A pair of actuator side oil passages 27A and 27B are provided on the output side of the first directional control valve 25, and the actuator side oil passages 27A and 27B are connected to the bottom of the hoist cylinder 15 via the hydraulic lines 20A and 20B. It is connected to the side oil chamber 15G and the rod side oil chambers 15E and 15F, respectively. A pair of actuator side oil passages 28A and 28B are provided on the output side of the second directional control valve 26, and the actuator side oil passages 28A and 28B are connected to the bottom of the hoist cylinder 15 via the hydraulic lines 20A and 20B. It is connected to the side oil chamber 15G and the rod side oil chambers 15E and 15F, respectively.

  The first directional control valve 25 and the second directional control valve 26 are each configured by, for example, a hydraulic pilot type directional control valve at 6 port 3 position. The first directional control valve 25 has a pair of hydraulic pilot portions 25A and 25B. The first directional control valve 25 is switched from the neutral position (N) to the raised position (R) when a pilot pressure is supplied from a solenoid valve 36 for raising operation, which will be described later, to the hydraulic pilot portion 25A, and the floating position described later. When the pilot pressure is supplied from the operation solenoid valve 38 to the hydraulic pilot unit 25B, the operation is switched from the neutral position (N) to the floating position (F).

  The second directional control valve 26 has a pair of hydraulic pilot portions 26A and 26B. The second directional control valve 26 is switched from the neutral position (N) to the raised position (R) when the pilot pressure is supplied from the solenoid valve 36 for raising operation to the hydraulic pilot part 26A, and is used for lowering operation described later. When the pilot pressure is supplied from the electromagnetic valve 37 to the hydraulic pilot portion 26B, the position is switched from the neutral position (N) to the lowered position (L).

  That is, as shown in FIG. 4, the control valve device 21 has a plurality of switching positions including a neutral position (N), a raised position (R), a lowered position (L), and a floating position (F). It can be switched to any of the switching positions. Here, a case where the control valve device 21 is in the neutral position (N) will be described. In this case, the control valve device 21 has a holding position for stopping the movement of the hoist cylinder 15 and holding the vessel 3 by arranging the first and second directional control valves 25 and 26 at the neutral position (N). Become. At the neutral position (N) that is the holding position, the supply and discharge of the pressure oil to and from the hoist cylinder 15 via the actuator side oil passages 27A and 27B and the actuator side oil passages 28A and 28B are stopped.

  The case where the control valve device 21 is in the raised position will be described. In this case, the pilot pressure is supplied to the hydraulic pilot portions 25A and 26A of the first and second directional control valves 25 and 26 from a solenoid valve 36 for raising operation, which will be described later, and the first and second directional control valves. 25 and 26 are both switched from the neutral position (N) to the raised position (R). When the first and second directional control valves 25 and 26 are in the raised position (R), the pressure oil from the hydraulic pump 16 is supplied from the pump line 18, the high-pressure side oil path 22, and the first and second directional control valves. 25, 26, actuator side oil passages 27A, 28A, and hydraulic line 20A are supplied into the bottom side oil chamber 15G of the hoist cylinder 15. At this time, the oil liquid in the rod side oil chambers 15E and 15F is changed to the hydraulic position 20B, the actuator side oil path 27B, and the direction control valve 25 when the first direction control valve 25 is switched to the raised position (R). Then, the oil is returned to the tank 17 through the low-pressure side oil passage 23A and the tank conduit 19.

  As a result, the inner cylinder portion 15B and / or the piston rod 15C of the hoist cylinder 15 are extended by the pressure oil in the bottom side oil chamber 15G and lift the vessel 3 to the discharge position shown in FIG. That is, at this time, the first and second directional control valves 25 and 26 of the control valve device 21 are both placed in the raised position (R), and the hoist cylinder 15 is extended by the hydraulic pressure so that the vessel 3 faces upward. It is something to lift.

  On the other hand, a case where the control valve device 21 is in the floating position will be described. In this case, a pilot pressure is supplied from a solenoid valve 38 for floating operation described later to the hydraulic pilot portion 25B of the first directional control valve 25, and the first directional control valve 25 is moved from the neutral position (N) to the floating position. Switching to (F), the second directional control valve 26 is placed in the neutral position (N). When the first directional control valve 25 is in the floating position (F), the actuator side oil passage 27A is connected to the low pressure side oil passage 23A and the tank conduit 19 via the direction control valve 25. The actuator side oil passage 27B is connected to the tank pipe line 19 side via a check valve 29B described later, and the other actuator side oil passage 28B is connected to the low pressure side oil passage 23B via a check valve 31B described later. , Connected to the tank line 19.

  As a result, the hoist cylinder 15 is reduced according to the load (self-weight) from the vessel 3, and the oil in the bottom side oil chamber 15G is hydraulic line 20A, actuator side oil path 27A, direction control valve 25, low pressure side oil. The oil is discharged toward the tank 17 through the passage 23A and the tank conduit 19, and the oil in the tank 17 is transferred from the check valves 29B and 31B described later to the actuator-side oil passage in the rod-side oil chambers 15E and 15F. It is replenished via 27B, 28B and the hydraulic line 20B. That is, at this time, the first directional control valve 25 of the control valve device 21 is arranged at the floating position (F) that allows the vessel 3 to fall by its own weight.

  The case where the control valve device 21 is in the lowered position will be described. In this case, pilot pressure is supplied from a solenoid valve 37 for lowering operation, which will be described later, to the hydraulic pilot portion 26B of the second directional control valve 26, and the second directional control valve 26 is moved from the neutral position (N) to the lowered position. Switching to (L), the first directional control valve 25 is arranged in the neutral position (N). When the second directional control valve 26 is in the lowered position (L), the pressure oil from the hydraulic pump 16 is pump line 18, high pressure side oil path 22, second directional control valve 26, actuator side oil path 28 </ b> B, hydraulic pressure. It is supplied into the rod side oil chambers 15E and 15F of the hoist cylinder 15 through the pipe line 20B. The oil in the bottom side oil chamber 15G is returned to the tank 17 via the hydraulic line 20A, the actuator side oil path 28A, the second direction control valve 26, the low pressure side oil path 23B, and the tank line 19. .

  As a result, the inner cylinder portion 15B and / or the piston rod 15C of the hoist cylinder 15 is contracted by the pressure oil in the rod side oil chambers 15E and 15F and rotates the vessel 3 downward to the transport position shown in FIG. . That is, at this time, the second directional control valve 26 of the control valve device 21 is disposed at the lowered position (L), and the hoist cylinder 15 is reduced to the position where the vessel 3 is seated on the vehicle body 2 by being reduced by the hydraulic pressure. And lowering (lowering).

  29A and 29B are makeup check valves arranged on the first directional control valve 25 side of the control valve device 21. The check valves 29A and 29B are provided around the first directional control valve 25 between the actuator side oil passages 27A and 27B and the low pressure side oil passage 23A (tank pipe line 19). The check valves 29A and 29B allow the oil in the tank 17 to flow from the low-pressure side oil passage 23A (tank conduit 19) to the bottom oil of the hoist cylinder 15 via the actuator-side oil passages 27A and 27B and the hydraulic conduits 20A and 20B. It allows to flow toward the chamber 15G and the rod side oil chambers 15E and 15F, and prevents the flow in the reverse direction. The bottom side oil chamber 15G and the rod side oil chambers 15E and 15F of the hoist cylinder 15 have negative pressure in the bottom side oil chamber 15G and the rod side oil chambers 15E and 15F due to the oil supplied through the check valves 29A and 29B. Can be prevented.

  30A and 30B are relief valves for preventing overload provided in the control valve device 21. The relief valves 30A and 30B are provided by bypassing the first directional control valve 25 between the actuator side oil passages 27A and 27B and the low pressure side oil passage 23A (tank pipe line 19), and check valves 29A and 29B. Connected in parallel. One relief valve 30A of the relief valves 30A and 30B opens to relieve the excess pressure on the bottom side oil chamber 15G side when an overload in the reduction direction acts on the hoist cylinder 15. The other relief valve 30B opens to relieve the excess pressure on the rod side oil chambers 15E and 15F when an overload in the extending direction acts on the hoist cylinder 15.

  31A and 31B are make-up check valves disposed on the second directional control valve 26 side of the control valve device 21. The check valves 31A and 31B are provided around the second directional control valve 26 between the actuator side oil passages 28A and 28B and the low pressure side oil passage 23B (tank pipe line 19). The check valves 31A and 31B are configured so that, for example, the oil liquid in the tank 17 flows from the low pressure side oil passage 23B (tank conduit 19) to the bottom side of the hoist cylinder 15 via the actuator side oil passages 28A and 28B and the hydraulic conduits 20A and 20B. Permits flow toward the oil chamber 15G and the rod-side oil chambers 15E and 15F, and prevents flow in the opposite direction. As a result, the check valves 31A and 31B supply oil to the bottom side oil chamber 15G and the rod side oil chambers 15E and 15F of the hoist cylinder 15.

  Reference numeral 32 denotes a main relief valve provided between the pump line 18 and the low-pressure side oil path 23A (tank 17). The relief valve 32 determines the maximum discharge pressure of the hydraulic pump 16, and the pump line 18 The internal pressure is kept below the maximum discharge pressure. That is, the relief valve 32 is opened when an excessive pressure exceeding the maximum discharge pressure is generated in the pump line 18, and the excessive pressure at this time is relieved to the tank 17 side.

  Reference numeral 33 denotes a branch pipe branched from the high-pressure side oil passage 22 (pump pipe 18). The branch pipe 33 is connected to a pilot pressure supply pipe 35 through a pressure reducing valve 34. The pressure reducing valve 34 switches between the valve closing position (a) and the valve opening position (b) shown in FIG. 4 in order to reduce the pressure oil in the branch pipe 33 and supply it to the pilot pressure supply line 35. As a result, the pressure in the pilot pressure supply pipe 35 is maintained at a preset pressure (that is, a pressure lower than that in the branch pipe 33) by the pressure reducing valve 34.

  36, 37, and 38 are electromagnetic valves for supplying pilot pressure to the hydraulic pilot portions 25 </ b> A and 26 </ b> A of the first and second directional control valves 25 and 26 of the control valve device 21. These electromagnetic valves 36 to 38 are provided between a controller 43 and a control valve device 21 which will be described later. The solenoid valves 36 to 38 are individually opened and closed according to an operation of an operation lever device 39 described later, and the control valve device 21 (the hydraulic pilot portion 25A of the first and second directional control valves 25 and 26) is opened. , 26A) is supplied with a pilot pressure for switching control.

  Among these, the raising solenoid valve 36 is switched from the valve closing position (c) to the valve opening position (d) in accordance with the excitation signal from the controller 43, and from the pilot pressure supply line 35 at this valve opening position (d). Pilot pressure for raising operation is supplied to the hydraulic pilot portions 25A and 26A of the first and second directional control valves 25 and 26. Thereby, the direction control valves 25 and 26 of the control valve device 21 are switched from the neutral position (N) shown in FIG. 4 to the raised position (R).

  The lowering solenoid valve 37 is switched from the valve closing position (c) to the valve opening position (d) in accordance with the excitation signal from the controller 43, and from the pilot pressure supply line 35 at this valve opening position (d). A pilot pressure for lowering operation is supplied toward the hydraulic pilot portion 26B of the second directional control valve 26. Accordingly, the second directional control valve 26 of the control valve device 21 is switched from the neutral position (N) shown in FIG. 4 to the lowered position (L). At this time, since the solenoid valves 36 and 38 are demagnetized and are in the closed position (C), the first directional control valve 25 is disposed in the neutral position (N).

  On the other hand, the solenoid valve 38 for floating operation is switched from the valve closing position (c) to the valve opening position (d) according to the excitation signal from the controller 43, and from the pilot pressure supply line 35 at this valve opening position (d). A pilot pressure for floating operation is supplied toward the hydraulic pilot portion 25B of the first directional control valve 25. Thereby, the first directional control valve 25 of the control valve device 21 is switched from the neutral position (N) shown in FIG. 4 to the floating position (F). At this time, since the solenoid valves 36 and 37 are demagnetized and are in the closed position (C), the second direction control valve 26 is disposed in the neutral position (N).

  Reference numeral 39 denotes an operation lever device as an operation device for performing a switching operation of the control valve device 21. The operation lever device 39 is constituted by, for example, an electric lever device, and is provided in the vicinity of the driver's seat of the cab 6. The operating lever device 39 has an operating lever 39A that is manually tilted by an operator in the cab 6. The operation lever 39A corresponds to each switching position of the control valve device 21, that is, the neutral position (N), the raised position (R), the lowered position (L), and the floating position (F). ), The raised position (R), the lowered position (L), and the floating position (F).

  Reference numeral 40 denotes a lever sensor as switching position detecting means attached to the operation lever device 39. The lever sensor 40 detects the operation position (lever position) of the operation lever 39A by the operator and outputs a detection signal to the controller 43 described later. The lever sensor 40 detects whether the operation lever 39A of the operation lever device 39 is in the neutral position (N), the raised position (R), the lowered position (L), or the floating position (F). The control valve device 21 is detected to which switching position.

  Reference numeral 41 denotes an angle sensor as an inclination position detecting means employed in the present embodiment. The angle sensor 41 is provided near the connecting pin 5 and provided on the rear side of the vehicle body 2 as shown in FIG. ing. The angle sensor 41 detects the tilt position of the vessel 3, and as shown in FIGS. 2 and 3, detects the tilt angle θ (θa, θb) of the vessel 3 with respect to the vehicle body 2, and the detection signal is described later. Output to the controller 43.

  Reference numeral 42 denotes a suspension pressure sensor as load detection means for detecting the load of the vessel 3, and the suspension pressure sensor 42 is provided in each of the front suspension 8 and the rear suspension 10 as shown in FIG. Is detected, and a detection signal is output to a controller 43 described later.

  On the controller 43 side, according to the detection signal from the suspension pressure sensor 42, it is determined whether the vessel 3 is loaded or empty. That is, the internal pressure (pressure) of the suspensions 8 and 10 is lowest when the vessel 3 is empty, and increases as the load (sediment 4) loaded on the vessel 3 increases. Therefore, when the suspension pressure detected by the suspension pressure sensor 42 exceeds the suspension pressure at the time of unloading which is a threshold for determining whether or not the load is unloaded, the load is loaded on the vessel 3. Similarly, when the suspension pressure is equal to or lower than the suspension pressure when empty, it can be determined that the vessel 3 is empty.

  Reference numeral 43 denotes a controller as a control means comprising a microcomputer. The controller 43 has an input side connected to the lever sensor 40, the angle sensor 41, the suspension pressure sensor 42, and the like, and an output side connected to the solenoid valves 36 to 38 and the like. Further, the controller 43 has a storage unit 43A composed of ROM, RAM, nonvolatile memory, and the like. In this storage unit 43A, a processing program shown in FIG. 5 to be described later, an upper limit inclination position of the vessel 3 at the time of loading, and In order to determine whether the upper limit inclination angle θa at the time of loading, the upper limit inclination angle θb at the time of the upper limit of the vessel 3 at the time of empty loading, and whether the vessel 3 is empty (loading a load). The threshold value (suspension pressure when empty) is stored.

  Here, the controller 43 performs the lifting operation of the vessel 3 in accordance with the processing program of FIG. Specifically, when the controller 43 determines that the load is loaded on the vessel 3 based on the detection signal of the suspension pressure sensor 42, the controller 43 performs the lifting operation of the vessel 3 as shown in FIG. It is configured to allow up to. On the other hand, when the controller 43 determines that the vessel 3 is empty according to the detection signal of the suspension pressure sensor 42, the controller 43 performs the lifting operation of the vessel 3 as shown in FIG. It is configured to limit to the empty upper limit inclination angle θb at which the height of the vessel 3 is lower than the upper limit inclination angle θa.

  For this reason, the controller 43 detects that the lever position of the operation lever 39A corresponding to the switching position of the control valve device 21 is in the raised position (R) based on detection signals from the lever sensor 40, the angle sensor 41, and the suspension pressure sensor 42. When it is determined that the vessel 3 is empty and the inclination angle θ of the vessel 3 has reached the upper-limit inclination angle θb when empty, the directional control valves 25 and 26 of the control valve device 21 are raised. Control to switch from (R) to neutral position (N) is performed. In this case, as shown in FIG. 3, by setting the unloaded upper limit inclination angle θb to an angle corresponding to a height lower than the ceiling height of the building 44, the vessel 3 is lifted during the lifting operation. 3 can be prevented from contacting the ceiling of the building 44 or the like.

  On the other hand, when the load is loaded on the vessel 3, the controller 43 determines that the load upper limit inclination angle θa at which the height of the vessel 3 is higher than the empty upper limit inclination angle θb has been reached. Control for switching the direction control valves 25 and 26 of the control valve device 21 from the raised position (R) to the neutral position (N) is performed. As a result, when the package is discharged, the inclination angle θ of the vessel 3 can be sufficiently increased, and a smooth discharge operation can be ensured.

  The dump truck 1 according to the first embodiment has the above-described configuration. Next, the operation thereof will be described.

  First, in a quarry such as a mine, earth and sand 4 serving as luggage is loaded on the vessel 3 using, for example, a large hydraulic excavator (not shown). At this time, the vessel 3 is placed at the carrying position shown in FIG. 1, and the dump truck 1 carries the dump truck 1 toward the unloading site with a large amount of earth and sand 4 loaded on the vessel 3.

  In an unloading place or the like, when an operator in the cab 6 manually tilts the operation lever 39A of the operation lever device 39 from the neutral position (N) to the lift position (R), the controller 43 performs a lifting operation. An excitation signal is output to the electromagnetic valve 36. As a result, the solenoid valve 36 is switched from the valve closing position (c) to the valve opening position (d), and the pilot pressure supply lines 35 to the hydraulic pilot portions 25A, 26A of the directional control valves 25, 26 of the control valve device 21. A pilot pressure for raising operation is supplied toward.

  As a result, the control valve device 21 is switched from the neutral position (N) to the raised position (R). As a result, the pressure oil from the hydraulic pump 16 passes through the pump line 18, the high pressure side oil path 22, the first and second directional control valves 25 and 26, the actuator side oil paths 27A and 28A, and the hydraulic line 20A. To the bottom oil chamber 15G of the hoist cylinder 15. The oil in the rod-side oil chambers 15E and 15F is sent to the tank 17 via the hydraulic line 20B, the actuator-side oil path 27B, the first directional control valve 25, the low-pressure side oil path 23A, and the tank line 19. Is returned.

  Thereby, the inner cylinder part 15B and / or the piston rod 15C of the hoist cylinder 15 are extended in the direction indicated by the arrow Z in FIG. 2 by the pressure oil in the bottom side oil chamber 15G, and the vessel 3 is inclined obliquely rearward. Lift to the soil removal position shown in FIG. At this time, the dump truck 1 is moved to the unloading site so as to slide down the earth and sand 4 in the vessel 3 by rotating the vessel 3 in an inclined posture as shown in FIG. 2 with the connecting pin 5 as a fulcrum. It can be discharged in the direction indicated by the arrow Y.

  At this time, when the operator releases his hand from the operation lever 39A, the operation lever 39A is automatically returned to the neutral position (N) by a return spring (not shown). Therefore, the signal output from the controller 43 to the electromagnetic valve 36 is demagnetized (OFF), and the electromagnetic valve 36 for raising operation returns to the valve closing position (c) shown in FIG. Thereby, the direction control valves 25 and 26 of the control valve device 21 are automatically returned to the neutral position (N), and supply and discharge of pressure oil to the bottom side oil chamber 15G and the rod side oil chambers 15E and 15F of the hoist cylinder 15 are performed. 2 and the inner cylinder portion 15B and the piston rod 15C can be maintained in the extended state, and the vessel 3 can be temporarily stopped in the inclined posture shown in FIG.

  Next, when the discharging operation of the earth and sand 4 is completed, the operator manually tilts the operation lever 39A from the neutral position (N) to the floating position (F), so that the controller 43 switches the electromagnetic lever 38 for the floating operation. An excitation signal is output. For this reason, the solenoid valve 38 for floating operation is switched from the valve closing position (c) to the valve opening position (d), and is directed from the pilot pressure supply line 35 to the hydraulic pilot portion 25B of the first directional control valve 25. Pilot pressure for floating operation is supplied.

  Thereby, the first directional control valve 25 of the control valve device 21 is switched from the neutral position (N) to the floating position (F). At this time, since the solenoid valves 36 and 37 are demagnetized and are in the closed position (C), the second direction control valve 26 is disposed in the neutral position (N). As a result, the actuator side oil passage 27A is connected to the low pressure side oil passage 23A and the tank pipeline 19 via the direction control valve 25, and the actuator side oil passage 27B is connected to the tank pipeline 19 side via the check valve 29B. The other actuator side oil passage 28B is connected to the low pressure side oil passage 23B and the tank pipe line 19 via the check valve 31B. As a result, the hoist cylinder 15 is reduced in accordance with the load (self-weight) from the vessel 3, the oil in the bottom side oil chamber 15G is discharged toward the tank 17, and in the rod side oil chambers 15E and 15F. The oil solution in the tank 17 is supplied via the check valve 29B and / or the check valve 31B. The hoist cylinder 15 allows the vessel 3 to descend to the transport position shown in FIG. 1 by allowing the vessel 3 to drop due to its own weight, and allows the vessel 3 to be seated on the vehicle body 2.

  On the other hand, when the dump truck 1 is tilted due to unevenness on the work site, sloping ground or the like, the vessel 3 may not be lowered by its own weight even when the control valve device 21 is switched to the floating position (F). However, in such a case, when the operator tilts the operation lever 39A to the lowered position (L), an excitation signal is output from the controller 43 to the electromagnetic valve 37 for the lowering operation. For this reason, the solenoid valve 37 for lowering operation is switched from the valve closing position (c) to the valve opening position (d), and is directed from the pilot pressure supply line 35 toward the hydraulic pilot portion 26B of the second directional control valve 26. Thus, pilot pressure for lowering operation is supplied.

  As a result, the second directional control valve 26 of the control valve device 21 is switched from the neutral position (N) to the lowered position (L). At this time, since the solenoid valves 36 and 38 are demagnetized and are in the closed position (C), the first directional control valve 25 is disposed in the neutral position (N). As a result, the pressure oil from the hydraulic pump 16 is supplied to the rod side oil of the hoist cylinder 15 via the pump line 18, the high pressure side oil path 22, the second directional control valve 26, the actuator side oil path 28B, and the hydraulic line 20B. It is supplied into the chambers 15E and 15F. The oil in the bottom side oil chamber 15G is returned to the tank 17 via the hydraulic line 20A, the actuator side oil path 28A, the second direction control valve 26, the low pressure side oil path 23B, and the tank line 19. . As a result, the hoist cylinder 15 is contracted by the pressure oil supplied into the rod-side oil chambers 15E and 15F, so that the inner cylinder portion 15B and / or the piston rod 15C are reduced into the outer cylinder portion 15A, and the vessel 3 is moved to the hoist cylinder. The hydraulic pressure of 15 can turn downward to the transport position shown in FIG. 1, and the vessel 3 can be forcibly seated on the vehicle body 2.

  However, when the control valve device 21 is switched to the lowered position (L) in this way, the hoist cylinder 15 is contracted by the hydraulic pressure, so that an impact may occur when the vessel 3 is seated on the vehicle body 2. There is a possibility that an extra load is applied to the vessel 3 and the vehicle body 2. Further, after that, when the position is switched to the lowered position (L), the vessel 3 remains strongly pressed on the vehicle body 2, and the hydraulic pressure from the hoist cylinder 15 is applied to the contact surface between the vessel 3 and the vehicle body 2. Acts as an extra load. For this reason, the operator of the dump truck 1 holds the operation lever 39A in the floating position (F) while the vehicle is traveling. As a result, the control valve device 21 is switched to the floating position (F), the vessel 3 continues to be seated on the vehicle body 2 by its own weight, and the hoist cylinder 15 can also be kept in a contracted state using the own weight on the vessel 3 side. .

  By the way, when the lifting operation of the vessel 3 is performed in the building 44 for the purpose of maintenance, inspection, maintenance, etc. of the dump truck 1, if the upper limit height of the vessel 3 is higher than the ceiling height of the building 44, the vessel 3 is moved to the building 44. There is a risk of touching the ceiling. Therefore, in the first embodiment, when the lifting operation of the vessel 3 is performed, the switching control of the control valve device 21 by the controller 43 is performed according to the processing program shown in FIG.

  That is, when the processing operation of FIG. 5 is started by the operation (start) of the engine 9, in step 1, the position signal of the operation lever 39A is read (detected) from the lever sensor 40. Then, it progresses to step 2, and it is determined whether the switching position (lever position) of the operation lever 39A corresponding to the switching position of the control valve apparatus 21 is a raising position (R). If “NO” in step 2, that is, if it is determined that the switching position of the operation lever 39A is not the raised position (R), the process returns to the start via the return, and the processes in step 1 and subsequent steps are repeated.

  On the other hand, if “YES” in step 2, that is, if it is determined that the switching position of the operation lever 39 A is the raised position (R), the process proceeds to step 3 where the front suspension 8 and the rear suspension 10 are moved from the suspension pressure sensor 42. Read (detect) the internal pressure (pressure). Subsequently, the process proceeds to step 4 to determine whether or not the vessel 3 is empty. This determination can be made based on, for example, whether or not the suspension pressure detected in step 3 exceeds a preset suspension pressure during empty load.

  That is, when the suspension pressure detected in step 3 exceeds the suspension pressure at the time of empty load, it can be determined that the load is loaded on the vessel 3, and the suspension pressure is also equal to or lower than the suspension pressure at the time of empty load. In some cases, it can be determined that the vessel 3 is empty. The suspension pressure at the time of empty load, which is a threshold value of whether or not the vehicle is empty, is determined based on experiments, calculations, simulations, etc. in advance so that it can be appropriately determined whether or not the vehicle is empty. Set.

  If it is determined in step 4 that “NO”, that is, the vessel 3 is not empty (a load is loaded on the vessel 3), the process proceeds to step 5, and the upper limit inclination position of the vessel 3, that is, when the vessel 3 is loaded. The upper limit angle corresponding to the maximum height of the vessel 3 is set to the upper limit angle θa during loading. Next, the process proceeds to step 6, and the inclination angle θ of the vessel 3 is read (detected) from the angle sensor 41, and the process proceeds to the next step 7.

  In step 7, it is determined whether or not the inclination angle θ of the vessel 3 detected in step 6 is less than the upper limit angle θa during loading. If it is determined in step 7 that the inclination angle θ of the vessel 3 is less than the upper limit angle θa during loading, the process proceeds to step 8 where the control valve device 21 is switched to the raised position (R). That is, an excitation signal is output from the controller 43 to the solenoid valve 36 for raising operation, and the solenoid valve 36 is switched from the valve closing position (c) to the valve opening position (d). As a result, the pilot pressure for raising operation is supplied from the pilot pressure supply line 35 toward the hydraulic pilot portions 25A and 26A of the direction control valves 25 and 26 of the control valve device 21, and the first and second direction control valves. Both 25 and 26 are switched to the raised position (R). As a result, the hoist cylinder 15 extends, and the vessel 3 tilts obliquely rearward with the connecting pin 5 as a fulcrum. If the control valve device 21 is switched to the raised position (R) in step 8, the process returns to the start via the return, and the processes in and after step 1 are repeated.

  On the other hand, if it is determined in step 7 that the inclination angle θ of the vessel 3 has reached the upper limit angle θa during loading, that is, it is determined that the inclination angle θ of the vessel 3 is greater than or equal to the upper limit angle θa during loading, the process proceeds to step 9. Then, the control valve device 21 is switched to the neutral position (N). That is, output of the excitation signal from the controller 43 to the electromagnetic valve 36 is stopped, and the electromagnetic valves 36 to 38 are brought to the valve closing position (c). Thereby, the direction control valves 25 and 26 of the control valve device 21 are in the neutral position (N), and supply and discharge of the pressure oil to the bottom side oil chamber 15G and the rod side oil chambers 15E and 15F of the hoist cylinder 15 are stopped. . As a result, the inner cylinder portion 15B and the piston rod 15C of the hoist cylinder 15 can be maintained in the extended state, and the raising operation of the vessel 3 can be stopped. At this time, as shown in FIG. 2, since the vessel 3 is lifted up to the upper limit angle θa at the time of loading, the inclination angle θ of the vessel 3 can be sufficiently increased, and a smooth discharge operation of the earth and sand 4 can be ensured. it can. If the control valve device 21 is switched to the neutral position (N) in step 9, the process returns to the start via return, and the processes in and after step 1 are repeated.

  On the other hand, if “YES” in step 4, that is, if it is determined that the vessel 3 is empty, the process proceeds to step 10, and the upper limit inclination position of the vessel 3, that is, the maximum height of the vessel 3 when empty. The upper limit angle corresponding to is set to the unloaded upper limit angle θb. Next, the process proceeds to step 11, and similarly to step 6, the inclination angle θ of the vessel 3 is read (detected) from the angle sensor 41, and the process proceeds to the next step 12.

  In step 12, it is determined whether or not the inclination angle θ of the vessel 3 detected in step 11 is less than the unloaded upper limit angle θb. If it is determined in step 12 that the inclination angle θ of the vessel 3 is less than the unloaded upper limit angle θb, the process proceeds to step 8 where the direction control valves 25 and 26 of the control valve device 21 are raised to the raised position (R). Switch to. As a result, the hoist cylinder 15 extends, and the vessel 3 tilts obliquely rearward with the connecting pin 5 as a fulcrum. When the control valve device 21 is switched to the raised position (R) in step 8 as described above, the process returns to the start via the return, and the processes in and after step 1 are repeated.

  On the other hand, if it is determined in step 12 that the inclination angle θ of the vessel 3 has reached the empty upper limit angle θb, that is, it is determined that the inclination angle θ of the vessel 3 has become equal to or greater than the empty upper limit angle θb, step 9 Then, the directional control valves 25 and 26 of the control valve device 21 are switched to the neutral position (N), and the extension of the hoist cylinder 15 is stopped. At this time, as shown in FIG. 3, the lifting operation of the vessel 3 stops at the unloaded upper limit angle θb. For this reason, it can suppress that the vessel 3 contacts the ceiling of the building 44, etc., without requiring time for confirmation work and operation becoming complicated. If the control valve device 21 is switched to the neutral position (N) in step 9, the process returns to the start via return, and the processes in and after step 1 are repeated.

  Thus, according to the present embodiment, it is possible to satisfy both the prevention of the vessel 3 from coming into contact with the ceiling of the building 44 and the like, and ensuring the smooth discharge operation of the load (sediment 4).

  That is, for example, when the lifting operation of the vessel 3 is performed in the building 44 for the purpose of maintenance, inspection, maintenance or the like of the dump truck 1, the vessel 3 is empty. In this case, when the vessel 3 reaches the empty upper limit inclination angle θb, the control valve device 21 is switched from the raised position (R) to the neutral position (N) by the processing of step 12 of the controller 43, and the lifting operation of the vessel 3 is performed. Stops. For this reason, when the upper limit inclination angle θb at the time of unloading is set to an angle corresponding to a height lower than the ceiling height of the building 44, for example, it takes time for the confirmation work when the vessel 3 is lifted. It is possible to prevent the vessel 3 from coming into contact with the ceiling of the building 44 or the like without complicated operations. On the other hand, when a load (sediment 4) is loaded on the vessel 3, the vessel 3 can be lifted up to the loading upper limit inclination angle θa that is higher than the empty loading upper limit inclination angle θb. For this reason, the inclination angle θ of the vessel 3 can be sufficiently increased, and a smooth discharge operation can be ensured.

  According to the present embodiment, since the switching position detecting means is constituted by the lever sensor 40, it is possible to stably detect which switching position the control valve device 21 is switched to. In addition, since the load detecting means is constituted by the suspension pressure sensor 42, it is possible to accurately and stably detect the load state of the vessel 3, that is, whether the vessel 3 is loaded or empty. . Furthermore, according to the present embodiment, since the tilt position detecting means is configured by the angle sensor 41, the tilt position of the vessel 3 can be detected with high accuracy and stability as the tilt angle θ.

  Next, FIG. 6 and FIG. 7 show a second embodiment of the present invention. The feature of this embodiment is that, when the vessel is empty and the vehicle body is parked, the control means switches the control valve device from the raised position to the neutral position when the vessel reaches the upper limit tilt position when empty. It is in the configuration. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, 51 is a parking brake switch for operating the parking brake 13, and the parking brake switch 51 is provided, for example, near the driver's seat of the vehicle body 2 (cab 6). The parking brake switch 51 is used to perform ON / OFF operation of braking application and braking cancellation by the parking brake device 13. That is, when the operator turns on the parking brake switch 51, the braking force by the parking brake device 13 can be applied to the rear wheel 9, and when the operator turns off the parking brake switch 51, the braking force of the parking brake device 13 is released. be able to.

  The parking brake switch 51 is connected to a controller 52 described later, and outputs an ON / OFF signal to the controller 52. The parking brake switch 51 constitutes vehicle body detection means for detecting whether or not the vehicle body 2 is parked. The controller 52 determines whether the vehicle is parked based on an ON / OFF signal of the parking brake switch 51.

  52 is a controller as a control means, and the controller 52 is connected to the lever sensor 40, the angle sensor 41, the suspension pressure sensor 42, the parking brake switch 51, and the like on the input side. In the storage unit 52A of the controller 52, a processing program shown in FIG.

  Here, the controller 52 performs the lifting operation of the vessel 3 in accordance with the processing program of FIG. Specifically, the controller 52 uses the detection signal (ON / OFF signal) from the parking brake switch 51 in addition to the detection signals from the lever sensor 40, the angle sensor 41, and the suspension pressure sensor 42 to move the lever position of the operation lever 39A. Is in the raised position (R), the vessel 3 is empty, the vehicle body 2 is parked (the parking brake switch 51 is ON), and the inclination angle θ of the vessel 3 is the upper-limit inclination angle θb when empty. When it is determined that the directional control valve has been reached, the direction control valves 25 and 26 of the control valve device 21 are controlled to be switched from the raised position (R) to the neutral position (N).

  Next, the raising operation process of the vessel 3 by the controller 52 will be described with reference to FIG.

  That is, when the processing operation of FIG. 7 is started by the operation (start) of the engine 9, in step 21, the position signal of the operation lever 39A is read (detected) from the lever sensor 40. Note that the processing from step 21 to step 29 in FIG. 7 is the same as the processing from step 1 to step 9 in FIG. 5 of the first example of the embodiment described above, and detailed description thereof is omitted.

  If “YES” in step 24, that is, if it is determined that the vessel 3 is empty, the process proceeds to step 30, and the signal of the parking brake switch 51 is read (detected). Then, it progresses to step 31 and it is determined whether the parking brake apparatus 13 is turned on. That is, in step 31, it is determined from the signal of the parking brake switch 51 in step 30 whether or not the vehicle body 2 is parked (the parking brake switch 51 is ON).

  If “NO” in step 31, that is, if it is determined that the parking brake device 13 is not ON (OFF), the process proceeds to step 25, where the upper limit inclination position of the vessel 3 is set to the upper limit angle θa during loading. To do. That is, if it is determined in step 31 that the parking brake device 13 is not turned on, it is considered that the lifting operation of the vessel 3 is not performed in the building 44 even if the vessel 3 is empty. Therefore, the upper limit inclination position of the vessel 3 is set to the upper limit angle θa during loading.

  On the other hand, if “YES” in step 31, that is, if it is determined that the parking brake device 13 is turned on, the process proceeds to step 32, where the upper limit inclination position of the vessel 3 is set to the upper limit angle θb when empty. That is, in this case, since the vessel 3 is empty and the parking brake device 13 is turned on, it is considered that the lifting operation of the vessel 3 is performed in the building 44. Therefore, the upper limit inclination position of the vessel 3 is set to the empty upper limit angle θb. Note that the processing from step 32 to step 34 in FIG. 7 is the same as the processing from step 10 to step 12 in FIG. 5 of the first example of the embodiment described above, and detailed description thereof will be omitted.

  In the present embodiment, the operation of raising the vessel 3 is performed by the process shown in FIG. 7 as described above, and the basic action is not different from that of the first embodiment described above.

  In particular, according to the present embodiment, when the vessel 3 reaches the empty upper limit inclination angle θb when the vessel 3 is empty and the vehicle body 2 is parked, the processing of step 34 of the controller 52 is performed. The control valve device 21 is switched from the raised position (R) to the neutral position (N). That is, when the lifting operation of the vessel 3 is performed in the building 44 for the purpose of maintenance, inspection, maintenance, etc. of the dump truck 1, the vessel 3 is empty and the vehicle body 2 is parked. For this reason, when these two conditions are satisfied, the lifting operation of the vessel 3 stops at the unloaded upper limit inclination angle θb. Accordingly, it is possible to achieve both suppression of the vessel 3 coming into contact with the ceiling of the building 44 and the like and ensuring a smooth discharge operation. In addition, when it is determined that the vehicle body 2 is not parked, that is, the parking brake switch 51 (parking brake device 13) is OFF, the vessel 3 is set to the upper limit when empty, even if the vessel 3 is empty. It can be lifted to a position higher than the tilt angle θb (the upper limit tilt angle θa at the time of loading). Thereby, the freedom degree of raising operation of the vessel 3 when the vessel 3 is empty can be increased.

  According to the present embodiment, since the parking detection means is constituted by the parking brake switch 51, it is stably detected whether or not the vehicle body 2 is parked depending on whether or not the parking brake switch 51 is ON. can do.

  Next, FIG. 8 and FIG. 9 show a third embodiment of the present invention. A feature of the present embodiment is that a configuration is provided that includes a vessel lifting limit release switch that enables the vessel to be lifted to the upper limit tilt position during loading even when the vessel is determined to be empty. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, reference numeral 61 denotes a vessel raising restriction release switch provided in the vicinity of the driver's seat in the cab 6. The vessel raising restriction release switch 61 is connected to the controller 62 and is connected to the controller 62 by the operation of the operator. 3 outputs a signal indicating that the upper limit inclination angle 3 is changed. That is, when the operator operates the vessel raising limit release switch 61, a signal (ON signal) indicating that the switch 61 has been operated is output from the vessel raising restriction release switch 61 to the controller 62. Thereby, even when it is determined that the vessel 3 is empty, the controller 62 allows the vessel 3 to be lifted up to the loading upper limit inclination angle θa.

  Here, the vessel raising limit release switch 61 can be constituted by, for example, a momentary switch that is turned on while the operator is pressing and automatically returns to OFF when the operator releases it. Thereby, even when the vessel 3 is empty, when the vessel 3 is lifted up to the upper limit inclination angle θa at the time of loading, the operator keeps the operation lever 39A in the raised position (R) and keeps pushing the vessel raising restriction release switch 61. Thus, the vessel 3 can be lifted up to the upper limit inclination angle θa during loading. Thereby, although the operator does not wish to lift the vessel 3 to the upper limit inclination angle θa at the time of loading, it is possible to suppress the vessel lifting limit release switch 61 from being turned on, and the possibility of an erroneous operation by the operator can be suppressed. Can be reduced.

  Reference numeral 62 denotes a controller as control means. The controller 62 is connected to the lever sensor 40, the angle sensor 41, the suspension pressure sensor 42, the vessel raising limit release switch 61, and the like on the input side. The storage unit 62A of the controller 62 stores the processing program shown in FIG.

  Here, the controller 62 performs the lifting operation of the vessel 3 according to the processing program of FIG. That is, when the processing operation of FIG. 9 is started by the operation (start) of the engine 9, in step 41, the position signal of the operation lever 39A is read (detected) from the lever sensor 40. Note that the processing from step 41 to step 49 in FIG. 9 is the same as the processing from step 1 to step 9 in FIG. 5 of the first example of the embodiment described above, and detailed description thereof is omitted.

  If “YES” in step 44, that is, if it is determined that the vessel 3 is empty, the process proceeds to step 50, and the signal of the vessel raising limit release switch 61 is read (detected). Subsequently, the process proceeds to step 51, where it is determined whether or not the vessel raising limit release switch 61 is turned on.

  If “YES” in step 51, that is, if it is determined that the vessel raising limit release switch 61 is ON, the process proceeds to step 45, where the upper limit inclination position of the vessel 3 is set to the upper limit angle θa during loading. That is, if it is determined in step 51 that the vessel raising limit release switch 61 is turned on, even if the vessel 3 is empty, the operator is higher than the height corresponding to the empty upper limit inclination angle θb. Hope to lift vessel 3 to position. Therefore, the upper limit inclination position of the vessel 3 is set to the upper limit angle θa during loading.

  On the other hand, if it is determined in step 51 that “NO”, that is, the vessel raising limit release switch 61 is not ON (OFF), the process proceeds to step 52 where the upper limit inclination position of the vessel 3 is set to the empty state. Set to the upper limit angle θb. That is, in this case, the vessel 3 is empty and the operator desires to stop the raising operation of the vessel 3 at a height corresponding to the empty upper limit angle θb. It can be considered that the lifting operation of the vessel 3 is performed. Therefore, the upper limit inclination position of the vessel 3 is set to the empty upper limit angle θb. Note that the processing from step 52 to step 54 in FIG. 9 is the same as the processing from step 10 to step 12 in FIG. 5 of the first example of the embodiment described above, and detailed description thereof is omitted.

  In the present embodiment, the raising operation of the vessel 3 is performed by the process shown in FIG. 9 as described above, and the basic action is not different from that of the first embodiment described above.

  In particular, according to the present embodiment, a configuration is provided in which the vessel lifting limit release switch 61 is provided to enable the vessel 3 to be lifted to the upper limit inclination angle θa during loading even when the vessel 3 is empty. For this reason, even when the vessel 3 is empty, for example, when it is necessary to lift the vessel 3 to a position higher than the height corresponding to the empty upper limit inclination angle θb outside the building 44, the vessel raising limit release switch 61 is turned on. By doing so, the vessel 3 can be lifted to a position higher than the height corresponding to the unloaded upper limit inclination angle θb. Thereby, the freedom degree of the raising operation | movement of the vessel 3 can be raised, suppressing that the vessel 3 contacts the ceiling of the building 44, etc.

  Next, FIGS. 10 to 12 show a fourth embodiment of the present invention. The feature of this embodiment is that the tilt position detecting means is constituted by a stroke sensor for detecting the extension length of the hoist cylinder. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 71 denotes a stroke sensor as an inclination position detecting means employed in the present embodiment. The stroke sensor 71 is provided in the hoist cylinder 15 as shown in FIG. 10, for example. The stroke sensor 71 detects the extension length L of the hoist cylinder 15 and outputs a detection signal to the controller 72.

  Reference numeral 72 denotes a controller as control means. As shown in FIG. 11, the input side of the controller 72 is connected to the lever sensor 40, the stroke sensor 71, the suspension pressure sensor 42, and the like. The storage unit 72A of the controller 72 stores a processing program shown in FIG.

  Here, the controller 72 performs the lifting operation of the vessel 3 according to the processing program of FIG. Specifically, when it is determined that the load is loaded on the vessel 3 based on the detection signal of the suspension pressure sensor 42, the controller 72 allows the lifting operation of the vessel 3 up to the upper limit extension length La when loaded. It is configured. On the other hand, when the controller 72 determines that the vessel 3 is empty according to the detection signal of the suspension pressure sensor 42, the controller 72 moves the lifting operation of the vessel 3 to the upper limit extension length Lb during loading, that is, the upper limit extension during loading. It is set as the structure which restrict | limits to the upper limit extension length Lb at the time of empty load in which the height of the vessel 3 becomes lower than length La.

  For this reason, the controller 72 detects that the lever position of the operation lever 39A is in the raised position (R) based on detection signals from the lever sensor 40, the stroke sensor 71, and the suspension pressure sensor 42, and the vessel 3 is empty. When it is determined that the extension length L of the hoist cylinder 15 has reached the empty upper limit extension length Lb, the direction control valves 25 and 26 of the control valve device 21 are moved from the raised position (R) to the neutral position (N Control to switch to). In this case, as shown in FIG. 10, by setting the empty upper limit extension length Lb to an extension length corresponding to a height lower than the ceiling height of the building 44, the lifting operation of the vessel 3 is performed. It is possible to suppress the vessel 3 from coming into contact with the ceiling of the building 44 or the like.

  Next, the raising operation process of the vessel 3 by the controller 72 will be described with reference to FIG.

  That is, when the processing operation of FIG. 12 is started by operating (starting) the engine 9 or the like, in step 61, the position signal of the operation lever 39A is read (detected) from the lever sensor 40. Note that the processing from step 61 to step 64 in FIG. 12 is the same as the processing from step 1 to step 4 in FIG. 5 of the first example of the embodiment described above, and detailed description thereof is omitted.

  If “NO” in step 64, that is, if it is determined that the vessel 3 is not empty (a load is loaded on the vessel 3), the process proceeds to step 65, and the upper limit inclination position of the vessel 3, that is, at the time of loading. The upper limit extension length of the hoist cylinder 15 corresponding to the maximum height of the vessel 3 is set to the upper limit extension length La during loading. Next, the process proceeds to step 66, where the extension length L of the hoist cylinder 15 is read (detected) from the stroke sensor 71, and the process proceeds to the next step 67.

  In step 67, it is determined whether or not the extension length L of the hoist cylinder 15 detected in step 66 is less than the upper limit extension length La during loading. If it is determined in step 67 that the extension length L of the hoist cylinder 15 is less than the upper limit extension length La during loading, the routine proceeds to step 68, where the control valve device 21 is switched to the raised position (R). As a result, the hoist cylinder 15 extends, and the vessel 3 tilts obliquely rearward with the connecting pin 5 as a fulcrum. If the control valve device 21 is switched to the raised position (R) at step 68, the process returns to the start via the return, and the processing after step 1 is repeated.

  On the other hand, in step 67, it is determined that the extension length L of the hoist cylinder 15 has reached the upper limit extension length La when loaded, that is, the extension length L of the hoist cylinder 15 is equal to or greater than the upper limit extension length La when loaded. If YES in step 69, the flow advances to step 69 to switch the control valve device 21 to the neutral position (N). Thereby, the extension of the hoist cylinder 15 is stopped, and the raising operation of the vessel 3 is stopped. At this time, as shown by the phantom line (two-dot chain line) in FIG. 10, the vessel 3 is lifted up to the upper limit extension length La at the time of loading, so that the inclination angle of the vessel 3 can be sufficiently increased, It is possible to secure the discharging operation of (earth and sand 4). If the control valve device 21 is switched to the neutral position (N) at step 69, the process returns to the start via the return, and the processes after step 1 are repeated.

  On the other hand, if “YES” in step 64, that is, if it is determined that the vessel 3 is empty, the process proceeds to step 70, and the upper limit inclination position of the vessel 3, that is, the maximum height of the vessel 3 when empty. The upper limit extension length of the hoist cylinder 15 corresponding to is set to the upper limit extension length Lb when empty. Next, the process proceeds to step 71, and similarly to step 66, the extension length L of the hoist cylinder 15 is read (detected) from the stroke sensor 71, and the process proceeds to the next step 72.

  In step 72, it is determined whether or not the extension length L of the hoist cylinder 15 detected in step 71 is less than the upper limit extension length Lb when empty. If it is determined in step 72 that the extension length L of the hoist cylinder 15 is less than the unloaded upper limit extension length Lb, the process proceeds to step 68 and the control valve device 21 is switched to the raised position (R). As a result, the hoist cylinder 15 extends, and the vessel 3 tilts obliquely rearward with the connecting pin 5 as a fulcrum. When the control valve device 21 is switched to the raised position (R) in step 68 as described above, the process returns to the start via the return, and the processes in and after step 1 are repeated.

  On the other hand, in step 72, the extension length L of the hoist cylinder 15 reaches the upper limit extension length Lb when empty, that is, the extension length L of the hoist cylinder 15 exceeds the upper limit extension length Lb when empty. When it determines, it progresses to step 69, the control valve apparatus 21 is switched to a neutral position (N), and the expansion | extension of the hoist cylinder 15 is stopped. At this time, as shown by a solid line in FIG. 10, the lifting operation of the vessel 3 is stopped when the hoist cylinder 15 reaches the empty upper limit extension length Lb. For this reason, it can suppress that the vessel 3 contacts the ceiling of the building 44, etc., without requiring time for confirmation work and operation becoming complicated.

  The present embodiment performs the raising operation of the vessel 3 using the stroke sensor 71 as described above, and the basic action is not particularly different from that according to the first embodiment described above. In particular, according to the present embodiment, since the tilt position detecting means is constituted by the stroke sensor 71, the tilt position of the vessel 3 can be detected accurately and stably as the extension length L of the hoist cylinder 15. it can.

  In each of the above-described embodiments, the case where the load detection unit is configured by the suspension pressure sensor 42 that detects the internal pressure change of the suspensions 8 and 10 has been described as an example. However, the present invention is not limited to this. For example, the load detection means may be constituted by a hoist cylinder pressure sensor that detects a change in the internal pressure of the hoist cylinder.

  In each of the above-described embodiments, the case where the control valve device 21 is configured using the first and second directional control valves 25 and 26 and the like has been described as an example. However, the present invention is not limited to this, and the control valve device may be configured using, for example, one (single) directional control valve at 4 ports and 4 positions.

  In each of the above-described embodiments, the case where the two-stage hoist cylinder 15 is used has been described as an example. However, the present invention is not limited to this, and for example, a multi-stage hoist cylinder (hydraulic cylinder) of three or more stages or a single-stage hoist cylinder (hydraulic cylinder) may be used.

  Furthermore, in each embodiment mentioned above, the rear-wheel drive type dump truck 1 was mentioned as an example and demonstrated as a transport vehicle. However, the present invention is not limited to this, and may be applied to, for example, a front-wheel drive type or a four-wheel drive type dump truck that drives both front and rear wheels. You may apply to a transport vehicle. Furthermore, the present invention can also be applied to a crawler type transport vehicle.

1 Dump truck (transportation vehicle)
2 Body 3 Vessel 4 Earth and sand (luggage)
15 Hoist cylinder 16 Hydraulic pump 21 Control valve device 40 Lever sensor (switching position detecting means)
41 Angle sensor (tilt position detection means)
42 Suspension pressure sensor (load detection sensor)
43, 52, 62, 72 Controller (control means)
51 Parking brake switch (parking detection means)
61 Vessel raising limit release switch 71 Stroke sensor (tilt position detecting means)

Claims (7)

A self-propelled vehicle body, a vessel provided on the vehicle body that can be tilted and loaded with a load, and a hoist cylinder that is provided to be extendable and expandable between the vessel and the vehicle body to incline the vessel. A hydraulic source that supplies and discharges pressure oil to and from the hoist cylinder, and a control valve device that controls supply and discharge of pressure oil to and from the hoist cylinder,
The control valve device has a lifting position for lifting the vessel by extending the hoist cylinder by supplying and discharging the pressure oil, and a lowering position for lowering the vessel by reducing the hoist cylinder by supplying and discharging the pressure oil. A floating position where the hoist cylinder is contracted by its own weight on the vessel side to allow the vessel to fall by its own weight, and a neutral position where the supply and discharge of the pressure oil is stopped to stop the movement of the hoist cylinder and hold the vessel In a transport vehicle having a plurality of switching positions consisting of
A switching position detecting means for detecting to which position of the plurality of switching positions the control valve device is switched;
Load detection means for detecting the load of the vessel;
A tilt position detecting means for detecting the tilt position of the vessel;
Based on detection signals from the switching position detecting means, the load detecting means and the tilt position detecting means, the control valve device is in the raised position, the vessel is empty, and the tilt position of the vessel is applied to the vessel. Control for switching the control valve device from the raised position to the neutral position when it is determined that the upper limit inclination position when empty is lower than the upper limit inclination position when loading when the load is loaded A transport vehicle characterized by comprising a means. Parking detection means for detecting whether the vehicle body is parked,
The control means includes a detection signal from the parking detection means in addition to detection signals from the switching position detection means, load detection means and tilt position detection means, so that the control valve device is in the raised position, and the vessel is Control for switching the control valve device from the raised position to the neutral position when it is determined that the vehicle body is parked and the vehicle body is parked and the inclined position of the vessel has reached the upper-limit inclined position when empty. The transport vehicle according to claim 1, wherein the transport vehicle is configured to perform.   The transport vehicle according to claim 2, wherein the parking detection means is configured by a parking brake switch that is provided near the driver's seat of the vehicle body and operates a parking brake.   The structure according to claim 1, 2 or 3, further comprising a vessel lifting limit release switch for enabling the vessel to be lifted up to the upper limit tilt position during loading even when the vessel is determined to be empty. The transport vehicle described.   4. The switch position detecting means comprises a lever sensor that detects a lever position of an operation lever device that is provided in the vicinity of a driver's seat of the vehicle body and performs a switching operation of the control valve device. Or the transport vehicle of 4. A suspension for suspending the vehicle body between wheels;
The transport vehicle according to claim 1, 2, 3, 4, or 5, wherein the load detection means is configured by a pressure sensor that detects a change in internal pressure of the suspension due to a change in a load amount.   The said inclination position detection means is comprised by the angle sensor which detects the inclination angle of the vessel with respect to the said vehicle body, or the stroke sensor which detects the expansion | extension length of the said hoist cylinder. Or the transport vehicle of 6.

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