JP6370769B2 - Transportation vehicle - Google Patents

Description

  The present invention relates to a transportation vehicle such as a large dump truck operating in a mine.

  As a transport vehicle, for example, a large dump truck operating in a mine has a vehicle body frame equipped with wheels, a cab is provided at the front side, and ore, rocks, earth and sand etc. A vessel to be loaded is installed. The vessel is connected by a connecting pin at a position on the rear end side of the body frame.

  A hoist cylinder is provided between the vehicle body frame and the vessel. By driving the hoist cylinder, the vessel can be tilted rearward about the connecting pin. Therefore, the attitude of the vessel is controlled by the hoist cylinder expansion / contraction operation to a loading attitude in which the vessel is seated on the vehicle body frame and is in a substantially horizontal state, and a loading / unloading posture in a state where the vessel is raised from the vehicle body frame. The

  The dump truck is used as a transporting means for ore, earth and sand, for example, in a mine. In a mine, a drilling mechanism such as a hydraulic excavator is located at a position to be a drilling site. This excavation site is a dump truck loading place. On the other hand, a sediment disposal site and an ore accumulation site are set at predetermined positions in the mine, and the dump truck is put into the vessel at the excavation site by the operation of the excavation mechanism. Or it operates so that this excavation thing may be conveyed to the unloading place which consists of an ore accumulation place.

  The dump truck is loaded in a state where the vessel is in a substantially horizontal loading posture at the loading location, and travels while maintaining the loading posture to the loading / unloading location. At the loading / unloading location, the hoist cylinder is driven, and the vessel tilts upward. This operation is a raising operation of the vessel, during which the load (excavated material) is discharged from the vessel. When the loading / unloading operation is completed, the hoist cylinder is driven to return the vessel to the loading posture in a substantially horizontal state with respect to the vehicle body frame. The dump truck travels so as to return to the loading place.

  In this way, the dump truck travels back and forth between the loading place and the unloading place, but since the mine is used as an operating field, its traveling path is rough and there are obstacles such as rocks. Objects may be scattered around. Therefore, a large vibration is generated in the entire vehicle when the dump truck is traveling.

  For this reason, vibration during running of the dump truck acts on the connecting portion between the vessel and the vehicle body frame, and the connecting pin and the connecting portion of the connecting pin between the vessel side and the vehicle body frame side are excessive. The impact load will act repeatedly. The vessel is connected to the vehicle body frame at a position on the rear end side, and is in a so-called cantilever state. When in the loading position, the vessel is seated so as to contact the pedestal portion provided on the vehicle body frame, thereby being stable. It is configured to ensure safety.

  Usually, in order to stably hold the vessel in the loading posture, a pressing force is applied to the pedestal, and this pressing force is obtained by the weight of the vessel. However, when the vibration described above becomes large, the vessel may jump up. In a state where the vessel is fully loaded, the pressing force to the pedestal portion is also increased, and the vessel is stably held against the pedestal portion even if there is vibration. However, while traveling on the return path from the loading / unloading place to the loading place, the vessel is in an unloaded state, so the pressing force against the pedestal is insufficient and the stability is impaired. .

  Patented to ensure the stability of this vessel by applying hydraulic pressure in the direction of pressing the vessel against the pedestal using a hoist cylinder at the lowered position of the vessel (ie, loading position) It is disclosed in Document 1.

International Publication No. 2008/099691

  In patent document 1 mentioned above, it is comprised so that the pressing force for hold | maintaining a vessel on a base part may be obtained with the pressure oil by a hydraulic pump. For this purpose, it is necessary to operate the hydraulic pump, but a relief valve is provided in order to prevent the supply pressure to the hoist cylinder from exceeding a predetermined set pressure. Therefore, when pressure is continuously supplied to the hoist cylinder from the hydraulic pump, there is a problem that energy loss increases.

  Therefore, in Patent Document 1, in order to suppress this energy loss to a minimum and to suppress an increase in the oil temperature due to the operation of the relief valve, the hoist cylinder is held in a contracted state (held in a lowered fixed state). Is set under limited conditions. Otherwise, both the bottom and rod oil chambers of the hoist cylinder are set to a floating state where the tank pressure (the pressure equal to that of the hydraulic oil tank) is set substantially. ing. That is, the hydraulic pressure holding force is given to the hoist cylinder only when the vehicle is traveling and the vessel vibrates greatly.

  If comprised as mentioned above, the energy loss in a hydraulic pump can be suppressed, the increase in the fuel consumption of an engine can be suppressed, and it can control that a relief valve opens and closes more than necessary, and oil temperature rises. There is an advantage. However, even in the configuration of Patent Document 1, since the vibration of the vessel is detected and the hoist cylinder is lowered and fixed after the vibration starts, a problem remains in terms of responsiveness.

  The present invention has been made in view of the above points, and an object of the present invention is to increase the responsiveness of the operation of lowering and holding the hoist cylinder in the transportation vehicle.

  In order to achieve the above-described object, a representative invention is provided between a vehicle body frame to which wheels are attached, a vessel that is tiltably attached to the vehicle body frame, and the vehicle body frame and the vessel. A hoist cylinder that tilts the vessel; a hydraulic pump that supplies pressure oil to the hoist cylinder; and an operation of the hoist cylinder provided between the hydraulic pump and the hoist cylinder by switching a flow path of the pressure oil In a transport vehicle, comprising: a control valve that controls a control valve; a pilot pump that supplies a pilot pressure to the control valve; an engine that drives the hydraulic pump and the pilot pump; and a controller. An accumulator for accumulating pressure by supplying pressure oil from a pump; A hydraulic pipe that connects the accumulator and a reduced-side oil chamber that is an oil chamber to which pressure oil is supplied when the hoist cylinder performs a reduction operation among the oil chambers on the head side and the rod side of the cylinder; and the hydraulic pipe An opening / closing valve that opens and closes a road; and a seating detector that detects that the vessel is seated on the vehicle body frame, and the seating detector detects that the vessel is seated on the vehicle body frame. Based on this, the controller outputs an opening operation command to the on-off valve in order to supply the pressure oil accumulated in the accumulator to the reduced-side oil chamber.

  According to the present invention, since the static pressure of the accumulator can be guided to the hoist cylinder, the responsiveness of the operation of lowering and holding the hoist cylinder in a fixed state is increased. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a side view of the dump truck for mines which shows an example of the vehicle for conveyance. It is composition explanatory drawing which shows the operation control mechanism of a dump truck. It is a hydraulic circuit diagram of a dump truck. It is a figure which shows the modification of the hydraulic circuit of a dump truck. It is operation | movement explanatory drawing at the time of applying the pressing force to the base part of a vessel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a configuration of a mine dump truck 1 as an example of a transport vehicle. In addition, even if it is other than this as a transport vehicle, it can apply to the thing provided with the vessel which accommodates various loads in a vehicle body frame so that inclination (undulation operation) was possible.

  The dump truck 1 has a body frame 2, and wheels as traveling means, that is, left and right front wheels 3 and rear wheels 4 are attached to the body frame 2. An engine 5 is used as a power source, and the engine 5 is attached to the vehicle body frame 2. Reference numeral 6 denotes a driver's cab in which an operator who operates the dump truck 1 is boarded. The driver's cab 6 is provided at a front position above the body frame 2.

  The vehicle body frame 2 is provided with a vessel 7 constituting a cargo bed. The vessel 7 has a rear end portion connected to the vehicle body frame 2 by a connection pin 8, and the vehicle body frame 2 is vertically moved around the connection pin 8 as indicated by an arrow in the drawing. Can be rotated. As a result, the vessel 7 tilts backward from the loading posture substantially parallel to the vehicle body frame 2 and can be displaced until it reaches a loading / unloading posture inclined at a predetermined angle. In this way, the hoist cylinder 9 is interposed between the vehicle body frame 2 and the vessel 7 in order to drive the vessel 7 to tilt. A pair of hoist cylinders 9 is provided. When the hoist cylinder 9 is extended, the vessel 7 performs a raising operation, and when the hoist cylinder 9 is contracted, the vessel 7 performs a lowering operation.

  The vessel 7 is configured to be loaded with earth and sand, crushed stone, and the like, and for this purpose, is a container opened upward. Further, a head guard 7a is connected to the front end portion of the vessel 7, and when the vessel 7 is in a lowered loading posture, the head guard 7a covers the upper portion of the operator cab 6 so as to cover this operator cab. Safety protection of the operator etc. who operate within 6 is achieved. Further, when the vessel 7 is in the loading posture, it is seated so as to abut on the pedestal portion 10 provided in the vehicle body frame 2. Furthermore, in the figure, 11 is a suspension cylinder.

  A mechanism for controlling the attitude of the vessel 7 will be described with reference to FIG. The vessel 7 is operated by an operating device 20 provided in the cab 6. The operating device 20 has an operating lever 21, and by operating the operating lever 21, the vessel 7 is tilted with respect to the vehicle body frame 2 around the connecting pin 8. The operation lever 21 has four positions, the first position is the vessel lowered position PD, the second position is the floating position FL, the third position is the neutral position NP, and the fourth position is the vessel raised position PU. is there.

  As described above, it is the hoist cylinder 9 that tilts and displaces the vessel 7, and as shown in FIG. 3, the hoist cylinder 9 has a piston rod in the cylinder tube 9a as in the case of a general cylinder. A piston 9c connected to 9b is slidably provided, and the inside of the cylinder tube 9a is partitioned into two oil chambers A and B by the piston 9c. When pressure oil is introduced into the head-side oil chamber A and the bottom-side oil chamber B is set to the tank pressure, the hoist cylinder 9 is extended, and therefore the head-side oil chamber A is an extension-side oil chamber. . On the other hand, when the pressure oil is introduced into the oil chamber B on the bottom side and the oil chamber A on the head side is set to the tank pressure, the hoist cylinder 9 is reduced. Therefore, the bottom side oil chamber B is a reduction side oil chamber.

  At the vessel raising position PU, which is the fourth position of the operating lever 21, pressure is introduced into the oil chamber A of the hoist cylinder 9 and the oil chamber B is held at the tank pressure, so that the hoist cylinder 9 extends. Further, at the vessel lowering position PD which is the first position, pressure is supplied to the oil chamber B, the oil chamber A is held at the tank pressure, and the hoist cylinder 9 is contracted. Further, at the floating position FL of the second position, the oil chamber A and the oil chamber B are substantially held at the tank pressure, and the vessel 7 is held in a state of being seated on the pedestal portion 10 by its own weight. Further, when the neutral position NP, which is the third position, is reached, both the oil chamber A and the oil chamber B are held in a locked state.

  The above operation by the operating lever 21 in the operating device 20 is input as a control signal to the controller 23 via the output unit 22, and drive control of the hoist cylinder 9 is performed based on the output signal of the controller 23.

  Next, FIG. 3 shows a configuration of a hydraulic circuit for driving the hoist cylinder 9. In the figure, 30 is a hydraulic pump for supplying pressure oil to the hoist cylinder 9. The hydraulic pump 30 is driven by the engine 5 together with a pilot pump 31 and the like that supply pressure oil to other hydraulic circuits. Two control valves 33 and 34 are interposed between the hydraulic pump 30 and the hydraulic oil tank 32 and the hoist cylinder 9. These control valves 33 and 34 are for controlling the operation of the hoist cylinder 9 by switching the supply of pressure oil to the hoist cylinder 9, and the switching operation is performed based on a signal from the controller 23.

  In the illustrated hydraulic circuit, each of the control valves 33 and 34 has three positions. When the operation lever 21 is in the neutral position NP, the control valves 33 and 34 are always in the central neutral position. When the operation lever 21 is tilted and operated from the neutral position, the control valves 33 and 34 are switched to one of the left and right switching positions by a hydraulic pilot signal. The output signal of the controller 23 is an electrical signal. An electromagnetic proportional valve unit 35 is attached to a flow path connecting the pilot pump 31 and the pilot parts of the control valves 33 and 34, and the electromagnetic proportional valve unit 35 is activated by receiving an electric signal from the controller 23. Pilot pressure from the pilot pump 31 is supplied to and discharged from each pilot section. The pilot pressure from the pilot pump 31 is adjusted by a pressure reducing valve (pressure adjusting device) 53 described later.

  The electromagnetic proportional valve unit 35 is composed of three electromagnetic proportional valves 35PD, 35FL, and 35PU. When the operation lever 21 is in the neutral position at all times, the output side of each electromagnetic proportional valve 35PD, 35FL, and 35PU. Is connected to the hydraulic oil tank 32. When a control signal is input from the controller 23, one of the electromagnetic proportional valves 35PD, 35FL or 35PU is switched to the switching position, and either the left or right of the control valves 33, 34 is switched. The pilot pressure is supplied to the pilot portion of the control valve 33 so that the control valves 33 and 34 are switched from the neutral position to either the left or right switching position.

  When the operating lever 21 in the neutral position is tilted to the right, the vessel raising position PU is reached. As a result, the electromagnetic proportional valve 35PU is switched, the pilot pressure is supplied to the left pilot portion of the control valves 33 and 34, and the control valves 33 and 34 in the neutral position are switched to the left switching position. become. As a result, the oil chamber A on the extension side of the hoist cylinder 9 is connected to the hydraulic pump 30, and the oil chamber B on the reduction side is connected to the hydraulic oil tank 32. As a result, the hoist cylinder 9 extends and the vessel 7 moves up. In FIG. 3, reference numeral 36 denotes a relief valve for protecting the control valves 33 and 34 from excessive pressure. Reference numerals 37 and 38 denote make-up check valves.

  When the operation lever 21 is tilted to the left and operated to the vessel lowering position PD through the floating position FL, the electromagnetic proportional valve 35PD is switched, and the control valve 34 is switched from the neutral position to the right switching position. Change. As a result, the pressure of the hydraulic pump 30 acts on the oil chamber B on the side where the hoist cylinder 9 is contracted, and the oil chamber A on the side where the hoist cylinder 9 expands is connected to the hydraulic oil tank 32. As a result, the hoist cylinder 9 is reduced, and the vessel 7 performs the lowering operation. At this time, the control valve 33 is held in the neutral position.

  When the operation lever 21 is operated so as to reach the floating position FL between the neutral position NP and the vessel lowering position PD, the electromagnetic proportional valve 35FL is switched. In this case, only the control valve 33 is switched to the switching position on the right side in the figure. As a result, both the oil chambers A and B of the hoist cylinder 9 are connected to the hydraulic oil tank 32, and the hydraulic pump 30. The pressure oil from the refrigerant flows back to the hydraulic oil tank 32, and the hoist cylinder 9 is reduced by the weight of the vessel 7, and the vessel 7 is seated on the pedestal 10 and stably held.

  Next, when the operation lever 21 is switched to the neutral position NP in the vertical state, the control valves 33 and 34 that perform control for driving the hoist cylinder 9 return to the neutral position, and the hoist cylinder 9 is in a contracted state due to the weight of the vessel 7. Is held stably. This state is the loading posture of the vessel 7, and it becomes possible to load loads such as earth and sand on the dump truck 1 without applying a load to the hoist cylinder 9, and ore and earth and sand are mined at the loading place. , Loaded on the vessel 7 of the dump truck 1.

  When the loading on the dump truck 1 is completed, the dump truck 1 is moved and transported to a loading / unloading place such as an ore accumulation place. At this time, the vessel 7 is kept in the loading posture.

  When the dump truck 1 is carried to a predetermined position in the loading / unloading place, the operation lever 21 in the operation device 20 is operated, and the electromagnetic proportional valve 35PU is switched based on the control signal from the controller 23 to switch from the hydraulic pump 30. The pilot pressure is supplied to the hydraulic pilot section on the left side of the control valves 33 and 34. As a result, the control valves 33 and 34 are switched, the pressure oil from the hydraulic pump 30 is supplied to the oil chamber A of the hoist cylinder 9, and the oil chamber B is connected to the hydraulic oil tank 32. Will stretch. Accordingly, the vessel 7 assumes a loading / unloading posture in which the vessel 7 tilts backward about the connecting pin 8 and the load in the vessel 7 is discharged backward.

  As long as the operation lever 21 maintains the vessel raising position PU, the hoist cylinder 9 continues to extend and the vessel 7 continues to tilt upward, but the center of gravity of the entire dump truck 1 moves backward. There is a risk of falling. Therefore, in order to ensure safety, the highest raised position is regulated by, for example, providing a stopper.

  When the load is completely discharged from the vessel 7, the operation lever 21 is switched from the vessel raising position PU to the floating position FL. As a result, the switching position on the right side of the control valve 33 is switched. Further, the control valve 34 returns to the neutral position. Accordingly, the oil chamber A side and the oil chamber B side of the hoist cylinder 9 are connected to the hydraulic oil tank 32, the hoist cylinder 9 is contracted, and the vessel 7 is tilted and displaced in the horizontal direction.

  When the operating lever 21 is switched to the neutral position NP while the vessel 7 is operating in the raising or lowering direction by setting the vessel raising position PU or the floating position FL, the control valves 33 and 34 are Switch to neutral position. In this neutral position, both the oil chambers A and B of the hoist cylinder 9 are shut off from both the hydraulic pump 30 and the hydraulic oil tank 32 to be locked, and the vessel 7 is held at that position.

  With the configuration as described above, the attitude control of the vessel 7 is performed. By setting the operation lever 21 to the floating position FL, the vessel 7 can be seated on the pedestal portion 10 by its own weight and held in the loaded posture. As a result, excavation is performed with a hydraulic excavator, and the excavated material is thrown into the vessel 7. This is the loading operation to the dump truck 1.

  When a predetermined amount of earth or sand or ore is thrown into the vessel 7 of the dump truck 1 and becomes full, the vessel 7 keeps the loading posture and the dump truck 1 travels to the loading / unloading place. When the dump truck 1 is arranged at a predetermined position in the loading / unloading place, the earth and sand are unloaded from the vessel 7. This earth and sand loading and unloading work is performed by tilting the operation lever 21 to the vessel raising position PU. As a result, the hoist cylinder 9 extends, the vessel 7 tilts upward about the connecting pin 8, and the earth and sand in the vessel 7 is discharged rearward. At this time, the dump truck 1 is advanced to facilitate the discharge of the load from the vessel 7. Further, the vessel 7 is held at a desired angular position by switching the operation lever 21 to the neutral position NP in the middle of the vessel raising state. Thereby, the discharge speed of the earth and sand from the vessel 7 can be adjusted.

  When the discharge of earth and sand from the vessel 7 is completed, the operation lever 21 is tilted to the floating position FL, so that the vessel 7 contracts the hoist cylinder 9 by its own weight, and the vessel 7 is lowered. As a result, the seat 7 returns to the seated state in which the bottom surface of the vessel 7 is in contact with the pedestal 10 provided on the body frame 2. As described above, the center of gravity of the vessel 7 connected to the vehicle body frame 2 by the connecting pin 8 in the rear position is in a state of acting downward, so that the vessel 7 returns to the horizontal state by the action of gravity.

  By operating the operating lever 21 as described above, the raising and lowering operation of the vessel 7 is performed. In principle, the vessel 7 is moved up and down only when the load is loaded and unloaded. At other times, the vessel 7 is held in a state of being seated on the pedestal portion 10 including when the dump truck 1 is traveling. The vessel 7 is connected to the connecting pin 8 at a position on the rear side, and the weight on the front side is large, so that the position of the center of gravity is located in front of the connecting position to the connecting pin 8. Therefore, even if the operating lever 21 is set to the floating position FL, it is held in a state where it is seated and abutted on the pedestal portion 10 unless a special external force is applied to the vessel 7. Further, if the operation lever 21 is set to the vessel lowering position PD, the vessel 7 is pressed by the pedestal portion 10 and thus becomes more stable.

  Incidentally, a relief valve 36 is provided at a position downstream of the control valve 33 in the high-pressure oil passage 40 from the hydraulic pump 30, and has a relief function for releasing the pressure to the hydraulic oil tank 32 when the pressure exceeds the relief set pressure. It is something that demonstrates. The relief valve 36 functions both during the raising operation of the vessel 7 and during the lowering operation, but is adjusted to have a high set pressure during the vessel raising operation and a low set pressure during the vessel lowering operation. .

  Now, when the operation lever 21 is set to the vessel lowering position PD, the control valve 34 is switched to the left switching position in the figure, and the pressure from the hydraulic pump 30 is supplied to the oil chamber B of the hoist cylinder 9. The hoist cylinder 9 is reduced, and the vessel 7 is lowered. Then, after the vessel 7 contacts the pedestal 10, the hoist cylinder 9 does not perform any further reduction operation. Thereafter, when the operation lever 21 holds the vessel lowering position PD, the relief valve 36 is opened, and the pressure from the hydraulic pump 30 is returned to the hydraulic oil tank 32. Here, when the vessel is lowered, the set pressure of the relief valve 36 is low. However, when the operation lever 21 remains at the vessel lowered position PD, the hydraulic pump 30 is subjected to a load corresponding to the set pressure of the relief valve 36. Will be held in a state. For this reason, when the vessel 7 is seated on the pedestal portion 10, it is desirable to quickly operate the operation lever 21 to temporarily return to the neutral position NP.

  The control lever 21 is set to the floating position FL except when the vessel 7 is moved up and down. As a result, the hydraulic pump 30 is connected to the hydraulic oil tank 32 without passing through the relief valve. As a result, the hydraulic pump 30 enters a no-load state, so that energy consumption can be saved and the relief valve 36 does not operate, so that an increase in the hydraulic oil temperature is suppressed.

  Here, since the dump truck 1 travels on rough terrain such as a mine, a large vibration is generated in the entire vehicle during traveling. Since the vessel 7 is connected to the vehicle body frame 2 in a cantilever manner by the connecting pin 8, when the vessel 7 bounces up and down due to vibration of the entire vehicle, repeated severe collisions with the base portion 10 are repeated. As a result, there is a possibility that the vessel 7 and the connecting pin 8 and further the mounting bracket 12 of the connecting pin 8 may be damaged. In order to prevent this, it is necessary to always bring the vessel 7 into contact with the pedestal portion 10 and stabilize it so that the vessel 7 is not separated from the pedestal portion 10 even when the vehicle vibrates.

  In a loaded state in which earth and sand are loaded on the vessel 7, the vessel 7 is pressed against the pedestal 10 by the weight of the loaded item, so that the vessel is loaded with the weight of the load while the dump truck 1 is traveling on rough terrain. 7 is held in contact with the pedestal 10 and is stably held in the seated state. However, when the load such as earth and sand is discharged and the vessel 7 becomes empty and the weight of the vessel 7 is reduced, the pressing force of the vessel 7 on the pedestal portion 10 is reduced and the stability is lost, and the dump truck 1 is running. When a large vibration occurs, the vessel 7 comes in contact with and separates from the pedestal portion 10 and the impact is repeatedly generated.

  If the vessel 7 can be pressed against the pedestal 10 using the hydraulic pressure of the hoist cylinder 9, the vessel 7 will repeatedly collide with the pedestal 10 even if vibration occurs when the dump truck 1 runs on rough terrain. Will not occur. Therefore, if the operation lever 21 is held at the vessel lowered position PD, the vessel 7 can be brought into close contact with the pedestal portion 10. However, as described above, from the viewpoint of reducing energy consumption and preventing the hydraulic oil temperature from rising, it is not preferable to hold the operation lever 21 at the vessel lowering position PD except when the vessel 7 is raised or lowered.

  Incidentally, in the hydraulic circuit of FIG. 3, an accumulator 50 is provided. The accumulator 50 is connected to the pilot pump 31 by a hydraulic pipe 51. When pressure oil is supplied from the pilot pump 31, the accumulator 50 accumulates a predetermined pressure therein. The hydraulic pipe 51 is also connected to a hydraulic device or the like provided on the downstream side of the accumulator 50. In the present embodiment, the pressure of the accumulator 50 is guided to the hoist cylinder 9 so that the hoist cylinder 9 is held in a contracted state and the state where the vessel 7 is seated on the pedestal portion 10 is maintained.

  For this purpose, there is a pressure supply pipe 52 that branches from a position on the upstream side of the connecting part of the hydraulic pipe 51 to the accumulator 50, that is, on the connecting side to the pilot pump 31, and is connected to the oil chamber B on the rod side of the hoist cylinder 9. The pressure supply pipe 52 is provided with a pressure reducing valve 53 and an electromagnetic open / close valve (open / close valve) 54. Therefore, when the hoist cylinder 9 is applied with oil pressure in the reduction direction and the vessel 7 is pressed against the pedestal 10, the pressure stored in the accumulator 50 is reduced by the pressure reducing valve 53, and the dump truck 1 is rough. During traveling, the pressure is adjusted so that a pressing force necessary to obtain the stability of the vessel 7 is applied. In addition, it is good also as a structure which accumulates the pressure oil from the hydraulic pump 30 with the accumulator 50 instead of the pilot pump 31. FIG.

  Here, since the pressure of the accumulator 50 is reduced by the pressure reducing valve 53 as the oil pressure applied to the hoist cylinder 9, the downstream side of the pressure reducing valve 53 is substantially in a static pressure state. That is, in the normal state, it is not necessary to set the pilot pump 31 to the constantly driven state in order to maintain the hoist cylinder 9 in a predetermined pressure state.

  In FIG. 3, the connection position between the hydraulic pipe 51 and the pressure supply pipe 52 is the upstream side of the connection portion of the accumulator 50, that is, the position between the pilot pump 31 and the accumulator 50. As described above, it can be connected to the downstream side of the accumulator 50. As to which position is desirable, the circuit design may be performed in consideration of whether the pressure fluctuation is greater in the front or back of the accumulator 50. The pilot pump 31 supplies pressure to the electromagnetic proportional valves 35PD, 35PU, and 35FL constituting the electromagnetic proportional valve unit 35. Therefore, the pressure reducing valve 53A on the connection side to the electromagnetic proportional valve unit 35 and the hoist are provided. It is desirable to divide into the pressure reducing valve 53B on the connection side to the electromagnetic opening / closing valve 54 connected to the cylinder 9.

  The pressure supply pipe 52 is provided with an electromagnetic on-off valve 54. When the electromagnetic on-off valve 54 is closed, the hoist cylinder 9 exhibits a holding force via the pressure supply pipe 52. Is not supplied. Then, when the electromagnetic opening / closing valve 54 is opened, pressure is supplied to the hoist cylinder 9, and the vessel 7 is pressed against the pedestal portion 10 by this pressure, and a stable vessel seating state is obtained. The vessel seating state is required when the dump truck 1 is traveling in a light weight state such as when the vessel 7 is empty. Other than this, the holding force by the accumulator 50 is not applied to the hoist cylinder 9. Moreover, the opening / closing of the electromagnetic opening / closing valve 54 is automatically controlled rather than being brought into the vessel holding state by manual operation.

  Here, the dump truck 1 includes a controller 23 as shown in FIG. 2, and the opening / closing operation of the electromagnetic opening / closing valve 54 is performed based on a signal from the controller 23. For this purpose, a seating sensor (sitting detector) 13 for detecting whether or not the vessel 7 is in contact with the pedestal portion 10 is interposed between the vehicle body frame 2 and the vessel 7, and is attached to the suspension cylinder 11. Includes a pressure sensor (state detector) 14 for detecting the weight of the vessel 7. Further, the rear wheel 4 is provided with a pickup sensor (speed detector) 15.

  With the configuration described above, the controller 23 determines whether or not the operating lever 21 configuring the operating device 20 is in the floating position FL as shown in FIG. 5 (step 1). If the seating sensor 13 is in the on state with the operation lever 21 in the floating position FL (step 2), it is detected that the vessel 7 is seated on the pedestal portion 10 in the horizontal state. It will be. In this state, it is determined whether or not the pressure sensor 14 provided in the suspension cylinder 11 is lower than a predetermined reference value (step 3).

  The weight of the vessel 7 changes depending on the presence / absence of the load and the amount of the load. If the weight of the vessel 7 is large, the vessel 7 is held in a state of being stably seated on the pedestal 10 by its own weight. Accordingly, the vessel 7 is reliably seated on the pedestal 10 even while the dump truck 1 is traveling on rough terrain. If the vessel 7 is in an empty state or a state close to an empty state, since the weight of the vessel 7 is small, the vessel 7 becomes unstable and the seating on the pedestal portion 10 is not stable.

  Further, it is determined whether or not the dump truck 1 is traveling based on the signal from the pickup sensor 15 (step 4). Note that the pickup sensor 15 can determine whether or not the dump truck 1 is traveling at a predetermined set speed, rather than whether or not the dump truck 1 is traveling. In other words, when the traveling speed is low, the vibration in the vehicle body is not large, so it may be unnecessary to open the electromagnetic on-off valve 54. Even when the vessel 7 is in an empty state, vibration or the like does not occur while the dump truck 1 is stopped.

  If the above conditions are satisfied, there is a problem in the stability of the vessel 7, and the controller 23 outputs an opening operation command to the electromagnetic on-off valve 54, opens the electromagnetic on-off valve 54 (step 5), and the hoist The pressure of the accumulator 50 is applied to the oil chamber B of the cylinder 9, and the pressing force to the pedestal portion 10 of the vessel 7 is applied to stabilize the vessel 7. Here, when the pressing force by the hoist cylinder 9 is applied, the hoist cylinder 9 is stably held by applying a substantially static pressure such as the pressure of the accumulator 50. Since the static pressure of the accumulator 50 can be applied to the hoist cylinder 9, the vessel 7 can be stably held on the pedestal portion 10 in a short time. That is, according to the present embodiment, the responsiveness of the operation of lowering and holding the hoist cylinder 9 in a fixed state is high. In addition, since it is not necessary to drive the pilot pump 31 at all times, energy loss can be suppressed, thereby contributing to improvement in fuel efficiency of the engine 5.

  On the other hand, if any one of the above-mentioned conditions is missing, the electromagnetic on-off valve 54 is kept closed (step 6). As a result, the pilot pump 31 is maintained in a state where no extra load is applied.

  In addition to the configuration of the above embodiment, an inclination angle sensor for detecting the inclination angle of the dump truck 1 is provided, and the opening operation of the electromagnetic on-off valve 54 is controlled by the inclination angle of the vehicle body frame 2. May be. If it does in this way, according to road surface condition, vessel 7 can be held to pedestal part 10 more stably.

DESCRIPTION OF SYMBOLS 1 Dump truck 2 Body frame 5 Engine 7 Vessel 8 Connecting pin 9 Hoist cylinder 10 Base part 11 Suspension cylinder 13 Seat sensor (seat detector)
14 Pressure sensor (status detector)
15 Pickup sensor (speed detector)
23 Controller 30 Hydraulic pump 31 Pilot pump 50 Accumulator 52 Pressure supply piping (hydraulic conduit)
53, 53A, 53B Pressure reducing valve (pressure adjusting valve)
54 Electromagnetic on-off valve (on-off valve)
A Head side oil chamber B Bottom side oil chamber (reduction side oil chamber)

Claims (4)

A vehicle body frame to which wheels are attached, a vessel attached to the vehicle body frame so as to be tiltable, a hoist cylinder provided between the vehicle body frame and the vessel and tilting the vessel, and pressure oil to the hoist cylinder Is provided between the hydraulic pump and the hoist cylinder, the control valve is configured to control the operation of the hoist cylinder by switching the flow path of the pressure oil, and the pilot pressure is supplied to the control valve. In a transport vehicle comprising a pilot pump, the hydraulic pump and an engine that drives the pilot pump, and a controller,
An accumulator that accumulates pressure by supplying pressure oil from the hydraulic pump or the pilot pump;
Of the oil chambers on the head side and rod side of the hoist cylinder, a hydraulic line that connects the reduced-side oil chamber that is an oil chamber to which pressure oil is supplied when the hoist cylinder is contracted, and the accumulator;
An on-off valve for opening and closing the hydraulic line;
A seating detector for detecting that the vessel is seated on the vehicle body frame,
When the seating detector detects that the vessel is seated on the vehicle body frame, the controller supplies pressure oil accumulated in the accumulator to the reduced-side oil chamber. A transport vehicle characterized by outputting an opening operation command to the on-off valve. In claim 1,
A transporting vehicle, further comprising a pressure adjusting valve provided in the hydraulic line and configured to adjust a pressure of pressure oil supplied from the accumulator to the reduced-side oil chamber. In claim 1 or 2,
A state detector for detecting a load state of the vessel;
The transport vehicle according to claim 1, wherein the controller outputs an opening operation command to the on-off valve based on the fact that the state detector detects that the vessel is in an empty state. In claim 1 or 2,
A speed detector for detecting the speed of the wheel;
The transport vehicle, wherein the controller outputs an opening operation command to the on-off valve when the speed of the wheel detected by the speed detector is a predetermined speed.