JP2016105001A - Industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrial vehicle capable of improving fuel consumption of an engine in a standby state.SOLUTION: An industrial vehicle 1A includes an engine 11 of which output is utilized in traveling, and a hydraulic pump 21 which is driven by the engine 11 and of which a tilt angle is changed by a regulator 22. A circulation line 31 is extended from the hydraulic pump 21 to a tank 32. A pilot line 51 connecting a part between a work circuit 34 and a throttle 33 in the circulation line 31 and the regulator 22 is provided with a switch valve 52. The switch valve 52 is connected to a pressure source line 53, and positioned at a first position for guiding a negative control pressure Pn to the regulator 22 in a travellable time, and at a second position to guide the pressure of the pressure source line 53 to the regulator 22 in a standby state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an industrial vehicle such as a wheel loader.

  Industrial vehicles such as wheel loaders, excavator loaders, and forklifts include traveling wheels and working hydraulic actuators. In such an industrial vehicle, the output of the engine is used for traveling and driving a hydraulic pump.

  For example, Patent Literature 1 discloses a hydraulic drive system mounted on a wheel loader. This hydraulic drive system includes a hydraulic pump driven by an engine, and a cargo handling circuit (working circuit) for driving the boom cylinder and the bucket cylinder. The hydraulic pump is a variable displacement pump whose tilt angle is changed by a regulator.

  In the hydraulic drive system disclosed in Patent Document 1, the tilt angle of the hydraulic pump is adjusted by negative control. Specifically, a circulation line constituting the center bypass line of the cargo handling circuit extends from the hydraulic pump to the tank, and the throttle is provided downstream of the cargo handling circuit. A negative control pressure Pn, which is a pressure upstream of the throttle in the circulation line, is introduced to the regulator through the pilot line.

JP 2014-101940 A

  By the way, in the industrial vehicle in which the output of the engine is used for traveling, the rotational speed of the engine varies greatly depending on the traveling state (for example, 900 to 2300 rpm). When the engine speed varies, the negative control pressure Pn also varies. That is, while the vehicle is running, the negative control pressure Pn increases because the engine speed is high. As a result, when the hydraulic actuator is not operating, the discharge flow rate of the hydraulic pump is minimized. On the other hand, when the vehicle is not traveling, the negative control pressure Pn is low because the engine speed is small. As a result, the discharge flow rate of the hydraulic pump cannot be minimized even when the hydraulic actuator is not operating. Therefore, even in a standby state where the vehicle does not travel, a certain amount of torque is required to drive the hydraulic pump, and the fuel consumption in the engine increases.

  Accordingly, an object of the present invention is to provide an industrial vehicle that can improve the fuel efficiency of an engine in a standby state.

  In order to solve the above problems, an industrial vehicle according to the present invention includes an engine whose output is used for traveling, a hydraulic pump driven by the engine and whose tilt angle is changed by a regulator, and the hydraulic pump. A circulation line constituting a center bypass line of a work circuit for driving a working hydraulic actuator extending to the tank, wherein the circulation line is provided with a throttle on the downstream side of the work circuit; A pilot line connecting a portion between the work circuit and the throttle and the regulator; and a switching valve provided in the pilot line, the pressure of which is equal to or higher than a reference pressure that minimizes a tilt angle of the main pump. A pressure source line is connected, and when traveling is possible, the pressure upstream of the throttle in the circulation line is guided to the regulator. Located in the position, and a cutting switched valve in the second position leading to the regulator the pressure of the pressure source line during the standby state, characterized in that.

  According to the above configuration, the negative control pressure Pn, which is the pressure upstream of the throttle in the circulation line, varies depending on the engine speed, but when the switching valve is switched to the second position during the standby state, the negative control pressure Pn The pressure of the pressure source line is led to the regulator instead of the control pressure Pn. Thereby, even in the standby state, when the hydraulic actuator is not operating, the discharge flow rate of the hydraulic pump can be minimized. As a result, the fuel efficiency of the engine in the standby state can be improved.

  The switching valve may be located at the first position when a parking brake switch is off, and may be switched to the second position when the parking brake switch is on. According to this configuration, the switching valve can always be maintained at the second position during the parking state (one form of the standby state). In addition, since the switching valve can be automatically switched to the second position using the electrical signal of the parking brake switch, there is no need to make a special determination using the control device.

  The industrial vehicle further includes a control device that controls the switching valve, and the control device satisfies both a first condition in which the traveling lever is positioned at the neutral position and a second condition in which the traveling brake is operated. The switching valve may be switched from the first position to the second position when a certain time has elapsed from the first position. According to this configuration, the switching valve is switched to the second position even when the vehicle is stopped for a short time (one form of standby state) in which travel is interrupted, so that the effect of improving the fuel consumption of the engine can be obtained in a wide range of standby state. be able to.

  The hydraulic pump is a main pump, and the industrial vehicle further includes an accessory pump driven by the engine, and the pressure source line is connected to a supply line that guides hydraulic oil discharged from the accessory pump. It may be. According to this configuration, the discharge pressure of the accessory pump can be rationally used as a pressure source.

  The supply line connects a main flow path connecting the accessory pump to an unloader valve, a first branch connecting the unloader valve to a travel brake and a parking brake, and connecting the unloader valve to a fan circuit for cooling the engine. The unloader valve includes a second tributary, and the unloader valve preferentially supplies hydraulic oil to the first tributary when the pressure of the first tributary falls below a set pressure, and the pressure of the first tributary exceeds the set pressure. In this case, hydraulic oil is supplied to the second branch, and the first branch is provided with a check valve and an accumulator in order from the upstream side. The pressure source line may be connected to a downstream portion of the stop valve. According to this configuration, the pressure of the first tributary, which is the pressure for the traveling brake and the parking brake, is kept substantially constant, so that this stable pressure can be guided to the regulator during the standby state.

  Alternatively, the pressure source line may be connected to an upstream portion of the work circuit in the circulation line, and the pressure source line may be provided with a check valve and an accumulator in order from the upstream side. According to this configuration, since the pressure on the downstream side of the check valve in the pressure source line is kept substantially constant, this stable pressure can be guided to the regulator during the standby state.

  According to the present invention, the fuel efficiency of the engine in the standby state can be improved.

It is a figure showing typically a schematic structure of an industrial vehicle concerning a 1st embodiment of the present invention. It is a side view of the industrial vehicle shown in FIG. It is a schematic block diagram of a cargo handling circuit. It is a figure which shows typically schematic structure of the industrial vehicle of the 1st modification of 1st Embodiment. It is a figure which shows typically schematic structure of the industrial vehicle of the 2nd modification of 1st Embodiment. It is a figure which shows typically schematic structure of the industrial vehicle which concerns on 2nd Embodiment of this invention. It is a figure which shows typically schematic structure of the industrial vehicle which concerns on 3rd Embodiment of this invention. It is a figure which shows typically schematic structure of the industrial vehicle which concerns on 4th Embodiment of this invention.

(First embodiment)
FIG. 2 shows an industrial vehicle 1A according to the first embodiment of the present invention, and FIG. 1 schematically shows a schematic configuration of the industrial vehicle 1A. Although the industrial vehicle 1A shown in FIG. 2 is a wheel loader, the present invention can also be applied to industrial vehicles such as an excavator loader and a forklift.

  As shown in FIG. 2, the industrial vehicle 1A includes a front vehicle body 10A and a rear vehicle body 10B that are connected to each other so as to be swingable in the horizontal direction. A front wheel 15A is attached to the front vehicle body 10A, and a rear wheel 15B is attached to the rear vehicle body 10B. Although not shown, a pair of left and right steering cylinders are disposed between the front vehicle body 10A and the rear vehicle body 10B.

  The rear vehicle body 10B is provided with a cab 17 and an engine 11 is mounted. The boom 18 is connected to the front vehicle body 10A so as to be swingable in the vertical direction, and the bucket 19 is connected to the tip of the boom 18 so as to be swingable in the vertical direction. The front vehicle body 10A is provided with a boom cylinder 24 that operates the boom 18 and a bucket cylinder 25 that operates the bucket 19. The boom cylinder 24 and the bucket cylinder 25 correspond to the working hydraulic actuator of the present invention.

  The boom cylinder 24, the bucket cylinder 25, and an unillustrated steering cylinder are components of the hydraulic drive system 2 shown in FIG. The output of the engine 11 is used for running and as a power source for the hydraulic drive system 2.

  Specifically, as shown in FIGS. 1 and 2, the engine 11 is connected to wheels 15A and 15B via a torque converter 12, a transmission 13, and axles 14A and 14B. The transmission 13 can change the speed ratio between the input shaft and the output shaft, and whether the rotation direction of the output shaft is the same as the input shaft or the reverse direction in order to switch the vehicle forward and reverse. Can be switched.

  A hydraulic drive system 2 shown in FIG. 1 includes a main pump (hydraulic pump) 21 and an accessory pump 23 connected to the torque converter 12. That is, the main pump 21 and the accessory pump 23 are driven by the engine 11. The hydraulic drive system 2 includes a cargo handling circuit (corresponding to a working circuit of the present invention) 34 for driving the boom cylinder 24 and the bucket cylinder 25 and a steering circuit 36 for driving a steering cylinder (not shown).

  The hydraulic oil discharged from the main pump 21 is supplied to the cargo handling circuit 34 and the steering circuit 36. Specifically, a circulation line 31 extends from the hydraulic pump 21 to the tank 32. The circulation line 31 constitutes a center bypass line 34 a of the cargo handling circuit 34. A branch line 35 branches from the circulation line 31 on the upstream side of the cargo handling circuit 34, and this branch line 35 is connected to the steering circuit 36.

  The main pump 21 is a variable displacement pump, and its tilt angle is changed by a regulator 22. The main pump 21 may be a swash plate pump or an oblique shaft pump.

  As shown in FIG. 3, the cargo handling circuit 34 includes a control valve 72 for the boom cylinder 24 and a control valve 71 for the bucket cylinder 25. The center bypass line 34a described above extends so as to penetrate these control valves 71 and 72. A pilot pressure is output from the boom operation valve 82 to the control valve 72 for the boom cylinder 24, and a pilot pressure is output from the bucket operation valve 81 to the control valve 71 for the bucket cylinder 25. The boom operation valve 82 and the bucket operation valve 81 are disposed in the cab 17. Further, the boom operation valve 82 and the bucket operation valve 81 include an operation lever, and output a pilot pressure corresponding to the operation amount of the operation lever.

  Although not shown, the steering circuit 36 includes a steering valve that controls supply and discharge of hydraulic oil to and from the steering cylinder. For example, a steering signal (pilot flow) is output to the steering valve from a steering signal output device such as Orbit Roll (registered trademark). The steering signal output device is connected to a steering wheel disposed in the cab 17 via a steering shaft.

  Returning to FIG. 1, the circulation line 31 is provided with a throttle 33 on the downstream side of the cargo handling circuit 34. Although not shown, the circulation line 31 is connected to a bypass line that bypasses the throttle 33, and a relief valve is provided in the bypass line. A portion of the circulation line 31 between the cargo handling circuit 34 and the throttle 33 is connected to the regulator 22 by a pilot line 51.

  When both the boom cylinder 24 and the bucket cylinder 25 are not driven, the entire amount of hydraulic oil supplied from the main pump 21 to the cargo handling circuit 34 passes through the throttle 33, so the pressure on the upstream side of the throttle 33 in the circulation line 31. The negative control pressure Pn is increased. On the other hand, when the boom cylinder 24 and / or the bucket cylinder 25 are driven, only a part of the hydraulic oil supplied from the main pump 21 to the cargo handling circuit 34 passes through the throttle 33, so the negative control pressure Pn is low. Become.

  The regulator 22 decreases the tilt angle of the main pump 21 when the pressure guided through the pilot line 51 is high, and increases the tilt angle of the main pump 21 when the pressure guided through the pilot line 51 is low. When the tilt angle of the main pump 21 decreases, the discharge flow rate of the main pump 21 decreases, and when the tilt angle of the main pump 21 increases, the discharge flow rate of the main pump 21 increases. When the pressure guided by the pilot line 51 becomes higher than the reference pressure Pt, the tilt angle of the main pump 21 is minimized, and the discharge flow rate of the main pump 21 is minimized.

  A switching valve 52 is provided in the pilot line 51. The switching valve 52 will be described in detail later.

  The hydraulic oil discharged from the accessory pump 23 is guided to the fan circuit 42, the traveling brake 45 and the parking brake 46 through the supply line 4. The accessory pump 23 is a fixed displacement pump in this embodiment, but may be a variable displacement pump.

  The fan circuit 42 is for driving the fan motor 26 (see FIG. 2) that sends wind to the radiator 16 for the engine 11 (see FIG. 2). That is, the fan circuit 42 is a circuit for cooling the engine 11.

  The supply line 4 is provided with an unloader valve 41, and hydraulic oil discharged from the accessory pump 23 by the unloader valve 41 is distributed to the brakes 45 and 46 side and the fan circuit 42 side. That is, the supply line 4 includes a main flow path 4 a that connects the accessory pump 23 to the unloader valve 41, a first branch 4 b that connects the unloader valve 41 to the traveling brake 45 and the parking brake 46, and the unloader valve 41 to the fan circuit 42. A second branch 4c to be connected is included.

  The unloader valve 41 preferentially supplies hydraulic oil to the first tributary 4b when the pressure of the first tributary 4b falls below the set pressure Pb by the operation of the traveling brake 45 or the parking brake 46, and the pressure of the first tributary 4b. When the pressure exceeds the set pressure Pb, the hydraulic oil is supplied to the second branch 4c.

  The first branch 4b is provided with a check valve 43 and an accumulator 44 in order from the upstream side. The downstream portion from the position where the accumulator 44 of the first tributary 4 b is provided is further divided into a first end flow path 4 d connected to the traveling brake 45 and a second end flow path 4 e connected to the parking brake 46.

  The second end passage 4e is provided with a switching valve 47 for switching whether or not the parking brake 46 is operated. The switching valve 47 is electrically connected to the parking brake switch 6 disposed in the cab 17. When the parking brake switch 6 is off, the switching valve 47 opens the second end passage 4e to keep the parking brake 46 in a brake-released state, and when the parking brake switch 6 is turned on, the second end passage 4e is opened. The flow path 4e is blocked and the parking brake 46 is operated.

  From the supply line 4, hydraulic oil is also led to the boom operation valve 82 and the bucket operation valve 81 (see FIG. 3) described above.

  A pressure source line 53 is connected to the switching valve 52 provided in the pilot line 51 described above. In the present embodiment, the pressure source line 53 is connected to the supply line 4. More specifically, the pressure source line 53 is connected to a downstream portion of the check valve 43 in the first tributary 4b. In the illustrated example, the pressure source line 53 is connected to the second terminal flow path 4e on the parking brake 46 side of the first tributary 4b, but the pressure source line 53 is connected to the first terminal flow path 4d on the traveling brake 45 side. It may be connected, or may be connected to a portion between the check valve 43 and the accumulator 44 in the first tributary 4b.

  The discharge pressure of the accessory pump 23 is set to be equal to or higher than the above-described reference pressure Pt that minimizes the tilt angle of the main pump 21. For this reason, the pressure of the supply line 4 and the pressure source line 53 is also equal to or higher than the reference pressure Pt.

  The switching valve 52 is located at a first position where the downstream portion of the pilot line 51 communicates with the upstream portion when traveling is possible, and a second portion which communicates the downstream portion of the pilot line 51 with the pressure source line 53 during the standby state. Switch to position. That is, the switching valve 52 guides the negative control pressure Pn to the regulator 22 at the first position, and guides the pressure of the pressure source line 53 to the regulator 22 at the second position.

  In the present embodiment, the switching valve 52 is electrically connected to the parking brake switch 6 described above. The switching valve 52 is located at the first position when the parking brake switch 6 is off, and is switched to the second position when the parking brake switch 6 is on.

  In the industrial vehicle 1A of the present embodiment, the negative control pressure Pn varies depending on the rotational speed of the engine 11, but the switching valve 52 is set to the second position during the standby state (in the present embodiment, when the vehicle is parked). By switching, not the negative control pressure Pn but the pressure of the pressure source line 53 is guided to the regulator 22. Thereby, even in the standby state, when the boom cylinder 24 and the bucket cylinder 25 are not operating, the discharge flow rate of the main pump 21 can be minimized. As a result, the fuel consumption of the engine 11 in the standby state can be improved.

  In the present embodiment, the switching valve 52 is switched in conjunction with the on / off of the parking brake switch 6. For this reason, the switching valve 52 can always be maintained at the second position during parking. Further, since the switching valve 52 can be automatically switched to the second position using the electrical signal of the parking brake switch 6, it is not necessary to make a special determination using the control device.

  Furthermore, in this embodiment, the pressure source line 53 is connected to the supply line 4 extending from the accessory pump 23. For this reason, the discharge pressure of the accessory pump 23 can be rationally used as a pressure source.

  In the present embodiment, the pressure source line 53 is connected to the downstream portion of the check valve 43 in the first branch 4 b of the supply line 4. The pressure of the first branch 4b, which is the pressure for the traveling brake 45 and the parking brake 46, is kept substantially constant. Therefore, this stable pressure can be guided to the regulator 22 during the standby state.

<Modification>
In the embodiment, the pressure source line 53 is connected to the downstream portion of the check valve 43 in the first branch 4 b of the supply line 4. However, the pressure source line 53 may be connected to the second branch 4c of the supply line 4 as in the industrial vehicle 1B of the first modified example shown in FIG.

  Or the pressure source line 53 may be connected to the main flow path 4a of the supply line 4 like the industrial vehicle 1C of the 2nd modification shown in FIG. In this case, the pressure source line 53 is preferably provided with a check valve 54 and an accumulator 55 in order from the upstream side.

(Second Embodiment)
Next, with reference to FIG. 6, an industrial vehicle 1D according to a second embodiment of the present invention will be described. In the present embodiment and third and fourth embodiments described later, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The industrial vehicle 1D of the present embodiment is different from the industrial vehicle 1A of the first embodiment in that, in the first embodiment, the switching valve 52 is directly electrically connected to the parking brake switch 6. In the present embodiment, the switching valve 52 is only electrically connected to the parking brake switch 6 via the control device 7.

  The control device 7 controls the switching valve 52 based on the operating situation. Specifically, the control device 7 determines a certain period of time after satisfying both the first condition in which the travel lever (not shown) disposed in the cab 17 is positioned at the neutral position and the second condition in which the travel brake 45 is operated. When (for example, 30 seconds) elapses, the switching valve 52 is connected to the pressure source line 53 from the first position where the downstream portion of the pilot line 51 communicates with the upstream portion. Switch to position 2.

  Further, the control device 7 positions the switching valve 52 in the first position when the parking brake switch 6 is off, and switches it to the second position when the parking brake switch 6 is on.

  Also in the present embodiment, as in the first embodiment, the switching valve 52 is in the standby state (in the present embodiment, when the above-mentioned specific state in the stopped state and when the parking state is entered). Since it switches to the 2 position, the discharge flow rate of the main pump 21 can be minimized when the boom cylinder 24 and the bucket cylinder 25 are not operating even in the standby state. As a result, the fuel consumption of the engine 11 in the standby state can be improved.

  In particular, in the present embodiment, the switching valve 52 is turned on when a certain time has elapsed since both the first condition in which the travel lever (not shown) is located in the neutral position and the second condition in which the travel brake 45 is operated are satisfied. Switch to the second position. As described above, since the switching valve 52 is switched to the second position even when the vehicle is stopped for a short period of time during which travel is interrupted, the fuel efficiency improvement effect of the engine 11 can be obtained in a wide range of the standby state.

  In addition, the effect by connecting the pressure source line 53 to the supply line 4 extended from the accessory pump 3 is the same as that of 1st Embodiment. Moreover, it cannot be overemphasized that the 1st and 2nd modification of 1st Embodiment shown in FIG. 4 and FIG. 5 is applicable to this embodiment.

(Third embodiment)
Next, an industrial vehicle 1E according to a second embodiment of the present invention will be described with reference to FIG. The industrial vehicle 1E of the present embodiment is different from the industrial vehicle 1A of the first embodiment in that the pressure source line 53 is connected to the supply line 4 extending from the accessory pump 23 in the first embodiment. In the embodiment, the pressure source line 53 is only connected to the upstream side portion of the cargo handling circuit 34 in the circulation line 31.

  The pressure source line 53 is provided with a check valve 54 and an accumulator 55 in order from the upstream side. Although the pressure in the circulation line 31 fluctuates, since the check valve 54 and the accumulator 55 are provided in the pressure source line 53, the highest pressure in the circulation line 31 is accumulated in the accumulator 55. Naturally, the pressure accumulated in the accumulator 55 is equal to or higher than the reference pressure Pt that minimizes the tilt angle of the main pump 21 described in the first embodiment.

  Also in the present embodiment, as in the first embodiment, the switching valve 52 switches from the first position to the second position during the standby state (when the parking state is reached), so that the fuel consumption of the engine 11 in the standby state is improved. Can be improved. Further, in this embodiment, the pressure downstream of the check valve 54 in the pressure source line 53 is kept substantially constant, so that this stable pressure can be guided to the regulator 22 during the standby state.

  In this embodiment, the switching valve 52 may be controlled using the control device 7 as in the second embodiment. In other words, the switching valve 52 changes from the first position to the first position when a certain time has elapsed after both the first condition in which the travel lever (not shown) is positioned in the neutral position and the second condition in which the travel brake 45 is operated are satisfied. It may be switched to two positions.

(Fourth embodiment)
Next, with reference to FIG. 8, an industrial vehicle 1F according to a fourth embodiment of the present invention will be described. In the present embodiment, the hydraulic drive system 2 includes an auxiliary pump 27 in addition to the main pump 21 and the accessory pump 23. A pressure source line 53 is connected to the auxiliary pump 27.

  A relief line 56 branches off from the pressure source line 53, and a relief valve 57 is provided in the relief line 56. The set pressure of the relief valve 57 is set to be equal to or higher than the reference pressure Pt that minimizes the tilt angle of the main pump 21 described in the first embodiment.

  Also in the present embodiment, as in the first embodiment, the switching valve 52 switches from the first position to the second position during the standby state (when the parking state is reached), so that the fuel consumption of the engine 11 in the standby state is improved. Can be improved.

  In this embodiment, the switching valve 52 may be controlled using the control device 7 as in the second embodiment. In other words, the switching valve 52 changes from the first position to the first position when a certain time has elapsed after both the first condition in which the travel lever (not shown) is positioned in the neutral position and the second condition in which the travel brake 45 is operated are satisfied. It may be switched to two positions.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, in the case of the configuration shown in FIGS. 7 and 8, the industrial vehicle may not have the accessory pump 23.

  The present invention is applicable to various industrial vehicles in which the output of the engine is used for traveling and is used as a power source for a hydraulic drive system.

1A to 1F Industrial vehicles 21 Main pump (hydraulic pump)
22 Regulator 23 Accessory pump 24 Boom cylinder (hydraulic actuator)
25 Bucket cylinder (hydraulic actuator)
31 Circulation line 32 Tank 33 Restriction 34 Cargo handling circuit (working circuit)
34a Center bypass line 4 Supply line 4a Main flow path 4b 1st tributary 4c 2nd tributary 41 Unloader valve 42 Fan circuit 43 Check valve 44 Accumulator 45 Traveling brake 46 Parking brake 51 Pilot line 52 Switching valve 53 Pressure source line 54 Check valve 55 Accumulator 6 Parking brake switch 7 Control device

Claims (6)

An engine whose output is used for traveling,
A hydraulic pump driven by the engine and having a tilt angle changed by a regulator;
A circulation line constituting a center bypass line of a work circuit for driving a working hydraulic actuator extending from the hydraulic pump to the tank, wherein a circulation line provided with a throttle on the downstream side of the work circuit;
A pilot line connecting the regulator and the part between the working circuit and the throttle in the circulation line;
A switching valve provided in the pilot line, to which a pressure source line having a pressure equal to or higher than a reference pressure that minimizes the tilt angle of the main pump is connected, and when traveling is possible, on the upstream side of the throttle in the circulation line A switching valve located at a first position leading pressure to the regulator and switching to a second position leading pressure of the pressure source line to the regulator during a standby state;
An industrial vehicle comprising:   2. The industrial vehicle according to claim 1, wherein the switching valve is located at the first position when a parking brake switch is off, and switches to the second position when the parking brake switch is on. A control device for controlling the switching valve;
The control device moves the switching valve from the first position to the first position when a predetermined time has elapsed after both the first condition for the travel lever to be in the neutral position and the second condition for the travel brake to operate are satisfied. The industrial vehicle according to claim 1, wherein the industrial vehicle is switched between two positions. The hydraulic pump is a main pump;
An accessory pump driven by the engine,
The industrial vehicle according to any one of claims 1 to 3, wherein the pressure source line is connected to a supply line that guides hydraulic oil discharged from the accessory pump. The supply line connects a main flow path connecting the accessory pump to an unloader valve, a first branch connecting the unloader valve to a travel brake and a parking brake, and connecting the unloader valve to a fan circuit for cooling the engine. Including the second tributary,
The unloader valve preferentially supplies hydraulic oil to the first tributary when the pressure of the first tributary falls below a set pressure, and the second load when the pressure of the first tributary exceeds the set pressure. Configured to supply hydraulic oil to the tributary,
The first tributary is provided with a check valve and an accumulator in order from the upstream side, and the pressure source line is connected to a downstream portion of the check valve in the first tributary. 4. The industrial vehicle according to 4. The pressure source line is connected to an upstream portion of the work circuit in the circulation line, and the pressure source line is provided with a check valve and an accumulator in order from the upstream side. 4. The industrial vehicle according to any one of 3.

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