Working machine

Abstract

To facilitate the starting of an engine in a working machine comprising an operation oil passage for supplying pressure oil from a hydraulic pump driven by the engine, to a working device drive part.SOLUTION: A drain oil passage 44 is connected to a place P2 on the upstream side of a control valve 39 of a working device drive part 29, and on the upstream side of a place P1 to which a relief valve 43 is connected, out of an operation oil passage 40. A working machine comprises an opening / closing valve 45 for opening / closing the drain oil passage 44, and a control device 47 for controlling the opening / closing valve 45. The control device 47 switches the opening / closing valve 45 to an opened state until detecting the starting of the engine 4 after detecting the starting operation of the engine 4, and switches the opening / closing valve 45 to a closed state when detecting the starting of the engine 4.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] As shown in Patent Document 1, there is a working machine (tractor) including a working device drive unit (PTO clutch) supplied with pressure oil from a hydraulic pump, an operation oil passage (second oil passage, second control oil passage) connecting the hydraulic pump and the working device drive unit and supplying the pressure oil from the hydraulic pump to the working device drive unit, a control valve (second control valve) provided in the operation oil passage and controlling the working device drive unit, and a relief valve (pressure adjustment valve) connected to a location upstream of the control valve in the operation oil passage and setting the pressure of the pressure oil supplied to the working device drive unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described working machine, in the case where the hydraulic pump is driven by an engine, when starting the engine, the hydraulic pump tries to rotate together with the engine, and a load due to the hydraulic pump is applied to the engine, so that the engine may be difficult to start. In particular, in a cold region or the like where the hydraulic oil is cold, the viscosity of the hydraulic oil becomes high, and the load applied by the hydraulic oil to the hydraulic pump that tries to rotate increases, so that the load applied to the engine by the hydraulic pump increases and the engine becomes difficult to start.

[0005] The present invention provides a working machine that is easy to start an engine while the hydraulic pump is driven by the engine.

Means for Solving the Problems

[0006] The working machine according to the present invention includes a hydraulic pump driven by an engine, a working device drive unit to which pressure oil from the hydraulic pump is supplied, an operation oil passage that connects the hydraulic pump and the working device drive unit and supplies the pressure oil from the hydraulic pump to the working device drive unit, a control valve provided in the operation oil passage to control the working device drive unit, a relief valve connected to a location upstream of the control valve in the operation oil passage to set the pressure of the pressure oil supplied to the working device drive unit, a drain oil passage connected to a location upstream of the control valve and also upstream of the location where the relief valve is connected in the operation oil passage to be able to discharge pressure oil without passing through the relief valve from the operation oil passage, an on-off valve to open and close the drain oil passage, and a control device to control the on-off valve based on the state of the engine. The control device switches the on-off valve to an open state between detecting the start operation of the engine and detecting the start of the engine, and switches the on-off valve to a closed state when detecting the start of the engine.

[0007] According to this configuration, when the start operation of the engine is performed, the on-off valve is opened by the control device and the operation oil passage is opened by the drain oil passage to enable the discharge of the working oil. Therefore, compared with the case where the operation oil passage remains closed, the load applied to the hydraulic pump that tries to rotate with the engine by the working oil is reduced, making it easier to start the engine. When the engine starts, the on-off valve is closed by the control mechanism to prevent the discharge of the working oil through the drain oil passage of the operation oil passage. Thus, it is possible to supply the pressure oil set by the relief valve as the pressure required for the operation of the working device drive unit to the working device drive unit.

[0008] In the present invention, it is preferable that a starter device for starting the engine is provided, and the control device detects the start operation of the engine based on the operation position of the starter device.

[0009] According to this configuration, since the starter device is utilized for the detection means that detects the starting operation of the engine, the engine can be easily started at low cost.

[0010] In the present invention, the starter device includes a starting device unit that starts the engine, and a key switch that can be switched between a power-on position for performing a power-on operation of a power source and a starting position for operating the starting device unit. When the control device detects that the key switch has been switched to the power-on position, it is preferable to determine that the starting operation of the engine has been performed.

[0011] According to this configuration, when the hydraulic pump attempts to rotate together with the engine, the on-off valve is opened and the operation oil passage is opened by the drain oil passage. That is, since the hydraulic pump starts to rotate in a state where the load applied to the hydraulic pump by the working oil is reduced, the engine can be easily started.

[0012] In the present invention, a rotational speed detection mechanism for detecting the rotational speed of the engine is provided, and it is preferable that the control device determines that the engine has started when the engine reaches the idling rotational speed based on the detection result by the rotational speed detection mechanism.

[0013] According to this configuration, when the engine starts and reaches the idling rotational speed, the on-off valve is closed by the control mechanism to prevent the discharge of the pressure oil in the operation oil passage through the drain oil passage. Therefore, the pressure oil that is stably maintained at the pressure set by the relief valve can be supplied to the working device drive unit.

[0014] In the present invention, a hydrostatic continuously variable transmission device that changes the power from the engine and transmits it to the traveling device is provided, and it is preferable that the pressure oil discharged from the relief valve is supplied as the working oil to the continuously variable transmission device.

[0015] According to this configuration, since the pressure oil discharged from the relief valve is supplied as hydraulic oil to the continuously variable transmission, the pressure oil discharged from the relief valve can be utilized without waste.

[0016] In the present invention, a valve unit including the control valve, the relief valve, and the on-off valve is provided. Among the valve units, it is preferable that the drain oil passage is connected to a location on the operation oil passage that is upstream of the control valve and also upstream of the location where the relief valve is connected.

[0017] According to this configuration, by assembling the valve unit, the control valve, the relief valve, and the on-off valve can be assembled together, so it is easy to assemble the control valve, the relief valve, and the on-off valve.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an embodiment of a tractor, which is an example of a working machine according to the present invention, will be described with reference to the drawings. In the embodiment, when defining the front-rear direction of the traveling body of the tractor, it is defined along the traveling direction of the traveling body in the working state, and when defining the left-right direction of the traveling body, the left and right are defined in the state seen from the traveling direction of the traveling body. That is, the direction indicated by the symbol (F) in FIGS. 1 and 2 is the front side of the traveling body, and the direction indicated by the symbol (B) in FIGS. 1 and 2 is the rear side of the traveling body. The direction indicated by the symbol (L) in FIG. 2 is the left side of the traveling body, and the direction indicated by the symbol (R) in FIG. 2 is the right side of the traveling body. Therefore, the left-right direction of the traveling body corresponds to the width direction of the traveling body.

[0020] 〔Overall configuration〕 In FIGS. 1 and 2, a tractor is shown. This tractor includes a traveling body 3 supported by a pair of left and right steerable and drivable front wheels 1 (traveling devices) and a pair of left and right drivable rear wheels 2 (traveling devices). At the front part of the traveling body 3, a power unit 5 including an engine 4 is provided. At the rear part of the traveling body 3, a driver's cab 6 where an operator rides to perform driving operations and a link mechanism 7 that connects a working device such as a rotary tiller in a liftable manner are provided. The driver's cab 6 is equipped with a driver's seat 8, a steering wheel 9 for steering the front wheels 1, and a cabin 10 that covers the boarding space. The body frame 11 of the traveling body 3 is composed of an engine 4, a transmission case 12 whose front part is connected to the rear part of the engine 4, a front wheel support frame 13 connected to the lower part of the engine 4, and the like. At the rear part of the transmission case 12, a rear PTO shaft 14 for transmitting the power from the engine 4 to the working device connected by the link mechanism 7 is provided. At the lower part of the transmission case 12, a mid PTO shaft 15 for transmitting the power from the engine 4 to a mowing device or the like connected to the lower part of the traveling body 3 is provided. In FIG. 2, for the sake of convenience, the cabin 10 is removed.

[0021] 〔Power transmission device for traveling, power transmission device for work〕 A traveling power transmission device 16 that transmits the power from the engine 4 to the front wheels 1 and the rear wheels 2, and a working power transmission device 17 that transmits the power from the engine 4 to the rear PTO shaft 14 and the mid PTO shaft 15 are configured as shown in FIG. 3. The traveling power transmission device 16 and the working power transmission device 17 are provided inside the transmission case 12.

[0022] As shown in FIG. 3, in the traveling power transmission device 16, the output of the engine 4 is input via the main clutch 18, the first drive shaft 19, and the second drive shaft 20 whose front part is connected to the rear part of the first drive shaft 19, and the input power is shifted and output toward the front wheels 1 and the rear wheels 2. It includes a continuously variable transmission 21, a gear transmission 23 whose output is input via the rotating shaft 22, a rear wheel differential mechanism 24 whose output of the gear transmission 23 is input by the input shaft 24a and outputs the input power to the left and right rear wheels 2, and a front wheel output shaft 26 to which the power of the input shaft 24a is transmitted via the gear linkage mechanism 25. The continuously variable transmission 21 is composed of a variable displacement hydraulic pump 21a to which the power of the second drive shaft 20 is input, and a hydraulic motor 21b that is driven by the pressure oil from the hydraulic pump 21a and outputs to the rotating shaft 22. The continuously variable transmission 21 is composed of a hydrostatic continuously variable transmission. A clutch 25a that cuts off the power transmission from the gear linkage mechanism 25 to the front wheel output shaft 26 is provided across the gear linkage mechanism 25 and the front wheel output shaft 26. The power of the front wheel output shaft 26 is configured to be transmitted to the front wheel differential mechanism 28 via the rotating shaft 27.

[0023] As shown in FIG. 3, the power transmission device 17 for work includes a PTO clutch 29 as a working device drive unit in which the power of the second drive shaft 20 is input via the pump shaft of the hydraulic pump 21a, a PTO transmission 31 in which the output of the PTO clutch 29 is input via the rotary shaft 30 and the input power is shifted and output to the rear PTO shaft 14, an intermediate transmission shaft 33 in which the power of the rotary shaft 30 is transmitted via the first gear linkage mechanism 32, and a second gear linkage mechanism 34 that transmits the power of the intermediate transmission shaft 33 to the mid PTO shaft 15. When the PTO clutch 29 is operated to engage, the power from the engine 4 is transmitted to the rear PTO shaft 14, and when the PTO clutch 29 is operated to disengage, the power transmission to the rear PTO shaft 14 is cut off. A mid PTO clutch 32a is provided across the first gear linkage mechanism 32 and the intermediate transmission shaft 33. When the mid PTO clutch 32a is operated to engage, power is transmitted to the mid PTO shaft 15, and when the mid PTO clutch 32a is operated to disengage, the power transmission to the mid PTO shaft 15 is cut off.

[0024] 〔Operating device for PTO clutch〕 The PTO clutch 29 is configured as a hydraulic-operated clutch such that it is switched to engage when pressure oil is supplied and switched to disengage when the pressure oil is discharged by a spring 29a (see FIG. 4). An operating device 35 and a hydraulic circuit that enable the operation of the PTO clutch 29 are configured as shown in FIG. 4.

[0025] As shown in FIG. 4, the operating device 35 includes a hydraulic pump 38 driven by the engine 4. The hydraulic pump 38 takes hydraulic oil from the hydraulic oil tank 36 through the filter 37, and discharges the taken hydraulic oil as pressurized oil. The hydraulic pump 38 and the PTO clutch 29 are connected by an operation oil passage 40, and the pressurized oil from the hydraulic pump 38 is configured to be supplied as operation oil to the PTO clutch 29 through the operation oil passage 40. A control valve 39 for controlling the PTO clutch 29 is provided in the operation oil passage 40. When the control valve 39 is operated to the on position, it supplies pressurized oil to the PTO clutch 29 to control the PTO clutch 29 to engage, and when it is operated to the off position, it discharges the pressurized oil from the PTO clutch 29 to control the PTO clutch 29 to disengage. The operation oil passage 40 includes a pump-side oil passage portion 40a connecting the input port 54a of the valve unit 53 including the control valve 39 and the hydraulic pump 38, an in-unit oil passage portion 40b provided in the valve unit 53, and a clutch-side oil passage portion 40c connecting the output port 54b of the valve unit 53 and the PTO clutch 29. An oil cooler 41 is provided in the pump-side oil passage portion 40a.

[0026] Among the operation oil passages 40, a relief valve 43 for setting the pressure of the pressure oil supplied to the PTO clutch 29 is connected to a location P1 on the upstream side of the control valve 39. A drain oil passage 44 is connected to a location P2 on the upstream side of the control valve 39 and also on the upstream side of the location P1 to which the relief valve 43 is connected in the operation oil passage 40. The drain oil passage 44 is opened and closed by an on-off valve 45. When the on-off valve 45 is opened, the pressure oil in the operation oil passage 40 can be discharged through the drain oil passage 44 without passing through the relief valve 43, and when it is closed, the discharge of the pressure oil in the operation oil passage 40 through the drain oil passage 44 is blocked. The drain oil passage 44 includes an in-unit oil passage portion 44a provided inside the valve unit 53 and a tank-side oil passage portion 44b connecting the drain port 57 of the valve unit 53 to the hydraulic oil tank 36. The on-off valve 45 is provided in the valve unit 53 and is provided in the in-unit oil passage portion 44a. The drain port 55 of the valve unit 53 and the charge port 21c of the continuously variable transmission 21 are connected by a supply oil passage 46, and the pressure oil discharged from the relief valve 43 is configured to be supplied as hydraulic oil to the continuously variable transmission 21 through the supply oil passage 46. In the present embodiment, the hydraulic oil tank 36 is constituted by the transmission case 12, and the lubricating oil stored in the transmission case 12 is utilized as hydraulic oil. The hydraulic pump 38 is constituted by a gear pump.

[0027] In the operating device 35, when the on-off valve 45 is closed, the discharge of the pressure oil from the operation oil passage 40 to the drain oil passage 44 is blocked, and the pressure oil from the hydraulic pump 38 is supplied to the control valve 39. When the control valve 39 is switched to the engaged position, the pressure oil set by the relief valve 43 as the pressure oil required for the operation of the PTO clutch 29 is supplied from the control valve 39 to the PTO clutch 29, and the PTO clutch 29 is switched to the engaged position. When the control valve 39 is switched to the disengaged position, the pressure oil of the PTO clutch 29 is discharged from the control valve 39 to the drain oil passage 36a, and the PTO clutch 29 is switched to the disengaged position. When the pressure oil is discharged from the relief valve 43, the discharged pressure oil is supplied as hydraulic oil to the continuously variable transmission 21 through the supply oil passage 46.

[0028] As shown in FIG. 4, a control device 47 that controls an on-off valve 45 based on the state of an engine 4 is linked to the on-off valve 45. The linkage of the control device 47 to the on-off valve 45 is achieved by configuring the on-off valve 45 as an electromagnetic operation valve and connecting the control device 47 so as to output an electric signal to the on-off valve 45. The control device 47 is configured to switch the on-off valve 45 to an open state from when it detects a starting operation of the engine 4 until it detects the start of the engine 4, and to switch the on-off valve 45 to a closed state when it detects the start of the engine 4. That is, when a starting operation of the engine 4 is performed, the on-off valve 45 is opened by the control device 47, enabling the discharge of the hydraulic oil in the operation oil passage 40 through the drain oil passage 44. Compared with the case where the hydraulic oil in the operation oil passage 40 cannot be discharged, the load applied to the hydraulic pump 38 that attempts to rotate with the engine 4 by the hydraulic oil becomes lighter. When the engine 4 starts, the on-off valve 45 is closed by the control device 47, preventing the outflow of the pressure oil through the drain oil passage 44 of the operation oil passage 40, and enabling the supply of the pressure oil set by the relief valve 43 to the PTO clutch 29.

[0029] 〔Control Device〕 As shown in FIG. 4, the control device 47 is linked to a starter device 48 that starts the engine 4 so as to detect a starting operation of the engine 4 based on the operation position of the starter device 48, and is linked to a rotational speed detection mechanism 51 that detects the rotational speed of the engine 4 so as to determine that the engine 4 has started based on the detection result by the rotational speed detection mechanism 51.

[0030] Specifically, as shown in FIG. 4, the starter device 48 includes a starting device unit 49 that starts the engine 4 by a starter motor (not shown), and a key switch 50 linked to the starting device unit 49. The key switch 50 is provided with a key detachment position 50a for inserting and removing a key (not shown), a power-on position 50b for turning on the power of the starting device unit 49 and the like, and a starting position 50c for operating the starting device unit 49. As shown in FIG. 4, the key detachment position 50a, the power-on position 50b, and the starting position 50c are arranged such that the key detachment position 50a and the power-on position 50b are adjacent to each other, and the starting position 50c is adjacent to the power-on position 50b on the side opposite to the side where the key detachment position 50a is located with respect to the power-on position 50b. The key switch 50 is configured such that when the key mounted at the key detachment position 50a is rotated in the rotation direction indicated by the arrow A, the key moves from the key detachment position 50a to the power-on position 50b, switching the power of the starting device unit 49 and the like from off to on, and then moves from the power-on position 50b to the starting position 50c, switching the starting device unit 49 from off to on.

[0031] Based on the information from the key switch 50, when the control device 47 detects that the key switch 50 has been switched from the key detachment position 50a to the power-on position 50b, it is configured to determine that the engine 4 has been moved and operate to open the on-off valve 45.

[0032] Based on the detection result of the rotation speed detection mechanism 51, when the control device 47 detects that the engine 4 has reached the idling rotation speed, it is configured to determine that the engine 4 has started and operate to close the on-off valve 45.

[0033] FIG. 5 is an explanatory diagram showing the change over time in the states of the key switch 50, power source, starting device unit 49, engine 4, and on-off valve 45. The horizontal axis in FIG. 5 indicates the elapsed time t. As shown in FIG. 5, when the key switch 50 is turned to the power-on position 50b and the power source is turned on, the on-off valve 45 is opened and operated by the control device 47, and the drain oil passage 44 is opened. When the key switch 50 is switched from the power-on position 50b to the starting position 50c, the starting device unit 49 is turned on and the engine 4 is started. When the engine 4 starts, the starting device unit 49 returns to the off state. When the engine 4 starts and the rotational speed of the engine 4 increases and the engine 4 is in the idling drive state, the on-off valve 45 is closed and operated by the control device 47, and the drain oil passage 44 returns to the closed state.

[0034] 〔Valve Unit〕 As shown in FIGS. 4 and 6, the control valve 39, relief valve 43, and on-off valve 45 are provided in the same valve housing 52 and are configured in a valve unit 53. As shown in FIG. 4, within the valve unit 53, the unit internal oil passage portion 44a of the drain oil passage 44 is connected to a location P2 on the upstream side of the control valve 39 and the relief valve 43 in the unit internal oil passage portion 40b of the operation oil passage 40. An input port 54a for inputting pressure oil from the hydraulic pump 38 is provided at the lower part of the valve housing 52. An oil drain port 55 to which the replenishing oil passage 46 is connected is provided at the side portion of the valve housing 52. An output port 54b to which the clutch side oil passage portion 40c of the operation oil passage 40 is connected is provided at the rear part of the valve housing 52. A drain port 57 to which the tank side oil passage portion 44b of the drain oil passage 44 is connected is provided at the upper part of the valve housing 52.

[0035] As shown in FIGS. 2 and 3, the valve unit 53 is supported on the lateral side of the transmission case 12 below the floor portion 6a of the operation unit 6 and between the front wheels 1 and the rear wheels 2. The valve unit 53 is supported on the transmission case 12 by engaging a connecting bolt (not shown) that passes through mounting holes 58 (see FIG. 6) provided at four locations of the valve housing 52 with the transmission case 12. The oil cooler 41 is provided at a location in the engine room that is in front of the radiator 59 for the engine.

[0036] As shown in FIG. 2, the clutch-side oil passage portion 40c that connects the output port 54b of the valve unit 53 and the PTO clutch 29 is piped so as to pass through the outside of the transmission case 12 in the front-rear direction of the traveling body 3. The pump-side oil passage portion 40a that connects the oil cooler 41 and the input port 54a of the valve unit 53 is piped so as to pass through below the engine 4 in the front-rear direction of the traveling body 3. The supply oil passage 46 that connects the drain port 55 of the valve unit 53 and the charge port 21c of the continuously variable transmission 21 is piped so as to pass through the inside of the transmission case 12 in the front-rear direction of the traveling body 3.

[0037] 〔Alternative Embodiment〕 (1) FIG. 7 shows the hydraulic circuit of a working machine according to another embodiment. In the working machine according to another embodiment, a front-wheel speed increasing device (not shown) that increases the driving speed of the front wheels 1 more than the driving speed of the rear wheels 2, and a front-wheel speed increasing clutch 60 that switches the on / off operation of the front-wheel speed increasing device are provided. In the hydraulic circuit according to another embodiment, a clutch operation oil passage 61 is provided that connects a location P2, which is upstream of the control valve 39 and also upstream of a location P1 where the relief valve 43 is connected, in the operation oil passage 40, and the front-wheel speed increasing clutch 60, and supplies pressure oil from the hydraulic pump 38 to the front-wheel speed increasing clutch 60. A clutch control valve 62 for controlling the on / off of the front-wheel speed increasing clutch 60 is provided in the clutch operation oil passage 61.

[0038] In the clutch operation oil passage 61, a flow path switching valve 64 is provided at a location upstream of the clutch control valve 62, and a tank side drain oil passage 63 is connected to the flow path switching valve 64. The flow path switching valve 64 is configured to be switchable between a first operation position 64a that closes the clutch operation oil passage 61 and connects an oil passage portion 61a upstream of the flow path switching valve 64 in the clutch operation oil passage 61 and the tank side drain oil passage 63, and a second operation position 64b that opens the clutch operation oil passage 61 and cuts off the communication between the oil passage portion 61a and the tank side drain oil passage 63.

[0039] That is, an oil passage portion 61a in the clutch operation oil passage 61 and the tank side drain oil passage 63 are connected to a location P2 upstream of a location P1 where a relief valve 43 is connected and upstream of a control valve 39 in the operation oil passage 40, and a drain oil passage 44 capable of discharging pressure oil from the operation oil passage 40 without passing through the relief valve 43 is configured. An on-off valve 45 that opens and closes the drain oil passage 44 by the flow path switching valve 64 and is controlled to open and close by a control device 47 is configured.

[0040] The clutch control valve 62, the flow path switching valve 64, the control valve 39, and the relief valve 43 are provided in a single valve housing (not shown) and configured as a valve unit 65. In the present embodiment, the clutch control valve 62, the flow path switching valve 64, the control valve 39, and the relief valve 43 are configured as the valve unit 65, but they may be provided in separate valve housings and not configured as a valve unit.

[0041] (2) In the above-described embodiment, an example in which a PTO clutch 29 is adopted as the working device drive unit is shown. However, the present invention is not limited to this, and as the working device drive unit, various devices for driving the working device can be adopted, such as a transmission that changes the driving speed of the working device by a hydraulically operated clutch.

[0042] (3) In the above-described embodiment, an example is shown in which the detection of the starting operation of the engine 4 is configured to be performed based on the operation position of the key switch 50 in the starter device 48. However, it may be performed based on the state of the starting device portion 49 in the starter device 48 or the detection result of the rotation speed detection mechanism that detects the rotation speed of the engine 4.

[0043] (4) In the above-described embodiment, an example is shown in which the detection of the starting of the engine 4 is configured to be performed based on the engine 4 entering the idling state. However, it may be performed based on the engine 4 reaching a rotation speed lower than the idling state.

[0044] (5) In the above-described embodiment, an example is shown in which the control valve 39, the relief valve 43, and the on-off valve 45 are configured in the valve unit 53. However, the present invention is not limited to this, and the control valve 39, the relief valve 43, and the on-off valve 45 may be provided in separate valve housings.

[0045] (6) In the above-described embodiment, the traveling device includes the front wheels 1 and the rear wheels 2. However, as the traveling device, a crawler traveling device or a mini crawler traveling device can be adopted.

Industrial Applicability

[0046] The present invention can be applied to a working machine including a hydraulic pump driven by an engine and a working device drive unit to which pressure oil is supplied from the hydraulic pump.

Explanation of Reference Numerals

[0047] 1 Front wheel (traveling device) 2 Rear wheel (traveling device) 4 Engine 29 PTO clutch (working device drive unit) 38 Hydraulic pump 39 Control valve 43 Relief valve 44 Drain oil passage 45 On-off valve 47 Control device 48 Starter device 49 Starter unit 50 Key switch 50b Power-on position 50c Starting position 51 Rotation speed detection mechanism 53 Valve unit 65 Valve unit Location P1 Location P2

Claims

1. A hydraulic pump driven by an engine, A working device drive unit to which pressure oil from the hydraulic pump is supplied, An operation oil passage that connects the hydraulic pump and the working device drive unit and supplies pressure oil from the hydraulic pump to the working device drive unit, A control valve provided in the operation oil passage to control the working device drive unit, A relief valve that is connected to a location upstream of the control valve in the operation oil passage and sets the pressure of the pressure oil supplied to the working device drive unit, A drain oil passage that is connected to a location upstream of the control valve and also upstream of the location where the relief valve is connected in the operation oil passage, and can discharge pressure oil from the operation oil passage without passing through the relief valve, An on-off valve that opens and closes the drain oil passage, And a control device that controls the on-off valve based on the state of the engine. The control device switches the on-off valve to the open state from when the start operation of the engine is detected until the start of the engine is detected, and switches the on-off valve to the closed state when the start of the engine is detected. A working machine.

2. It is equipped with a starter device for starting the engine, The control device detects the start operation of the engine based on the operation position of the starter device. The working machine according to claim 1.

3. The starter device includes a starting device unit for starting the engine, and a key switch that can be switched between a power-on position for performing a power-on operation of a power source and a starting position for operating the starting device unit. When the control device detects that the key switch has been switched to the power-on position, it determines that the start operation of the engine has been performed. The working machine according to claim 2.

4. It is equipped with a rotation speed detection mechanism for detecting the rotation speed of the engine, The working machine according to any one of claims 1 to 3, wherein the control device determines that the engine has started when the engine reaches the idling speed based on the detection result by the rotation speed detection mechanism.

5. The working machine is provided with a hydrostatic continuously variable transmission that changes the power from the engine and transmits it to the traveling device. The working machine according to claim 1, wherein the pressure oil discharged from the relief valve is supplied as hydraulic oil to the continuously variable transmission.

6. The working machine is provided with a valve unit including the control valve, the relief valve, and the on-off valve. In the valve unit, the drain oil passage is connected to a location on the operation oil passage that is upstream of the control valve and also upstream of the location where the relief valve is connected. The working machine according to claim 1.

Images