Crane

Abstract

In the present invention, a crane comprises a traveling vehicle body having a travel motor driven by a power supply unit, a hydraulic oil supply device that is driven by the power supply unit and that supplies hydraulic oil to a driven unit, and a regenerative brake device that performs regenerative brake control for supplying regenerative power generated by the travel motor to the power supply unit to generate braking force during deceleration of the traveling vehicle body. Under regenerative brake control, the regenerative brake device distributes the regenerative power to the hydraulic oil supply device in accordance with the chargeable power of the power supply unit, and changes the power consumed by the hydraulic oil supply device.

Description

crane

[0001] The present invention relates to a crane.

[0002] Patent Document 1 discloses a mobile crane that includes a lower traveling body having a traveling function and an upper rotating body that is rotatably mounted on the upper part of the lower traveling body. The lower traveling body has an engine and travels using the power of the engine.

[0003] JP 2012-96928 A

[0004] In recent years, from the viewpoint of environmental protection and the like, there has been a demand for the above-mentioned cranes to be electrified.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a crane that can be run on electric power.

[0006] One aspect of the crane according to the present invention comprises a traveling vehicle body having a traveling motor driven by a power supply unit; a hydraulic oil supply device driven by the power supply unit and supplying hydraulic oil to driven parts; and a regenerative braking device that performs regenerative braking control when the traveling vehicle body decelerates by supplying regenerative power generated by the traveling motor to the power supply unit to generate braking force, wherein the regenerative braking device distributes regenerative power to the hydraulic oil supply device according to the chargeable power of the power supply unit during regenerative braking control, and changes the power consumed by the hydraulic oil supply device.

[0007] According to the present invention, a crane that can be traveled by electric power can be provided.

[0008] FIG. 1 is a schematic diagram of a mobile crane according to a first embodiment. FIG. 2 is a block diagram showing a schematic system configuration of the mobile crane. FIG. 3 is a perspective view of the crane with some components omitted. FIG. 4 is a diagram for explaining the arrangement of a transmission member, a tank, and a hydraulic oil supply device. FIG. 5 is a flowchart of regenerative power compensation control.

[0009] An example of an embodiment of a crane according to the present invention will be described in detail below with reference to the drawings. Note that the crane according to the embodiment described below is an example of a crane according to the present invention, and the present invention is not limited to the embodiment described below.

[0010] [Embodiment] A mobile crane 1 according to this embodiment will be described with reference to Figures 1 to 5. Figure 1 is a schematic diagram of a mobile crane 1 (a rough terrain crane in the illustrated case) according to this embodiment. The mobile crane may be, for example, an all-terrain crane, a truck crane, or a loaded truck crane (also referred to as a cargo crane). However, the crane according to the present invention may be various types of cranes.

[0011] Mobile crane 1 has a lower traveling body 2 and an upper rotating body 3. Mobile crane 1 is an electric crane equipped with a high-power battery 60 (see FIG. 2). Mobile crane 1 runs using only the power supplied from high-power battery 60 as its power source. In other words, mobile crane 1 does not have an engine.

[0012] Furthermore, the mobile crane 1 performs operations other than traveling (e.g., crane work, air conditioning, and / or heating) based on the power supplied from the high-power battery 60. The crane work is, for example, a swing operation and / or a winch operation during cargo transport work.

[0013] When decelerating while traveling, such a mobile crane 1 performs regenerative braking control, in which regenerative power generated by the traveling motor 63 is supplied to the high-power battery 60 to generate braking force.

[0014] Then, during regenerative braking control, the mobile crane 1 distributes regenerative power to the hydraulic oil supply device 8 when the remaining battery charge of the high-power system battery 60 is greater than a predetermined value. At this time, the mobile crane 1 changes the power consumed by the hydraulic oil supply device 8 depending on the remaining battery charge. The specific configuration of the mobile crane 1 will be described below. After that, the regenerative braking control performed by the mobile crane 1 will be described.

[0015] First, the configuration of the upper rotating body 3 will be described with reference to Figure 1. Figure 1 is a schematic diagram of a mobile crane 1. The upper rotating body 3 is provided above the lower traveling body 2 and rotates around a rotation central axis α relative to the lower traveling body 2. The upper rotating body 3 has a swivel base 31, a telescopic boom 32, and a cab 33.

[0016] The swivel base 31 is supported on the upper part of the lower traveling body 2 via bearings (not shown). The swivel base 31 rotates based on power generated by a rotation actuator (not shown) provided on the upper rotating body 3.

[0017] In this embodiment, the swing actuator is a hydraulic motor. This motor operates based on the supply and discharge of hydraulic oil. The hydraulic oil is supplied from the undercarriage 2. The swing actuator may also be an electric motor. In this case, the swing electric motor is driven based on power supplied from a high-power battery 60, which will be described later.

[0018] The telescopic boom 32 is supported by the swivel base 31 and has multiple booms that are combined so as to be extendable and retractable. The telescopic boom 32 can change its hoisting angle based on the power generated by the hoisting cylinder 34.

[0019] The hoisting cylinder 34 is a telescopic hydraulic cylinder provided on the upper rotating body 3. The hoisting cylinder 34 operates based on the supply and discharge of hydraulic oil. The hydraulic oil is supplied by a hydraulic oil supply device 8 (see FIG. 2) provided on the lower traveling body 2.

[0020] The telescopic boom 32 extends and retracts based on the power generated by the telescopic cylinder 35. The telescopic cylinder 35 is a hydraulic cylinder that is provided inside the telescopic boom 32. The telescopic cylinder 35 operates based on the supply and discharge of hydraulic oil. The hydraulic oil is supplied by a hydraulic oil supply device 8 (see FIG. 2) provided on the undercarriage 2.

[0021] The telescopic boom 32 also supports a wire rope 36. The wire rope 36 hangs down from the tip of the telescopic boom 32 and has a hook 37 attached to the tip. A portion of the wire rope 36 is wound around a winch 38.

[0022] The winch 38 is driven by power generated by a winch actuator (not shown). In this embodiment, the winch actuator is a hydraulic motor provided on the swivel base 31. This motor operates based on the supply and discharge of hydraulic oil. The hydraulic oil is supplied by a hydraulic oil supply device 8 (see FIG. 2) provided on the undercarriage 2.

[0023] When the winch 38 rotates, the wire rope 36 is wound up or unwound depending on the direction of rotation of the winch 38. The winch motor may be an electric motor. In this case, the winch motor is driven by power supplied from a high-power battery 60 (described later).

[0024] Next, the lower running body 2 will be described with reference to Figures 1 to 4. Note that in describing the structure of the lower running body 2, a Cartesian coordinate system (X, Y, Z) shown in each figure will be used. The X direction corresponds to the front-to-rear direction of the lower running body 2. The positive side of the X direction corresponds to the front side of the lower running body 2. The negative side of the X direction corresponds to the rear side of the lower running body 2. The Y direction corresponds to the left-to-right direction of the lower running body 2. The positive side of the Y direction corresponds to the left side when viewing the lower running body 2 from behind. The negative side of the Y direction corresponds to the right side when viewing the lower running body 2 from behind. The Z direction corresponds to the up-down direction of the lower running body 2. The positive side of the Z direction corresponds to the upper side of the lower running body 2. The negative side of the Z direction corresponds to the lower side of the lower running body 2.

[0025] The undercarriage 2 is an example of a vehicle body and is capable of running on electricity. Specifically, as shown in Figures 1 and 3, the undercarriage 2 has a frame 20, a body 21, a front axle 22, a rear axle 23, front tires 24, rear tires 25, and outriggers 26.

[0026] The frame 20 extends in the front-rear direction and is, for example, a box-shaped member having a rectangular cross section, and forms the skeleton of the lower traveling body 2 .

[0027] The frame 20 also has a transmission member arrangement space 200 formed by a through-hole that passes through the frame 20 in the up-down direction. The transmission member arrangement space 200 is provided in the middle part of the frame 20 in the front-rear direction.

[0028] The frame 20 also has a battery storage space 201 formed by a through-hole that passes through the frame 20 in the vertical direction. The battery storage space 201 is provided in the frame 20 at a position ranging from above the rear axle 23 to the rear end thereof.

[0029] That is, the battery accommodating space 201 is provided in the rear of the frame 20. The location of the battery accommodating space is not limited to the illustrated case. The battery accommodating space may be provided in a position in the frame 20 ranging from above the front axle 22 to the front end. In this case, too, the battery accommodating space may be formed by a through-hole that passes through the frame 20 in the up-down direction.

[0030] The frame 20 has a pair of front outrigger support portions 202 at its front end portion. The frame 20 has a pair of rear outrigger support portions 203 at its rear end portion.

[0031] The body 21 (see FIG. 1 ) is a member that constitutes the outer shape of the lower traveling body 2 and is supported by the frame 20 .

[0032] The front axle 22 is a shaft member that extends in the left-right direction and is supported on a portion of the frame 20 near the front end. Front tires 24 are rotatably supported on both left-right end portions of the front axle 22, respectively.

[0033] The rear axle 23 is a shaft member that extends in the left-right direction and is supported on a portion of the frame 20 near the rear end. Rear tires 25 are rotatably supported on both left-right end portions of the rear axle 23, respectively.

[0034] In this embodiment, the mobile crane 1 is a so-called two-axle type mobile crane equipped with a front axle 22 and a rear axle 23. However, the mobile crane may also be a so-called multi-axle type mobile crane equipped with three or more axles.

[0035] The outriggers 26 include a pair of front outriggers 26 a and a pair of rear outriggers 26 b. The pair of front outriggers 26 a are supported by a pair of front outrigger support portions 202 on the frame 20. The pair of rear outriggers 26 b are supported by a pair of rear outrigger support portions 203 on the frame 20.

[0036] Mobile crane 1 also has a transmission member 4 provided between lower traveling body 2 and upper rotating body 3. Specifically, transmission member 4 is arranged in transmission member arrangement space 200 of frame 20. Such transmission member 4 is a member for transmitting power, fluid (hydraulic oil and / or compressed air), signals, etc. between lower traveling body 2 and upper rotating body 3, which rotate relative to each other.

[0037] 2, the mobile crane 1 has a low-voltage system 5, a high-voltage system 6, and a hydraulic system 7. The configurations of the low-voltage system 5, the high-voltage system 6, and the hydraulic system 7 will be described below.

[0038] First, a description will be given of the low-power system 5. The low-power system 5 includes a lower controller 50, a transmission member 4, an upper controller 51, and a low-power battery 53.

[0039] The lower controller 50 sends, for example, video signals, sensor detection signals, and control signals to the upper controller 51 via the transmission member 4. The control signals are signals for controlling the operation of devices provided on the upper rotating body 3, which is the control target. The lower controller 50 operates based on power supplied from the low-voltage battery 53.

[0040] The upper controller 51 sends the signal received from the lower controller 50 to a control device that controls the operation of the device provided on the upper revolving body 3. The control device is, for example, a solenoid valve that controls the operation of the upper hydraulic device 73 or a controller that controls the operation of the upper electric device 64.

[0041] In addition to signals, the low-voltage system 5 may also send, for example, information regarding the operation of a device installed on the upper rotating body 3, and / or a current below a specified voltage to be supplied to the device, from the lower running body 2 to the upper rotating body 3.

[0042] Next, a description will be given of the high-power system 6. The high-power system 6 is a system for running the lower traveling body 2 and performing operations other than running (for example, crane work, air conditioning, and / or heating) based on power supplied from the high-power battery 60.

[0043] As shown in FIG. 2 , the high-power system 6 includes a high-power battery 60 , a traction motor 63 , a transmission member 4 , an upper electric device 64 , and a control unit 65 .

[0044] The high-power battery 60 is an example of a power supply unit, and as shown in Figure 3, has multiple batteries 601a, 601b. The batteries 601a, 601b are arranged outside (specifically, above) the frame 20. The high-power battery 60 also has multiple batteries (not shown) arranged in the battery housing space 201 of the frame 20.

[0045] The travel motor 63 includes a front travel motor 631 and a rear travel motor 632. The front travel motor 631 and the rear travel motor 632 are provided below the frame 20 and between the front axle 22 and the rear axle 23.

[0046] The front traveling motor 631 is connected to the front axle 22. The front traveling motor 631 drives the front axle 22 based on the electric power supplied from the high-power battery 60.

[0047] The rear traveling motor 632 is connected to the rear axle 23. The rear traveling motor 632 drives the rear axle 23 based on the electric power supplied from the high-power battery 60.

[0048] The travel motors 63 (specifically, the front travel motor 631 and the rear travel motor 632) described above are driven by power supplied from the high-power battery 60 under the control of the control unit 65. When the travel motors 63 are driven, the lower travel unit 2 (mobile crane 1) is enabled to travel based on the power of the travel motors 63. The power of the high-power battery 60 is sent to the upper rotating unit 3 via the transmission member 4.

[0049] The transmission member 4 constitutes an electric path for supplying electric power from the high-power battery 60 to the upper electric device 64 between the lower traveling body 2 and the upper rotating body 3, which rotate relative to each other. The upper electric device 64 is a device provided on the upper rotating body 3, and operates based on electric power from the high-power battery 60. The upper electric device 64 is, for example, a heating compressor provided on the upper rotating body 3.

[0050] When the swing actuator is an electric motor, the swing electric motor is an example of an upper electric device. When the winch actuator is an electric motor, the winch electric motor is an example of an upper electric device. In this case, the transmission member 4 is connected to the swing electric motor and the winch electric motor via an upper junction box (not shown). This upper junction box has the function of allocating the power of the high-power battery 60 supplied via the transmission member 4 to the swing electric motor and the winch electric motor.

[0051] When power is supplied from the high-power battery 60, the electric motor for rotation is driven by the power. The electric motor for rotation rotates the upper rotating body 3. When power is supplied from the high-power battery 60, the electric motor for winch is driven by the power. The electric motor for winch rotates the winch (not shown). As a result, the wire rope 36 is wound up or unwound, and the hook 37 is raised or lowered.

[0052] Next, a description will be given of the hydraulic system 7. The hydraulic system 7 is a system for supplying hydraulic oil to a lower hydraulic device 72 provided on the lower traveling body 2 and an upper hydraulic device 73 provided on the upper rotating body 3.

[0053] The lower hydraulic device 72 includes, for example, a hydraulic cylinder that constitutes a suspension and / or a hydraulic cylinder that constitutes an outrigger. The lower hydraulic device 72 may also include a hydraulic cylinder that constitutes a steering device.

[0054] The upper hydraulic device 73 also includes a rotation actuator (not shown), a hoisting cylinder 34, an extension cylinder 35, and a winch actuator (not shown). The upper hydraulic device 73 may also include an actuator for moving the jib.

[0055] The hydraulic system 7 includes a tank 71, a hydraulic oil supply device 8, and a transmission member 4. The hydraulic system 7 also includes a lower hydraulic device 72 and an upper hydraulic device 73. The elements that make up the hydraulic system 7 are connected by a circuit shown by a thick line in FIG.

[0056] The tank 71 and the hydraulic oil supply device 8 are provided on the lower traveling body 2. Specifically, as shown in Fig. 3 , the tank 71 and the hydraulic oil supply device 8 are disposed between the front axle 22 and the rear axle 23, and in a predetermined region on the side of the frame 20 in the left-right direction (on the left side in this embodiment).

[0057] The tank 71 is an example of a hydraulic oil tank, and is a tank for storing hydraulic oil, and is a substantially rectangular box-shaped tank. As shown in Figure 4, the tank 71 is disposed to the side of the transmission member 4 (on the left side in this embodiment).

[0058] The tank 71 and the hydraulic oil supply device 8 are arranged side by side in the front-to-rear direction in the above-mentioned predetermined area. The tank 71 is arranged forward of the hydraulic oil supply device 8. The tank 71 and the hydraulic oil supply device 8 are fixed to the side surface of the frame 20 (the left side surface in this embodiment).

[0059] The hydraulic oil supply device 8 is provided on the side (rear in this embodiment) of the tank 71. The hydraulic oil supply device 8 has an electric motor 80, a reducer 81, and a pump 82.

[0060] The electric motor 80 is an example of a pump motor. The reducer 81 is provided on one axial side (the front side in this embodiment) of the electric motor 80. In this embodiment, the axial direction of the electric motor 80 is parallel to the front-to-rear direction. However, the axial direction of the electric motor 80 may be inclined relative to the front-to-rear direction within a horizontal plane.

[0061] The reducer 81 reduces the rotation speed of the electric motor 80 and transmits the reduced speed to the pump 82. The electric motor 80 and the pump 82 (first pump 820 and second pump 821) are provided on opposite sides of the reducer 81 in the front-to-rear direction. Specifically, the pump 82 (first pump 820 and second pump 821) is provided in front of the reducer 81. The electric motor 80 is provided behind the reducer 81. The pump 82 corresponds to an example of a first pump unit. The electric motor 80 is driven by power supplied from the high-power battery 60 via an inverter 83 (see FIG. 2 ).

[0062] The inverter 83 is provided between the tank 71 and the hydraulic oil supply device 8 in the front-rear direction.

[0063] The reducer 81 reduces the rotation of the electric motor 80 at a predetermined reduction ratio and transmits the rotation to the pump 82 .

[0064] The pump 82 is an example of a pump unit, and operates based on rotation transmitted from the electric motor 80. The pump 82 has a first pump 820 (see FIG. 4) and a second pump 821. The first pump 820 and the second pump 821 are arranged in parallel. In other words, the central axis of the first pump 820 and the central axis of the second pump 821 are parallel to each other.

[0065] The central axes of the first pump 820 and the second pump 821 are parallel to the front-rear direction. The central axes of the first pump 820 and the second pump 821 are parallel to the central axis of the electric motor 80. The central axes of the first pump 820 and the second pump 821 may be inclined with respect to the front-rear direction in a horizontal plane. In this case, too, the central axes of the first pump 820 and the second pump 821 may be parallel to the central axis of the electric motor 80.

[0066] The first pump 820 and the second pump 821 are each connected to the tank 71 via a discharge hose 88a. The discharge hose 88a extends from the tank 71 toward the pump 82.

[0067] The hydraulic oil flowing out of the tank 71 passes through the discharge hose 88 a and flows into the first pump 820 and the second pump 821 .

[0068] The first pump 820 corresponds to an example of a main pump, and is driven based on the rotation of the electric motor 80 to supply hydraulic oil to a first driven part.

[0069] The first pump 820 is a variable displacement pump whose discharge volume can be changed. In this embodiment, the first pump 820 has two operating modes: a first mode in which the discharge volume is a first discharge volume, and a second mode in which the discharge volume is a second discharge volume. The discharge volume of the first pump 820 in the first mode is smaller than the discharge volume of the first pump 820 in the second mode.

[0070] The displacement of the first pump 820 in the first mode is the minimum displacement of the first pump 820. The displacement of the first pump 820 in the second mode is the maximum displacement of the first pump 820.

[0071] In the present embodiment, the first driven part is an upper first hydraulic device 730 (see FIG. 2) included in the upper hydraulic device 73.

[0072] The upper first hydraulic device 730 is a hydraulic device that is driven during crane operation, and includes the hoisting cylinder 34, the extension cylinder 35, and a winch actuator (not shown). The upper first hydraulic device 730 may also include an actuator for moving the jib. The first driven part also includes a hydraulic cylinder for the outrigger included in the lower hydraulic device 72.

[0073] When supplying hydraulic oil to the upper first hydraulic device 730, the first pump 820 sends the hydraulic oil to the transmission member 4. In the present embodiment, in the crane operating state, the first pump 820 is constantly driven to supply hydraulic oil to the upper first hydraulic device 730.

[0074] The transmission member 4 forms a flow path for fluid (e.g., hydraulic oil and / or compressed air) supplied from the lower running body 2 to the upper rotating body 3 between the lower running body 2 and the upper rotating body 3 which rotate relative to each other.

[0075] Specifically, the transmission member 4 forms part of a flow path that transmits hydraulic oil supplied from the hydraulic oil supply device 8 (first pump 820) to the upper hydraulic device 73 provided on the upper rotating body 3.

[0076] The hydraulic oil used in the upper first hydraulic device 730 passes through the transmission member 4 and returns to the tank 71. The transmission member 4 also forms part of a flow path for the hydraulic oil returning from the upper rotating body 3 to the lower traveling body 2.

[0077] The first pump 820 and the transmission member 4 are connected via a discharge hose 88b (see FIG. 4).

[0078] Furthermore, if the winch actuator (not shown), the elevation cylinder 34, and the extension cylinder 35 are provided in hydraulic circuits that are independent of each other, the first pump 820 may be composed of multiple independent pumps corresponding to each hydraulic circuit.

[0079] The second pump 821 is an example of a sub-pump, and is driven based on the rotation of the electric motor 80 to supply hydraulic oil to the second driven part. In this embodiment, the second pump 821 is a pump smaller than the first pump 820. In other words, the discharge rate of the second pump 821 is smaller than the discharge rate of the first pump 820.

[0080] In this embodiment, the second driven part is an upper second hydraulic device 731 (see FIG. 2 ) included in the upper hydraulic device 73. The upper second hydraulic device 731 includes a rotation actuator (not shown) and an Orbitroll (registered trademark) that constitutes a steering device. The Orbitroll is attached to the handle of the crane and is a hydraulic device that supplies pressure oil to a hydraulic cylinder provided on the lower traveling body 2.

[0081] When the hydraulic oil is supplied to the upper second hydraulic device 731, the second pump 821 sends the hydraulic oil to the transmission member 4. The transmission member 4 constitutes part of a flow path that transmits the hydraulic oil supplied from the hydraulic oil supply device 8 (second pump 821) to the upper second hydraulic device 731 provided on the upper rotating body 3.

[0082] The hydraulic oil used in the upper second hydraulic device 731 passes through the transmission member 4 and returns to the tank 71. The transmission member 4 also forms a flow path for the hydraulic oil returning from the upper rotating body 3 to the lower traveling body 2.

[0083] The second pump 821 and the transmission member 4 are connected via a discharge hose 88c (see FIG. 4). In FIG. 4, the discharge hose 88b and the discharge hose 88c are shown as a single discharge hose for the sake of convenience, but the discharge hose 88b and the discharge hose 88c are actually independent discharge hoses.

[0084] In this embodiment, the first pump 820 and the second pump 821 both operate. However, the first pump 820 and the second pump 821 may also operate independently of each other. That is, the first pump 820 may operate when the first driven part requires hydraulic oil, and the first pump 820 may stop when the first driven part does not require hydraulic oil. Furthermore, the second pump 821 may operate when the second driven part requires hydraulic oil, and the second pump 821 may stop when the second driven part does not require hydraulic oil.

[0085] Alternatively, when the first driven part does not require hydraulic oil, the output of the first pump 820 may be set to a predetermined value or less. Also, when the second driven part does not require hydraulic oil, the output of the second pump 821 may be set to a predetermined value or less. This configuration can reduce power consumption, thereby achieving energy savings.

[0086] Next, we will explain the regenerative braking control performed in the mobile crane 1. When decelerating while traveling, the mobile crane 1 performs regenerative braking control, in which regenerative power generated by the traveling motor 63 is supplied to the high-power battery 60 to generate braking force.

[0087] Specifically, when the driver releases the accelerator pedal while the mobile crane 1 is traveling, the rotation of the front tires 24 and rear tires 25 is transmitted to the traveling motor 63, generating regenerative power in the traveling motor 63 (specifically, the front traveling motor 631 and the rear traveling motor 632).

[0088] Then, a braking force equivalent to the regenerative power generated by the travel motors 63 (specifically, the front travel motor 631 and the rear travel motor 632) acts on the front tires 24 and the rear tires 25, slowing down the mobile crane 1.

[0089] In the case of this embodiment, in the regenerative braking control, the regenerative power generated by the traction motor 63 is basically supplied to the high-power battery 60. This type of control in the regenerative braking control is called normal regenerative braking control.

[0090] In the regenerative braking control, depending on the remaining battery charge of the high-power system battery 60, the high-power system battery 60 may not be able to accept all of the regenerative power.

[0091] If the high-power battery 60 cannot accept regenerative power and cannot consume the regenerative power generated by the travel motor 63, it may not be possible to obtain braking force to decelerate the mobile crane 1.

[0092] Therefore, in the case of this embodiment, in the regenerative braking control, when the remaining battery charge of the high-power system battery 60 is greater than a predetermined value, the mobile crane 1 distributes regenerative power to the hydraulic oil supply device 8. This type of control in the regenerative braking control is called regenerative power compensation control.

[0093] In addition, in the case of this embodiment, the mobile crane 1 changes the power consumed by the hydraulic oil supply device 8 in accordance with the remaining battery charge of the high-power system battery 60 during regenerative power compensation control.

[0094] The regenerative power compensation control performed in the regenerative braking control will be described below with reference to Fig. 5. Fig. 5 is a flowchart of the regenerative power compensation control. The regenerative braking control and the regenerative power compensation control are performed by the control unit 65. Therefore, the control processing performed in the regenerative braking control and the regenerative power compensation control is mainly performed by the control unit 65.

[0095] A regenerative braking device is configured by the control unit 65, the high-power battery 60, and the hydraulic oil supply device 8. In the following description, the term "electric power" may be replaced with the term "current."

[0096] First, in step S101 of FIG. 5, the control unit 65 calculates the required regenerative power P Ｆ Required regenerative power P Ｆ is the sum of the electric power corresponding to the braking force to be applied to the front tires 24 (in other words, the front axle 22) and the electric power corresponding to the braking force to be applied to the rear tires 25 (in other words, the rear axle 23). Ｆ is also the regenerative power generated by the traction motor 63 during regenerative braking control.

[0097] The electric power equivalent to the braking force to be applied to the front tires 24 is the electric power that the front running motor 631 should generate based on the rotation transmitted from the front tires 24 to the front running motor 631 (hereinafter referred to as the front required regenerative power).

[0098] In addition, the electric power equivalent to the braking force to be applied to the rear tires 25 is the electric power that the rear running motor 632 should generate based on the rotation transmitted from the rear tires 25 to the rear running motor 632 (hereinafter referred to as rear required regenerative power).

[0099] Therefore, the required regenerative power P Ｆ is the sum of the front required regenerative power and the rear required regenerative power. The front required regenerative power and the rear required regenerative power are calculated based on the vehicle speed of the mobile crane 1 and the required braking force corresponding to the vehicle speed.

[0100] In this embodiment, the control unit 65 stores a first table (not shown) that associates vehicle speed with required braking force (hereinafter referred to as front required braking force). The vehicle speed in the first table corresponds to the rotation speed of the front traveling motor 631.

[0101] The control unit 65 also stores a second table (not shown) that associates vehicle speed with required braking force (hereinafter referred to as rear required braking force). The vehicle speed in the second table corresponds to the rotation speed of the rear traveling motor 632.

[0102] The control unit 65 obtains from the first table the front required braking force corresponding to the vehicle speed of the mobile crane 1 in the traveling state. The control unit 65 then calculates the front required regenerative power based on the vehicle speed and the front required braking force obtained from the first table. In this way, the front required regenerative power varies depending on the vehicle speed of the mobile crane 1 in the traveling state.

[0103] The control unit 65 also obtains from the second table the required rear braking force corresponding to the vehicle speed of the mobile crane 1 in the traveling state. The control unit 65 then calculates the required rear regenerative power based on the vehicle speed and the required rear braking force obtained from the second table. In this way, the required rear regenerative power varies depending on the vehicle speed of the mobile crane 1 in the traveling state.

[0104] Next, in step S102 of FIG. 5, the control unit 65 calculates the power P to be consumed in the hydraulic oil supply device 8. ｅＰＴＯ (Hereinafter, the first power consumption P ｅＰＴＯ ) is calculated.

[0105] First power consumption P ｅＰＴＯ is calculated by the following formula (1): Ｆ is the required regenerative power. ６０ is the chargeable power of the high-power system battery 60. The chargeable power of the high-power system battery 60 may be considered as the power that can be received by the high-power system battery 60 at that time (i.e., at the time when the process of step S102 is performed).

[0106] P α is the power consumed at that time by a device that operates based on the power of the high-power system battery 60. The chargeable power of the high-power system battery 60 may be considered to be the power that the high-power system battery 60 can accept, which is determined according to the remaining battery charge of the high-power system battery 60. Note that the chargeable power of the high-power system battery 60 can also be considered to be the power that the high-power system battery 60 can accept, which is determined according to the temperature of the high-power system battery 60.

[0107]

[0108] Next, in step S103 of FIG. 5, the control unit 65 calculates the first power consumption P ｅＰＴＯ Determine whether is greater than zero.

[0109] First power consumption P ｅＰＴＯWhen the first power consumption P is greater than zero, the remaining charge of the high-power system battery 60 is greater than a predetermined value, and all of the requested regenerative power cannot be charged to the high-power system battery 60. ｅＰＴＯ When the remaining charge of the high-power system battery 60 is equal to or less than a predetermined value, all of the required regenerative power can be charged into the high-power system battery 60 .

[0110] The control unit 65 determines the first power consumption P ｅＰＴＯ is greater than zero (YES in step S103), the control process proceeds to step S104. That is, in this embodiment, if the remaining charge of the high-power system battery 60 is greater than a predetermined value, the control process proceeds to step S104.

[0111] As described above, in this embodiment, the regenerative power generated by the traveling motor 63 is distributed to the hydraulic oil supply device 8 according to the chargeable power of the high-power battery 60. Specifically, in this embodiment, when the remaining charge of the high-power battery 60 is greater than a predetermined value, the regenerative power compensation control distributes the regenerative power generated by the traveling motor 63 to the hydraulic oil supply device 8.

[0112] On the other hand, the control unit 65 determines the first power consumption P ｅＰＴＯ If the answer is "NO" in step S103, the control unit 65 terminates the regenerative power compensation control. That is, the control unit 65 supplies the regenerative power generated by the traction motor 63 to the high-power battery 60 through normal regenerative braking control.

[0113] Next, in step S104 of Fig. 5, the control unit 65 determines whether the temperature of the hydraulic oil is equal to or lower than a predetermined threshold value. The predetermined threshold value is, for example, 85°C. The predetermined threshold value may be set appropriately depending on the type of hydraulic oil or the operating environment.

[0114] If the temperature of the hydraulic oil is equal to or lower than the predetermined threshold value ("YES" in step S104), the control unit 65 advances the control process to step S105.

[0115] If the temperature of the hydraulic oil is higher than the predetermined threshold (NO in step S104), the control unit 65 ends the regenerative power compensation control. If the temperature of the hydraulic oil is higher than the predetermined threshold, the control unit 65 ends the regenerative brake control.

[0116] Therefore, no braking force is generated based on the regenerative braking control. In this case, the driver operates the foot brake to apply a braking force to the mobile crane 1, thereby slowing down the mobile crane 1. Note that when the control unit 65 terminates the regenerative braking control, it may notify the driver of this.

[0117] Furthermore, when the temperature of the hydraulic oil is higher than a predetermined threshold value ("NO" in step S104), the control unit 65 may control the cooling device 86, which will be described later, to cool the hydraulic oil in the tank 71. During this time, the control unit 65 may repeat the operation of step S104.

[0118] As described above, in this embodiment, the control unit 65 uses the hydraulic oil temperature condition as one of the conditions for starting regenerative power compensation control. However, the condition for starting regenerative power compensation control is not limited to the hydraulic oil temperature condition. The condition for starting regenerative power compensation control may include various conditions depending on the state of the mobile crane 1.

[0119] Next, in step S105 of Fig. 5, the control unit 65 performs a pump displacement change process. The pump displacement change process is a process for switching the displacement of the first pump 820 from the first displacement to the second displacement.

[0120] As described above, the first pump 820 has two operating modes: a first mode in which the displacement is a first displacement, and a second mode in which the displacement is a second displacement. The displacement of the first pump 820 in the first mode is smaller than the displacement of the first pump 820 in the second mode.

[0121] When the mobile crane 1 is traveling and normal regenerative braking control is being performed, the first pump 820 operates in the first mode. Therefore, the power consumed by the first pump 820 (in other words, the hydraulic oil supply device 8) is relatively small. This configuration contributes to energy conservation.

[0122] On the other hand, when regenerative power compensation control is performed while the mobile crane 1 is traveling, it is desirable that the power consumed by the hydraulic oil supply device 8 be large. Therefore, in step S105, the control unit 65 switches the mode of the first pump 820 from the first mode to the second mode, thereby increasing the discharge rate of the first pump 820. When the discharge rate of the first pump 820 increases, the power consumed by the hydraulic oil supply device 8 increases.

[0123] 5, the control unit 65 performs a return circuit switching process. The return circuit switching process is a process for switching the return circuit through which the hydraulic oil discharged from the first pump 820 passes when returning to the tank 71.

[0124] When the mobile crane 1 is in a traveling state, the hydraulic oil discharged from the first pump 820 is not supplied to the upper first hydraulic device 730, but passes through the return circuit 85 (see FIG. 2) and returns to the tank 71. The first pump 820 is constantly driven when the mobile crane 1 is in a traveling state.

[0125] The return circuit 85 has a low load return circuit 851 and a high load return circuit 852. The return circuit 85 (the low load return circuit 851 and the high load return circuit 852) may be regarded as elements of the hydraulic oil supply device 8.

[0126] The load pressure in the low-load return circuit 851 is relatively small. That is, when the hydraulic oil discharged from the first pump 820 is supplied to the low-load return circuit 851, the load torque acting on the first pump 820 (in other words, the electric motor 80) is small.

[0127] The state in which the hydraulic oil discharged from the first pump 820 returns to the tank 71 through the low-load return circuit 851 is referred to as the low-load return state (in other words, unloaded state) of the first pump 820. In the low-load return state, the load torque acting on the first pump 820 (in other words, the electric motor 80) is small, and therefore the power consumed by the hydraulic oil supply device 8 is small.

[0128] On the other hand, the high load return circuit 852 has a pressure regulating valve 852 a. The pressure regulating valve 852 a is, for example, a relief valve. The load pressure in the high load return circuit 852 is higher than the load pressure in the low load return circuit 851.

[0129] That is, in a state in which the hydraulic oil discharged from the first pump 820 is supplied to the high-load return circuit 852, the load torque acting on the first pump 820 (in other words, the electric motor 80) is large.

[0130] A state in which the hydraulic oil discharged from the first pump 820 returns to the tank 71 through the high-load return circuit 852 is referred to as a high-load return state of the first pump 820. In the high-load return state, the load torque acting on the first pump 820 (in other words, the electric motor 80) is large, and therefore the power consumed by the hydraulic oil supply device 8 is large.

[0131] In this embodiment, when normal regenerative braking control is being implemented while the mobile crane 1 is traveling, the hydraulic oil discharged from the first pump 820 returns to the tank 71 through the low-load return circuit 851.

[0132] In other words, when the mobile crane 1 is traveling and normal regenerative braking control is being performed, the first pump 820 is in a low-load return state. As described above, the load pressure within the low-load return circuit 851 is relatively low. Therefore, the power consumed by the hydraulic oil supply device 8 is small. This configuration contributes to energy savings.

[0133] On the other hand, when regenerative power compensation control is performed while the mobile crane 1 is traveling, it is desirable that the power consumed by the hydraulic oil supply device 8 be large. Therefore, in step S106, the control unit 65 switches the return circuit through which the hydraulic oil discharged from the first pump 820 returns to the tank 71 from the low-load return circuit 851 to the high-load return circuit 852.

[0134] As described above, the load pressure in the high-load return circuit 852 is higher than the load pressure in the low-load return circuit 851. Therefore, when the hydraulic oil discharged from the first pump 820 is supplied to the high-load return circuit 852, the load torque acting on the first pump 820 (in other words, the electric motor 80) is large. Therefore, the power consumed by the hydraulic oil supply device 8 is also large.

[0135] As described above, in this embodiment, the control unit 65 increases the power consumed by the hydraulic oil supply device 8 in two stages by performing the pump capacity change process in step S105 and the return circuit switching process in step S106.

[0136] Depending on the amount of power that the hydraulic oil supply device 8 is to consume, the pump capacity changing process and / or the return circuit switching process may be omitted.

[0137] Next, in step S107 of Fig. 5, the control unit 65 performs a rotation speed change process. The rotation speed change process is a process for changing the rotation speed of the first pump 820 (in other words, the electric motor 80).

[0138] In other words, the rotation speed change process is a process that changes the power consumed by the hydraulic oil supply device 8 by changing the rotation speed of the first pump 820 (in other words, the electric motor 80) depending on the remaining battery charge.

[0139] In the rotation speed change process, the control unit 65 increases the rotation speed of the first pump 820 (in other words, the electric motor 80 ) as the remaining battery charge increases, thereby increasing the amount of power that can be consumed by the hydraulic oil supply device 8 .

[0140] Specifically, the control unit 65 calculates the rotation speed of the first pump 820 based on the first power consumption P ｅＰＴＯ The rotation speed N corresponding to ｅＰＴＯ (hereinafter referred to as the first rotation speed N ｅＰＴＯ (hereinafter referred to as "(the first parameter)").

[0141] First rotation speed N ｅＰＴＯ is calculated by the following formula (2): ｅＰＴＯ is the first power consumption calculated in step S104.８０ is the motor efficiency of the electric motor 80. The motor efficiency of the electric motor 80 is a value that is set in advance depending on the electric motor 80. T ８０ is the motor shaft torque of the electric motor 80. The motor shaft torque of the electric motor 80 is a value that is set in advance according to the load torque acting on the first pump 820 and the reduction ratio of the reducer 81 (see FIG. 2 ).

[0142]

[0143] Then, the control unit 65 sets the first rotation speed N ｅＰＴＯ Then, the first pump 820 is driven.

[0144] As described above, the control unit 65 calculates the first power consumption P ｅＰＴＯ First rotation speed N according to ｅＰＴＯ is set as the rotation speed of the first pump 820. That is, the first power consumption P ｅＰＴＯ is a value according to the remaining battery charge of the high-power system battery 60. As shown in the above formula (2), the first rotation speed N ｅＰＴＯ is the first power consumption P ｅＰＴＯ In other words, the first rotation speed N ｅＰＴＯ is set based on the remaining battery capacity of the high-power system battery 60.

[0145] As a result of the above-described rotation speed change process, the first consumed power P ｅＰＴＯ The regenerated power corresponding to the first power consumption P ｅＰＴＯ The regenerative power generated by the driving motor 63 is calculated by the control unit 65 in step S101. Ｆ is equal to.

[0146] Furthermore, even if the remaining battery charge of the high-power system battery 60 is greater than a predetermined value, the high-power system battery 60 may be able to receive a certain amount of regenerative power. In this case, the regenerative power generated by the traction motor 63 that the high-power system battery 60 can receive is distributed to the high-power system battery 60.

[0147] On the other hand, the regenerated power generated by the traveling motor 63 that cannot be accepted by the high-power battery 60 is distributed to the hydraulic oil supply device 8 as described above. The power that cannot be accepted by the high-power battery 60 is divided into the power P calculated by the control unit 65 in step S102. ｅＰＴＯ is.

[0148] The smaller the remaining battery charge of the high-power system battery 60, the larger the regenerative power that can be received by the high-power system battery 60. Therefore, the smaller the remaining battery charge of the high-power system battery 60, the smaller the regenerative power distributed to the hydraulic oil supply device 8.

[0149] On the other hand, the greater the remaining battery charge of the high-power system battery 60, the smaller the regenerative power that can be received by the high-power system battery 60. Therefore, the greater the remaining battery charge of the high-power system battery 60, the greater the regenerative power distributed to the hydraulic oil supply device 8.

[0150] The regenerative power distributed to the hydraulic oil supply device 8 is consumed in the hydraulic oil supply device 8 as described above. Specifically, the regenerative power supplied to the hydraulic oil supply device 8 passes through the inverter 83 and flows into the electric motor 80. Then, the electric motor 80 is driven.

[0151] When the electric motor 80 is driven, the first pump 820 is driven via the reducer 81, and hydraulic oil is discharged from the first pump 820. In the case of this embodiment, when the mobile crane 1 is in a traveling state, the hydraulic oil discharged from the first pump 820 is not supplied to the upper first hydraulic device 730, but returns to the tank 71 through the high-load return circuit 852.

[0152] At this time, the regenerative electric power supplied to the hydraulic oil supply device 8 is converted into kinetic energy of the first pump 820. Then, the kinetic energy of the first pump 820 is converted into kinetic energy of the hydraulic oil discharged from the first pump 820.

[0153] Furthermore, the kinetic energy of the hydraulic oil is converted into thermal energy in the high-load return circuit 852. In other words, the regenerative power distributed to the hydraulic oil supply device 8 is consumed mainly by being converted into thermal energy in the high-load return circuit 852.

[0154] In this embodiment, in the pump displacement change process in step S105, the mode of the first pump 820 is changed so that the load torque acting on the first pump 820 increases.

[0155] In addition, in the return circuit switching process of step S106, the return circuit through which the hydraulic oil discharged from the first pump 820 returns to the tank 71 is set to a high-load return circuit 852 so that the load torque acting on the first pump 820 is increased.

[0156] Furthermore, in the rotation speed change process of step S107, the rotation speed of the first pump 820 is changed to the first power consumption P ｅＰＴＯ The first rotation speed N corresponding to ｅＰＴＯ is set to.

[0157] Therefore, the regenerative electric power supplied to the hydraulic oil supply device 8 can be consumed in the hydraulic oil supply device 8 .

[0158] The hydraulic oil supply device 8 may also include a cooling device 86 that cools the hydraulic oil. The cooling device 86 cools the hydraulic oil in the tank 71 when the temperature of the hydraulic oil exceeds a predetermined temperature while the mobile crane 1 is traveling. The location of the cooling device 86 is not particularly limited. The cooling device 86 may be disposed in a position where it can cool the hydraulic oil.

[0159] (Operations and Effects of the Present Embodiment) According to the mobile crane 1 of the present embodiment having the above-described configuration, it is possible to provide a crane that can travel using electricity.

[0160] In particular, according to the mobile crane 1 of this embodiment, appropriate regenerative braking control can be performed according to the remaining battery charge of the high-power system battery 60.

[0161] Specifically, in the regenerative braking control, when the remaining battery charge of the high-power battery 60 is greater than a predetermined value, the control unit 65 distributes the regenerative power generated by the traveling motor 63 to the hydraulic oil supply device 8. Therefore, even when the remaining battery charge of the high-power battery 60 is high, the regenerative braking control can be performed.

[0162] Furthermore, the control unit 65 changes the power consumed by the hydraulic oil supply device in accordance with the remaining battery charge of the high-power battery 60. Therefore, the regenerative power generated by the travel motor 63 and supplied to the hydraulic oil supply device 8 can be reliably consumed by the hydraulic oil supply device 8. As a result, regenerative braking control can be stably performed regardless of the remaining battery charge of the high-power battery 60.

[0163] Furthermore, the regenerative power generated by the travel motor 63 and supplied to the hydraulic oil supply device 8 is converted into thermal energy of the hydraulic oil in the hydraulic oil supply device 8 and consumed. The mobile crane 1 is equipped with many hydraulic devices used during crane operation. Therefore, the mobile crane 1 has a large amount of hydraulic oil. Therefore, the hydraulic oil can accept a large amount of thermal energy. In other words, the hydraulic oil supply device 8 can accept a large amount of regenerative power in regenerative power compensation control. Other functions and effects achieved by the mobile crane 1 according to this embodiment are as described above.

[0164] (Additional Note) The crane according to the present invention, including the above-described embodiment, distributes the regenerative power generated by the traveling motor 63 to the hydraulic oil supply device 8 in accordance with the chargeable power of the power source unit (specifically, the high-power battery 60) during regenerative braking control, and also performs regenerative power compensation control that changes the power consumed by the hydraulic oil supply device 8.

[0165] In the above embodiment, an example has been described in which regenerative power compensation control is performed based on the remaining battery charge of the high power system battery 60. In such an embodiment, the chargeable power of the high power system battery 60 is the power that can be accepted by the high power system battery 60, which is determined according to the remaining battery charge of the high power system battery 60.

[0166] However, the crane according to the present invention may also perform regenerative power compensation control based on the temperature of the power supply unit (specifically, the high-power battery 60). Specifically, in regenerative braking control, when the temperature of the high-power battery 60 satisfies a predetermined condition, the crane may distribute regenerative power generated by the travel motor 63 to the hydraulic oil supply device 8 and change the power consumed by the hydraulic oil supply device 8.

[0167] In this case, the chargeable power of the high-power system battery 60 is the power that the high-power system battery 60 can accept, which is determined according to the temperature of the high-power system battery 60 .

[0168] An example of a case where the temperature of the high-power system battery 60 satisfies a predetermined condition is when the temperature of the high-power system battery 60 is equal to or lower than a first predetermined temperature. When the temperature of the high-power system battery 60 is lower than the first predetermined temperature, the chargeable power of the high-power system battery 60 decreases. In such a situation, when regenerative power compensation control is performed, a portion of the regenerative power generated by the traction motor 63 can be consumed in the hydraulic oil supply device 8.

[0169] Furthermore, the case where the temperature of the high-power system battery 60 satisfies the predetermined condition is, for example, the case where the temperature of the high-power system battery 60 is equal to or higher than a second predetermined temperature. When the temperature of the high-power system battery 60 is equal to or higher than the second predetermined temperature, the chargeable power of the high-power system battery 60 decreases. In such a situation, when regenerative power compensation control is performed, part of the regenerative power generated by the travel motor 63 can be consumed in the hydraulic oil supply device 8.

[0170] The disclosures of the specification, drawings, and abstract contained in Japanese Patent Application No. 2023-203954, filed December 1, 2023, are incorporated herein by reference in their entirety.

[0171] The crane according to the present invention is not limited to a rough terrain crane, but may be any of various mobile cranes, such as an all-terrain crane, a truck crane, or a loaded truck crane (also called a cargo crane).

[0172] REFERENCE SIGNS LIST 1 Mobile crane 2 Undercarriage 20 Frame 200 Transmission member arrangement space 201 Battery storage space 202 Front outrigger support section 203 Rear outrigger support section 21 Body 22 Front axle 23 Rear axle 24 Front tire 25 Rear tire 26 Outrigger 26a Front outrigger 26b Rear outrigger 3 Upper rotating body 31 Swivel base 32 Telescopic boom 33 Cab 34 Raising and lowering cylinder 35 Telescopic cylinder 36 Wire rope 37 Hook 38 Winch 4 Transmission member 5 Low-voltage system 50 Lower controller 51 Upper controller 53 Low-voltage battery 6 High-voltage system 60 High-voltage battery 601a, 601b Battery 63 Travel motor 631 Front travel motor 632 Rear traveling motor 64 Upper electric device 65 Control unit 7 Hydraulic system 71 Tank 72 Lower hydraulic device 73 Upper hydraulic device 730 Upper first hydraulic device 731 Upper second hydraulic device 8 Hydraulic oil supply device 80 Electric motor 81 Reducer 82 Pump 820 First pump 821 Second pump 83 Inverter 85 Return circuit 851 Low load return circuit 852 High load return circuit 852a Pressure regulating valve 86 Cooling device 88a, 88b, 88c Discharge hose

Claims

1. A crane comprising: a traveling vehicle body having a traveling motor driven by a power supply unit; a hydraulic oil supply device driven by the power supply unit and supplying hydraulic oil to a driven unit; and a regenerative brake device that performs regenerative brake control to generate braking force by supplying regenerative power generated by the traveling motor to the power supply unit when the traveling vehicle body decelerates, wherein the regenerative brake device distributes the regenerative power to the hydraulic oil supply device in accordance with the chargeable power of the power supply unit and changes the power consumed by the hydraulic oil supply device during the regenerative brake control.

2. A crane as described in claim 1, wherein the chargeable power is power that can be accepted by the power supply unit and is determined according to the remaining battery charge of the power supply unit, and the regenerative braking device distributes the regenerative power to the hydraulic oil supply device in the regenerative braking control when the remaining battery charge of the power supply unit is greater than a predetermined value, and changes the power consumed by the hydraulic oil supply device according to the remaining battery charge.

3. A crane as described in claim 1, wherein the chargeable power is power that can be accepted by the power supply unit and is determined according to the temperature of the power supply unit, and the regenerative braking device distributes the regenerative power to the hydraulic oil supply device and changes the power consumed by the hydraulic oil supply device in the regenerative braking control when the temperature of the power supply unit satisfies a predetermined condition.

4. A crane as described in claim 2, wherein the hydraulic oil supply device has a pump motor driven by the power supply unit and a first pump unit driven by the pump motor, and the regenerative braking device changes the power consumed by the hydraulic oil supply device by changing the rotation speed of the pump motor according to the remaining battery charge.

5. The crane according to claim 4, wherein the regenerative braking device increases the rotation speed of the pump motor as the remaining battery charge increases, thereby increasing the amount of power that can be consumed by the hydraulic oil supply device.

6. The crane according to claim 4, wherein the regenerative braking device switches the discharge capacity of the first pump unit from minimum to maximum when distributing the regenerative power to the hydraulic oil supply device.

7. A crane as described in claim 4, wherein the regenerative braking device switches the hydraulic circuit through which the hydraulic oil passes from a hydraulic circuit in which a load torque acting on the first pump unit is low to a hydraulic circuit in which the load torque is high when distributing the regenerative power to the hydraulic oil supply device.

8. The crane according to claim 4, wherein the hydraulic oil supply device, in a crane operating state, drives the first pump unit constantly to supply the hydraulic oil to the driven parts, and, in a traveling state, drives the first pump unit constantly to return the hydraulic oil to the hydraulic oil tank without supplying it to the driven parts.

9. The crane according to claim 1, further comprising a cooling device for cooling the hydraulic oil when the temperature of the hydraulic oil exceeds a predetermined temperature during traveling.

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