WORKING MACHINE, CONTROL METHOD FOR A WORKING MACHINE, AND CONTROL VALVE DEVICE

Abstract

A control valve device (40) includes a first body (41) and a second body (42). The first body (41) includes a first control valve (V1). The first control valve (V1) enables the discharge of hydraulic oil flowing from a bottom chamber (16a) of a boom cylinder (16) during a lowering operation of a boom (14). The second body (42) includes a second control valve (V2). The second control valve (V2) enables the discharge of the hydraulic oil flowing from the bottom chamber (16a) of the boom cylinder (16) during the lowering operation of the boom (14) and enables communication of the accumulator (70) with the bottom chamber (16a) of the boom cylinder (16) during a predetermined operation other than the lowering operation or a raising operation of the boom (14).

Description

TECHNICAL FIELD

[0001] The present invention relates to a working machine, a control method for a working machine and a control valve device. STATE OF THE ART

[0002] It is known that a work machine (such as a wheel loader) is widely used, which includes a boom to which an attachment such as a bucket is attached, and a boom cylinder that drives the boom.

[0003] To increase the boom lifting capacity, it is preferable to increase the inner diameter of the boom cylinder. However, since the lowering speed of the boom is higher than the raising speed, an increased inner diameter of the boom cylinder significantly increases the flow rate of hydraulic oil flowing from a bottom chamber of the boom cylinder during boom lowering. Therefore, if the hydraulic oil flowing from the bottom chamber of the boom cylinder is discharged via a control valve, erosion may occur in the control valve.

[0004] Here, Patent Document 1 discloses a control valve device in which a boom valve body, a speed-increasing valve body, and a leveling valve body are stacked. The boom valve body includes a boom valve through which hydraulic oil flows from a bottom chamber of the boom cylinder during boom lowering, and an oil path for discharging the hydraulic oil. The speed-increasing valve body includes a boom valve through which hydraulic oil flows from a bottom chamber of the boom cylinder during boom lowering, and an oil path for discharging the hydraulic oil. The leveling valve body includes an oil path for connecting the bottom chamber of the boom cylinder to an accumulator during a predetermined operation other than boom lowering.

[0005] According to the control valve device described in Patent Document 1, since the hydraulic oil flowing from the bottom chamber of the boom cylinder can be discharged by means of two control valves, namely the boom valve and the speed increase valve, the occurrence of erosion in each of the control valves can be suppressed while still achieving a high flow rate of the discharged hydraulic oil. LIST OF CITATIONS Patent literature

[0006] Patent Document 1: WO 2005 / 035883 SUMMARY OF THE INVENTIONTechnical Problem

[0007] However, since the control valve device described in Patent Document 1 requires stacking three bodies, namely the boom valve body, the speed increasing valve body, and the leveling valve body, a large space is required to install the control valve device.

[0008] An object of the present disclosure is to provide a work machine, a control method for the work machine, and a control valve device, the work machine enabling a reduction in the size of a control valve. Solution to the problem

[0009] A work machine according to a first aspect of the present disclosure includes a hydraulic pump, a work implement having a boom, a hydraulic cylinder having a bottom chamber and a rod chamber and configured to drive the boom, a pressure surge suppressing mechanism configured to suppress pressure surges in the bottom chamber, and a control valve device configured to control a hydraulic oil flow between the hydraulic pump, the hydraulic cylinder, and the pressure surge suppressing mechanism. The control valve device includes a first body having a first control valve and a second body having a second control valve. The first control valve enables the discharge of the hydraulic oil flowing from the bottom chamber during a boom lowering operation.The second control valve allows the discharge of the hydraulic oil flowing from the bottom chamber during the boom lowering operation and allows the pressure fluctuation suppression mechanism to communicate with the bottom chamber during a predetermined operation other than the boom lowering operation or a boom raising operation. Advantageous effects of the invention

[0010] The present disclosure may provide a work machine, a control method for the work machine, and a control valve device, wherein the work machine enables a reduction in the size of a control valve. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a wheel loader. Fig. 2 is a schematic view illustrating a configuration of a hydraulic system. Fig. 3 is a schematic view illustrating a configuration of a hydraulic circuit. DESCRIPTION OF EMBODIMENTSOverview of the wheel loader 10

[0011] Fig. 1 is a side view illustrating a general configuration of a wheel loader 10 according to the present embodiment. The wheel loader 10 is an example of a "work machine" according to the present disclosure.

[0012] The wheel loader 10 includes a base body 1 and a working device 3. The base body 1 and the working device 3 form a vehicle body 20 of the wheel loader 10.

[0013] The main body 1 includes a vehicle body frame 2, a pair of front tires 4, a cab 5, an engine compartment 6, a pair of rear tires 7, and a steering cylinder 8. The vehicle body frame 2, the pair of front tires 4, and the pair of rear tires 7 form the traveling body of the wheel loader 10.

[0014] The vehicle body frame 2 is a so-called articulated frame. The vehicle body frame 2 includes a front frame 11, a rear frame 12, and a coupling shaft portion 13. The front frame 11 is arranged on the front side of the rear frame 12. The coupling shaft portion 13 rotatably connects the front frame 11 and the rear frame 12. The angle of the front frame 11 with respect to the rear frame 12 is adjusted by extending and retracting the articulated cylinder 8.

[0015] The pair of front tires 4 are mounted on the left and right sides of the front frame 11. The pair of rear tires 7 are mounted on the left and right sides of the rear frame 12. In this specification, the front, rear, left, and right directions are defined in a state where the angle of the front frame 11 with respect to the rear frame 12 is zero, that is, in a state where the front frame 11 and the rear frame 12 are arranged linearly. Specifically, left and right mean the left and right directions when viewed in the traveling direction (i.e., forward) from the cab 5.

[0016] The working device 3 is attached to the base body 1. The working device 3 is used for various types of work (such as loading work of earth and sand and unloading work of earth and sand). The working device 3 is driven by hydraulic oil discharged from a hydraulic pump 50 described below. The working device 3 includes a boom 14, a bucket 15, a pair of boom cylinders 16, a bucket cylinder 17, and a bell crank 18. The boom 14 is attached to the front frame 11 so as to be movable up and down. The bucket 15 is attached to a distal end of the boom 14.

[0017] The boom cylinder 16 and the bucket cylinder 17 are hydraulic cylinders for driving the work implement 3. The boom cylinders 16 are coupled to the front frame 11 and the boom 14. The boom cylinder 16 drives the boom 14. The boom 14 moves up and down by extending and retracting the boom cylinders 16. For example, the boom cylinders 16 are an example of a "hydraulic cylinder" according to the present disclosure. The bucket cylinder 17 is coupled to the front frame 11 and the bell crank 18. The bucket cylinder 17 drives the bucket 15 via the bell crank 18. When the bucket cylinder 17 extends and retracts, the bucket 15 moves up and down.

[0018] The cabin 5 is mounted on the rear frame 12. Inside the cabin 5, a steering wheel for steering, a control lever for operating the implement 3, various switches, a display, and the like, which are not illustrated, are arranged.

[0019] The engine compartment 6 is arranged on the rear frame 12 at the rear of the cab 5. An engine (not illustrated) is arranged in the engine compartment 6. A counterweight 6a is arranged behind the engine compartment 6. The counterweight 6a is arranged at a rear end portion of the rear frame 12. Hydraulic system 30

[0020] Fig. 2 is a schematic view illustrating a hydraulic system 30 of the wheel loader 10.

[0021] The hydraulic system 30 includes the boom cylinder 16, the bucket cylinder 17, a control valve device 40, the hydraulic pump 50, a hydraulic oil tank 60 and an accumulator 70.

[0022] The boom cylinder 16 includes a bottom chamber 16a and a rod chamber 16b. The bucket cylinder 17 includes a bottom chamber 17a and a rod chamber 17b.

[0023] The control valve device 40 controls the flow of hydraulic oil between the boom cylinder 16, the hydraulic pump 50, and the accumulator 70. The control valve device 40 controls the flow of hydraulic oil between the bucket cylinder 17 and the hydraulic pump 50.

[0024] The control valve device 40 includes a first body 41, a second body 42, and a third body 43. The first to third bodies 41 to 43 are stacked. In the present embodiment, the first body 41 is sandwiched between the second body 42 and the third body 43. The first and second bodies 41 and 42 contact each other at a mating surface F1. The first and third bodies 41 and 43 contact each other at a mating surface F2.

[0025] The first to third bodies 41 to 43 are configured as a block body. While the stacking direction of the first to third bodies 41 to 43 is not particularly limited, the stacking may be in the top-down direction, for example. When the first to third bodies 41 to 43 are stacked in the top-down direction, the second body 42 may be arranged on the uppermost level, or the third body 43 may be arranged on the uppermost level. The control valve device 40 may further include another body stacked on the first to third bodies 41 to 43.

[0026] In the present embodiment, the configuration in which the first body 41 and the second body 42 are stacked is an essential configuration, but the configuration in which the first body 41 and the third body 43 are stacked is an optional configuration.

[0027] The control valve device 40 is connected to the hydraulic oil tank 60 via a pipe P1. The control valve device 40 is connected to the hydraulic pump 50 via a pipe P2. The first body 41 is connected to the bottom chamber 16a of the boom cylinder 16 via a pipe P3 and is connected to the rod chamber 16b of the boom cylinder 16 via a pipe P4. The second body 42 is connected to the accumulator 70 via a pipe P5. The third body 43 is connected to the bottom chamber 17a of the bucket cylinder 17 via a pipe P6 and is connected to the rod chamber 17b of the bucket cylinder 17 via a pipe P7.

[0028] The hydraulic pump 50 delivers the hydraulic oil drawn from the hydraulic oil tank 60 to the control valve device 40. A hydraulic pump 50 is driven by the engine's drive force. A variable displacement gear pump, for example, can be used as the hydraulic pump 50.

[0029] The hydraulic oil tank 60 stores the hydraulic oil discharged from the control valve device 40. The hydraulic oil stored in the hydraulic oil tank 60 is sucked into the hydraulic pump 50.

[0030] The accumulator 70 is an example of a "pressure surge suppression mechanism" according to the present disclosure. The accumulator 70 stores the hydraulic oil. When the accumulator 70 is connected to the bottom chamber 16a of the boom cylinder 16, it suppresses pressure surges in the bottom chamber 16a. This dampens the vibration of the work implement 3. The accumulator 70 operates during a predetermined operation other than the lowering operation or the raising operation of the boom 14. The predetermined operation is mainly assumed to be a traveling operation of the wheel loader 10. However, if the accumulator 70 does not need to be operated even during traveling, the operation of the accumulator 70 can be stopped. The accumulator 70 can also be operated during an operation other than traveling if necessary.

[0031] Here shows Fig. 3 is a configuration diagram of a hydraulic circuit between the first and second bodies 41 and 42 and the boom cylinder 16, the hydraulic pump 50, the hydraulic oil tank 60, and the accumulator 70 in the control valve device 40.

[0032] The first body 41 includes a first control valve V1, a first discharge oil path L1, a second discharge oil path L2, a supply oil path L3, an intermediate oil path L4, a first flow oil path L5 and a second flow oil path L6.

[0033] The first control valve V1 is formed in the first body 41. The first control valve V1 controls the operation of the boom cylinder 16 by supplying the hydraulic oil discharged from the hydraulic pump 50 to the boom cylinder 16.

[0034] A pair of pilot chambers S1 and S2 are formed at both end portions of the first control valve V1. The pilot chambers S1 and S2 each receive a pilot pressure via a proportional pressure reducing valve (not illustrated) operated by an operation lever or the like. The first control valve V1 can be switched to three positions: a lowered position (D1), a neutral position (N1), and a raised position (U) by the pilot pressure acting on the control chambers S1 and S2 and the spring pressure acting on both ends of the first control valve V1. When the boom 14 is lowered, the first control valve V1 is switched from the neutral position (N1) to the lowered position (D1). When the boom 14 is raised, the first control valve V1 is switched from the neutral position (N1) to the raised position (U). When the accumulator 70 is operated, the first control valve V1 is held in the neutral position (N1).The proportional pressure reducing valve is controlled via a control unit (not shown).

[0035] The first discharge oil path L1 is connected to a first port A1 of the first control valve V1 and the pipe P1 connected to the hydraulic oil tank 60. The second discharge oil path L2 is connected to the first discharge oil path L1 and a discharge oil path M1 of the second body 42 described below. The second discharge oil path L2 opens into the mating surface F1. The supply oil path L3 is connected to a second port A2 of the first control valve V1 and the pipe P2 connected to the hydraulic pump 50.

[0036] The intermediate oil path L4 is connected to a third port A3 of the first control valve V1 and an intermediate oil path M2 of the second body 42 described below. The intermediate oil path L4 opens into the mating surface F1. The "intermediate oil path" according to the present disclosure includes the intermediate oil path L4 of the first body 41 and the intermediate oil path M2 of the second body 42.

[0037] The first flow oil path L5 is connected to the intermediate oil path L4 and the pipe P3 connected to the bottom chamber 16a of the boom cylinder 16. The second flow oil path L6 is connected to a fourth port A4 of the first control valve V1 and the pipe P4 connected to the rod chamber 16b of the boom cylinder 16.

[0038] The second body 42 includes a second control valve V2, a discharge oil path M1, an intermediate oil path M2 and a flow oil path M3.

[0039] The second control valve V2 is formed in the second body 42. The second control valve V2 discharges the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 and switches between communication and shutoff between the boom cylinder 16 and the accumulator 70. The operation of the accumulator 70 is controlled. A pair of pilot chambers S3 and S4 are formed at both end portions of the second control valve V2. The pilot chambers S3 and S4 each receive a pilot pressure via a proportional pressure reducing valve (not shown) operated by an operation lever or the like. The second control valve V2 can be switched to three positions: a lowered position (D2), a neutral position (N2), and a vibration control position (Y) by the pilot pressure acting on the control chambers S3 and S4 and the spring pressure acting on both ends of the second control valve V2.When the boom 14 is lowered, the second control valve V2 is switched from the neutral position (N2) to the lowered position (D2). When the boom 14 is raised, the second control valve V2 is held in the neutral position (N2). When the pressure accumulator 70 is operated, the second control valve V2 is switched from the neutral position (N2) to the vibration control position (Y). The proportional pressure reducing valve is controlled via a control unit (not shown).

[0040] The discharge oil path M1 is connected to a first port B1 of the second control valve V2 and the second discharge oil path L2 of the first body 41. The discharge oil path M1 opens into the mating surface F1.

[0041] The intermediate oil path M2 is connected to a second port B2 of the second control valve V2 and the intermediate oil path L4 of the first body 41. The intermediate oil path M2 opens into the mating surface F1. As described above, the "intermediate oil path" according to the present disclosure includes the intermediate oil path L4 of the first body 41 and the intermediate oil path M2 of the second body 42.

[0042] The flow oil path M3 is connected to a third port B3 of the second control valve V2 and the pipe P5 is connected to the pressure accumulator 70. Flow of hydraulic oil

[0043] The flow of hydraulic oil in the hydraulic system 30 is described with reference to Fig. 3 described.

[0044] When the boom 14 is raised, the first control valve V1 is switched from the neutral position (N1) to the raised position (U) and the second control valve V2 is held in the neutral position (N2).

[0045] The hydraulic oil discharged from the hydraulic pump 50 passes through the pipeline P2, the supply oil path L3 of the first body 41, the first control valve V1 (second port A2 -> third port A3), the intermediate oil path L4 and the first flow oil path L5 in sequence, and then reaches the bottom chamber 16a of the boom cylinder 16 through the pipeline P3.

[0046] The hydraulic oil flowed from the rod chamber 16b of the boom cylinder 16 passes sequentially through the pipeline P4, the second flow oil path L6 of the first body 41, the first control valve V1 (fourth port A4 -> first port A1) and the first discharge oil path L1, and is then discharged into the hydraulic oil tank 60 through the pipeline P1.

[0047] In this way, during the operation of lifting the boom 14, the hydraulic oil flowing from the rod chamber 16b of the boom cylinder 16 is discharged only through the first control valve V1 of the first body 41.

[0048] When lowering the boom 14, the first control valve V1 is switched from the neutral position (N1) to the lowered position (D1) and the second control valve V2 is switched from the neutral position (N2) to the lowered position (D2).

[0049] The hydraulic oil discharged from the hydraulic pump 50 passes through the pipe P2, the supply oil path L3 of the first body 41, the first control valve V1 (second port A2 -> fourth port A4) and the second flow oil path L6 in sequence, and then reaches the rod chamber 16b of the boom cylinder 16 through the pipe P4.

[0050] The hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 sequentially passes through the pipeline P3 and the first flow oil path L5 of the first body 41, and then flows into the intermediate oil path L4. The hydraulic oil flowing into the intermediate oil path L4 is distributed in two ways, namely, to the first control valve V1 side and the second control valve V2 side. The hydraulic oil distributed to the first control valve V1 side sequentially passes through the intermediate oil path L4, the first control valve V1 (third port A3 -> first port A1), and the first discharge oil path L1, and is then discharged into the hydraulic oil tank 60 through the pipeline P1. The hydraulic oil distributed to the second control valve V2 side flows from the intermediate oil path L4 into the intermediate oil path M2 of the second body 42.The hydraulic oil flowing into the intermediate oil path M2 of the second body 42 sequentially passes through the intermediate oil path M2, the second control valve V2 (second port B2 -> first port B1), and the discharge oil path M1, and then flows into the second discharge oil path L2 of the first body 41. The hydraulic oil flowing into the second discharge oil path L2 of the first body 41 sequentially passes through the second discharge oil path L2 and the first discharge oil path L1, and is then discharged into the hydraulic oil tank 60 through the piping P1.

[0051] As described above, during the lowering operation of the boom 14, the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 is discharged via the first control valve V1 of the first body 41 and the second control valve V2 of the second body 42. This step is an example of a "first step" according to the present disclosure. The flow rate of the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 during the lowering operation of the boom 14 is preferably higher than the flow rate of the hydraulic oil flowing from the rod chamber 16b of the boom cylinder 16 during the raising operation of the boom 14 described above. Accordingly, the hydraulic oil can be quickly discharged from the bottom chamber 16a of the boom cylinder 16, and thus, rapid lowering of the boom 14 can be achieved.

[0052] When the accumulator 70 is operated, the first control valve V1 is maintained in the neutral position (N1), and the second control valve V2 is switched from the neutral position (N2) to the vibration control position (Y). Accordingly, the bottom chamber 16a of the boom cylinder 16 and the accumulator 70 communicate with each other via the piping P3, the first flow oil path L5, the intermediate oil path L4, the intermediate oil path M2, the second control valve V2 (second port B2 -> third port B3), the flow oil path M3, and the piping P5. This dampens the vibration of the work implement 3. This step is an example of a "second step" according to the present disclosure. feature

[0053] The control valve device 40 according to the present embodiment includes the first body 41 and the second body 42. The first body 41 includes the first control valve V1. The first control valve V1 enables the discharge of hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 during the lowering operation of the boom 14. The second body 42 includes the second control valve V2. The second control valve V2 enables the discharge of the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 during the lowering operation of the boom 14 and enables the accumulator 70 to communicate with the bottom chamber 16a of the boom cylinder 16 during a predetermined operation other than the lowering operation or a raising operation of the boom 14.

[0054] Therefore, during the lowering operation of the boom 14, the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 can be quickly discharged by using not only the first control valve V1 of the first body 41 but also the second control valve V2 of the second body 42, which has not been used in conventional cases. Furthermore, since the second control valve V2 can be used to drive the accumulator 70 to discharge the hydraulic oil, it is not necessary to provide a speed-increasing valve body with a speed-increasing valve separately from a leveling valve body with a leveling valve, as disclosed in WO 2005 / 035883. Therefore, the control valve device 40 can be downsized.

[0055] Furthermore, since the hydraulic oil flowing from the bottom chamber 16a of the boom cylinder 16 can be distributed to the first and second control valves V1 and V2, it is possible to prevent the occurrence of erosion in each of the first and second control valves V1 and V2 while increasing the flow rate of the hydraulic oil to be discharged. Therefore, it is possible to avoid a reduction in the durability of the control valve device 40 even if the lifting force of the work machine 3 is increased by increasing the inner diameter of the boom cylinder 16.

[0056] Furthermore, the second body 42 according to the present embodiment can be manufactured by additionally forming a flow path (second port B2 -> first port B1) in a control valve for a known accumulator and additionally forming an oil path (discharge oil path M1) in a body that houses the control valve. Therefore, a known body for an accumulator can be used, thereby avoiding an increase in the manufacturing cost of the control valve device 40. Modification of the embodiment

[0057] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit of the invention. First modification

[0058] In the above embodiment, the wheel loader is described as an example of the work machine, but this should not be construed in a limiting sense. Examples of the work machine include, but are not limited to, a hydraulic excavator, a motor grader, and the like. Second modification

[0059] In the above embodiment, the first body 41 and the second body 42 are stacked, but this should not be interpreted in a limiting sense. Another body (for example, a body enclosing a vane control valve) may be interposed between the first body 41 and the second body 42. Third modification

[0060] In the above embodiment, the accumulator was described as an example of the pressure fluctuation suppression mechanism. However, this should not be construed in a limiting sense. The pressure fluctuation suppression mechanism can be any mechanism that can suppress the pressure fluctuation in the bottom chamber. Examples of the pressure fluctuation suppression mechanism include an oil path with an orifice, and the like. LIST OF REFERENCE SYMBOLS

[0061] 3 Working device, 10 Wheel loader, 14 Boom, 16 Boom cylinder, 30 Hydraulic system, 40 Control valve device, 41 First body, V1 First control valve, L1 First discharge oil path, L2 Second discharge oil path, L3 Feed oil path, L4 Intermediate oil path, L5 First flow oil path, L6 Second flow oil path, 42 Second body, V2 Second control valve, M1 Discharge oil path, M2 Intermediate oil path, M3 Flow oil path, 50 Hydraulic pump, 60 Hydraulic oil tank, 70 Accumulator QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2005 / 035883 [0006, 0054]

Claims

[1] Work machine, comprising: a hydraulic pump; a working device including a boom; a hydraulic cylinder having a bottom chamber and a rod chamber configured to drive the boom; a pressure fluctuation suppression mechanism configured to suppress pressure fluctuations in the bottom chamber; and a control valve device configured to control a flow of hydraulic oil between the hydraulic pump, the hydraulic cylinder and the pressure fluctuation suppression mechanism, wherein the control valve device includes: a first body including a first control valve that enables discharge of the hydraulic oil flowing from the bottom chamber during a lowering operation of the boom, and a second body including a second control valve that enables discharge of the hydraulic oil flowing from the bottom chamber during the boom lowering operation and that enables communication of the pressure fluctuation suppressing mechanism with the bottom chamber during a predetermined operation other than the boom lowering operation or the boom raising operation. [2] Working machine according to claim 1, wherein the first body and the second body are stacked and the control valve device includes an intermediate oil path configured to distribute the hydraulic oil flowing from the bottom chamber during the lowering operation of the boom to the first control valve and the second control valve. [3] The working machine according to claim 1 or 2, wherein a flow rate of the hydraulic oil flowing out of the bottom chamber during the lowering operation of the boom is higher than a flow rate of the hydraulic oil flowing out of the rod chamber during the raising operation of the boom. [4] Control method for a work machine, the method comprising: a first step of discharging hydraulic oil flowing from a bottom chamber of a hydraulic cylinder configured to drive a boom via a control valve device during a lowering operation of the boom; and a second step of causing a pressure fluctuation suppression mechanism configured to suppress pressure fluctuations in the bottom chamber to communicate with the bottom chamber via the control valve device during a predetermined operation other than the lowering operation or a lifting operation of the boom, wherein the control valve device includes: a first body including a first control valve that enables discharge of the hydraulic oil flowing from the bottom chamber in the first step; and a second body including a second control valve that enables discharge of the hydraulic oil flowing from the bottom chamber in the first step and enables communication of the pressure fluctuation suppression mechanism with the bottom chamber in the second step. [5] A control valve device configured to control a flow of hydraulic oil between a hydraulic pump, a hydraulic cylinder configured to drive a boom, and a pressure fluctuation suppressing mechanism configured to suppress pressure fluctuations in a bottom chamber of the hydraulic cylinder, the control valve device comprising: a first body including a first control valve that enables discharge of the hydraulic oil flowing from the bottom chamber during a lowering operation of the boom, and a second body enclosing the second control valve that enables discharge of the hydraulic oil flowing from the bottom chamber during the boom lowering operation and enables communication of the pressure fluctuation suppressing mechanism with the bottom chamber during a predetermined operation other than the boom lowering operation or a boom raising operation.

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