Control valve unit

Abstract

This control valve unit (3) to be used in a hydraulic system (1) of a construction machine includes a casing (4) and a spool (5a). The spool (5a) can move from a neutral position (52) to an arm pulling position (53) or an arm pushing position (51) and, at the neutral position (52), blocks a pump channel (41), a tank channel (42), an arm pulling supply channel (43), and an arm pushing supply channel (44) of the casing (4). Incorporated in the spool (5a) are: a first check valve (61) that allows a flow from the arm pushing supply channel (44) toward the arm pulling supply channel (43) when the spool (5a) is positioned at the arm pulling position (53) at which the pump channel (41) communicates with the arm pulling supply channel (43); and a second check valve (62) that allows a flow from the arm pulling supply channel (43) toward the arm pushing supply channel (44) when the spool (5a) is positioned at the arm pushing position (51) at which the pump channel (41) communicates with the arm pushing supply channel (44).

Description

Control valve unit

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[0001] The present disclosure relates to a control valve unit used in a hydraulic system of a construction machine.

[0002] A construction machine is equipped with a hydraulic system including a hydraulic pump and a plurality of hydraulic actuators. In such a hydraulic system, hydraulic oil is supplied to each hydraulic actuator via a control valve.

[0003] For example, Patent Document 1 discloses a hydraulic system including a swing control valve, a boom control valve, an arm control valve, and a bucket control valve mounted on a hydraulic excavator. The arm control valve is connected to the hydraulic pump by a pump line, connected to a tank by a tank line, and connected to an arm cylinder by an arm push supply line and an arm pull supply line. Further, FIG. 4 of Patent Document 1 describes an arm control valve capable of regenerating hydraulic oil during arm pulling.

[0004] Specifically, the arm control valve described in FIG. 4 of Patent Document 1 incorporates a check valve that allows the flow from the arm push supply line to the arm pull supply line during arm pulling.

[0005] Japanese Patent Application Laid-Open No. 2020-56226

[0006] Generally, in a hydraulic system of a construction machine, a control valve unit including a plurality of control valves is used. The control valve unit includes a casing and a plurality of spools slidably held in the casing, and each spool and the adjacent portion of the spool in the casing constitute one control valve.

[0007] If the control valve unit includes an arm control valve, the spool constituting the arm control valve is movable from a neutral position to an arm-pull position or an arm-push position. In the neutral position, the spool blocks the pump passage, tank passage, arm-pull supply passage, and arm-push supply passage provided in the casing. In the arm-pull position, the spool connects the pump passage to the arm-pull supply passage and the arm-push supply passage to the tank passage. In the arm-push position, the spool connects the pump passage to the arm-push supply passage and the arm-pull supply passage to the tank passage.

[0008] Such control valve units have a demand for enabling the regeneration of hydraulic fluid not only when the arm is pulled back but also when the arm is pushed. For example, in a hydraulic excavator, when pushing the arm from a position where the arm is pulled back to a position in front of the vertical line passing through the arm's pivot center, the arm's own weight acts in the direction of the swing as the arm swings back to the aforementioned vertical line, which can cause cavitation in the arm push supply passage. If the hydraulic fluid can be regenerated when the arm is pushed, such cavitation can be prevented.

[0009] Therefore, the present disclosure aims to provide a control valve unit that can regenerate the hydraulic fluid not only when the arm is pulled, but also when the arm is pushed.

[0010] This disclosure provides a control valve unit for use in a hydraulic system of construction machinery, comprising: a casing including a pump passage, a tank passage, an arm pull supply passage, and an arm push supply passage; and a spool that is movable from a neutral position blocking the pump passage, the tank passage, the arm pull supply passage, and the arm push supply passage to an arm pull position in which the pump passage communicates with the arm pull supply passage and the arm push supply passage communicates with the tank passage, or an arm push position in which the pump passage communicates with the arm push supply passage and the arm pull supply passage communicates with the tank passage, wherein the spool incorporates a first check valve that allows flow from the arm push supply passage to the arm pull supply passage when in the arm pull position, and a second check valve that allows flow from the arm pull supply passage to the arm push supply passage when in the arm push position.

[0011] According to this disclosure, a control valve unit is provided that can regenerate the hydraulic fluid not only when the arm is pulled, but also when the arm is pushed.

[0012] This is a schematic diagram of a hydraulic system including a control valve unit according to one embodiment. This is a side view of a hydraulic excavator, which is an example of construction machinery.

[0013] Figure 1 shows a hydraulic system 1 for a construction machine including a control valve unit 3 according to one embodiment, and Figure 2 shows a construction machine 9 on which the hydraulic system 1 is mounted. The construction machine 9 shown in Figure 2 is a hydraulic excavator, but the construction machine 9 may be other construction machines such as a hydraulic crane.

[0014] The construction machine 9 shown in Figure 2 is self-propelled and includes a vehicle 91 and a slewing body 92 that is rotatably supported on the vehicle 91. The slewing body 92 is equipped with a cabin 93 including a driver's seat and to which a boom 94 is attached. An arm 95 is attached to the tip of the boom 94, and a bucket 96 is attached to the tip of the arm 95. However, the construction machine 9 does not have to be self-propelled.

[0015] The hydraulic system 1 includes a boom cylinder 21, an arm cylinder 22, and a bucket cylinder 23 as hydraulic actuators, as shown in Figure 2, as well as a slewing motor and a pair of left and right travel motors. The boom cylinder 21 raises and lowers the boom 94, the arm cylinder 22 swings the arm 95, and the bucket cylinder 23 swings the bucket 96. The hydraulic system 1 also includes a hydraulic pump 11 that supplies hydraulic fluid to these hydraulic actuators via a control valve unit 3, as shown in Figure 1.

[0016] Note that in Figure 1, hydraulic actuators other than the arm cylinder 22 are omitted for the sake of simplifying the drawing. Furthermore, in the following, the configurations for hydraulic actuators other than the arm cylinder 22 will not be explained unless specifically noted.

[0017] The control valve unit 3 includes a casing 4 and a plurality of spools 5 slidably held in the casing 4, and each spool 5 and the adjacent portion of the spool 5 in the casing 4 constitute a single control valve.

[0018] More specifically, the spool 5 includes a spool 5a that constitutes an arm control valve, and the casing 4 includes a spool hole 40 into which the spool 5a is slidably inserted. In this embodiment, the spool 5a operates in response to pilot pressure acting on both end faces. For this reason, the casing 4 includes a pair of pilot chambers 4a and 4b facing both end faces of the spool 5a. However, the spool 5a does not necessarily have to operate in response to pilot pressure, and a linear motion mechanism including an electric motor and a ball screw may be connected to the spool 5a.

[0019] Furthermore, the control valve unit 3 has a pump port 3a, a tank port 3b, and a pair of arm ports 3c and 3d on the surface of the casing 4. The pump port 3a is connected to the hydraulic pump 11 by pump piping 12, the tank port 3b is connected to the tank by tank piping 13, and the arm ports 3c and 3d are connected to the arm cylinders 22 by arm piping 2a and 2b.

[0020] In this embodiment, arm pulling is performed by extending the arm cylinder 22, and arm pushing is performed by shortening the arm cylinder 22. In other words, the arm piping 2a and arm port 3c are on the head side of the arm cylinder 22, and the arm piping 2b and arm port 3d are on the rod side of the arm cylinder 22.

[0021] However, conversely to this embodiment, the arm may be pulled by shortening the arm cylinder 22, and the arm may be pushed by extending the arm cylinder 22. In this case, the arm piping 2a and arm port 3c are on the rod side of the arm cylinder 22, and the arm piping 2b and arm port 3d are on the head side of the arm cylinder 22.

[0022] The casing 4 of the control valve unit 3 includes a pump passage 41 extending from the pump port 3a to the spool hole 40, a tank passage 42 extending from the tank port 3b to the spool hole 40, an arm pull supply passage 43 extending from the arm port 3c to the spool hole 40, and an arm push supply passage 44 extending from the arm port 3d to the spool hole 40. The arm push supply passage 44 is provided with a lock valve 45 to prevent downward swinging of the arm 95 due to its own weight when the arm 95 is located behind a vertical line passing through the pivot center of the arm 95.

[0023] The arm-pull supply passage 43 is connected to the tank port 3b by a relief passage 71. A relief valve 72 is provided in the relief passage 71, and a replenishment passage 73 is connected to bypass the relief valve 72. The replenishment passage 73 is provided with a check valve 74 that allows flow from the tank port 3b to the arm-pull supply passage 43, but prohibits flow from the arm-pull supply passage 43 to the tank port 3b.

[0024] Similarly, the portion of the arm push supply passage 44 between the arm port 3d and the lock valve 45 is connected to the tank port 3b by a relief passage 81. The relief passage 81 is equipped with a relief valve 82, and a replenishment passage 83 is connected to bypass the relief valve 82. The replenishment passage 83 is equipped with a check valve 84 that allows flow from the tank port 3b to the arm push supply passage 44, but prohibits flow from the arm push supply passage 44 to the tank port 3b.

[0025] The spool 5a is movable from the neutral position 52 to the arm-pulling position 53 or the arm-pushing position 51. In the neutral position 52, the spool 5a blocks the pump passage 41, the tank passage 42, the arm-pulling supply passage 43, and the arm-pushing supply passage 44. In the arm-pulling position 53, the spool 5a connects the pump passage 41 to the arm-pulling supply passage 43 and the arm-pushing supply passage 44 to the tank passage 42. In the arm-pushing position 51, the spool 5a connects the pump passage 41 to the arm-pushing supply passage 44 and the arm-pulling supply passage 43 to the tank passage 42.

[0026] The spool 5a incorporates a first check valve 61 that functions in the arm-pulled position 53 and a second check valve 62 that functions in the arm-pushed position 51. For example, the spool 5a is hollow, and the first check valve 61 and the second check valve 62 are located inside the spool 5a.

[0027] The first check valve 61 allows flow from the arm pushing supply passage 44 to the arm pulling supply passage 43 when the spool 5a is in the arm pulling position 53, but prohibits flow from the arm pulling supply passage 43 to the arm pushing supply passage 44.

[0028] The second check valve 62 allows flow from the arm pull supply passage 43 to the arm push supply passage 44 when the spool 5a is in the arm push position 51, but prohibits flow from the arm push supply passage 44 to the arm pull supply passage 43.

[0029] In the control valve unit 3 with the configuration described above, the first check valve 61 enables the regeneration of the hydraulic fluid when the arm is pulled, and the second check valve 62 enables the regeneration of the hydraulic fluid when the arm is pushed. Moreover, since the first check valve 61 and the second check valve 62 are built into the spool 5a, a structure that enables the regeneration of the hydraulic fluid when the arm is pulled and pushed can be realized without increasing the size of the casing 4.

[0030] This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0031] <Summary> In a first aspect, the present disclosure provides a control valve unit for use in a hydraulic system of construction machinery, comprising: a casing including a pump passage, a tank passage, an arm pull supply passage, and an arm push supply passage; and a spool movable from a neutral position blocking the pump passage, the tank passage, the arm pull supply passage, and the arm push supply passage to an arm pull position in which the pump passage communicates with the arm pull supply passage and the arm push supply passage communicates with the tank passage, or an arm push position in which the pump passage communicates with the arm push supply passage and the arm pull supply passage communicates with the tank passage, wherein the spool incorporates a first check valve that allows flow from the arm push supply passage to the arm pull supply passage when in the arm pull position, and a second check valve that allows flow from the arm pull supply passage to the arm push supply passage when in the arm push position.

[0032] With the above configuration, the first check valve enables the regeneration of the hydraulic fluid when the arm is pulled, and the second check valve enables the regeneration of the hydraulic fluid when the arm is pushed. Moreover, since the first and second check valves are built into the spool, a structure that enables the regeneration of the hydraulic fluid when the arm is pulled and pushed can be realized without increasing the size of the casing.

[0033] 1 Hydraulic system 11 Hydraulic pump 22 Arm cylinder 3 Control valve unit 4 Casing 41 Pump passage 42 Tank passage 43 Arm pull supply passage 44 Arm push supply passage 5 Spool 51 Arm push position 52 Neutral position 53 Arm pull position 61 First check valve 62 Second check valve 9 Construction machinery

Claims

1. A control valve unit for use in a hydraulic system of construction machinery, comprising: a casing including a pump passage, a tank passage, an arm pull supply passage, and an arm push supply passage; and a spool movable from a neutral position blocking the pump passage, the tank passage, the arm pull supply passage, and the arm push supply passage to an arm pull position in which the pump passage communicates with the arm pull supply passage and the arm push supply passage communicates with the tank passage, or an arm push position in which the pump passage communicates with the arm push supply passage and the arm pull supply passage communicates with the tank passage, wherein the spool incorporates a first check valve that allows flow from the arm push supply passage to the arm pull supply passage when in the arm pull position, and a second check valve that allows flow from the arm pull supply passage to the arm push supply passage when in the arm push position.

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