Work vehicle

Abstract

To provide a work vehicle capable of improving workability of an attachment operating through connection to two system operating circuits, allowing mounted equipment to be simplified, the vehicle to be made compact and vehicle cost to be reduced.SOLUTION: A work vehicle 1 of the present invention is provided with: a first operating circuit 61 and a second operating circuit 62 supplying hydraulic fluid to an attachment 46 operating with hydraulic pressure; a first changeover valve 71 changing over therebetween; a control valve 64 controlling operation of the attachment 46; a proportional solenoid valve 66 controlling operation of the control valve 64; and a pilot circuit 63 supplying pilot oil to the control valve 64 through the proportional solenoid valve 66, wherein the pilot circuit 63 has a second changeover valve 72 changing over an oil passage in which the pilot oil is made flow between a first oil passage 81 and a second oil passage 82, and a junction part 74 at a downstream side thereof. A pressure reduction valve 76 is arranged in the second oil passage 82.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a work vehicle equipped with a hydraulically operated working device. [Background technology]

[0002] Conventionally known examples of working vehicles include hydraulic excavators and track loaders, which are equipped with a lower body to which crawlers or tires for traveling are attached, an upper body disposed on the lower body, and a working device attached to the lower body or upper body and operated by hydraulic pressure (i.e., hydraulic oil at a predetermined pressure).

[0003] In the above-mentioned work vehicle, an attachment suitable for the work content may be selected from multiple types and attached as an attachment constituting a working device (see Patent Document 1: JP 2020-041266 A). For this reason, the work vehicle is provided with a service circuit that supplies hydraulic oil to operate the attachment. The attachment may be configured to be connected to a single service circuit and operate, such as a breaker (i.e., one that performs one type of operation), or configured to be connected to a dual service circuit and operate, such as a tiltrotator bucket (i.e., one that performs two types of operation). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-041266 A Summary of the Invention [Problem to be solved by the invention]

[0005] For example, when attempting to provide two service circuits in a work vehicle, a standard design would be to provide a control valve for controlling the operation of the attachment, a proportional solenoid valve for controlling the operation of the control valve, etc., for each system (each service circuit). However, with work vehicles, simplifying the onboard equipment and making the vehicle more compact are constant issues, and this demand becomes more pronounced especially in smaller work vehicles.

[0006] The present inventors therefore conducted extensive research to simplify the on-board equipment and to make the vehicle more compact, particularly in a work vehicle equipped with two service circuits. However, in the process, new problems became apparent. [Means for solving the problem]

[0007] First, the inventors devised a configuration for a work vehicle in which a proportional solenoid valve and a control valve are provided in common, and a switching valve is provided in the circuit downstream of the control valve, thereby providing two service circuits. With this configuration, the proportional solenoid valve, the control valve, etc. can be shared, which simplifies the on-board equipment and makes the vehicle more compact.

[0008] On the other hand, new problems were identified with the above configuration. Specifically, an attachment connected to two service circuits can perform two different operations by switching the service circuit with a selector valve. However, because the amount of hydraulic oil supplied to either service circuit remains the same, one operation may occur too quickly (or the other may occur too slowly), resulting in a deterioration in workability.

[0009] One possible solution to this problem would be to install an advanced controller and control the proportional solenoid valve to operate optimally depending on the system of the service circuit to be switched (i.e., the operation of the attachment). However, installing such a controller would result in a rise in the vehicle cost.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a work vehicle that can improve the operability of attachments that are connected to and operate through two service circuits, while simplifying the onboard equipment, making the vehicle more compact, and reducing vehicle costs.

[0011] The present invention solves the above problems by the solution means described below as one embodiment.

[0012] A work vehicle according to one embodiment is a work vehicle equipped with a hydraulically operated attachment to perform a specified task, and includes a first service circuit and a second service circuit that supply hydraulic oil to the attachment, a first changeover valve that switches the circuit that supplies the hydraulic oil between the first service circuit and the second service circuit, a control valve that controls the operation of the attachment, a proportional solenoid valve that controls the operation of the control valve, and a pilot circuit that supplies pilot oil to the control valve via the proportional solenoid valve, wherein the pilot circuit has a second changeover valve that switches an oil passage through which the pilot oil flows between a first oil passage and a second oil passage, and a junction section that joins the first oil passage and the second oil passage downstream, and a pressure reducing valve is provided in the second oil passage.

[0013] According to the above configuration, it is possible to simplify the on-board equipment, make the vehicle more compact, and reduce vehicle costs, while improving the operability of the attachments that are connected to and operate through the two service circuits.

[0014] It is also preferable to provide one trigger switch that simultaneously switches the first and second switching valves with one operation.

[0015] It is also preferable that a slide switch for controlling the operation of the proportional solenoid valve is provided, the slide switch being slidably provided on the grip portion of the operating lever.

[0016] Further, it is preferable that the pilot circuit is provided with a check valve downstream of the pressure reducing valve in the second oil passage.

[0017] It is also preferable that the pressure reducing valve has an adjustment portion capable of adjusting the amount of pressure reduction, and is disposed inside an equipment compartment provided under a seat on which an operator sits, and in the vicinity of a door for opening and closing the equipment compartment. Effect of the Invention

[0018] According to one embodiment of the work vehicle, it is possible to simplify the onboard equipment, make the vehicle more compact, and reduce vehicle costs, while improving the operability of attachments that are connected to and operate through two service circuits. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view showing an example of a work vehicle according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing an example of a cab of the work vehicle of FIG. [Diagram 3] FIG. 3 is a perspective view showing an example of an operating device for the work vehicle of FIG. [Figure 4] FIG. 4 is a circuit diagram (part) of the work vehicle of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic diagram (perspective view from above the left front) showing an example of a work vehicle 1 according to this embodiment. For convenience of explanation, arrows may be used in the drawings to indicate up / down, left / right, and front / rear directions. In addition, in all drawings for explaining the embodiment, members having the same function are given the same reference numerals, and repeated explanations thereof may be omitted.

[0021] First, a description will be given of the overall configuration of the work vehicle 1. A hydraulic excavator will be taken as an example of the work vehicle 1. However, the work vehicle 1 is not limited to a hydraulic excavator.

[0022] As shown in FIG. 1, a work vehicle 1 includes a vehicle body including a lower body 2 and an upper body 3 disposed on the lower body 2 (note that the lower body 2 and the upper body 3 may be integrally configured).

[0023] The work vehicle 1 is equipped with working devices 12, 14 that are attached to the lower body 2 and upper body 3 and are operated by hydraulic pressure (hydraulic oil at a specified pressure). The lower body 2 is equipped with a traveling device 10 that drives the vehicle. The upper body 3 is equipped with a driver's cab 16 at the front where an operator sits and where various operating devices are provided to operate the vehicle for traveling and work.

[0024] An example of the traveling device 10 includes a pair of left and right crawlers 26. However, the traveling device 10 is not limited to the crawlers 26, and may include tires (not shown) instead of the crawlers 26. The crawlers 26 are driven (travel) by a traveling hydraulic motor 28.

[0025] An example of the working device 12 includes a blade 22. The blade 22 is attached to the lower body 2 so as to be swingable up and down (including forward and backward). The blade 22 is driven by a hydraulic cylinder (blade cylinder) 32. However, the present invention is not limited to the above configuration.

[0026] Examples of the working device 14 include a boom 42, an arm 44, and a detachable attachment 46. In Fig. 1, a bucket (without using a service circuit) is shown as the attachment 46. However, this is not limited to this, and there are various other types such as a breaker (with one service circuit) and a tiltrotator bucket (with two service circuits).

[0027] As a specific configuration, the boom 42 is attached to the upper body 3 so as to be swingable up and down (including front and rear components). In this embodiment, a boom bracket 48 is provided between the upper body 3 and the boom 42. The boom bracket 48 allows the boom 42 to swing left and right (including front and rear components) with respect to the upper body 3. Note that the boom bracket 48 may be omitted. The arm 44 is attached to the boom 42 so as to be swingable up and down (including front and rear components). The attachment 46 is attached to the arm 44 so as to be swingable up and down (including front and rear components). The boom 42 is driven by a hydraulic cylinder (boom cylinder) 52. The arm 44 is driven by a hydraulic cylinder (arm cylinder) 54. The attachment 46 is driven by a hydraulic cylinder (bucket cylinder) 56. However, the configuration is not limited to the above.

[0028] As described above, the attachment 46 is configured such that one suitable for the work content is selected from a plurality of types, and is detachably attached to the arm 44. Note that a quick hitch (not shown) may be interposed between the arm 44 and the attachment 46. In that case, a separate service circuit may be provided to operate the quick hitch.

[0029] The drive mechanism for driving the traveling hydraulic motor 28 and each hydraulic cylinder is composed of, for example, a hydraulic pump (main hydraulic pump, etc.) driven by the drive source 18, a control valve, etc. An operator operates a predetermined operating device to actuate the control valve, and control is performed to supply hydraulic oil at a predetermined pressure delivered from the hydraulic pump to the traveling hydraulic motor 28 and each hydraulic cylinder. This allows the traveling device 10 to travel, and the working devices 12, 14 to work. One or more hydraulic pumps that constitute the drive mechanism are provided depending on the configuration and load of the working devices 12, 14 and the traveling device 10.

[0030] In this embodiment, the hydraulic pump 30 supplies hydraulic oil to the service circuit, and the pilot hydraulic pump 40 supplies pilot oil used to control each device (specifically, each control valve) (details of the circuits, etc. will be described later). As a modified example, it is also possible to use a configuration in which these hydraulic pumps are not provided, and hydraulic oil supplied from another hydraulic pump (for example, a main hydraulic pump, etc.) is diverted (reduced in pressure as necessary) and used (not shown).

[0031] The work vehicle 1 is equipped with an engine (an internal combustion engine that burns fuel) as the above-mentioned drive source 18. Note that, as another example of the drive source 18, a configuration may be used in which an electric motor (one or more depending on the number of hydraulic pumps, the rated output, etc.) is provided instead of or in addition to the engine (not shown).

[0032] Here, the work vehicle 1 according to this embodiment is provided with at least two systems (a first service circuit 61 and a second service circuit 62 described below) as service circuits that supply hydraulic oil to operate the attachment 46. This makes it possible to use an attachment 46 (46A) that is connected to two service circuits and performs two types of operation, such as a tiltrotator bucket, for example. Note that the vehicle may be configured to further include one or more separate service circuits (not shown).

[0033] More specifically, as shown in the circuit diagram (schematic diagram) of FIG. 4, the attachment 46 (46A) is provided with a first switching valve 71 that switches between a first service circuit 61 and a second service circuit 62 as a circuit for supplying hydraulic oil to the attachment 46 (46A). The attachment 46 (46A) is also provided with a control valve 64 that controls the operation of the attachment 46 (46A). The attachment 46 (46A) is also provided with a proportional solenoid valve 66 that controls the operation of the control valve 64. The attachment 46 (46A) is also provided with a pilot circuit 63 that supplies pilot oil to the control valve 64 via the proportional solenoid valve 66 (i.e., the direction and flow rate are controlled by the proportional solenoid valve 66). With this configuration, the control valve 64, the proportional solenoid valve 66, etc. can be made common (i.e., one each is required for common use), which simplifies the onboard equipment and makes the vehicle more compact. In this embodiment, a solenoid valve is used for the first switching valve 71.

[0034] The pilot circuit 63 is provided with a second switching valve 72 that switches the oil passage through which the pilot oil flows between a first oil passage 81 and a second oil passage 82. The pilot circuit 63 is also provided with a junction section 74 that joins the first oil passage 81 and the second oil passage 82 downstream of the second switching valve 72. In this embodiment, a solenoid valve is used for the second switching valve 72. Here, by using solenoid valves of the same configuration for the first switching valve 71 and the second switching valve 72, an increase in the number of parts is suppressed, thereby suppressing costs.

[0035] Furthermore, the second oil passage 82 is provided with a pressure reducing valve 76 that reduces the pressure of the pilot oil flowing through the second oil passage 82 to a predetermined value. Also, the second oil passage 82 is provided with a check valve 78 downstream of the pressure reducing valve 76 and upstream of the junction 74. The presence of this check valve 78 makes it possible to prevent the pilot oil flowing through the first oil passage 81 from flowing back into the second oil passage 82 and causing the pressure to drop below the set value.

[0036] The work vehicle 1 is also provided with an operating device for switching between the first service circuit 61 and the second service circuit 62. As an example of the operating device, a push-type trigger switch 92 is provided on a grip portion 90a of an operating lever (for example, a right operating lever) 90 in the driver's cab 16 (see FIG. 2). In this embodiment, the operation of the trigger switch 92 is converted into a signal (current) for operating the first switching valve 71 and the second switching valve 72 via a remote controller 96 provided inside (or outside) the operating lever 90, and is transmitted to the first switching valve 71 and the second switching valve 72. However, the present invention is not limited to this configuration.

[0037] To explain a specific example of operation accompanying the operation of the trigger switch 92, the first switching valve 71 and the second switching valve 72 are configured to be switched simultaneously by one operation (one push) of the trigger switch 92. More specifically, the first switching valve 71 is switched to the first service circuit 61 side, and at the same time, the second switching valve 72 is switched to the first oil passage 81 side. The reverse switching is similar, and the first switching valve 71 is switched to the second service circuit 62 side, and at the same time, the second switching valve 72 is switched to the second oil passage 82 side. That is, each time the trigger switch 92 is operated (one push), the above two settings are alternately repeated.

[0038] The work vehicle 1 also includes an operating device for operating the attachment 46 (46A). Specifically, the operating device is an operating device for controlling the operation of the proportional solenoid valve 66. As an example of the operating device, a slide switch 94 of a sliding type is provided on a grip portion 90a of an operating lever (e.g., a right operating lever) 90 of the driver's cab 16 (see FIG. 3). Note that in this embodiment, the operation (amount, direction) of the slide switch 94 is converted into a signal (current) for operating the proportional solenoid valve 66 via a remote controller 96 provided inside (or outside) the operating lever 90, and is transmitted to the proportional solenoid valve 66. However, the present invention is not limited to this configuration.

[0039] To explain a specific example of operation accompanying the operation of the slide switch 94, when the slide switch 94 is moved from the neutral position to one end side (e.g., the right end side), the operation of the attachment 46 (46A) (e.g., right rotation, right tilt, etc.) becomes faster as the amount of movement increases. Similarly, when the slide switch 94 is moved from the neutral position to the other end side (e.g., the left end side), the operation of the attachment 46 (46A) (e.g., left rotation, left tilt, etc.) becomes faster as the amount of movement increases.

[0040] Here, as described above in advance, an attachment connected to two service circuits can perform two types of operation by providing a switching valve to switch the service circuits. However, the following problem was revealed. That is, since the amount of hydraulic oil supplied to either service circuit is the same, one operation may be too fast (or the other operation may be too slow), which may cause a deterioration in workability. Specifically, in the case where a tiltrotator bucket is used as the attachment 46 (46A), switching is performed to the first service circuit 61 to perform a rotation operation, and switching is performed to the second service circuit 62 to perform a tilt operation. In this case, if the above-mentioned configuration according to this embodiment is not provided, a state in which the tilt operation is too fast when switching to the second service circuit 62, or a state in which the rotation operation is too slow when switching to the first service circuit 61, may occur.

[0041] In response to this problem, the work vehicle 1 according to this embodiment can solve the problem without providing a configuration in which a control valve, proportional solenoid valve, etc. are provided for each of the two service circuits (first service circuit 61 and second service circuit 62) (i.e., a configuration in which two of each are provided), and without providing a configuration in which an advanced controller is mounted to control each of the two service circuits individually. In other words, it is possible to improve the operability of the attachment 46 (46A) that operates by being connected to the two service circuits, while simplifying the on-board equipment, making the vehicle more compact, and suppressing vehicle costs.

[0042] Specifically, this problem can be solved by configuring the first switching valve 71 and the second switching valve 72 to be switched simultaneously by the trigger switch 92, and providing the pressure reducing valve 76 in the second oil passage 82 where the switching is performed by the second switching valve 72. According to this configuration, in a state where the first switching valve 71 is switched to the second service circuit 62 side and the second switching valve 72 is simultaneously switched to the second oil passage 82 side, the following action and effect can be obtained compared to a state where the switching is performed to the other side (a state where the first switching valve 71 is on the second service circuit 62 side and the second switching valve 72 is on the second oil passage 82 side). That is, even if the operation amount of the slide switch 94 is the same (i.e., the operation amount of the proportional solenoid valve 66 is the same), the pilot oil that flows through the second oil passage 82 and is reduced in pressure by the pressure reducing valve 76 is input to the control valve 64. As a result, the pressure of the pilot oil input to the control valve 64 can be relatively reduced, and therefore the amount of actuation of the control valve 64 can be relatively reduced. Therefore, the actuation speed of the attachment 46 (46A) can be relatively reduced.

[0043] In this way, in an attachment 46 (46A) that performs two types of operation, a work vehicle 1 can be realized in which deterioration of workability does not occur due to one operation being too fast or the other operation being too slow.

[0044] Furthermore, in the work vehicle 1 according to this embodiment, the pressure reducing valve 76 has an adjustment unit 76a capable of adjusting the amount of pressure reduction, and is disposed inside the equipment room 36 provided under the seat 34 on which the operator sits and in the vicinity of the opening and closing door 38 of the equipment room 36 (the distance is about several centimeters to several tens of centimeters) (see FIG. 2). With this configuration, the adjustment unit 76a can be touched simply by opening the opening and closing door 38, making it extremely easy to adjust the amount of pressure reduction in the pressure reducing valve 76. In particular, because it is disposed in the equipment room 36 provided under the seat 34 on which the operator sits, the operator can easily and quickly make adjustments while actually checking the operating speed for each type of operation of the attachment 46 (46A), resulting in further improvement in operability.

[0045] As described above, the above-mentioned work vehicle makes it possible to simplify the onboard equipment, make the vehicle more compact, and reduce vehicle costs, while improving the operability of attachments that are connected to and operate through two service circuits.

[0046] The present invention is not limited to the above embodiment (hydraulic excavator), and can be similarly applied to a work vehicle (such as a track loader) in which the upper body does not rotate relative to the lower body. [Explanation of symbols]

[0047] 1. Work vehicles 10 Running gear 12, 14 Working equipment 46, 46A Attachment 61 First Service Circuit 62 Second Service Circuit 63 Pilot Circuit 64 Control valve 66 Proportional Solenoid Valve 71 First switching valve 72 Second switching valve 76 Pressure reducing valve

Claims

1. A work vehicle equipped with a hydraulically operated attachment for performing a predetermined task, a first service circuit and a second service circuit for supplying hydraulic fluid to the attachment; a first switching valve that switches a circuit for supplying the hydraulic oil between the first service circuit and the second service circuit; A control valve that controls the operation of the attachment; a proportional solenoid valve for controlling the operation of the control valve; a pilot circuit for supplying pilot oil to the control valve via the proportional solenoid valve; The pilot circuit has a second switching valve that switches the oil passage through which the pilot oil flows between the first oil passage and the second oil passage, and a confluence portion that joins the first oil passage and the second oil passage on the downstream side, and a pressure reducing valve is provided in the second oil passage. A work vehicle characterized by:

2. The valve is provided with one trigger switch that simultaneously switches the first and second switching valves with one operation.

2. The work vehicle according to claim 1,

3. A slide switch is provided to control the operation of the proportional solenoid valve. The slide switch is slidably provided on the grip portion of the operating lever.

2. The work vehicle according to claim 1,

4. The pilot circuit is provided with a check valve downstream of the pressure reducing valve in the second oil passage.

2. The work vehicle according to claim 1,

5. The pressure reducing valve has an adjustment unit that can adjust the amount of pressure reduction, and is disposed inside the device room provided under the seat where the operator is seated, and in a position near the opening / closing door of the device room. The work vehicle according to any one of claims 1 to 4,

Images