loader

Abstract

This reduces the cost of the dump cylinder, prevents the generation of negative pressure, and reduces the number of pipes between the dump cylinder and the auxiliary cylinder. [Solution] The loader of the present invention is characterized in that the dump cylinder 41 is configured as a single-rod type, the squeezing port 41b of the dump cylinder 41 is connected to the rising port 51a of the auxiliary cylinder 51, while the dump port 41a of the dump cylinder 41 is connected to the hydraulic tank T via a flow rate adjustment circuit F branched from a dump circuit having a check valve C, when raising the lift arm 23, the lowering port 27b of the lift cylinder 27 is connected to the dump port 41a of the dump cylinder 41 via the dump circuit and check valve C, and when lowering the lift arm 23, the rising port 27a of the lift cylinder 27 is connected to the hydraulic tank T, and the dump port 41a of the dump cylinder 41 is connected to the hydraulic tank T via the dump circuit and check valve C.

Description

Technical Field

[0001] The present invention relates to a loader that is mounted on a work vehicle such as a tractor and raises and lowers heavy objects with a work implement such as a bucket.

Background Art

[0002] A work implement is an attachment device that is detachably mounted on a work vehicle such as a tractor. As shown in FIG. 2, a work implement mounted on the front side of a tractor 10 is called a front loader 21. This front loader 21 has lift arms 23 that are raised and lowered by a lift cylinder 27, and various tip attachments such as a bucket 32, a fork, a grader, a roll grab, a container bucket, a loading hook, etc. are attached to the tips of these lift arms 23 according to the work content.

[0003] Hereinafter, it will be described assuming that the attachment is the bucket 32. As shown in FIG. 2, a dump cylinder 41 is disposed on the upper part of the tip side of the lift arm 23, and the bucket 32 is configured to tilt forward (dump operation) or tilt backward (squeegee operation) by this dump cylinder 41.

[0004] The raising and lowering operation of the lift arm 23 and the dump and squeegee operations of the bucket 32 are performed by operating, for example, a joystick-type operation lever provided in the driver's seat of the tractor 10 in the front-back, left-right directions. The operation lever can perform composite operations such as raising or lowering the lift arm 23 while dumping or squeegeeing the bucket 32, in addition to individual operations of raising and lowering the lift arm 23 and dumping and squeegeeing the bucket 32.

[0005] Incidentally, the hydraulic circuit of the front loader 21 is known to be equipped with a leveling mechanism to prevent the load from falling or collapsing. Examples of front loaders equipped with this leveling mechanism include the front loader in Patent Document 1 (Japanese Patent Publication No. 6-88351, Figure 3) and the front loader in Non-Patent Document 1 (MX T400 series front loader from France, hereinafter referred to as MX front loader). With this leveling mechanism, the bucket 32 ​​dumps or scoops simultaneously with the lifting and lowering operation of the lift arm 23, and the angle of the bucket 32 ​​with respect to the ground is maintained at a nearly constant level.

[0006] Specifically, as shown in Figures 2 and 3, an auxiliary cylinder 51 is installed adjacent to the upper side of the lift cylinder 27, and this auxiliary cylinder 51 maintains the parallelism (horizontalness to the ground) of the bucket 32 ​​(parallel raising and lowering of the bucket). In detail, as shown in Figures 4A and 4B, the raising port 51a of the auxiliary cylinder 51 is connected to the squeezing port 41b of the dump cylinder 41 via piping L1. Also, the lowering port 51b of the auxiliary cylinder 51 is connected to the dump port 41a of the dump cylinder 41 via piping L2.

[0007] As a result, when the lift arm 23 is raised or lowered, pressurized oil is supplied to and discharged from the lift port 51a of the auxiliary cylinder 51 to the squeegee port 41b of the dump cylinder 41 via piping L1, in accordance with the height of the lift arm 23, thereby leveling the bucket 32. On the other hand, pressurized oil is supplied to and discharged from the dump port 41a of the dump cylinder 41 via piping L2 from the lowering port 51b of the auxiliary cylinder 51. Both the dump cylinder 41 and the auxiliary cylinder 51 are of the same diameter and rod type, and the volume ratio of the two cylinders is set so that the amount of pressurized oil supplied to and discharged between the dump cylinder 41 and the auxiliary cylinder 51 is the same.

[0008] On the other hand, the MX front loader has a dump cylinder with two rods of different diameters (using special-sized materials) and an auxiliary cylinder with a single rod and double-acting design. As a result, the dump port pressure during upward dumping is normal pressure for the front loader in Patent Document 1, but negative pressure for the MX front loader.

[0009] Figures 5A and 5B show the parallel lifting and parallel lowering circuits of the MX front loader. The hydraulic flow is the same as in Figures 4A and 4B of Patent Document 1. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 6-88351 [Non-patent literature]

[0011] [Non-Patent Document 1] "MX, Agricultural equipment manufacturer" (searched September 25, 2024), T400 series front loader from MX, a French company, Internet<URL:https: / / m-x.eu / en / > [Overview of the project] [Problems that the invention aims to solve]

[0012] However, it has been found that such a leveling mechanism using an auxiliary cylinder 51 has the following problems. Problems with the leveling mechanism described in Patent Document 1 1) The double-rod type dump cylinder 41 and auxiliary cylinder 51 have more parts and a longer cylinder length compared to the single-rod type, resulting in higher costs. 2) Two pipes, L1 and L2, are required between the dump cylinder 41 and the auxiliary cylinder 51.

[0013] Challenges of the leveling mechanism in MX front loaders 1) The double-rod type dump cylinder 41 has more parts and a longer cylinder length compared to a single-rod cylinder, and is more expensive because it uses material sizes that are not commercially available. 2) Two pipes, L1 and L2, are required between the dump cylinder 41 and the auxiliary cylinder 51. 3) Even if the dump cylinder 41 is made of two rods of different diameters (using special size materials), it is difficult to perfectly match the volume ratio with the auxiliary cylinder 51. Currently, the dump port 41a of the dump cylinder 41 and the lowering port 51b of the auxiliary cylinder 51 are under negative pressure, which negatively affects the durability of the sealing material.

[0014] Therefore, the objectives of the present invention are: 1) to simplify the structure of the dump cylinder and auxiliary cylinder to reduce costs (advantages compared to Japanese Patent Publication No. 6-88351, Figure 3 of Patent Document 1), and 2) to reduce the number of pipes between the dump cylinder and the auxiliary cylinder.

[0015] Table 1 below summarizes the differences in the leveling mechanisms of Patent Document 1, the MX Front Loader, and each loader of the present invention. [Table 1] [Means for solving the problem]

[0016] In order to solve the above problems, a loader according to the present invention includes a lift arm that is supported by a support bracket of a work vehicle so as to be movable up and down, a work implement that is supported by a tip end portion of the lift arm so as to be swingable up and down, a lift cylinder that is disposed between the support bracket and the lift arm and raises and lowers the lift arm by telescopic operation, an auxiliary cylinder that is disposed between the support bracket and the lift arm and telescopically operates in conjunction with the lift cylinder, and a dump cylinder that is disposed between the lift arm and the work implement and swings the work implement up and down by telescopic operation. In the loader, the dump cylinder is configured as a single-rod type, a squib port of the dump cylinder is connected to a raise port of the auxiliary cylinder, while a dump port of the dump cylinder is connected to a hydraulic tank via a flow rate adjustment circuit branched from a dump circuit having a check valve. When raising the lift arm, hydraulic pressure is supplied from a hydraulic pump to a raise port of the lift cylinder, while a lower port of the lift cylinder is connected to the dump port of the dump cylinder via the dump circuit and the check valve. When lowering the lift arm, hydraulic pressure is supplied from a hydraulic pump to a lower port of the lift cylinder, while a raise port of the lift cylinder is connected to the hydraulic tank, and the dump port of the dump cylinder is connected to the hydraulic tank via the dump circuit and the check valve. This is the gist of the present invention.

Advantages of the Invention

[0017] According to the loader of the present invention, 1) the dump cylinder is made into a single-rod type to reduce costs, 2) generation of negative pressure in the dump cylinder and the auxiliary cylinder is prevented, and 3) the piping between the dump cylinder and the auxiliary cylinder can be reduced to only one.

Brief Description of the Drawings

[0018] [Figure 1A] It is a diagram for explaining a parallel raise circuit of a loader according to an embodiment of the present invention. [Figure 1B] It is a diagram for explaining a parallel lower circuit of a loader according to an embodiment of the present invention. [Figure 2]It is a side view of a general front loader attached to the front side of a tractor. [Figure 3] It is a diagram showing the arrangement of each cylinder of a general front loader. [Figure 4A] It is a diagram for explaining the parallel lifting circuit of the front loader of Patent Document 1. [Figure 4B] It is a diagram for explaining the parallel lowering circuit of the front loader of Patent Document 1. [Figure 5A] It is a diagram for explaining the parallel lifting circuit of the MX front loader. [Figure 5B] It is a diagram for explaining the parallel lowering circuit of the MX front loader.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the loader according to the embodiment of the present invention will be described based on FIGS. 1A, 1B, and 2. As shown in FIG. 2, a bucket 32 as an attachment is attached to the tip of a lift arm 23 constituting the main body of the front loader 21 so as to be able to swing up and down. The base end of the lift arm 23 is attached to a support bracket 22 as a support base fixedly provided on the tractor 10 in FIG. 2.

[0020] A lift cylinder 27 is disposed between the support bracket 22 and the intermediate portion in the longitudinal direction of the lift arm 23. The lift arm 23 is configured to move up and down by the telescopic operation of the lift cylinder 27. The lift cylinder 27 is a single-rod double-acting hydraulic cylinder, and its base end side (cap side) is connected to the support bracket 22, and the rod side is connected to the lift arm 23.

[0021] A short auxiliary cylinder 51 is disposed adjacent to the upper side of the lift cylinder 27. The auxiliary cylinder 51 is a single-acting hydraulic cylinder, and its base end side (cap side) is connected to the support bracket 22, and the rod side is connected to the lift arm 23.

[0022] A dump cylinder 41 is positioned above the longitudinal middle section of the lift arm 23. The dump cylinder 41 is a single-rod double-acting hydraulic cylinder, similar to the lift cylinder 27, with its cap side supported by the lift arm 23 and its rod side connected to the bucket 32 ​​via a link. By configuring the dump cylinder 41 as a single-rod double-acting type, significant cost reductions and (for the same stroke) a substantial reduction in cylinder length are possible compared to conventional double-rod types.

[0023] As shown in Figures 1A and 1B, the hydraulic pump P, which serves as the hydraulic power source, is mounted on the tractor 10, and the hydraulic pump P and the front loader 21 are detachably connected via a hydraulic coupler or the like (not shown). Two switching valves (a first switching valve and a second switching valve, not shown) are connected to the hydraulic pump P, one for the lift cylinder 27 and the other for the dump cylinder 41. The first and second switching valves can be operated individually or simultaneously by a joystick-type operating lever.

[0024] The auxiliary cylinder 51 and the dump cylinder 41 are connected by a single pipe L1. Specifically, the lifting port 51a of the auxiliary cylinder 51 and the squeezing port 41b of the dump cylinder 41 are connected by pipe L1.

[0025] The lowering port 27b of the lift cylinder 27 is connected to the dump port 41a of the dump cylinder 41 by a dump circuit D having a pilot check valve C. This dump circuit D has a flow control circuit (bleed-off circuit) F that branches off from the primary side of the pilot check valve C and is connected to the hydraulic tank T. In the parallel lowering circuit of Figure 1B, the pilot check valve C opens when the pressure P at the squee port 41b of the dump cylinder 41 rises, connecting the dump port 41a of the dump cylinder 41 to the hydraulic tank T.

[0026] ● Parallel rising circuit During parallel upward movement, as shown in Figure 1A, pressurized oil from the hydraulic pump P is introduced into the upward port 27a of the lift cylinder 27. Meanwhile, the pressurized oil pushed out from the downward port 27b of the lift cylinder 27 is introduced into the dump port 41a of the dump cylinder 41 through the dump circuit D.

[0027] Some of the pressurized oil that does not enter the dump port 41a is returned to the hydraulic tank T through the flow control circuit (bleed-off circuit) F. If the amount of pressurized oil introduced into the dump port 41a is insufficient, an antivoid valve (makeup valve) can be attached to the switching valve to prevent the generation of air bubbles. Meanwhile, the pressurized oil pushed out from the squeezing port 41b of the dump cylinder 41 is introduced into the rising port 51a of the auxiliary cylinder 51 through the piping L1.

[0028] ●Parallel descending circuit During parallel descent, as shown in Figure 1B, pressurized oil from the hydraulic pump P is introduced into the descent port 27b of the lift cylinder 27. Meanwhile, the pressurized oil pushed out from the rise port 27b of the lift cylinder 27 is returned to the hydraulic tank T.

[0029] The pressurized oil pushed out from the rise port 51a of the auxiliary cylinder 51 is introduced into the squeegee port 41b of the dump cylinder 41. Meanwhile, the pressurized oil pushed out from the dump port 41a of the dump cylinder 41 is returned to the tank T through the dump circuit D. At this time, the pilot check valve C of the dump circuit D opens due to the pressure rise in the squeegee port 41 of the dump cylinder 41, allowing the oil to be discharged through the dump circuit D.

[0030] ● Design flexibility The dump circuit D, which includes a pilot check valve C, facilitates the optimization of the leveling mechanism and also increases the design flexibility of the work equipment. In other words, in a leveling mechanism using a double-rod type dump cylinder 41 and an auxiliary cylinder 51 of the same diameter, as in the conventional Patent Document 1, the cylinder length is longer for the same stroke compared to a single-rod cylinder. As a result, the mounting position of the dump cylinder 41 and auxiliary cylinder 51 to the loader body and the lift-dump linkage mechanism are restricted, affecting the loader's inherent leveling accuracy and various design specifications.

[0031] Furthermore, in the leveling mechanism of conventional MX front loaders, the dump cylinder 41 is a double-rod type with different diameters, resulting in a longer cylinder length for the same stroke compared to a single-rod cylinder. This restricts the mounting position of the dump cylinder 41 and auxiliary cylinder 51 to the loader body, as well as the dump linkage mechanism, affecting the loader's inherent leveling accuracy and various design specifications. In addition, various special-sized cylinder materials are required depending on the loader model (size), but considering manufacturing costs and delivery times, it is necessary to consider standardization, which also affects the loader's inherent design specifications.

[0032] To achieve parallel lifting, the volume ratio of the dump cylinder and the auxiliary cylinder must be matched. However, if a double-rod type is selected for the dump cylinder and a single-rod double-acting type for the auxiliary cylinder, the specifications cannot be met with commercially available cylinder material diameters, and a special size must be selected, resulting in increased costs. Furthermore, if a commercially available size is selected, the negative pressure in the dump port of the dump cylinder 41 becomes too large during parallel lifting, rendering it unusable.

[0033] Currently, we are using special sizes, but we are unable to completely prevent negative pressure in the dump port. This is negatively impacting the durability of the sealing material.

[0034] On the other hand, the present invention provides a dump circuit D having a single-rod type dump cylinder 41, a single-acting auxiliary cylinder 51, and a pilot check valve C. Therefore, in addition to 1) reducing the cost of the dump cylinder, 2) preventing the generation of negative pressure, and 3) reducing the number of pipes, it is also possible to optimize the leveling mechanism. This makes it possible to freely design the work machine, freeing it from the design constraint that the volume ratio of the dump cylinder and the auxiliary cylinder must be matched.

[0035] ●Summary Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiments, the orientation of the lift cylinder 27 and the dump cylinder 41 may be reversed, with the cap side and the rod side being reversed.

[0036] Furthermore, if there is sufficient space, it is possible to install not just one auxiliary cylinder, but, for example, two side by side. Also, the lift arm 23 is not limited to a single piece; it can be changed to a type that can be bent in the middle of its longitudinal direction.

[0037] Furthermore, the end attachment is not limited to the bucket 32; various other end attachments such as forks, graders, roll grabs, container buckets, and loading hooks can be attached. The present invention is also applicable to various other work machines besides front loaders.

[0038] Furthermore, in the above embodiment, the lift arm 23 was raised and lowered by the extension and contraction of the lift cylinder 27, and the bucket 32 ​​was tilted up and down by the extension and contraction of the dump cylinder 41. However, conversely, it is also possible to configure the system so that the lift arm 23 is raised and lowered by the contraction and extension of the lift cylinder 27, and the bucket 32 ​​is tilted up and down by the contraction and extension of the dump cylinder 41. [Explanation of Symbols]

[0039] 10: Tractor 22: Support bracket 21: Front loader 23: Lift arm 27: Lift cylinder 27a: Lifting port 27b: Descent port 32: Bucket 41: Dump cylinder 41a: Dump port 41b: Squeeze port 51: Auxiliary cylinder 51a: Ascending port 51b: Descending port C: Pilot check valve D: Damp circuit F: Flow rate adjustment circuit L1, L2: Piping P: Hydraulic pump P': Pressure T: Hydraulic tank

Claims

1. A loader having a lift arm supported on a support bracket of a work vehicle so as to be able to move up and down, a work machine supported on the tip of the lift arm so as to be able to swing up and down, a lift cylinder disposed between the support bracket and the lift arm and moving up and down by extension and retraction, an auxiliary cylinder disposed between the support bracket and the lift arm and moving in conjunction with the lift cylinder, and a dump cylinder disposed between the lift arm and the work machine and swinging up and down by extension and retraction, The aforementioned dump cylinder is configured as a single-rod type, The squeezing port of the dump cylinder is connected to the lifting port of the auxiliary cylinder, while the dump port of the dump cylinder is connected to a hydraulic tank via a flow rate adjustment circuit branched from a dump circuit having a check valve. When the lift arm is raised, hydraulic pressure is supplied from the hydraulic pump to the lifting port of the lift cylinder, while the lowering port of the lift cylinder is connected to the dump port of the dump cylinder via the dump circuit and the check valve. When the lift arm is lowered, hydraulic pressure is supplied from a hydraulic pump to the lowering port of the lift cylinder, the rising port of the lift cylinder is connected to a hydraulic tank, and the dump port of the dump cylinder is connected to the hydraulic tank via the dump circuit and the check valve. A loader characterized by the following features.

2. The loader according to claim 1, characterized in that the check valve is configured as a pilot check valve, and when the pressure in the squee port of the dump cylinder rises, the pilot check valve is opened to connect the dump port of the dump cylinder to a hydraulic tank.

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