Hydraulic system for excavator, valve structure and engineering machinery

Abstract

The invention relates to the technical field of engineering machinery, and particularly discloses a hydraulic system for an excavator, a valve structure and engineering machinery, and the hydraulic system for the excavator comprises an oil tank, a back pressure valve, a first movable arm valve and an oil supplementing path. The output end of the back pressure valve is communicated with the oil tank; the first movable arm valve comprises a first port a, a second port a and a third port a, the first port a is used for being communicated with a movable arm rod cavity of the movable arm cylinder, the second port a is used for being communicated with a movable arm rodless cavity of the movable arm cylinder, the third port a is communicated with the input end of the back pressure valve, and when a valve element of the first movable arm valve is located at the floating position, the back pressure valve is connected with the back pressure valve. The first port a, the second port a and the third port a are communicated with one another; the oil supplementing oil way communicates with the third port a and is used for supplementing oil to the movable arm rod cavity and / or the movable arm rodless cavity. While floating adjustment of the movable arm cylinder is achieved, the structure of a hydraulic oil way is simplified, and the operation process of an operator is simplified when horizontal pushing operation is executed.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, and in particular to a hydraulic system for excavators, a valve structure, and engineering machinery. Background Technology

[0002] In the field of construction machinery, especially in earthmoving machinery such as excavators and loaders, pushing is a common working condition, which requires using working devices to push and level loose materials (such as sand, gravel, soil, etc.) along the ground.

[0003] Traditional horizontal pushing operation relies on the operator manually coordinating the control of three working devices: the stick, bucket, and boom, ensuring their synchronized horizontal movement. However, in actual operation, due to differences in the movement trajectories and hydraulic drive characteristics of each working device, the operator must manually adjust the extension and retraction of each device in real time by operating multiple control levers to maintain the bucket's contact with the ground and ensure horizontal pushing. This control method demands a high level of experience and skill from the operator, is difficult to coordinate, and is highly susceptible to problems such as the bucket scraping the ground or lifting off the ground due to asynchronous coordination, resulting in poor flatness and low efficiency.

[0004] Therefore, there is an urgent need for a hydraulic system, valve structure, and engineering machinery for excavators to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a hydraulic system, valve structure, and construction machinery for excavators, so as to solve the problem that existing excavators require the operator to coordinate multiple levers of the stick, bucket, and boom when performing horizontal pushing operations.

[0006] On one hand, the present invention provides a hydraulic system for excavators, the hydraulic system for excavators comprising: tank; Back pressure valve, the output end of which is connected to the oil tank. The first boom valve includes a first port a, a second port a, and a third port a. The first port a is used to communicate with the boom rod chamber of the boom cylinder, the second port a is used to communicate with the boom rodless chamber of the boom cylinder, and the third port a is connected to the input end of the back pressure valve. When the valve core of the first boom valve is in the floating position, the first port a, the second port a, and the third port a are interconnected. The oil replenishment circuit is connected to the third port a and is used to replenish oil to the boom rod chamber and / or the boom rodless chamber.

[0007] As a preferred embodiment of the hydraulic system for the excavator, the oil replenishment circuit includes a first pump body, and the input end of the first pump body is connected to the oil tank. The first boom valve also includes a fourth port a and a fifth port a. The output end of the first pump body is connected to the fourth port a, and the fifth port a is connected to the input end of the back pressure valve and the third port a, respectively. When the valve core of the first boom valve is in the floating position, the fourth port a is connected to the fifth port a.

[0008] As a preferred embodiment of the hydraulic system for the excavator, the first boom valve further includes a sixth port a, which is connected to the output end of the first pump body through a first check valve. The first check valve allows the oil to flow unidirectionally from the first pump body to the sixth port a. When the valve core of the first boom valve is in the lifting position, the first port a is connected to the third port a, and the sixth port a is connected to the second port a.

[0009] As a preferred embodiment of the aforementioned hydraulic system for excavators, it also includes: The second pump body has its input end connected to the oil delivery end of the oil tank. The second boom valve includes a first port b, a second port b, a third port b, a fourth port b, a fifth port b, and a sixth port b. The first port b is used to communicate with the boom rod chamber of the boom cylinder, the second port b is used to communicate with the boom rodless chamber of the boom cylinder, the third port b is connected to the input end of the back pressure valve, the fourth port b is connected to the output end of the second pump body, the fifth port b is connected to the input end of the back pressure valve, and the sixth port b is connected to the output end of the second pump body through a second check valve. The second check valve allows the oil to flow from the second pump body. When the valve core of the second boom valve is in the raised position, the first port b is connected to the third port b, and the sixth port b is connected to the second port b. When the valve core of the second boom valve is in the floating position, the fourth port b is connected to the fifth port b.

[0010] As a preferred embodiment of the hydraulic system for the excavator, when the valve core of the first boom valve is in the lowered position, the second port a is connected to the third port a, and the fourth port a is connected to the fifth port a. When the valve core of the second boom valve is in the lowered position, the second port b is connected to the third port b, and the sixth port b is connected to the first port b.

[0011] As a preferred embodiment of the aforementioned hydraulic system for excavators, it also includes: The second pump body has its input end connected to the oil delivery end of the oil tank. The boom valve includes a first port c, a second port c, a third port c, and a sixth port c. The first port c is used to communicate with the rod chamber of the boom cylinder, the second port c is used to communicate with the rodless chamber of the boom cylinder, the third port c is connected to the input end of the back pressure valve and the third port a respectively, and the sixth port c is connected to the output end of the second pump body through a third check valve. The third check valve allows the oil to flow unidirectionally from the second pump body to the sixth port c. When the valve core of the aforementioned boom valve is in the extended position, the sixth port c is connected to the second port c, and the first port c is connected to the third port c. When the valve core of the aforementioned boom valve is in the retracted position, the sixth port c is connected to the first port c, and the second port c is connected to the third port c.

[0012] As a preferred embodiment of the hydraulic system for the excavator, the boom valve further includes a fourth port c and a fifth port c. The fourth port c is connected to the output end of the second pump body, and the fifth port c is connected to the input end of the back pressure valve and the third port a. When the valve core of the aforementioned boom valve is in the locked position, the aforementioned fourth port c is connected to the aforementioned fifth port c.

[0013] The present invention also provides a valve structure suitable for the above-mentioned hydraulic system for excavators, the valve structure comprising: The valve island has a first return oil passage, a rodless chamber oil passage, a rod chamber oil passage, and a second return oil passage sequentially opened along a first direction. The first return oil passage and the second return oil passage are respectively used to connect to the return oil end of the oil tank. The rodless chamber oil passage is used to connect to the rodless chamber of the boom, and the rod chamber oil passage is used to connect to the rod chamber of the boom. The valve island also has a first mounting cavity, which is connected along the first direction to the first return oil passage, the rodless chamber oil passage, the rod chamber oil passage, and the second return oil passage. A first valve core is inserted into the first mounting cavity and can move relative to the valve island along the first direction. The first valve core is provided with a first guide oil passage and a second guide oil passage along the first direction. When the first valve core is in the floating position, the first guide oil passage connects the first return oil passage with the rodless chamber oil passage, and the second guide oil passage connects the rod chamber oil passage with the second return oil passage.

[0014] The present invention also provides an engineering machine, including the above-described hydraulic system for excavators, or the above-described valve structure.

[0015] As a preferred embodiment of the aforementioned engineering machinery, it further includes: a bucket, a bucket cylinder, a stick, a stick cylinder, a boom, and a boom cylinder. The body, boom, stick, and bucket are hinged end to end in sequence. The extension and retraction ends of the boom cylinder are respectively hinged to the body and the boom. The extension and retraction ends of the stick cylinder are respectively hinged to the boom and the stick. The extension and retraction ends of the bucket cylinder are respectively hinged to the boom and the bucket, which is used to complete the rotation of the bucket relative to the stick.

[0016] The hydraulic system, valve structure, and construction machinery for excavators provided by this invention have at least the following beneficial effects: The hydraulic system of this excavator includes an oil tank, a back pressure valve, a first boom valve, and a replenishing oil circuit. The output of the back pressure valve is connected to the oil tank. The first boom valve includes a first port a, a second port a, and a third port a. The first port a is connected to the rod chamber of the boom cylinder, the second port a is connected to the rodless chamber of the boom cylinder, and the third port a is connected to the input of the back pressure valve. When the valve core of the first boom valve is in the floating position, the first port a, the second port a, and the third port a are interconnected. The replenishing oil circuit is connected to the third port a and is used to replenish oil to the rod chamber and / or the rodless chamber of the boom.

[0017] The oil tank stores hydraulic fluid and includes an oil supply end and an oil return end. The oil tank supplies hydraulic fluid to the oil circuit through the oil supply end and recovers excess hydraulic fluid from the oil circuit through the oil return end. A back pressure valve is installed on the oil return end of the oil tank to maintain the hydraulic fluid pressure in the oil circuit. The back pressure valve has a preset opening pressure value and is normally closed. When the hydraulic fluid pressure upstream of the back pressure valve exceeds the opening pressure value, the back pressure valve opens, allowing hydraulic fluid in the oil circuit to return to the oil tank through the back pressure valve. The first boom valve includes three ports, denoted as first port a, second port a, and third port a. First port a communicates with the boom rod chamber, second port a communicates with the boom rodless chamber, and third port a communicates with the input end of the back pressure valve. When the valve core of the first boom valve is in the floating position, the boom rod chamber, the boom rodless chamber, and the input end of the back pressure valve are interconnected.

[0018] The excavator's actuators include a bucket, bucket cylinder, stick, stick cylinder, boom, and boom cylinder. The body, boom, stick, and bucket are hinged sequentially end-to-end. The boom cylinder's extension and retraction ends are hinged to the body and boom respectively, driving the boom's rotation relative to the body to adjust the bucket's ground clearance. The stick cylinder's extension and retraction ends are hinged to the boom and stick respectively, driving the stick's rotation relative to the boom to adjust the bucket's distance from the body in the forward / backward direction. The bucket cylinder's extension and retraction ends are hinged to the boom and bucket respectively, driving the bucket's rotation relative to the stick. During direct thrust operation, the bucket is placed on the ground and moves with the terrain. The valve core of the first boom valve is in a floating position, meaning the boom cylinder does not actively drive the boom's extension and retraction during this process. The boom holds the bucket firmly against the ground by gravity, while the bucket cylinder, through extension and retraction, drives the stick to rotate relative to the boom, moving the bucket forward / backward. When the bucket passes over a protrusion, the protrusion supports the bucket's upward movement, causing the boom cylinder to deploy. This compresses the boom rod chamber and enlarges the boom rodless chamber. Part of the oil in the boom rod chamber flows into the boom rodless chamber through port a1 and port a2, while the other part flows through port a1 and port a3 to the input of the back pressure valve. If the pressure of this portion of oil exceeds the opening pressure of the back pressure valve, it returns to the oil tank through the back pressure valve. When the bucket passes over a depression, the bucket descends, causing the boom cylinder to contract. This compresses the boom rodless chamber and enlarges the boom rod chamber. Part of the oil in the boom rodless chamber flows through port a2 and port a1 to replenish the boom rod chamber, while the other part flows through port a2 and port a3 to the input of the back pressure valve. If the pressure of this portion of oil exceeds the opening pressure of the back pressure valve, it returns to the oil tank through the back pressure valve.

[0019] Because some oil always flows back to the oil tank when the oil circulates between the boom rod chamber and the boom rodless chamber, this reduces the total oil volume in the boom cylinder. To address this, this application also provides a replenishing oil circuit, which is connected to the third port a. The replenishing oil circuit can continuously replenish oil to the third port a. When the oil pressure in the replenishing oil circuit is lower than the oil pressure on the boom cylinder side, the oil in the boom cylinder flows to the input end of the back pressure valve through the third port a. When the oil pressure on the boom cylinder side is lower than the oil pressure in the replenishing oil circuit, the replenishing oil circuit enters the boom rodless chamber or the boom rod chamber through the third port a, the second port a, or the first port a to replenish oil and stabilize the pressure.

[0020] In this way, while realizing the floating adjustment of the boom cylinder, the structure of the hydraulic circuit is simplified, which simplifies the operator's operation process when performing horizontal pushing operations. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the hydraulic system (floating) for excavators in an embodiment of the present invention. Figure 1 ; Figure 2This is a schematic diagram of the hydraulic system (floating) for excavators in an embodiment of the present invention. Figure 2 ; Figure 3 This is a schematic diagram of the hydraulic system (lifting) for an excavator in an embodiment of the present invention; Figure 4 This is a schematic diagram of the hydraulic system (lowering) for an excavator in an embodiment of the present invention; Figure 5 This is a schematic diagram of the hydraulic system (including boom and stick) for an excavator in an embodiment of the present invention; Figure 6 This is a schematic diagram of the valve structure in an embodiment of the present invention.

[0022] In the picture: X, first direction; 1. Fuel tank; 2. Back pressure valve; 3. First boom valve; 31. First port a; 32. Second port a; 33. Third port a; 34. Fourth port a; 35. Fifth port a; 36. Sixth port a; 4. First pump body; 5. First check valve; 6. Second pump body; 7. Second boom valve; 71. First port b; 72. Second port b; 73. Third port b; 74. Fourth port b; 75. Fifth port b; 76. Sixth port b; 8. Second check valve; 9. Stalk valve; 91. First port c; 92. Second port c; 93. Third port c; 94. Fourth port c; 95. Fifth port c; 96. Sixth port c; 10. Third check valve; 11. Valve island; 111. First return oil circuit; 112. Rodless chamber oil circuit; 113. Rod chamber oil circuit; 114. Second return oil circuit; 12. First valve core; 121. First guide oil passage; 122. Second guide oil passage; 100. Boom cylinder; 110. Rodless boom chamber; 120. Rod-operated boom chamber; 200. Boom; 300. Rod cylinder; 310. Rodless chamber; 320. Rod with rod chamber; 400, boom; 500, bucket cylinder; 600, bucket; 700, vehicle body. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Furthermore, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] like Figures 1 to 5As shown, this embodiment provides a hydraulic system for an excavator, which includes an oil tank 1, a back pressure valve 2, a first boom valve 3, and a replenishing oil circuit. The output end of the back pressure valve 2 is connected to the oil tank 1. The first boom valve 3 includes a first port a31, a second port a32, and a third port a33. The first port a31 is connected to the boom rod chamber 120 of the boom cylinder 100, the second port a32 is connected to the boom rodless chamber 110 of the boom cylinder 100, and the third port a33 is connected to the input end of the back pressure valve 2. When the valve core of the first boom valve 3 is in a floating position, the first port a31, the second port a32, and the third port a33 are interconnected. The replenishing oil circuit is connected to the third port a33 and is used to replenish oil to the boom rod chamber 120 and / or the boom rodless chamber 110.

[0028] For example, oil tank 1 stores oil and includes an oil supply end and an oil return end. Oil tank 1 supplies oil to the oil circuit through the oil supply end and recovers excess oil from the oil circuit through the oil return end. Back pressure valve 2 is installed at the oil return end of oil tank 1 to maintain the oil pressure in the oil circuit. Back pressure valve 2 has a preset opening pressure value and is normally closed. When the oil pressure upstream of back pressure valve 2 is greater than the opening pressure value of back pressure valve 2, back pressure valve 2 opens, and oil in the oil circuit can return to oil tank 1 through back pressure valve 2. The first boom valve 3 includes three ports, denoted as first port a31, second port a32, and third port a33. First port a31 is used to communicate with the boom rod chamber 120, second port a32 is used to communicate with the boom rodless chamber 110, and third port a33 is connected to the input end of back pressure valve 2. When the valve core of the first boom valve 3 is in the floating position, the boom rod chamber 120, the boom rodless chamber 110, and the input end of the back pressure valve 2 are interconnected.

[0029] The excavator's actuators include a bucket 600, a bucket cylinder 500, a stick 400, a stick cylinder 300, a boom 200, and a boom cylinder 100. The body 700, boom 200, stick 400, and bucket 600 are hinged end to end. The telescopic ends of the boom cylinder 100 are hinged to the body 700 and boom 200 respectively, and are used to drive the boom 200 to rotate relative to the body 700 to adjust the distance between the bucket 600 and the ground. The telescopic ends of the stick cylinder 300 are hinged to the boom 200 and stick 400 respectively, and are used to drive the stick 400 to rotate relative to the boom 200 to adjust the distance between the bucket 600 and the body 700 in the front-to-back direction. The telescopic ends of the bucket cylinder 500 are hinged to the boom 200 and bucket 600 respectively, and are used to rotate the bucket 600 relative to the stick 400. During the direct thrust operation, the bucket 600 is placed on the ground and moves with the terrain. The valve core of the first boom valve 3 is in a floating position, meaning that the boom cylinder 100 does not actively drive the boom 200 to extend or retract during this process. The boom 200 holds the bucket 600 close to the ground by gravity. The bucket cylinder 500, through extension and retraction, drives the stick 400 to rotate relative to the boom 200, moving the bucket 600 in the forward and backward direction. When the bucket 600 passes a protrusion, the protrusion supports the bucket 600 to rise, causing the boom cylinder 100 to extend, compressing the boom rod chamber 120, and enlarging the boom rodless chamber 110. Part of the oil in the boom rod chamber 120 enters the boom rodless chamber 110 through the first port a31 and the second port a32, while the other part enters the input end of the back pressure valve 2 through the first port a31 and the third port a33. If the pressure of this part of the oil is greater than the opening pressure value of the back pressure valve 2, it returns to the oil tank 1 through the back pressure valve 2. When the bucket 600 passes over a depression, the bucket 600 descends, causing the boom cylinder 100 to contract, the boom rodless chamber 110 to compress, and the boom rod chamber 120 to enlarge. Part of the oil in the boom rodless chamber 110 is replenished into the boom rod chamber 120 through the second port a32 and the first port a31, and another part enters the input end of the back pressure valve 2 through the second port a32 and the third port a33. If the pressure of this part of the oil is greater than the opening pressure value of the back pressure valve 2, it returns to the oil tank 1 through the back pressure valve 2.

[0030] Because some oil always flows back to the oil tank 1 when the oil circulates between the boom rod chamber 120 and the boom rodless chamber 110, this results in a decrease in the total oil volume in the boom cylinder 100. To address this, this application also provides a replenishing oil circuit, which is connected to the third port a33. The replenishing oil circuit can continuously replenish oil to the third port a33. When the oil pressure in the replenishing oil circuit is less than the oil pressure on the boom cylinder 100 side, the oil in the boom cylinder 100 flows to the input end of the back pressure valve 2 through the third port a33. When the oil pressure on the boom cylinder 100 side is less than the oil pressure in the replenishing oil circuit, the replenishing oil circuit enters the boom rodless chamber 110 or the boom rod chamber 120 through the third port a33, the second port a32, or the first port a31 to replenish oil and stabilize the pressure.

[0031] In this way, while realizing the floating adjustment of the boom cylinder 100, the structure of the hydraulic circuit is simplified, which simplifies the operator's operation process when performing horizontal pushing operation.

[0032] Optionally, the oil replenishment circuit includes a first pump body 4, the input end of which is connected to the oil tank 1; the first boom valve 3 also includes a fourth port a34 and a fifth port a35, the output end of the first pump body 4 is connected to the fourth port a34, and the fifth port a35 is connected to the input end of the back pressure valve 2 and the third port a33 respectively; when the valve core of the first boom valve 3 is in the floating position, the fourth port a34 and the fifth port a35 are connected.

[0033] For example, the first pump body 4 is kept in a normally open state to supply oil from the oil tank 1 to the oil circuit. The oil can pass through the fourth port a34 and the fifth port a35 in sequence. A portion of the oil flows to the input end of the back pressure valve 2. If the opening condition of the back pressure valve 2 is met, this portion of the oil can flow back to the oil tank 1. Another portion of the oil flows to the third port a33. If the pressure value of this portion of the oil is greater than the pressure value of the boom rod chamber 120, it is injected into the boom rod chamber 120. And / or, if the pressure value of this portion of the oil is greater than the pressure value of the boom rodless chamber 110, it is injected into the boom rodless chamber 110, thereby continuously replenishing the boom cylinder 100 with oil to stabilize the pressure.

[0034] Furthermore, a pressure sensor is installed at the output end of the back pressure valve 2. The pressure sensor is used to detect the oil pressure upstream of the back pressure valve 2. When the upstream oil pressure approaches the opening pressure value of the back pressure valve 2, the pressure sensor communicates with the first pump body 4 and commands the first pump body 4 to reduce the output power.

[0035] Optionally, the first boom valve 3 also includes a sixth port a36, which is connected to the output end of the first pump body 4 through a first check valve 5. The first check valve 5 allows oil to flow unidirectionally from the first pump body 4 to the sixth port a36. When the valve core of the first boom valve 3 is in the lifting position, the first port a31 is connected to the third port a33, and the sixth port a36 is connected to the second port a32.

[0036] For example, when the valve core of the first boom valve 3 is in the raised position, the oil in the oil tank 1 is drawn out by the first pump body 4 and enters the boom rodless chamber 110 after passing through the sixth port a36 and the second port a32 in sequence. This increases the pressure in the boom rodless chamber 110, causing the piston to move towards the boom rod chamber 120 and squeeze the boom rod chamber 120. The boom cylinder 100 then extends. Due to the increased pressure, the oil in the boom rod chamber 120 is discharged from the boom rod chamber 120 and flows to the back pressure valve 2 after passing through the first port a31 and the third port a33 in sequence. If the opening conditions of the back pressure valve 2 are met, the oil flows back to the oil tank 1.

[0037] Optionally, the hydraulic system for the excavator also includes a second pump body 6 and a second boom valve 7. The second pump body 6 has its input end connected to the oil tank 1's oil delivery end. The second boom valve 7 includes a first port b71, a second port b72, a third port b73, a fourth port b74, a fifth port b75, and a sixth port b76. The first port b71 is connected to the boom rod chamber 120, the second port b72 is connected to the boom rodless chamber 110, the third port b73 is connected to the input end of the back pressure valve 2, the fourth port b74 is connected to the output end of the second pump body 6, the fifth port b75 is connected to the input end of the back pressure valve 2, and the sixth port b76 is connected to the output end of the second pump body 6 through a second check valve 8. The second check valve 8 allows oil to flow from the second pump body 6. When the valve core of the second boom valve 7 is in the raised position, the first port b71 is connected to the third port b73, and the sixth port b76 is connected to the second port b72. When the valve core of the second boom valve 7 is in the floating position, the fourth port b74 is connected to the fifth port b75.

[0038] For example, when the valve core of the second boom valve 7 is in the raised position, the second pump body 6 starts, drawing oil from the oil tank 1. The oil passes through the sixth port b76 and the second port b72 in sequence before entering the boom rodless chamber 110, increasing the pressure in the boom rodless chamber 110. This causes the piston to move towards the boom rod chamber 120, squeezing the boom rod chamber 120, and the boom cylinder 100 extends. Due to the increased pressure, the oil in the boom rod chamber 120 is discharged from the boom rod chamber 120 and flows through the first port b71 and the third port b73 in sequence to the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, the oil flows back to the oil tank 1.

[0039] Thus, when the boom 200 needs to be lifted, the valve core of the first boom valve 3 moves to the lifting position, and the valve core of the second boom valve 7 moves to the lifting position. The first pump body 4 and the second pump body 6 can simultaneously provide oil to the boom rodless chamber 110 and depressurize the boom rod chamber 120, so that the boom rodless chamber 110 can be pressed quickly. On the one hand, this can increase the lifting speed of the boom 200, and on the other hand, it can enable the boom 200 to have a larger load capacity.

[0040] When the boom 200 needs to be in a floating state, the valve core of the first boom valve 3 and the valve core of the second boom valve 7 are in a floating position. After the second pump body 6 draws oil from the oil tank 1, the oil flows through the fourth port b74, the fifth port b75, and the input end of the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, the oil flows back into the oil tank 1. The second pump body 6 and the second boom valve 7, in the floating state of the boom 200, are mainly used to stabilize the pressure in the oil circuit.

[0041] Furthermore, the oil discharged from the fifth port b75 can also flow to the third port a33 of the first boom valve 3 to replenish the oil in the boom rod chamber 120 and / or the boom rodless chamber 110.

[0042] Optionally, when the valve core of the first boom valve 3 is in the lowered position, the second port a32 is connected to the third port a33, and the fourth port a34 is connected to the fifth port a35; when the valve core of the second boom valve 7 is in the lowered position, the second port b72 is connected to the third port b73, and the sixth port b76 is connected to the first port b71.

[0043] For example, when the boom 200 needs to be lowered, the valve core of the second boom valve 7 is adjusted to the lowered position, and the second pump body 6 draws oil from the oil tank 1. The oil can sequentially pass through the sixth port b76 and the first port b71 into the boom rod chamber 120, increasing the pressure inside the boom rod chamber 120. This pushes the piston to move towards the boom rodless chamber 110, and the oil in the boom rodless chamber 110 is squeezed out of the boom rodless chamber 110. It then sequentially passes through the second port b72, the third port b73, and the input end of the back pressure valve 2. If the back pressure valve 2 opening condition is met, the oil enters the oil tank 1. The valve core of the first boom valve 3 is adjusted to the lowered position, and part of the oil in the boom rodless chamber 110 flows to the second boom valve 7, while the other part flows to the first boom valve 3. It then sequentially passes through the second port a32, the third port a33, and the input end of the back pressure valve 2. If the back pressure valve 2 opening condition is met, the oil enters the oil tank 1.

[0044] Thus, the first boom valve 3 and the second boom valve 7 provide pressure relief channels for the boom rodless chamber 110, enabling rapid pressure relief of the boom rodless chamber 110. On the one hand, this can increase the lowering speed of the boom 200, and on the other hand, it can reduce the driving pressure of the boom rod chamber 120.

[0045] like Figure 5 As shown, the hydraulic system for the excavator also includes a second pump body 6 and a stick valve 9. The input end of the second pump body 6 is connected to the oil supply end of the oil tank 1. The stick valve 9 includes a first port c91, a second port c92, a third port c93, and a sixth port c96. The first port c91 is used to connect with the rod chamber 320 of the stick cylinder 300, the second port c92 is used to connect with the rodless chamber 310 of the stick cylinder 300, and the third port c93 is connected to the input end of the back pressure valve 2 and the third port a33. The sixth port c96 is connected to the output end of the second pump body 6 through the third check valve 10. The third check valve 10 allows oil to flow unidirectionally from the second pump body 6 to the sixth port c96. When the valve core of the boom valve 9 is in the extended position, the sixth port c96 is connected to the second port c92, and the first port c91 is connected to the third port c93. When the valve core of the boom valve 9 is in the retracted position, the sixth port c96 is connected to the first port c91, and the second port c92 is connected to the third port c93.

[0046] For example, when the excavator performs a horizontal pushing operation, the valve core of the first boom valve 3 is adjusted to the floating position, so that the boom 200 can move with the undulations of the terrain. The stick cylinder 300 needs to actively extend or retract to drive the bucket 600 to move back and forth. When the bucket 600 needs to move forward, the valve core of the stick valve 9 is in the extended position. The oil drawn from the oil tank 1 by the second pump body 6 enters the stick rodless chamber 310 through the sixth port c96 and the second port c92. Inside, the increased pressure in the rodless chamber 310 of the boom drives the piston to move towards the rod chamber 320 of the boom, causing the boom 400 to extend. The oil in the rod chamber 320 then flows sequentially through the first port c91 and the third port c93. Part of the oil flows to the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, the oil returns to the oil tank 1 through the back pressure valve 2. The other part flows to the third port a33 to replenish the oil in the rod chamber 320 and / or the rodless chamber 310 of the boom cylinder 100. When the bucket 600 needs to move backward, the valve core of the boom valve 9 is in the retracted position. The oil pumped from the oil tank 1 by the second pump body 6 passes through the sixth port c96 and the first port c91 in sequence and enters the boom rod chamber 320. The pressure in the boom rod chamber 320 increases, driving the piston to move towards the boom rodless chamber 310. The boom 400 extends, and the oil in the boom rodless chamber 310 passes through the second port c92 and the third port c93 in sequence. Part of the oil flows to the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, it returns to the oil tank 1 through the back pressure valve 2. The other part flows to the third port a33 to replenish the oil in the boom rodless chamber 310 and / or the boom rod chamber 320 of the boom cylinder 100.

[0047] Optionally, the boom valve 9 also includes a fourth port c94 and a fifth port c95. The fourth port c94 is connected to the output end of the second pump body 6, and the fifth port c95 is connected to the input end of the back pressure valve 2 and the third port a33. When the valve core of the boom valve 9 is in the locked position, the fourth port c94 and the fifth port c95 are connected.

[0048] When the boom 400 needs to remain stationary, the valve core of the boom valve 9 is adjusted to the locked position. At this time, the oil output from the second pump body 6 can flow sequentially through the fourth port c94 and the fifth port c95 to the back pressure valve 2 and the third port a33. However, the oil in the boom rod chamber 320 and the boom rod rodless chamber 310 cannot be exchanged with the oil circuit through the boom valve 9, so that the pressure on both sides of the piston is relatively stable, thereby locking the length of the boom cylinder 300.

[0049] Optionally, the hydraulic system for excavators may also include: The second boom valve 7 includes a first port b71, a second port b72, a third port b73, a fourth port b74, a fifth port b75, and a sixth port b76. The first port b71 is connected to the boom rod chamber 120; the second port b72 is connected to the boom rodless chamber 110; the third port b73 is connected to the input end of the back pressure valve 2; the fourth port b74 is connected to the output end of the second pump body 6; the fifth port b75 and the sixth port b76 are connected via a third check valve 10; and the fifth port b75 is also connected to the fourth port b94. The sixth port b76 is connected to the output end of the second pump body 6 through the second check valve 8, which allows oil to flow from the second pump body 6; when the valve core of the second boom valve 7 is in the locked position, the fourth port b74 is connected to the fifth port b75; when the valve core of the second boom valve 7 is in the raised position b, the first port b71 is connected to the third port b73, and the sixth port b76 is connected to the second port b72; when the valve core of the second boom valve 7 is in the lowered position, the second port b72 is connected to the third port b73, and the sixth port b76 is connected to the first port b71.

[0050] For example, when the valve core of the second boom valve 7 is in the raised position, the second pump body 6 starts, drawing oil from the oil tank 1. The oil passes through the sixth port b76 and the second port b72 in sequence before entering the boom rodless chamber 110, increasing the pressure in the boom rodless chamber 110. This causes the piston to move towards the boom rod chamber 120, squeezing the boom rod chamber 120, and the boom cylinder 100 extends. Due to the increased pressure, the oil in the boom rod chamber 120 is discharged from the boom rod chamber 120 and flows through the first port b71 and the third port b73 in sequence to the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, the oil flows back to the oil tank 1.

[0051] Thus, when the boom 200 needs to be lifted, the valve core of the first boom valve 3 moves to the lifting position, and the valve core of the second boom valve 7 moves to the lifting position. The first pump body 4 and the second pump body 6 can simultaneously provide oil to the boom rodless chamber 110 and depressurize the boom rod chamber 120, so that the boom rodless chamber 110 can be pressed quickly. On the one hand, this can increase the lifting speed of the boom 200, and on the other hand, it can enable the boom 200 to have a larger load capacity.

[0052] When the boom 200 needs to be in a floating state, the valve core of the first boom valve 3 and the valve core of the second boom valve 7 are in a floating position. After the second pump body 6 draws oil from the oil tank 1, the oil flows through the fourth port b74, the fifth port b75, and the input end of the back pressure valve 2. If the opening conditions of the back pressure valve 2 are met, the oil flows back into the oil tank 1. The second pump body 6 and the second boom valve 7, in the floating state of the boom 200, are mainly used to stabilize the pressure in the oil circuit.

[0053] Furthermore, the oil discharged from the fifth port b75 can also flow to the third port a33 of the first boom valve 3 to replenish the oil in the boom rod chamber 120 and / or the boom rodless chamber 110.

[0054] Optionally, when the valve core of the first boom valve 3 is in the lowered position, the second port a32 is connected to the third port a33, and the fourth port a34 is connected to the fifth port a35; when the valve core of the second boom valve 7 is in the lowered position, the second port b72 is connected to the third port b73, and the sixth port b76 is connected to the first port b71.

[0055] For example, when the boom 200 needs to be lowered, the valve core of the second boom valve 7 is adjusted to the lowered position, and the second pump body 6 draws oil from the oil tank 1. The oil can sequentially pass through the sixth port b76 and the first port b71 into the boom rod chamber 120, increasing the pressure inside the boom rod chamber 120. This pushes the piston to move towards the boom rodless chamber 110, and the oil in the boom rodless chamber 110 is squeezed out of the boom rodless chamber 110. It then sequentially passes through the second port b72, the third port b73, and the input end of the back pressure valve 2. If the back pressure valve 2 opening condition is met, the oil enters the oil tank 1. The valve core of the first boom valve 3 is adjusted to the lowered position, and part of the oil in the boom rodless chamber 110 flows to the second boom valve 7, while the other part flows to the first boom valve 3. It then sequentially passes through the second port a32, the third port a33, and the input end of the back pressure valve 2. If the back pressure valve 2 opening condition is met, the oil enters the oil tank 1.

[0056] It should be noted that when the valve core of the second boom valve 7 is adjusted to the lowered or raised position, the fifth port b75 of the second boom valve 7 is disconnected from the output end of the second pump body 6. The fifth port b75 cannot supply oil to the fourth port c94 or the sixth port c96 of the stick valve 9 to drive the stick cylinder 300 to extend or retract. That is, the second pump body 6 can only supply oil to the stick valve 9 when the second boom valve 7 is in the floating position.

[0057] like Figure 6As shown, a valve structure is also provided, suitable for the aforementioned hydraulic system for excavators. The valve structure includes a valve island 11 and a first valve core 12. The valve island 11 has a first return oil passage 111, a rodless chamber oil passage 112, a rod chamber oil passage 113, and a second return oil passage 114 sequentially arranged along a first direction X. The first return oil passage 111 and the second return oil passage 114 are respectively used to connect to the return oil end of the oil tank 1. The rodless chamber oil passage 112 is used to connect to the boom rodless chamber 110, and the rod chamber oil passage 113 is used to connect to the boom rod chamber 120. The valve island 11 also has a first mounting cavity, which is connected along the first direction X to the first return oil passage 111, the rodless chamber oil passage 112, the rod chamber oil passage 113, and the second return oil passage 114. The valve core 12 has a rod chamber oil passage 112, a rod chamber oil passage 113, and a second return oil passage 114. The first valve core 12 is inserted into the first mounting cavity and can move relative to the valve island 11 along the first direction X. The first valve core 12 has a first guide oil passage 121 and a second guide oil passage 122 along the first direction X. When the first valve core 12 is in the floating position, the first guide oil passage 121 connects the first return oil passage 111 and the rodless chamber oil passage 112, and the second guide oil passage 122 connects the rod chamber oil passage 113 and the second return oil passage 114.

[0058] An engineering machine is also provided, including the hydraulic system for the excavator described above, or the valve structure described above.

[0059] Optionally, the construction machinery also includes: bucket 600, bucket cylinder 500, stick 400, stick cylinder 300, boom 200 and boom cylinder 100. The body 700, boom 200, stick 400 and bucket 600 are hinged end to end. The telescopic ends of boom cylinder 100 are hinged to body 700 and boom 200 respectively. The telescopic ends of stick cylinder 300 are hinged to boom 200 and stick 400 respectively. The telescopic ends of bucket cylinder 500 are hinged to boom 200 and bucket 600 respectively, and are used to complete the rotation of bucket 600 relative to stick 400.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hydraulic system for an excavator, characterized in that, include: Fuel tank (1); Back pressure valve (2), the output end of which is connected to the oil tank (1); The first boom valve (3) includes a first port a (31), a second port a (32) and a third port a (33). The first port a (31) is used to communicate with the boom rod chamber (120) of the boom cylinder (100). The second port a (32) is used to communicate with the boom rodless chamber (110) of the boom cylinder (100). The third port a (33) is connected to the input end of the back pressure valve (2). When the valve core of the first boom valve (3) is in the floating position, the first port a (31), the second port a (32) and the third port a (33) are interconnected. The oil replenishment circuit is connected to the third port a (33) and is used to replenish oil to the boom rod chamber (120) and / or the boom rodless chamber (110).

2. The hydraulic system for excavators according to claim 1, characterized in that, The oil replenishment circuit includes a first pump body (4), and the input end of the first pump body (4) is connected to the oil tank (1); The first boom valve (3) also includes a fourth port a (34) and a fifth port a (35). The output end of the first pump body (4) is connected to the fourth port a (34), and the fifth port a (35) is connected to the input end of the back pressure valve (2) and the third port a (33), respectively. When the valve core of the first boom valve (3) is in the floating position, the fourth port a (34) is connected to the fifth port a (35).

3. The hydraulic system for excavators according to claim 2, characterized in that, The first boom valve (3) also includes a sixth port a (36), which is connected to the output end of the first pump body (4) through a first check valve (5). The first check valve (5) allows the oil to flow unidirectionally from the first pump body (4) to the sixth port a (36). When the valve core of the first boom valve (3) is in the lifting position, the first port a (31) is connected to the third port a (33), and the sixth port a (36) is connected to the second port a (32).

4. The hydraulic system for excavators according to claim 2, characterized in that, Also includes: The second pump body (6) has its input end connected to the oil supply end of the oil tank (1); The second boom valve (7) includes a first port b (71), a second port b (72), a third port b (73), a fourth port b (74), a fifth port b (75), and a sixth port b (76). The first port b (71) is connected to the boom rod chamber (120), the second port b (72) is connected to the boom rodless chamber (110), the third port b (73) is connected to the input end of the back pressure valve (2), the fourth port b (74) is connected to the output end of the second pump body (6), the fifth port b (75) is connected to the input end of the back pressure valve (2), and the sixth port b (76) is connected to the output end of the second pump body (6) through a second check valve (8). The second check valve (8) allows the oil to flow from the second pump body (6). When the valve core of the second boom valve (7) is in the lifting position, the first port b (71) is connected to the third port b (73), and the sixth port b (76) is connected to the second port b (72); When the valve core of the second boom valve (7) is in the floating position, the fourth port b (74) is connected to the fifth port b (75).

5. The hydraulic system for excavators according to claim 4, characterized in that, When the valve core of the first boom valve (3) is in the lowered position, the second port a (32) is connected to the third port a (33), and the fourth port a (34) is connected to the fifth port a (35); When the valve core of the second boom valve (7) is in the lowered position, the second port b (72) is connected to the third port b (73), and the sixth port b (76) is connected to the first port b (71).

6. The hydraulic system for excavators according to any one of claims 1-5, characterized in that, Also includes: The second pump body (6) has its input end connected to the oil supply end of the oil tank (1); The boom valve (9) includes a first port c (91), a second port c (92), a third port c (93), and a sixth port c (96). The first port c (91) is used to communicate with the rod chamber (320) of the boom cylinder (300). The second port c (92) is used to communicate with the rodless chamber (310) of the boom cylinder (300). The third port c (93) is connected to the input end of the back pressure valve (2) and the third port a (33) respectively. The sixth port c (96) is connected to the output end of the second pump body (6) through a third check valve (10). The third check valve (10) allows the oil to flow unidirectionally from the second pump body (6) to the sixth port c (96). When the valve core of the boom valve (9) is in the extended position, the sixth port c (96) is connected to the second port c (92), and the first port c (91) is connected to the third port c (93); When the valve core of the boom valve (9) is in the retracted position, the sixth port c (96) is connected to the first port c (91), and the second port c (92) is connected to the third port c (93).

7. The hydraulic system for excavators according to claim 6, characterized in that, The boom valve (9) also includes a fourth port c (94) and a fifth port c (95). The fourth port c (94) is connected to the output end of the second pump body (6), and the fifth port c (95) is connected to the input end of the back pressure valve (2) and the third port a (33). When the valve core of the boom valve (9) is in the locked position, the fourth port c (94) is connected to the fifth port c (95).

8. A valve structure suitable for the hydraulic system of an excavator as described in any one of claims 1-7, characterized in that, The valve structure includes: The valve island (11) is provided with a first return oil passage (111), a rodless chamber oil passage (112), a rod chamber oil passage (113), and a second return oil passage (114) in sequence along the first direction (X). The first return oil passage (111) and the second return oil passage (114) are respectively used to communicate with the return oil end of the oil tank (1). The rodless chamber oil passage (112) is used to communicate with the rodless chamber (110) of the boom. The rod chamber oil passage (113) is used to communicate with the rod chamber (120) of the boom. The valve island (11) is also provided with a first mounting cavity, which is connected to the first return oil passage (111), the rodless chamber oil passage (112), the rod chamber oil passage (113), and the second return oil passage (114) along the first direction (X). The first valve core (12) is inserted into the first mounting cavity and can move relative to the valve island (11) along the first direction (X). The first valve core (12) is provided with a first guide oil passage (121) and a second guide oil passage (122) along the first direction (X). When the first valve core (12) is in the floating position, the first guide oil passage (121) connects the first return oil passage (111) and the rodless chamber oil passage (112), and the second guide oil passage (122) connects the rod chamber oil passage (113) and the second return oil passage (114).

9. An engineering machinery, characterized in that, Includes the hydraulic system for excavators as described in any one of claims 1-7, or the valve structure as described in claim 8.

10. The engineering machinery according to claim 9, characterized in that, Also includes: The bucket (600), bucket cylinder (500), stick (400), stick cylinder (300), boom (200), and boom cylinder (100) are connected end to end in sequence. The extension and retraction ends of the boom cylinder (100) are respectively connected to the body 700 and the boom (200). The extension and retraction ends of the stick cylinder (300) are respectively connected to the boom (200) and the stick (400). The extension and retraction ends of the bucket cylinder (500) are respectively connected to the boom (200) and the bucket (600), which are used to complete the rotation of the bucket (600) relative to the stick (400).

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