Hydraulic oil cylinder and engineering machinery

Abstract

The utility model provides a hydraulic oil cylinder and engineering machinery, and the hydraulic oil cylinder comprises a cylinder barrel which is provided with a first hydraulic cavity; the main piston rod is arranged in the first hydraulic cavity and divides the first hydraulic cavity into a first rodless cavity and a first rod cavity, a second hydraulic cavity is formed in the main piston rod, a first oil hole and a second oil hole are formed in the cylinder barrel, the first oil hole is communicated with the first rodless cavity and the oil tank, and the second oil hole is communicated with the first rod cavity and the oil tank; the auxiliary piston rod extends into the second hydraulic cavity from the first rodless cavity and divides the second hydraulic cavity into a second rodless cavity and a second rod cavity, the second rod cavity is communicated with the first rod cavity, and the auxiliary piston rod is provided with an auxiliary oil channel communicated with the first rodless cavity and the second rodless cavity. Compared with the prior art, under the same oil cylinder outer diameter, the action area is larger, larger thrust can be provided to adapt to the heavy-load working condition, and under the same load, the hydraulic oil cylinder can be made to be smaller, lighter and more convenient to install.

Description

Technical Field

[0001] This utility model belongs to the field of engineering machinery technology, and in particular relates to a hydraulic cylinder and engineering machinery. Background Technology

[0002] like Figure 1 The diagram shows a hydraulic cylinder in a conventional engineering machine, such as a truck crane. The first port of the hydraulic cylinder is the oil port for the rodless chamber, and the second port is the oil port for the rod chamber. When the piston rod extends, high-pressure oil enters through the first port and acts on the front end face of the piston rod, pushing it out of the rod chamber. Hydraulic oil then flows out through the second port back to the oil tank. The thrust divided by the area of ​​the front end face of the piston rod is the load pressure. When the piston rod retracts, high-pressure oil enters the rod chamber through the second port and acts on the rear end face of the piston rod. Hydraulic oil in the rodless chamber is discharged through the first port back to the oil tank.

[0003] When a hydraulic cylinder requires a large thrust, and the hydraulic system is under high pressure, the required quality of the hydraulic components is also high. When the rated pressure of the hydraulic system is fixed, the only way to achieve a large thrust is to increase the diameter of the hydraulic cylinder. However, the weight and installation dimensions of the hydraulic cylinder are generally limited, and increasing the cylinder diameter makes installation of the hydraulic cylinder inconvenient. Utility Model Content

[0004] The main purpose of this utility model is to propose a hydraulic cylinder and engineering machinery, which aims to solve the technical problem that existing hydraulic cylinders cannot simultaneously meet the requirements of large thrust and convenient installation.

[0005] To achieve the above objectives, this utility model provides a hydraulic cylinder, comprising: a cylinder barrel having a first hydraulic chamber; a main piston rod disposed within the first hydraulic chamber, dividing the first hydraulic chamber into a first rodless chamber and a first rod chamber, a second hydraulic chamber being disposed within the main piston rod; a first oil hole and a second oil hole being provided on the cylinder barrel, the first oil hole connecting the first rodless chamber and an oil tank, and the second oil hole connecting the first rod chamber and an oil tank; and a secondary piston rod extending from the first rodless chamber into the second hydraulic chamber, dividing the second hydraulic chamber into a second rodless chamber and a second rod chamber, the second rod chamber connecting to the first rod chamber; and an auxiliary oil passage connecting the first rodless chamber and the second rodless chamber being provided on the secondary piston rod.

[0006] In this embodiment of the utility model, the auxiliary oil passage includes: a hollow hole that penetrates the auxiliary piston rod along the axial direction and connects to the second rodless chamber; and a third oil hole that connects to the first rodless chamber at one end and to the hollow hole at the other end.

[0007] In the utility model embodiment, the vice piston rod comprises: a vice rod body, the third oil hole is arranged in the vice rod body; a vice piston head is located in the second hydraulic cavity and is connected to one end of the vice rod body close to the second rodless cavity, the hollow hole penetrates through the vice rod body and the vice piston head, and the cross-sectional size of the vice piston head is greater than that of the vice rod body.

[0008] In the utility model embodiment, the hollow hole is located at the central axis of the vice piston rod, and the third oil hole is in plurality, and the plurality of third oil holes are arranged at the periphery of the hollow hole along the circumference of the vice piston rod.

[0009] In the utility model embodiment, the fourth oil hole is arranged in one end of the main piston rod close to the first rodless cavity, and the fourth oil hole is communicated with the first rod cavity and the second rod cavity.

[0010] In the utility model embodiment, the main piston rod comprises: a main rod body, the second hydraulic cavity and the fourth oil hole are arranged in the main rod body; a main piston head is connected to one end of the main rod body close to the first rodless cavity, and the cross-sectional size of the main piston head is greater than that of the main rod body.

[0011] In the utility model embodiment, the fourth oil hole is in plurality, and the plurality of fourth oil holes are arranged at the periphery of the vice piston rod along the circumference of the main rod body.

[0012] In the utility model embodiment, the hydraulic cylinder further comprises a first end cover and a second end cover arranged at both ends of the cylinder barrel along the axial direction of the cylinder barrel, the first end cover is arranged corresponding to the first rodless cavity, the second end cover is arranged corresponding to the first rod cavity, the vice piston rod is fixedly connected to the first end cover, and the main piston rod is movably penetrated through the second end cover.

[0013] In the utility model embodiment, the first end cover is provided with a mounting groove for mounting the vice piston rod, the main piston rod is provided with a plurality of annular protrusions with stepped cross sections, and the annular protrusions are used for extending into the mounting groove and surrounding the groove side wall of the mounting groove to form an oil groove communicated with the auxiliary oil channel.

[0014] The utility model further provides an engineering machinery, and the engineering machinery comprises the hydraulic cylinder.

[0015] Through the above technical scheme, the hydraulic cylinder provided by the utility model embodiment has the following beneficial effects:

[0016] When the main piston rod of the hydraulic cylinder needs to extend relative to the cylinder barrel, the high-pressure hydraulic oil of the oil tank can enter the first rodless cavity from the first oil hole, the hydraulic oil in the first rodless cavity can act on the end face of the main piston rod towards the first rodless cavity, and the main piston rod is pushed to extend relative to the cylinder barrel; the hydraulic oil in the first rodless cavity can also enter the second rodless cavity through the auxiliary oil channel, so that the hydraulic oil in the second rodless cavity acts on the end face of the main piston rod towards the second rodless cavity, and the hydraulic oil in the first rodless cavity and the hydraulic oil in the second rodless cavity jointly push the main piston rod to extend relative to the cylinder barrel; the action area of the hydraulic oil pushing the main piston rod can be larger than that of the cylinder in the prior art by the action area of the second rodless cavity, and the system pressure value is lower under the same load; when the main piston rod of the hydraulic cylinder needs to retract relative to the cylinder barrel, the high-pressure hydraulic oil can enter the first rod cavity from the second oil hole, the hydraulic oil in the first rod cavity can act on the end face of the main piston rod towards the first rod cavity, and the main piston rod is pushed to retract relative to the cylinder barrel; meanwhile, the hydraulic oil in the first rod cavity can enter the second rod cavity, the hydraulic oil in the second rod cavity can act on the end face of the main piston rod towards the second rod cavity, and the main piston rod is pushed to retract relative to the cylinder barrel; the action area of the hydraulic oil pushing the main piston rod can be larger than that of the cylinder in the prior art by the action area of the second rod cavity, the action area is larger under the same outer diameter of the hydraulic cylinder, and greater thrust can be provided to adapt to large load working conditions; and the hydraulic cylinder can be smaller, lighter and more convenient to install under the same load.

[0017] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with the following specific embodiments, but do not constitute a limitation on the present application. In the drawings:

[0019] Figure 1 is a hydraulic cylinder in the prior art;

[0020] Figure 2 is a sectional view of the hydraulic cylinder according to an embodiment of the present application;

[0021] Figure 3 is a sectional view of the hydraulic cylinder according to an embodiment of the present application.

[0022] BRIEF DESCRIPTION OF DRAWINGS

[0023] Label Name Label Name

[0024] 100 hydraulic cylinder 25 main piston head

[0025] 1 cylinder 251 annular protrusion

[0026] 11 first rodless chamber 3 auxiliary oil passage

[0027] 12 first rod chamber 31 auxiliary oil passage

[0028] 13 first oil hole 311 hollow hole

[0029] 14 second oil hole 312 third oil hole

[0030] 2 main piston rod 32 auxiliary rod body

[0031] 21 second rodless chamber 33 auxiliary piston head

[0032] 22 second rod chamber 4 first end cover

[0033] 23 fourth oil hole 41 installation groove

[0034] 24 main rod body 5 second end cover DETAILED DESCRIPTION

[0035] The specific embodiments described herein are intended to be illustrative only and are not intended to limit the scope of the present application. Other embodiments within the scope of the present application are apparent to those skilled in the art from consideration of the specification and may be practiced without departing from the spirit or essential character of the application.

[0036] A hydraulic cylinder according to the present application is described below with reference to the accompanying drawings.

[0037] As shown in Figure 2 and Figure 3 In the embodiment of the present application, the hydraulic cylinder 100 comprises a cylinder 1, a main piston rod 2 and an auxiliary piston rod 3. The cylinder 1 is provided with a first hydraulic chamber. The main piston rod 2 is arranged in the first hydraulic chamber and divides the first hydraulic chamber into a first rodless chamber 11 and a first rod chamber 12. The main piston rod 2 is provided with a second hydraulic chamber. The cylinder 1 is provided with a first oil hole 13 and a second oil hole 14. The first oil hole 13 connects the first rodless chamber 11 and an oil tank. The second oil hole 14 connects the first rod chamber 12 and the oil tank. The auxiliary piston rod 3 extends into the second hydraulic chamber from the first rodless chamber 11 and divides the second hydraulic chamber into a second rodless chamber 21 and a second rod chamber 22. The second rod chamber 22 is connected to the first rod chamber 12. The auxiliary piston rod 3 is provided with an auxiliary oil passage 31 connecting the first rodless chamber 11 and the second rodless chamber 21.

[0038] It can be understood that the second oil hole 14 is arranged corresponding to the first rod cavity 12, and the first oil hole 13 is arranged corresponding to the rodless cavity. In the embodiment, the main piston rod 2 is slidingly installed in the first hydraulic cavity of the cylinder barrel 1, and the auxiliary piston rod 3 is fixedly installed in the first hydraulic cavity of the cylinder barrel 1. In the case that the main piston rod 2 slides relative to the cylinder barrel 1, the auxiliary piston rod 3 is fixed relative to the cylinder barrel 1, and the main piston rod 2 moves relative to the auxiliary piston rod 3.

[0039] When the main piston rod 2 of the hydraulic oil cylinder 100 needs to extend relative to the cylinder barrel 1, high-pressure hydraulic oil can enter the first rodless cavity 11 from the first oil hole 13. The hydraulic oil in the first rodless cavity 11 can act on the end face of the main piston rod 2 facing the first rodless cavity 11, so as to push the main piston rod 2 to extend relative to the cylinder barrel 1. The hydraulic oil in the first rodless cavity 11 can also enter the second rodless cavity 21 through the auxiliary oil channel 31, so that the hydraulic oil in the second rodless cavity 21 acts on the end face of the main piston rod 2 facing the second rodless cavity 21. The hydraulic oil in the second rodless cavity 21 cooperates with the hydraulic oil in the first rodless cavity 11 to jointly push the main piston rod 2 to extend relative to the cylinder barrel 1. The action area of the hydraulic oil pushing the main piston rod 2 can be larger than that of the oil cylinder in the prior art by the action area of the second rodless cavity 21. Under the same load, the system pressure value is lower. When the main piston rod 2 of the hydraulic oil cylinder 100 needs to retract relative to the cylinder barrel 1, high-pressure hydraulic oil can enter the first rod cavity 12 from the second oil hole 14. The hydraulic oil in the first rod cavity 12 can act on the end face of the main piston rod 2 facing the first rod cavity 12, so as to push the main piston rod 2 to retract relative to the cylinder barrel 1. At the same time, the hydraulic oil in the first rod cavity 12 can enter the second rod cavity 22. The hydraulic oil in the second rod cavity 22 can act on the end face of the main piston rod 2 facing the second rod cavity 22, so as to push the main piston rod 2 to retract relative to the cylinder barrel 1. The action area of the hydraulic oil pushing the main piston rod 2 can be larger than that of the oil cylinder in the prior art by the action area of the second rod cavity 22. Under the same outer diameter of the oil cylinder, the action area is larger, which can provide larger thrust to adapt to large load working conditions. Under the same load, the hydraulic oil cylinder 100 can be made smaller, lighter and more convenient to install. In the embodiment, the first rodless cavity 11 of the hydraulic oil cylinder 100 is connected to the second rodless cavity 21 through the auxiliary oil channel 31 formed in the auxiliary piston rod 3. One rodless cavity and one rod cavity are added, the stress area is increased, and the pipeline does not need to be additionally increased. It is beautiful and convenient, and the internal cavity does not need to be directly connected with the outside, which can reduce pollution.

[0040] In an embodiment, the auxiliary oil passage 31 comprises a hollow hole 311 and a third oil hole 312, the hollow hole 311 penetrates the auxiliary piston rod 3 along the axial direction of the auxiliary piston rod 3 and communicates with the second rodless cavity 21, and the third oil hole 312 communicates with the first rodless cavity 11 at one end and communicates with the hollow hole 311 at the other end. The hollow hole 311 in the embodiment can be a long strip-shaped cylindrical hole, the length of the hollow hole 311 is consistent with the length of the auxiliary piston rod 3, and the third oil hole 312 is arranged at the end of the auxiliary piston rod 3 away from the first rod cavity 12. When the high-pressure hydraulic oil enters the first rodless cavity 11 through the first oil hole 13, the hydraulic oil in the first rodless cavity 11 can enter the hollow hole 311 through the third oil hole 312, and the hydraulic oil in the hollow hole 311 can enter the second rodless cavity 21. In the embodiment, the third oil hole 312 communicating with the first rodless cavity 11 is arranged at the end of the auxiliary piston rod 3, and a long strip-shaped hole penetrating the auxiliary piston rod 3 is arranged on the auxiliary piston rod 3, so that the connection structure of other oil cavities is avoided, the communication between the two rodless cavities is realized without external components, and the structure is simple and the cost is low.

[0041] Specifically, the auxiliary piston rod 3 comprises an auxiliary rod body 32 and an auxiliary piston head 33 located in the second hydraulic cavity, and the third oil hole 312 is arranged in the auxiliary rod body 32; the auxiliary piston head 33 is connected to the end of the auxiliary rod body 32 close to the second rodless cavity 21, the hollow hole 311 penetrates the auxiliary rod body 32 and the auxiliary piston head 33, and the cross-sectional size of the auxiliary piston head 33 is greater than that of the auxiliary rod body 32. In the embodiment, the auxiliary rod body 32 and the auxiliary piston head 33 can be fixedly connected by welding, the central axis of the auxiliary rod body 32 coincides with the central axis of the auxiliary piston head 33, the cross-sectional size of the auxiliary piston head 33 matches the cross-sectional size of the second hydraulic cavity, the main piston rod 2 and the auxiliary piston head 33 are in sliding contact and cooperation under the condition that the main piston rod 2 extends and retracts relative to the cylinder 1, and the auxiliary rod body 32 extends into the second hydraulic cavity from the first rodless cavity 11. The structure of the auxiliary piston rod 3 in the embodiment is simple and convenient to assemble.

[0042] It should be noted that the hollow hole 311 is located at the central axis of the auxiliary piston rod 3, and the number of the third oil holes 312 is multiple, and the multiple third oil holes 312 are arranged at the periphery of the hollow hole 311 along the circumferential direction of the auxiliary piston rod 3. As shown in Figure 2 , two third oil holes 312 surround the periphery of the hollow hole 311, and the hydraulic oil in the first rodless cavity 11 can enter the hollow hole 311 through the multiple third oil holes 312 at the same time, so as to ensure the hydraulic driving efficiency. In the embodiment, the central axis of the hollow hole 311 coincides with the central axis of the auxiliary piston rod 3, so as to ensure the structural strength of the auxiliary piston rod 3 and facilitate the layout of the multiple third oil holes 312.

[0043] As shown in Figure 2 and Figure 3As shown, the fourth oil hole 23 is arranged at one end of the main piston rod 2 close to the first rodless chamber 11, and the fourth oil hole 23 is communicated with the first rod chamber 12 and the second rod chamber 22. In this embodiment, the main piston rod 2 is hollow, and the fourth oil hole 23 is arranged on the cavity wall of the second hydraulic chamber. The high-pressure hydraulic oil entering the first rod chamber 12 through the second oil hole 14 can enter the second rod chamber 22 through the fourth oil hole 23. In this embodiment, the first rod chamber 12 and the second rod chamber 22 are communicated by the self-punching of the main piston rod 2, which can avoid the communication of the rod chambers by external components, and has a simple structure and is easy to assemble.

[0044] In this embodiment, the auxiliary oil channel 31 is arranged by punching the auxiliary oil channel 31 in the auxiliary piston rod 3, so that the first rodless chamber 11 and the second rodless chamber 21 are communicated in the interior of the hydraulic oil cylinder 100, without the need to additionally increase the pipeline, which is beautiful, convenient, has a large acting area when a large thrust is required, and has a low hydraulic oil pressure. At the same time, the first rod chamber 12 and the second rod chamber 22 are communicated through the fourth oil hole 23, so that the same pulling force can be ensured when the main piston rod 2 of the hydraulic oil cylinder 100 is retracted relative to the cylinder barrel 1, and the oil pressure is lower, which is energy-saving and environmentally friendly. In this embodiment, the internal cavity of the hydraulic oil cylinder 100 does not need to be directly connected with the outside, which can reduce pollution.

[0045] In an embodiment, the main piston rod 2 includes a main rod body 24 and a main piston head 25, and the second hydraulic chamber is arranged in the main rod body 24; the main piston head 25 is connected to one end of the main rod body 24 close to the first rodless chamber 11, the fourth oil hole 23 is arranged in the main rod body 24, and the cross-sectional size of the main piston head 25 is greater than the cross-sectional size of the main rod body 24. In this embodiment, the main piston head 25 is fixedly connected to the left end of the main rod body 24, the cross-sectional size of the main piston head 25 matches the cross-sectional size of the first hydraulic chamber, the main rod body 24 is hollow, and the auxiliary piston rod 3 penetrates through the main piston head 25 and extends into the second hydraulic chamber. In this embodiment, the fourth oil hole 23 is arranged close to the main piston head 25, which can ensure the supply of hydraulic oil between the first rod chamber 12 and the second rod chamber 22.

[0046] Specifically, the number of the fourth oil holes 23 is multiple, and the multiple fourth oil holes 23 are arranged at the periphery of the auxiliary piston rod 3 along the circumference of the main rod body 24. As shown, Figure 2 In this embodiment, the number of the fourth oil holes 23 is two, and the two fourth oil holes 23 are arranged at the periphery of the main rod body 24 and at the periphery of the auxiliary piston rod 3. The hydraulic oil in the first rod chamber 12 can supply oil to the second rod chamber 22 through the multiple fourth oil holes 23 at the same time, which ensures the hydraulic drive of the hydraulic oil cylinder 100. In other embodiments, the number of the fourth oil holes 23 can be arranged according to actual use requirements.

[0047] In an embodiment, the hydraulic cylinder 100 further comprises a first end cover 4 and a second end cover 5 arranged at both ends of the cylinder barrel 1 along the axial direction of the cylinder barrel 1, the first end cover 4 is arranged corresponding to the first rodless cavity 11, the second end cover 5 is arranged corresponding to the first rod cavity 12, the auxiliary piston rod 3 is fixedly connected to the first end cover 4, and the main piston rod 2 is movably penetrated through the second end cover 5. In the embodiment, the first end cover 4 is arranged at the left side of the cylinder barrel 1, the second end cover 5 is arranged at the right side of the cylinder barrel 1, the left side of the auxiliary piston rod 3 can be welded to the first end cover 4, and both ends of the cylinder barrel 1 are open in the embodiment, and the split structure is formed by arranging the cylinder barrel 1, the first end cover 4 and the second end cover 5, so that the main piston rod 2 and the auxiliary piston rod 3 can be conveniently assembled.

[0048] It should be noted that the first end cover 4 is provided with a mounting groove 41 for mounting the auxiliary piston rod 3, and the main piston rod 2 is provided with a plurality of annular protrusions 251 in a stepped cross-section, the annular protrusions 251 are used to extend into the mounting groove 41 and surround the groove side wall of the mounting groove 41 to form an oil groove connected with the auxiliary oil channel 31. Figure 2 And Figure 3 As shown in the drawings, in the embodiment, two annular protrusions 251 are arranged on the end face of the main piston rod 2 facing the first rodless cavity 11, the two annular protrusions 251 are nested from inside to outside along the radial direction of the main piston rod 2, the protrusion length of the annular protrusion 251 located inside is greater than the protrusion length of the annular protrusion 251 located outside, in the case that the main piston rod 2 moves to the leftmost side relative to the cylinder barrel 1, the two annular protrusions 251 can cooperate with the groove side wall of the mounting groove 41 to form an oil groove connected with the auxiliary oil channel 31, so as to ensure that the hydraulic oil in the first rodless cavity 11 can enter the second rodless cavity 21 through the third oil hole 312. Moreover, in the embodiment, the third oil hole 312 is arranged right relative to the groove side wall of the mounting groove 41 along the left-right direction.

[0049] The utility model discloses still propose a kind of engineering machinery, engineering machinery includes above-mentioned hydraulic cylinder 100, the specific structure of the hydraulic cylinder 100 refers to above-mentioned embodiment. Since engineering machinery adopts all technical solutions of above-mentioned all embodiments, it at least has all beneficial effects brought by the technical scheme of above-mentioned embodiment, which will not be repeated here. In an embodiment, the engineering machinery is a crane.

[0050] In the description of the utility model, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one feature. In the description of the utility model, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0051] In the utility model, unless another definite provision and limit, the term " install " " link " " connect " " fixed " and so on term should do broad sense understanding, for example, can be fixed connection, also can be detachable connection, or be integrated;Can be mechanical connection, also can be electric connection or each other can communicate;Can be direct link, also can pass through intermediate medium indirectly link, can be two element inside's intercommunication or two element's interaction relation, unless another definite limit.For the ordinary skill of the art, can understand the concrete meaning of above-mentioned term in the utility model according to specific circumstances.

[0052] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, the skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0053] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the ordinary skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A hydraulic cylinder, characterized in that, The hydraulic cylinder (100) includes: The cylinder (1) is provided with a first hydraulic chamber; The main piston rod (2) is disposed in the first hydraulic chamber and divides the first hydraulic chamber into a first rodless chamber (11) and a first rod chamber (12). A second hydraulic chamber is disposed in the main piston rod (2). A first oil hole (13) and a second oil hole (14) are provided on the cylinder (1). The first oil hole (13) connects the first rodless chamber (11) and the oil tank, and the second oil hole (14) connects the first rod chamber (12) and the oil tank. The auxiliary piston rod (3) extends from the first rodless chamber (11) into the second hydraulic chamber and divides the second hydraulic chamber into a second rodless chamber (21) and a second rod chamber (22). The second rod chamber (22) is connected to the first rod chamber (12). The auxiliary piston rod (3) is provided with an auxiliary oil passage (31) connecting the first rodless chamber (11) and the second rodless chamber (21).

2. The hydraulic cylinder according to claim 1, characterized in that, The auxiliary oil passage (31) includes: A hollow hole (311) extends through the auxiliary piston rod (3) along its axial direction and connects to the second rodless chamber (21); The third oil hole (312) is connected at one end to the first rodless cavity (11) and at the other end to the hollow hole (311).

3. The hydraulic cylinder according to claim 2, characterized in that, The auxiliary piston rod (3) includes: The third oil hole (312) is opened in the secondary rod body (32); The auxiliary piston head (33) is located in the second hydraulic chamber and connected to one end of the auxiliary rod body (32) near the second rodless chamber (21). The hollow hole (311) passes through the auxiliary rod body (32) and the auxiliary piston head (33). The cross-sectional dimension of the auxiliary piston head (33) is larger than that of the auxiliary rod body (32).

4. The hydraulic cylinder according to claim 2, characterized in that, The hollow hole (311) is located at the central axis of the auxiliary piston rod (3), and there are multiple third oil holes (312). The multiple third oil holes (312) are arranged at intervals around the hollow hole (311) along the circumference of the auxiliary piston rod (3).

5. The hydraulic cylinder according to any one of claims 1 to 4, characterized in that, The main piston rod (2) has a fourth oil hole (23) at one end near the first rodless chamber (11), and the fourth oil hole (23) connects the first rod chamber (12) and the second rod chamber (22).

6. The hydraulic cylinder according to claim 5, characterized in that, The main piston rod (2) includes: The main rod body (24), the second hydraulic chamber and the fourth oil hole (23) are both located on the main rod body (24); The main piston head (25) is connected to one end of the main rod body (24) near the first rodless cavity (11), and the cross-sectional dimension of the main piston head (25) is larger than the cross-sectional dimension of the main rod body (24).

7. The hydraulic cylinder according to claim 6, characterized in that, The number of the fourth oil holes (23) is multiple, and the multiple fourth oil holes (23) are arranged at intervals along the circumference of the main rod body (24) on the periphery of the auxiliary piston rod (3).

8. The hydraulic cylinder according to any one of claims 1 to 4, characterized in that, The hydraulic cylinder (100) further includes a first end cover (4) and a second end cover (5) that are disposed on both ends of the cylinder (1) along the axial direction of the cylinder (1). The first end cover (4) is disposed corresponding to the first rodless cavity (11), and the second end cover (5) is disposed corresponding to the first rod cavity (12). The auxiliary piston rod (3) is fixedly connected to the first end cover (4), and the main piston rod (2) is movably inserted through the second end cover (5).

9. The hydraulic cylinder according to claim 8, characterized in that, The first end cap (4) is provided with a mounting groove (41) for mounting the auxiliary piston rod (3). The main piston rod (2) is provided with a plurality of annular protrusions (251) with a stepped cross section. The annular protrusions (251) are used to extend into the mounting groove (41) and form an oil groove that communicates with the auxiliary oil passage (31) together with the groove sidewall of the mounting groove (41).

10. An engineering machinery, characterized in that, The engineering machinery includes the hydraulic cylinder (100) as described in any one of claims 1 to 9.

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