Hydraulic pump

Abstract

The utility model provides a hydraulic pump which comprises a shell, the shell is provided with a liquid inlet, a liquid outlet and a hydraulic cavity communicated with the liquid inlet and the liquid outlet, the shell is further provided with a pressure limiting channel, the pressure limiting channel and the hydraulic cavity are arranged in a spaced mode, the pressure limiting channel is provided with a first communication port and a second communication port which are arranged in a spaced mode, and the first communication port is communicated with the liquid outlet; the pressure limiting valve is movably arranged in the pressure limiting channel so as to block or avoid the second communication port; the blocking part is provided with a connecting end and a blocking end which are oppositely arranged, the connecting end is arranged at the end, close to the liquid outlet, of the first communication opening, the blocking end and the end, away from the liquid outlet, of the first communication opening are arranged in a spaced mode, and the blocking part and at least part of the pressure limiting channel are oppositely arranged. By means of the technical scheme, the technical problem that in the prior art, impurities in engine oil are prone to clamping a valve element of the pressure limiting valve can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulic pumps, in particular to a hydraulic pump. Background Art

[0002] At present, the oil pump is usually used to provide a certain flow of oil to the engine to lubricate the various parts in the engine. The oil pump is usually equipped with a pressure limiting valve. When the oil pressure is too high, the valve core needs to be opened to discharge the oil.

[0003] However, if Figure 3 The figure shows the internal structure of the oil pump in the prior art. There is an intersecting line transition area between the oil pump pressure limiting valve hole and the gear cavity hole. The oil pump pressure limiting valve has a low oil intake position. During the opening and closing process of the pressure limiting valve, impurities in the oil are easily retained in the transition area. When the pressure limiting valve is closed, the impurities will be squeezed in between the valve core and the valve hole, causing the valve core to get stuck, so that the pressure limiting valve remains in the open state, thereby making the engine lubricating oil channel pressure too low, unable to form effective lubrication, and further causing abnormal wear of internal engine components, affecting the engine life. Utility Model Content

[0004] The main purpose of the utility model is to provide a hydraulic pump to solve the technical problem in the prior art that impurities in the engine oil are easy to get stuck on the valve core of the pressure limiting valve.

[0005] In order to achieve the above object, the utility model provides a hydraulic pump, comprising:

[0006] A housing, wherein the housing has a liquid inlet, a liquid outlet, and a hydraulic cavity connected to the liquid inlet and the liquid outlet, and the housing further has a pressure-limiting channel, the pressure-limiting channel is spaced apart from the hydraulic cavity, the pressure-limiting channel has a first communication port and a second communication port spaced apart, and the first communication port is connected to the liquid outlet;

[0007] A pressure-limiting valve is movably disposed in the pressure-limiting channel to block or avoid the second communication port;

[0008] The blocking part has a connecting end and a blocking end which are arranged opposite to each other. The connecting end is arranged at one end of the first connecting port close to the liquid outlet, the blocking end is spaced apart from one end of the first connecting port away from the liquid outlet, and the blocking part is arranged opposite to at least part of the pressure limiting channel.

[0009] Furthermore, the blocking portion has a blocking side surface and a flow guiding side surface that are arranged opposite to each other, the blocking side surface and the flow guiding side surface are both located between the connecting end and the blocking end, and the flow guiding side surface is located on a side of the blocking side surface close to the pressure limiting channel;

[0010] Wherein, along the extending direction from the blocking end to the connecting end, the distance between the flow guiding side surface and the pressure limiting channel gradually decreases.

[0011] Furthermore, the flow-guiding side surface is a flow-guiding inclined surface or a flow-guiding curved surface.

[0012] Furthermore, the blocking portion has a blocking side surface and a flow guiding side surface that are arranged opposite to each other, the blocking side surface and the flow guiding side surface are both located between the connecting end and the blocking end, and the blocking side surface is located on a side of the flow guiding side surface close to the liquid outlet;

[0013] Wherein, the blocking side surface is arranged flush with the side wall surface used to enclose the liquid outlet; or,

[0014] The blocking side surface transitions smoothly with the side wall surface used for surrounding the liquid outlet.

[0015] Furthermore, along the extension direction from the connecting end to the blocking end, the length of the blocking portion is d, 3mm<d≤19mm.

[0016] Furthermore, the blocking portion has a blocking side surface and a guide side surface that are relatively arranged, and both the blocking side surface and the guide side surface are located between the connecting end and the blocking end. The guide side surface is located on the side of the blocking side surface close to the pressure limiting channel, and the guide side surface is a guide slope, and the inclination angle of the guide slope is α, 2°≤α≤9°.

[0017] Furthermore, the second communication port leads to the outside of the shell.

[0018] Furthermore, the shell also has a process channel, which is connected to the second connecting port and is separated from the hydraulic chamber; the shell also has a discharge port connected to the process channel, so that the liquid at the second connecting port can be discharged to the outside of the shell through the process channel and the discharge port.

[0019] Further, the pressure limiting valve comprises:

[0020] The valve core is movably arranged in the pressure-limiting channel, and one end of the valve core close to the first connecting port is provided with a first arc chamfer, and the radius of the first arc chamfer is R1, 0<R1≤0.3mm.

[0021] Furthermore, the valve core includes a first blocking portion, a connecting portion, and a second blocking portion which are connected in sequence, the first blocking portion and the second blocking portion are both adapted to the pressure limiting channel, the connecting portion and the pressure limiting channel are arranged at intervals, and an end of the first blocking portion away from the connecting portion forms one end of the valve core;

[0022] Wherein, a second arc chamfer is provided at one end of the first blocking portion close to the connecting portion, and the radius of the second arc chamfer is R2, 0<R2≤0.3mm;

[0023] A third arc chamfer is provided at one end of the second blocking portion close to the connecting portion, and the radius of the third arc chamfer is R3, 0<R3≤0.3mm.

[0024] By applying the technical solution of the utility model, a barrier can be formed between the pressure-limiting channel and the liquid outlet through the setting of the blocking part. When the hydraulic oil flows from the liquid outlet to the pressure-limiting valve in the pressure-limiting channel, it will first be blocked by the blocking part, and then flow to the pressure-limiting channel through the blocking end of the blocking part. In this way, the oil extraction position of the pressure-limiting valve is improved by the setting of the blocking part, and part of the impurities in the hydraulic oil can be blocked by the blocking part, thereby effectively reducing the possibility of impurities entering the pressure-limiting valve and causing the valve core of the pressure-limiting valve to be stuck. Therefore, the hydraulic pump provided by this embodiment can solve the technical problem in the prior art that impurities in the engine oil are easy to get stuck in the valve core of the pressure-limiting valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0026] Figure 1 A schematic structural diagram of a hydraulic pump provided according to an embodiment of the utility model is shown;

[0027] Figure 2 A schematic cross-sectional structure diagram of the AA section of the hydraulic pump provided according to an embodiment of the utility model is shown;

[0028] Figure 3 A schematic diagram of the cross-sectional structure of the AA section of a hydraulic pump in the prior art is shown;

[0029] Figure 4 A schematic cross-sectional structure diagram of the BB section of a hydraulic pump provided according to an embodiment of the utility model is shown;

[0030] Figure 5 A schematic diagram of the cross-sectional structure of the BB section of a hydraulic pump in the prior art is shown;

[0031] Figure 6 A schematic structural diagram of a pressure limiting valve provided according to an embodiment of the utility model is shown;

[0032] Figure 7 A schematic structural diagram of a valve core provided according to an embodiment of the utility model is shown.

[0033] The above drawings include the following reference numerals:

[0034] 10. Shell; 11. Liquid inlet; 12. Liquid outlet; 13. Hydraulic chamber; 14. Pressure limiting channel; 15. Process channel; 16. Discharge port;

[0035] 20. pressure limiting valve; 21. valve core; 211. first arc chamfer; 212. first blocking portion; 213. connecting portion; 214. second blocking portion; 215. second arc chamfer; 216. third arc chamfer;

[0036] 30. Blocking portion; 31. Blocking end; 32. Blocking side; 33. Diversion side. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] like Figure 1 , 2 , 4, 6 and 7, an embodiment of the utility model provides a hydraulic pump, which includes a housing 10, the housing 10 has a liquid inlet 11, a liquid outlet 12 and a hydraulic chamber 13 connected to both the liquid inlet 11 and the liquid outlet 12, the housing 10 also has a pressure-limiting channel 14, the pressure-limiting channel 14 is spaced apart from the hydraulic chamber 13, the pressure-limiting channel 14 has a first connecting port and a second connecting port spaced apart, and the first connecting port is connected to the liquid outlet 12. The hydraulic pump also includes a pressure-limiting valve 20, which can be movably arranged in the pressure-limiting channel 14 to block or avoid the second connecting port. The hydraulic pump also includes a blocking portion 30, the blocking portion 30 has a connecting end and a blocking end 31 that are arranged oppositely, the connecting end is arranged at one end of the first connecting port close to the liquid outlet 12, the blocking end 31 is spaced apart from one end of the first connecting port away from the liquid outlet 12, and the blocking portion 30 is arranged oppositely to at least part of the pressure-limiting channel 14.

[0039] The hydraulic pump provided in this embodiment can form a barrier between the pressure-limiting channel 14 and the liquid outlet 12 by setting the blocking part 30. When the hydraulic oil flows from the liquid outlet 12 to the pressure-limiting valve 20 in the pressure-limiting channel 14, it will first be blocked by the blocking part 30, and then flow to the pressure-limiting channel 14 through the blocking end of the blocking part 30. In this way, the oil-taking position of the pressure-limiting valve 20 is improved by setting the blocking part 30, and part of the impurities in the hydraulic oil can be blocked by the blocking part 30, thereby effectively reducing the possibility of impurities entering the pressure-limiting valve 20 and causing the valve core of the pressure-limiting valve 20 to be stuck. Therefore, the hydraulic pump provided in this embodiment can solve the technical problem in the prior art that impurities in the engine oil are easy to get stuck in the valve core of the pressure-limiting valve.

[0040] In addition, the above arrangement can also allow impurities in the engine oil to settle to a certain extent between the liquid outlet 12 and the blocking portion 30, thereby reducing the situation where impurities enter the valve core of the pressure limiting valve along with the oil.

[0041] Specifically, the blocking portion 30 has a blocking side surface 32 and a flow guiding side surface 33 that are arranged opposite to each other. The blocking side surface 32 and the flow guiding side surface 33 are both located between the connection end and the blocking end 31, and the flow guiding side surface 33 is located on the side of the blocking side surface 32 that is close to the pressure limiting channel 14. Along the extending direction from the blocking end 31 to the connection end, the distance between the flow guiding side surface 33 and the pressure limiting channel 14 gradually decreases. With such a structural arrangement, impurities in the hydraulic oil can be blocked by the blocking side surface 32, and at the same time, the hydraulic oil flowing to the pressure limiting valve 20 can be guided by the specific arrangement of the flow guiding side surface 33, which is beneficial for the pressure limiting valve 20 to take oil.

[0042] Specifically, the flow-guiding side surface 33 is a flow-guiding inclined surface or a flow-guiding cambered surface. In this way, the hydraulic oil flowing to the pressure-limiting valve 20 can be guided and drained by the specific arrangement of the flow-guiding side surface 33, which is beneficial for the pressure-limiting valve 20 to take oil.

[0043] In this embodiment, the blocking portion 30 has a blocking side surface 32 and a flow guiding side surface 33 that are arranged opposite to each other. The blocking side surface 32 and the flow guiding side surface 33 are both located between the connection end and the blocking end 31, and the blocking side surface 32 is located on the side of the flow guiding side surface 33 that is close to the liquid outlet 12. The blocking side surface 32 is arranged flush with the side wall surface that is used to surround the liquid outlet 12. With such a structural arrangement, the blocking side surface 32 can cooperate with the side wall surface of the liquid outlet 12 to jointly block the hydraulic oil, further improving the effect of blocking impurities from entering the pressure limiting valve 20, and also minimizing the situation where the flow velocity of the hydraulic fluid is greatly affected by the protrusion of the blocking side surface 32.

[0044] Specifically, the blocking side surface 32 smoothly transitions with the side wall surface surrounding the liquid outlet 12. With such a structural arrangement, the blocking side surface 32 and the side wall surface of the liquid outlet 12 can cooperate with each other to block the hydraulic oil, further improving the effect of blocking impurities from entering the pressure limiting valve 20.

[0045] Specifically, along the extension direction from the connection end to the blocking end 31, the length of the blocking portion 30 is d, 3mm<d≤19mm. With such a structural setting, the blocking portion 30 can have a certain length along the extension direction from the connection end to the blocking end 31, thereby ensuring the blocking effect on impurities in the hydraulic oil and avoiding the influence on the flow rate of the hydraulic oil.

[0046] In this embodiment, the length of the blocking portion 30 along the extending direction from the connecting end to the blocking end 31 matches the length of the pressure limiting valve 20 along the extending direction from the connecting end to the blocking end 31. With such a structural setting, the length of the blocking portion 30 along the extending direction from the connecting end to the blocking end 31 matches the height of the pressure limiting valve, thereby ensuring the blocking effect on impurities in the hydraulic oil and avoiding the influence on the flow rate of the hydraulic oil.

[0047] Specifically, the blocking portion 30 has a blocking side surface 32 and a flow guiding side surface 33 that are arranged opposite to each other. The blocking side surface 32 and the flow guiding side surface 33 are both located between the connecting end and the blocking end 31. The flow guiding side surface 33 is located on the side of the blocking side surface 32 close to the pressure limiting channel 14. The flow guiding side surface 33 is a flow guiding slope, and the inclination angle of the flow guiding slope is α, 2°≤α≤9°. With such a structural setting, the blocking effect of impurities in the hydraulic oil can be improved by setting the inclination angle of the flow guiding slope, while also avoiding the influence on the flow of the hydraulic oil.

[0048] Preferably, the inclination angle of the guide slope is α, and α=5°.

[0049] In this embodiment, the second communication port leads to the outside of the housing 10. Figure 5 As shown in the structure of the prior art in the prior art, the hydraulic oil discharged by the pressure limiting valve 20 in the prior art usually flows back into the hydraulic chamber 13 of the hydraulic pump through the oil passage, thereby increasing the possibility of impurities getting stuck. By directly discharging the hydraulic oil passing through the pressure limiting valve 20 into the hydraulic pump, it is possible to prevent impurities in the hydraulic oil from returning to the interior of the hydraulic pump and causing wear of parts.

[0050] Specifically, the housing 10 further has a process channel 15, which is connected to the second communication port, and the process channel 15 is separated from the hydraulic chamber 13; the housing 10 further has a discharge port 16 connected to the process channel 15, so that the liquid at the second communication port is discharged to the outside of the housing 10 through the process channel 15 and the discharge port 16. With such a structural arrangement, the hydraulic oil discharged from the pressure limiting channel 14 can be discharged from the housing 10 through the process channel 15.

[0051] In this embodiment, the pressure limiting valve 20 includes a valve core 21, which is movably arranged in the pressure limiting channel 14, and a first arc chamfer 211 is arranged at one end of the valve core 21 close to the first connecting port, and the radius of the first arc chamfer 211 is R1, 0<R1≤0.3mm. In this way, since the impurities that may cause the pressure limiting valve 20 to get stuck usually have a diameter of more than 0.3mm, and the chamfer of the valve core of the pressure limiting valve in the prior art is usually set to 1.5×20°, it is easy to cause the impurities to get stuck in the pressure limiting valve 20. The specific setting of the radius of the first arc chamfer 211 can ensure that the impurities will not get stuck in the pressure limiting valve 20 when flowing through the valve core 21, further reducing the possibility of hydraulic pump failure caused by the stuck pressure limiting valve 20.

[0052] Specifically, the valve core 21 includes a first blocking portion 212, a connecting portion 213 and a second blocking portion 214 connected in sequence. The first blocking portion 212 and the second blocking portion 214 are both adapted to the pressure limiting channel 14. The connecting portion 213 is spaced apart from the pressure limiting channel 14. The end of the first blocking portion 212 away from the connecting portion 213 forms one end of the valve core 21. The end of the first blocking portion 212 close to the connecting portion 213 is provided with a second arc chamfer 215, and the radius of the second arc chamfer 215 is R2, 0<R2≤0.3mm. The end of the second blocking portion 214 close to the connecting portion 213 is provided with a third arc chamfer 216, and the radius of the third arc chamfer 216 is R3, 0<R3≤0.3mm. In this way, since the impurities that may cause the pressure limiting valve 20 to get stuck usually have a diameter of more than 0.3 mm, the specific setting of the radius of the second arc chamfer 215 and the third arc chamfer 216 can ensure that the impurities will not get stuck in the pressure limiting valve 20 when flowing through the valve core 21, further reducing the possibility of hydraulic pump failure caused by the pressure limiting valve 20 getting stuck.

[0053] From the above description, it can be seen that the above-mentioned embodiments of the utility model achieve the following technical effects: adopting the back-to-oil extraction method of the pressure-limiting valve to reduce the probability of impurities entering the pressure-limiting valve, and the probability of impurities entering the pressure-limiting valve is reduced by 57%; optimizing the valve core structure, changing internal leakage to external leakage, which is conducive to the discharge of impurities.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0056] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0057] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0058] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0059] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A hydraulic pump, characterized in that: include: A housing (10), the housing (10) comprising a liquid inlet (11), a liquid outlet (12), and a hydraulic chamber (13) in communication with the liquid inlet (11) and the liquid outlet (12); the housing (10) further comprising a pressure limiting channel (14), the pressure limiting channel (14) being spaced apart from the hydraulic chamber (13); the pressure limiting channel (14) comprising a first communication port and a second communication port spaced apart from each other, the first communication port being in communication with the liquid outlet (12); a pressure limiting valve (20) movably arranged in the pressure limiting channel (14) to block or avoid the second communication port; A blocking portion (30), the blocking portion (30) comprising a connecting end and a blocking end (31) arranged opposite to each other, the connecting end being arranged at an end of the first connecting port close to the liquid outlet (12), the blocking end (31) being arranged at a distance from an end of the first connecting port far from the liquid outlet (12), and the blocking portion (30) being arranged opposite to at least a portion of the pressure limiting channel (14).

2. The hydraulic pump according to claim 1, characterized in that: The blocking portion (30) comprises a blocking side surface (32) and a flow guiding side surface (33) which are arranged opposite to each other, the blocking side surface (32) and the flow guiding side surface (33) are both located between the connecting end and the blocking end (31), and the flow guiding side surface (33) is located on a side of the blocking side surface (32) close to the pressure limiting channel (14); Wherein, along the extending direction from the blocking end (31) to the connecting end, the distance between the flow guiding side surface (33) and the pressure limiting channel (14) gradually decreases.

3. The hydraulic pump according to claim 2, characterized in that: The flow-guiding side surface (33) is a flow-guiding inclined surface or a flow-guiding arc surface.

4. The hydraulic pump according to claim 1, characterized in that: The blocking portion (30) comprises a blocking side surface (32) and a flow guiding side surface (33) which are arranged opposite to each other, the blocking side surface (32) and the flow guiding side surface (33) are both located between the connecting end and the blocking end (31), and the blocking side surface (32) is located on a side of the flow guiding side surface (33) close to the liquid outlet (12); Wherein, the blocking side surface (32) is arranged flush with the side wall surface used to surround the liquid outlet (12); or, The blocking side surface (32) smoothly transitions to the side wall surface used to surround the liquid outlet (12).

5. The hydraulic pump according to claim 1, characterized in that: Along the extension direction from the connecting end to the blocking end (31), the length of the blocking portion (30) is d, 3mm<d≤19mm.

6. The hydraulic pump according to claim 1, characterized in that: The blocking portion (30) comprises a blocking side surface (32) and a flow guiding side surface (33) which are arranged opposite to each other; the blocking side surface (32) and the flow guiding side surface (33) are both located between the connecting end and the blocking end (31); the flow guiding side surface (33) is located on a side of the blocking side surface (32) close to the pressure limiting channel (14); the flow guiding side surface (33) is a flow guiding inclined surface; and the inclination angle of the flow guiding inclined surface is α, 2°≤α≤9°.

7. The hydraulic pump according to claim 1, characterized in that: The second communication port leads to the outside of the shell (10).

8. The hydraulic pump according to claim 1, characterized in that: The housing (10) further comprises a process channel (15), the process channel (15) being in communication with the second communication port, and the process channel (15) being separated from the hydraulic chamber (13); the housing (10) further comprises a discharge port (16) in communication with the process channel (15), so that liquid at the second communication port is discharged to the outside of the housing (10) through the process channel (15) and the discharge port (16).

9. The hydraulic pump according to claim 1, characterized in that: The pressure limiting valve (20) comprises: A valve core (21), the valve core (21) being movably arranged in the pressure limiting channel (14), and a first circular arc chamfer (211) being arranged at one end of the valve core (21) close to the first connecting port, the radius of the first circular arc chamfer (211) being R1, 0<R1≤0.3mm.

10. The hydraulic pump according to claim 9, characterized in that The valve core (21) comprises a first blocking portion (212), a connecting portion (213) and a second blocking portion (214) which are connected in sequence, the first blocking portion (212) and the second blocking portion (214) are both adapted to the pressure limiting channel (14), the connecting portion (213) and the pressure limiting channel (14) are arranged at intervals, and an end of the first blocking portion (212) away from the connecting portion (213) forms one end of the valve core (21); Wherein, a second arc chamfer (215) is provided at one end of the first blocking portion (212) close to the connecting portion (213), and the radius of the second arc chamfer (215) is R2, 0<R2≤0.3mm; A third circular chamfer (216) is provided at one end of the second blocking portion (214) close to the connecting portion (213), and the radius of the third circular chamfer (216) is R3, 0<R3≤0.3mm.

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