DC high-pressure piston pump and coffee machine

Abstract

The present invention provides a DC high-pressure piston pump and a coffee machine. The DC high-pressure piston pump includes a cylinder block, a drive assembly, a cam assembly, and a piston assembly. An accommodation cavity and a pressurization cavity that communicate with each other are provided in the cylinder block, and a piston channel is provided on one side of the pressurization cavity close to the accommodation cavity. The first end of the piston assembly is connected to the cam assembly, and the second end is in clearance fit with the piston channel. The piston assembly is provided with a cam moving cavity and a sliding fit portion, and a limiting portion is provided on the cylinder block and / or the drive assembly. The sliding fit portion is in limiting fit with the limiting portion and slides along a first direction relative to the limiting portion; the cam assembly is located in the cam moving cavity, and the cam assembly includes a cam body and a rotating shaft. The cam body is fixed on the drive shaft, the rotating shaft is rotatably installed on the cam body, and the outer peripheral wall of the rotating shaft contacts the inner peripheral wall of the cam moving cavity; the drive assembly drives the cam assembly to rotate and drives the piston assembly to reciprocate. The DC high-pressure piston pump enables the inside of the cylinder block to reach a higher pressure and reduces the operating resistance.

Description

Technical Field

[0001] The present invention relates to the field of coffee making equipment, and specifically, to a DC high-pressure plunger pump and a coffee machine. Background Art

[0002] Refer to Figures 1 to 3 , the water pump used in the existing coffee machine includes a connecting rod 101, a piston 102, a cam 103, a cylinder block 104 and a motor. The piston 102 is reciprocally movably installed in the cylinder block 104. The cam 103 is installed on the drive shaft 105 of the motor. Two ends of the connecting rod 101 are respectively hinged to the piston 102 and the cam 103. The motor drives the cam 103 to rotate and drives the connecting rod 101 to swing. The connecting rod 101 drives the piston 102 to reciprocally move, thereby realizing the pressurization in the cylinder block 104.

[0003] In the process that the connecting rod 101 drives the piston 102 to move in this water pump, since the connecting rod 101 swings relative to the piston 102, the sealing performance between the piston 102 and the cylinder block 104 may be poor. And since the connecting rod 101 not only has reciprocating movement but also has swinging, it is impossible to make the pressure inside the cylinder block higher and the running resistance is large. Summary of the Invention

[0004] The first object of the present invention is to provide a DC high-pressure plunger pump that can make the pressure inside the cylinder block higher and at the same time reduce the running resistance.

[0005] The second object of the present invention is to provide a coffee machine having the above-mentioned DC high-pressure plunger pump.

[0006] To achieve the above first object, the present invention provides a DC high-pressure plunger pump, including a cylinder block, a drive assembly, a cam assembly and a piston assembly. An accommodation cavity and a pressurization cavity that communicate with each other are provided in the cylinder block. A piston channel extending along a first direction is provided on a side of the pressurization cavity close to the accommodation cavity. The drive assembly is arranged on one side of the cylinder block. The drive shaft of the drive assembly extends into the accommodation cavity, and the axial direction of the drive shaft is perpendicular to the first direction. The cam assembly is installed on the drive shaft and is located in the accommodation cavity. The piston assembly is installed in the accommodation cavity. The first end of the piston assembly is connected to the cam assembly, and the second end of the piston assembly extends into the piston channel. The piston assembly is in clearance fit with the piston channel. The piston assembly is provided with a cam moving cavity and a sliding fit portion. A limiting portion is provided on the cylinder block and / or the drive assembly. The sliding fit portion is in limiting fit with the limiting portion and slides along the first direction relative to the limiting portion. The cam assembly is located in the cam moving cavity. The cam assembly includes a cam body and a rotating shaft. The cam body is fixed on the drive shaft. The rotating shaft is rotatably installed on the cam body. The axis of the rotating shaft is parallel to the axial direction of the drive shaft. The outer peripheral wall of the rotating shaft contacts the inner peripheral wall of the cam moving cavity. The drive assembly drives the cam assembly to rotate and drives the piston assembly to reciprocally move along the first direction.

[0007] As can be seen from the above solution, when the driving component drives the cam component to rotate, the rotating shaft of the cam component applies a force to the piston component. At the same time, due to the cooperation between the sliding fit portion on the piston component and the limiting portion on the cylinder block / driving component, the piston component can only reciprocate along the first direction. Since the piston only moves along the first direction relative to the cylinder block and does not swing relative to the cylinder block, the sealing performance between the piston and the piston passage can be effectively guaranteed, so that a higher pressure can be achieved in the pressurizing chamber inside the cylinder block. At the same time, since the piston does not swing relative to the cylinder block, the resistance of the piston during movement is smaller. In addition, the rotating shaft is rotatably mounted on the cam body, so the friction force between the rotating shaft and the piston is rolling friction. Since the cam continuously generates friction with the inner peripheral wall of the cam moving cavity during rotation, through the setting of the rotating shaft, the friction force between the cam component and the piston can be reduced, preventing the piston from not being able to move to the preset position due to the wear of the cam component and failing to achieve the effect of effective pressurization, and it can effectively extend the service life of the DC high-pressure piston pump.

[0008] A preferred solution is that an installation groove with an opening facing away from the driving shaft direction is formed on the peripheral wall of the cam body, and a central hole is axially penetrated through the rotating shaft; the cam component further includes a positioning pin, the positioning pin is fixed on the cam body and passes through the installation groove, the rotating shaft is sleeved on the positioning pin through the central hole, the rotating shaft is located in the installation groove, and a part of the rotating shaft exposes from the opening.

[0009] Thus, the rotating shaft can be stably connected to the cam body.

[0010] A preferred solution is that the cam moving cavity includes a first arc-shaped wall and a second arc-shaped wall that are oppositely arranged and connected end to end. The first arc-shaped wall bends towards the pressurizing chamber, the second arc-shaped wall bends towards the direction away from the pressurizing chamber, and the plane where the central axis of the first arc-shaped wall and the central axis of the second arc-shaped wall are located passes through the axis of the driving shaft and is parallel to the first direction.

[0011] Thus, the rotating shaft can move along the first arc-shaped wall and the second arc-shaped wall, so as to ensure the smooth movement of the piston component.

[0012] A preferred solution is that the piston component includes a piston, a seal, an elastic sealing ring and a fixing member; the piston includes a cylindrical portion and a piston portion that are arranged and connected along the first direction, the cam moving cavity and the sliding fit portion are both located on the cylindrical portion, and the piston portion is in sliding fit with the piston passage; the seal and the elastic sealing ring are both arranged at the axial end of the piston portion away from the cylindrical portion, the elastic sealing ring is located between the seal and the piston portion, and the fixing member fixes the seal on the piston portion along the first direction.

[0013] It can be seen that through the settings of the seal and the elastic sealing ring, the effective isolation between the pressurizing chamber and the accommodating chamber is ensured, preventing the liquid in the pressurizing chamber from flowing into the accommodating chamber. The seal realizes the sealing in the axial and radial directions of the piston channel, and the elastic sealing ring further seals the gap between the piston and the seal, preventing the liquid from entering the accommodating chamber through the central hole of the seal.

[0014] A further solution is the interference fit between the seal and the piston channel; or a sleeve is provided in the piston channel, and the seal is in interference fit with the sleeve.

[0015] A further solution is that the seal is made of Teflon material, fluororubber, special plastic or precision special ceramic, and the sleeve is made of metal material or ceramic material.

[0016] It can be seen that through the interference fit between the seal made of materials such as Teflon and the inner peripheral wall of the piston channel or the sleeve in the piston channel, on the one hand, the sealing performance of the piston and the piston channel in the radial and axial directions is ensured, and on the other hand, materials such as Teflon have an extremely low lubrication coefficient and good wear resistance. Therefore, even after the piston makes multiple reciprocating movements, the seal still will not fail, and it ensures the smooth sliding of the piston in the piston channel. The sleeve made of metal material or ceramic material can improve the fitting accuracy with the piston part and at the same time improve the wear resistance.

[0017] A further solution is that the piston assembly further includes an elastic sealing ring and a pressing block; the pressing block is arranged on the side opposite to the elastic sealing ring of the seal, and the fixing part sequentially passes through the pressing block and the seal and is fixedly connected to the piston; the elastic sealing ring is squeezed and installed between the outer peripheral wall of the pressing block and the inner peripheral wall of the piston channel.

[0018] It can be seen that the setting of the pressing block ensures the stability of the seal installed on the piston, preventing the seal from being deformed or falling off under force. And the setting of the elastic sealing ring ensures the sealing performance in the axial and radial directions between the pressing block and the piston channel.

[0019] A preferred solution is that a shaft hole is provided on the top wall of the cylinder block; the free end of the drive shaft is rotatably installed in the shaft hole; or a shaft sleeve is provided in the shaft hole, and the free end of the drive shaft is rotatably installed in the shaft sleeve; or a bearing is provided in the shaft hole, and the free end of the drive shaft is rotatably installed in the bearing.

[0020] It can be seen that the setting of the shaft hole realizes the support for the free end of the drive shaft, preventing the drive shaft from shaking during the working process. And by providing a shaft sleeve or a bearing in the shaft hole, the wear resistance of the shaft hole can be improved, preventing the shaft hole from being worn and enlarged, so that the effective support for the free end of the drive shaft cannot be achieved. At the same time, through the setting of the shaft sleeve or the bearing, the smoothness and smoothness of the rotation of the drive shaft are ensured.

[0021] Preferably, the limiting part includes two parallel limiting walls located in the accommodating cavity, and the sliding fitting part includes two parallel sliding fitting walls located on the outer peripheral wall of the piston assembly; the sliding fitting walls cooperate with the limiting walls to limit the piston to slide only in the first direction.

[0022] It can be seen that the limiting cooperation between the sliding fitting wall and the limiting wall ensures that the piston can only slide in the first direction.

[0023] To achieve the above second object, the present invention provides a coffee machine including the above-mentioned DC high-pressure piston pump. Description of the Drawings

[0024] Figure 1 is a schematic structural diagram of a conventional water pump piston of a coffee machine in the first position during movement.

[0025] Figure 2 is a schematic structural diagram of a conventional water pump piston of a coffee machine when it moves to the second position.

[0026] Figure 3 is a schematic structural diagram of a conventional water pump piston of a coffee machine when it moves to the third position.

[0027] Figure 4 is a cross-sectional view of an embodiment of the DC high-pressure piston pump of the present invention.

[0028] Figure 5 is an assembly drawing of the drive shaft, cam assembly, cylinder block and piston assembly in an embodiment of the DC high-pressure piston pump of the present invention.

[0029] Figure 6 is an exploded view of the drive shaft, cam assembly, cylinder block and piston assembly in an embodiment of the DC high-pressure piston pump of the present invention.

[0030] Figure 7 is a cross-sectional view of an embodiment of the DC high-pressure piston pump of the present invention perpendicular to the axial direction of the drive shaft.

[0031] Figure 8 is a cross-sectional view of the drive shaft, cam assembly, cylinder block and piston assembly in an embodiment of the DC high-pressure piston pump of the present invention.

[0032] Figure 9 is a schematic structural diagram of the piston assembly in an embodiment of the DC high-pressure piston pump of the present invention in the first position during movement.

[0033] Figure 10 is a schematic structural diagram of the piston assembly in an embodiment of the DC high-pressure piston pump of the present invention when it moves to the second position.

[0034] Figure 11This is a schematic structural diagram when the piston assembly in the DC high-pressure piston pump embodiment of the present invention moves to the third position.

[0035] The present invention will be further described below in conjunction with the drawings and embodiments. Specific embodiments

[0036] See Figure 4 , the coffee machine of this embodiment includes a DC high-pressure piston pump 100, and the DC high-pressure piston pump 100 includes a cylinder block 1, a drive assembly 2, a cam assembly 3, and a piston assembly 4.

[0037] An accommodating cavity 11 and a pressurizing cavity 12 that communicate with each other are provided in the cylinder block 1. A piston passage 13 extending along a first direction is provided on one side of the pressurizing cavity 12 close to the accommodating cavity 11. The drive assembly 2 is arranged on one side of the cylinder block 1. The drive assembly 2 includes a motor 22, a planetary gear reduction gear set 23, and a drive shaft 21. The drive shaft 21 and the rotating shaft 221 of the motor 22 are both connected to the planetary gear reduction gear set 23, so as to transmit the driving force of the motor 22 to the drive shaft 21. The drive shaft 21 extends upward into the accommodating cavity 11, and the axial direction of the drive shaft 21 is perpendicular to the first direction. An inlet 121 and an outlet 122 that are opposite to each other in the axial direction of the drive shaft 21 are provided on the cylinder block 1. The inlet 121 and the outlet 122 are both communicated with the pressurizing cavity 12 and are respectively located on opposite sides of the pressurizing cavity 12. An inlet valve 123 is provided in the inlet 121, and an outlet valve 124 is provided in the outlet 122. Both the inlet valve 123 and the outlet valve 124 include a spring 1231 and a sealing plug 1232. The spring 1231 is arranged on the side of the corresponding sealing plug 1232 close to the pressurizing cavity 12. The restoring force of the spring 1231 of the inlet valve 123 forces the sealing plug 1232 to seal the corresponding inlet 121, and the restoring force of the spring 1231 of the outlet valve 124 forces the sealing plug 1232 to seal the corresponding outlet 122.

[0038] See Figures 4 to 8 , a top cover 15 is provided on the top of the cylinder block 1. A shaft hole 151 is opened on the top cover 15, and a bearing 152 is provided in the shaft hole 151. The free end of the drive shaft 21 is rotatably installed in the bearing 152. Preferably, the bearing 152 is an oil-impregnated bearing. A sliding groove 414 extending along the first direction is opened on the top wall of the cylindrical portion 411 of the piston 41. The drive shaft 21 passes through the sliding groove 414 and is connected to the bearing 152. The length of the sliding groove 414 is greater than or equal to the displacement of the piston 41 in the first direction.

[0039] The piston assembly 4 is installed in the accommodation cavity 11. The piston assembly 4 includes a piston 41, a seal 42, an elastic sealing ring 43, a fixing member, an elastic sealing ring 45 and a pressing block 46. The fixing member is a fastening screw 44. The piston 41 includes a cylindrical portion 411 and a piston portion 412 that are arranged and connected along a first direction. A cam moving cavity 413 is provided on the cylindrical portion 411. The cam assembly 3 is installed on the drive shaft 21 and is located in the cam moving cavity 413. The cross-sectional area of the cam moving cavity 413 is larger than the cross-sectional area of the cam assembly 3. The cylindrical portion 411 of the piston assembly 4 is located in the accommodation cavity 11 and is cooperatively connected with the cam assembly 3. The piston portion 412 of the piston assembly 4 extends into the piston passage 13. A sleeve 14 is provided in the piston passage 13. The sleeve 14 is made of a metal material. The sleeve 14 is integrally injection-molded with the piston portion 412. The piston portion 412 is in clearance fit with the inner peripheral wall of the sleeve 14 and can reciprocate along the extending direction of the piston passage 13.

[0040] As Figure 7 and Figure 8 shown, the cam moving cavity 413 includes a first arc wall 4131 and a second arc wall 4132 that are oppositely arranged and connected end to end. The first arc wall 4131 bends towards the pressurizing cavity 12, and the second arc wall 4132 bends towards the direction away from the pressurizing cavity 12. The plane where the central axis of the first arc wall 4131 and the central axis of the second arc wall 4132 are located passes through the axis of the drive shaft 21 and is parallel to the first direction.

[0041] Both the seal 42 and the elastic sealing ring 43 are provided at the axial end of the piston portion 412 away from the cylindrical portion 411. The elastic sealing ring 43 is located between the seal 42 and the piston portion 412. The seal 42 is in the shape of a disc-shaped ring and is made of Teflon material. The seal 42 is in interference fit with the sleeve 14. The pressing block 46 is provided on the side of the seal 42 opposite to the elastic sealing ring 43. A threaded hole 4121 is provided at the axial end of the piston portion 412 away from the cylindrical portion 411, and the threaded hole 4121 is a blind hole, so as to prevent liquid from entering the accommodation cavity 11 through the gap between the threaded hole 4121 and the fastening screw 44, further improving the sealing performance. The fastening screw 44 sequentially passes through the pressing block 46 and the seal 42 along the first direction and is fixedly connected to the threaded hole 4121 of the piston portion 412, thereby fixing the seal 42 on the piston portion 412. The elastic sealing ring 45 is press-fitted and installed between the outer peripheral wall of the pressing block 46 and the inner peripheral wall of the sleeve 14.

[0042] See Figure 4 as well as Figures 6 to 8, the cam assembly 3 includes a cam body 31, a rotating shaft 32 and a positioning pin 33. The cam body 31 is fixed on the drive shaft 21. The rotating shaft 32 is rotatably installed on the cam body 31. The axis of the rotating shaft 32 is parallel to the axial direction of the drive shaft 21. An installation groove 311 with an opening 312 facing away from the drive shaft 21 is formed on the circumferential wall of the cam body 31. A central hole 321 is axially formed through the rotating shaft 32. The rotating shaft 32 is located in the installation groove 311, and a part of the rotating shaft 32 is exposed from the opening 312. The positioning pin 33 axially passes through the cam body 31 and the central hole 321 of the rotating shaft 32, thereby connecting the rotating shaft 32 to the cam body 31. By sleeving the rotating shaft 32 on the positioning pin 33, the rotating shaft 32 can freely rotate around the central axis of the positioning pin 33, and the outer peripheral wall of the rotating shaft 32 contacts the inner peripheral wall of the cam cavity 413. On the one hand, it reduces the frictional force between the cam assembly 3 and the piston assembly 4, and on the other hand, it provides a driving force for driving the piston assembly 4 to move.

[0043] As Figure 7 shown, a limiting portion is provided on the cylinder block 1. The limiting portion includes a limiting wall 111 and a limiting wall 112 that are parallel and both extend along the first direction. The limiting wall 111 and the limiting wall 112 are both located in the accommodating cavity 11. The piston assembly 4 is provided with a sliding fit portion. The sliding fit portion includes a sliding fit wall 415 and a sliding fit wall 416 that are parallel and both extend along the first direction. The sliding fit wall 415 and the sliding fit wall 416 are located on the outer peripheral wall of the cylindrical portion 411 of the piston 41. The cylindrical portion 411 is located between the limiting wall 111 and the limiting wall 112. The sliding fit wall 415 contacts the limiting wall 111, and the sliding fit wall 416 contacts the limiting wall 112, so that the sliding fit wall and the limiting wall cooperate to limit the piston 41 to slide only along the first direction. In this embodiment, the diameter of the drive shaft 21 at the sliding groove 414 is substantially the same as the width of the sliding groove 414 of the piston 41, that is, the drive shaft 21 and the sliding groove 414 are in clearance fit. Therefore, the portion of the drive shaft 21 that cooperates with the sliding groove 414 is also a limiting portion, and the sliding groove 414 on the piston 41 is a sliding fit portion. The limiting fit formed by the two makes the piston 41 slide only along the first direction.

[0044] Refer to Figures 9 to 11 , when the drive shaft 21 of the drive assembly 2 drives the cam assembly 3 to rotate, the rotating shaft 32 of the cam assembly 3 applies a force to the inner peripheral wall of the cam cavity 413 of the piston 41. At the same time, due to the cooperation between the sliding fit portion on the piston assembly 4 and the limiting portion on the cylinder block 1, the piston assembly 4 can only reciprocate along the first direction and does not swing relative to the piston passage 13.

[0045] As can be seen from the above, since the piston moves only in the first direction relative to the cylinder block and does not swing relative to the cylinder block, the sealing performance between the piston and the piston passage can be effectively guaranteed, so that a higher pressure can be achieved in the pressurization chamber inside the cylinder block. At the same time, since the piston does not swing relative to the cylinder block, the resistance of the piston during movement is smaller. In addition, the rotating shaft is rotatably installed on the cam body, so the friction between the rotating shaft and the piston is rolling friction. Since the cam continuously generates friction with the inner peripheral wall of the cam moving chamber during rotation, through the setting of the rotating shaft, the friction between the cam assembly and the piston can be reduced, preventing the piston from not being able to move to the preset position due to the wear of the cam assembly and unable to achieve the effective pressurization effect, and it can effectively extend the service life of the DC high-pressure piston pump.

[0046] In addition, the rotating shaft can also be a solid structure, and hinge shafts are provided at both ends of the rotating shaft. The rotating shaft is hinged to the cam body through the hinge shafts. Bearings can also be used to replace the rotating shaft. The number of rotating shafts can also be more than two, and multiple said rotating shafts are arranged in parallel or coaxially. The free end of the driving shaft of the motor can also be directly connected to the shaft hole on the top cover of the cylinder block, or a shaft sleeve can also be provided in the shaft hole, and the driving shaft is in fit connection with the shaft sleeve. A sleeve may not be provided in the piston passage, and the piston portion is in clearance fit with the inner peripheral wall of the piston passage, and the seal is in interference fit with the inner peripheral wall of the piston passage. The seal can also be made of other wear-resistant materials. The piston assembly can also include one of a seal and an elastic sealing ring to achieve axial sealing and radial sealing. A shaft sleeve can also be provided in the shaft hole of the top cover of the cylinder block, and the free end of the driving shaft is rotatably installed in the shaft sleeve; or no shaft sleeve or bearing is provided in the shaft hole, but the free end of the driving shaft is directly assembled in the shaft hole. The width of the chute can also be greater than the diameter of the driving shaft, and the piston can be restricted to slide only in the first direction only through the cooperation of the sliding fit wall and the limiting wall. The seal can also be made of materials such as fluororubber, special plastics, or precision special ceramics. The sleeve can also be made of ceramic materials. The above changes can also achieve the purpose of the present invention.

[0047] Finally, it should be emphasized that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. DC high-pressure piston pump, comprising: A cylinder block, in which an accommodating cavity and a pressurizing cavity are provided and communicated with each other. A piston channel extending along a first direction is provided on a side of the pressurizing cavity close to the accommodating cavity; A driving assembly, which is arranged on one side of the cylinder block. A driving shaft of the driving assembly extends into the accommodating cavity, and an axial direction of the driving shaft is perpendicular to the first direction; A cam assembly, which is mounted on the driving shaft and located in the accommodating cavity; A piston assembly, which is mounted in the accommodating cavity. A first end of the piston assembly is connected to the cam assembly, a second end of the piston assembly extends into the piston channel, and the piston assembly is in clearance fit with the piston channel; It is characterized in that: The piston assembly is provided with a cam moving cavity and a sliding fit portion. A limiting portion is provided on the cylinder block and / or the driving assembly. The sliding fit portion is in limiting fit with the limiting portion and slides along the first direction relative to the limiting portion; The cam assembly is located in the cam moving cavity. The cam assembly includes a cam body and a rotating shaft. The cam body is fixed on the driving shaft, the rotating shaft is rotatably mounted on the cam body, an axis of the rotating shaft is parallel to an axial direction of the driving shaft, and an outer peripheral wall of the rotating shaft contacts an inner peripheral wall of the cam moving cavity; The driving assembly drives the cam assembly to rotate and drives the piston assembly to reciprocate along the first direction; An installation groove with an opening facing away from the driving shaft is formed on a peripheral wall of the cam body. The rotating shaft is located in the installation groove, and a part of the rotating shaft exposes from the opening; The cam moving cavity includes a first arc wall and a second arc wall which are oppositely arranged and connected end to end. The first arc wall bends towards the pressurizing cavity, the second arc wall bends towards a direction away from the pressurizing cavity, and a plane where a central axis of the first arc wall and a central axis of the second arc wall are located passes through an axis of the driving shaft and is parallel to the first direction; The piston assembly includes a piston, a seal, an elastic sealing ring and a fixing member; The piston includes a cylindrical portion and a piston portion which are arranged and connected along the first direction. The cam moving cavity and the sliding fit portion are both located on the cylindrical portion, and the piston portion is in sliding fit with the piston channel; The seal and the elastic sealing ring are both arranged at an axial end of the piston portion far from the cylindrical portion. The elastic sealing ring is located between the seal and the piston portion, and the fixing member fixes the seal on the piston portion along the first direction.

2. The DC high-pressure piston pump according to claim 1, characterized in that: A central hole is axially penetrated through the rotating shaft; The cam assembly further includes a positioning pin, which is fixed on the cam body and passes through the installation groove, and the rotating shaft is sleeved on the positioning pin through the central hole.

3. The DC high-pressure piston pump according to claim 1, characterized in that: The seal is in interference fit with the piston channel; or A sleeve is arranged in the piston passage, and the seal is in interference fit with the sleeve.

4. The DC high-pressure plunger pump according to claim 3, wherein: The seal is made of Teflon material or fluororubber, and the sleeve is made of metal material or ceramic material.

5. The DC high-pressure plunger pump according to any one of claims 1 to 4, wherein: The piston assembly further includes an elastic sealing ring and a pressing block; The pressing block is arranged on the side opposite to the elastic sealing ring of the seal, and the fixing member sequentially passes through the pressing block and the seal and then is fixedly connected to the piston; The elastic sealing ring is squeezed and installed between the outer peripheral wall of the pressing block and the inner peripheral wall of the piston passage.

6. The DC high-pressure plunger pump according to any one of claims 1 to 4, wherein: A shaft hole is provided in the top wall of the cylinder block; The free end of the drive shaft is rotatably installed in the shaft hole; or A shaft sleeve is arranged in the shaft hole, and the free end of the drive shaft is rotatably installed in the shaft sleeve; or A bearing is arranged in the shaft hole, and the free end of the drive shaft is rotatably installed in the bearing.

7. The DC high-pressure plunger pump according to any one of claims 1 to 4, wherein: The limiting portion includes two parallel limiting walls located in the accommodating cavity, and the sliding fit portion includes two parallel sliding fit walls located on the outer peripheral wall of the piston assembly; The sliding fit wall cooperates with the limiting wall to limit the piston to slide only in the first direction.

8. Coffee machine, characterized in that, Including the DC high-pressure plunger pump according to any one of claims 1 to 7.

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