High-pressure common rail fuel injection pump
By using a plunger forced downward device and a one-way valve design, the plunger return spring was eliminated, solving the problems of large size, high noise, and high cost of existing high-pressure common rail injection pumps, and achieving smaller size, higher speed, and lower overall cost.
Patent Information
- Application Number
- CN202521106781.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-02
- Publication Date
- 2026-01-20
- Estimated Expiration
- 2035-06-02
AI Technical Summary
Existing high-pressure common rail injection pumps have drawbacks such as large size, low maximum speed, high noise, and high cost. In particular, the large size and harsh force of the plunger return spring prevent the injection pump from being miniaturized.
The plunger is forced to move downward by means of a plunger, eliminating the plunger return spring. It utilizes the plunger's own oil suction capacity and combines it with the one-way flow design of the inlet and outlet valves to eliminate the fuel pump. The fuel flow direction is controlled by a check valve and a metering solenoid valve to achieve the forced return downward movement of the plunger.
This technology enables the miniaturization of the fuel injection pump, increases the maximum speed, reduces noise and lowers costs, while meeting the requirements for cooling and lubrication.
Smart Images
Figure CN223814122U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a fuel injection pump for engine, in particular to a high pressure common rail fuel injection pump. BACKGROUND
[0002] The high pressure common rail fuel injection pump on engine is a device responsible for pressurizing fuel and providing high pressure fuel to engine. In order to ensure stable and sufficient fuel intake of the fuel injection pump, an additional fuel transfer pump is usually additionally arranged before the fuel injection pump, which brings additional cost to the system.
[0003] The downstroke oil suction stroke of the plunger of the fuel injection pump is realized by the reset spring. Because the plunger runs at high speed and the downstroke time is extremely short, the reset spring is large in size and is subjected to harsh force, which results in large working noise, low maximum speed, and is not conducive to the miniaturization of the fuel injection pump, and the fuel injection pump is high in cost.
[0004] In summary, the high pressure common rail fuel injection pump of the prior art has the disadvantages of large size, low maximum speed, large noise, and high cost. SUMMARY
[0005] The purpose of the present application is to provide a high pressure common rail fuel injection pump, which cancels the fuel transfer pump and the plunger reset spring by setting a plunger forced down device and utilizing the oil suction capacity of the plunger, so as to reduce the size of the fuel injection pump, improve the maximum speed, reduce the noise, and reduce the cost.
[0006] In order to achieve the above purpose, the present application adopts the following technical solutions.
[0007] The present application provides a high pressure common rail fuel injection pump, which comprises a pump body, a camshaft, at least one plunger, and a high pressure module. The plunger is arranged in the compression chamber of the high pressure module and can reciprocate along the axial direction. An oil inlet valve and an oil outlet valve are arranged adjacent to the top of the compression chamber. The oil inlet valve maintains the tendency of one-way flow of fuel from the low pressure fuel passage outside the oil inlet valve to the compression chamber under the action of an oil inlet spring. The oil outlet valve maintains the tendency of one-way flow of fuel from the compression chamber to the high pressure oil outlet outside under the action of an oil outlet spring.
[0008] A cylindrical eccentric wheel is arranged on the camshaft, and a slider rotatable around the shaft is sleeved on the eccentric wheel. A reset block is arranged on the slider. The reciprocating sliding direction of the plunger is perpendicular to the rotation axis of the slider. A push-pull foot is arranged at the bottom of the plunger and is transversely and slidably arranged in the parallel sliding groove between the slider and the reset block. The slider and the bottom of the push-pull foot abut against each other, and the reset block and the back of the push-pull foot abut against each other. The plunger reciprocates with the rotation of the eccentric wheel under the limitation of the slider and the reset block.
[0009] The high-pressure common rail injection pump is provided with a first one-way valve and a second one-way valve; the first one-way valve is connected with the oil inlet of the high-pressure common rail injection pump at the inlet and connected with the low-pressure fuel passage outside the oil inlet valve at the outlet, so as to keep the fuel flowing from the oil inlet to the low-pressure fuel passage in one direction; the second one-way valve is connected with the low-pressure fuel passage at the inlet and connected with the transition oil passage at the outlet, so as to keep the fuel flowing from the low-pressure fuel passage to the transition oil passage in one direction.
[0010] The above structure cancels the plunger return spring, and instead uses a return block following the one-way movement of the slider to realize the forced plunger return downward movement. The external low-pressure fuel is sucked into the compression chamber by the plunger downward movement, and then the additional oil pump is omitted. In order to control the amount of fuel entering the compression chamber, the high-pressure common rail injection pump should be provided with an oil inlet metering electromagnetic valve. In order to ensure a certain amount of fuel to enter the injection pump to meet the cooling and / or lubrication needs, plus the first one-way valve and the second one-way valve, the low-pressure fuel flow is limited.
[0011] Preferably, the first one-way valve is provided with a first one-way spring and a first one-way limit, the first one-way spring keeps the fuel flowing from the oil inlet to the low-pressure fuel passage in one direction, and the first one-way limit limits the maximum opening stroke of the first one-way valve to be not more than 2mm. The second one-way valve is provided with a second one-way spring and a second one-way limit, the second one-way spring keeps the fuel flowing from the low-pressure fuel passage to the transition oil passage in one direction, and the second one-way spring limits the maximum opening stroke of the second one-way valve to be not more than 2mm.
[0012] The first one-way limit, the second one-way limit and the oil outlet limit arranged after the oil outlet valve are beneficial to speed up the valve reset closing speed.
[0013] Preferably, the first one-way valve is arranged in the high-pressure module or the pump body.
[0014] Preferably, the second one-way valve is arranged in the high-pressure module or the pump body.
[0015] Preferably, the high-pressure common rail injection pump is provided with a low-pressure module, one or all of the first one-way valve, the second one-way valve, the oil inlet and the oil return port are arranged in the low-pressure module.
[0016] Preferably, the low-pressure module is further provided with a pressure relief valve; the pressure relief valve includes a pressure relief valve core, a pressure relief limit and a pressure relief spring; one end of the pressure relief spring is pressed on the pressure relief limit, and the other end is pressed on the pressure relief valve core to keep the pressure relief valve core closed; the pressure relief valve includes an inlet and at least one outlet, wherein the inlet is connected with the transition oil passage, and the at least one outlet is connected with the oil return port.
[0017] Preferably, the pressure relief valve and the second check valve are integrated in series in the axial direction, and the pressure relief limit and the second check limit are integrated.
[0018] Preferably, the slider is further provided with a U-shaped belt, the upper two ends of the U-shaped belt press the two sides of the reset pressing block respectively, so that the reset pressing block is fixed on the slider and moves together with the slider; the U-shaped groove at the lower part of the U-shaped belt passes around the eccentric wheel and can rotate axially around the eccentric wheel.
[0019] Preferably, a bearing is arranged between the U-shaped belt and the eccentric wheel, the bearing is fixed with the eccentric wheel, in sliding contact with the eccentric wheel and rotates axially around the eccentric wheel.
[0020] Preferably, the plunger and the push-pull foot are separate independent components, the push-pull foot is arranged at the bottom of the plunger and abuts against each other; the push-pull foot and the plunger are integrally moved up and down by the clasp spring inserted from the side.
[0021] The beneficial effects of the present application are:
[0022] The present application provides a high-pressure common rail fuel injection pump, the downward reset of the plunger is forced, without plunger reset spring, and the fuel injection pump is provided with two check valves in the low-pressure oil circuit to provide necessary cooling and / or lubricating fuel. Therefore, smaller size, higher applicable speed, lower noise and lower comprehensive cost are achieved. BRIEF DESCRIPTION OF DRAWINGS
[0023] Figure 1 is a structural schematic diagram of an embodiment of the high-pressure common rail fuel injection pump of the present application.
[0024] Figure 2 is Figure 1 is a three-dimensional schematic diagram of the forced downward structure of the plunger of the embodiment.
[0025] Figure 3 is a structural schematic diagram of another embodiment of the high-pressure common rail fuel injection pump of the present application.
[0026] Figure 4 is Figure 3 is a three-dimensional schematic diagram of the forced downward structure of the plunger of the embodiment.
[0027] Figure 5 is a structural schematic diagram of another embodiment of the high-pressure common rail fuel injection pump of the present application.
[0028] Figure 6 is Figure 5 is a three-dimensional exploded schematic diagram of the plunger and the push-pull foot structure of the embodiment.
[0029] In the figure: 1-pump body; 2-camshaft; 2a- eccentric wheel; 3-slid; 3a-U-shaped belt; 3b-bushing; 4-resetting block; 5-plunger; 5a-pushing and pulling leg; 5b- leg bottom; 5c- leg back; 5d- clip spring; 6- high pressure module; 6a- compression chamber; 6b- high pressure oil outlet; 7- oil outlet valve; 7a- oil outlet spring; 7b- oil outlet limit; 8- oil inlet valve; 8a- oil inlet spring; 9- oil inlet metering electromagnetic valve; 10- oil return port; 11- low pressure fuel passage; 12- first one-way valve; 12a- first one-way spring; 12b- first one-way limit; 13- second one-way valve; 13a- second one-way spring; 13b- second one-way limit; 14- transition oil way; 15- oil inlet port; 16- pressure relief valve; 16a- pressure relief valve core; 16b- pressure relief limit; 16c- pressure relief spring; 17- low pressure module; 18- cover plate. DETAILED DESCRIPTION
[0030] The application will be further described below in conjunction with the drawings and examples. It can be understood that the specific examples described herein are only used to explain the application, and are not a limitation of the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, not all the structures.
[0031] In the description of the application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.
[0032] In the application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "upper" and "upper" of the first feature to the second feature include that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.
[0033] In the description of the embodiments, the terms "upper", "lower", "left", "right", and the like orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used to distinguish in the description, and have no special meaning. Embodiments
[0034] Figure 1 is a schematic diagram of the structure of an embodiment of the high-pressure common rail fuel injection pump of the present application, Figure 2 is Figure 1 is a three-dimensional schematic diagram of the forced down structure of the plunger of the embodiment.
[0035] A high-pressure common rail fuel injection pump, comprising a pump body 1, a camshaft 2, a plunger 5 and a high-pressure module 6; the plunger 5 is arranged in the compression chamber 6a of the high-pressure module 6 and can slide reciprocatingly along the axial direction, and an oil inlet valve 8 and an oil outlet valve 7 are arranged immediately above the top of the compression chamber 6a; the oil inlet valve 8, under the action of an oil inlet spring 8a, maintains the tendency of one-way flow of fuel from the low-pressure fuel passage 11 outside the oil inlet valve 8 to the compression chamber 6a; the oil outlet valve 7, under the action of an oil outlet spring 7a, maintains the tendency of one-way flow of fuel from the compression chamber 6a to the high-pressure oil outlet 6b outside.
[0036] A cylindrical eccentric wheel 2a is arranged on the camshaft 2, a slider 3 rotatable about the shaft is sleeved on the eccentric wheel 2a, and a reset block 4 is arranged on the slider 3; the reciprocating sliding direction of the plunger 5 is perpendicular to the rotation axis of the slider 3; a push-pull foot 5a is arranged at the bottom of the plunger 5, the push-pull foot 5a is transversely and slidably fitted in the parallel sliding groove between the slider 3 and the reset block 4, the slider 3 and the foot bottom 5b of the push-pull foot 5a abut, the push-pull foot 5a is pushed to make the plunger 5 go up, the reset block 4 and the foot back 5c of the push-pull foot 5a abut, and the plunger 5 is pulled to make the plunger 5 go down; under the restriction of the slider 3 and the reset block 4, the plunger 5 reciprocates with the rotation of the eccentric wheel 2a.
[0037] The high-pressure common rail fuel injection pump is provided with a first one-way valve 12 and a second one-way valve 13; the inlet of the first one-way valve 12 is connected to the oil inlet 15 of the high-pressure common rail fuel injection pump, and the outlet is connected to the low-pressure fuel passage 11 outside the oil inlet valve 8, maintaining the tendency of one-way flow of fuel from the oil inlet 15 to the low-pressure fuel passage 11; the inlet of the second one-way valve 13 is connected to the low-pressure fuel passage 11, and the outlet is connected to the transition oil passage 14, maintaining the tendency of one-way flow of fuel from the low-pressure fuel passage 11 to the transition oil passage 14.
[0038] Fuel passes through the transition oil passage 14 to provide fuel required for cooling and lubrication of the fuel injection pump.
[0039] The above structure cancels the plunger return spring, and instead is followed by the return block of the slider, which realizes the forced plunger return downward movement. The plunger downward movement is used to suck the external low-pressure fuel into the compression chamber, and then the additional oil pump is omitted. In order to control the amount of fuel entering the compression chamber, the high-pressure common rail fuel injection pump should be provided with an oil inlet metering electromagnetic valve 9. In the embodiment, the oil inlet metering electromagnetic valve 9 is a kind of energized opening type electromagnetic valve, that is, the oil inlet valve 8 will keep the opening state when the electromagnetic coil is energized, and will restore the one-way flow trend when the power is off. In order to ensure a certain amount of fuel into the fuel injection pump to meet the cooling and / or lubrication needs, plus the first one-way valve, the second one-way valve, the low-pressure fuel flow is limited.
[0040] The first one-way valve 12 is provided with a first one-way spring 12a and a first one-way limit 12b. The first one-way spring 12a keeps the one-way flow trend of the fuel from the oil inlet 15 to the low-pressure fuel passage 11, and the first one-way limit 12b limits the maximum opening stroke of the first one-way valve 12 to not more than 2mm. The second one-way valve 13 is provided with a second one-way spring 13a and a second one-way limit 13b. The second one-way spring 13a keeps the one-way flow trend of the fuel from the low-pressure fuel passage 11 to the transition oil passage 14, and the second one-way spring 13a limits the maximum opening stroke of the second one-way valve 13 to not more than 2mm.
[0041] The first one-way limit 12b, the second one-way limit 13b and the oil outlet limit 7b arranged after the oil outlet valve 7 are beneficial to speed up the valve reset closing speed.
[0042] The first one-way valve 12 and the second one-way valve 13 are arranged in the high-pressure module 6. Embodiment
[0043] Figure 3 is another high-pressure common rail fuel injection pump embodiment of the present application. Figure 4 is Figure 3 The plunger forced downward structure of the embodiment is a three-dimensional schematic view.
[0044] Different from the foregoing embodiment, the present embodiment has the following differences.
[0045] The high-pressure module 6 is provided with an independent plunger sleeve 6c, which is easier to process. The plunger sleeve 6c and the high-pressure module 6 can adopt different materials, which is more conducive to reducing the material cost.
[0046] Through Figure 4 As can be seen, the high-pressure common rail fuel injection pump includes two parallel plungers 5, each of which is configured with a set of respective eccentric wheels 2a, sliders 3, return blocks 4 and push-pull feet 5a. The eccentric angles of the two eccentric wheels 2a on the camshaft 2 are 180 degrees out of phase.
[0047] The first one-way valve 12 and the second one-way valve 13 are arranged in the pump body 1.
[0048] The oil inlet metering electromagnetic valve 9 is a de-energized opening type electromagnetic valve, that is, the oil inlet valve 8 will remain open when the electromagnetic coil is de-energized, and will restore the tendency of one-way flow when energized. A cover plate 18 is arranged above the oil inlet metering electromagnetic valve 9 to seal the oil passage.
[0049] The slider 3 is further provided with a U-shaped belt 3a, the upper two ends of the U-shaped belt 3a press the two sides of the reset pressing block 4 respectively, so that the reset pressing block 4 is fixed on the slider 3 and moves together with the slider 3; the U-shaped groove below the U-shaped belt 3a passes around the eccentric wheel 2a and can rotate axially around the eccentric wheel 2a.
[0050] A bearing 3b is arranged between the U-shaped belt 3a and the eccentric wheel 2a, the bearing 3b is fixedly attached to the eccentric wheel 2a, in sliding contact with the eccentric wheel 2a and rotates axially around the eccentric wheel 2a. Embodiment
[0051] Figure 5 is a structural schematic diagram of another embodiment of the high-pressure common rail fuel injection pump of the application, Figure 6 is Figure 5 is a three-dimensional exploded schematic diagram of the plunger and push-pull foot structure of the embodiment.
[0052] Different from the foregoing embodiments, the present embodiment has the following differences.
[0053] The high-pressure common rail fuel injection pump is provided with a low-pressure module 17, and the first one-way valve 12, the second one-way valve 13, the oil inlet 15 and the oil return port 10 are all arranged in the low-pressure module 17.
[0054] The low-pressure module 17 is further provided with a pressure relief valve 16; the pressure relief valve 16 comprises a pressure relief valve core 16a, a pressure relief limit 16b and a pressure relief spring 16c; one end of the pressure relief spring 16c presses on the pressure relief limit 16b, and the other end presses on the pressure relief valve core 16a to keep the pressure relief valve core 16a closed; the pressure relief valve 16 comprises one inlet and at least one outlet, wherein the inlet is communicated with the transition oil passage 14, and one of the outlets is communicated with the oil return port 10, and the other outlet is communicated with the oil inlet 15. The pressure relief valve 16 is of a two-stage opening type, the first stage is opened at a lower pressure, and fuel flows back to the oil tank from the oil return port 10 to take away the heat in the fuel injection pump, and the second stage is opened at a higher pressure, and fuel returns to the oil inlet 15 for recycling.
[0055] The pressure relief valve 16 and the second one-way valve 13 are axially connected in series as a whole, and the pressure relief limit 16b and the second one-way limit 13b are integrated.
[0056] The plunger 5 and the push-pull foot 5a are separate independent components, the push-pull foot 5a is arranged at the bottom of the plunger 5 and abuts against each other; the push-pull foot 5a and the plunger 5 are kept integrally moving up and down by the snap spring 5d inserted from the side.
[0057] Obviously, the above-mentioned embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. For those skilled in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present application. Here, it is unnecessary and impossible to enumerate all the implementation modes. Any modification, equivalent substitution and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.
Claims
1. A high pressure common rail fuel injection pump characterised in that: The high-pressure common rail injection pump comprises a pump body (1), a camshaft (2), at least one plunger (5) and a high-pressure module (6); the plunger (5) is arranged in the compression chamber (6a) of the high-pressure module (6) and can slide reciprocally along the axial direction, and an oil inlet valve (8) and an oil outlet valve (7) are arranged close to the top of the compression chamber (6a); the oil inlet valve (8) keeps the fuel in the tendency of unidirectional flow from the low-pressure fuel passage (11) outside the oil inlet valve (8) to the compression chamber (6a) under the action of the oil inlet spring (8a); the oil outlet valve (7) keeps the fuel in the tendency of unidirectional flow from the compression chamber (6a) to the high-pressure oil outlet (6b) outside under the action of the oil outlet spring (7a). The camshaft (2) is provided with a cylindrical eccentric wheel (2a), the eccentric wheel (2a) is sleeved with a slider (3) which can rotate around the shaft, and the slider (3) is provided with a reset block (4); the reciprocating sliding direction of the plunger (5) is perpendicular to the rotation axis of the slider (3); the bottom of the plunger (5) is provided with a push-pull foot (5a), the push-pull foot (5a) is transversely and slidably arranged in the parallel sliding groove between the slider (3) and the reset block (4), the slider (3) abuts against the foot bottom (5b) of the push-pull foot (5a), the push-pull foot (5a) pushes the plunger (5) to move upward, the reset block (4) abuts against the foot back (5c) of the push-pull foot (5a), and the reset block (4) pulls the plunger (5) to move downward; under the limitation of the slider (3) and the reset block (4), the plunger (5) reciprocates with the rotation of the eccentric wheel (2a). The high-pressure common rail injection pump is provided with a first one-way valve (12) and a second one-way valve (13); the inlet of the first one-way valve (12) is connected with the oil inlet (15) of the high-pressure common rail injection pump, the outlet is connected with the low-pressure fuel passage (11) outside the oil inlet valve (8), and the fuel keeps the tendency of unidirectional flow from the oil inlet (15) to the low-pressure fuel passage (11); the inlet of the second one-way valve (13) is connected with the low-pressure fuel passage (11), and the outlet is connected with the transition oil passage (14), so that the fuel keeps the tendency of unidirectional flow from the low-pressure fuel passage (11) to the transition oil passage (14).
2. A high-pressure common-rail fuel injection pump according to claim 1, characterized in that: The first one-way valve (12) is provided with a first one-way spring (12a) and a first one-way limit (12b); the first one-way spring (12a) keeps the tendency of unidirectional flow of the fuel from the oil inlet (15) to the low-pressure fuel passage (11), and the first one-way limit (12b) limits the maximum opening stroke of the first one-way valve (12) to be not more than 2mm. The second one-way valve (13) is provided with a second one-way spring (13a) and a second one-way limit (13b); the second one-way spring (13a) keeps the tendency of unidirectional flow of the fuel from the low-pressure fuel passage (11) to the transition oil passage (14), and the second one-way spring (13a) limits the maximum opening stroke of the second one-way valve (13) to be not more than 2mm.
3. The high-pressure common rail fuel injection pump according to claim 1, characterized in that: The first one-way valve (12) is arranged in the high-pressure module (6) or the pump body (1).
4. The high-pressure common rail fuel injection pump according to claim 1, characterized in that: The second one-way valve (13) is arranged in the high-pressure module (6) or the pump body (1).
5. The high-pressure common rail fuel injection pump of claim 1, wherein: The high-pressure common rail injection pump is provided with a low-pressure module (17); one or all of the first one-way valve (12), the second one-way valve (13), the oil inlet (15) and the oil return port (10) are arranged in the low-pressure module (17).
6. A high-pressure common-rail fuel injection pump according to claim 5, characterized in that: The low-pressure module (17) is further provided with a pressure relief valve (16); the pressure relief valve (16) comprises a pressure relief valve core (16a), a pressure relief limit (16b) and a pressure relief spring (16c); one end of the pressure relief spring (16c) is pressed on the pressure relief limit (16b), and the other end is pressed on the pressure relief valve core (16a) to keep the pressure relief valve core (16a) closed; the pressure relief valve (16) comprises an inlet and at least one outlet, wherein the inlet is communicated with the transition oil way (14), and the at least one outlet is communicated with the oil return port (10).
7. A high-pressure common-rail fuel injection pump according to claim 6, characterized in that: The pressure relief valve (16) and the second one-way valve (13) are axially integrated in series.
8. The high-pressure common rail fuel injection pump of claim 1, wherein: The slider (3) is further provided with a U-shaped belt (3a), the upper two ends of the U-shaped belt (3a) press the two sides of the reset pressing block (4) respectively, so that the reset pressing block (4) is fixed on the slider (3) and moves together with the slider (3); the lower U-shaped groove of the U-shaped belt (3a) passes around the eccentric wheel (2a) and can rotate axially around the eccentric wheel (2a).
9. A high-pressure common-rail fuel injection pump according to claim 8, characterized in that: A bearing (3b) is arranged between the U-shaped belt (3a) and the eccentric wheel (2a), the bearing (3b) is fixed with the eccentric wheel (2a), in sliding contact with the eccentric wheel (2a) and rotates axially around the eccentric wheel (2a).
10. The high-pressure common-rail fuel injection pump according to claim 1, characterized in that: The plunger (5) and the push-pull foot (5a) are separate independent components, the push-pull foot (5a) is arranged at the bottom of the plunger (5) and abuts against each other; the push-pull foot (5a) and the plunger (5) are integrally moved up and down by the snap spring (5d) inserted from the side.