Combined high-pressure common rail fuel injection pump

Abstract

The utility model relates to a combined high-pressure common rail fuel injection pump which comprises a pump body, a pump cover arranged at the upper end of the pump body and a proportional valve arranged outside the upper portion of the pump body, a step is arranged in the upper end of the pump body, two middle holes are formed in the upper portion of the pump body, a through hole is formed in the lower portion of the pump body, and the center lines of the two middle holes are parallel and perpendicular to the center line of the through hole. The oil outlet valve assembly is arranged on a step at the upper end of the pump body; the two plunger and barrel assemblies are respectively arranged in two middle holes in the upper part of the pump body; the two oil inlet valve assemblies are respectively arranged at the upper ends of the two plunger and barrel assemblies; the two guide piston assemblies are respectively matched with the lower parts of the two plunger and barrel assemblies; the gear pump assembly is arranged outside the lower portion of the pump body and connected with the driving mechanism in a matched mode, and the two guide piston assemblies make contact with the driving mechanism correspondingly. The sealing structure is reliable in sealing, can improve the pressure buildup capacity of the fuel injection pump, improves the fuel atomization effect, and improves the fuel use efficiency.

Description

Technical Field

[0001] This utility model relates to marine engines, specifically a combined high-pressure common rail fuel injection pump. Background Art

[0002] Due to increasingly stringent emission regulations and ever-improving emission standards, high-pressure common rail injection technology has been widely applied in engine technology. The high-pressure common rail system mainly consists of an electronic control unit (ECU), a high-pressure fuel pump, a common rail, electronic fuel injectors, and various sensors. Its fuel supply principle involves the high-pressure fuel pump outputting high-pressure fuel, which is then supplied to the electronic fuel injectors via the high-pressure common rail. The precise control of the electronic control system ensures that the fuel is accurately injected into the cylinders. The fuel quantity is adjusted by the opening time of a solenoid valve. The sole function of the injection pump is to build up the required pressure. The higher the pressure the injection pump can build up, the better the fuel atomization and the higher the fuel efficiency. However, this also places higher demands on the high-pressure sealing performance of the fuel pump.

[0003] CN 212479441U discloses a "High-Speed ​​Diesel Engine Combined Common Rail Injection Pump," which employs a four-cylinder single-acting plunger pump design. The cam profile uses an eccentric circle, with each cylinder having a 90° phase angle. It utilizes imported throttling technology to adjust the opening size of the proportional solenoid valve electromagnet according to operating conditions, thus achieving flexible adjustment of the fuel supply. Fuel flow is controlled by the inlet and outlet valves. During filling, the inlet valve remains open; during the plunger's upward movement, the inlet valve is closed, preventing compressed fuel from flowing back to the low-pressure system. Compressed fuel is guided into the pump cover's accumulator chamber through the spring-loaded outlet valve's arc-shaped groove. After the plunger reaches top dead center, the outlet valve closes, preventing high-pressure fuel from flowing back from the accumulator chamber to the plunger sleeve, effectively improving fuel supply efficiency and reducing power consumption. The transmission gear and camshaft are driven by a conical interference fit friction transmission, secured by a locking nut. The design is simple, has good centering, high load-bearing capacity, good impact resistance, and minimal shaft weakening. The technical solution disclosed in this patent document represents a beneficial attempt in its respective technical field. Summary of the Invention

[0004] The purpose of this invention is to provide a combined high-pressure common rail injection pump that is reliably sealed, improves the pressure build-up capability of the injection pump, enhances fuel atomization, and increases fuel efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A combined high-pressure common rail injection pump includes a pump body, a pump cover located at the upper end of the pump body, and a proportional valve located outside the upper part of the pump body. The upper end of the pump body has a step, two central holes in the upper part, and a through hole in the lower part. The centerlines of the two central holes are parallel and perpendicular to the centerline of the through hole. The pump body also includes an outlet valve assembly located on the step at the upper end of the pump body, two plunger assemblies located in the two central holes in the upper part of the pump body, two inlet valve assemblies located at the upper ends of the two plunger assemblies, two guide piston assemblies that respectively cooperate with the lower parts of the two plunger assemblies, a drive mechanism located in the lower part of the pump body, and a gear pump located outside the lower part of the pump body and connected to the drive mechanism. The two guide piston assemblies are respectively in contact with the drive mechanism.

[0007] Furthermore, the pump body is provided with an oil inlet and a first oil passage, a second oil passage, a third oil passage and a fourth oil passage communicating with it.

[0008] Furthermore, the pump cover is provided with two accumulator chambers and two transverse oil passages communicating with the two accumulator chambers. The openings of the two accumulator chambers are provided with steel balls. The steel balls are in close contact with the conical surfaces of the openings of the accumulator chambers and are connected to the internal threads of the openings of the accumulator chambers through screw plugs, thereby pressing the steel balls to achieve high-pressure sealing. The pump cover is provided with an abnormal leakage oil passage and a high-pressure oil outlet.

[0009] Furthermore, the proportional valve is positioned and connected to the outside of the upper part of the pump body by multiple screws; the proportional valve is provided with a fuel inlet and a fuel return port.

[0010] Furthermore, the oil outlet valve assembly includes an oil outlet valve seat disposed on the inner step at the upper end of the pump body, two oil outlet valves disposed on the oil outlet valve seat, an oil outlet valve spring disposed in the pressure chamber of the oil outlet valve, an oil outlet valve spring seat fitted on the upper part of the oil outlet valve spring, and a vertically penetrating leakage oil passage disposed on the oil outlet valve seat; it also includes an O-ring seal disposed on the outer circle of the oil outlet valve seat; the upper surface of the oil outlet valve seat contacts the lower surface of the pump cover to form a high-pressure sealing surface leakage cavity, which communicates with the abnormal leakage oil passage on the pump cover; a connecting cavity is disposed at the lower part of the outer circle of the oil outlet valve seat, which communicates with the fuel inlet on the proportional valve; and an oil inlet channel communicating with the connecting cavity is also provided.

[0011] Furthermore, the plunger assembly includes a plunger sleeve with a stepped hole in the center, and a plunger fitted in the middle and lower part of the stepped hole of the plunger sleeve. The upper end face of the plunger sleeve contacts the lower plane of the oil outlet valve seat to form a high-pressure sealing structure. A lubricating fuel inlet channel is provided in the plunger sleeve, and the upper end of the lubricating fuel inlet channel communicates with the inlet channel on the oil outlet valve seat. A fuel return channel and a fuel return annular groove communicating with it are provided in the plunger sleeve, and the fuel return annular groove communicates with the fuel return hole of the proportional valve. A first plug is provided at the upper end of the fuel return channel. It also includes a plunger spring sleeved on the lower part of the outside of the plunger sleeve and a spring seat connected to the lower end of the plunger.

[0012] Furthermore, a first O-ring and a second O-ring are provided on the outer circumference of the plunger sleeve; a first annular groove, a second annular groove, and a third annular groove are provided at the lower part of the stepped hole of the plunger sleeve; the first annular groove is connected to the lower end of the lubricating fuel inlet channel, and a combined sealing ring is provided in the third annular groove; the second annular groove is connected to the fuel return channel.

[0013] Furthermore, the inlet valve assembly is installed on the upper part of the stepped hole of the plunger sleeve, and includes an inlet valve, an inlet valve spring and an inlet valve spring seat arranged sequentially from top to bottom in the upper part of the stepped hole; an inlet chamber is provided between the upper end of the inlet valve and the lower plane of the outlet valve seat, and low-pressure fuel enters the inlet chamber through the inlet channel of the outlet valve seat.

[0014] Furthermore, the guide piston assembly, which mates with the lower part of the plunger assembly, includes a guide piston and a roller connected to the lower part of the guide piston via a pin. A stop hole is located at one end of the pin where it mates with the guide piston, and a compression spring and a stop pin are installed within this stop hole. An upper lubricating oil passage is located in the middle of the guide piston, and this lubricating oil passage communicates with the second and third lubricating oil passages on the pump body. A lower lubricating oil passage is located at the other end of the pin, and a lubricating oil cavity is located at the center of the other end of the pin. A second plug is installed at the opening of the lubricating oil cavity. One end of the lower lubricating oil passage communicates with the upper lubricating oil passage, and the other end of the lower lubricating oil passage communicates with the lubricating oil cavity.

[0015] Furthermore, the drive mechanism includes a camshaft disposed in the lower through hole of the pump body. The two ends of the camshaft are respectively engaged with the lower through hole of the pump body through bearing bushes. A driven gear is engaged on one end of the camshaft extending out of the through hole. This extended end is connected to the pump body through a flange, and a thrust washer is provided between the pump body and the flange. The other end of the camshaft extending out of the through hole is engaged with a gear pump through a spline sleeve. The gear pump is positioned and connected to the pump body through threaded fasteners. The gear pump is connected to the fuel inlet of the proportional valve through a pipe. The bearing bush at one end of the camshaft is connected to the first lubricating oil channel on the pump body, and the bearing bush at the other end is connected to the fourth lubricating oil channel on the pump body.

[0016] Beneficial effects of the utility model:

[0017] During the filling process, low-pressure fuel enters the inlet chamber of the inlet valve through the inlet channel of the outlet valve seat. The pressure of the fuel entering overcomes the spring force of the inlet spring, opening the inlet valve. The low-pressure fuel enters the pressure chamber of the plunger sleeve. The plunger moves under the action of the camshaft and the guide piston assembly. When the plunger moves upward, the pressure in the plunger sleeve pressure chamber increases, closing the inlet valve and preventing the compressed fuel from flowing back into the fuel system. The compressed fuel is then guided into the accumulator chamber of the pump cover through the outlet valve. When the plunger moves downward, the outlet valve closes under the action of the outlet valve spring and the high-pressure common rail, preventing the high-pressure fuel in the accumulator chamber from flowing back into the plunger sleeve. This effectively improves the fuel atomization effect and increases the fuel pump's supply efficiency. Attached Figure Description

[0018] Figure 1 It is a structural diagram of the utility model;

[0019] Figure 2 This is a schematic diagram of a proportional valve installed on the pump body.

[0020] Figure 3 This is a schematic diagram of the pump cover structure;

[0021] Figure 4 This is a schematic diagram showing the cooperation between the plunger assembly and the inlet valve assembly and outlet valve assembly;

[0022] Figure 5 This is a schematic diagram of the guide piston assembly.

[0023] In the diagram (the markings refer to the technical features):

[0024] 1—Pump body, 10—Oil inlet, 11—First oil passage, 12—Second oil passage, 13—Third oil passage, 14—Fourth oil passage;

[0025] 2—Pump cover, 20—Accumulator chamber, 21—Transverse oil passage, 22—Steel ball, 23—Screw plug, 24—Abnormal leakage oil passage, 25—High-pressure oil outlet;

[0026] 3—Proportional valve, 30—Screw, 31—Fuel inlet, 32—Fuel return port;

[0027] 4—Outlet valve assembly, 40—Outlet valve seat, 41—Outlet valve, 42—Outlet valve spring, 43—Outlet valve spring seat, 44—Leakage passage, 45—O-ring seal, 46—High-pressure sealing surface leakage cavity, 47—Connecting cavity, 48—Inlet channel;

[0028] 5—plunger assembly, 51—plunger sleeve, 52—plunger, 53—first plug, 54—plunger spring, 55—spring seat, 56—first O-ring seal, 57—second O-ring seal, 58—combination seal;

[0029] 511—Lubricating fuel inlet channel, 512—Fuel return channel, 513—Fuel return annular groove, 514—First annular groove, 515—Second annular groove, 516—Third annular groove;

[0030] 6—Inlet valve assembly; 61—Inlet valve; 62—Inlet valve spring; 63—Inlet valve spring seat; 611—Inlet chamber;

[0031] 7—Guide piston assembly; 71—Guide piston; 72—Roller; 73—Pin; 74—Compression spring; 75—Stop pin; 76—Second plug; 711—Upper lubricating oil passage; 731—Lower lubricating oil passage; 732—Lubricating oil chamber;

[0032] 8—Drive mechanism, 81—Camshaft, 82—Bearing shell, 83—Driven gear, 84—Flange, 85—Thrust washer, 86—Spline sleeve;

[0033] 9—Gear pump; 91—Threaded fastener. Detailed Implementation

[0034] The technical solution of this utility model will now be described in detail with reference to the accompanying drawings.

[0035] Reference Figures 1 to 5The illustrated combined high-pressure common rail injection pump includes a pump body 1, a pump cover 2 located at the upper end of the pump body 1, and a proportional valve 3 located on the outer side of the upper part of the pump body 1. The pump body 1 has a step inside the upper end, two central holes in the upper part, and a through hole in the lower part. The center lines of the two central holes are parallel and perpendicular to the center line of the through hole. It also includes an outlet valve assembly 4 located on the step at the upper end of the pump body 1, two plunger assemblies 5 respectively located in the two central holes in the upper part of the pump body 1, two inlet valve assemblies 6 respectively located at the upper ends of the two plunger assemblies 5, two guide piston assemblies 7 respectively cooperating with the lower parts of the two plunger assemblies 5, a drive mechanism 8 located in the lower part of the pump body 1, and a gear pump 9 located on the outer side of the lower part of the pump body 1 and connected to the drive mechanism 8. The two guide piston assemblies 7 are respectively in contact with the drive mechanism 8.

[0036] The pump body 1 is provided with an oil inlet 10 and a first oil channel 11, a second oil channel 12, a third oil channel 13 and a fourth oil channel 14 communicating with it.

[0037] The pump cover 2 is provided with two accumulator chambers 20 and two transverse oil passages 21 communicating with the two accumulator chambers 20. The opening of each of the two accumulator chambers 20 is provided with a steel ball 22. The steel ball 22 is in close contact with the conical surface of the opening of the accumulator chamber 20 and is connected to the internal thread of the opening of the accumulator chamber 20 through a screw plug 23, thereby pressing the steel ball 22 to achieve high pressure sealing. The pump cover 2 is provided with an abnormal leakage oil passage 24 and a high pressure oil outlet 25.

[0038] The proportional valve 3 is positioned and connected to the outside of the upper part of the pump body 1 by multiple screws 30; the proportional valve 3 is provided with a fuel inlet 31 and a fuel return port 32. The fuel supply flow to the injection pump can be controlled by adjusting the proportional valve.

[0039] The oil outlet valve assembly 4 includes an oil outlet valve seat 40 located on the inner step at the upper end of the pump body 1, two oil outlet valves 41 on the oil outlet valve seat 40, an oil outlet valve spring 42 located in the pressure chamber (not shown in the figure) of the oil outlet valve 41, an oil outlet valve spring seat 43 fitted on the upper part of the oil outlet valve spring 42, and a vertically penetrating leakage oil passage 44 on the oil outlet valve seat 40; it also includes an O-ring seal 45 on the outer circle of the oil outlet valve seat 40; the upper surface of the oil outlet valve seat 40 contacts the lower surface of the pump cover 2 to form a high-pressure sealing surface leakage cavity 46, which communicates with the abnormal leakage oil passage 24 on the pump cover 2 to provide timely feedback on the sealing status of the high-pressure sealing surface; a connecting cavity 47 is located at the lower part of the outer circle of the oil outlet valve seat 40, which is connected to the fuel inlet 31 on the proportional valve 3; and an oil inlet channel 48 communicating with the connecting cavity 47 is also provided.

[0040] The plunger assembly 5 includes a plunger sleeve 51 with a stepped hole in the center, and a plunger 52 that fits into the middle and lower part of the stepped hole of the plunger sleeve 51. The upper end face of the plunger sleeve 51 contacts the lower plane of the oil outlet valve seat 40 to form a high-pressure sealing structure. A lubricating fuel inlet channel 511 is provided in the plunger sleeve 51. The upper end of the lubricating fuel inlet channel 511 communicates with the inlet channel 48 on the oil outlet valve seat 40 to lubricate the plunger and plunger sleeve when fuel is introduced. A fuel return channel 512 and a fuel return ring groove 513 communicating with it are provided in the plunger sleeve 51. The fuel return ring groove 513 is connected to the fuel return port 32 of the proportional valve 3. A first plug 53 is provided at the upper end of the fuel return channel 512. It also includes a plunger spring 54 sleeved on the lower part of the outside of the plunger sleeve 51 and a spring seat 55 connected to the lower end of the plunger 52.

[0041] A first O-ring 56 and a second O-ring 57 are provided on the outer circle of the plunger sleeve 51; a first annular groove 514, a second annular groove 515 and a third annular groove 516 are provided at the lower part of the stepped hole of the plunger sleeve 51; the first annular groove 514 is connected to the lower end of the lubricating fuel inlet channel 511, and a combined sealing ring 58 is provided in the third annular groove 516 to prevent low-pressure fuel from entering the guide piston chamber; the second annular groove 515 is connected to the fuel return channel 512; the low-pressure fuel first passes through the inlet channel 48 of the outlet valve assembly 4 in the plunger assembly 5, then through the lubricating fuel inlet channel 511, the first annular groove 514, the second annular groove 515 and the fuel return annular groove 513 of the plunger assembly 5, and then flows back through the fuel return port 32 on the proportional valve 3.

[0042] The inlet valve assembly 6 is installed on the upper part of the stepped hole of the plunger sleeve 51. It includes an inlet valve 61, an inlet valve spring 62 and an inlet valve spring seat 63 arranged sequentially from top to bottom in the upper part of the stepped hole. An inlet chamber 611 is provided between the upper end of the inlet valve 61 and the lower plane of the outlet valve seat 40. Low-pressure fuel enters the inlet chamber 611 through the inlet channel 48 of the outlet valve seat 40.

[0043] The guide piston assembly 7, which cooperates with the lower part of the plunger assembly 5, includes a guide piston 71 and a roller 72 connected to the lower part of the guide piston 71 via a pin 73. A stop hole is located at one end of the pin 73 where it engages with the guide piston 71. A compression spring 74 and a stop pin 75 are installed in this stop hole to prevent the pin from shifting. An upper lubricating oil passage 711 is provided in the middle of the guide piston 71. The lubricating oil passage 711 communicates with the second lubricating oil passage 12 and the third lubricating oil passage 13 on the pump body 1 to lubricate the guide piston assembly. A lower lubricating oil passage 731 is provided at the other end of the pin 73. A lubricating oil cavity 732 is provided at the center of the other end of the pin 73. A second plug 76 is provided at the opening of the lubricating oil cavity 732. One end of the lower lubricating oil passage 731 communicates with the upper lubricating oil passage 711, and the other end of the lower lubricating oil passage 731 communicates with the lubricating oil cavity 732.

[0044] The drive mechanism 8 includes a camshaft 81 disposed in the lower through hole of the pump body 1. Both ends of the camshaft 81 are respectively engaged with the lower through hole of the pump body 1 through bearing bushes 82. A driven gear 83 is engaged on one end of the camshaft 81 that extends out of the through hole. This extended end is connected to the pump body 1 through a flange 84, and a thrust plate 85 is provided between the pump body and the flange. The other end of the camshaft 81 that extends out of the through hole is engaged with a gear pump 9 through a spline sleeve 86. The gear pump 9 is positioned and connected to the pump body 1 through a threaded fastener 87. The gear pump 9 is connected to the fuel inlet 31 of the proportional valve 3 through a pipe. The bearing bush 82 at one end of the camshaft 81 is connected to the first lubricating oil channel 11 on the pump body 1, and the bearing bush 82 at the other end is connected to the fourth lubricating oil channel 14 on the pump body 1.

[0045] Since the inlet valve 61 and the outlet valve seat 40 are provided with an inlet chamber 611, low-pressure fuel can enter the inlet chamber 611 through the inlet channel 48 on the outlet valve seat 40.

[0046] During the fuel inlet process, when the proportional valve 3 controls the fuel inlet pressure to be higher than the spring force of the fuel inlet valve spring 62, the fuel inlet valve 61 is in the open state; when the fuel inlet pressure is lower than the spring force of the fuel outlet valve spring 42, the fuel outlet valve 41 and the fuel outlet valve spring seat 43 are sealed with a conical surface, and low-pressure fuel cannot enter the pressure chamber of the fuel outlet valve 41.

[0047] After the oil is fed in, the plunger 52 moves upward under the action of the camshaft 81 and the guide piston assembly 7. During the upward movement of the plunger 52, the pressure in the plunger cavity increases, which is higher than the combined force of the oil inlet pressure and the spring force of the oil inlet valve spring 63. The oil inlet valve 61 is in the closed state, and the upward movement of the plunger 52 will compress the low-pressure fuel in the plunger cavity, thereby increasing the pressure of the low-pressure fuel in the plunger cavity. The oil inlet valve 61 and the oil outlet valve seat 40 plane contact to form a high-pressure seal, thereby improving the reliability of the seal between the plunger sleeve 51 and the oil outlet valve seat 40 plane, and preventing the compressed fuel from flowing back into the oil inlet channel 48.

[0048] When the pressure of the compressed fuel in the plunger chamber reaches the opening pressure of the delivery valve 41, the delivery valve 41 moves upward, and a gap is formed between the delivery valve 41 and the delivery valve seat 40. The compressed fuel enters the accumulator chamber 20 of the pump cover 2 through the gap and the hole in the delivery valve spring seat 43.

[0049] Obviously, the embodiments described above are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

Claims

1. A combined high-pressure common rail fuel injection pump, comprising a pump body (1), a pump cover (2) arranged at the upper end of the pump body (1), and a proportional valve (3) arranged outside the upper part of the pump body (1), wherein: The pump body (1) has a step at the upper end, two middle holes at the upper part, and a through hole at the lower part, wherein the center lines of the two middle holes are parallel and perpendicular to the center line of the through hole; the pump body (1) also includes an oil outlet valve assembly (4) arranged on the step at the upper end of the pump body (1), two plunger pairs (5) respectively arranged in the two middle holes at the upper part of the pump body (1), two oil inlet valve assemblies (6) respectively arranged at the upper ends of the two plunger pairs (5), two guide piston assemblies (7) respectively matched with the lower parts of the two plunger pairs (5), a driving mechanism (8) arranged at the lower part of the pump body (1), and a gear pump (9) arranged outside the lower part of the pump body (1) and connected to the driving mechanism (8), wherein the two guide piston assemblies (7) are respectively in contact with the driving mechanism (8).

2. The combined high-pressure common rail fuel injection pump according to claim 1 is characterized in that: The pump body (1) is provided with a lubricating oil inlet hole (10) and a first lubricating oil channel (11), a second lubricating oil channel (12), a third lubricating oil channel (13) and a fourth lubricating oil channel (14) communicating with the lubricating oil inlet hole (10).

3. The combined high-pressure common rail fuel injection pump according to claim 1 or 2, characterized in that: The pump cover (2) is provided with two pressure storage chambers (20), and two transverse oil passages (21) communicating with the two pressure storage chambers (20). The mouths of the two pressure storage chambers (20) are provided with steel balls (22). The steel balls (22) are in close contact with the conical surfaces of the mouths of the pressure storage chambers (20), and are matched and connected with the internal threads of the mouths of the pressure storage chambers (20) through screw plugs (23), thereby pressing the steel balls (22) to achieve high-pressure sealing. The pump cover (2) is provided with abnormal leakage oil passages (24) and high-pressure oil outlets (25).

4. The combined high-pressure common rail fuel injection pump according to claim 3 is characterized in that: The proportional valve (3) is positioned and connected to the outside of the upper part of the pump body (1) by means of a plurality of screws (30); the proportional valve (3) is provided with a fuel inlet (31) and a fuel return port (32).

5. The combined high-pressure common rail fuel injection pump according to claim 4 is characterized in that: The oil outlet valve assembly (4) comprises an oil outlet valve seat (40) arranged on an inner step at the upper end of the pump body (1), two oil outlet valves (41) being arranged on the oil outlet valve seat (40), an oil outlet valve spring (42) being arranged in a pressure chamber of the oil outlet valve (41), an oil outlet valve spring seat (43) being matched with an oil outlet valve spring seat (43) on the upper part of the oil outlet valve spring (42), and an oil leakage passage (44) being arranged on the oil outlet valve seat (40) and extending vertically therethrough; and further comprising an O-shaped oil outlet valve seat (44) being arranged on the outer circumference of the oil outlet valve seat (40) The oil outlet valve seat (40) is provided with a shaped sealing ring (45); the upper plane of the oil outlet valve seat (40) contacts the lower plane of the pump cover (2) to form a high-pressure sealing surface leakage cavity (46); the high-pressure sealing surface leakage cavity (46) is communicated with the abnormal leakage oil passage (24) on the pump cover (2); a connecting cavity (47) is provided at the lower part of the outer circle of the oil outlet valve seat (40); the connecting cavity (47) is connected to the fuel inlet (31) on the proportional valve (3); and an oil inlet hole (48) is provided which is communicated with the connecting cavity (47).

6. The combined high-pressure common rail fuel injection pump according to claim 5 is characterized in that: The plunger pair (5) comprises a plunger sleeve (51) having a stepped hole at the center, and a plunger (52) fitted in the middle and lower parts of the stepped hole of the plunger sleeve (51). The upper end surface of the plunger sleeve (51) contacts the lower plane of the oil outlet valve seat (40) to form a high-pressure sealing structure. A lubricating fuel oil inlet hole (511) is provided in the plunger sleeve (51), and the upper end of the lubricating fuel oil inlet hole (511) contacts the oil inlet hole (411) on the oil outlet valve seat (40). 8) connected; a fuel return channel (512) and a fuel return annular groove (513) connected thereto are provided in the plunger sleeve (51), the fuel return annular groove (513) being connected to the fuel return port (32) of the proportional valve (3); a first plug (53) is provided at the upper end of the fuel return channel (512); and further comprising a plunger spring (54) sleeved on the lower portion of the outer surface of the plunger sleeve (51), and a spring seat (55) connected to the lower end of the plunger (52).

7. The combined high-pressure common rail fuel injection pump according to claim 6 is characterized in that: A first O-ring (56) and a second O-ring (57) are provided on the outer circumference of the plunger sleeve (51); a first annular groove (514), a second annular groove (515) and a third annular groove (516) are provided at the lower part of the stepped hole of the plunger sleeve (51); the first annular groove (514) is connected to the lower end of the lubricating fuel oil inlet channel (511), and a combined sealing ring (58) is provided in the third annular groove (516); and the second annular groove (515) is connected to the fuel oil return channel (512).

8. The combined high-pressure common rail fuel injection pump according to claim 7 is characterized in that: The oil inlet valve assembly (6) is mounted on the upper portion of the stepped hole of the plunger sleeve (51), and comprises an oil inlet valve (61), an oil inlet valve spring (62), and an oil inlet valve spring seat (63) which are arranged in sequence from top to bottom in the upper portion of the stepped hole; an oil inlet chamber (611) is provided between the upper end of the oil inlet valve (61) and the lower plane of the oil outlet valve seat (40), and low-pressure fuel enters the oil inlet chamber (611) through the oil inlet channel (48) of the oil outlet valve seat (40).

9. The combined high-pressure common rail fuel injection pump according to claim 8 is characterized in that: The guide piston assembly (7) cooperates with the lower part of the plunger assembly (5), and comprises a guide piston (71), a roller (72) connected to the lower part of the guide piston (71) through a pin shaft (73); a stop hole is provided at one end of the pin shaft (73) at a position cooperating with the guide piston (71), and a compression spring (74) and a stop pin (75) are provided in the stop hole; an upper lubricating oil passage (711) is provided in the middle part of the guide piston (71), and the lubricating oil passage (711) is connected to the upper part of the pump body (1). The second lubricating oil channel (12) and the third lubricating oil channel (13) are connected; a lower lubricating oil channel (731) is provided at the other end of the pin shaft (73); a lubricating oil chamber (732) is provided at the center of the other end of the pin shaft (73); a second plug (76) is provided at the mouth of the lubricating oil chamber (732); one end of the lower lubricating oil channel (731) is connected to the upper lubricating oil channel (711), and the other end of the lower lubricating oil channel (731) is connected to the lubricating oil chamber (732).

10. The combined high-pressure common rail fuel injection pump according to claim 9, characterized in that: The driving mechanism (8) comprises a camshaft (81) disposed in a through hole at the bottom of the pump body (1); the two ends of the camshaft (81) are respectively engaged with the through hole at the bottom of the pump body (1) via bearing bushes (82); a driven gear (83) is engaged with one end of the camshaft (81) extending out of the through hole; the extended end is connected to the pump body (1) via a flange (84); and a thrust plate (85) is provided between the pump body and the flange; the other end of the camshaft (81) extending out of the through hole is connected to the pump body (1) via a flange (84); The spline sleeve (86) is connected to the gear pump (9); the gear pump (9) is positioned and connected to the pump body (1) via a threaded fastener (87); the gear pump (9) is connected to the fuel inlet (31) of the proportional valve (3) via a pipeline; the bearing bush (82) at one end of the camshaft (81) is connected to the first lubricating oil channel (11) on the pump body (1) correspondingly, and the bearing bush (82) at the other end is connected to the fourth lubricating oil channel (14) on the pump body (1) correspondingly.

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