FI20215003A1 - Multi-cylinder combined high pressure oil pump for marine low speed engine - Google Patents

Abstract

The present disclosure discloses a multi-cylinder combined high pressure oil pump for a marine low speed engine, comprising a pump body assembly (1), a pump cover (2), and a cam shaft (10). The pump body assembly (1) comprises a pump body (101) and bearing bushes (102). The pump body (101) is provided with a first horizontal central hole and a plurality of first vertical central holes. The first horizontal central hole is communicated with the first vertical central holes. The pump cover (2) is mounted on the upper side of the pump body (101). The pump cover (2) is provided with a second horizontal central hole (201) and a plurality of second vertical central holes which are communicated with one another. A plunger and barrel assembly (4), a plunger spring (6), a lower spring seat (7), and a guide piston assembly (8) are mounted in each vertical central hole formed by the corresponding first vertical central hole and the corresponding second vertical central hole. Each plunger and barrel assembly (4) is in threaded connection to the interior of the corresponding second vertical central hole. An oil inlet and outlet valve assembly (9) is mounted in each plunger and barrel assembly (4). The cam shaft (10) is mounted in the first horizontal central hole of the pump body (101). A cooling circulating oil way is arranged in an electrically controlled proportional valve. A mixed oil way is arranged in the pump cover (2). By means of electronic control, oil way layering, and sealing structure optimization, the oil supply regulation flexibility and the heavy oil reliability of a high pressure oil pump are improved; meanwhile, the application range of heavy oil of the low speed engine is expanded; the using environment of 750 Cst heavy oil is met.

Description

MULTI-CYLINDER COMBINED HIGH PRESSURE OIL PUMP FOR MARINE LOW SPEED ENGINE

TECHNICAL FIELD The present disclosure relates to the field of fuel systems for marine low speed engines, and in particular to a multi-cylinder combined high pressure oil pump for a marine low speed engine.

BACKGROUND An electrically controlled common rail fuel system can realize accurate con- trol of oil injection timing and circulating oil injection quantity, and is one of ef- fective means for a high-power marine diesel engine to realize high oil economy and low hazard emission. The existing mechanical single high pressure oil pump + common rail pipe + ICU + mechanical oil injector system of an oil system of a low speed engine realizes flexible control of injection timing and circulating oil injection quantity of the low speed engine. However, there are certain limitations on a flexible regulation aspect of circulating oil supply quantity and oil supply frequency of the high pressure oil pump, which is not beneficial to common rail pressure fluctuation control. However, the existing combined oil pump propor- — tional valve is generally of a non-cooled structure, which cannot meet the operat- ing environment of high temperature high viscosity 750 Cst heavy oil. A plunger sleeve is connected by using a bolt, so the sealing surface of the plunger sleeve is special-shaped, which is not beneficial to the sealing reliability of high tempera- ture high pressure heavy oil and the machining difficulty is high. N 25 x SUMMARY ? The objective of the present disclosure is to provide a multi-cylinder com- © bined high pressure oil pump for a marine low speed engine to solve the problems i in the prior art. By means of electronic control, oil way layering, and sealing struc- S 30 ture optimization, the oil supply regulation flexibility of a high pressure oil pump = and the heavy oil reliability are improved; meanwhile, the application range of the heavy oil of the low speed engine is expanded; the using environment of 750 Cst heavy oil is met. In order to achieve the aforementioned objective, the present disclosure provides the following solution: The present disclosure provides a multi-cylinder combined high pressure oil pump for a marine low speed engine, including a pump body assembly, a pump cover, and a cam shaft.

Wherein, the pump body assembly includes a pump body and bearing bushes. The pump body is provided with a first horizontal central hole and a plurality of first vertical central holes. The first horizontal central hole is communicated with the first vertical central holes.

The pump cover is mounted on the upper side of the pump body. The pump — cover is provided with a second horizontal central hole and a plurality of second vertical central holes. Each of the second vertical central holes is communicated with the second horizontal central hole. One first vertical central hole is corre- spondingly communicated with one of the second vertical central holes. An elec- trically controlled proportional valve and a heavy oil outlet connector are mounted onthe pump cover. A plunger and barrel assembly, a plunger spring, a lower spring seat, and a guide piston assembly are mounted, in sequence from top to bottom, in each vertical central hole formed by the corresponding first vertical central hole and the corresponding second vertical central hole. The plunger and barrel assem- bly is in threaded connection to the interior of the second vertical central hole. an oil inlet and outlet valve assembly is mounted in the plunger and barrel assembly. The low pressure heavy oil output by the electrically controlled proportional valve flows into a plunger volumetric cavity of the plunger and barrel assembly after being delivered through the oil inlet and outlet valve assembly. The high pressure heavy oil pressurized in the plunger volumetric cavity flows out through the oil S 25 inlet and outlet valve assembly, the second horizontal central hole, and the heavy = oil outlet connector in sequence. The lower spring seat is mounted in the guide x piston assembly. The plunger spring is mounted between the plunger and barrel I assembly and the lower spring seat.

a 0 The cam shaft is mounted in the first horizontal central hole of the pump body, S 30 — isradially located by the bearing bushes, and is axially located by thrust bearings N and end covers which are mounted at the two ends of the pump body. The cam N shaft is provided with a plurality of cams which are respectively corresponding to the guide piston assemblies arranged in various first vertical central holes. A cooling circulating oil way is arranged in the electrically controlled proportional valve.

The cooling circulating oil way is communicated with a sec- ond cooling oil way arranged in the pump cover.

A mixed oil way is arranged in the pump cover.

The mixed oil way is communicated with a mixed oil outlet con- nector arranged on the pump cover.

The mixed oil way is arranged between the — second cooling oil way and the plunger volumetric cavity of the plunger and barrel assembly.

Preferably, the plunger and barrel assembly includes a plunger sleeve and a plunger.

A first mounting hole is formed in the upper part of the plunger sleeve.

A second mounting hole is formed in the lower part of the plunger sleeve.

The oil inlet and outlet valve assembly is mounted in the first mounting hole.

The plunger is inserted into the second mounting hole in a sliding manner.

The plunger volu- metric cavity of the plunger is formed between the first mounting hole and the second mounting hole.

A first mixed oil groove and a first cooling oil groove which are formed around the plunger are formed in the inner wall of the plunger sleeve.

A second mixed oil groove and a second cooling oil groove are formed in the external circumferential direction of the plunger sleeve.

The first mixed oil groove is communicated with the second mixed oil groove through an oil channel.

The second mixed oil groove is communicated with the mixed oil way on the pump cover.

The first cooling oil groove is communicated with the second cooling — oil groove through the oil channel.

The second cooling oil groove is communi- cated with the second cooling oil way on the pump cover.

An oil inlet channel is further formed in the plunger sleeve.

The oil inlet channel is communicated with the outer surface of the plunger sleeve and the first mounting hole.

Preferably, a stress transition ring cavity is formed in the hole wall of the first S 25 mounting hole in the plunger sleeve.

The stress transition ring cavity is a ring 5 cavity of which the aperture is gradually decreased from top to bottom.

The stress x transition ring cavity is arranged at the position opposite to the first three screw I threads in the upper end part of the plunger sleeve. a 0 Preferably, the guide piston assembly includes a guide piston and a roller as- S 30 sembly.

A first mounting cavity used for mounting the lower spring seat is formed N in the upper end surface of the guide piston.

A second mounting cavity for mount- N ing the roller assembly is formed in the lower side of the guide piston.

The roller assembly includes a roller, a roller bushing which is interference-fitted in the roller, a roller pin which is clearance-fitted in the roller bushing, and the thrust bearings which are interference-fitted at the axial two ends of the roller. A lubri- cating oil groove is formed in the outer circumference of the guide piston. First lubricating oil channels which are arranged obliquely are formed in the roller pin. Second lubricating oil channels which are arranged circumferentially are formed inthe roller bushing. One end of each first lubricating oil channel is communicated with the corresponding second lubricating oil channel. The other end of each first lubricating oil channel is arranged at the position opposite to the corresponding guide piston. The first lubricating oil channels are communicated with the lubri- cating oil groove. A retaining ring is arranged on each of the two ends of each roller pin in a sleeving manner. The retaining rings fit each guide piston. Preferably, the first mounting cavity is in a shape with a convex center and a concave outer side. A collar mounting groove is formed in the convex part, in the first mounting cavity, of the guide piston. A collar is mounted in the collar mount- ing groove. The lower spring seat is fixedly connected to the guide piston through the collar. The lower cylindrical head of the plunger is limited between the lower spring seat and the guide piston. The lower end surface of the lower cylindrical head of the plunger fits the upper end surface of the guide piston.

Preferably, the oil inlet and outlet valve assembly includes an oil inlet valve assembly and an oil outlet valve assembly. The oil inlet valve assembly includes an oil inlet valve seat, an oil inlet valve, and an oil inlet valve spring. The oil inlet valve is mounted in an oil inlet valve cavity formed in the oil inlet valve seat. The oil inlet valve cavity is communicated with each of the oil inlet channel and the plunger volumetric cavity. The oil inlet valve spring is used for pushing the oil inlet valve to form conical sealing with the oil inlet valve cavity. The oil outlet S 25 — valve assembly includes an oil outlet valve seat, an oil outlet valve, an oil outlet = valve spring, and an oil outlet valve spring seat. The oil outlet valve seat is ar- x ranged on the upper side of the oil inlet valve seat. A high pressure oil outlet cavity I which is communicated with the plunger volumetric cavity is formed in the oil N outlet valve seat. The oil outlet valve is mounted in the oil outlet valve cavity S 30 formed in the oil outlet valve seat. The oil outlet valve cavity is communicated N with the high pressure oil outlet cavity. The oil outlet valve spring is used for N pushing the oil outlet valve to form conical sealing with the oil outlet valve cavity. The oil outlet valve spring seat is mounted on the upper side of the oil outlet valve seat. The oil outlet valve spring is limited between the oil outlet valve spring seat and the cavity wall of the oil outlet valve cavity.

A through hole which is commu- nicated with the oil outlet valve cavity and the second horizontal central hole is formed in the oil outlet valve spring seat.

Preferably, the electrically controlled proportional valve includes a valve 5 — body, a proportional valve coupling, a spring , a push rod, an isolation sleeve, and an electromagnet.

The proportional valve coupling is arranged in the valve body.

The spring is arranged in the valve body.

The spring is arranged on one side of the proportional valve coupling.

The push rod and the isolation sleeve are arranged in the valve body.

The isolation sleeve is arranged on the push rod in a sleeving man- ner.

The push rod and the isolation sleeve are arranged on the other side of the proportional valve coupling.

The electromagnet is arranged on the outer side of the valve body.

The electromagnet is connected with the push rod.

A cooling oil inlet channel, a cooling cavity, and a cooling oil return channel which are seguen- tially communicated are formed in the valve body.

The cooling cavity is formed around part of the push rod.

The cooling cavity fits the electromagnet.

A waste oil cavity and a waste oil channel which are communicated with each other are further formed in the valve body.

The waste oil cavity is arranged around part of the iso- lation sleeve.

A heavy oil inlet channel, a heavy oil cavity, and a heavy oil outlet channel which are sequentially communicated are further formed in the valve — body.

The heavy oil cavity is arranged around the push rod.

The area of the oil inlet cross section of the heavy oil inlet channel is greater than that of the oil outlet cross section of the heavy oil outlet channel.

Compared with the prior art, the multi-cylinder combined high pressure oil pump for the marine low speed engine achieves the following technical effects: S 25 (1). According to the multi-cylinder combined high pressure oil pump for the 5 marine low speed engine provided by the present disclosure, by means of elec- x tronic control, oil way layering, and sealing structure optimization, the oil supply I regulation flexibility of a high pressure oil pump and the heavy oil reliability are a 0 improved.

Meanwhile, the application range of heavy oil of the low speed engine S 30 is expanded; the using environment of 750 Cst heavy oil is met.

Specifically, the N electrically controlled proportional valve is additionally arranged, and the isola- N tion sleeve for isolating the heavy oil is arranged in the electrically controlled pro- portional valve, so high temperature heavy oil is prevented from being in direct contact with the electromagnet of the electrically controlled proportional valve,

and the damage and corrosion of the electromagnet caused by high temperature is avoided. The electrically controlled proportional valve has a forced cooling struc- ture. Cooling oil is from a lubricating oil inlet way inside the combined heavy oil pump. Cooling return oil also flows back to a lubricating oil tank through the lu- bricating oil return way inside the combined heavy oil pump. A low temperature lubricating oil and high temperature low pressure heavy oil leakage mixed oil channel is formed outside the isolation sleeve, so that the cooling is prevented from being polluted, and the mixed waste oil also flows back to a waste oil tank through the mixed oil return way inside the combined heavy oil pump.

(2). According to the multi-cylinder combined high pressure oil pump for the marine low speed engine provided by the present disclosure, the guide piston as- sembly has symmetrical multi-point lubricating structures. The lubricating oil is introduced to the roller pin, a roller bushing, the roller, and the thrust bearings through the guide piston and the oil channels in the two sides of the roller pin, so as to ensure full lubricating of these movement pieces.

(3). According to the multi-cylinder combined high pressure oil pump for the marine low speed engine provided by the present disclosure, the oil inlet and outlet valve assembly is mounted in the plunger sleeve. A spring seat is arranged on the oil inlet and outlet valve assembly. The plunger sleeve is connected with the pump — cover through large external screw threads to press and seal the oil inlet and outlet valve assembly. The oil inlet and outlet valve assembly is arranged up and down, its sealing surface is of symmetrical annular sealing, so the sealing reliability is improved. The oil inlet and outlet valve assembly adopts a universal design. The oil inlet valve is the same as the air outlet valve, and the oil inlet valve spring is S 25 the same as the oil outlet valve spring, so the cost is reduced, and meanwhile, a 5 low pressure circulating function of the heavy oil is met.

x (4). According to the multi-cylinder combined high pressure oil pump for the I marine low speed engine provided by the present disclosure, the oil way in the oil a 0 pump is divided into four layers, wherein the lower layer is the cooling lubricating S 30 oil way; the lubricating oil enters from the middle of the pump body, is distributed N to the two sides to lubricate and cool the guide piston assembly, is distributed N downwards to lubricate and cool the bearing bushes and the thrust bearings, is distributed upwards to lubricate and cool the plunger and barrel assembly, then is distributed upwards to cool the electrically controlled proportional valve and flows back into the cooling oil way of the pump body from the oil channel inside the pump cover, and finally, flows back to the lubricating oil tank through an oil hole in a front end cover of the high pressure oil pump. The middle layer is a mixed oil way for the oil with slightly high temperature; lubricating cooling oil leakage in the lower part of the plunger and high temperature heavy oil leakage in the upper part of the plunger flow back to the waste oil tank through a mixed oil outlet connector at the tail end of the pump cover after being mixed. The upper layer is a high temperature heavy oil low pressure oil way; the high temperature low pressure heavy oil from the electrically controlled proportional valve enters — the plunger volumetric cavity through the pump cover, the plunger sleeve and the oil inlet valve. The top layer is a high temperature heavy oil high pressure oil way; low pressure high temperature heavy oil enters a high temperature heavy oil high pressure oil way at the top of the pump cover through the oil outlet valve after being pressurized by the plunger. Through layered design of the oil ways, the low temperature cooling lubricating oil, the mixed waste oil, and the high temperature heavy are isolated from one another, which can effectively improve the cooling efficiency of the lubricating oil, improve the working reliability of the movement pieces, such as the plunger and barrel assembly and the guide piston assembly, and meet the using conditions of the high temperature heavy oil.

BRIEF DESCRIPTION OF THE DRAWINGS To describe the technical solutions in the embodiments of the present disclo- sure or in the prior art more clearly, the following briefly introduces the accompa- nying drawings required for describing the embodiments. Apparently, the accom- S 25 — panying drawings in the following description are merely some embodiments of 5 the present disclosure, and those of ordinary skill in the art may still derive other x drawings from these accompanying drawings without creative efforts. I FIG. 1 is a schematic structural diagram of a multi-cylinder combined high a 0 pressure oil pump for a marine low speed engine; S 30 FIG. 2 isa schematic structural diagram of a plunger and barrel assembly of N the multi-cylinder combined high pressure oil pump for the marine low speed en- N . gine; FIG. 3 is a schematic structural diagram of a guide piston of the multi-cylinder combined high pressure oil pump for the marine low speed engine;

FIG. 4 is a schematic structural diagram of a roller pin of the multi-cylinder combined high pressure oil pump for the marine low speed engine; FIG. 5 is a schematic structural diagram of an oil inlet and outlet valve as- sembly of the multi-cylinder combined high pressure oil pump for the marine low speed engine; FIG. 6 is a schematic structural diagram of the fit of a pump cover, the oil inlet and outlet valve assembly, and the plunger and barrel assembly of the multi- cylinder combined high pressure oil pump for the marine low speed engine; FIG. 7 is a schematic structural diagram of the electrically controlled propor- — tional valve of the multi-cylinder combined high pressure oil pump for the marine low speed engine; FIG. 8 is a schematic diagram of the oil way arrangement in the structure of the multi-cylinder combined high pressure oil pump for the marine low speed en- gine.

Reference signs in the drawings: 1-pump body assembly; 101-pump body; 102-bearing bush; 103-first cooling oil way; 2-pump cover; 201-second horizontal central hole; 202-hight pressure oil channel; 203-second cooling oil way; 301- valve body; 302-proportional valve coupling; 303-spring; 304-push rod; 305-iso- lation sleeve; 306-electromagnet; 307-cooling oil inlet channel; 308-cooling cav- ity; 309-cooling oil return channel; 310-waste oil channel; 311-waste oil cavity; 312-heavy oil inlet channel; 313-heavy oil cavity; 314-heavy oil outlet channel; 4-plunger and barrel assembly; 401-plunger volumetric cavity; 402-plunger sleeve; 403-first mounting hole; 404-plunger; 405-first mixed oil groove; 406-first cooling oil groove; 407-second.mixed oil groove; 408-second cooling oil groove; S 25 409-oil inlet channel; 410-stress transition ring cavity, 5-heavy oil outlet con- 5 nector; 6-plunger spring; 7-lower spring seat; 8-guide piston assembly; 801-thrust 3 bearing; 802-first mounting cavity; 803-roller; 804-roller bushing; 805-roller pin; I 806-thrust bearing; 807-lubricating oil groove; 808-first lubricating oil way; 809- a 0 second lubricating oil way; 810-retaining ring; 811-collar mounting groove, 812- S 30 oblique annular groove; 9-oil inlet and outlet valve assembly; 901-oil inlet valve N seat; 902-oil inlet valve; 903-oil inlet valve spring; 904-oil outlet valve seat; 905- N high pressure oil outlet cavity; 906-oil outlet valve; 907-oil outlet valve spring; 908-oi] outlet valve spring seat; 10-cam; 11-thrust bearing; 12-end cover; 13- mixed oil outlet connector.

DETAILED DESCRIPTION The technical solution of the embodiments of the present disclosure will now be further described clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embod- iments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present disclosure.

The objective of the present disclosure is to provide a multi-cylinder com- bined high pressure oil pump for a marine low speed engine, so as to solve the problems in the prior art.

To make the aforementioned purpose, features, and advantages of the present disclosure more apparent and more comprehensible, the present disclosure is fur- — ther described in detail below with reference to the accompanying drawings and specific embodiments.

The embodiment of the present disclosure provides a multi-cylinder com- bined high pressure oil pump for a marine low speed engine, as shown in FIG. 1 to FIG. 8, including a pump body assembly 1. The pump body assembly 1 includes apump body 101 and bearing bushes 102. The pump body 101 is provided with a first horizontal central hole and a plurality of first vertical central holes. The first horizontal central hole is communicated with the first vertical central holes. Spe- cifically, the horizontal central hole is formed in the lower part of the pump body 101, and penetrates through the left side and the right side of the pump body 101.

S 25 The first vertical central holes are formed in the upper end surface of the pump 5 body 101. A bearing bush 102 is interference-fitted at each of the two ends of the x horizontal central hole of the pump body 101. The bearing bushes 102 are inter- I ference-fitted at the two ends of the horizontal central hole. The bearing bushes a 0 are soft low-carbon steel. The working surface of each bearing bush is coated with S 30 — a multi-element alloy coating.

N A pump cover 2 is mounted on the upper side of the pump body 101. The N pump cover 2 is provided with a second horizontal central hole 201 and a plurality of second vertical central holes. Each of the second vertical central holes is com- municated with the second horizontal central hole 201. One first vertical central hole is correspondingly communicated with one of the second vertical central holes.

An electrically controlled proportional valve and a heavy oil outlet con- nector 5 are mounted on the pump cover 2. The pump cover 2 consists of a small cuboid located above and a large cuboid located below.

The small cuboid and the large cuboid are formed integrally.

The second horizontal central hole 201 is formed in the small cuboid above and is formed in the length direction of the small cuboid.

The second vertical central holes are formed in the large cuboid below.

The apertures, dimensions and the like of the second vertical central holes and the first vertical central holes are all not determined.

The second vertical central holes and the first vertical central holes are arranged according to the shapes, dimen- sions and the like of the parts mounted therein.

The second vertical central holes are communicated to the second horizontal central hole 201 through a high pres- sure oil channel 202. With regard to the pump cover 2, two threaded holes are uniformly distributed in the horizontal central hole of the upper end surface of the pump cover 2 and are used for mounting lifting rings.

The bottoms of the threaded holes are arranged at a certain distance from the second horizontal central hole 201 to ensure the strength of the pump cover 2. A groove is formed in the groove bottom of one side, connected to the high pressure oil channel 202, of each second vertical central hole.

A sealing ring band is arranged at the bottom of each second vertical central hole to be in contact with the oil inlet and outlet valve assembly 9 to form a high pressure sealing cavity.

The contact surface between each sealing ring band and the oil inlet and outlet valve assembly 9 requires high flatness and roughness.

The widths of the sealing ring bands are reduced by forming the grooves, so the processing difficulty of the S 25 sealing ring bands is reduced, thereby improving the processing accuracy of the 5 sealing ring bands, making the sealing ring bands meet the requirement of high x pressure sealing better, and improving the impact resistance of the pump cover 2. I A plunger and barrel assembly 4, a plunger spring 6, a lower spring seat 7 and a 0 a guide piston assembly 8 are mounted, in seguence from top to bottom, in each S 30 vertical central hole formed by the corresponding first vertical central hole and the N corresponding second vertical central hole.

N The plunger and barrel assembly 4 is in threaded connection to the interior of the second vertical central hole.

The oil inlet and outlet valve assembly 9 is mounted in the plunger and barrel assembly 4. The low pressure heavy oil output by the electrically controlled proportional valve flows into a plunger volumetric cavity 401 of the plunger and barrel assembly 4 after being delivered through the oil inlet and outlet valve assembly 9. The high pressure heavy oil pressurized in the plunger volumetric cavity 401 flows out through the oil inlet and outlet valve assembly 9, the second horizontal central hole 201, and the heavy oil outlet con- nector 5 in sequence.

The lower spring seat 7 is mounted in the guide piston assembly 8. The plunger spring 6 is mounted between the plunger and barrel assembly 4 and the lower spring seat 7. Specifically, a lower spring seat mounting groove is formed in one side, facing the plunger and barrel assembly 4, of the guide piston assembly 8, so the lower spring seat 7 is mounted in the lower spring seat mounting groove.

A cam shaft 10 is mounted in the first horizontal central hole of the pump body 101, is radially located by the bearing bushes 102, and is axially located by thrust bearings 11 and end covers 12 which are mounted at the two ends of the pump body 101. The cam shaft 10 is provided with a plurality of cams which are respectively corresponding to the guide piston assemblies 8 arranged in various first vertical central holes. Specifically, the cams on the cam shaft 10 are disc- shaped components which rotate around a fixed axis and have varying diameters. The corresponding guide piston assembly 8 is driven to move upward when the — cam shaft 10 rotates. As shown in FIG. 1 and FIG. 6, the end covers 12 are con- nected and fixed to the pump body 101 in a threaded connection manner. A sealing ring for improving the sealing performance is arranged on the end surface, in con- tact with the pump body 101, of each end cover 12. The thrust bearings 11 are arranged on the cam shaft 10 in a sleeving manner and are limited between the S 25 — end cover 12 and the cam shaft 10.

5 A cooling circulating oil way is arranged in the electrically controlled propor- x tional valve. The cooling circulating oil way is communicated with a second cool- I ing oil way 203 arranged in the pump cover 2. A mixed oil way is arranged in the a 0 pump cover 2. The mixed oil way is communicated with a mixed oil outlet con- S 30 — nector 13 arranged on the pump cover 2. The mixed oil way is arranged between N the second cooling oil way 203 and the plunger volumetric cavity 401 of the N plunger and barrel assembly 4. The electrically controlled proportional valve serves as a hydraulic control device, which has an oil inlet throttling effect. The electrically controlled proportional valve is mainly used for oil inlet regulation and control of light oil and heavy oil outlet connectors, such as a gasoline or diesel heavy oil outlet connector.

In the prior art, there is no solution for applying the electrically controlled proportional valve to the oil inlet regulation and control of heavy oil.

The reason is that when the heavy oil works, its temperature can reach upto 160 DEG C, which has exceeded the limit operating temperature of electri- cally controlled elements, such as an armature and a coil, of the existing electri- cally controlled proportional valve.

In the prior art, a mechanical design of trans- mission is adopted aiming at the oil inlet regulation of a high pressure oil pump using the heavy oil, namely, the oil quantity is controlled by a speed regulator and — a spiral groove above the plunger.

However, this oil inlet regulation mode has the defects of low oil guantity regulation accuracy and slow response, and has the disadvantage that the oil guantity depends on the rotating speed of the speed reg- ulator.

In the embodiment of the application, the temperature of the existing me- chanical regulation mode can be solved by applying the electrically controlled proportional valve to regulate the oil inlet of the heavy oil.

In a targeted manner, the cooling circulating oil way is arranged in the electrically controlled propor- tional valve to make the cooling oil which flows in the pump cover 2 enter the electrically controlled proportional valve to perform targeted cooling on the elec- trically controlled elements in the electrically controlled proportional valve, so — that the electrically controlled elements of the electrically controlled proportional valve are kept within a normal temperature range.

The cooling circulating oil way designed in the electrically controlled proportional valve should meet the follow- ing reguirements: 1, the cooling circulating oil way is as close as possible to the electrically controlled elements, such as the coil and the armature, of the electri- S 25 cally controlled proportional valve; 2, the flow rate of the cooling oil introduced 5 into the heavy oil outlet connector and the cooling circulating oil way can reduce x the temperature of the electrically controlled elements, such as the coil and the I armature, to be within the working temperature range.

In order to make the cooling N circulating oil way meet the reguirements, simulation calculation and experiments S 30 need to be performed for the armatures of different models in advance to deter- N mine specific parameter information, such as spatial arrangement and dimension, N of the cooling circulating oil way of each model.

The design has the advantages that the cooling circulating oil way is arranged in the electrically controlled proportional valve, which reduces the temperature of the armature and the coil of the electrically controlled proportional valve, so that the electrically controlled elements work in the normal temperature range, thereby allowing the use of the electrically controlled proportional valve to perform oil inlet throttling on the pump. The electrically controlled proportional valve over- comes the defects of mechanical oil quantity regulation, improves the accuracy, flexibility, and response speed of the oil quantity regulation, and then realizes ac- curate matching of oil supply amount of the pump and the operating condition of a diesel engine, avoids the reduction of performance caused by insufficient oil supply, and reduces surplus flow during work, thereby reducing the actual load of — the pump.

As shown in FIG. 2, the plunger and barrel assembly 4 includes: a plunger sleeve 402 and a plunger 404. A first mounting hole 403 is formed in the upper part of the plunger sleeve, and a second mounting hole is formed in the lower part of the plunger sleeve. The oil inlet and outlet valve assembly 9 is mounted in the first mounting hole 403.

The plunger 404 is inserted into the second mounting hole in a sliding manner.

The plunger volumetric cavity 401 is formed between the first mounting hole 403 and the second mounting hole.

A first mixed oil groove 405 and a first cooling oil groove 406 which are — formed around the plunger 404 are formed in the inner wall of the the plunger sleeve 402.

A second mixed oil groove 407 and a second cooling oil groove 408 are formed in the external circumferential direction of the plunger sleeve 402.

The first mixed oil groove 405 is communicated with the second mixed oil S 25 — groove 407 through an oil channel. The second mixed oil groove 407 is commu- 5 nicated with the mixed oil way on the pump cover 2.

x The first cooling oil groove 406 is communicated with the second cooling oil I groove 408 through the oil channel. The second cooling oil groove 408 is com- a 0 municated with the second cooling oil way 203 in the pump cover 2.

S 30 An oil inlet channel 409 is further formed in the plunger sleeve 402. The oil N inlet channel 409 is communicated with the outer surface of the plunger sleeve N 402 and the first mounting hole 403. The first mixed oil groove 405 is formed in the upper side of the first cooling groove 406. The second mixed oil groove 407 is formed in the upper side of the second cooling groove 408. The cooling oil of the first cooling oil way 103 in the pump body 101 flows into a second cooling oil way 203 of the pump cover 2 for providing oil for the second cooling groove 408, and flows to the position between the plunger 404 and the plunger sleeve 402 through the oil channel for providing cooling lubricating.

When the high pressure — heavy oil in the plunger volumetric cavity 401 flows out through a gap between the plunger 404 and the plunger sleeve 402, it flows out to the second mixed oil groove 407 through the oil channel at the first mixed oil groove 405, and then flows to the mixed oil outlet connector 13 through the mixed oil way on the pump cover 2. The oil inlet channel 409 is communicated with an oil outlet end of the electrically controlled proportional valve.

The low pressure heavy oil output from the electrically controlled proportional valve flows into the oil inlet and outlet valve assembly 9 in the first mounting hole 403 through the oil inlet channel 409, and then performs subsequent actions.

Meanwhile, a plurality of sealing ring grooves are also formed in the external circumferential direction of the plunger sleeve 402. The sealing performance between the plunger sleeve 402 and the pump body 101 is improved by mounting sealing rings in the plurality of the sealing ring grooves.

In the embodiment, the surface, matched with the pump body 101, of the lower cuboid of the pump cover 2 is a plane.

The difficulty in processing the sec- — ond vertical central holes serving as plunger sleeve holes in the lower cuboid is relatively low.

Meanwhile, the mounting mode of the plunger sleeve 402 and the pump cover 2 is to perform threaded connection in the second vertical central holes, the lower surface of the lower cuboid does not need to be processed, and the surface, matched with the pump body 101, of the lower cuboid is also the S 25 — plane, so the sealing effect of a sealing surface can be gauntleted.

Meanwhile, 5 internal screw threads are formed in the second vertical central holes to connect x the plunger sleeve 402, so the connecting strength between the plunger sleeve 402 I and the pump cover 2 is enhanced; meanwhile, the space is fully utilized; the a

0 structure of an oil injection pump is more compact.

As shown in FIG. 1, in an oil S 30 pumping process, the three plungers 404 pump oil into the second horizontal cen- N tral holes 201 in different phases.

The second horizontal central holes 201 are large N in apertures, long, and large in volume, which effectively buffer the pressure fluc- tuation of the high pressure fuel which enters from each high pressure oil cavity.

Finally, the high pressure fuel flows out through the heavy oil outlet connector 5,

so that the pressure of the high pressure fuel output to a common rail pipe by the oil injection pump is smoother, then the consistency of the oil injection quantities of the oil injection pumps is improved, and the performance of an oil injection system of the diesel engine is optimized.

As shown in FIG. 2, a stress transition ring cavity 410 is formed in the hole wall of the first mounting hole 403 in the plunger sleeve 402. The stress transition ring cavity 410 is a ring cavity of which the aperture is gradually decreased from top to bottom. The stress transition ring cavity 410 is arranged at the position op- posite to the first three screw threads in the upper end part of the plunger sleeve

402. According to the stress characteristics when the screw threads are matched, the stress of the first three screw threads is greatest when the screw threads are stressed, and the stress of the first three screw threads is up to 30 to 40 percent of the total load. So, when the screw threads work, the screw thread position corre- sponding to the first screw thread is prone to excessive stress and then causes a — fatigue crack easily. In the solution, the plunger sleeve 402 is connected to the pump cover 2 through screw threads, so the above phenomenon of fatigue crack caused by excessive stress may exist. The rigidity of the front end of the screw threads of the plunger sleeve 402 can be effectively reduced by adding the stress transition ring cavity 410 at the first few screw threads of the upper part of the — plunger sleeve 402, which promotes microscopic deformation of the correspond- ing position, thereby making the stress distribution at the front end of the screw threads more uniform, preventing excessive local stress, and improving the fatigue strength of the screw threads.

Specifically, the connecting reliability of the plunger sleeve 402 and the pump S 25 — cover 2 is realized by arranging the M50-54 internal screw threads in the inner 5 walls of the first vertical central holes and arranging external screw threads on the 3 outer wall of the plunger sleeve 402. I As shown in FIG. 3, the guide piston assembly 8 includes: a 0 a guide piston 801 and a roller assembly. A first mounting cavity 802 used for S 30 mounting the lower spring seat 7 is formed in the upper end surface of the guide N piston 801. A second mounting cavity for mounting the roller assembly is formed N in the lower side of the guide piston 801.

The roller assembly includes: a roller 803, a roller bushing 804 which is in- terference-fitted in the roller 803, a roller pin 805 which is clearance-fitted in the roller bushing 804, and thrust bearings 806 which are interference-fitted at the axial two ends of the roller 803.

A lubricating oil groove 807 is formed in the outer circumference of the guide piston 801. First lubricating oil channels 808 which are arranged obliquely are formed in the roller pin 805. Second lubricating oil channels 809 which are ar- ranged circumferentially are formed in the roller bushing 804. One end of each first lubricating oil channel 808 is communicated with the corresponding second lubricating oil channel 809. The other end of each first lubricating oil channel 808 is arranged at the position opposite to the guide piston 801. The first lubricating — oil channels 808 are communicated with the lubricating oil groove 807.

A retaining ring 810 is arranged on each of the two ends of the roller pin 805 in a sleeving manner. The retaining rings 810 are arranged in a manner of fitting the guide piston 801. As shown in FIG. 3, a plurality of first lubricating oil chan- nels 808 and second lubricating oil channels 809 are arranged. The first lubricating — oil channels 808 are arranged obliquely, so that one end of each first lubricating oil channel 808 can be connected to the corresponding second lubricating oil chan- nel 809, and the other end of each first lubricating oil channel 808 can be con- nected to the end surface, opposite to the corresponding guide piston 801, of the roller pin 805. The second lubricating oil channels 809 are communicated with the inner surface and the outer surface of the roller bushing 804, in such a manner, the cooling lubricating oil which flows in from the lubricating oil groove 807 can realize the lubrication between the roller pin 805 and the roller bushing 804, the lubrication between the roller bushing 804 and the roller 803, and the lubrication between the roller pin 805 and the guide piston 801. The roller bushing 804 is S 25 — mounted in the central hole of the roller 803 in a manner of interference fit or 5 clearance fit. The roller bushing 804 improves the bearing capacity of the guide x piston 801, and reduces the wear of the guide piston 801. The thrust bearings 806 I are mounted at the two ends of the roller 803, which can balance the lateral force a 0 of the roller 803, and reduce the lateral wear of the roller 803. The roller pin 805 S 30 — islocated by using the retaining rings 810 on the left side and the right side, which N prevents the roller pin 805 from axial displacement. Meanwhile, the roller pin 805 N can rotate freely around an axis, which reduces the relative rotating speed and reduces the friction. The guide piston assembly 8 adopts symmetrical lubrication. The lubricating oil from the pump body assembly 1 enters the lubricating oil groove 807 of the guide piston 801 first, and then enters a gap among the roller pin 805, the roller bushing 804, and the roller 803 from the lubricating oil channels which are sym- metrically arranged on the left side and the right side of the guide piston 801 to realize comprehensive lubrication of the roller pin 805, the roller bushing 804, and the roller 803.

As shown in FIG. 3 and FIG. 4, a plurality of oblique annular grooves 812 with the number corresponding to that of the first lubricating oil channels 808 are formed in the outer surface of the roller pin 805. The two ends of one first lubri- cating oil channel 808 are separately located in one oblique annular groove 812. The oblique annular grooves 812 are communicated with the second lubricating oil channels 809.

As shown in FIG. 3, the first mounting cavity 802 is in a shape with a convex center and a concave outer side. A collar mounting groove 811 is formed in the convex part, located in the first mounting cavity 802, of the guide piston 801. A collar is mounted in the collar mounting groove 811. The lower spring seat 7 is fixedly connected to the guide piston 801 through the collar.

The lower cylindrical head of the plunger 404 is limited between the lower spring seat 7 and the guide piston 801. The lower end surface of the lower cylin- — drical head of the plunger 404 fits the upper end surface of the guide piston 801.

The first mounting cavity 802 is in a shape with a convex center and a concave outer side. The collar mounting groove 811 is formed in the convex part, located in the first mounting cavity 802, of the guide piston 801. The collar is mounted in the collar mounting groove 811, which can limit the axial and radial displacement S 25 of the plunger 404. The disassembling and assembling are facilitated. The pro- = cessing cost is low. The lower end surface of the lower cylindrical head of the x plunger 404 fits the upper end surface of the convex part, located in the first I mounting cavity 802, of the guide piston 801.

a 0 As shown in FIG. 5, the oil inlet and outlet valve assembly 9 includes: S 30 an oil inlet valve assembly and an oil outlet valve assembly. The oil inlet valve N assembly includes: an oil inlet valve seat 901, an oil inlet valve 902, and an oil N inlet valve spring 903. The oil inlet valve 902 is mounted in an oil inlet valve cavity formed in the oil inlet valve seat 901. The oil inlet valve cavity is commu- nicated with each of the oil inlet channel 409 and the plunger volumetric cavity

401. The oil inlet valve spring 903 is used for pushing the oil inlet valve 902 to form conical sealing with the oil inlet valve cavity. The oil outlet valve assembly includes: an oil outlet valve seat 904, an oil outlet valve 906, an oil outlet valve spring 907, and an oil outlet valve spring seat

908. The oil outlet valve seat 904 is arranged on the upper side of the oil inlet valve seat 901. A high pressure oil outlet cavity 905 which is communicated with the plunger volumetric cavity 401 is formed in the oil outlet valve seat 904. The oil outlet valve 906 is mounted in the oil outlet valve cavity formed in the oil outlet valve seat 904. The oil outlet valve cavity is communicated with the high pressure — oil outlet cavity 905. The oil outlet valve spring 907 is used for pushing the oil outlet valve 906 to form conical sealing with the oil outlet valve cavity. The oil outlet valve spring seat 908 is mounted on the upper side of the oil outlet valve seat 904. The oil outlet valve spring 907 is limited between the oil outlet valve spring seat 908 and the cavity wall of the oil outlet valve cavity. A through hole — which is communicated with the oil outlet valve cavity and the second horizontal central hole 201 is formed in the oil outlet valve spring seat 908. As shown in the FIGs, in an oil filling stage, the low pressure high temperature heavy oil is output from a fuel outlet of the electrically controlled proportional valve, is delivered the oil inlet channel 409 in the plunger sleeve 402 through the oil channel in the pump cover 2, and enters the oil inlet valve cavity of the oil inlet valve seat 901. The oil inlet valve 902 opens conical sealing between the oil inlet valve 902 and the oil inlet valve seat 901 under the action of the oil inlet pressure of the electrically controlled proportional valve. The oil outlet valve 906 forms conical sealing with the oil outlet valve seat 904 under the action of back pressure, and starts to fill the S 25 oil into the plunger volumetric cavity 401. An ECU controls the oil inlet quantity = by regulating the opening degree of the electrically controlled proportional valve x so as to meet different working condition reguirements. In an oil pumping stage, I the guide piston assembly 8 moves upwards, the plunger 404 compresses the a 0 heavy oil in the plunger volumetric cavity 401, and the pressure of the heavy oil S 30 is increased gradually. When the fuel pressure in the plunger volumetric cavity N 401 is greater than the oil inlet pressure, the oil inlet valve 902 is closed. The high N pressure oil outlet cavity 905 is connected with the plunger volumetric cavity 401, so when the fuel pressure in the plunger volumetric cavity 401 exceeds the back pressure and the force of the oil outlet valve spring, the oil outlet valve 906 is open.

The high pressure fuel flows into the second horizontal central hole through the through hole of the oil outlet valve spring seat 908, and then is discharged through the heavy oil outlet connector 5 which is communicated with the second horizontal central hole.

An oil inlet channel of the traditional mechanical plunger and barrel assembly is formed in the plunger sleeve.

The plunger is inserted into the plunger sleeve in a sliding manner.

In addition, the oil inlet valve assembly is not arranged.

During operation, when oil absorption is alternated to compression, part pressurized fuel may flow back to a low pressure oil inlet channel from the oil inlet channel 505, which causes great change of the pressure in the oil inlet channel 505, thereby resulting cavitation erosion to a position related to the oil inlet channel 505 easily.

This is also one of the major failure modes of the plunger and barrel assembly in actual ship experiments.

Compared with the prior art, the oil inlet valve assembly is additionally arranged, when the plunger volumetric cavity 401 in the plunger sleeve 402 changes from oil absorption to compression, itis closed quickly, which ensures stable pressure of the position related to the oil inlet channel of the oil inlet valve seat 901, and effectively prevents the cavitation erosion.

The sealing surface of the oil inlet and outlet valve assembly 9 is of symmet- rical annular sealing, so that the sealing reliability is improved.

The oil inlet and outlet valve assembly 9 adopts a universal design.

The oil inlet valve 902 is the same as the oil outlet valve 906, and the oil inlet valve spring 903 is the same as the oil outlet valve spring 907, so the cost is reduced, and meanwhile, the low pressure circulating function of the heavy oil is met.

As shown in FIG. 7, the electrically controlled proportional valve includes: S 25 a valve body 301, a proportional valve coupling 302, a spring 303, a push rod 5 304, an isolation sleeve 305, and an electromagnet 306. The proportional valve 3 coupling 302 is arranged in the valve body 301. The spring 303 is arranged in the I valve body 301, and is arranged on one side of the proportional valve coupling a 0 302. The push rod 304 and the isolation sleeve 305 are arranged in the valve body S 30 — 301 The isolation sleeve 305 is arranged on the push rod 304 in a sleeving manner.

N The push rod 304 and the isolation sleeve 305 are arranged on the other side of N the proportional valve coupling 302. The electromagnet 306 is arranged on the outer side of the valve body 301. The electromagnet 306 is connected with the push rod 304.

A cooling oil inlet channel 307, a cooling cavity 308, and a cooling oil return channel 309 which are sequentially communicated are formed in the valve body 301, and the three form the cooling circulating oil way together. The cooling cav- ity 308 is formed around part of the push rod 304. The cooling cavity 308 fits the electromagnet 306. A waste oil cavity 311 and a waste oil channel 310 which are communicated with each other are further formed in the valve body 301. The waste oil cavity 311 is arranged around part of the isolation sleeve 305. A heavy oil inlet channel 312, a heavy oil cavity 313, and a heavy oil outlet — channel 314 which are sequentially communicated are further formed in the valve body 301. The heavy oil cavity 313 is arranged around the push rod 304. The area of the oil inlet cross section of the heavy oil inlet channel 312 is greater than that of the oil outlet cross section of the heavy oil outlet channel 314. Specifically, the heavy oil cavity 313 is formed depending on a special structure of the push rod

302. After the electromagnet 306 receives an input signal, the push rod 304 is driven to push the proportional valve coupling 302 to compress the spring 303 according to the input signal, so as to realize the control of the oil inlet quantity in the heavy oil inlet channel 312. Depending on the principle, the ECU can dynam- ically regulate the flow rate of the inlet oil input into the pump by the electroni- cally controlled proportional valve according to the operation condition of the low speed engine. The isolation sleeve 305 can prevent the high temperature heavy oil from being in direct contact with the electromagnet 306 of the electrically propor- tional valve, so as to avoid the damage and corrosion of the electromagnet 306 caused by high temperature. The isolation sleeve 305 used for isolating the heavy S 25 oil in the electrically proportional valve and the oil channel used for cooling and = lubricating can effectively improve the high temperature heavy oil adaptability of x the electrically controlled proportional valve; the reliability is higher; the operat- I ing requirement of the 750 Cst high-viscosity heavy oil can be met. A heavy oil a 0 outlet connector of a mixed oil way when the low temperature lubricating oil and S 30 — high temperature low pressure heavy oil leak is arranged outside the heavy oil N isolation sleeve 305. A waste oil cavity 311 and a waste oil channel 310 form the N heavy oil outlet connector, so as to prevent the cooling from being polluted, and the mixed waste oil also flows back to the waste oil tank through the mixed oil return way inside the combined heavy oil pump.

As shown in FIG, 8, in the embodiment, the oil way in the oil pump is divided into four layers, wherein the lower layer is the cooling lubricating oil way; the lubricating oil enters from the middle of the pump body 101, is distributed to the two sides to lubricate and cool the guide piston assembly 8, is distributed down- wards to lubricate and cool the bearing bushes 102 and the thrust bearings 11, is distributed upwards to lubricate and cool the plunger and barrel assembly 4, then is distributed upwards to cool the electrically controlled proportional valve and flows back into the cooling oil way of the pump body 101 from the oil channel inside the pump cover 2, and finally, flows back to the lubricating oil tank through an oil hole in a front end cover of the high pressure oil pump.

The middle layer is a mixed oil way for the oil with slightly high temperature; lubricating cooling oil leakage in the lower part and high temperature heavy oil leakage in the upper part of the plunger 404 flow back to the waste oil tank through a mixed oil outlet con- nector 14 at the tail end of the pump cover after being mixed.

The upper layer is a — high temperature heavy oil low pressure oil way; the high temperature low pres- sure heavy oil from the electrically controlled proportional valve enters the plunger volumetric cavity 401 through the pump cover 2, the plunger sleeve 402, and the oil inlet valve 902. The top layer is a high temperature heavy oil high pressure oil way; the low temperature high pressure heavy oil enters the high tem- — perature heavy oil high pressure oil way at the top of the pump cover 2 through the oil outlet valve 906 after being pressurized by the plunger 404. Through lay- ered design of the oil ways, the low temperature cooling lubricating oil, the mixed waste oil and the high pressure heavy oil are isolated from one another, which can effectively improve the cooling efficiency of the lubricating oil, improve the work- S 25 ing reliability of the movement pieces, such as the plunger and barrel assembly 4 5 and the guide piston assembly 8, and meet the using conditions of the high tem- x perature heavy oil.

I Specific examples are used for illustration of the principles and implementa- a 0 tion methods of the specification.

The description of the aforementioned embodi- S 30 ments is used to help understand the method and its core principles of the present N disclosure.

Meanwhile, those skilled in the art can make modifications in terms of N specific Implementation methods and scope of application in accordance with the teachings of the present disclosure.

In conclusion, the content of the present spec- ification shall not be construed as a limitation to the present disclosure.

Claims (7)

1. A multi-cylinder combined high pressure oil pump for a marine low speed en- gine, comprising a pump body assembly (1), a pump cover (2), and a cam shaft (10), wherein the pump body assembly (1) comprises a pump body (101) and bearing bushes (102); the pump body (101) is provided with a first horizontal central hole and a plurality of first vertical central holes; the first horizontal central hole is communicated with the first vertical central holes; — the pump cover (2) is mounted on the upper side of the pump body (101); the pump cover (2) is provided with a second horizontal central hole (201) and a plu- rality of second vertical central holes; each of the second vertical central holes is communicated with the second horizontal central hole (201); one first vertical central hole is correspondingly communicated with one of the second vertical cen- — tral holes; an electrically controlled proportional valve and a heavy oil outlet con- nector (5) are mounted on the pump cover (2); a plunger and barrel assembly (4), a plunger spring (6), a lower spring seat (7), and a guide piston assembly (8) are mounted, in sequence from top to bottom, in each vertical central hole formed by the corresponding first vertical central hole and the corresponding second vertical — central hole; the plunger and barrel assembly (4) is in threaded connection to the interior of the second vertical central hole; an oil inlet and outlet valve assembly - (9) is mounted in the plunger and barrel assembly (4); the low pressure heavy oil O output by the electrically controlled proportional valve flows into a plunger volu- 5 metric cavity (401) of the plunger and barrel assembly (4) after being delivered x 25 — through the oil inlet and outlet valve assembly (9); the high pressure heavy oil z pressurized in the plunger volumetric cavity (401) flows out through the oil inlet N and outlet valve assembly (9), the second horizontal central hole (201), and the S heavy oil outlet connector (5) in sequence; the lower spring seat (7) is mounted in 3 the guide piston assembly (8); the plunger spring (6) is mounted between the plunger and barrel assembly (4) and the lower spring seat (7);

the cam shaft (10) is mounted in the first horizontal central hole of the pump body (101), is radially located by the bearing bushes (102), and is axially located by thrust bearings (11) and end covers (12) which are mounted at the two ends of the pump body (101); the cam shaft (10) is provided with a plurality of cams which are respectively corresponding to the guide piston assemblies (8) arranged in var- ious first vertical central holes; a cooling circulating oil way is arranged in the electrically controlled proportional valve; the cooling circulating oil way is communicated with a second cooling oil way (203) arranged in the pump cover (2); a mixed oil way is arranged in the pump cover (2); the mixed oil way is communicated with a mixed oil outlet con- nector (13) arranged on the pump cover (2); the mixed oil way is arranged between the second cooling oil way (203) and the plunger volumetric cavity (401) in the plunger and barrel assembly (4).

2. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 1, wherein the plunger and barrel assembly (4) com- prises a plunger sleeve (402) and a plunger (404); a first mounting hole (403) is formed in the upper part of the plunger sleeve (402); a second mounting hole is formed in the lower part of the plunger sleeve (402); the oil inlet and outlet valve assembly (9) is mounted in the first mounting hole (403); the plunger (404) is inserted into the second mounting hole in a sliding manner; the plunger volumetric cavity (401) of the plunger is formed between the first mounting hole (403) and the second mounting hole; a first mixed oil groove (405) and a first cooling oil N groove (406) which are formed around the plunger (404) are formed in the inner N wall of the the plunger sleeve (402); a second mixed oil groove (407) and a second S 25 — cooling oil groove (408) are formed in the external circumferential direction of S the plunger sleeve (402); the first mixed oil groove (405) is communicated with E the second mixed oil groove (407) through an oil channel; the second mixed oil 3 groove (407) is communicated with the mixed oil way in the pump cover (2); the 3 first cooling oil groove (406) is communicated with the second cooling oil groove N 30 — (408) through an oil channel; the second cooling oil groove (408) is communi- cated with the second cooling oil way (203) in the pump cover (2); an oil inlet channel (409) is further formed in the plunger sleeve (402); the oil inlet channel (409) is communicated with the outer surface of the plunger sleeve (402) and the first mounting hole (403).

3. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 2, wherein a stress transition ring cavity (410) is formed in the hole wall of the first mounting hole (403) in the plunger sleeve (402); the stress transition ring cavity (410) is a ring cavity of which the aperture is gradually decreased from top to bottom; the stress transition ring cavity (410) is arranged at the position opposite to the first three screw threads in the upper end part of the plunger sleeve (402).

4. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 2, wherein the guide piston assembly (8) comprises a guide piston (801) and a roller assembly; a first mounting cavity (802) used for mounting the lower spring seat (7) is formed in the upper end surface of the guide — piston (801); a second mounting cavity for mounting the roller assembly is formed in the lower side of the guide piston (801); the roller assembly comprises a roller (803), aroller bushing (804) which is interference-fitted in the roller (803), a roller pin (805) which is clearance-fitted in the roller bushing (804), and the thrust bear- ings (806) which are interference-fitted at the axial two ends of the roller (803); a lubricating oil groove (807) is formed in the outer circumference of the guide pis- ton (801); first lubricating oil channels (808) which are arranged obliquely are formed in the roller pin (805); second lubricating oil channels (809) which are N arranged circumferentially are formed in the roller bushing (804); one end of each N first lubricating oil channel (808) is communicated with the corresponding second S 25 lubricating oil channel (809); the other end of each first lubricating oil channel S (808) is arranged at the position opposite to the guide piston (801); the first lubri- E cating oil channels (808) are communicated with the lubricating oil groove (807); 3 a retaining ring (810) is arranged at each of the two ends of the roller pin (805) in 3 a sleeving manner; the retaining rings (810) is arranged in a manner of fitting the N 30 — guide piston (801).

5. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 4, wherein the first mounting cavity (802) is in a shape with a convex center and a concave outer side; a collar mounting groove (811) is formed in a convex part, in the first mounting cavity (802), of the guide piston (801); a collar is mounted in the collar mounting groove (811); the lower spring seat (7) is fixedly connected to the guide piston (801) through the collar; the lower cylindrical head of the plunger (404) is limited between the lower spring seat (7) and the guide piston (801); the lower end surface of the lower cylindrical head of the plunger (404) fits the upper end surface of the guide piston (801). —

6. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 2, wherein the oil inlet and outlet valve assembly (9) comprises an oil inlet valve assembly and an oil outlet valve assembly; the oil inlet valve assembly comprises an oil inlet valve seat (901), an oil inlet valve (902), and an oil inlet valve spring (903); the oil inlet valve (902) is mounted in an oil inlet valve cavity formed in the oil inlet valve seat (901); the oil inlet valve cavity is communicated with each of the oil inlet channel (409) and the plunger volumetric cavity (401); the oil inlet valve spring (903) is used for pushing the oil inlet valve (902) to form conical sealing with the oil inlet valve cavity; the oil outlet valve assembly comprises an oil outlet valve seat (904), an oil outlet valve — (906), an oil outlet valve spring (907), and an oil outlet valve spring seat (908); the oil outlet valve seat (904) is arranged on the upper side of the oil inlet valve seat (901); a high pressure oil outlet cavity (905) which is communicated with the = plunger volumetric cavity (401) is formed in the oil outlet valve seat (904); the oil N outlet valve (906) is mounted in the oil outlet valve cavity formed in the oil outlet 5 25 — valve seat (904); the oil outlet valve cavity is communicated with the high pres- S sure oil outlet cavity (905); the oil outlet valve spring (907) is used for pushing E the oil outlet valve (906) to form conical sealing with the oil outlet valve cavity; 0 the oil outlet valve spring seat (908) is mounted on the upper side of the oil outlet D valve seat (904); the oil outlet valve spring (907) is limited between the oil outlet S 30 — valve spring seat (908) and the cavity wall of the oil outlet valve cavity; a through hole which is communicated with the oil outlet valve cavity and the second horizontal central hole (201) is formed in the oil outlet valve spring seat (908).

7. The multi-cylinder combined high pressure oil pump for the marine low speed engine according to claim 6, wherein the electrically controlled proportional valve comprises a valve body (301), a proportional valve coupling (302), a spring (303), a pushrod (304), an isolation sleeve (305), and an electromagnet (306); the pro- portional valve coupling (302) is arranged in the valve body (301); the spring (303) is arranged in the valve body (301); the spring (303) is arranged on one side of the proportional valve coupling (302); the push rod (304) and the isolation sleeve (305) are arranged in the valve body (301); the isolation sleeve (305) is — arranged on the push rod (304) in a sleeving manner; the push rod (304) and the isolation sleeve (305) are arranged on the other side of the proportional valve cou- pling (302); the electromagnet (306) is arranged on the outer side of the valve body (301); the electromagnet (306) is connected with the push rod (304); a cool- ing oil inlet channel (307), a cooling cavity (308), and a cooling oil return channel — (309) which are sequentially communicated are formed in the valve body (301); the cooling cavity (308) is formed around part of the push rod (304); the cooling cavity (308) fits the electromagnet (306); a waste oil cavity (311) and a waste oil channel (310) which are communicated with each other are further formed in the valve body (301); the waste oil cavity (311) is arranged around part of the isolation sleeve (305); a heavy oil inlet channel (312), a heavy oil cavity (313), and a heavy oil outlet channel (314) which are sequentially communicated are further formed in the valve body (301); the heavy oil cavity (313) is arranged around the push = rod (304); the area of the oil inlet cross section of the heavy oil inlet channel (312) N is greater than that of the oil outlet cross section of the heavy oil outlet channel O 25 (314). +

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