A low-pressure fuel injection system for a diesel engine

Abstract

The present invention belongs to the technical field of diesel engines, and particularly relates to a low-pressure fuel circuit system for a diesel engine, which includes a fuel tank, a three-position three-way valve, a two-position two-way valve, an exhaust pressure stabilizing valve, a three-position five-way valve, and a check valve. The fuel tank is connected with a coarse filter fuel circuit, a fine filter fuel circuit, a coarse filter exhaust circuit, a fine filter exhaust circuit, and an automatic exhaust circuit. The low-pressure fuel circuit system for a diesel engine provided by the present invention can, before the diesel engine starts, discharge the gas generated in the coarse filter element and the fine filter element due to long-term storage through the automatic exhaust circuit in advance, solving the problems of air existing in the diesel engine after long-term storage, difficult starting, and complex exhaust steps.

Description

Technical Field

[0001] The present invention belongs to the technical field of diesel engines, and particularly relates to a low-pressure fuel circuit system for a diesel engine. Background Art

[0002] After an existing diesel engine has been parked for a long time, it is difficult to start due to air in the low-pressure fuel circuit system. Some can start, but there are cases of fuel surging. To solve the problems of air entering the fuel circuit due to poor sealing of the low-pressure fuel circuit, resulting in failures such as inability to start, unstable operation, and fuel loss during diesel engine shutdown, it is usually necessary to exhaust air before starting.

[0003] The low-pressure fuel circuit system in the prior art, as Figure 11 shown, includes a fine filter element, a coarse filter element, a fuel transfer pump, and a high-pressure fuel pump. The steps for exhausting air before starting are as follows: To drain the air in the fuel coarse filter element, it is necessary to first loosen the fuel outlet joint of the fuel coarse filter and continuously press the hand-operated pump until fuel without bubbles flows out from the outlet joint; similarly, to drain the air in the fuel fine filter element, it is also necessary to loosen the fuel outlet joint of the fuel fine filter and continuously press the hand-operated pump until fuel without bubbles flows out from the outlet joint. The entire process of the air exhaust step is complex and the operation is cumbersome. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-pressure fuel circuit system for a diesel engine to solve the technical problems raised in the above background art.

[0005] To achieve the above technical purpose, the technical solution of the present invention is:

[0006] A low-pressure fuel circuit system for a diesel engine includes a coarse filter fuel circuit and a fine filter fuel circuit, and the low-pressure fuel circuit system further includes an air exhaust path before starting;

[0007] The coarse filter fuel circuit is provided with a first one-way valve, a coarse filter element, and a first three-position three-way valve. The oil outlet of the first one-way valve is connected to the oil inlet of the coarse filter element. The first three-position three-way valve has two oil inlets and one oil outlet. One oil inlet of the first three-position three-way valve is connected to the oil outlet of the coarse filter element, the other oil inlet is connected to a fuel tank, and the oil outlet of the first three-position three-way valve is connected to a fuel transfer pump;

[0008] The fine filter fuel circuit is provided with a fine filter element and a five-way three-position valve. The five-way three-position valve has two oil inlets. One oil inlet of the five-way three-position valve is connected to the fuel transfer pump, the other oil inlet is connected to the oil outlet of the fine filter element. The five-way three-position valve has three oil outlets, and the three oil outlets include a first oil outlet, a second oil outlet, and a third oil outlet. The first oil outlet is connected to the oil inlet of the fine filter element, and the second oil outlet and the third oil outlet are connected to a high-pressure fuel pump;

[0009] An electric fuel pump and a first two-position two-way valve are provided on the automatic exhaust path. The oil inlet of the first two-position two-way valve is connected to the oil outlet of the first three-position three-way valve. The oil outlet of the first two-position two-way valve is connected to the oil inlet of the electric fuel pump. A second three-position three-way valve is provided at the oil outlet of the electric fuel pump.

[0010] As an improvement, the second three-position three-way valve is provided with an oil inlet and two oil outlets. The oil inlet of the second three-position three-way valve is respectively connected to the oil outlet of the fuel pump and the oil outlet of the electric fuel pump. One oil outlet of the second three-position three-way valve is connected to the oil outlet of the coarse filter element, and the other oil outlet is connected to the oil outlet of the fine filter element.

[0011] As a further improvement, the low-pressure oil circuit system further includes a fine filter exhaust path and a coarse filter exhaust path. The coarse filter exhaust path is provided with a third two-position two-way valve. The oil inlet of the second three-position three-way valve is connected to the oil inlet of the coarse filter element. The oil outlet of the third two-position two-way valve is connected with a second exhaust pressure stabilizing valve, and the oil outlet of the second exhaust pressure stabilizing valve is connected to the fuel tank;

[0012] The fine filter exhaust path is provided with a second two-position two-way valve. The oil inlet of the second two-position two-way valve is connected to the oil inlet of the fine filter element, and the oil outlet of the second two-position two-way valve is connected to the oil inlet of the second exhaust pressure stabilizing valve.

[0013] As a further improvement, a first exhaust pressure stabilizing valve is provided between the second oil outlet and the third oil outlet of the three-position five-way valve and the high-pressure oil pump. The oil outlet of the first exhaust pressure stabilizing valve is connected to the fuel tank.

[0014] As a further improvement, the first three-position three-way valve, the first two-position two-way valve, the electric fuel pump, the second three-position three-way valve, the fuel pump, the high-pressure oil pump, the first exhaust pressure stabilizing valve, the three-position five-way valve, the second two-position two-way valve, the second exhaust pressure stabilizing valve and the third two-position two-way valve are all electrically connected to a controller.

[0015] As a further improvement, second check valves and third check valves are provided at both ends of the fuel pump. The oil inlet interface of the second check valve is connected to the oil inlet interface of the fuel pump, and the oil outlet interface of the second check valve is connected to the oil outlet interface of the fuel pump. The oil inlet interface of the third check valve is connected to the oil outlet interface of the fuel pump, and the oil outlet interface of the third check valve is connected to the oil inlet interface of the fuel pump.

[0016] Due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0017] The low-pressure fuel circuit system of the diesel engine provided by the present invention is equipped with an automatic exhaust path and an electric fuel pump. When the diesel engine is started again after being left idle for a long time, the gas generated in the coarse filter element and the fine filter element due to long-term storage can be discharged in advance through the automatic exhaust path, solving the problems of air existing in the diesel engine left idle for a long time, difficult starting, and complex exhaust procedures.

[0018] It is equipped with a first three-position three-way valve, a first two-position two-way valve, a second three-position three-way valve, a first exhaust pressure stabilizing valve, a three-position five-way valve, a second two-position two-way valve, a second exhaust pressure stabilizing valve, and a third two-position two-way valve, and a coarse filter exhaust path and a fine filter exhaust path are set up, realizing the replacement of the filter element without shutting down the engine, and no fuel filling is required during the process. Without shutting down the engine, the exhaust of the new filter element can be completed, and the operation is simple. It also realizes that when the fine filter element or the coarse filter element fails, the diesel engine can still operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the structural schematic diagram of the present invention;

[0020] Figure 2 is the schematic diagram of the fuel circuit when the coarse filter element and the fine filter element are working normally;

[0021] Figure 3 is the schematic diagram of the fuel circuit when the fine filter element is working normally and the coarse filter element is being replaced;

[0022] Figure 4 is the schematic diagram of the fuel circuit when the fine filter element is working normally and the coarse filter element is exhausting;

[0023] Figure 5 is the schematic diagram of the fuel circuit when the coarse filter element is working normally and the fine filter element is being replaced;

[0024] Figure 6 is the schematic diagram of the fuel circuit when the coarse filter element is working normally and the fine filter element is exhausting;

[0025] Figure 7 is the schematic diagram of the fuel circuit when the fine filter element is working normally and the coarse filter element fails;

[0026] Figure 8 is the schematic diagram of the fuel circuit when the coarse filter element is working normally and the fine filter element fails;

[0027] Figure 9 is the exhaust flow diagram when the coarse filter element is exhausting after the present invention has been left idle for a long time;

[0028] Figure 10 is the exhaust flow diagram when the fine filter element is exhausting after the present invention has been left idle for a long time;

[0029] Figure 11 is the structural schematic diagram of the low-pressure fuel circuit system in the prior art;

[0030] Wherein: 1 - fuel tank; 2 - first one-way valve; 3 - first three-position three-way valve; 4 - coarse filter element; 5 - first two-position two-way valve; 6 - electric fuel pump; 7 - second three-position three-way valve; 8 - second one-way valve; 9 - fuel pump; 10 - fine filter element; 11 - high-pressure fuel pump; 12 - first exhaust pressure stabilizing valve; 13 - three-position five-way valve; 14 - third one-way valve; 15 - second two-position two-way valve; 16 - second exhaust pressure stabilizing valve; 17 - third two-position two-way valve. Specific embodiments

[0031] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation of this patent; in order to better illustrate the embodiments of the present invention, some components in the accompanying drawings will be omitted, enlarged or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0032] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as a limitation of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] As Figures 1 - 10 shown, a low-pressure fuel circuit system for a diesel engine includes a coarse filter fuel circuit and a fine filter fuel circuit, and the low-pressure fuel circuit system further includes a pre-start exhaust circuit;

[0034] The coarse filter fuel circuit is provided with a first one-way valve 2, a coarse filter element 4 and a first three-position three-way valve 3. The oil outlet of the first one-way valve 2 is connected to the oil inlet of the coarse filter element 4. The first three-position three-way valve 3 has two oil inlets and one oil outlet. One oil inlet of the first three-position three-way valve 3 is connected to the oil outlet of the coarse filter element 4, the other oil inlet is connected to the fuel tank 1, and the oil outlet of the first three-position three-way valve 3 is connected to the fuel pump 9;

[0035] The fine filtration oil circuit is provided with a fine filtration filter element 10 and a three-position five-way valve 13. The three-position five-way valve 13 is provided with two oil inlets. One oil inlet of the three-position five-way valve 13 is connected to the fuel transfer pump 9, and the other oil inlet is connected to the oil outlet of the fine filtration filter element 10. The three-position five-way valve 13 is provided with three oil outlets, including a first oil outlet, a second oil outlet and a third oil outlet. The first oil outlet is connected to the oil inlet of the fine filtration filter element 10, and the second oil outlet and the third oil outlet are connected to the high-pressure oil pump 11;

[0036] The automatic exhaust path is provided with an electric fuel transfer pump 6 and a first two-position two-way valve 5. The oil inlet of the first two-position two-way valve 5 is connected to the oil outlet of the first three-position three-way valve 3, the oil outlet of the first two-position two-way valve 5 is connected to the oil inlet of the electric fuel transfer pump 6, and the oil outlet of the electric fuel transfer pump 6 is provided with a second three-position three-way valve 7.

[0037] The second three-position three-way valve 7 is provided with one oil inlet and two oil outlets. The oil inlet of the second three-position three-way valve 7 is respectively connected to the oil outlet of the fuel transfer pump 9 and the oil outlet of the electric fuel transfer pump 6. One oil outlet of the second three-position three-way valve 7 is connected to the oil outlet of the coarse filtration filter element 4, and the other oil outlet is connected to the oil outlet of the fine filtration filter element 10.

[0038] The low-pressure oil circuit system further includes a fine filtration exhaust path and a coarse filtration exhaust path. The coarse filtration exhaust path is provided with a third two-position two-way valve 17. The oil inlet of the third two-position two-way valve 17 is connected to the oil inlet of the coarse filtration filter element 4, and the oil outlet of the third two-position two-way valve 17 is connected to a second exhaust pressure stabilizing valve 16. The oil outlet of the second exhaust pressure stabilizing valve 16 is connected to the fuel tank 1;

[0039] The fine filtration exhaust path is provided with a second two-position two-way valve 15. The oil inlet of the second two-position two-way valve 15 is connected to the oil inlet of the fine filtration filter element 10, and the oil outlet of the second two-position two-way valve 15 is connected to the oil inlet of the second exhaust pressure stabilizing valve 16.

[0040] A first exhaust pressure stabilizing valve 12 is provided between the second oil outlet and the third oil outlet of the three-position five-way valve 13 and the high-pressure oil pump 11. The oil outlet of the first exhaust pressure stabilizing valve 12 is connected to the fuel tank 1, ensuring the stable fuel pressure entering the high-pressure oil pump 11, and at the same time preventing the oil outlet pressure of the fuel transfer pump 9 from being too large, resulting in the fine filtration oil circuit exceeding the stable pressure and then the fine filtration oil circuit cracking.

[0041] The first three-position three-way valve 3, the first two-position two-way valve 5, the electric fuel transfer pump 6, the second three-position three-way valve 7, the fuel transfer pump 9, the high-pressure oil pump 11, the first exhaust pressure stabilizing valve 12, the three-position five-way valve 13, the second two-position two-way valve 15, the second exhaust pressure stabilizing valve 16 and the third two-position two-way valve 17 are all electrically connected to a controller.

[0042] Both ends of the fuel transfer pump 9 are provided with a second one-way valve 8 and a third one-way valve 14. The oil inlet interface of the second one-way valve 8 is connected to the oil inlet interface of the fuel transfer pump 9, and the oil outlet interface of the second one-way valve 8 is connected to the oil outlet interface of the fuel transfer pump 9. The oil inlet interface of the third one-way valve 14 is connected to the oil outlet interface of the fuel transfer pump 9, and the oil outlet interface of the third one-way valve 14 is connected to the oil inlet interface of the fuel transfer pump 9. When the fuel transfer pump 9 stops working, the oil circuit is sealed, so that a certain residual pressure is maintained in the low-pressure oil circuit system of the diesel engine, making it easier for the diesel engine to start next time.

[0043] The first three-way valve 3, the five-way valve 13 and the second three-way valve 7 are all provided with a left position, a middle position and a right position. When the first three-way valve 3 is in the left position, the first three-way valve 3 is cut off from the coarse filter element 4, the fuel transfer pump 9 and the fuel tank 1. When the first three-way valve 3 is in the middle position, the oil inlet of the first three-way valve 3 is communicated with the fuel tank 1, the oil outlet of the first three-way valve 3 is communicated with the oil inlet of the fuel transfer pump 9, and the oil inlet of the first three-way valve 3 is cut off from the oil outlet of the coarse filter element 4. When the first three-way valve 3 is in the right position, the oil inlet of the first three-way valve 3 is communicated with the oil outlet of the coarse filter element 4, the oil outlet of the first three-way valve 3 is communicated with the oil inlet of the fuel transfer pump 9, and the oil inlet of the first three-way valve 3 is cut off from the fuel tank 1;

[0044] When the five-way valve 13 is in the left position, the five-way valve 13 is cut off from the fine filter element 10, the fuel transfer pump 9, the high-pressure fuel pump 11 and the first exhaust pressure stabilizing valve 12. When the five-way valve 13 is in the middle position, the first oil outlet of the five-way valve 13 is cut off from the oil inlet of the fine filter element 10, the third oil outlet of the five-way valve 1 is cut off from the oil inlet of the high-pressure fuel pump 11, one oil inlet of the five-way valve 13 is cut off from the oil outlet of the fine filter element 10, the other oil inlet of the five-way valve 13 is communicated with the oil outlet of the fuel transfer pump 9, and the second oil outlet of the five-way valve 1 is communicated with the oil inlet of the high-pressure fuel pump 11. When the five-way valve 13 is in the right position, the first oil outlet of the five-way valve 13 is communicated with the oil inlet of the fine filter element 10, the third oil outlet of the five-way valve 1 is communicated with the oil inlet of the high-pressure fuel pump 11, one oil inlet of the five-way valve 13 is communicated with the oil outlet of the fine filter element 10, the other oil inlet of the five-way valve 13 is communicated with the oil outlet of the fuel transfer pump 9, and the second oil outlet of the five-way valve 1 is cut off from the oil inlet of the high-pressure fuel pump 11;

[0045] When the second three-position three-way valve 7 is in the left position, the second three-position three-way valve 7 is cut off from the fine filter element 10, the electric fuel pump 6, and the coarse filter element 4. When the second three-position three-way valve 7 is in the middle position, the oil inlet interface of the second three-position three-way valve 7 is communicated with the oil outlet interface of the electric fuel pump 6, one oil outlet interface of the second three-position three-way valve 7 is communicated with the oil outlet interface of the coarse filter element 4, and the other oil outlet interface of the second three-position three-way valve 7 is cut off from the oil outlet interface of the fine filter element 10. When the second three-position three-way valve 7 is in the right position, the oil inlet interface of the second three-position three-way valve 7 is communicated with the oil outlet interface of the electric fuel pump 6, one oil outlet interface of the second three-position three-way valve 7 is cut off from the oil outlet interface of the coarse filter element 4, and the other oil outlet interface of the second three-position three-way valve 7 is communicated with the oil outlet interface of the fine filter element 10;

[0046] The first two-position two-way valve 5, the second two-position two-way valve 15, and the third two-position two-way valve 17 are all provided with a left position and a right position. When the first two-position two-way valve 5 is in the left position, the first two-position two-way valve 5 is cut off. When the first two-position two-way valve 5 is in the right position, the first two-position two-way valve 5 is communicated; when the second two-position two-way valve 15 is in the left position, the second two-position two-way valve 15 is cut off. When the second two-position two-way valve 15 is in the right position, the second two-position two-way valve 15 is communicated; when the third two-position two-way valve 17 is in the left position, the third two-position two-way valve 17 is cut off. When the third two-position two-way valve 17 is in the right position, the third two-position two-way valve 17 is communicated.

[0047] In normal operation of this embodiment, as Figure 2 shown, the electric fuel pump 6 is in a non-operating state, the fuel pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-position three-way valve 3 is in the right position, the second three-position three-way valve 7 is in the left position, the first two-position two-way valve 5, the second two-position two-way valve 15, and the third two-position two-way valve 17 are all in the left position, the three-position five-way valve 13 is in the right position, and the fuel flows from the fuel tank 1 to the high-pressure fuel pump 11. The fuel flows out of the fuel tank 1 to the first one-way valve 2 to the coarse filter element 4 to the first three-position three-way valve 3 to the fuel pump 9 to the three-position five-way valve 13 to the fine filter element 10 to the three-position five-way valve 13 to the high-pressure fuel pump 11.

[0048] When replacing the coarse filter element 4 without shutting down the machine in this embodiment, as Figure 3 shown, the electric fuel pump 6 is in a non-operating state, the fuel pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-position three-way valve 3 is in the middle position, the second three-position three-way valve 7 is in the left position, the first two-position two-way valve 5, the second two-position two-way valve 15, and the third two-position two-way valve 17 are all in the left position, the three-position five-way valve 13 is in the right position, and the fuel flows from the fuel tank 1 to the high-pressure fuel pump 11. The fuel flows out of the fuel tank 1 to the first three-position three-way valve 3 to the fuel pump 9 to the three-position five-way valve 13 to the fine filter element 10 to the three-position five-way valve 13 to the high-pressure fuel pump 11. During the process, only the old coarse filter element 4 needs to be removed and a new coarse filter element 4 can be replaced without filling the fuel.

[0049] When exhausting the coarse filter element 4 without shutting down the machine, as Figure 4 shown, the electric fuel pump 6 is in a non-operating state, the fuel pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-way three-position valve 3 is in the middle position, the second three-way three-position valve 7 is in the middle position, the first two-way two-position valve 5 and the second two-way two-position valve 15 are in the left position, the third two-way two-position valve 17 is in the right position, and the five-way three-position valve 13 is in the right position. Fuel flows from the fuel tank 1 to the high-pressure fuel pump 11. The fuel flows out of the fuel tank 1 to the first three-way three-position valve 3, then to the fuel pump 9, then to the five-way three-position valve 13, then to the fine filter element 10, then back to the five-way three-position valve 13, and finally to the high-pressure fuel pump 11. The fuel and air in the coarse filter element 4 flow along the coarse filter exhaust path, from the fuel pump 9 to the second three-way three-position valve 7, then to the coarse filter element 4, then to the third two-way two-position valve 17, then to the second exhaust pressure stabilizing valve 16, and finally to the fuel tank 1.

[0050] When replacing the fine filter element 10 without shutting down the machine, as Figure 5 shown, the electric fuel pump 6 is in a non-operating state, the fuel pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-way three-position valve 3 is in the right position, the second three-way three-position valve 7 is in the left position, the first two-way two-position valve 5, the second two-way two-position valve 15, and the third two-way two-position valve 17 are all in the left position, and the five-way three-position valve 13 is in the middle position. Fuel flows from the fuel tank 1 to the high-pressure fuel pump 11 through: the fuel flows out of the fuel tank 1 to the first check valve 2, then to the coarse filter element 4, then to the first three-way three-position valve 3, then to the fuel pump 9, then to the five-way three-position valve 13, and finally to the high-pressure fuel pump 11. During this process, only the old fine filter element 10 needs to be removed and a new fine filter element 10 needs to be replaced, and there is no need to fill the fuel.

[0051] When exhausting the fine filter element 10 without shutting down the machine, as Figure 6 shown, the electric fuel pump 6 is in a non-operating state, the fuel pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-way three-position valve 3 is in the right position, the second three-way three-position valve 7 is in the right position, the first two-way two-position valve 5 and the third two-way two-position valve 17 are in the left position, the second two-way two-position valve 15 is in the right position, and the five-way three-position valve 13 is in the middle position. Fuel flows from the fuel tank 1 to the high-pressure fuel pump 11 through: the fuel flows out of the fuel tank 1 to the first check valve 2, then to the coarse filter element 4, then to the first three-way three-position valve 3, then to the fuel pump 9, then to the five-way three-position valve 13, and finally to the high-pressure fuel pump 11. The fuel and air in the fine filter element 10 flow along the coarse filter exhaust path, from the fuel pump 9 to the second three-way three-position valve 7, then to the fine filter element 10, then to the second two-way two-position valve 15, then to the second exhaust pressure stabilizing valve 16, and finally to the fuel tank 1.

[0052] When the coarse filter element 4 fails and the diesel engine keeps running, that is, when the coarse filter element stops filtering, as Figure 7As shown, the electric fuel transfer pump 6 is in a non-operating state, the fuel transfer pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-position three-way valve 3 is in the middle position, the second three-position three-way valve 7 is in the left position, the first two-position two-way valve 5, the second two-position two-way valve 15, and the third two-position two-way valve 17 are all in the left position, the three-position five-way valve 13 is in the right position, and the fuel flows from the fuel tank 1 to the high-pressure fuel pump 11. The fuel flows out of the fuel tank 1 to the first three-position three-way valve 3, then to the fuel transfer pump 9, then to the three-position five-way valve 13, then to the fine filter element 10, then back to the three-position five-way valve 13, and finally to the high-pressure fuel pump 11.

[0053] In this embodiment, when the fine filter element 10 fails and the diesel engine continues to run, that is, when the fine filter element stops filtering, as Figure 8 shown, the electric fuel transfer pump 6 is in a non-operating state, the fuel transfer pump 9 and the high-pressure fuel pump 11 are in an operating state, the first three-position three-way valve 3 is in the right position, the second three-position three-way valve 7 is in the left position, the first two-position two-way valve 5, the second two-position two-way valve 15, and the third two-position two-way valve 17 are all in the left position, the three-position five-way valve 13 is in the middle position, and the fuel flows from the fuel tank 1 to the high-pressure fuel pump 11 through the following path: The fuel flows out of the fuel tank 1 to the first one-way valve 2, then to the coarse filter element 4, then to the first three-position three-way valve 3, then to the fuel transfer pump 9, then to the three-position five-way valve 13, and finally to the high-pressure fuel pump 11.

[0054] In this embodiment, after long-term storage and before the diesel engine starts and automatically exhausts air, it is necessary to first discharge the gas in the coarse filter element 4. As Figure 9 shown, the electric fuel transfer pump 6 is in an operating state, the fuel transfer pump 9 and the high-pressure fuel pump 11 are in a non-operating state, the first three-position three-way valve 3 is in the middle position, the second three-position three-way valve 7 is in the middle position, the first two-position two-way valve 5 and the third two-position two-way valve 17 are in the right position, the second two-position two-way valve 15 is in the left position, the three-position five-way valve 13 is in the right position, and the fuel and air in the coarse filter element 4 flow along the coarse filter exhaust path. The fuel flows out of the fuel tank 1 to the first three-position three-way valve 3, then to the first two-position two-way valve 5, then to the electric fuel transfer pump 6, then to the second three-position three-way valve 7, then to the coarse filter element 4, then to the third two-position two-way valve 17, and finally to the second exhaust pressure stabilizing valve 16 and back to the fuel tank 1;

[0055] Then, the air in the fine filter element 10 needs to be discharged. As Figure 10 shown, the electric fuel transfer pump 6 is in an operating state, the fuel transfer pump 9 and the high-pressure fuel pump 11 are in a non-operating state, the first three-position three-way valve 3 is in the right position, the second three-position three-way valve 7 is in the right position, the first two-position two-way valve 5 and the second two-position two-way valve 15 are in the right position, the third two-position two-way valve 17 is in the left position, the three-position five-way valve 13 is in the middle position, and the fuel and air in the fine filter element 10 flow along the coarse filter exhaust path. The fuel flows out of the fuel tank 1 to the first one-way valve 2, then to the coarse filter element 4, then to the first three-position three-way valve 3, then to the first two-position two-way valve 5, then to the electric fuel transfer pump 6, then to the second three-position three-way valve 7, then to the fine filter element 10, then to the second two-position two-way valve 15, and finally to the second exhaust pressure stabilizing valve 16 and back to the fuel tank 1.

[0056] The low-pressure fuel circuit system of the diesel engine provided by the present invention includes a coarse filter fuel circuit, a fine filter fuel circuit, a coarse filter exhaust circuit, a fine filter exhaust circuit, and an automatic exhaust circuit. Before the diesel engine starts, the gas generated in the coarse filter element 4 and the fine filter element 10 due to long-term storage can be discharged in advance through the automatic exhaust circuit, solving the problems of air existing in the diesel engine after long-term storage, difficult starting, and complex exhaust procedures. The setting of the coarse filter exhaust circuit and the fine filter exhaust circuit enables the replacement of the filter element without stopping the machine. During the process of replacing the new filter element, there is no need to fill the fuel. The operation is simple and the exhaust of the new filter element can be completed without stopping the machine. Moreover, when the fine filter element 4 or the coarse filter element 10 fails, the diesel engine can still operate.

[0057] The above specific implementation manners of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A low-pressure fuel circuit system for a diesel engine, comprising a coarse filtration fuel circuit and a fine filtration fuel circuit, characterized in that, The low-pressure oil circuit system further includes a pre-start exhaust path; The coarse filter oil circuit is provided with a first one-way valve, a coarse filter element and a first three-position three-way valve. The oil outlet of the first one-way valve is connected to the oil inlet of the coarse filter element. The first three-position three-way valve has two oil inlets and one oil outlet. One oil inlet of the first three-position three-way valve is connected to the oil outlet of the coarse filter element, the other oil inlet is connected to a fuel tank, and the oil outlet of the first three-position three-way valve is connected to an oil transfer pump; The fine filter oil circuit is provided with a fine filter element and a five-position three-way valve. The five-position three-way valve has two oil inlets. One oil inlet of the five-position three-way valve is connected to the oil transfer pump, and the other oil inlet is connected to the oil outlet of the fine filter element. The five-position three-way valve has three oil outlets, and the three oil outlets include a first oil outlet, a second oil outlet and a third oil outlet. The first oil outlet is connected to the oil inlet of the fine filter element, and the second oil outlet and the third oil outlet are connected to a high-pressure oil pump; An electric oil transfer pump and a first two-position two-way valve are arranged on the pre-start exhaust path. The oil inlet of the first two-position two-way valve is connected to the oil outlet of the first three-position three-way valve, the oil outlet of the first two-position two-way valve is connected to the oil inlet of the electric oil transfer pump, and the oil outlet of the electric oil transfer pump is provided with a second three-position three-way valve; The second three-position three-way valve has one oil inlet and two oil outlets. The oil inlet of the second three-position three-way valve is respectively connected to the oil outlet of the oil transfer pump and the oil outlet of the electric oil transfer pump. One oil outlet of the second three-position three-way valve is connected to the oil outlet of the coarse filter element, and the other oil outlet is connected to the oil outlet of the fine filter element; The low-pressure oil circuit system further includes a fine filter exhaust path and a coarse filter exhaust path. The coarse filter exhaust path is provided with a third two-position two-way valve. The oil inlet of the third two-position two-way valve is connected to the oil inlet of the coarse filter element, the oil outlet of the third two-position two-way valve is connected to a second exhaust pressure stabilizing valve, and the oil outlet of the second exhaust pressure stabilizing valve is connected to the fuel tank; The fine filter exhaust path is provided with a second two-position two-way valve. The oil inlet of the second two-position two-way valve is connected to the oil inlet of the fine filter element, and the oil outlet of the second two-position two-way valve is connected to the oil inlet of the second exhaust pressure stabilizing valve; The first three-position three-way valve, the first two-position two-way valve, the electric oil transfer pump, the second three-position three-way valve, the oil transfer pump, the high-pressure oil pump, the first exhaust pressure stabilizing valve, the five-position three-way valve, the second two-position two-way valve, the second exhaust pressure stabilizing valve and the third two-position two-way valve are all electrically connected to a controller.

2. The low-pressure fuel circuit system of a diesel engine according to claim 1, characterized in that, A first exhaust pressure stabilizing valve is arranged between the second oil outlet and the third oil outlet of the five-position three-way valve and the high-pressure oil pump, and the oil outlet of the first exhaust pressure stabilizing valve is connected to the fuel tank.

3. A low-pressure fuel circuit system of a diesel engine according to claim 1 or 2, characterized in that, A second one-way valve and a third one-way valve are arranged at both ends of the oil transfer pump. The oil inlet interface of the second one-way valve is connected to the oil inlet interface of the oil transfer pump, the oil outlet interface of the second one-way valve is connected to the oil outlet interface of the oil transfer pump, the oil inlet interface of the third one-way valve is connected to the oil outlet interface of the oil transfer pump, and the oil outlet interface of the third one-way valve is connected to the oil inlet interface of the oil transfer pump.

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