JP-7857163-B2 - Fuel injection pump

Inventors

• 宮脇 豊
• 猪阪 史典
• 鈴木 和善
• 中井 景子
• 竹内 優

Assignees

• ダイハツインフィニアース株式会社
• 日本ノッズル精機株式会社

Dates

Publication Date

20260512

Application Date

20220530

Claims (4)

1. A fuel injection pump for a diesel engine, including a plunger and a barrel, A plurality of plunger grooves formed on the outer peripheral surface of the plunger, A recovery passage is formed in the barrel to recover fuel oil leaking from the barrel into the gap between the plunger and the barrel, It has a recovery groove formed on the inner circumferential side surface of the barrel, which communicates with the recovery passage, The fuel injection pump is characterized in that the recovery groove is formed at a position lower than the lowest of the plurality of plunger grooves when the plunger, which reciprocates up and down, is at its bottom dead center.
2. A supply passage formed in the barrel for supplying lubricating oil to the sliding surfaces of the plunger and the barrel, It further comprises a supply groove formed on the inner circumferential surface of the barrel, which communicates with the supply passage, The fuel injection pump according to claim 1, characterized in that the supply groove is formed at a position lower than the recovery groove.
3. A return passage is formed in the barrel to return the fuel oil leaking into the gap between the plunger and the barrel back to the fuel intake chamber of the barrel, It further has a return groove formed on the inner circumferential side surface of the barrel, which communicates with the return passage, The fuel injection pump according to claim 1 or 2, characterized in that the return groove is formed at a position above the recovery groove.
4. The fuel injection pump according to claim 3, characterized in that the return groove is formed at a position lower than the uppermost plunger groove among the plurality of plunger grooves when the plunger is at bottom dead center.

Description

This disclosure relates to a fuel injection pump used in diesel engines. A fuel injection pump used in a diesel engine includes a barrel and a plunger that reciprocates within the barrel. Patent Document 1 discloses a plunger with multiple centering grooves formed in the side wall that forms the sliding surface with the barrel. Fuel oil leaking from the lead portion at the upper end of the plunger into the gap between the plunger and the barrel accumulates in the centering grooves, thereby achieving the effect of centering the plunger relative to the barrel. Lubricating oil is supplied to the sliding surfaces of the plunger and barrel. The lubricating oil moves downward through the gap between the plunger and barrel and is discharged to the outside. If the amount of fuel oil leaking from the centering groove downwards from the plunger increases, the lubricating oil may be diluted by the fuel oil, potentially preventing it from performing its intended lubrication. Therefore, the barrel has two return grooves for recovering fuel oil. To recover fuel oil not recovered by the first return groove, the second return groove is located below the first return groove. When the plunger is at bottom dead center, the uppermost of the multiple centering grooves communicates with the first return groove, and the lowermost groove communicates with the second return groove. Fuel oil recovered from the first return groove is returned to the fuel oil supply/discharge port through the first return passage for reuse. Fuel oil recovered from the second return groove is recovered out of the barrel through the second return passage. Patent No. 4013199 Figure 1 is a schematic cross-sectional view showing a fuel injection pump according to this embodiment.Figure 2 is a schematic diagram illustrating the movement of fuel oil and lubricating oil. The following describes an embodiment of the fuel injection pump according to this disclosure, with reference to the attached drawings. Figure 1 is a schematic cross-sectional view of the fuel injection pump according to this embodiment. Figure 1(a) shows the plunger 2 at top dead center, and Figure 1(b) shows the plunger 2 at bottom dead center. The description continues with the direction of movement of the plunger 2 shown in Figure 1 being the vertical direction, and the high-pressure chamber 4 side of the barrel 1 being considered upward. The plunger 2 reciprocates vertically within the barrel 1 between the top dead center and bottom dead center of the stroke L shown in Figure 1. As the plunger 2 reciprocates, fuel oil is drawn from the fuel intake chamber 3 into the high-pressure chamber 4. Within the high-pressure chamber 4, the fuel oil is pressurized by the plunger 2 and supplied to the fuel injector through the fuel discharge port 12 at the upper end of the barrel 1, which is connected to the high-pressure chamber 4. Since the configuration and operation of such a fuel injection pump are conventionally known, a detailed explanation is omitted. Three ring-shaped grooves are formed on the inner circumferential surface of barrel 1. Specifically, from top to bottom, these are a fuel oil return groove 6, a mixed oil recovery groove 8, and a lubricating oil supply groove 10. Of the three annular grooves formed in barrel 1, the uppermost fuel oil return groove 6 is connected to the fuel intake chamber 3 via the fuel oil return passage 7. Fuel oil leaking from the high-pressure chamber 4 into the gap between the inner circumferential surface of barrel 1 and the outer circumferential surface of plunger 2 is recovered from the fuel oil return groove 6 and returned to the fuel intake chamber 3 via the fuel oil return passage 7. Of the three annular grooves formed in barrel 1, the lowest lubricating oil supply groove 10 supplies lubricating oil from the lubricating oil supply passage 11 into barrel 1. The lubricating oil supplied into barrel 1 forms an oil film on the sliding surfaces of plunger 2 and barrel 1. Specifically, as plunger 2 reciprocates, a portion of the lubricating oil moves upward through the gap between plunger 2 and barrel 1 towards the mixed oil recovery groove 8, forming an oil film. This oil film provides both a lubricating effect on the sliding surfaces of plunger 2 and barrel 1, and a sealing effect that prevents fuel oil from moving downwards in barrel 1. As plunger 2 reciprocates, a portion of the lubricating oil moves downward, forming an oil film in the gap between plunger 2 and barrel 1. Lubricating oil that leaks below plunger 2 is discharged to the outside. The mixed oil recovery groove 8, located in the center of the three annular grooves formed in barrel 1, specifically between the fuel oil return groove 6 and the lubricating oil supply groove 10, is connected to the outside of barrel 1 via the mixed oil recovery passage 9. The mixed oil recovery passage 9 and the fuel oil return passage 7 are formed on the opposite side of barrel 1 from the lubricating oil supply