Fuel injection pump

Abstract

To provide a fuel injection pump for efficiently recovering fuel oil which leaks into a gap between a plunger and a barrel, to the outside of the barrel.SOLUTION: The fuel injection pump for a diesel engine including the plunger and the barrel includes a plurality of plunger grooves formed in the outer peripheral side face of the plunger, a recovery passage formed in the barrel to recover the fuel oil which leaks into a gap between the plunger and the barrel, from the barrel, and a recovery groove formed in the inner peripheral side face of the barrel in communication with the recovery passage, the recovery groove being formed in a lower position than the plurality of plunger grooves at the time the plunger reciprocating up and down is at a bottom dead center.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a fuel injection pump used in a diesel engine.

Background Art

[0002] The 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 having a plurality of centering grooves formed in a side wall that forms a sliding surface with the barrel. By allowing the fuel oil leaking from the lead portion at the upper end of the plunger into the gap between the plunger and the barrel to accumulate in the centering grooves, an effect of centering the plunger with respect to the barrel can be obtained.

[0003] Lubricating oil is supplied to the sliding surface between the plunger and the barrel. The lubricating oil moves downward through the gap between the plunger and the barrel and is discharged to the outside. If the amount of fuel oil leaking from the centering grooves downward to the lower side of the plunger increases, there is a possibility that the lubricating oil is diluted by the fuel oil and cannot exhibit its original lubricating performance. For this reason, two return grooves for recovering the fuel oil are formed in the barrel. In order to recover the fuel oil that could not be completely recovered by the first return groove, the second return groove is provided at a position lower than the first return groove. When the plunger is at the bottom dead center, among the plurality of centering grooves, the uppermost groove communicates with the first return groove, and the lowermost groove communicates with the second return groove. The fuel oil recovered from the first return groove is returned from the first return passage to the fuel supply / discharge port and reused. The fuel oil recovered from the second return groove is recovered from the second return passage outside the barrel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even with the conventional fuel injection pumps described above, it is not possible to completely recover the fuel oil leaking into the gap between the plunger and the barrel, and some of the fuel oil leaks below the plunger. It is desirable to efficiently recover the fuel oil from the gap between the plunger and the barrel and reduce the amount of fuel oil leaking below the plunger.

[0006] This disclosure has been made in view of the prior art, including the problems described above, and one of its objectives is to provide a fuel injection pump that can efficiently recover fuel oil leaking into the gap between the plunger and the barrel. [Means for solving the problem]

[0007] The fuel injection pump according to this disclosure is a fuel injection pump for a diesel engine including a plunger and a barrel, comprising: a plurality of plunger grooves formed on the outer peripheral side surface of the plunger; a recovery passage formed in the barrel for recovering fuel oil leaking from the gap between the plunger and the barrel; and a recovery groove formed on the inner peripheral side surface of the barrel communicating with the recovery passage, wherein the recovery groove is formed when the plunger, which reciprocates up and down, is at its bottom dead center. The plunger groove at the very bottom It is formed in a lower position than that.

[0008] In the above configuration, the device further includes a supply passage formed in the barrel for supplying lubricating oil to the sliding surfaces of the plunger and the barrel, and a supply groove formed on the inner circumferential surface of the barrel in communication with the supply passage, wherein the supply groove may be formed at a position lower than the recovery groove.

[0009] In the above configuration, the device further includes a return passage formed in the barrel to return fuel oil leaking into the gap between the plunger and the barrel back to the fuel intake chamber of the barrel, and a return groove formed on the inner circumferential side surface of the barrel in communication with the return passage, wherein the return groove may be formed at a position above the recovery groove.

[0010] In the above configuration, the return groove may be formed at a position lower than the uppermost plunger groove among the plurality of plunger grooves when the plunger is at its bottom dead center. [Effects of the Invention]

[0011] The fuel injection pump according to this disclosure can efficiently recover fuel oil leaked into the gap between the plunger and the barrel, thereby reducing the amount of fuel oil leaking downwards from the plunger. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view showing a fuel injection pump according to this embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating the movement of fuel oil and lubricating oil. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the fuel injection pump according to this disclosure will be described with reference to the attached drawings. Figure 1 is a schematic cross-sectional view showing 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.

[0014] 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, pressurized by the plunger 2 within the high-pressure chamber 4, and supplied to the fuel injector from 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 will be omitted.

[0015] 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.

[0016] 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 a fuel oil return passage 7. Fuel oil that leaks from the high-pressure chamber 4 into the gap between the inner circumferential side surface of barrel 1 and the outer circumferential side 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.

[0017] 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 a lubricating effect on the sliding surfaces of plunger 2 and barrel 1, as well as 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.

[0018] The mixed oil recovery groove 8, located in the center of the three annular grooves formed in barrel 1, that is, 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 passage 11. A portion of the lubricating oil supplied into barrel 1 from the lubricating oil supply groove 10 on the left side of Figure 1 is recovered to the outside of barrel 1 through the mixed oil recovery groove 8 on the right side. Fuel oil that reaches the mixed oil recovery groove 8 without being recovered in the fuel oil return groove 6 is also recovered to the outside of barrel 1 through the mixed oil recovery groove 8.

[0019] Specifically, the fuel oil that has moved downward without being recovered by the fuel oil return groove 6 and reached the mixed oil recovery groove 8 is supplied from the lubricating oil supply groove 10, moves upward, is mixed with the lubricating oil that has reached the mixed oil recovery groove 8, becomes mixed oil, and is recovered from the mixed oil recovery groove 8 to the outside of the barrel 1. The mixed oil of the lubricating oil and the fuel oil recovered from the barrel 1 is discarded, for example, into an open-air waste oil tank.

[0020] On the outer peripheral side surface of the plunger 2 slidably inserted into the barrel 1, a plurality of annular plunger grooves 5 (5a to 5e) are formed. In the example shown in FIG. 1, five plunger grooves 5, namely, the first plunger groove 5a, the second plunger groove 5b, the third plunger groove 5c, the fourth plunger groove 5d, and the fifth plunger groove 5e, having the same annular shape are formed at a predetermined pitch in the vertical direction. However, the number of the plunger grooves 5 is not particularly limited and may be four or less or six or more. Some of the plunger grooves 5 may be formed at a different pitch from other plunger grooves 5 or may have different shapes.

[0021] As shown in FIG. 1(a), when the plunger 2 is at the top dead center, all five plunger grooves 5 are located above the fuel oil return groove 6. As shown in FIG. 1(b), when the plunger 2 is at the bottom dead center, the second plunger groove 5b communicates with the fuel oil return groove 6. In other words, the fuel oil return groove 6 is formed at a position that communicates with the second plunger groove 5b when the plunger 2 is at the bottom dead center. The fuel oil return groove 6 communicates only with the second plunger groove 5b when the plunger 2 is at the bottom dead center and is formed at a position that does not communicate with the first plunger groove 5a and the third plunger groove 5c formed adjacent to the second plunger groove 5b. Here, the communication referred to in the present embodiment means that, in the vertical direction, at least a part of the groove formed on the outer peripheral side surface of the plunger 2 overlaps at least a part of the groove formed on the inner peripheral side surface of the barrel 1, and the groove of the plunger 2 is connected to the passage formed in the barrel 1 through the groove of the barrel 1.

[0022] As shown in Fig. 1(b), when the plunger 2 is at the bottom dead center, the third plunger groove 5c, the fourth plunger groove 5d, and the fifth plunger groove 5e are located below the fuel oil return groove 6 and above the mixed oil recovery groove 8. When the plunger 2 reciprocates between the top dead center and the bottom dead center, the third plunger groove 5c, the fourth plunger groove 5d, and the fifth plunger groove 5e pass through the fuel oil return groove 6. That is, when the plunger 2 reciprocates, the third plunger groove 5c, the fourth plunger groove 5d, and the fifth plunger groove 5e communicate with the fuel oil return groove 6.

[0023] As shown in Fig. 1(b), the first plunger groove 5a is located above the fuel oil return groove 6 even when the plunger 2 is at the bottom dead center. The first plunger groove 5a is always located above the fuel oil return groove 6 formed in the barrel 1 regardless of the position of the reciprocating plunger 2 and does not communicate with the fuel oil return groove 6. That is, the first plunger groove 5a does not communicate with any of the grooves formed on the inner peripheral surface of the barrel 1. In the groove portion formed in the barrel 1, the gap between the plunger 2 and the barrel 1 expands, but the first plunger groove 5a can move up and down without being affected by this expansion. When the plunger 2 is at the bottom dead center, two or more of the plurality of plunger grooves 5 may be formed above the fuel oil return groove 6.

[0024] As shown in Fig. 1(b), when the plunger 2 is at the bottom dead center, the mixed oil recovery groove 8 is located below all the plunger grooves 5. In other words, the mixed oil recovery groove 8 is formed at a position further below the fifth plunger groove 5e formed at the bottom of the outer peripheral surface of the plunger 2 at the bottom dead center. The mixed oil recovery groove 8 is always located below all the plunger grooves 5 regardless of the position of the reciprocating plunger 2 and does not communicate with the plunger grooves 5. When the plunger groove 5 passes through the groove portion formed in the barrel 1, the gap between the barrel 1 and the plunger 2 changes by the amount of the plunger groove 5, but the mixed oil recovery groove 8 is not affected by this change.

[0025] Figure 2 is a schematic diagram illustrating the movement of fuel oil and lubricating oil. Figure 2 shows plunger 2 at bottom dead center. Solid arrows in Figure 2 indicate the movement of fuel oil, and dashed arrows indicate the movement of lubricating oil. However, these arrows are intended to illustrate the main movement paths of fuel oil and lubricating oil and do not limit their movement.

[0026] As shown on the left side of Figure 2, lubricating oil is delivered from the lubricating oil supply passage 11 and supplied into the barrel 1 from the lubricating oil supply groove 10. A portion of the lubricating oil moves upward to form an oil film on the sliding surfaces of the plunger 2 and the barrel 1. Another portion of the lubricating oil moves downward and is discharged to the outside.

[0027] As the plunger 2 moves upward from bottom dead center to top dead center, and the fuel oil drawn into the high-pressure chamber 4 is discharged from the fuel outlet 12 at the upper end, some of the compressed fuel oil leaks downward through the gap between the outer surface of the plunger 2 and the inner surface of the barrel 1, i.e., onto the sliding surfaces of the plunger 2 and the barrel 1. The leaked fuel oil enters the plunger groove 5, providing a centering effect that aligns the radial center of the plunger 2 with the radial center of the barrel 1. In addition, the leaked fuel oil forms an oil film on the sliding surfaces of the plunger 2 and the barrel 1, providing a lubricating effect.

[0028] As the plunger 2 reciprocates between its top dead center and bottom dead center, the four plunger grooves 5b to 5e communicate with the fuel oil return groove 6. Fuel oil that leaks into the gap between the plunger 2 and the barrel 1 and accumulates in the plunger grooves 5b to 5e is recovered from the fuel oil return groove 6, as shown on the right side of Figure 2. The fuel oil is returned from the fuel oil return passage 7 to the fuel intake chamber 3 in the barrel 1.

[0029] Some of the fuel oil that is not recovered from the fuel oil return groove 6 moves further down the gap between the plunger 2 and the barrel 1, while lubricating oil supplied from the lubricating oil supply groove 10 moves upward from below. As a result, the fuel oil moving from above and the lubricating oil moving from below mix together to form a mixed oil, which is recovered from the mixed oil recovery groove 8, as shown on the right side of Figure 2. The mixed oil is recovered out of the barrel 1 through the mixed oil recovery passage 9.

[0030] Fuel oil leaking from above the plunger 2 into the gap between the plunger 2 and the barrel 1 moves through the region where the gap between the plunger 2 and the barrel 1 changes due to the plunger groove 5 and the fuel oil return groove 6, up to the area below where the mixed oil recovery groove 8 is formed. On the other hand, lubricating oil supplied from the lubricating oil supply groove 10 into the gap between the plunger 2 and the barrel 1 moves through the region where the gap between the plunger 2 and the barrel 1 does not change even while the plunger 2 moves up and down, up to the area above where the mixed oil recovery groove 8 is formed.

[0031] The path from the lubricating oil supply groove 10 to the mixed oil recovery groove 8 is a stable path with a nearly constant gap between the plunger 2 and the barrel 1. As a result, the amount of lubricating oil recovered from the mixed oil recovery groove 8 to the outside of the barrel 1 increases compared to when the plunger groove 5 passes through or communicates with the mixed oil recovery groove 8. This increase in lubricating oil recovered from the mixed oil recovery groove 8 leads to an improved sealing effect of the lubricating oil that prevents the movement of fuel oil below the mixed oil recovery groove 8, thereby reducing the amount of fuel oil leaking downwards from the plunger 2.

[0032] As described above, in this embodiment of the fuel injection pump, multiple annular grooves are formed on the outer circumference of the plunger, and multiple annular grooves are also formed on the inner circumference of the barrel. A portion of the fuel oil that leaks into the gap between the plunger and the barrel is recovered and reused from the fuel oil return groove in the barrel. In addition, fuel oil that leaks below the fuel oil return groove is recovered out of the barrel from the mixed oil recovery groove along with the lubricating oil that has moved upward from the lubricating oil supply groove. The mixed oil recovery groove is always positioned below all plunger grooves while the plunger is reciprocating up and down. Therefore, compared to the case where the plunger groove passes through or communicates with the mixed oil recovery groove, the amount of lubricating oil recovered from the mixed oil recovery groove increases, and the amount of fuel oil that leaks further below the mixed oil recovery groove can be reduced. [Industrial applicability]

[0033] As described above, the fuel injection pump according to this disclosure is useful for efficiently recovering fuel oil leaking into the gap between the plunger and the barrel out of the barrel. [Explanation of Symbols]

[0034] 1 barrel 2 plungers 3. Fuel intake chamber 4. High-pressure chamber 5 (5a~5e) Plunger groove 6. Fuel oil return groove 7. Fuel oil return passage 8. Mixed oil recovery channel 9. Mixed oil recovery passage 10 Lubricating oil supply groove 11 Lubricating oil supply passage 12 Fuel outlet

Claims

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, A recovery groove formed on the inner circumferential surface of the barrel, communicating with the recovery passage, It has, The recovery groove is formed at a position lower than the lowest of the multiple plunger grooves when the plunger, which reciprocates vertically, is at its bottom dead center. A fuel injection pump characterized by the following features.

2. A supply passage formed in the barrel for supplying lubricating oil to the sliding surfaces of the plunger and the barrel, A supply groove formed on the inner circumferential surface of the barrel, communicating with the supply passage, It further possesses, The supply groove is formed at a lower position than the recovery groove. The fuel injection pump according to feature 1.

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, A return groove formed on the inner circumferential surface of the barrel, communicating with the return passage, It further possesses, The return groove is formed at a position above the recovery groove. A fuel injection pump according to claim 1 or 2, characterized in that it is as described above.

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.

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