EP2635796B1

EP2635796B1 - Injection pump

Info

Publication number: EP2635796B1
Application number: EP11770842.0A
Authority: EP
Inventors: Håkan NYNÄS; Gösta Liljenfeldt
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2010-11-05
Filing date: 2011-09-22
Publication date: 2015-08-26
Anticipated expiration: 2031-09-22
Also published as: CN103228903A; EP2635796A2; FI20106161A; KR20130103768A; WO2012059623A3; FI20106161A0; CN103228903B; WO2012059623A2; KR101692231B1

Description

Technical field of the invention

The present invention relates to an injection pump for an internal combustion engine, as defined in the preamble of claim 1.

Background of the invention

Injection pumps that are capable of producing high injection pressures are needed as fuel injection pumps of compression ignition internal combustion engines. Especially in large internal combustion engines, similar injection pumps can also be used for injecting other fluids, such as water for reducing emissions of the engine. The expression large internal combustion engine is used here to refer to such engines that are used for instance at power plants or as the main or auxiliary engines of ships.
Patent application EP 0715070 A1 discloses an injection pump for injecting pressure medium into a cylinder of an internal combustion engine. The pump comprises two reciprocating piston members being arranged inside a common pump body. The piston members are provided with control edges so that the control edge of one of the piston members determines the starting moment of injection and the control edge of the other piston member determines the termination of injection. With this kind of an injection pump high injection pressures can be achieved and the injection timing can be adjusted. However, the construction of EP 0715070 A1 has some weaknesses relating to fluid flow between the chambers in which the piston members are arranged. The construction is also challenging to seal effectively.
US 3 294 075 A discloses a high pressure fuel pump having two separate pistons driven by two separate plungers with separate rollers.

Summary of the invention

The object of the present invention is to provide an improved injection pump for an internal combustion engine. The characterizing features of an injection pump according to the present invention are given in the characterizing part of claim 1.
According to the present invention, the injection pump for an internal combustion engine comprises a pump body and a first fluid chamber and a second fluid chamber being arranged inside the pump body. The first fluid chamber and the second fluid chamber are in mutual fluid communication. A first reciprocating plunger is arranged inside the pump body and protrudes into the first fluid chamber. The pump also comprises a second plunger being arranged at least partly inside the second fluid chamber, a first fluid port being in fluid communication with the first fluid chamber, a second fluid port being in fluid communication with the second fluid chamber, a fluid supply channel being in fluid communication with the first fluid chamber and/or the second fluid chamber via the first fluid port and/or the second fluid port, and a fluid outlet being in fluid communication with the first fluid chamber and/or the second fluid chamber. According to the invention, the first plunger and the second plunger have different diameters.
When one of the plungers has smaller diameter than the other one, the fluid flow between the first and the second fluid chamber is reduced. The pump body can also be made smaller. A further advantage of the invention is that the sealing of the injection pump can be improved.
According to an embodiment of the invention, the diameter of the second plunger is smaller than the diameter of the first plunger. According to another embodiment of the invention, the diameter of the second plunger is less than 50 percent of the diameter of the first plunger. According to still another embodiment of the invention, the diameter of the second plunger is less than 15 percent of the diameter of the first plunger.
According to an embodiment of the invention, the first plunger is arranged to control the starting point of the fluid injection and the second plunger is arranged to control the end point of the fluid injection. If the diameter of the second plunger is smaller than the diameter of the first plunger, less power is needed for rotating the second plunger. In many cases the end point of the injection is adjusted more often than the starting point of the injection, and therefore it might be advantageous to use the second plunger for controlling the end point of the fluid injection.
According to an embodiment of the invention, the second plunger is arranged to control the starting point of the fluid injection and the first plunger is arranged to control the end point of the fluid injection.
According to an embodiment of the invention, the first plunger comprises a rotationally asymmetric cut-out for allowing outflow from the first fluid chamber when being in fluid communication with the first fluid port. According to another embodiment of the invention, the injection pump comprises means for rotating the first plunger. The cut-out and the rotating means enable adjustments of the starting and/or the end point of the fluid injection.
According to an embodiment of the invention, the second plunger comprises a rotationally asymmetric cut-out for allowing outflow from the second fluid chamber when being in fluid communication with the second fluid port. According to another embodiment of the invention, the injection pump comprises means for rotating the second plunger. The cut-out and the rotating means enable adjustments of the starting and/or the end point of the fluid injection.
According to an embodiment of the invention, the injection pump comprises a third fluid port being in fluid communication with the first fluid chamber. If the first fluid chamber comprises two separate fluid ports, one of the fluid ports can be used for introducing fluid into the fluid chamber, while the other one can be used to relieve pressure from the chamber at the end of the injection.
According to an embodiment of the invention, the injection pump comprises a connecting duct for connecting the first fluid chamber to the second fluid chamber.
According to an embodiment of the invention, the connecting duct is arranged to connect the outlet ends of the first and second fluid chambers.
According to an embodiment of the invention, the ends of the connecting duct are arranged at a distance from both ends of the first fluid chamber and the second fluid chamber.
According to an embodiment of the invention, the fluid outlet is in fluid communication only with the first fluid chamber.
When the connecting duct is arranged so that it does not connect the ends of the fluid chambers, and the fluid outlet is in fluid communication only with the first fluid chamber, the second plunger can be arranged to block the connecting duct so that the second plunger is not used for pressurizing the fluid. This is advantageous since better efficiency of the pump can be achieved. The pressure in the second fluid chamber also remains lower.
According to an embodiment of the invention, the first and the second fluid ports are in fluid communication with the fluid supply channel. When the same fluid ports work as fluid inlets and spill ports, no separate ducts for collecting the excess fluid are needed.
According to an embodiment of the invention, the injection pump comprises a thrust means for moving the first plunger.
According to an embodiment of the invention, the second plunger is arranged to be moved by the thrust means. If also the second plunger is moved by the same thrust means as the first plunger, the injection pump can be driven by a single cam of a camshaft.
According to an embodiment of the invention, the injection pump is a fuel injection pump.

Brief description of the drawings

Fig. 1: shows an injection pump according to an embodiment of the invention.
Fig. 2: shows the injection pump of Fig. 1 at the end of the compression stroke.
Fig. 3: shows a design option for the second plunger.
Fig. 4: shows another design option for the second plunger.
Fig. 5: shows an injection pump according to another embodiment of the invention.
Fig. 6: shows an injection pump according to still another embodiment of the invention.
Fig. 7: shows an injection pump with electrical injection timing.

Detailed description of the invention

Embodiments of the present invention are now described in more detail with reference to the accompanying drawings. An injection pump 1 according to an embodiment of the invention is shown in Figs. 1 and 2. The pump 1 is used for pressurizing fluid, for instance fuel, that is injected through nozzles 25 for instance into a cylinder of an internal combustion engine. The injection pump 1 comprises a pump body 2. The pump body 2 is formed of a lower body part 2a and an upper body part 2b. Inside the pump body 2, there is an inner body part 20. A cylindrical space inside the inner body part 20 forms a first fluid chamber 15. There is also another cylindrical space inside the inner body part 20 forming a second fluid chamber 16. A first reciprocating plunger 3 protrudes into the first fluid chamber 15, and a second plunger 4 protrudes into the second fluid chamber 16. The first plunger 3 is attached to a thrust means 5, which can reciprocate inside the pump body 2. The thrust means 5 comprises a roller 5a that can rotate against a cam 6 of a camshaft. The second plunger 4 is attached to the same thrust means 5 as the first plunger 3. The injection pump 1 is also provided with a spring 29 that is arranged to push the thrust means 5 outwards, i.e. towards the cam 6.
The first plunger 3 and the second plunger 4 have different diameters. In the embodiments shown in the figures, the diameter of the second plunger 4 is smaller than the diameter of the first plunger 3. Due to the difference in diameters, fluid flow between the first fluid chamber 15 and the second fluid chamber 16 is reduced. The pump body 2 can also be made smaller.
A peripheral fluid supply channel 10 is arranged between the pump body 2 and the inner body part 20. Borings in the inner body part 20 form a first fluid port 11 and a second fluid port 12 connecting the first fluid chamber 15 and the second fluid chamber 16 to the fluid supply channel 10. There is also a third fluid port 13 that connects the first fluid chamber 15 to the fluid supply channel 10. A fluid outlet 14 is connected to the first and second fluid chambers 15, 16. A check valve 17 comprising a spring 17a is arranged in the fluid outlet 14 for preventing back-flow into the first and second fluid chambers 15, 16.
The first plunger 3 is provided with a cut-out 18. The cut-out 18 comprises a peripheral section 18c and a longitudinal section 18a that is arranged between the peripheral section 18c and the end of the first plunger 3. The longitudinal section 18a broadens towards the peripheral section 18 forming a beveled section 18b.
When the roller 5a is on the base circle 6a of the cam 6, the first and second plungers 3, 4 are at their outermost positions. The cut-out 18 of the first plunger 3 is aligned with the third fluid port 13 and the second plunger 4 does not cover the second fluid port 12. The fluid to be injected can thus flow from the fluid supply channel 10 into the first fluid chamber 15 through the third fluid port 13 and into the second fluid chamber 16 through the second fluid port 12.
When the cam 6 rotates, the roller 5a is engaged with the cam race 6b of the cam 6 and starts to push the thrust means 5 inwards. As long as the third fluid port 13 and/or the second fluid port 12 are not covered by the outer surfaces of the first plunger 3 and the second plunger 4, the fluid in the first and the second fluid chambers 15, 16 can flow back into the fluid supply channel 10 and the check valve 17 remains closed. When the first and the second plungers 3, 4 move inwards, their outer surfaces eventually cover the third and second fluid ports 13, 12 and prevent the fluid from flowing into the fluid supply channel 10. Pressure in the first and second fluid chamber 15, 16 starts to increase and eventually the check valve 17 opens allowing the fluid to flow out of the fluid chambers 15, 16. When the plungers 3, 4 move further inwards, the first plunger 3 eventually reaches the position shown in Fig. 2. At this position, the peripheral section 18c of the cut-out 18 of the first plunger 3 is aligned with the first fluid port 11. The fluid in the first chamber 15 can thus flow out of the fluid chamber 15 into the fluid supply channel 10 and pressure in the first and the second fluid chambers 15, 16 drops closing the check valve 17.
The timing of the fluid injection can be adjusted by the second plunger 4. The second plunger 4 is provided with means 9 for rotating the plunger 4, the means 9 comprising a rack 9a and a pinion 9b. When the rack 9a is moved it rotates the pinion 9b that is attached to an extension of the second plunger 4. The inner end of the second plunger 4 is provided with a cut-out 19, as shown in Figs. 3 and 4. When the second plunger 4 is rotated, it can be affected when the second fluid port 12 is blocked by the second plunger 4 and the starting point of the fluid injection can thus be adjusted. In the embodiment of Fig. 3, the second plunger 4 has a tapered cut-out 19 at the free end, i.e. the inner end of the plunger 4. By rotating the second plunger 4, it can thus be steplessly adjusted when the plunger 4 blocks the second fluid port 12 and the injection starts. In the embodiment of Fig. 4, the second plunger 4 comprises a stepped cut-out 19. If the second plunger 4 is rotated to the position shown on the left, the latest possible injection timing is in use. When the second plunger is in the position shown on the right, the earliest possible timing is in use. The positions in the middle are used for intermediate injection timings.
The quantity of the injected fluid can be adjusted by the first plunger 3. The first plunger 3 is also provided with a rack 8a and a pinion 8b, and the first plunger 3 can thus be rotated in a similar way as the second plunger 3. When the first plunger 3 is rotated, it can be affected when the cut-out 18 is aligned with the first fluid 11 port and the pressure in the fluid chambers 15, 16 is relieved and the injection thus terminated.
The embodiment of Fig. 5 is similar to that of Figs. 1 and 2. A difference is that the injection pump 1 of Fig. 5 does not comprise a third fluid port like the injection pump 1 of Figs. 1 and 2. Another difference between these two embodiments is that in the embodiment of Fig. 5, the fluid outlet 14 is connected only to the first fluid chamber 15. The first fluid chamber 15 and the second fluid chamber 16 are mutually connected by a connecting duct 22. The connecting duct 22 is located so that it connects the outlet ends of the fluid chambers 15, 16 to each other. In the embodiment of Fig. 5, the second plunger 4 is not moved directly by the thrust means 5, but a push rod 23 that is connected to the thrust means 5 is arranged to move the second plunger 4. A gap 24 can be left between the push rod 23 and the second plunger 4 when the thrust means 5 is not at its innermost position, i.e. at the end of the compression stroke. By adjusting the gap 24, the injection timing can be affected. If a large gap 24 is left between the push rod 23 and the second plunger 4 when the roller 5a of the thrust means is on the base circle of the cam 6, later injection timing is achieved, since the second plunger 4 does not move until the push rod 23 and the plunger 4 are in contact with each other. If the gap 24 is small or the push rod 23 and the second plunger 4 are in contact even when the roller 5a is on the base circle 6a of the cam 6, the injection timing is earlier. A second spring 30 is arranged to push the second plunger 4 outwards, i.e. towards the cam 6.
In the embodiment of Fig. 5, the first fluid chamber 15 comprises only one fluid port 11. Before the start of the injection, fluid can thus flow into the first fluid chamber 15 through the first fluid port 11. The end point of the injection depends on the moment when the cut-out 18 of the first plunger 3 is aligned with the first fluid port 11.
In Fig. 6 is shown still another embodiment of the present invention. In the embodiment of Fig. 6, the fluid outlet 14 is connected only to the first fluid chamber 15. Instead of the fluid outlet 14, the first fluid chamber 15 and the second fluid chamber 16 are connected by a similar connecting duct 22 as in the embodiment of Fig. 5. The main difference between the embodiment of Fig. 5 and the embodiment of Fig. 6 is that in the embodiment of Fig. 6 the connecting duct 22 does not connect the outlet ends of the fluid chambers 15, 16. Instead, the connecting duct 22 is arranged approximately in the middle of the first and the second fluid chambers 15, 16. The second plunger 4 is thus not used for pressurizing the fluid but it only controls the injection timing. Injection starts when the second plunger 4 blocks the connecting duct 22 between the first fluid chamber 15 and the second fluid chamber 16. When the connecting duct 22 is blocked by the second plunger 4, the second fluid chamber 16 is not in fluid communication with the first fluid chamber 15 or the fluid outlet 14. An advantage of this embodiment is that since only the first plunger 3 is used for pressurizing the fluid, the efficiency of the pump is better. Another advantage of the embodiment of Fig. 6 is that the pressure in the second fluid chamber 16 is lower during the injection.
In the embodiment of Fig. 7, the second fluid chamber 16 is arranged in the upper body part 2b of the pump body 2. The second plunger 4 is not moved directly by the thrust means 5. Instead, the second plunger 4 is a valve member that is moved by an electrical actuator 26. When the cut-out 19 of the second plunger 4 is aligned with the second fluid port 12 and the connecting duct 22, the fluid can flow from first fluid chamber 15 into the second fluid chamber 16 and further into the fluid supply channel 10. A spindle 27 of a linear position sensor 28 is attached to the thrust means 5. When the spindle 27 reaches a predetermined position, the valve actuator 26 receives a signal for blocking the fluid connection between the first and the second fluid chambers 15, 16. The second plunger 4 is moved so that fluid flow into the second fluid chamber 16 is prevented, and the fluid flows through the fluid outlet 14 to the injection nozzle 25.
It will be appreciated by those skilled in the art that the invention is not limited to the embodiments described above, but may vary within the scope of the appended independent claim. For instance, there are many possible designs for the cut-outs of the plungers. Separate thrust means can be provided for moving the first plunger and the second plunger, and the thrust means could be arranged outside the pump body. It is also possible that the first plunger is arranged to control the starting point of injection, whereas the second plunger is arranged to control when the injection is terminated. Either of the plungers can have smaller diameter than the other. Features from the different embodiments described above can also be combined.

Claims

An injection pump (1) for an internal combustion engine, the injection pump (1) comprising
- a pump body (2),

- a first fluid chamber (15) and a second fluid chamber (16) being arranged inside the pump body (2), the first fluid chamber (15) and the second fluid chamber (16) being in mutual fluid communication,

- a first reciprocating plunger (3) being arranged inside the pump body (2) and protruding into the first fluid chamber (15),

- a second plunger (4) being arranged at least partly inside the second fluid chamber (16) and having a different diameter than the first plunger (3),

- a first fluid port (11) being in fluid communication with the first fluid chamber (15),

- a second fluid port (12) being in fluid communication with the second fluid chamber (16).

- a fluid supply channel (10) being in fluid communication with the first fluid chamber (15) and/or the second fluid chamber (16) via the first fluid port (11) and/or the second fluid port (12),

- a fluid outlet (14) being in fluid communication with the first fluid chamber (15) and/or the second fluid chamber (16), and

- a thrust means (5) for moving the first plunger (3) and the second plunger (4), the thrust means (5) comprising a roller (5a) that can rotate against a cam (6) of a camshaft,
characterized in that the diameter of the second plunger (4) is less than 15 percent of the diameter of the first plunger (3) and in that the second plunger (4) is attached to the same thrust means (5) as the first plunger (3).
An injection pump (1) according to claim 1, characterized in that the first plunger (3) is arranged to control the starting point of the fluid injection and the second plunger (4) is arranged to control the end point of the fluid injection.
An injection pump (1) according to claim 1 or 2, characterized in that the second plunger (4) is arranged to control the starting point of the fluid injection and the first plunger (3) is arranged to control the end point of the fluid injection.
An injection pump (1) according to any of the preceding claims, characterized in that the first plunger (3) comprises a rotationally asymmetric cut-out (18) for allowing outflow from the first fluid chamber (15) when being in fluid communication with the first fluid port (11).
An injection pump (1) according to any of the preceding claims, characterized in that the injection pump (1) comprises means (8a, 8b) for rotating the first plunger (3).
An injection pump (1) according to any of the preceding claims, characterized in that the second plunger (4) comprises a rotationally asymmetric cut-out (19) for allowing outflow from the second fluid chamber (16) when being in fluid communication with the second fluid port (12).
An injection pump (1) according to any of the preceding claims, characterized in that the injection pump (1) comprises means (9a, 9b) for rotating the second plunger (4).
An injection pump (1) according to any of the preceding claims, characterized in that the injection pump (1) comprises a third fluid port (13) being in fluid communication with the first fluid chamber (15).
An injection pump (1) according to any of the preceding claims, characterized in that the injection pump (1) comprises a connecting duct (22) for connecting the first fluid chamber (15) to the second fluid chamber (16).
An injection pump (1) according to claim 9, characterized in that the connecting duct (22) is arranged to connect the outlet ends of the first and second fluid chambers (15, 16).
An injection pump (1) according to claim 9, characterized in that the ends of the connecting duct (22) are arranged at a distance from both ends of the first fluid chamber (15) and the second fluid chamber (16).
An injection pump (1) according to any of the preceding claims, characterized in that the fluid outlet (14) is in fluid communication only with the first fluid chamber (15).
An injection pump (1) according to any of the preceding claims, characterized in that the first and the second fluid ports (11, 12) are in fluid communication with the fluid supply channel (10).
An injection pump (1) according to any of the preceding claims, characterized in that the injection pump (1) is a fuel injection pump.