JP2008038717A - Fuel injection control system for internal combustion engine - Google Patents

Abstract

A fuel injection control system capable of increasing the pressure of fuel according to the state of an internal combustion engine and suppressing the generation of return fuel.
A pressure accumulator that stores fuel in a pressurized state, a fuel injection nozzle that injects fuel supplied from the pressure accumulator, and a fuel accumulator disposed between the pressure accumulator and the fuel injection nozzle. A fuel injection control system for an internal combustion engine, comprising a pressure booster 30A for increasing pressure, wherein the pressure booster 30A has a plurality of stepped portions and reciprocates in the axial direction in response to the pressure of the fuel. And a cylinder 31 having an inner wall formed so as to correspond to the outer shape of the piston and allowing movement of the piston, and depending on the state of the internal combustion engine, It further includes pressure increase adjusting mechanisms 37 and 39 that change the pressure increase ratio of the fuel by communicating a plurality of intermediate chambers 33-1 and 33-2 formed between the step portion and the inner wall of the cylinder.
[Selection] Figure 2

Description

  The present invention relates to a fuel injection control system suitable for an internal combustion engine, particularly a diesel engine. More specifically, a fuel in which a pressure intensifier for increasing the pressure (fuel pressure) of fuel supplied to the injection nozzle is disposed between the pressure accumulator and the fuel injection nozzle (hereinafter simply referred to as an injection nozzle). The present invention relates to an injection control system.

  As a fuel injection system applied to a fuel supply system of a diesel engine, a system provided with a pressure accumulator called a common rail is well known. In this system, a plurality of injection nozzles are connected to a common rail that stores pressurized fuel. In this system, fuel supplied from a fuel supply pump is temporarily stored in a common rail in a pressurized state, and fuel is injected into the cylinder when each injection nozzle is opened. An injection system that employs a common rail has a merit that the injection pressure and the injection amount can be controlled independently, and has been widely adopted in recent years.

  In recent years, further improvements in exhaust gas purification and fuel efficiency have been required for internal combustion engines from the viewpoint of environmental protection. In order to meet this demand, it is important to establish a technique for increasing the fuel injection pressure for diesel engines. However, in order to set the pressure of the fuel supplied to the injection nozzle to a higher pressure, a structure having sufficient pressure resistance performance including the common rail and piping must be provided, resulting in an increase in cost. Thus, for example, Patent Document 1 proposes a fuel injection control device in which a pressure booster that increases the fuel pressure is provided between the common rail and the injection nozzle. If the pressure intensifier is arranged downstream of the common rail in this way, the fuel pressure can be increased without changing the common rail side, so that the fuel injection pressure can be increased relatively easily.

  Here, as shown in Patent Document 1, a conventional pressure booster employs a structure in which a stepped piston is arranged in a cylinder to increase the pressure of fuel. A general structure of the intensifier will be described with reference to the drawings. FIG. 6 is a diagram schematically showing the relationship between the conventional pressure intensifier 110 and the injection nozzle 120. Although the illustration of the common rail is omitted in FIG. 6, the pressure booster 110 is supplied with fuel pressurized from the common rail. The pressure intensifier 110 has a structure in which a stepped piston 115 that reciprocates in the axial direction (vertical direction in FIG. 6) is housed in a cylinder 111. The inner wall of the cylinder 111 is formed in a step shape so as to allow the stepped piston 115 to move.

  In such a pressure intensifier 110, a high pressure chamber 112 is formed in a cylinder 111 above a piston 115, an intermediate chamber 113 is formed in a step portion between a large diameter portion BD and a small diameter portion SD, and a pressure increase chamber 114 is formed below the piston 115. . A fuel passage 118 for supplying fuel from the common rail is connected to the chambers 112 to 114, and a fuel return passage (return passage) 119 is further connected to the intermediate chamber 113. Although a detailed configuration is omitted in FIG. 6, actually, each of the passages 118 and 119 is appropriately provided with a valve device, a control circuit for controlling the valve device according to the state of the orifice or the diesel engine, and the like. ing.

When increasing the pressure of the fuel supplied to the injection nozzle 120 with the above structure, for example, the pressure increasing operation is executed as follows. First, fuel pressurized from the common rail is supplied to each chamber 112-114. When each of the chambers 112 to 114 is filled with fuel, the upper high-pressure chamber 112, the lower intermediate chamber 113, and the pressure-increasing chamber 114 are in a state of being balanced in a vertical direction. Thereafter, the fuel return passage 119 is opened, and the fuel in the intermediate chamber 113 is extracted (returned). This destroys the pressure balance in the vertical direction. By performing such an operation, the fuel pressure in the pressure increasing chamber 114 is increased by a considerable amount in the intermediate chamber 113, so that the fuel supplied to the injection nozzle 12 can be increased.

JP 2005-98131 A

In the conventional pressure intensifier, the pressure is increased by returning the fuel introduced into one intermediate chamber as described above to the fuel return passage 119. The pressure increase ratio is the area ratio of the large diameter part BD and the small diameter part SD. If each of BD and SD represents the diameter of each diameter portion, the area ratio is constant at (BD / SD) ² .

  By the way, considering the situation where the engine is actually driven, it may not be necessary to increase the fuel pressure depending on the driving situation. However, when the pressure intensifier as described above is arranged, a constant pressure increase is performed even when it is not necessary to increase the pressure, and the above-described fuel return (fuel return) occurs. Therefore, a wasteful operation of increasing the pressure of the fuel which is not necessary in the conventional fuel injection control system and returning the fuel is frequently performed.

  Accordingly, an object of the present invention is to provide a fuel injection control system that can suppress the generation of return fuel by increasing the pressure of fuel according to the state of the internal combustion engine.

  The above-mentioned object is arranged between a pressure accumulator for storing fuel in a pressurized state, a fuel injection nozzle for injecting fuel supplied from the pressure accumulator, and the pressure accumulator and the fuel injection nozzle. A fuel injection control system for an internal combustion engine, comprising a pressure intensifier for increasing pressure, wherein the pressure intensifier has a plurality of step portions and reciprocates in the axial direction under the pressure of the fuel. And an inner wall formed to correspond to the outer shape of the piston and a cylinder formed to allow movement of the piston, and depending on the state of the internal combustion engine, the step portion of the piston and the cylinder This can be achieved by a fuel injection control system for an internal combustion engine that further includes a pressure increase adjustment mechanism that changes the pressure increase ratio of the fuel by communicating a plurality of intermediate chambers formed between the inner wall of the cylinder and each other.

  According to the present invention, the fuel pressure increase ratio can be changed by selectively communicating a plurality of intermediate chambers formed between the stepped portion of the piston and the inner wall of the cylinder. The pressure can be increased. As a result, useless pressure increase can be suppressed, and the amount of fuel to be returned along with the pressure increasing operation can be reduced.

  And the said pressure increase adjustment mechanism is as a structure containing the communication path which connects the said intermediate chambers formed in multiple numbers, and the valve apparatus which opens and closes the said communication path according to the pressure of the fuel supplied from the said pressure accumulator. Also good.

  The pressure-increasing adjustment mechanism may include a communication groove formed on the surface of the piston, and the communication groove may communicate with a plurality of the intermediate chambers formed according to the lift amount of the piston.

  According to the present invention, it is possible to provide a fuel injection control system that can suppress the generation of return fuel by increasing the pressure of fuel according to the state of the internal combustion engine.

  Hereinafter, a fuel injection control system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a fuel injection control system 1A according to a first embodiment applied to a diesel engine. The fuel injection control system 1A of the present embodiment includes a common rail 10, an injection nozzle 20, and a pressure intensifier 30A, which are pressure accumulators, as in the prior art. These are connected to each other by a plurality of fuel passages. The fuel passage 40 from the common rail 10 is connected to the high pressure chamber 32 of the pressure intensifier 30A. Further, the fuel passage 40 is branched halfway to become a fuel passage 41, and a servo valve 50 is provided in the fuel passage 41. Further, two fuel passages 42 and 43 are connected to the downstream side of the servo valve 50. The fuel passage 42 is connected to the intermediate chamber 33 of the pressure booster 30A. The fuel passage 43 is connected to the control chamber 21 of the injection nozzle 20. Further, fuel is supplied to the pressure increasing chamber 34 of the pressure intensifier 30 </ b> A through a branch passage 47 from the fuel passage 40. Further, the pressure increasing chamber 34 is connected to the injection nozzle 20 through a fuel passage 45 so that the increased pressure fuel can be injected from the tip of the injection nozzle 20.

  The common rail 10 is connected to a fuel tank (not shown), and stores the fuel by changing the pressure of the fuel according to the state of the diesel engine. The servo valve 50 adjusts the flow of fuel by switching the communication between the fuel passage 41 and the fuel passages 42 and 43. That is, the servo valve 50 supplies the fuel from the common rail 10 to the intermediate chamber 33 and the control chamber 21 and returns the fuel from the chambers 33 and 21. The servo valve 50 is connected to a fuel passage 46 through which returned fuel is released. Thus, the servo valve 50 functions as a flow path switching device that supplies fuel to the intermediate chamber 33 of the pressure intensifier 30A and the control chamber 21 of the injection nozzle 20 and returns fuel therefrom. The common rail 10 and the servo valve 50 may be driven by using an ECU (Electronic Control Unit) 60 of a diesel engine, for example.

  The schematic configuration shown in FIG. 1 is the same as that of the conventional fuel injection control system, but the pressure intensifier 30A has a novel structure. FIG. 2 specifically shows the structure of the pressure intensifier 30A schematically shown in FIG. The structure of the pressure intensifier 30A will be described with reference to FIG.

  In the pressure intensifier 30A, a piston 35 formed in a step shape in the cylinder 31 is disposed so as to reciprocate in the axial direction (vertical direction in FIG. 2). The piston 35 is a two-stage (multiple-stage) type piston in which a large-diameter portion 35BD, a medium-diameter portion 35MD, and a small-diameter portion 35SD are formed. The piston 35 is a structure in which three types of cylindrical bodies having different diameters are connected and integrated. The diameter of the small diameter portion 35SD is D1, the diameter of the medium diameter portion 35MD is D2, and the diameter of the large diameter portion 35BD is D3. The inner wall of the cylinder 31 is formed in a step shape so as to allow the movement of the two-stage type piston 35.

  Also in the case of the pressure intensifier 30 </ b> A, a plurality of rooms (chambers) are formed in the cylinder 31. A high pressure chamber 32 is formed above the piston 35 and a pressure increasing chamber 34 is formed below the piston 35. This point is the same as in the case of the conventional pressure intensifier, but in the first embodiment, the intermediate chamber 33 is divided into two intermediate chambers 33-1 and 33-2.

  The plurality of intermediate chambers 33 are formed according to the number of step portions provided on the outer periphery of the piston 35. The piston 35 is formed in two or more stages so that at least two (a plurality) intermediate chambers are formed. The piston 35 of this embodiment is the least two-stage configuration example in order to facilitate understanding of the invention. Accordingly, two intermediate chambers, a first intermediate chamber 33-1 and a second intermediate chamber 33-2 are formed. In the present embodiment, a single intermediate chamber, which is one in the prior art, is configured by a plurality of intermediate chambers having a small volume. By forming a plurality of intermediate chambers in this way, the fuel pressure increase ratio can be changed. This will be clarified in the following explanation.

  The aforementioned fuel passage 42 (see FIG. 1) is connected to the first intermediate chamber 33-1. The first intermediate chamber 33-1 is connected to the second intermediate chamber 33-2 positioned above by two communication passages 36 and 37. The first communication passage 36 is a passage for further feeding the fuel that has entered the first intermediate chamber 33-1 into the second intermediate chamber 33-2, and a check valve 38 is provided on the way. The check valve 38 prevents the back flow of fuel from the second intermediate chamber 33-2 to the first intermediate chamber 33-1. The second communication passage 37 is a passage for returning the fuel to the first intermediate chamber 33-1 when the fuel in the second intermediate chamber 33-2 reaches a predetermined pressure or higher. A pressure regulating valve 39 set to open when the fuel pressure in the intermediate chamber 33-2 exceeds a predetermined pressure is provided. The pressure regulating valve 39 is initially set so as to close the communication passage 37 by urging the valve body 39V upward by a spring 39C. When the pressure regulating valve 39 is opened, the fuel in the second intermediate chamber 33-2 returns (returns) to the first intermediate chamber 33-1. The valve body 39 </ b> V disposed inside the pressure regulating valve 39 has a rod shape, extends upward, and has a T-shaped head that projects into the high-pressure chamber 32. The lower limit of the pressure regulating valve 39 is set by this head.

  Furthermore, a communication passage 51 that communicates the second intermediate chamber 33-2 and the high-pressure chamber 32 is provided. The communication passage 51 is a passage that allows the fuel in the second intermediate chamber 33-2 to flow into the high-pressure chamber 32, and a check valve 52 is provided in the middle. The check valve 52 prevents the back flow of fuel from the high pressure chamber 32 to the second intermediate chamber 33-2.

  The pressure boosting operation by the fuel injection control system 1A including the pressure booster 30A having the above structure is executed as follows. First, fuel from the common rail 10 is supplied to the high pressure chamber 32 via the fuel passage 40 and further to the pressure increasing chamber 34 via the branch passage 47. Further, the servo valve 50 controlled by the ECU 60 is set to the supply side, and fuel is introduced into the first intermediate chamber 33-1 through the fuel passage 42. The fuel introduced into the first intermediate chamber 33-1 is further introduced into the second intermediate chamber 33-2 via the communication path 36.

  In a state where fuel is filled and balanced in the high pressure chamber 32, the first intermediate chamber 33-1, the second intermediate chamber 33-2, and the pressure increasing chamber 34, the pressure of the high pressure chamber 32 located on the upper side The total pressure of the first intermediate chamber 33-1, the second intermediate chamber 33-2, and the pressure increasing chamber 34 on the lower side is balanced.

  As described above, the pressure intensifier generally increases the fuel pressure in the pressure increasing chamber by returning the fuel in the intermediate chamber (withdrawing the fuel in the intermediate chamber to empty it). The pressure intensifier 30A according to the first embodiment includes the two intermediate chambers (33-1, 33-2) as described above, and returns the fuel according to the pressure of the fuel supplied from the common rail (fuel). The intermediate chamber is changed. This point will be described more specifically.

For example, when the diesel engine is operated with a light load, the pressure of the fuel stored in the common rail 10 is also relatively low. In such a case, there is often no need for fuel injection with a significantly increased pressure. In consideration of such points, the spring coefficient of the spring 39C of the pressure regulating valve 39 is set. The spring coefficient of the spring 39C is set so that the valve body 39V is maintained in the closed state when the fuel pressure from the common rail 10 is relatively low. Therefore, when the pressure of the fuel supplied from the common rail 10 is low, only the fuel in the first intermediate chamber 33-1 is returned when the servo valve 50 is switched to return (return) the fuel to the fuel passage 42. The fuel in the second intermediate chamber 33-2 is maintained as it is. At this time, the fuel in the pressure increasing chamber 34 is pressurized based on the area ratio of the small diameter portion 35SD and the medium diameter portion 35MD. Specifically, since the diameter of the small diameter portion 35SD is D1 and the diameter of the medium diameter portion 35MD is D2, the pressure increase ratio is (D2 / D1) ² . This pressure increase ratio is a smaller value than the pressure increase ratio in the case where there is one intermediate chamber as in the prior art. And since only the fuel in the 1st intermediate chamber 33-1 will return, it can also suppress about the return amount (return amount) of a fuel. Note that the return amount / the injection amount ^{= (D2 2 -D1 2) /} D1 2 in this case.

  As described above, in the fuel injection control system 1A, when the fuel pressure of the common rail 10 is relatively low and only the fuel in the first intermediate chamber 33-1 is returned, a small amount of fuel return is performed with a pressure increase ratio smaller than the conventional one. Amount. That is, in the prior art, since one large intermediate chamber was set, the pressure was forcibly increased to a high pressure increase ratio, and the amount of fuel returned was large. On the other hand, the fuel injection control system 1A can form a state in which the pressure increase ratio is suppressed and the fuel return amount is also suppressed.

  On the other hand, for example, when a diesel engine is operated at a high load, the pressure of the fuel stored in the common rail 10 becomes relatively high, and it is necessary to increase the pressure sufficiently and inject the fuel. In this case, since the pressure regulating valve 39 is opened, the fuel flows in the communication passage 37. Therefore, when the pressure of the fuel supplied from the common rail 10 is high, the first intermediate chamber 33-1 and the second intermediate chamber are switched when the servo valve 50 is switched to return (return) the fuel to the fuel passage 42. The fuel in 33-2 will be returned.

At this time, the fuel in the pressure increasing chamber 34 is greatly increased based on the area ratio between the small diameter portion 35SD and the large diameter portion 35BD. Specifically, since the diameter of the small diameter portion 35SD is D1 and the diameter of the large diameter portion 35BD is D3, the pressure increase ratio is (D3 / D1) ² . In this state, the fuel in the first intermediate chamber 33-1 and the second intermediate chamber 33-2 returns, and the fuel in the pressure-increasing chamber 34 can be most increased as in the conventional case. Note that the return amount / the injection amount ^{= (D3 2 -D1 2) /} D1 2 in this case.

  As described above, in the fuel injection control system 1A, when the fuel pressure in the common rail 10 is relatively high and the fuel in the first intermediate chamber 33-1 and the second intermediate chamber 33-2 is returned, the fuel injection control system 1A increases as in the conventional case. A pressure ratio can also be obtained.

  As is apparent from the above description, the fuel injection control system 1A according to the first embodiment has a pressure increase adjustment mechanism (communication) that connects a plurality of formed intermediate chambers in accordance with the pressure of the fuel stored in the common rail 10. (Including the passage 37 and the pressure regulating valve 39), the fuel injection pressure can be changed to a suitable one according to the state of the diesel engine. Therefore, unnecessary pressure increase of the fuel and generation of the fuel return amount can be suppressed as compared with the conventional case.

Hereinafter, the fuel injection control system 1B according to the second embodiment will be described. The schematic configuration of the fuel injection control system 1B is the same as that of FIG. 1 shown for the fuel injection control system 1A of the first embodiment, and only the structure of the intensifier employed is different. Therefore, in the second embodiment, a pressure intensifier 30B included in the fuel injection control system 1B will be described. FIG. 3 is a diagram specifically showing the structure of a pressure intensifier 30B applied to the fuel injection control system 1B. In FIG. 3, the same parts as those of the pressure intensifier 30 </ b> A according to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The structure of the medium diameter portion 35CMD of the second embodiment is different from the structure of the medium diameter portion 35MD of the first embodiment. In the case of Example 1, the communication path 37 which connects the 1st intermediate chamber 33-1 and the 2nd intermediate chamber 33-2 was provided, and the pressure regulation valve 39 was arrange | positioned here. And it was comprised so that the pressure increase ratio may be changed by opening the pressure regulation valve 39 according to the fuel pressure of the common rail 10 reflecting the state of a diesel engine.

  In contrast to the first embodiment, the medium diameter portion 35CMD of the piston 35 of the second embodiment is not formed with a communication path that allows the first intermediate chamber 33-1 and the second intermediate chamber 33-2 to communicate with each other. . Instead of the communication path, a communication groove 55 is formed along the axial direction (vertical direction in FIG. 3) on the peripheral surface of the medium diameter portion 35CMD. FIG. 3 illustrates a case where four communication grooves 55 are provided around the axis.

  In the case of the present embodiment, the height position (position in the axial direction) of the medium diameter portion 35CMD varies depending on the lift amount of the piston 35. A communication groove 55 is formed on the outer periphery of the medium diameter portion 35CMD. The communication groove 55 is set so that the first intermediate chamber 33-1 and the second intermediate chamber 33-2 communicate with each other when the lift amount becomes larger than a certain level. FIG. 4 shows a case where the lift amount of the piston 35 of the intensifier 30B is different. FIG. 4A shows a case where the lift amount is small, and FIG. 4B shows a case where the lift amount is large. In the case of FIG. 4A, the lift amount of the piston 35 is small, and the communication groove 55 does not connect (connect) the first intermediate chamber 33-1 and the second intermediate chamber 33-2 as indicated by a circle CR1. On the other hand, in the case of FIG. 4B, the lift amount of the piston 35 is large, and the communication groove 55 communicates between the first intermediate chamber 33-1 and the second intermediate chamber 33-2 as indicated by a circle CR2. Connecting.

  As described above, in the second embodiment, a state where the first intermediate chamber 33-1 and the second intermediate chamber 33-2 are communicated and a state where they are not communicated are formed according to the lift amount of the piston 35. In the pressure increasing operation in a state where the intermediate chambers are not communicated with each other, the fuel only in the first intermediate chamber 33-1 is removed (returned), and the pressure is increased with a relatively small pressure increasing ratio. This corresponds to the case where low pressure fuel is supplied from the common rail 10 in the first embodiment. The second embodiment corresponds to the case where the lift amount of the piston 35 is small as described above. This corresponds to the case where the diesel engine is in a light load state and the fuel injection amount can be suppressed, and the lift amount of the piston 35 is small.

  This corresponds to the case where high pressure fuel is supplied from the common rail 10 in the first embodiment. A large lift amount corresponds to a case where the diesel engine is in a medium / high load state and there is a request for an injection amount of a certain amount or more. FIG. 5 is a diagram summarizing images of fuel injection rates for the second embodiment. When the lift amount of the piston 35 is small and the first intermediate chamber 33-1 and the second intermediate chamber 33-2 are not communicated with each other, the injection amount is small. When the lift amount of the piston 35 is larger than a certain value and the position where the first intermediate chamber 33-1 and the second intermediate chamber 33-2 are communicated with each other, the injection amount becomes large.

  As is apparent from the above description, the fuel injection control system 1B of the second embodiment has a pressure increase adjustment mechanism (including the communication groove 55) that allows a plurality of intermediate chambers to communicate according to the lift amount of the piston 35. Therefore, the fuel injection pressure can be changed to a suitable one according to the state of the diesel engine. Therefore, in the case of the present embodiment, as in the case of the first embodiment, unnecessary fuel pressure increase and fuel return amount generation can be suppressed as compared with the conventional case.

  In the above-described embodiment, the case where two pistons are formed as a two-stage piston to facilitate understanding of the invention has been described. However, three or more intermediate chambers are formed using a piston having a three-stage structure or more. It is good also as a structure. In this way, the pressure increase ratio can be changed in multiple stages.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is the figure which showed the schematic structure of the fuel-injection control system which concerns on Example 1 applied to the diesel engine. It is the figure which showed concretely the structure of the pressure booster typically shown in FIG. It is the figure which showed concretely the structure of the pressure booster applied to the fuel-injection control system which concerns on Example 2. FIG. It is shown in the case where the lift amount of the piston is different, (A) shows a case where the lift amount is small, and (B) shows a case where the lift amount is large. It is the figure which put together the image of the fuel injection rate about the present Example 2. It is the figure which showed typically the relationship between the conventional pressure booster 110 and the injection nozzle 120. FIG.

Explanation of symbols

1 (1A, 1B) Fuel injection control system 10 Common rail (pressure accumulator)
20 Fuel injection nozzle 30 (30A, 30B) Intensifier 31 Cylinder 33 Intermediate chamber 33-1 First intermediate chamber 33-2 Second intermediate chamber 37 Communication path 39 Pressure regulating valve (valve device)
35 Piston 55 Communication groove

Claims (3)

A pressure accumulator for storing fuel in a pressurized state, a fuel injection nozzle for injecting fuel supplied from the pressure accumulator, and a pressure intensifier arranged between the pressure accumulator and the fuel injection nozzle to increase the fuel A fuel injection control system for an internal combustion engine,
The pressure intensifier has a plurality of stepped portions that reciprocate in the axial direction under the pressure of the fuel, and an inner wall is formed to correspond to the outer shape of the piston, and the movement of the piston Including a cylinder formed to allow
In accordance with the state of the internal combustion engine, it further includes a pressure increase adjustment mechanism that changes the fuel pressure increase ratio by communicating a plurality of intermediate chambers formed between the stepped portion of the piston and the inner wall of the cylinder. A fuel injection control system for an internal combustion engine. The pressure-increasing adjustment mechanism includes a communication path that connects a plurality of the intermediate chambers, and a valve device that opens and closes the communication path according to the pressure of fuel supplied from the pressure accumulator. The fuel injection control system for an internal combustion engine according to claim 1. The pressure increase adjusting mechanism includes a communication groove formed on the surface of the piston,
2. The fuel injection control system for an internal combustion engine according to claim 1, wherein the communication groove communicates a plurality of the intermediate chambers formed in accordance with a lift amount of the piston.

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