JPWO2015108138A1 - Crosshead engine - Google Patents

Abstract

The crosshead type engine includes a cylinder, a piston head that slides in the cylinder, and a piston rod (112b) having one end fixed to the piston head, and a piston that reciprocates within the cylinder, and a piston rod The cross head is fixed to the other end of the piston, and reciprocates integrally with the piston. The connecting rod is supported by the cross head at one end. The piston rod is connected to the first rod disposed on one end side, the second rod disposed on the other end side, the first rod and the second rod, and supplied to the inside. And a variable portion whose length in the reciprocating direction of the piston is variable depending on the pressure of the working fluid.

Description

The present invention relates to a crosshead engine in which a crosshead is fixed to a piston rod.
This application claims priority based on Japanese Patent Application No. 2014-008101 for which it applied to Japan on January 20, 2014, and uses the content here.

In a crosshead type engine that is widely used in marine engines, a crosshead is provided at the end of a piston rod of a piston. The connecting rod (connecting rod) connects the crosshead and the crankshaft, and the reciprocating motion of the crosshead is converted into the rotational motion of the crankshaft.

The engine of Patent Document 1 is such a crosshead type engine, in which a hydraulic cylinder chamber is provided in the piston head, and an oil passage communicating from one end to the other end on the piston head side is provided in the piston rod. Provided on the other end side of the piston rod is a pilot valve box in which a pilot valve for controlling the hydraulic pressure of the hydraulic oil supplied to the oil passage is incorporated. And the length of the piston is made variable by switching the hydraulic pressure in the hydraulic cylinder chamber.
Further, Patent Document 2 discloses a crosshead type engine having a piston rod provided with a hydraulic shock absorbing mechanism.

Japanese Patent Publication No. 63-52221 Japanese Unexamined Patent Publication No. 63-25331

By the way, if the pressure in the combustion chamber becomes too high, abnormal combustion occurs or the amount of NOx (nitrogen oxide) contained in the exhaust gas increases. In this case, the substantial compression ratio of the engine can be lowered by control such as delaying the closing timing of the exhaust valve. However, since the amount of air taken into the engine is reduced and the excess air ratio is reduced, the effect of suppressing abnormal combustion and the amount of NOx may be limited.

In the engine described in Patent Document 1 described above, since the mechanical compression ratio can be lowered, it is considered effective for suppressing abnormal combustion and the amount of NOx. A mechanism to make the length variable must be arranged. In addition, the structure is complicated, for example, it is necessary to arrange a pilot valve box on the other end side of the piston rod.
In addition, since the hydraulic cylinder chamber is close to the combustion chamber and exposed to high temperature by heat transfer from the combustion chamber, the durability of the sliding portion in the hydraulic cylinder chamber is reduced.

In view of such problems, the present invention provides a crosshead engine that has a high durability and a simple structure, can vary the mechanical compression ratio, and can suppress abnormal combustion and NOx amount. The purpose is that.

In order to solve the above problems, a crosshead type engine of the present invention includes a cylinder, a piston head that slides in the cylinder, and a piston rod having one end fixed to the piston head. A piston that reciprocates, a crosshead that is fixed to the other end of the piston rod and reciprocates integrally with the piston, a connecting rod that is supported by the crosshead at one end, and a connecting rod that is connected to the connecting rod. A crankshaft that rotates in conjunction with the reciprocating movement. Furthermore, the piston rod connects the first rod disposed on one end side, the second rod disposed on the other end side, the first rod and the second rod, and the working fluid supplied to the inside. And a variable portion whose length in the reciprocating direction of the piston is variable depending on the pressure.

The variable portion may be configured by a hydraulic cylinder using hydraulic oil as a working fluid.

You may further provide the control part which switches the fuel burned in a cylinder with liquid fuel and gaseous fuel.

According to the crosshead type engine of the present invention, it is possible to suppress abnormal combustion and the amount of NOx by making the mechanical compression ratio variable with a highly durable and simple structure.

It is a figure which shows the whole structure of a uniflow scavenging type 2 cycle engine. It is a figure which shows operation | movement of each control part. It is a figure which shows operation | movement of each control part. It is sectional drawing of a piston rod. It is sectional drawing of a piston rod.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

In the following embodiments, it is possible to selectively execute any one of a gas operation mode in which fuel gas that is gaseous fuel is mainly burned and a diesel operation mode in which fuel oil that is liquid fuel is burned. A so-called dual fuel type engine will be described. Further, a case where one cycle is two cycles (two strokes) and a uniflow scavenging type in which gas flows in one direction inside the cylinder will be described. However, the type of engine to which the present invention is applied is not limited to the dual fuel type, the two-cycle type, and the uniflow scavenging type, and may be a crosshead type engine.

FIG. 1 is a diagram showing an overall configuration of a uniflow scavenging two-cycle engine 100 (crosshead engine). The uniflow scavenging two-cycle engine 100 of the present embodiment is used for, for example, ships. Specifically, the uniflow scavenging two-cycle engine 100 includes a cylinder 110, a piston 112, a crosshead 114, a connecting rod 116, a crankshaft 118, a pilot injection valve 120, a combustion chamber 122, and an exhaust port 124. An exhaust valve drive device 126, an exhaust valve 128, a scavenging port 130, a scavenging chamber 132, a fuel injection port 134, a rotary encoder 136, a governor 150 (governor), and a fuel injection control unit 152 ( A control unit), an exhaust control unit 154, and a hydraulic control unit 156.

In the uniflow scavenging two-cycle engine 100, the piston 112 reciprocates in the cylinder 110 through four consecutive strokes such as intake (supply), compression, combustion, and exhaust. The piston 112 includes a piston head 112a that slides in the cylinder 110, and one end of a piston rod 112b is fixed to the piston head 112a. A cross head 114 is fixed to the other end of the piston rod 112b, and the cross head 114 reciprocates together with the piston 112. The cross head 114 is restricted from moving in a direction (left and right direction in FIG. 1) perpendicular to the stroke direction (reciprocating direction) of the piston 112 by the cross head shoe 114a.

The cross head 114 pivotally supports one end of the connecting rod 116. The other end of the connecting rod 116 is connected to the crankshaft 118 so that the crankshaft 118 rotates with respect to the connecting rod 116. As a result, when the cross head 114 reciprocates as the piston 112 reciprocates, the crankshaft 118 rotates in conjunction with the reciprocation.

In such a crosshead type engine, the stroke in the cylinder 110 can be formed relatively long, and the side pressure acting on the piston 112 can be received by the crosshead 114. Therefore, the uniflow scavenging two-cycle engine 100 Output can be increased. Furthermore, since the cylinder 110 and a crank chamber (not shown) in which the crosshead 114 is accommodated are isolated, deterioration of the lubricating oil in the crank chamber can be prevented even when low quality fuel is used.

The pilot injection valve 120 is provided in the cylinder head 110a above the top dead center of the piston 112.

In the gas operation mode, the pilot injection valve 120 injects an appropriate amount of fuel oil at a desired point in the engine cycle. Such fuel oil is spontaneously ignited by the heat of the combustion chamber 122 surrounded by the cylinder head 110a, the cylinder liner in the cylinder block 110b, and the piston 112, and burns in a short time, so that the temperature of the combustion chamber 122 is extremely reduced. Make it high.

As a result, the premixed gas containing the fuel gas flowing in from the fuel injection port 134 described later can be reliably burned at a desired timing. The piston 112 reciprocates mainly by the expansion pressure due to the combustion of fuel gas.

On the other hand, in the diesel operation mode, the pilot injection valve 120 injects a larger amount of fuel oil than the fuel oil injection amount in the gas operation mode. The piston 112 reciprocates by an expansion pressure caused by combustion of fuel oil, not fuel gas.

The exhaust port 124 is an opening provided in the cylinder head 110 a above the top dead center of the piston 112, and is opened and closed to exhaust the exhaust gas after combustion generated in the cylinder 110. The exhaust valve drive device 126 opens and closes the exhaust port 124 by sliding the exhaust valve 128 up and down at a predetermined timing. The exhaust gas exhausted through the exhaust port 124 in this way is supplied to the turbine side of a turbocharger (not shown) and then exhausted to the outside.

The scavenging port 130 is a hole penetrating from the inner peripheral surface (the inner peripheral surface of the cylinder block 110 b) on the lower end side of the cylinder 110 to the outer peripheral surface, and a plurality of scavenging ports 130 are provided over the entire periphery of the cylinder 110. Then, the active gas is sucked into the cylinder 110 from the scavenging port 130 in accordance with the sliding motion of the piston 112. Such an active gas includes an oxidizing agent such as oxygen and ozone, or a mixture thereof (for example, air). The scavenging chamber 132 is filled with active gas (for example, air) pressurized by a compressor of a supercharger (not shown), and the active gas is sucked from the scavenging port 130 due to the differential pressure in the scavenging chamber 132 and the cylinder 110. Is done. The pressure in the scavenging chamber 132 can be substantially constant, but when the pressure in the scavenging chamber 132 changes, a pressure gauge is provided in the scavenging port 130, and the fuel gas injection amount, etc., according to the measured value, etc. Other parameters may be controlled.

The fuel injection ports 134 are a plurality of openings provided at predetermined intervals in the circumferential direction on the inner peripheral surface of the cylinder 110. The fuel injection valve 134 a is disposed in each fuel injection port 134. In the diesel operation mode described above, the fuel injection valve 134a is not opened and fuel gas is not injected.

On the other hand, in the gas operation mode, the fuel injection valve 134a receives a command from the fuel injection control unit 152 and injects, for example, fuel gas obtained by gasifying LNG (liquefied natural gas). Thus, the fuel gas is supplied into the cylinder 110. Further, the fuel gas is not limited to LNG, and for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, or the like can be applied.

The rotary encoder 136 detects an angle signal indicating the rotation angle of the crankshaft 118 (hereinafter referred to as a crank angle signal).

The governor 150 derives the fuel injection amount based on the engine output command value and the operation mode input from the host controller and the engine speed based on the crank angle signal from the rotary encoder 136, and determines the fuel injection amount and the operation mode. Is output to the fuel injection control unit 152.

The fuel injection control unit 152 controls the pilot injection valve 120 and the fuel injection valve 134 a based on the fuel injection amount and information indicating the operation mode input from the governor 150 and the crank angle signal from the rotary encoder 136.

The exhaust control unit 154 outputs an exhaust valve operation signal to the exhaust valve driving device 126 based on the fuel injection amount from the fuel injection control unit 152, the signal relating to the operation mode, and the crank angle signal from the rotary encoder 136. .

The hydraulic control unit 156 controls the hydraulic pump 158 based on the operation mode input from the host control device. The hydraulic pump 158 communicates with the inside of the piston rod 112b and supplies hydraulic oil to the inside of the piston rod 112b.

Next, the operation of each control unit in the engine cycle of the above-described uniflow scavenging two-cycle engine 100 will be described.

2A and 2B are diagrams showing the operation of each control unit. FIG. 2A shows a timing chart in the gas operation mode, and FIG. 2B shows a timing chart in the diesel operation mode.

In the gas operation mode, as shown in FIG. 2A, in the exhaust stroke after the combustion stroke, the exhaust port 124 and the scavenging port 130 are closed, and the combustion chamber 122 (inside the cylinder 110) is filled with exhaust gas. Yes.

When the piston 112 descends and approaches the bottom dead center due to the explosion pressure generated by the combustion action of the combustion chamber 122, the exhaust control unit 154 opens the exhaust valve 128 through the exhaust valve driving device 126 (t1 shown in FIG. 2A), Subsequently, the scavenging port 130 is opened according to the sliding motion of the piston 112 (t2 shown in FIG. 2A). Then, the active gas is sucked from the scavenging port 130. The active gas rises in the cylinder 110 and pushes the exhaust gas in the combustion chamber 122 (in the cylinder 110) from the exhaust port 124.

In the compression stroke in which the piston 112 rises from the bottom dead center toward the top dead center, the scavenging port 130 is closed, and the suction of the active gas is stopped.

At this time, the exhaust control unit 154 maintains the exhaust valve 128 in the open state, and the exhaust gas in the combustion chamber 122 (inside the cylinder 110) is continuously discharged from the exhaust port 124 by the rise of the piston 112. .

Then, while the piston 112 is sliding toward the top dead center (t3 shown in FIG. 2A), the fuel injection control unit 152 receives information indicating the fuel injection amount input from the governor 150, and the rotary encoder 136. Based on the engine speed derived from the crank angle signal from the engine, the fuel injection valve 134a is opened, fuel is injected into the combustion chamber 122 from the fuel injection port 134, and then the fuel injection valve 134a is closed. I speak.

Thereafter, when the piston 112 further rises, the exhaust control unit 154 closes the exhaust valve 128 and closes the exhaust port 124 (t4 shown in FIG. 2A). Then, before the piston 112 reaches top dead center, the fuel injection control unit 152 opens the pilot injection valve 120 and injects fuel oil to induce combustion of fuel gas (t5 shown in FIG. 2A). .

As shown in FIG. 2B, in the diesel operation mode, the fuel injection control unit 152 does not open the fuel injection valve 134a. Before the piston 112 reaches top dead center, the fuel injection control unit 152 opens the pilot injection valve 120 and injects and burns fuel oil (t5 shown in FIG. 2B). At this time, the opening period of the pilot injection valve 120 is longer than the opening period of the pilot injection valve 120 in the gas operation mode, and as a result, the fuel oil injection amount increases.

As described above, the fuel injection control unit 152 switches the fuel to be burned in the combustion chamber 122 between the fuel oil and the fuel gas according to the operation mode.

Then, as fuel gas or fuel oil burns in the combustion chamber 122, exhaust, intake, compression, and combustion stroke are repeated as described above.

Here, the case where the opening timing of the pilot injection valve 120 is the same in the diesel operation mode and the gas operation mode has been described (t5 shown in FIGS. 2A and 2B). However, in order to make the opening period of the pilot injection valve 120 in the diesel operation mode longer than the opening period of the pilot injection valve 120 in the gas operation mode, the opening of the pilot injection valve 120 in the diesel operation mode is performed in the gas operation mode. It may be earlier than the pilot injection valve 120 is opened.

By the way, an appropriate compression ratio differs between the diesel operation mode and the gas operation mode. In this embodiment, the compression ratio is variable by improving the structure of the piston rod 112b. Hereinafter, the specific structure of the piston rod 112b will be described in detail.

3A and 3B are sectional views of the piston rod 112b. FIG. 3A shows the piston rod 112b in a normal state, and FIG. 3B shows the piston rod 112b in a contracted state. 3A and 3B, the upper side is the side where the piston head 112a is arranged, and the lower side is the side where the cross head 114 is arranged.

As shown in FIGS. 3A and B, the piston rod 112b includes a first rod 160 and a second rod 162. The first rod 160 is disposed on the piston head 112a side (one end side), and the second rod 162 is disposed on the cross head 114 side (the other end side).

The first rod 160 is an annular member having a through hole 160a penetrating in the axial direction of the piston rod 112b. 3A and B, the lower end surface 160b of the first rod 160 is formed with a protruding portion 160c protruding in the axial direction from the end surface 160b, and the through hole 160a is centered on the protruding portion 160c. It penetrates.

Similar to the first rod 160, the second rod 162 is an annular member having a through hole 162a penetrating in the axial direction. The through-hole 162a of the second rod 162 has a large-diameter portion 162c extending to the upper end surface 162b in FIGS. 3A and B, an inner diameter smaller than the large-diameter portion 162c, and from the large-diameter portion 162c in FIGS. A small-diameter portion 162d continuous to the lower side is included. A step surface 162e is formed at the boundary between the large diameter portion 162c and the small diameter portion 162d.

The inner diameter of the large-diameter portion 162c of the second rod 162 is formed slightly larger than the outer diameter of the protruding portion 160c of the first rod 160, and the protruding portion 160c of the first rod 160 is shown in FIGS. It is inserted into the large diameter portion 162c of the second rod 162 from above.

Inside the through hole 160a of the first rod 160 and the through hole 162a of the second rod 162, a hydraulic cylinder 164 (variable part) extending on the axis of the piston rod 112b across the through hole 160a and the through hole 162a is arranged. Has been. The hydraulic cylinder 164 includes a base portion 166 and a plunger portion 168, and connects the first rod 160 and the second rod 162.

The base portion 166 is a cylindrical member, and is formed with a sliding hole 166a extending in the axial direction. An oil hole 166b penetrating to the outside of the base portion 166 is provided on the bottom surface (the upper end surface in FIGS. 3A and 3B) of the sliding hole 166a. A hydraulic hose (not shown) is connected to the oil hole 166b and communicates with the hydraulic pump 158.

The plunger portion 168 is a columnar member having an outer diameter substantially equal to that of the base portion 166. 3A and B, the small-diameter portion 168a formed on the upper side of the plunger portion 168 is a portion whose outer diameter is slightly smaller than the inner diameter of the sliding hole 166a of the base portion 166. It is inserted into the sliding hole 166a from below and inside.

The first rod 160 is provided with a support hole 160d passing through the first rod 160 in the radial direction above the end surface 160b. Two support holes 160d are provided in the radial direction of the first rod 160, and both ends of the base support portion 170 are inserted into these support holes 160d.

The base support portion 170 is a plate-like member, and has an insertion hole 170a through which the base portion 166 is inserted at the center thereof. The base portion 166 is fixed to the base support portion 170 in a state where the base portion 166 is inserted into the insertion hole 170 a of the base support portion 170.

The small diameter portion 162d of the second rod 162 is provided with a support hole 162f penetrating in the radial direction. Two support holes 162f are provided in the radial direction of the second rod 162, and both ends of the plunger support portion 172 are inserted into these support holes 162f, respectively.

The plunger support portion 172 is a plate-like member, and has an insertion hole 172a through which the plunger portion 168 is inserted at the center thereof. The plunger portion 168 is fixed to the plunger support portion 172 in a state of being inserted through the insertion hole 172a of the plunger support portion 172.

That is, the base portion 166 is fixed to the first rod 160 by the base support portion 170, and the plunger portion 168 is fixed to the second rod 162 by the plunger support portion 172.

The hydraulic oil pressurized by the hydraulic pump 158 flows into the sliding hole 166a of the base portion 166 from the oil hole 166b, and the plunger portion 168 is pressed downward by the hydraulic pressure of the hydraulic oil. Further, a force in the direction of compressing the piston 112 acts on the piston 112 due to an expansion pressure accompanying combustion of fuel gas or fuel oil in the combustion chamber 122.

And if the hydraulic pressure by the hydraulic pump 158 falls, the base part 166 and the plunger part 168 will move in the direction which approaches relatively from the state of FIG. 3A to the state of FIG. 3B.

When the hydraulic cylinder 164 contracts, the first rod 160 and the second rod 162 fixed to the base portion 166 and the plunger portion 168 also move in conjunction with each other via the base support portion 170 and the plunger support portion 172, respectively. The distance D between the stepped surface 162e formed at the boundary between the large diameter portion 162c and the small diameter portion 162d and the protrusion 160c is reduced.

Further, when the hydraulic pressure by the hydraulic pump 158 is increased, the base portion 166 and the plunger portion 168 are moved in a relatively separated direction from the state of FIG. 3B to the state of FIG. 3A. Thus, the hydraulic cylinder 164 extends.

When the hydraulic cylinder 164 extends, the first rod 160 and the second rod 162 fixed to the base portion 166 and the plunger portion 168 also move in conjunction with each other via the base support portion 170 and the plunger support portion 172, respectively. Then, the distance D between the stepped surface 162e formed at the boundary between the large diameter portion 162c and the small diameter portion 162d and the protruding portion 160c is increased.

In this way, the piston rod 112b extends as the hydraulic cylinder 164 extends, and the piston rod 112b contracts as the hydraulic cylinder 164 contracts. As described above, the piston rod 112b is configured such that the length of the piston 112 in the stroke direction is variable.

Since the uniflow scavenging two-cycle engine 100 is a crosshead engine, the crosshead 114 receives the force in the direction perpendicular to the stroke direction transmitted from the connecting rod 116. Therefore, since the piston rod 112b and the hydraulic cylinder 164 are not easily subjected to a force in a direction perpendicular to the stroke direction, the hydraulic cylinder 164 can be expanded and contracted by hydraulic pressure.

In the gas operation mode, the oil pressure control unit 156 reduces the oil pressure and contracts the hydraulic cylinder 164 so that the compression ratio is low (see FIG. 3B). The hydraulic cylinder is increased and the hydraulic cylinder 164 is extended so as to achieve a high compression ratio (see FIG. 3A).

As a result, in the gas operation mode, the occurrence of abnormal combustion and knocking and the amount of NOx contained in the exhaust gas are suppressed. In the diesel operation mode, it is possible to achieve high efficiency by a high compression ratio.

In addition, when the substantial compression ratio is lowered by delaying the closing timing of the exhaust valve 128, the excess air ratio is reduced, but in this embodiment, the piston rod 112b is contracted to lower the compression ratio. Therefore, the occurrence of abnormal combustion and knocking can be suppressed.

In addition, since the length in the stroke direction is variable in the piston 112, not the piston head 112a, in the piston rod 112b, the hydraulic cylinder 164 is disposed at a position farther from the combustion chamber 122 than the piston head 112a. . As a result, the high temperature of the hydraulic cylinder 164 and hydraulic oil is suppressed, and it becomes possible to improve their durability.

Further, by adjusting the hydraulic pressure in the hydraulic cylinder 164 installed inside the through hole 160a of the first rod 160 and the through hole 162a of the second rod 162, the length of the piston rod 112b in the stroke direction becomes variable. Yes. Therefore, for example, unlike Patent Document 2 described above, the periphery of the first rod 160 and the second rod 162 is covered with a cylinder, and hydraulic oil is supplied to the space surrounded by the first rod 160 and the second rod 162 and the cylinder. Thus, it is not necessary to slide the first rod 160 and the second rod 162 within the cylinder.
That is, there is no sliding surface of the first rod 160 and the second rod 162 with respect to the cylinder as a sealing surface of the hydraulic oil, and the hydraulic oil is affected by the reciprocating motion of the first rod 160 and the second rod 162. Hateful. Therefore, the sealing performance of the hydraulic oil is improved, and the reliability of the piston rod 112b whose length in the stroke direction is variable is improved.

When abnormal combustion occurs and the pressure in the combustion chamber 122 becomes excessively high, the compressive force acting on the hydraulic cylinder 164 increases and the hydraulic cylinder 164 is automatically contracted. As a result, since the compression ratio is lowered, abnormal combustion is calmed down. As described above, in the uniflow scavenging two-cycle engine 100, when abnormal combustion occurs, the compression ratio is automatically lowered to perform abnormal combustion without performing processing such as detection of abnormal combustion or control of the hydraulic pressure control unit 156. Sedation can be achieved.

In the above-described embodiment, the case where the variable portion is configured by the hydraulic cylinder 164 has been described. However, the variable portion is connected to the first rod 160 and the second rod 162, and the length in the stroke direction is increased by the pressure of the working fluid. The hydraulic cylinder 164 may be omitted as long as the mechanism is variable. For example, the variable portion may be constituted by a pneumatic cylinder using air instead of hydraulic oil as a working fluid, or may be constituted by an electric actuator. However, when the hydraulic cylinder 164 using hydraulic fluid as the hydraulic fluid is used, the hydraulic oil has a small volume change due to compression, so that the response is good and the piston rod 112b can be stably expanded and contracted.
Moreover, since the structure which connected the 1st rod 160 and the 2nd rod 162 with the hydraulic cylinder 164 is a simple structure, manufacturing cost is low and it is hard to break down.

Further, in the above-described embodiment, the case where the hydraulic control unit 156 controls the hydraulic pressure based on the operation mode and expands / contracts the length of the piston rod 112b has been described. However, for example, when the pressure in the combustion chamber 122 becomes too high, the hydraulic control unit 156 may reduce the hydraulic pressure and contract the piston rod 112b. According to such control, it is possible to suppress the occurrence of abnormal combustion and knocking and the amount of NOx.

In the above-described embodiment, the case where the hydraulic pump 158 is a dedicated pump that supplies hydraulic oil to the piston 112 has been described. However, the hydraulic pump 158 may share a pump for circulating cooling oil for cooling the piston head 112 a in the cylinder 110. In this case, during normal operation of the hydraulic pump 158, the cooling oil of the piston head 112a is supplied into the cylinder 110, and the hydraulic oil is supplied to the piston 112 of the above-described embodiment only when the length of the piston rod 112b is expanded and contracted. In this way, the number of installed pumps can be reduced, and the manufacturing cost can be reduced.

As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. The

The present invention can be used for a crosshead engine in which a crosshead is fixed to a piston rod.

100 Uniflow scavenging type 2-cycle engine (crosshead type engine)
110 Cylinder 112 Piston 112a Piston head 112b Piston rod 114 Crosshead 116 Connecting rod 118 Crankshaft 152 Fuel injection control unit (control unit)
160 1st rod 162 2nd rod 164 Hydraulic cylinder (variable part)

Claims (4)

A cylinder,
A piston head that slides in the cylinder; and a piston rod that has one end fixed to the piston head; and a piston that reciprocates in the cylinder;
A crosshead fixed to the other end of the piston rod and reciprocating integrally with the piston;
A connecting rod having one end supported by the crosshead;
A crankshaft connected to the connecting rod and rotating in conjunction with the reciprocating movement of the piston and the crosshead,
The piston rod connects the first rod disposed on the one end side, the second rod disposed on the other end side, the first rod and the second rod, and is supplied to the inside. A crosshead type engine comprising: a variable portion whose length in the reciprocating direction of the piston is variable depending on the pressure of the working fluid. The crosshead engine according to claim 1, wherein the variable portion is configured by a hydraulic cylinder using hydraulic oil as the hydraulic fluid. The crosshead engine according to claim 1, further comprising a control unit that switches between fuel to be burned in the cylinder between liquid fuel and gaseous fuel. The crosshead type engine according to claim 2, further comprising a control unit that switches a fuel to be burned in the cylinder between a liquid fuel and a gaseous fuel.

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