Patent Description:
A dual fuel engine employed in ship uses natural gas and heavy oil as a fuel source. A fuel gas supply system (FGSS) is designed to supply liquefied gas to the dual fuel engine. Accordingly, the high pressure gas injection type dual fuel engine essentially requires a high pressure pump for FGSS to supply high pressure gas.

For example, the high pressure pump for FGSS as disclosed by <CIT> typically includes a plurality of cylinders for one crankshaft, wherein a connecting rod and a piston mounted in each cylinder are operated to compress/discharge high pressure fuel by the reciprocating motion in the cylinder. However, in the case of this type high pressure pump, since the connecting rod and the piston are structurally connected to the crankshaft, it fails to selectively control the operation of the connecting rod and the piston mounted in the cylinder. Accordingly, to check or inspect any error in the high pressure pump, it is necessary to install an extra high pressure pump.

As described above, since it is necessary to install the high pressure pump for operation and the extra high pressure pump in FGSS, it requires a space for installing the two high pressure pumps and an additional cost to install the two high pressure pumps.

<CIT> discloses a fuel injection pump arrangement for a dual-fuel internal combustion engine which comprises a pump body, at least one fuel chamber that is arranged inside the pump body, at least one reciprocating plunger that protrudes into the fuel chamber for pressurizing liquid fuel in the chamber, a plunger moving mechanism for establishing mechanical connection between the plunger and a rotating cam that drives the fuel injection pump, and means for breaking the mechanical connection between the plunger and the cam when the fuel injection pump is not used for pressurizing fuel. The invention also concerns a method for operating a dual-fuel engine.

The present disclosure is designed to solve the above-described problem, and therefore the present disclosure is directed to providing a gas supply pump for a ship dual fuel engine for enabling independent cylinder operation.

To achieve the above-described objective, a gas supply pump for a ship is provided according to claim <NUM>. Other optional and preferred features of the gas supply pump are set out in the dependent claims and in the following paragraphs in this section.

A plurality of the drive shafts are arranged side by side in a direction perpendicular to one camshaft, and the cam roller is disposed between the cam nose and the drive shaft of the camshaft.

A center of rotation of the cam nose is the same as a center of rotation of the camshaft, a radius of the cam nose is smaller than a radius of the camshaft, a radius of rotation of the cam nose corresponds to a radius of rotation of the camshaft, and when the camshaft rotates, the cam roller in close contact with the cam nose makes a linear reciprocating motion within a predetermined distance.

When the cam nose is located at a <NUM>° angle on the basis of a vertical direction by the rotation of the camshaft, the cam roller moves the compression direction of the piston, and when the cam nose is located at a <NUM>° angle by the rotation of the camshaft, the cam roller moves in the decompression direction of the piston.

The gas supply pump for a ship dual fuel engine further includes an integral connection member to integrally connect the cam roller and the drive shaft, wherein the cam roller is seated at one end of the integral connection member, the drive shaft is mounted at the other end, and a compression spring disposed around the drive shaft is fixed to an inner side of the integral connection member, and when the camshaft rotates, the cam roller and the drive shaft in close contact with the cam nose make a linear reciprocating motion together with the integral connection member.

A first seating portion and a second seating portion which form a predetermined space at one end of the drive shaft are provided at a coupled part of the drive shaft and the piston, the first seating portion is disposed in an inner direction of the drive shaft, the second seating portion is disposed in an outer direction of the drive shaft, an inertia moment damping member is disposed in the first seating portion, and one exposed surface of the inertia moment damping member is in close contact with the piston.

One surface of the inertia moment damping member in close contact with the piston has a convex surface shape with a radius of curvature, and when the moment of inertia of the camshaft is applied to the drive shaft, the moment of inertia applied to the drive shaft is allowed to spread out by the convex surface of the inertia moment damping member.

A diameter of the second seating portion is larger than a diameter of the first seating portion, the diameter of the first seating portion corresponds to a diameter of the piston, and a stopper is filled between a space between the second seating portion and the piston and is in close contact with the piston and an inner diameter of the second seating portion to prevent the piston from rotating.

A clamp may be provided at the coupled part of the drive shaft and the piston to protect the corresponding coupled part.

The liquefied gas compression device includes a liquefied gas supply passage in which the liquefied gas to be compressed is supplied to a suction valve, the suction valve configured to suck the liquefied gas from the liquefied gas supply passage and supply the sucked liquefied gas to a discharge valve when pressure of the piston is applied, and the discharge valve configured to discharge the liquefied gas supplied from the suction valve in a compressed state.

One end of the liquefied gas supply passage is connected to a liquefied gas supply port on one side of the gas supply pump, the other end is connected to a liquefied gas inlet port on one side of the suction valve, and the liquefied gas to be compressed is supplied to an internal space of the suction valve through the liquefied gas inlet port via the liquefied gas supply port and the liquefied gas supply passage.

An opening/closing member is provided around the suction valve to selectively open/close the liquefied gas inlet port, the opening/closing member is connected to a spring member around a bottom circumference of the suction valve and makes a linear reciprocating motion by compression and restoration of the spring member, when the opening/closing member moves in the compression direction by the compression of the spring member, the liquefied gas inlet port is opened, when the opening/closing member moves in the restoration direction by the restoration of the spring member, the liquefied gas inlet port is closed, and when the liquefied gas is supplied through the liquefied gas supply passage with the liquefied gas inlet port closed by the opening/closing member, the opening/closing member moves in the compression direction of the spring member by supply pressure of the liquefied gas, the liquefied gas inlet port is opened, and accordingly, the liquefied gas is supplied to the internal space of the suction valve.

The discharge valve is disposed in a discharge chamber, a spring member is provided at a lower end of the discharge valve and allows the discharge valve to make a linear reciprocating motion by compression and restoration of the spring member, an auxiliary chamber of a predetermined space is provided around a top circumference of the discharge chamber, a discharge inlet pipe is provided between the auxiliary chamber and the discharge valve, and the liquefied gas discharged from the suction valve is supplied to the discharge valve via the auxiliary chamber and the discharge inlet pipe in a sequential order.

The discharge valve is configured to close a suction valve outlet pipe when the spring member is restored, when the discharge valve moves in the compression direction of the spring member, a space is formed on top of the discharge chamber, and the suction valve outlet pipe is opened, when the space is formed on top of the discharge chamber by the movement of the discharge valve, the space on top of the discharge chamber is spatially connected to the suction valve outlet pipe and is also connected to the auxiliary chamber, and the liquefied gas discharged through the suction valve outlet pipe is supplied to the internal space of the discharge chamber via the auxiliary chamber and the discharge inlet pipe through the space on top of the discharge chamber.

When the liquefied gas is discharged through the suction valve, since the operating pressure of the piston is much higher than the supply pressure of the liquefied gas supplied to the liquefied gas supply passage, the liquefied gas inlet port is closed by the opening/closing member.

The gas supply pump for a ship dual fuel engine further includes a cam roller-drive shaft case on an outer side of the integral connection member to protect the integral connection member and guide the movement of the integral connection member, wherein the cam roller-drive shaft case has, on one side, a cutoff bolt through-hole into which a cutoff bolt is inserted and passed through, the integral connection member has, on one side, a cutoff bolt insertion groove, into which the cutoff bolt is inserted to a predetermined depth, and the cam nose and the cam roller are induced to be spaced apart from each other by inserting the cutoff bolt into the cutoff bolt insertion groove through the cutoff bolt through-hole.

A center of the cutoff bolt through-hole and a center of the cutoff bolt insertion groove are offset each other, and on the basis of the piston being perpendicular to the camshaft, the center of the cutoff bolt insertion groove is located at a slightly lower position than the center of the cutoff bolt through-hole, and the cutoff bolt insertion groove has a tapered shape having a decreasing radius with increasing depth, and has a difference 'd' between radii at an entrance and a lower surface of the cutoff bolt insertion groove by the tapered shape.

In the insertion of the cutoff bolt passing through the cutoff bolt through-hole into the cutoff bolt insertion groove, the cutoff bolt contacts a side of the cutoff bolt insertion groove having a tapered shape and moves inward of the cutoff bolt insertion groove along the side of the cutoff bolt insertion groove, and as the cutoff bolt moves inward of the cutoff bolt insertion groove, the integral connection member having the cutoff bolt insertion groove moves up, and the cam roller is spaced apart from the cam nose.

When one end of the cutoff bolt contacts the lower surface of the cutoff bolt insertion groove, the integral connection member moves up by the difference 'd' between the radii at the entrance and the lower surface of the cutoff bolt insertion groove, and the cam roller and the cam nose are spaced apart from each other by the length 'd'.

The gas supply pump for a ship dual fuel engine further includes a cam roller-drive shaft case on an outer side of the integral connection member to protect the integral connection member and guide the movement of the integral connection member, wherein a hollow cylindrical cutoff pin guide member is provided on one side of the cam roller-drive shaft case, the cutoff pin is inserted into the cutoff pin guide member such that the cutoff pin can move up or down, the cutoff pin guide member has a cutoff pin guide groove on one side, the cutoff pin guide groove includes a vertical guide groove and a horizontal guide groove spatially connected to each other, the vertical guide groove is extended from a first point to a second point on a vertical line, the horizontal guide groove is extended from the second point of the vertical guide groove to a third point in a horizontal direction, a cutoff pin guide pin is provided on one side of the cutoff pin and is disposed in the cutoff pin guide groove, when the cutoff pin guide pin vertically moves from the first point of the cutoff pin guide groove to the second point, the cutoff pin moves down by a corresponding distance, when the cutoff pin guide pin horizontally moves from the second point of the cutoff pin guide groove to the third point, the cutoff pin rotates by an angle between the second point and the third point, the cutoff pin has, on a lower surface, a cylindrical cam roller spacing protrusion having a smaller radius than the cutoff pin, a center of the cam roller spacing protrusion is eccentric from a center of a circle of the cutoff pin, and when the cutoff pin guide pin horizontally moves from the second point of the cutoff pin guide groove to the third point, the cam roller spacing protrusion on the lower surface of the cutoff pin rotates at a predetermined angle.

The cam roller-drive shaft case has, on one side, a cutoff pin through-hole into which the cutoff pin is inserted and passed through, the integral connection member has a cam roller spacing guide groove corresponding to the cutoff pin through-hole, when the cutoff pin guide pin is located at the second point, the cam roller spacing protrusion at the lower end of the cutoff pin is disposed in the cam roller spacing guide groove of the integral connection member, the cam roller spacing protrusion is in non-contact with the integral connection member in the cam roller spacing guide groove, when the cutoff pin protrusion moves from the second point of the cutoff pin guide groove to the third point, the cutoff pin horizontally rotates, and the cam roller spacing protrusion horizontally rotates and physically pushes and moves the integral connection member, and the cam roller and the cam nose are spaced apart from each other by the movement of the integral connection member by the cam roller spacing protrusion.

The gas supply pump for a ship dual fuel engine further includes a coupling case at a coupled part of the drive shaft and the piston; a rack member connected to the drive shaft, or connected and fixed to both the drive shaft and the piston in an internal space of the coupling case; a pinion engaged with a teeth-shaped rack on an outer surface of the rack member; and a pinion guide member on the other side of the pinion to transmit the driving force to the pinion, wherein when the pinion guide member moves down, the pinion rotates in a counterclockwise direction, the rack member connected to the drive shaft moves up by the counterclockwise rotation of the pinion, and the cam nose and the cam roller are spaced apart from each other by the upward movement of the rack member.

The pinion guide member may make a reciprocating motion by a hydraulic cylinder.

The gas supply pump for a ship dual fuel engine further includes a pressure chamber between the drive shaft and the piston to selectively apply a driving force of the drive shaft to the piston, wherein an amount of the liquefied gas discharged from the liquefied gas compression device is controlled by adjusting an amount of lubricating oil in the pressure chamber.

A first surface of the pressure chamber contacts the drive shaft, a second surface of the pressure chamber contacts the piston, the first surface of the pressure chamber can move by the driving force of the drive shaft, and the pressure chamber may change in volume by the movement of the first surface.

In case that the pressure chamber is fully filled with the lubricating oil, when the driving force of the drive shaft is applied to the first surface of the pressure chamber, the driving force of the drive shaft is applied to the piston via the lubricating oil filled in the pressure chamber, and the pressure of the piston is transmitted to the liquefied gas compression device and the discharge of the liquefied gas is performed.

In case that there is no lubricating oil in the pressure chamber, when the driving force of the drive shaft is applied to the first surface of the pressure chamber, since the pressure chamber is an empty space, the first surface of the pressure chamber moves toward the second surface, and when a stroke length of the drive shaft by the operation of the camshaft is smaller than a length between the first surface and the second surface of the pressure chamber, the driving force of the drive shaft is not transmitted to the second surface of the pressure chamber, and the discharge of the liquefied gas by the liquefied gas compression device is not performed.

In case that the pressure chamber is filled with the lubricating oil and the lubricating oil in the pressure chamber can be discharged through a lubricating oil supply passage, when the driving force of the drive shaft is applied to the first surface of the pressure chamber, the lubricating oil in the pressure chamber is discharged, the first surface moves by an amount of the discharged lubricating oil, the driving force is not applied to the piston by a length as much as the amount of discharge of the lubricating oil in the pressure chamber among a total stroke length Ds of the drive shaft, and the piston only moves to a remaining stroke length left after subtracting the length as much as the amount of discharge of the lubricating oil in the pressure chamber from the total stroke length Ds.

The gas supply pump for a ship dual fuel engine may further include a lubricating oil supply passage in which the lubricating oil is supplied to the pressure chamber or discharged from the pressure chamber, and a lubricating oil supply device to set an amount of the lubricating oil supplied to the pressure chamber and an amount of the lubricating oil discharged from the pressure chamber.

The gas supply pump for a ship dual fuel engine according to the present disclosure has the following effects.

It is possible to achieve independent operation control for each cylinder provided in the high pressure pump. Accordingly, there is no need to install an additional pump to check or inspect any error in the specific cylinder.

Additionally, it is possible to minimize the influence of the moment of inertia in the rotational motion of the camshaft on the drive shaft and the piston, and it is possible to effectively compress the liquefied gas and prevent the backflow of the liquefied gas through the liquefied gas compression device including the suction valve and the discharge valve.

Along with this, it is possible to prevent cavitation caused by the introduction of liquefied gas and effectively suppress overheat in the internal space of the cylinder through the optimal sealing structure in the region in which the piston moves.

The present disclosure proposes technology related to a high pressure pump for enabling independent operation of each cylinder. The high pressure pump according to the present disclosure plays a role in supplying high pressure gas to a dual fuel engine, and may be employed in a fuel gas supply system (FGSS) that supplies high pressure gas to the dual fuel engine.

The high pressure pump includes a plurality of cylinders, and injects high pressure gas through each cylinder. It is necessary to check or inspect any error in each cylinder, and when a specific cylinder is out of order or requires inspection, it will be efficient to take action for only the corresponding cylinder and enable the remaining cylinder to normally operate. However, as mentioned in the 'Background Art', the high pressure pump according to the related art includes a plurality of cylinders in one crankshaft wherein a connecting rod and a piston are mounted in each cylinder, failing to achieve independent operation control for each cylinder.

The present disclosure proposes technology to achieve independent operation control for each cylinder provided in the high pressure pump. Specifically, the present disclosure proposes technology to selectively control the operation of each of a plurality of cylinders provided in a camshaft.

Along with this, the present disclosure proposes an optimal coupling structure of drive shaft-piston for minimizing the influence of the moment of inertia of the camshaft on the drive shaft and the piston. Additionally, the present disclosure proposes technology to effectively compress liquefied gas and prevent the backflow of liquefied gas through a liquefied gas compression device including a suction valve and a discharge valve. Furthermore, the present disclosure proposes technology to prevent cavitation caused by the introduction of liquefied gas and effectively suppress overheat in the internal space of the cylinder through an optimal sealing structure in an area in which the piston moves.

Hereinafter, a gas supply pump for a ship dual fuel engine according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

Referring to <FIG> and <FIG>, the gas supply pump for a ship dual fuel engine according to an embodiment of the present disclosure includes a camshaft, a cam roller <NUM>, a drive shaft <NUM>, a piston <NUM> and a liquefied gas compression device.

The rotational motion of the camshaft <NUM> induces a linear reciprocating motion of the drive shaft <NUM> and the piston <NUM>, and the pressure by the linear reciprocating motion of the piston <NUM> is applied to the liquefied gas compression device, so liquefied gas is discharged at high pressure by the liquefied gas compression device.

The camshaft <NUM> rotates by the power of driving means, and a plurality of cam noses <NUM> are arranged at regular intervals along the lengthwise direction of the camshaft <NUM>. The drive shaft <NUM> is positioned for each cam nose <NUM>, and the drive shaft <NUM> is perpendicular to the lengthwise direction of the camshaft <NUM>. The cam roller <NUM> is between the cam nose <NUM> and the drive shaft <NUM>. Accordingly, the plurality of drive shafts <NUM> are arranged side by side in a direction perpendicular to one camshaft <NUM>, and the cam rollers <NUM> are between the cam noses <NUM> and the drive shafts <NUM> of the camshaft <NUM>.

The rotational motion of the camshaft <NUM> induces the linear reciprocating motion of the drive shaft <NUM>, and this motion can be enabled by the cam nose <NUM> of the camshaft <NUM>.

It is designed such that the center of rotation of the cam nose <NUM> is the same as the center of rotation of the camshaft <NUM>, the radius of the cam nose <NUM> is smaller than the radius of the camshaft <NUM>, and the radius of rotation of the cam nose <NUM> corresponds to the radius of rotation of the camshaft <NUM>.

The cam roller <NUM> is in close contact with each cam nose <NUM> on one side of the cam nose <NUM>. Since the center of rotation of the cam nose <NUM> is eccentric from the axis of the camshaft and the radius of the cam nose <NUM> is smaller than the radius of the camshaft <NUM>, when the camshaft <NUM> rotates, the cam roller <NUM> on one side of the cam nose <NUM> makes a linear reciprocating motion within a predetermined distance.

Additionally, the drive shaft <NUM> and the piston <NUM> are connected adjacent to each other on one side of the cam roller <NUM>, and when the cam roller <NUM> makes the linear reciprocating motion, the drive shaft <NUM> and the piston <NUM> also make a linear reciprocating motion together.

Specifically, as shown in <FIG>, when the cam nose <NUM> is located at <NUM>° angle on the basis of the vertical direction by the rotation of the camshaft <NUM>, the cam roller <NUM> moves in a compression direction of the piston <NUM>, and as shown in <FIG>, when the cam nose <NUM> is located at <NUM>° angle by the rotation of the camshaft <NUM>, the cam roller <NUM> moves in a decompression direction of the piston <NUM>. As described above, when the camshaft <NUM> rotates, the cam roller <NUM> makes the linear reciprocating motion within the predetermined distance, and the distance of the linear reciprocating motion of the cam roller <NUM> corresponds to a distance between the cam nose <NUM> located at <NUM>° angle and the cam nose <NUM> located at <NUM>° angle. Here, when the cam nose <NUM> is located at <NUM>° angle, the movement of the cam roller <NUM> in the decompression direction of the piston <NUM> is made by a compression spring <NUM> as described below. Additionally, in the specification, the compression direction of the piston <NUM> refers to a direction in which the piston <NUM> moves inward of a cylinder <NUM>, and the decompression direction of the piston <NUM> refers to a direction in which the piston <NUM> moves outward of the cylinder <NUM>.

The drive shaft <NUM> is disposed at one end of the cam roller <NUM>, and the compression spring <NUM> is disposed around the drive shaft <NUM>. When the cam roller <NUM> moves in the compression direction of the piston <NUM>, the compression spring <NUM> is compressed, and when the cam roller <NUM> moves in the decompression direction of the piston <NUM>, the compression spring <NUM> is restored to the original state.

The cam roller <NUM> and the drive shaft <NUM> are integrally connected by an integral connection member <NUM>, and one end of the compression spring <NUM> is fixed to the integral connection member <NUM>. Specifically, the integral connection member <NUM> is hollow, and the cam roller <NUM> is seated at one end of the integral connection member <NUM> and the drive shaft <NUM> is mounted at the other end, and the compression spring <NUM> disposed around the drive shaft <NUM> is fixed to the inner side of the integral connection member <NUM>.

As described above, due to the structure in which the cam roller <NUM>, the drive shaft <NUM> and the integral connection member <NUM> are integrally connected, when the camshaft <NUM> rotates, not only the cam roller <NUM> in close contact with the cam nose <NUM> but also the drive shaft <NUM> and the integral connection member <NUM> make a linear reciprocating motion together, and the compression spring <NUM> is compressed or restored to the original state by the movement.

Meanwhile, a cam roller-drive shaft case <NUM> is provided on the outer side of the integral connection member <NUM>. The cam roller-drive shaft case <NUM> plays a role in protecting the integral connection member <NUM> and the compression spring <NUM> from the outdoor environment and guiding the movement of the integral connection member <NUM> and the compression spring <NUM>.

The drive shaft <NUM> and the piston <NUM> are coupled by the following configuration.

Since the piston <NUM> is a device designed to make a linear reciprocating motion in the cylinder <NUM>, a direction of a force applied to the piston <NUM> should be accurately consistent with the linear reciprocating motion of the piston <NUM>. When the direction of the force applied to the piston <NUM> is inconsistent with the linear reciprocating motion direction of the piston <NUM>, this represents a partial loss of the force applied to the piston <NUM>, and further, it hinders the linear reciprocating motion of the piston <NUM>.

Meanwhile, the force applied to the piston <NUM> is the linear reciprocating motion of the drive shaft <NUM>, and the linear reciprocating motion of the drive shaft <NUM> is induced by the rotational motion of the camshaft <NUM>. However, during the transformation of the rotational motion of the camshaft <NUM> into the linear reciprocating motion of the drive shaft <NUM>, the moment of inertia of the camshaft <NUM> acts on the drive shaft <NUM> and it may hinder the linear reciprocating motion of the drive shaft <NUM>. The moment of inertia refers to the rotational inertia in the rotational reciprocating motion of the cam/roller, and an inertia moment damping member <NUM> as described below is provided to prevent the rotational inertia from affecting the reciprocating motion of the piston.

The coupling structure of the drive shaft <NUM> and the piston <NUM> according to the present disclosure is designed considering the action of the moment of inertia of the camshaft <NUM>. That is, the drive shaft <NUM> and the piston <NUM> have an optimal coupling structure for minimizing the influence of the moment of inertia of the camshaft <NUM> on the drive shaft <NUM>.

Specifically, referring to <FIG> and <FIG>, a first seating portion <NUM> and a second seating portion <NUM> for providing a predetermined space are at one end of the drive shaft <NUM>. The first seating portion <NUM> is disposed in the inner direction of the drive shaft <NUM>, and the second seating portion <NUM> is disposed in the outer direction of the drive shaft <NUM>. The diameter of the second seating portion <NUM> is larger than the diameter of the first seating portion <NUM>, and the diameter of the first seating portion <NUM> corresponds to the diameter of the piston <NUM>.

The inertia moment damping member <NUM> is disposed in the first seating portion <NUM>. One exposed surface of the inertia moment damping member <NUM> comes into close contact with the piston <NUM>. Additionally, one surface of the inertia moment damping member <NUM> in close contact with the piston <NUM> has a gentle slope convex surface shape with a large radius of curvature.

The reason why one surface of the inertia moment damping member <NUM> in close contact with the piston <NUM> is designed in the gentle slope convex surface shape with a large radius of curvature is to minimize the action of the moment of inertia applied to the drive shaft <NUM> on the piston <NUM> when the moment of inertia of the camshaft <NUM> is applied to the drive shaft <NUM>. Since the moment of inertia applied to the drive shaft <NUM> is allowed to spread out by the convex surface of the inertia moment damping member <NUM> prior to being applied to the piston <NUM>, the moment of inertia applied to the piston <NUM> is minimized.

A stopper <NUM> is filled between a space between the second seating portion <NUM> and the piston <NUM>. The stopper <NUM> is in close contact with the piston <NUM> and the inner diameter of the second seating portion <NUM> to prevent the piston <NUM> from rotating.

Additionally, a clamp <NUM> may be provided at the coupled part of the drive shaft <NUM> and the piston <NUM> to protect the corresponding coupled part. That is, it is possible to protect the coupled part of the drive shaft <NUM> and the piston <NUM> from the outdoor environment by fastening two clamp <NUM> members with bolts.

The piston <NUM> makes the linear reciprocating motion in the cylinder <NUM>, and the pressure is applied to the liquefied gas compression device by the linear reciprocating motion of the piston <NUM>. The liquefied gas compression device is a device that discharges the liquefied gas at high pressure using the pressure applied by the piston <NUM>.

As shown in <FIG> and <FIG>, the liquefied gas compression device includes a liquefied gas supply passage <NUM>, a suction valve <NUM> and a discharge valve <NUM>.

The liquefied gas supply passage <NUM> is a passage or channel for the liquefied gas supply to the suction valve <NUM>. One end of the liquefied gas supply passage <NUM> is connected to a liquefied gas supply port <NUM> on one side of the gas supply pump, and the other end is connected to a liquefied gas inlet port <NUM> on one side of the suction valve <NUM>. The liquefied gas to be compressed is supplied to the internal space of the suction valve <NUM> through the liquefied gas inlet port <NUM> via the liquefied gas supply port <NUM> and the liquefied gas supply passage <NUM>. The liquefied gas supply passage <NUM> connected to the suction valve <NUM> is formed in a housing of the suction valve <NUM> that covers the suction valve <NUM>.

An opening/closing member <NUM> is provided around the suction valve <NUM> to selectively open/close the liquefied gas inlet port <NUM>. The opening/closing member <NUM> is connected to a spring member <NUM> around the bottom circumference of the suction valve <NUM> and can make a linear reciprocating motion by the compression and restoration of the spring member <NUM>. When the opening/closing member <NUM> moves in the compression direction by the compression of the spring member <NUM>, the liquefied gas inlet port <NUM> is opened, and when the opening/closing member <NUM> moves in the restoration direction by the restoration of the spring member <NUM>, the liquefied gas inlet port <NUM> is closed. The compression and restoration of the spring member <NUM> is carried out by the force acting on the opening/closing member <NUM>.

When the liquefied gas is supplied through the liquefied gas supply passage <NUM> with the liquefied gas inlet port <NUM> closed by the opening/closing member <NUM>, as the piston <NUM> is retracted, the pressure of the internal space of the suction valve <NUM> is lower than the liquefied gas supply pressure, and the opening/closing member <NUM> moves in the compression direction of the spring member <NUM>, and accordingly, the liquefied gas inlet port <NUM> is opened, and the liquefied gas is supplied to the internal space of the suction valve <NUM>. In this way, the liquefied gas is supplied from the liquefied gas supply passage <NUM> to the suction valve <NUM>.

The liquefied gas in the suction valve <NUM> is discharged at high pressure through the discharge valve <NUM>, and the liquefied gas in the suction valve <NUM> is supplied to the discharge valve <NUM> through a suction valve outlet pipe 60a.

The discharge valve <NUM> is disposed in a discharge chamber <NUM>. The discharge valve <NUM> makes a linear reciprocating motion within a predetermined distance in the discharge chamber <NUM> by the applied pressure. Additionally, in the same way as the suction valve <NUM>, a spring member <NUM> is provided at the lower end of the discharge valve <NUM> to allow the discharge valve <NUM> to make a linear reciprocating motion by the compression and restoration of the spring member <NUM>. The compression and restoration of the spring member <NUM> is determined based on a force acting on the discharge valve <NUM>, and the force acting on the discharge valve <NUM> is the pressure of the liquefied gas discharged from the suction valve <NUM> by the pressure of the piston <NUM>.

The discharge valve <NUM> is configured to close the suction valve outlet pipe 60a when the spring member <NUM> is restored. When the discharge valve <NUM> moves in the compression direction of the spring member <NUM>, a space is formed on top of the discharge chamber <NUM>, and the suction valve outlet pipe 60a is opened. Additionally, an auxiliary chamber <NUM> of a predetermined space is provided around the top circumference of the discharge chamber <NUM>, and the auxiliary chamber <NUM> is connected to the space on top of the discharge chamber <NUM> and is also connected to a discharge inlet pipe <NUM> on one side of the discharge valve <NUM>.

That is, when the space is formed on top of the discharge chamber <NUM> by the movement of the discharge valve <NUM>, the corresponding space is spatially connected to the suction valve outlet pipe 60a and is also connected to the auxiliary chamber <NUM>. Additionally, due to the structure in which the auxiliary chamber <NUM> is connected to the discharge inlet pipe <NUM>, the liquefied gas discharged through the suction valve outlet pipe 60a is supplied to the internal space of the discharge chamber <NUM> via the auxiliary chamber <NUM> through the space <NUM> on top of the discharge chamber.

When the pressure of the piston <NUM> is applied to the suction valve <NUM> filled with the liquefied gas (see <FIG>), the liquefied gas in the suction valve <NUM> is discharged through the suction valve outlet pipe 60a, and in this instance, the pressure of the liquefied gas discharged through the suction valve outlet pipe 60a is applied to the discharge valve <NUM>. When the pressure is applied to the discharge valve <NUM>, the discharge valve <NUM> moves in the compression direction of the spring member <NUM>, and accordingly, the space <NUM> is formed on top of the discharge chamber <NUM>, and the liquefied gas discharged through the suction valve outlet pipe 60a moves to the auxiliary chamber <NUM> through the space <NUM> on top of the discharge chamber <NUM> (see <FIG>). Due to the structure in which the auxiliary chamber <NUM> is connected to the discharge inlet pipe, the liquefied gas in the auxiliary chamber <NUM> is supplied to the internal space of the discharge inlet pipe, and finally, the compressed liquefied gas is discharged through the discharge valve <NUM>.

When the piston <NUM> moves in the decompression direction and the liquefied gas in the suction valve <NUM> is not discharged through the suction valve outlet pipe 60a, the discharge chamber <NUM> is restored to the original state by the restoration of the spring member <NUM>, and the space <NUM> on top of the discharge chamber <NUM> disappears and the discharge chamber <NUM> closes the suction valve outlet pipe 60a.

Due to the structure in which the liquefied gas discharged from the suction valve outlet pipe 60a is supplied to the discharge valve <NUM> via the space <NUM> on top of the discharge chamber <NUM> and the auxiliary chamber <NUM>, it is possible to prevent the backflow of the liquefied gas at the rear end of the discharge valve <NUM> toward the suction valve <NUM> by the auxiliary chamber <NUM> and the space <NUM> on top of the discharge chamber <NUM>.

In the above description, when the liquefied gas is discharged through the suction valve outlet pipe 60a, since the operating pressure of the piston <NUM> is much higher than the supply pressure of the liquefied gas supplied to the liquefied gas supply passage <NUM>, the liquefied gas inlet port <NUM> is closed by the opening/closing member <NUM>.

As described above, as the pressure of the piston <NUM> making the linear reciprocating motion in the cylinder <NUM> is applied to the liquefied gas compression device, the liquefied gas is discharged at high pressure through the suction valve <NUM> and the discharge valve <NUM> of the liquefied gas compression device.

Meanwhile, in the process of liquefied gas compression and discharge by the liquefied gas compression device, the liquefied gas in the liquefied gas compression device may enter the internal space of the cylinder <NUM> through a micro-gap between the piston <NUM> and the cylinder <NUM>. When sealing prevents the liquefied gas from entering, the liquefied gas is discharged without leaks, thereby increasing the pump efficiency. However, when there is no sealing for preventing the liquefied gas from entering, the liquefied gas entering the internal space of the cylinder <NUM> induces cavitation by the friction heat during the linear reciprocating motion of the piston <NUM>, causing mechanical damage to the piston <NUM>, the cylinder <NUM> and the drive shaft <NUM>.

Accordingly, completely preventing or partially allowing the introduction of liquefied gas into the internal space of the cylinder <NUM> has advantages and disadvantages.

The present disclosure proposes an approach to increase the efficiency of the pump and prevent cavitation caused by the introduction of liquefied gas through the piston <NUM> sealing structure that blocks or allows the introduction of liquefied gas.

The piston <NUM> sealing structure is largely divided into a cylinder side sealing structure and a rod side sealing structure. The cylinder side sealing structure is a sealing structure for the piston <NUM> embedded in the cylinder, and the rod side sealing structure is a sealing structure for the piston portion which is not embedded in the cylinder <NUM>, i.e., the rod.

The present disclosure designs the cylinder side sealing structure to allow the introduction of liquefied gas to some extent, and the rod side sealing structure to prevent the introduction of liquefied gas and other materials. Furthermore, the present disclosure proposes configurations for preventing the introduction of liquefied gas and other materials for both the cylinder side sealing structure and the rod side sealing structure.

As shown in <FIG> and <FIG>, the cylinder side sealing structure includes a spring member seating groove 51a and a guide ring seating groove 51b spatially connected to the circumference of the piston portion embedded in the cylinder <NUM>. The spring member seating groove 51a and the guide ring seating groove 51b are designed in a multi-step shape such that the width of the guide ring seating groove 51b is larger than the width of the spring member seating groove 51a. A spring member <NUM> having a hollow shape and thus an elastic property is mounted in the spring member seating groove 51a, and a band-shaped plate type guide ring <NUM> is mounted in the guide ring seating groove 51b adjacent to the spring member seating groove 51a. The width of the spring member <NUM> seated in the spring member seating groove 51a is smaller than the width of the guide ring <NUM> seated in the guide ring seating groove.

The guide ring <NUM> plays a role in guiding the movement of the piston <NUM> during the reciprocating motion of the piston in the cylinder, and the spring member <NUM> which is in contact with the guide ring <NUM> and seated in the spring member seating groove 51a plays a role in damping the force applied to the guide ring during the movement of the piston <NUM>. With the spring member <NUM>, it is possible to uniformly maintain the position of the guide ring <NUM>, thereby stably guiding the movement of the piston <NUM>.

A combination of the guide ring <NUM> and the spring member <NUM> is repeated at regular intervals along the lengthwise direction of the piston portion. In an embodiment, the combination of the guide ring <NUM> and the spring member <NUM> may be repeated five times.

The cylinder side sealing structure including the guide ring <NUM> and the spring member <NUM> as described above is designed to allow the introduction of liquefied gas to some extent, and this design is to effectively suppress overheat in the internal space of the cylinder <NUM>.

The cylinder side sealing structure may be designed not only to allow the introduction of liquefied gas as described above but also to disallow the introduction of liquefied gas. The cylinder side sealing structure that disallows the introduction of liquefied gas may be a structure that is faithful to the intrinsic purpose of sealing.

Specifically, the cylinder side sealing structure that disallows the introduction of liquefied gas includes a combination of the guide ring <NUM> and a piston seal <NUM> as shown in <FIG>. Specifically, the guide ring seating groove is disposed along the circumference of the piston portion, and the band-shaped plate type guide ring <NUM> is mounted in the corresponding guide ring seating groove. Additionally, a piston seal seating groove is disposed on the circumference of the piston portion located in the lengthwise direction of the piston portion apart from the guide ring seating groove, and the piston seal <NUM> is mounted in the corresponding piston seal seating groove.

The guide ring <NUM> is positioned on the left and right sides of the piston seal <NUM> and plays a role in guiding the movement of the piston <NUM>, and the piston seal <NUM> plays a role in preventing the liquefied gas from entering.

The detailed structure of the piston seal <NUM> is as follows. The piston seal <NUM> includes a contact member <NUM>, a spring member <NUM> and a stopper <NUM>. The contact member <NUM>, the spring member <NUM> and the stopper <NUM> are disposed around the piston <NUM>.

The contact member <NUM> has one surface in close contact with the outer surface of the piston <NUM> and the other surface in close contact with the inner wall of the cylinder <NUM>, and the contact member <NUM> has a seating groove in which the spring member <NUM> is seated. The spring member <NUM> is inserted into the seating groove of the contact member <NUM> and plays a role in applying a force to cause the contact member <NUM> to come into close contact with the outer surface of the piston <NUM> and the inner wall of the cylinder <NUM> through the restoring force of the spring member <NUM>. It is possible to prevent the liquefied gas from moving from one side of the cylinder to the other side through a combination of the contact member <NUM> and the spring member <NUM>. The stopper <NUM> plays a role in preventing the spring member <NUM> from moving out of the seating groove of the contact member <NUM>.

Subsequently, describing the rod side sealing structure, as shown in <FIG> and <FIG>, the rod side sealing structure is designed to prevent the introduction of liquefied gas from the cylinder and prevent the introduction of air and impurities at the coupled part of the drive shaft <NUM> and the piston <NUM>.

A piston cover <NUM> is disposed around the rod portion at which the rod portion of the piston <NUM> is located, and the piston cover <NUM> includes a rod seal <NUM>, a guide ring <NUM> and a wiper seal <NUM>. The rod seal <NUM> is disposed on the piston cover <NUM> on the side of the cylinder <NUM>, and the wiper seal <NUM> is disposed on the piston cover <NUM> on the side of the drive shaft <NUM>. Additionally, the guide ring is positioned on the piston cover <NUM> adjacent to each of the rod seal <NUM> and the wiper seal <NUM>, and the guide ring is located in the inner direction of the rod portion. Accordingly, the wiper seal <NUM>, the guide ring, the guide ring and the rod seal <NUM> are arranged on the piston cover <NUM> in that order from the drive shaft <NUM> to the cylinder <NUM>.

The wiper seal <NUM> plays a role in preventing air and other materials such as impurities from entering from the drive shaft <NUM>, and the rod seal <NUM> plays a role in preventing liquefied gas from entering from the cylinder <NUM>. Additionally, the guide ring plays a role in guiding the movement of the rod portion on the piston cover <NUM>.

The rod seal <NUM> and the wiper seal <NUM> have the same structure as the piston seal applied to the cylinder side sealing structure. That is, in the same way as the piston seal <NUM>, each of the rod seal <NUM> and the wiper seal <NUM> includes a contact member <NUM>, a spring member <NUM> and a stopper <NUM>.

Additionally, in the same way as the guide ring <NUM> applied to the cylinder side sealing structure, the guide ring <NUM> applied to the rod side sealing structure further includes a spring member <NUM> therein. The guide ring <NUM> plays a role in guiding the movement of the rod portion during the reciprocating motion of the rod portion, and the spring member <NUM> is in contact with the guide ring <NUM> and plays a role in damping the force applied to the guide ring during the movement of the rod portion. With the spring member <NUM>, it is possible to uniformly maintain the position of the guide ring <NUM>, thereby stably guiding the movement of the rod portion.

Meanwhile, one of the most important features of the present disclosure is that each of the plurality of cylinders <NUM> provided in the camshaft <NUM> can independently operate.

As described above, the plurality of cam noses <NUM> are provided in the camshaft <NUM>, spaced apart from each other, the cam roller <NUM> is provided in close contact with each cam nose <NUM>, and each cam roller <NUM> is connected to the drive shaft <NUM>, the piston <NUM>, the cylinder <NUM> and the liquefied gas compression device. Accordingly, this structure enables the operation of the plurality of liquefied gas compression devices through the operation of one camshaft <NUM>.

Under this structure, it is possible to independently control the operation of each of the plurality of cylinders <NUM>, i.e., the operation of each of the plurality of liquefied gas compression devices. To this end, the present disclosure proposes technology to force the cam roller <NUM> to be spaced apart from the cam nose <NUM> to stop the operation of the drive shaft <NUM>, the piston <NUM>, the cylinder <NUM> and the liquefied gas compression device connected to the cam roller <NUM> forced to be spaced apart. Specifically, it can be realized through three embodiments. The first embodiment is designed to cause the cam roller <NUM> to be spaced apart from the cam nose <NUM> using a cutoff bolt <NUM>, the second embodiment is designed to cause the cam roller <NUM> to be spaced apart from the cam nose <NUM> using a cutoff pin <NUM>, and the third embodiment is designed to cause the cam roller <NUM> to be spaced apart from the cam nose <NUM> using a rack-pinion <NUM>.

To begin with, the first embodiment is as follows.

Referring to <FIG> and <FIG>, the cam roller-drive shaft case <NUM> has, on one side, a cutoff bolt through-hole <NUM> through which the cutoff bolt <NUM> is inserted and passed, and the integral connection member <NUM> has, on one side, a cutoff bolt insertion groove <NUM> into which the cutoff bolt <NUM> is inserted to a predetermined depth.

The cam nose <NUM> and the cam roller <NUM> may be induced to be spaced apart from each other through the process of inserting the cutoff bolt <NUM> into the cutoff bolt insertion groove <NUM> through the cutoff bolt through-hole <NUM>.

As the cam nose <NUM> and the cam roller <NUM> are spaced apart from each other, even though the camshaft <NUM> rotates, the cam nose <NUM> and the cam roller <NUM> do not come to contact with each other, and the operation of the drive shaft <NUM> and the piston <NUM> connected to the corresponding cam roller <NUM> is stopped. Through this process, it is possible to selectively control the operation of each piston <NUM> provided in the camshaft <NUM>.

Below is the principle in which the cam nose <NUM> and the cam roller <NUM> are spaced apart from each other by the insertion of the cutoff bolt <NUM> into the cutoff bolt insertion groove <NUM> (see FIGS. 4A and 4B).

The center of the cutoff bolt through-hole <NUM> and the center of the cutoff bolt insertion groove <NUM> adjacent to each other do not match and are offset each other.

The cam roller-drive shaft case <NUM> has the cutoff bolt through-hole <NUM> and the integral connection member <NUM> has the cutoff bolt insertion groove <NUM>, and the cutoff bolt <NUM> is inserted into the cutoff bolt insertion groove <NUM> through the cutoff bolt through-hole <NUM>. The cutoff bolt through-hole <NUM> and the cutoff bolt insertion groove <NUM> may be designed with the same diameter.

In this instance, the center of the cutoff bolt through-hole <NUM> and the center of the cutoff bolt insertion groove <NUM> are offset each other. On the basis of the piston <NUM> being perpendicular to the camshaft <NUM>, the center of the cutoff bolt insertion groove <NUM> is located at a slightly lower position than the center of the cutoff bolt through-hole <NUM>. Additionally, the cutoff bolt insertion groove <NUM> has a tapered shape having the decreasing radius with the increasing depth. The cutoff bolt insertion groove <NUM> have a difference 'd' between the radius at the entrance and the radius at the lower surface by the tapered shape (see <FIG>).

Under this condition, the cutoff bolt <NUM> passing through the cutoff bolt through-hole <NUM> is inserted into the cutoff bolt insertion groove <NUM>, and since the center of the cutoff bolt insertion groove <NUM> is located at a slightly lower position than the center of the cutoff bolt through-hole <NUM>, the cutoff bolt <NUM> contacts the side of the cutoff bolt insertion groove <NUM> having the tapered shape.

When the cutoff bolt <NUM> is continuously tightened in the insertion direction, the cutoff bolt <NUM> moves more inward of the cutoff bolt insertion groove <NUM> along the side of the cutoff bolt insertion groove <NUM>. The movement of the cutoff bolt <NUM> inward of the cutoff bolt insertion groove <NUM> represents the upward movement of the integral connection member <NUM> having the cutoff bolt insertion groove <NUM>.

When one end of the cutoff bolt <NUM> contacts the lower surface of the cutoff bolt insertion groove <NUM> in this way, the integral connection member <NUM> moves up by the difference 'd' between the radii at the entrance and the lower surface of the cutoff bolt insertion groove <NUM>. Here, a predetermined part of the cutoff bolt <NUM> also may have a tapered shape to make it easy to insert, and in this case, the movement distance of the integral connection member <NUM> corresponds to a value obtained by subtracting the taper thickness of the cutoff bolt <NUM> from 'd'.

Through the above-described process, the integral connection member <NUM> may move up by the length 'd', and this represents that the cam nose <NUM> and the cam roller <NUM> are spaced apart from each other by the length 'd'. By this principle, the cam nose <NUM> and the cam roller <NUM> may be kept apart from each other, and as the cam nose <NUM> and the cam roller <NUM> are spaced apart from each other, even though the camshaft <NUM> rotates, the drive shaft <NUM> and the piston <NUM> connected to the corresponding cam roller <NUM> do not operate.

Although the foregoing describes that the cam roller-drive shaft case <NUM> has, on one side, the cutoff bolt through-hole <NUM> into which the cutoff bolt <NUM> is inserted and passed through and the integral connection member <NUM> has, on one side, the cutoff bolt insertion groove <NUM> into which the cutoff bolt <NUM> is inserted to the predetermined depth, the position of the cutoff bolt through-hole <NUM> and the cutoff bolt insertion groove <NUM> is not limited to a particular position. In an embodiment, the cutoff bolt through-hole <NUM> and the cutoff bolt insertion groove <NUM> may be disposed at a position corresponding to the internal space of the camshaft <NUM> case (see FIGS. 4A and 4B), or the cutoff bolt through-hole <NUM> and the cutoff bolt insertion groove <NUM> may be disposed at a position corresponding to the outside of the camshaft <NUM> case.

Below is the configuration of the second embodiment using the cutoff pin <NUM>.

Referring to <FIG> and <FIG>, a hollow cylindrical cutoff pin guide member <NUM> is provided on one side of the cam roller-drive shaft case <NUM>, and the cutoff pin <NUM> is inserted into the cutoff pin guide member <NUM>. The cutoff pin <NUM> can move up or down in the cutoff pin guide member <NUM>.

The cutoff pin guide member <NUM> has a cutoff pin guide groove <NUM> on one side. The cutoff pin guide groove <NUM> includes a vertical guide groove and a horizontal guide groove, and the vertical guide groove and the horizontal guide groove are spatially connected to each other. The vertical guide groove is extended from a first point to a second point on a vertical line, and the horizontal guide groove is extended from the second point of the vertical guide groove to a third point in the horizontal direction. The second point and the third point of the horizontal guide groove may be disposed at <NUM>° point and <NUM>° point.

A cutoff pin guide pin <NUM> is provided on one side of the cutoff pin <NUM>, and is disposed in the cutoff pin guide groove <NUM>. Accordingly, the cutoff pin guide pin <NUM> can move along the cutoff pin guide groove <NUM>. When the cutoff pin guide pin <NUM> vertically moves from the first point of the cutoff pin guide groove <NUM> to the second point, the cutoff pin <NUM> moves down by the corresponding distance, and when the cutoff pin guide pin <NUM> horizontally moves from the second point of the cutoff pin guide groove <NUM> to the third point, the cutoff pin <NUM> rotates by an angle between the second point and the third point, for example, <NUM>°.

The cutoff pin <NUM> has, on the lower surface, a cam roller spacing protrusion <NUM> of a cylindrical shape having a smaller radius than the cutoff pin <NUM>. The center of the cam roller spacing protrusion <NUM> is eccentric from the center of a circle of the cutoff pin <NUM>. When the cutoff pin guide pin <NUM> horizontally moves from the second point of the cutoff pin guide groove <NUM> to the third point, the cam roller spacing protrusion <NUM> on the lower surface of the cutoff pin <NUM> rotates by the predetermined angle, for example, <NUM>°.

Meanwhile, the cam roller-drive shaft case <NUM> has, on one side, a cutoff pin through-hole <NUM> into which the cutoff pin <NUM> is inserted and passed through, and the integral connection member <NUM> has a cam roller spacing guide groove <NUM> corresponding to the cutoff pin through-hole <NUM>.

When the cutoff pin guide pin <NUM> is located at the second point, the cam roller spacing protrusion <NUM> at the lower end of the cutoff pin <NUM> is disposed in the cam roller spacing guide groove <NUM> of the integral connection member <NUM>, and is in non-contact with the integral connection member <NUM> in the cam roller spacing guide groove <NUM> (see <FIG>).

In this state, when the cutoff pin <NUM> protrusion moves from the second point of the cutoff pin guide groove <NUM> to the third point, the cutoff pin <NUM> makes a horizontal rotation and the cam roller spacing protrusion <NUM> also makes a horizontal rotation, and accordingly, the cam roller spacing protrusion <NUM> makes a horizontal rotation at a predetermined angle in the cam roller spacing guide groove <NUM> and comes into contact with the integral connection member <NUM> (see <FIG>). Subsequently, the cam roller spacing protrusion <NUM> physically pushes the integral connection member <NUM> in contact with the cam roller spacing protrusion <NUM>, then the integral connection member <NUM> moves and the cam roller <NUM> also moves with the integral connection member <NUM>, and finally, the cam roller <NUM> and the cam nose <NUM> are spaced apart from each other (see <FIG>).

On the contrary, when the cutoff pin guide pin <NUM> moves from the third point of the cutoff pin guide groove <NUM> to the second point, the moved integral connection member <NUM> is restored to the original state and the cam roller <NUM> and the cam nose <NUM> come into contact with each other again.

As described above, the cam nose <NUM> and the cam roller <NUM> may be induced to be spaced apart from each other through the configuration using the cutoff pin <NUM>, and as the cam nose <NUM> and the cam roller <NUM> are spaced apart from each other, it is possible to selectively control the operation of the specific piston <NUM>, i.e., the specific cylinder <NUM>.

Below is the configuration of the third embodiment using the rack-pinion <NUM>.

While the first and second embodiments are designed to cause the cam roller <NUM> and the cam nose <NUM> to be spaced apart from each other by inserting the cutoff bolt <NUM> or the cutoff pin <NUM> into the integral connection member <NUM>, the third embodiment is designed to induce the cam roller <NUM> and the cam nose <NUM> to be spaced apart from each other through the movement of the drive shaft <NUM>.

According to the third embodiment, as shown in <FIG>, a coupling case <NUM> is further provided at the coupled part of the drive shaft <NUM> and the piston <NUM> to protect it from the outdoor environment. Additionally, the rack-pinion <NUM> device operated by a hydraulic cylinder <NUM> is further provided.

Specifically, a rack member <NUM> is provided in the internal space of the coupling case <NUM>. The rack member <NUM> is connected and fixed to one side of the drive shaft <NUM> or both the drive shaft <NUM> and the piston <NUM>. Accordingly, when the drive shaft <NUM> moves, the rack member <NUM> also moves together. In other words, when the rack member <NUM> moves, the drive shaft <NUM> and the piston <NUM> also move together.

A teeth-shaped rack is provided on the outer surface of the rack member <NUM>. Additionally, the rack of the rack member <NUM> is engaged with the pinion <NUM>. Accordingly, the rack member <NUM> can move up and down by the rotational motion of the pinion <NUM>. A pinion guide member <NUM> is provided on the other side of the pinion <NUM> to transmit the driving force to the pinion <NUM>, and the pinion guide member <NUM> selectively moves up and down by the hydraulic cylinder <NUM>. A rack is also provided on the surface of the pinion guide member <NUM>, and the pinion <NUM> is engaged with the rack of the pinion guide member <NUM>.

Under this structure, when the pinion guide member <NUM> moves down through the hydraulic cylinder <NUM>, the pinion <NUM> rotates in the counterclockwise direction, and the rack member <NUM> connected to the drive shaft <NUM> moves up by the counterclockwise rotation of the pinion <NUM>. The upward movement of the rack member <NUM> represents the upward movement of the drive shaft <NUM>, and the upward movement of the drive shaft <NUM> may induce the cam nose <NUM> and the cam roller <NUM> to be spaced apart from each other.

The method for causing the cam roller <NUM> and the cam nose <NUM> to be spaced apart from each other according to the first to third embodiments has been hereinabove described. Meanwhile, in inducing the cam roller <NUM> and the cam nose <NUM> to be spaced apart from each other using the first to third embodiments as described above, it is necessary to cause the cam roller <NUM> and the cam nose <NUM> to be spaced apart from each other with the cam nose <NUM> accurately facing the cam roller <NUM>, and to this end, a predetermined turning gear may be provided. The turning gear may precisely adjust the rotation of the camshaft <NUM> so that the cam nose <NUM> accurately faces the cam roller <NUM>.

The foregoing describes that the cam roller and the cam nose are induced to be spaced apart from each other through the above-described first to third embodiments, thereby independently controlling the operation of each cylinder, but according to the first to third embodiments, since the cam roller and the cam nose are spaced apart from each other, the piston is stopped and the liquefied gas is not discharged.

The present disclosure proposes technology to adjust the amount of discharge of liquefied gas. According to an embodiment of the present disclosure, the amount of discharge of liquefied gas may be controlled by adjusting the stroke length of the piston <NUM>.

Specifically, as shown in <FIG>, a pressure chamber <NUM> is provided between the drive shaft <NUM> and the piston <NUM>. A first surface <NUM> of the pressure chamber <NUM> contacts the drive shaft <NUM>, and a second surface <NUM> of the pressure chamber <NUM> opposite the first surface <NUM> is fixed in contact with the piston <NUM>. Accordingly, when the drive shaft <NUM> moves towards the piston <NUM>, the driving force of the drive shaft <NUM> is applied to the first surface <NUM> of the pressure chamber <NUM> and is transmitted to the pressure chamber <NUM>. In this instance, in case that the pressure chamber <NUM> is fully filled with lubricating oil, the driving force of the drive shaft <NUM> will be transmitted to the piston <NUM> via the pressure chamber <NUM> (first case), in case that the pressure chamber <NUM> is an empty space, the driving force of the drive shaft <NUM> disappears in the pressure chamber <NUM> and is not transmitted to the piston <NUM> (second case), and in case that the pressure chamber <NUM> is fully filled with lubricating oil, when some of the lubricating oil in the pressure chamber <NUM> are discharged by the applied driving force of the drive shaft <NUM>, only some of the driving force of the drive shaft <NUM> will be transmitted to the piston <NUM> (third case).

An embodiment of the present disclosure may stop discharging the liquefied gas or control the amount of discharge of liquefied gas using the above-described principle.

Here, a lubricating oil supply passage <NUM> is provided on one side of the pressure chamber <NUM>, and the lubricating oil <NUM> may be supplied to the pressure chamber <NUM> or discharged from the pressure chamber <NUM> through the lubricating oil supply passage <NUM>. Additionally, the lubricating oil supply passage <NUM> is connected to a lubricating oil supply device <NUM>. The amount of the lubricating oil <NUM> supplied to the pressure chamber <NUM> and the amount of the lubricating oil <NUM> discharged from the pressure chamber <NUM> may be set using the lubricating oil supply device <NUM>.

The above-described three cases will be described in detail.

As shown in <FIG>, in case that the pressure chamber <NUM> is fully filled with the lubricating oil <NUM>, when the driving force of the drive shaft <NUM> is applied to the first surface <NUM> of the pressure chamber <NUM>, the driving force of the drive shaft <NUM> is applied to the piston <NUM> via the lubricating oil <NUM> filled in the pressure chamber <NUM>, and finally, the pressure of the piston <NUM> is transmitted to the liquefied gas compression device and the liquefied gas is normally discharged. In this instance, the lubricating oil supply passage <NUM> is closed and the lubricating oil in the pressure chamber <NUM> is not discharged.

In contrast, as shown in <FIG>, in case that there is no lubricating oil <NUM> in the pressure chamber <NUM>, when the driving force of the drive shaft <NUM> is applied to the first surface <NUM> of the pressure chamber <NUM>, since the pressure chamber <NUM> is an empty space, the first surface <NUM> of the pressure chamber <NUM> moves toward the second surface <NUM>. In this instance, when the stroke length of the drive shaft <NUM> by the operation of the camshaft corresponds to the distance between the first surface <NUM> and the second surface <NUM> of the pressure chamber <NUM>, the driving force of the drive shaft <NUM> is not transmitted to the second surface <NUM> of the pressure chamber <NUM>. Accordingly, even though the drive shaft <NUM> moves by the operation of the camshaft, the driving force of the drive shaft <NUM> is not transmitted to the piston <NUM>, so the liquefied gas compression device does not operate and the liquefied gas is not discharged.

Lastly, describing the third case, as shown in <FIG>, in case that the pressure chamber <NUM> is filled with the lubricating oil and the lubricating oil supply passage <NUM> is open, when the driving force of the drive shaft <NUM> is applied to the first surface <NUM> of the pressure chamber <NUM>, the lubricating oil in the pressure chamber <NUM> is discharged through the lubricating oil supply passage <NUM> and the first surface <NUM> moves toward the piston <NUM>. In this instance, the movement distance of the first surface <NUM> may be controlled through the adjustment of the amount of lubricating oil discharged through the lubricating oil supply passage <NUM>. That is, the movement distance of the first surface <NUM> is proportional to the amount of lubricating oil discharged from the pressure chamber <NUM> through the lubricating oil supply passage <NUM>, and the stroke length of the piston may be controlled by adjusting the amount of lubricating oil discharged from the pressure chamber <NUM> through the lubricating oil supply passage <NUM>.

As the driving force is not applied to the piston <NUM> by a length as much as the amount of discharge of lubricating oil in the pressure chamber <NUM> among the total stroke length Ds of the drive shaft <NUM>, the piston <NUM> only moves to the remaining stroke length left after subtracting the length as much as the amount of lubricating oil in the pressure chamber <NUM> from the total stroke length Ds. As described above, with the decreasing stroke length of the piston <NUM>, the amount of liquefied gas discharged through the liquefied gas compression device decreases compared to the normal one.

As described above, it is possible to stop the discharge of the liquefied gas by setting the condition of the pressure chamber <NUM> to empty, and it is possible to maintain the normal discharge of the liquefied gas by fully filling the pressure chamber <NUM> with the lubricating oil <NUM> to completely transmit the driving force of the drive shaft <NUM> to the piston <NUM>, and together with this, it is possible to selectively control the amount of liquefied gas discharged from the liquefied gas compression device by adjusting the amount of lubricating oil discharged from the pressure chamber <NUM>.

Meanwhile, the gas supply pump according to the present disclosure may include the plurality of pistons in one camshaft, and each piston may be independently driven through any one of the above-described first to third embodiments, the cutoff method or the above-described pressure chamber method.

The liquefied gas compression device connected to each piston discharges high pressure liquefied gas by the rotation of the camshaft, and the liquefied gas discharged through each liquefied gas compression device joins at an integrated outlet pipe, and finally, is supplied to an engine combustion chamber.

In the supply of the liquefied gas to the engine combustion chamber through the integrated outlet pipe, the liquefied gas creates pulsation of discharge pressure (hereinafter referred to as 'discharge pressure pulsation') (see <FIG>). The discharge pressure pulsation of the liquefied gas supplied to the engine combustion chamber through the integrated outlet pipe has the physical influence on the liquefied gas combustion efficiency and the engine. When the discharge pressure pulsation increases, the liquefied gas combustion efficiency reduces and physical impacts are applied to the engine.

The discharge pressure pulsation of the liquefied gas is related to the number of pistons connected to the camshaft and the phase of the cam nose to which the piston is connected. Experiments reveal that as the number of pistons in action increases, the discharge pressure pulsation reduces, and when the cam noses to which the pistons are connected are in equidistant phase, the discharge pressure pulsation reduces.

<FIG> and <FIG> show the experimental results of the discharge pressure pulsation as a function of the number of pistons and the cam nose phase. Referring to <FIG>, in case that the number of pistons connected to the camshaft is <NUM>, when the number of pistons in action is <NUM>, the highest discharge pressure pulsation of <NUM> bar is found. In contrast, when the number of pistons in action is <NUM>, the discharge pressure pulsation is <NUM> bar, and when the number of pistons in action is <NUM>, the discharge pressure pulsation is <NUM> bar, so it can be seen that as the number of pistons in action increases, the discharge pressure pulsation reduces. This is because as the number of pistons in action increases, the discharge pressure pulsation of the liquefied gas compressed and discharged through each piston cancels out.

Additionally, referring to <FIG>, it can be seen that in case that the cam noses are in equidistant phase and in case that one piston is cut off without a change in cam nose phase, both when the number of pistons in action is <NUM> and <NUM>, the discharge pressure pulsation reduces in the equidistant phase of the cam noses. Specifically, while when the number of pistons in action is <NUM> and the cam noses are in equidistant phase, the discharge pressure pulsation is <NUM> bar, when one piston is cut off to operate three pistons without a change in cam nose phase, the discharge pressure pulsation increases to <NUM> bar. Additionally, while when the number of pistons in action is <NUM> and the cam noses are in equidistant phase, the discharge pressure pulsation is <NUM> bar, when one piston is cut off to operate two pistons without a change in cam nose phase, the discharge pressure pulsation increases to <NUM> bar.

As can be seen from the foregoing, as the number of pistons connected to the operation of the camshaft increases and when the cam noses are in equidistant phase, it is possible to reduce the discharge pressure pulsation.

Additionally, it can be seen through the above-described experimental results that it is possible to adjust the discharge pressure pulsation through the number of pistons and the cam nose phase placement. In an embodiment, the number of pistons in action and the cam nose phase may be placed considering the allowable range of discharge pressure pulsation. For example, when the upper limit of the allowable range of discharge pressure pulsation is equal to or less than <NUM> bar, the cam noses are in equidistant phase and the minimum number of pistons in action is <NUM>.

Claim 1:
A gas supply pump for a ship dual fuel engine, comprising:
a rotatable camshaft (<NUM>);
a plurality of cam noses (<NUM>) arranged at regular intervals along a lengthwise direction of the camshaft, wherein the cam noses are eccentric from a center of the camshaft;
a plurality of cam rollers (<NUM>), each cam roller in close contact with a respective cam nose;
a plurality of drive shafts (<NUM>) and a plurality of pistons (<NUM>) wherein each drive shaft is adjacent to a respective piston on one side of the respective cam roller; and
a plurality of liquefied gas compression devices, each comprising a liquefied gas supply passage (<NUM>), a suction valve (<NUM>), a discharge valve (<NUM>) and a cylinder (<NUM>) within which the piston reciprocates, to compress and discharge liquefied gas by a linear reciprocating motion of the piston,
wherein as the camshaft rotates, when the cam nose moves in a compression direction of the piston, the liquefied gas in the suction valve is discharged through the discharge valve, and when the cam nose moves in a decompression direction of the piston, the piston is retracted and liquefied gas is supplied to an internal space of the suction valve from the liquefied gas supply passage, and
characterized in that each cam roller is configured to be selectively spaced apart from the respective cam nose, and when the cam roller and the cam nose are spaced apart from each other, a rotational driving force of the cam nose is not transmitted to the piston.