JP2010209874A - High pressure pump for dme fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress leakage of DME fuel in a pump chamber from a gap between a plunger and a cylinder in a high pressure pump for the DME fuel containing dimethyl ether as a main component. <P>SOLUTION: The high pressure pump for the DME fuel includes the cylinder 13, the plunger 14 reciprocating inside the cylinder 13, the pump chamber 15 whose volume changes by reciprocation of the plunger 14 inside the cylinder 13, and a fuel gallery 19 for accumulating the DME fuel supplied to the pump chamber 15. The cylinder 13 includes a recovery groove 23 for recovering the DME fuel leaked from between the cylinder 13 and the plunger 14, and a fuel recovery passage 24 communicating the recovery groove 23 with the fuel gallery 19. The fuel recovery passage 24 includes a passage opening and closing valve 25 for allowing flow of the DME fuel in the direction from the recovery groove 23 to the fuel gallery 19, and closing the fuel recovery passage 24 until pressure in the recovery groove 23 becomes a set valve opening pressure of higher. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-pressure pump for DME fuel containing dimethyl ether as a main component.

  In recent years, as a measure against air pollution in a compression ignition type internal combustion engine (for example, a diesel engine), DME fuel mainly composed of dimethyl ether (DME) whose clean exhaust gas is used instead of diesel oil has attracted attention. DME fuel is a liquefied gas fuel and has a property that it has a lower boiling point and vaporizes at room temperature than light oil, which is a conventional fuel.

  Therefore, when using DME fuel as the fuel for the conventional diesel engine, it is necessary to pressurize the fuel injection device so that the pressure is higher than that of the conventional light oil fuel in the high pressure pump of the fuel injection device. As a result, the leak fuel leaking from the gap between the plunger of the high-pressure pump and the cylinder (plunger barrel) increases as compared with the case where light oil fuel is used. Further, since DME fuel has a lower viscosity than light oil fuel, more leak fuel leaks from the gap than when light oil fuel is used.

  Thus, for example, in the high-pressure pump described in Patent Document 1, a recovery groove is formed around the inner peripheral surface of the cylinder, and the recovery groove and a fuel gallery filled with DME fuel supplied from the feed pump are communicated with each other. A fuel recovery passage is formed. With such a configuration, the leakage fuel leaking from the gap between the plunger and the cylinder in the DME fuel in the pump chamber is returned to the fuel gallery via the recovery groove and the fuel recovery passage formed in the cylinder.

JP 2003-206825 A

  By the way, since DME fuel has a lower calorific value and lower density than light oil fuel, in order to obtain the same output as light oil fuel, the injector needs an injection amount about twice that of light oil fuel. Become. Therefore, the high-pressure pump is required to have a discharge amount that is equal to or greater than the combined amount of the injection amount and the leak fuel.

  However, when the recovery groove and the fuel gallery communicate with each other via the fuel recovery passage as in the high-pressure pump described in Patent Document 1, the DME fuel flows from the recovery groove into the fuel gallery, so that the inside of the recovery groove And the pressure in the pump chamber and the differential pressure in the recovery groove increase. As a result, the DME fuel in the pump chamber easily leaks from the gap between the plunger and the cylinder to the recovery groove, and the recovered DME fuel increases. In particular, since the DME fuel has a lower viscosity than the light oil fuel, the high-pressure fuel in the pump chamber easily leaks from the gap between the plunger and the cylinder to the recovery groove, and the recovered DME fuel increases.

  As a result, the amount of DME fuel discharged from the high-pressure pump decreases, the amount of fuel supplied from the high-pressure pump to the injector becomes insufficient, and there is a problem that appropriate fuel injection cannot be realized in the injector.

  An object of the present invention is to suppress leakage of DME fuel from a gap between a plunger and a cylinder in a pump chamber in a high-pressure pump for DME fuel containing dimethyl ether as a main component.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a high-pressure pump for DME fuel that pressurizes and discharges DME fuel mainly composed of dimethyl ether, and includes a cylinder (13) and a cylinder (13). Plunger (14) arranged to reciprocate inside, pump chamber (15) whose volume is changed by the reciprocating motion of plunger (14) in cylinder (13), and DME supplied to pump chamber (15) A fuel gallery (19) for storing fuel is provided. The cylinder (13) is formed on a sliding surface (13a) on which the plunger (14) of the cylinder (13) slides, and the cylinder (13) and the plunger (14) A recovery groove (23) for recovering the DME fuel leaked from the gap between the recovery groove and the fuel recovery passage (24) connecting the recovery groove (23) and the fuel gallery (19). In the fuel recovery passage (24), the flow of DME fuel in the direction from the recovery groove (23) toward the fuel gallery (19) is allowed, and the pressure in the recovery groove (23) is set open. A passage opening / closing means (25) configured to close the fuel recovery passage (24) until the pressure becomes higher than the pressure is provided.

  Thus, by providing the passage opening / closing means (25) in the fuel recovery passage (24) that allows the recovery groove (23) and the fuel gallery (19) to communicate with each other, the DME fuel is supplied from the recovery groove (23) to the fuel gallery (19 ) It is possible to suppress a pressure drop in the recovery groove (23) due to the flow into the inside.

  Thereby, the pressure in the pump chamber (15) and the differential pressure in the recovery groove (23) can be reduced as compared with the conventional case, and the DME fuel in the pump chamber (15) becomes the plunger (14) and the cylinder (13). It is possible to suppress leakage from the gap to the recovery groove (23). As a result, a sufficient discharge amount of DME fuel in the high-pressure pump can be ensured.

  Specifically, as in the invention described in claim 2, in the invention described in claim 1, the set valve opening pressure of the passage opening / closing means (25) is higher than the pressure in the fuel gallery (19). By setting so as to be, it is possible to suppress the pressure drop in the recovery groove (23) due to the DME fuel flowing from the recovery groove (23) into the fuel gallery (19).

  More specifically, as in the invention described in claim 3, in the invention described in claim 1, the fuel gallery (19) communicates with the outside, and the DME fuel in the fuel gallery (19) is connected to the outside. A discharge passage (20) for discharging is provided, and pressure adjusting means (21) for opening the discharge passage (20) is provided in the discharge passage (20) so that the pressure in the fuel gallery (19) is lower than the reference pressure. By setting the set valve opening pressure of the passage opening / closing means (25) to be higher than the reference pressure, the recovery groove (DME fuel is caused by the flow of DME fuel into the fuel gallery (19) from the recovery groove (23)). 23) It is possible to suppress the pressure drop within.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the high pressure pump which concerns on 1st Embodiment. It is sectional drawing which shows the solenoid valve single-piece | unit of FIG. It is an expanded sectional view of the A section of FIG. It is an expanded sectional view showing the passage on-off valve concerning a 1st embodiment. It is explanatory drawing explaining the pressure change in a pump chamber. It is an expanded sectional view showing the passage on-off valve concerning a 2nd embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view showing a high-pressure pump according to the present embodiment, FIG. 2 is a cross-sectional view of a single solenoid valve of FIG. 1, FIG. 3 is an enlarged cross-sectional view of part A of FIG. It is an expanded sectional view of an on-off valve.

  The high-pressure pump 1 according to the present embodiment uses a DME fuel containing dimethyl ether as a main component in a fuel supply device (not shown) of a compression ignition internal combustion engine (hereinafter simply referred to as an internal combustion engine) (not shown). It is used as a fuel supply pump for supplying to an injector (not shown) via The DME fuel is a fuel having a low viscosity and easily vaporized as compared with light oil, and may be, for example, pure or various dimethyl ether components adjusted to various purities, or dimethyl ether as a main component. And other diesel fuels may be included.

  As shown in FIGS. 1 and 2, the high-pressure pump 1 includes a pump housing 10. The pump housing 10 includes a cam chamber 10a located on the lower end side thereof, a columnar slider insertion hole 10b extending from the cam chamber 10a toward the top of the pump housing 10, and a slider insertion hole 10b. A cylindrical cylinder insertion hole 10c extending to the upper end surface of the pump housing 10 is formed.

  A cam shaft 11 driven by an internal combustion engine (not shown) is disposed in the cam chamber 10a, and the cam shaft 11 is rotatably supported by the pump housing 10. A cam 12 is formed on the cam shaft 11.

  A cylinder 13 is attached to the cylinder insertion hole 10c so as to close the cylinder insertion hole 10c. A cylindrical plunger insertion hole 13a is formed in the cylinder 13, and a cylindrical plunger 14 is inserted into the plunger insertion hole 13a so as to reciprocate. A pump chamber 15 is formed by the upper end surface of the plunger 14 and the inner peripheral surface of the cylinder 13. Accordingly, the volume of the pump chamber 15 changes as the plunger 14 reciprocates in the cylinder 13.

  A sheet 14 a is connected to the lower end of the plunger 14, and the sheet 14 a is pressed against the slider 17 by a spring 16. The seat 14a prevents DME fuel leaking from the gap between the plunger 14 and the plunger insertion hole 13a of the cylinder 13 from flowing into the cam chamber 10a or the like.

  The slider 17 is formed in a cylindrical shape, and is inserted into the slider insertion hole 10b so as to reciprocate. A cam roller 18 is rotatably attached to the slider 17, and the cam roller 18 is in contact with the cam 12. When the cam 12 is rotated by the rotation of the cam shaft 11, the plunger 14 is driven to reciprocate together with the sheet 14a, the slider 17 and the cam roller 18.

  An annular fuel gallery (fuel) is supplied between the cylinder 13 and the pump housing 10 through which low-pressure DME fuel discharged from a low-pressure supply pump (not shown) is supplied via a low-pressure fuel pipe (not shown). A reservoir 19 is formed. The fuel gallery 19 is communicated with the pump chamber 15 via a low pressure communication passage 13b formed in the cylinder 13 and a low pressure passage 31a in an electromagnetic valve 30 described later.

  The fuel gallery 19 is connected to a fuel tank (not shown) via a fuel discharge passage 20, a pressure regulating valve 21, a fuel discharge pipe (not shown), and the like. The pressure regulating valve 21 is attached to the pump housing 10 on the downstream side of the fuel discharge passage 20. The pressure regulating valve 21 constitutes a pressure adjusting means that regulates the maximum pressure in the fuel gallery 19, and biases the valve body 21a that opens and closes the fuel discharge passage 20 and the direction in which the valve body 21a is closed. And a spring 21b. The DME fuel in the fuel gallery 19 is recovered in the fuel tank by moving the valve element 21a in the valve opening direction against the spring 21b when the pressure in the fuel gallery 19 becomes equal to or higher than the reference pressure. It is like that.

  The cylinder 13 is formed with a high-pressure communication path 13 c that always communicates with the pump chamber 15. The pump chamber 15 is connected to a common rail (not shown) via the high-pressure communication path 13c, the discharge valve 22, and a high-pressure fuel pipe (not shown). The high-pressure communication path 13c and the high-pressure fuel pipe constitute a high-pressure fuel supply path.

  The discharge valve 22 is attached to the cylinder 13 on the downstream side of the high-pressure communication path 13c. The discharge valve 22 includes a valve body 22a that opens and closes the high-pressure fuel supply path, and a spring 22b that urges the valve body 22a in the valve closing direction. The DME fuel pressurized in the pump chamber 15 moves the valve body 22a in the valve opening direction against the biasing force of the spring 22b, and is pumped to the common rail.

  The electromagnetic valve 30 is screwed and fixed to the cylinder 13 so as to close the pump chamber 15 at a position facing the upper end surface of the plunger 14.

  The electromagnetic valve 30 includes a body 31. The body 31 has a low pressure passage 31a having one end communicating with the pump chamber 15 and the other end communicating with the low pressure communication passage 13b, and a seat disposed in the low pressure passage 31a. A portion 31b is formed.

  The solenoid valve 30 moves integrally with a solenoid 32 that generates a suction force when energized, an armature 33 that is attracted by the solenoid 32, a spring 34 that biases the armature 33 toward the opposite side, and the armature 33. The valve body 35 opens and closes the low pressure passage 31a by contacting and separating from the seat portion 31b, and the stopper 36 regulates the position of the valve body 35 when the valve is opened.

  The stopper 36 is sandwiched between the electromagnetic valve 30 and the cylinder 13, and a plurality of communication holes 36 a for communicating the low pressure passage 31 a and the pump chamber 15 are formed.

  A dynamic pressure of DME fuel flowing from the pump chamber 15 toward the low pressure passage 31a (hereinafter referred to as a dynamic pressure during overflow) acts on the valve body 35 in the valve closing direction. Then, the surface of the valve body 35 on the side on which the dynamic pressure at the time of overflow acts is orthogonal to the operation direction X of the valve body 35 (in this example, the direction coincides with the direction of the dynamic pressure at the time of overflow). A slope 35a that is non-parallel to the surface to be formed is formed. Specifically, the slope 35a is a tapered surface (that is, a truncated cone) whose diameter increases at a constant rate along the direction of action of dynamic pressure during overflow. Further, the valve body 35 is formed with a seat surface 35b that comes into contact with and separates from the seat portion 31b of the body 31.

  Here, as shown in FIGS. 3 and 4, DME fuel leaking from between the plunger 14 and the cylinder 13 is applied to the inner wall of the plunger insertion hole 13 a constituting the sliding surface on which the plunger 14 slides in the cylinder 13. A recovery groove 23 for recovery is formed. The collection groove 23 is an annular groove whose diameter is increased in the circumferential direction on the inner wall of the insertion hole 13 a of the cylinder 13.

  The cylinder 13 is formed with a fuel recovery passage 24 that communicates the fuel gallery 19 and the recovery groove 23. The fuel recovery passage 24 constitutes a recovery passage for returning the DME fuel in the recovery groove 23 to the fuel gallery 19. In the middle of the fuel recovery passage 24, a seat surface 24a whose inner periphery is enlarged in a tapered shape toward the fuel gallery 19 side is formed.

  The fuel recovery passage 24 allows a one-way fuel flow of DME fuel from the recovery groove 23 to the fuel gallery 19, and allows the fuel recovery passage 24 to pass until the pressure in the recovery groove 23 becomes equal to or higher than the set valve opening pressure. A passage opening / closing valve 25 is provided as a passage opening / closing means for closing.

  The passage opening / closing valve 25 of the present embodiment has a ball valve body 25a that opens and closes the fuel recovery passage 24 by being brought into contact with and separated from the seat surface 24a of the fuel recovery passage 24, and a direction in which the ball valve body 25a is closed (fuel gallery 19). To the recovery groove 23). Here, one end side of the spring 25b is fixed by a pressing portion 26 that is screwed into the opening of the fuel recovery passage 24 on the fuel gallery 19 side. A fuel passage 26 a is formed in the holding portion 26.

  Here, the set valve opening pressure of the passage opening / closing valve 25 is set to be larger than the pressure in the fuel gallery 19. More specifically, the set valve opening pressure of the passage opening / closing valve 25 is larger than the reference pressure in the fuel gallery 19 defined by the pressure regulating valve 21 and smaller than the presumed maximum pressure in the pump chamber 15. It is set to be. The set valve opening pressure of the passage opening / closing valve 25 can be set by adjusting the urging force of the spring 25b of the passage opening / closing valve 25, the urging force of the spring 21b of the pressure regulating valve 21, and the like.

  The operation of the high-pressure pump 1 having the above configuration will be described. First, when the solenoid 32 of the electromagnetic valve 30 is not energized, the valve body 35 of the electromagnetic valve 30 is moved to the valve open position by the urging force of the spring 34. That is, the seat surface 35b of the valve body 35 is separated from the seat portion 31b of the body 31, and the low-pressure passage 31a is opened.

  In the suction process in which the plunger 14 is lowered while the low-pressure passage 31a is open, the low-pressure DME fuel discharged from the low-pressure supply pump passes through the fuel gallery 19, the low-pressure communication passage 13b, and the low-pressure passage 31a. , Supplied to the pump chamber 15.

  Next, in the discharge process in which the plunger 14 starts to rise, the plunger 14 attempts to pressurize the DME fuel in the pump chamber 15. However, since the solenoid valve 30 is not energized and the low pressure passage 31a is opened at the beginning of the upward movement of the plunger 14, the DME fuel in the pump chamber 15 passes through the low pressure passage 31a and the low pressure communication passage 13b. As a result, it overflows to the fuel reservoir 19 side and is not pressurized.

  When the solenoid valve 30 is energized during the overflow of the DME fuel in the pump chamber 15, the armature 33 and the valve body 35 are sucked against the spring 34, and the seat surface 35 b of the valve body 35 is the seat of the body 31. The low pressure passage 31a is closed by sitting on the portion 31b.

  Thereby, the overflow of the DME fuel to the fuel reservoir 19 side is stopped, and pressurization of the DME fuel in the pump chamber 15 by the plunger 14 is started. Then, the discharge valve 22 is opened by the fuel pressure in the pump chamber 15, and the DME fuel is pumped to the common rail.

  Here, the pressure change in the pump chamber 15 during the operation of the high-pressure pump 1 will be described with reference to FIG. FIG. 5 is an explanatory diagram for explaining the pressure change in the pump chamber 15, and the solid line in the drawing indicates the pressure in the pump chamber. 5 represents the pressure in the recovery groove 23, and the two-dot chain line represents the pressure in the fuel gallery 19.

  As shown in FIG. 5, during the operation of the high pressure pump 1, in the pumping process in which the DME fuel in the pump chamber 15 is pressurized, the pressure in the pump chamber 15 is higher than the pressure in the fuel gallery 19 and the recovery groove 23. To rise. When the pressure in the pump chamber 15 rises to the valve opening pressure of the discharge valve 22, the discharge valve 22 is opened. Then, when the discharge valve 22 is opened, the process proceeds to an intake process in which the pressure in the pump chamber 15 decreases, and the pressure in the pump chamber 15 decreases below the pressure in the fuel gallery 19 and the recovery groove 23.

  In the pumping process, the pressure in the pump chamber 15 rises higher than the pressure in the recovery groove 23, and the differential pressure between the pressure in the pump chamber 15 and the recovery groove 23 increases, and the DME fuel in the pump chamber 15 It becomes easy to leak from the gap between the plunger 14 and the plunger insertion hole 13a.

  Here, in the conventional high-pressure pump, since the fuel gallery and the recovery groove are simply communicated with each other in the fuel recovery passage, the pressure in the recovery groove is substantially the same as the pressure in the fuel gallery. . Therefore, the pressure difference between the pump chamber and the recovery groove is large, and the DME fuel in the pump chamber is likely to leak from the gap between the plunger and the plunger insertion hole of the cylinder.

  On the other hand, in the high-pressure pump 1 of the present embodiment, the passage opening / closing valve 25 is provided in the fuel recovery passage 24 that allows the fuel gallery 19 and the recovery groove 23 to communicate with each other. The pressure is set to be higher than the pressure in the gallery 19.

  Therefore, in the high-pressure pump 1 of the present embodiment, the pressure in the recovery groove 23 (see the alternate long and short dash line in FIG. 5) is greater than the pressure in the fuel gallery 19 (see the alternate long and two short dashes line in FIG. 5). High pressure can be achieved.

  According to this, the pressure difference between the pump chamber 15 and the recovery groove 23 can be reduced as compared with the conventional case, and the DME fuel in the pump chamber 15 becomes difficult to flow into the recovery groove 23. Leakage from the gap between the DME fuel cylinder 13 and the plunger insertion hole 13a can be suppressed.

  As a result, the amount of DME fuel discharged from the high-pressure pump 1 can be sufficiently secured, so that sufficient fuel can be supplied from the high-pressure pump 1 to the injector, and appropriate fuel injection in the injector can be realized. Become.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. Parts that are the same as or equivalent to those in the first embodiment are given the same reference numerals, and descriptions thereof are omitted. Here, FIG. 6 is an enlarged cross-sectional view of the passage opening / closing valve of the present embodiment.

  In the present embodiment, the configuration of the passage opening / closing valve 25 is different from that of the first embodiment. Specifically, as shown in FIG. 6, the passage opening / closing valve 25 of the present embodiment closes the needle valve body 25 c and the needle valve body 25 c that opens and closes the fuel recovery passage 24 by making contact with and separating from the seat surface 24 a. A spring 25d that biases in the direction (the direction from the fuel gallery 19 toward the recovery groove 23) is provided. The set valve opening pressure of the passage opening / closing valve 25 and the biasing force of the spring 25d of the passage opening / closing valve 25 and the spring 21b of the pressure regulating valve 21 are set so as to be larger than the pressure in the fuel gallery 19 as in the first embodiment. It is set by adjusting the biasing force.

  Also in the high pressure pump 1 including the passage opening / closing valve 25 of the present embodiment, the pressure in the recovery groove 23 can be made higher than the pressure in the fuel gallery 19, and compared with the conventional high pressure pump, The differential pressure with the pump chamber 15 can be reduced. Therefore, the same effect as that of the first embodiment can be obtained in the high-pressure pump 1 of the present embodiment.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, Unless it deviates from the range described in each claim, it is not limited to the wording of each claim, and those skilled in the art Improvements based on the knowledge that a person skilled in the art normally has can be added as appropriate to the extent that they can be easily replaced.

  For example, the passage opening / closing valve 25 provided in the fuel recovery passage 24 allows the flow of DME fuel in the direction from the recovery groove 23 toward the fuel gallery 19 and until the pressure in the recovery groove 23 becomes equal to or higher than the set valve opening pressure. Any passage opening / closing means capable of closing the fuel recovery passage 24 can be employed without being limited to those shown in the above embodiments.

13 Cylinder 14 Plunger 15 Pump chamber 19 Fuel gallery 20 Fuel discharge passage (discharge passage)
21 Pressure regulating valve (pressure adjusting means)
23 recovery groove 24 fuel recovery passage 25 passage opening / closing valve (passage opening / closing means)

Claims (3)

A high-pressure pump for DME fuel that pressurizes and discharges DME fuel mainly composed of dimethyl ether,
A cylinder (13);
A plunger (14) arranged to reciprocate in the cylinder (13);
A pump chamber (15) whose volume is changed by reciprocation of the plunger (14) in the cylinder (13);
A fuel gallery (19) for storing the DME fuel supplied to the pump chamber (15);
The cylinder (13) is formed on a sliding surface (13a) on which the plunger (14) in the cylinder (13) slides, and from a gap between the cylinder (13) and the plunger (14). A recovery groove (23) for recovering the leaked DME fuel, and a fuel recovery passage (24) for connecting the recovery groove (23) and the fuel gallery (19);
In the fuel recovery passage (24), the flow of the DME fuel in the direction from the recovery groove (23) toward the fuel gallery (19) is allowed, and the pressure in the recovery groove (23) is set open. A high-pressure pump for DME fuel is provided with passage opening / closing means (25) configured to close the fuel recovery passage (24) until the pressure becomes higher than the pressure.   2. The DME fuel use according to claim 1, wherein the set valve opening pressure of the passage opening / closing means (25) is set to be higher than the pressure in the fuel gallery (19). High pressure pump. A discharge passage (20) for communicating the fuel gallery (19) with the outside and discharging the DME fuel in the fuel gallery (19) to the outside;
The discharge passage (20) is provided with pressure adjusting means (21) for opening the discharge passage (20) so that the pressure in the fuel gallery (19) is equal to or lower than a reference pressure.
The high-pressure pump for DME fuel according to claim 1, wherein the set valve opening pressure of the passage opening / closing means (25) is set to be higher than the reference pressure.

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