JPH06323257A - Hydraulic diaphragm pump - Google Patents

Abstract

PURPOSE:To prevent the delivery amount of a pump from lowering at low temperatures by returning a diaphragm back to the position at the back-up plate side when a plunger comes at the bottom dead center of a suction stroke even if the viscosity of oil is increased by the lowering of temperature of the atmosphere. CONSTITUTION:A space in a pump main body 1 is divided air-tight into an oil working chamber 11 and a pump chamber 12 by a diaphragm 8, a plunger 7 is inserted reciprocatedly into a cylinder 6 installed connectedly to the oil working chamber 11, and transport flow paths 15 and 18 are connected to the pump chamber 12. Also the diaphragm 8 is held between a back up plate 9 and an upper plate 25 to provide a preset force to return the diaphragm back to the original position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulically driven diaphragm pump which is used, for example, for in-cylinder injection in which fuel is directly injected into a cylinder of an engine and which reciprocates the diaphragm by hydraulic pressure to pump fluid.

[0002]

2. Description of the Related Art At present, a fuel injection system for a gasoline engine is under study for increasing fuel pressure, and as a pump capable of pumping gasoline at a high pressure, there is a hydraulic diaphragm pump. FIG. 4 shows a conventional hydraulic diaphragm pump (see, for example, Japanese Utility Model Laid-Open No. 55-88088 and Japanese Patent Publication No. 1-38198), in which a pump body 2, a cylinder member 4, and a cover 3 are sequentially connected. The pump body 1 is configured by the above, and the plunger chamber 5 is formed by the pump body 2, the cylinder member 4, and the like. A cylindrical cylinder 6 projecting into the plunger chamber 5 is integrally formed above the cylinder member 4, and a plunger 7 is inserted into the cylinder 6 in a reciprocally movable and airtight manner as much as possible. A plunger drive mechanism (not shown) is incorporated in the plunger chamber 5, and the plunger drive mechanism applies a reciprocating motion to the plunger 7.

As shown in FIG. 4, the outer periphery of the diaphragm 8 and the backup plate 9 is hermetically sandwiched between the cylinder member 4 and the cover 3, and the backup plate 9 has a large number of oils extending in a substantially horizontal direction. A passage hole (small hole) 10 is formed. The diaphragm 8 is disposed between the backup plate 9 and the cover 3, and the cylinder member 4
The space formed between the cover and the cover 3 is the diaphragm 8
Thus, the oil working chamber 11 and the pump chamber 12 are airtightly divided (separated) from each other. The shape of the side surface of the backup plate 9 in contact with the diaphragm 8 is a designed displacement shape of the diaphragm 8 at the bottom dead center.

The cover 3 has a suction port communicating with the pump chamber 12.
13 and a discharge port 14 are formed, the suction port 13 is communicated with a discharge port of an in-tank feed pump 17 in a fuel tank 16 via a suction pipe 15, and the discharge port 14 of the pump chamber 12 is discharged via a discharge pipe 18. Is communicated with an engine delivery pipe (not shown). A suction side check valve 19 is provided on the suction pipe 15 and the discharge pipe 18.
And a discharge side check valve 20 are respectively arranged, the suction side check valve 19 allows the fluid to flow only from the feed pump 17 to the pump chamber 12, and the discharge side check valve 20 allows the fluid to flow only from the pump chamber 12 to the delivery pipe. . An oil port 21 is formed on the side wall of the cylinder 6 at a position slightly away from the bottom dead center of the tip of the plunger 7 (the position on the leftmost solid line in FIG. 4), and the lower end of the oil pipe 22 is formed in the oil port 21. Are communicated. The oil pipe 22 extends upward through the pump body 2, and the upper end of the oil pipe 22 communicates with the bottom of the oil chamber 23. The oil working chamber 11 is filled with oil from the oil chamber 23, and the oil port 21 is opened and closed by the cylindrical side surface of the plunger 7 moving inside the oil port 21. When the plunger 7 is at the bottom dead center, the oil port 21 is opened, and the oil chamber 23 and the oil working chamber are opened.
11 is communicated with. The feed pump 17 has a discharge flow rate equal to or larger than the maximum discharge amount of the diaphragm pump, and has a predetermined discharge pressure P3 (for example, about 2.5 to 3.0 bar).
This discharge pressure P3 is the discharge pressure P3 = P1 (fuel feed pressure to the pump chamber 12) + P2
([Valve opening pressure required to open the suction side check valve 19] + [pressure loss of the suction pipe 15]). The valve opening pressure of the discharge side check valve 20 is set to be equal to or higher than the feed pressure, and the suction pipe 15 and the discharge pipe 18 form a transfer flow path.

In the conventional hydraulic diaphragm pump, when the plunger drive mechanism operates, the plunger 7 in the cylinder 6 reciprocates between the bottom dead center and the top dead center (the position of the rightmost dotted line in FIG. 4). Then, the pump action is performed.
When the plunger 7 moves from the bottom dead center to the top dead center, oil corresponding to the stroke volume of the plunger 7 is backed up while the tip of the plunger 7 closes the oil port 21 and then moves to the top dead center. Oil passage hole 10 in plate 9
Through to the portion between the diaphragm 8 and the backup plate 9. The backup plate 9 is installed to prevent excessive deformation of the diaphragm 8, and the diaphragm 8 is displaced by an amount proportional to the compression force of oil. Due to this displacement of the diaphragm 8, the fuel sent from the feed pump 17 is made into a high pressure, and the discharge pipe 18
To discharge. When the plunger 7 moves from the top dead center to the bottom dead center, the oil in the portion between the diaphragm 8 and the backup plate 9 is returned to the oil working chamber 11 through the oil passage hole 10.

However, the ambient temperature is lowered, and, for example,
At 30 ° C., the viscosity of oil increases, the flow resistance when passing through the oil passage hole 10 increases, and the operability deteriorates. Then, when the plunger 7 reaches the bottom dead center of the suction stroke, the diaphragm 8 cannot fully return to the position where it comes into contact with the backup plate 9, and the discharge amount of the hydraulic diaphragm pump decreases, so that the pump performance is reduced. It cannot be secured. As a countermeasure against such a phenomenon, there is a means of increasing the diameter of the oil passage holes 10 of the backup plate 9 or increasing the number of the oil passage holes 10 to increase the oil passage area. However, increasing the diameter of the oil passage holes 10 has a drawback that the diaphragm 8 is easily damaged when the pressure in the pump chamber 12 becomes excessive. It has the drawback of being difficult to manufacture.

[0007]

SUMMARY OF THE INVENTION In a hydraulic diaphragm pump according to the present invention, even when the atmospheric temperature is lowered and the viscosity of oil is increased, the diaphragm is driven when the bottom stroke of the intake stroke of the plunger is reached. It is an object to prevent the pump discharge amount from decreasing at a low temperature by returning it to the position on the side of the backup plate.

[0008]

In order to solve the above-mentioned problems, the hydraulic diaphragm pump of the present invention has a pump body.
The space inside (1) is airtightly divided into the oil working chamber (11) and the pump chamber (12) by the diaphragm (8), and the plunger (6) is connected to the cylinder (6) connected to the oil working chamber (11). (7) is reciprocally inserted, and the transfer channel (15) (1
8) was connected, the diaphragm (8) was sandwiched between the backup plate (9) and the upper plate (25), and the diaphragm (8) was given a preset force to return to its original position as a technical means. There is.

[0009]

[Operation] When the plunger (7) is reciprocated at a predetermined speed, the pressure in the oil working chamber (11) fluctuates periodically, and the diaphragm (8) is displaced according to the pressure fluctuation. The displacement of the diaphragm (8) causes the volume of the pump chamber (12) to fluctuate, and the pumping action is performed. When the temperature decreases, the viscosity of the oil increases, but since the diaphragm (8) has a preset force, the diaphragm (8) is set by the preset force when the plunger (7) reaches the bottom dead center of the suction stroke. You can return to the original position.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A configuration of an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of a hydraulic diaphragm pump of the present invention. The same parts as those of the conventional example shown in FIG. 4 are designated by the same reference numerals as those of the conventional example, and the description thereof is omitted in principle. To do. In the embodiment, as shown in FIG. 2A, the diaphragm 8 and the backup plate 9
And the upper plate 25 are prepared. A central hole 28 is formed in the central portion of the upper plate 25, an annular groove 29 is formed in the outer peripheral portion inside the upper plate 25 (on the side of the diaphragm 8), and a frustoconical portion is formed in the portion excluding the outer peripheral portion. A shaped depression 27 is formed. As shown in FIG. 2B, the diaphragm 8 is sandwiched between the backup plate 9 and the upper plate 25, and the outer peripheral portions of these three members are welded by laser welding or the like. After welding, the portion of the outer side of the backup plate 9 (the left side in FIG. 2B) facing the annular groove 29 of the upper plate 25 (the portion immediately to the left of the annular groove 29 in FIG. 2B) is annularly shaped with a tool. A portion of the backup plate 9 is plastically deformed by pressing it toward the groove 29. At the same time as the concave plastic deformation of the backup plate 9, the diaphragm 8 is pushed into the annular groove 29 of the upper plate 25 and plastically deformed. 8 is given a tensile preset force in the outer diameter direction.This preset force causes the diaphragm 8 to move toward the backup plate 9, and the diaphragm 8 is always in contact with the backup plate 9 at the end of the suction stroke (suction stroke). Ideal condition at the end).

The backup plate 9 shown in FIG. 2 (b)
Annular gaskets 31 and 32 are brought into contact with both sides of the outer peripheral portion of the combined body of the diaphragm 8 and the upper plate 25, and as shown in FIG. 1, they are hermetically sandwiched between the cylinder member 4 and the cover 3. According to this embodiment, since the preset force acts on the diaphragm 8, even when the viscosity of the oil becomes high and the operability deteriorates at low ambient temperature, the diaphragm 8 is moved toward the backup plate 9 side at the end of the suction stroke. It returns to the position of the section and the pump performance is maintained.
Further, even when the pump chamber 12 is out of gas, the oil contained in the portion between the diaphragm 8 and the backup plate 9 due to the preset force that acts on the diaphragm 8 is at the end of the suction stroke. Therefore, it is possible to prevent the diaphragm 8 from being damaged due to excessive swelling.

FIG. 3 shows a modification of the embodiment of the hydraulic diaphragm pump of the present invention. In the modified example, the diaphragm 8, the backup plate 9, and the upper plate 25 are prepared as in the embodiment. Although the diaphragm 8 and the upper plate 25 have the same structure as that of the embodiment, an annular protrusion 30 is formed on the outer peripheral portion of the backup plate 9 at a portion facing the annular groove 29 of the upper plate 25. The backup plate 9, the diaphragm 8 and the upper plate 25 shown in FIG. 3 are sequentially brought into contact with each other and arranged between the cylinder member 4 and the cover 3 of FIG. 1, and the cylinder member 4 and the cover 3 are joined by bolts or the like. By this joining, backup plate 9, diaphragm 8, upper plate
The outer peripheral portion of 25 is sandwiched between the cylinder member 4 and the cover 3 in an airtight manner. At the same time, the portion of the diaphragm 8 facing the annular groove 29 of the upper plate 25 is pushed into the annular groove 29 of the upper plate 25 by the annular protrusion 30 and plastically deformed, so that the diaphragm 8 is given a tensile preset force in the outer diameter direction. With this preset force, the diaphragm 8
Tries to move towards the backup plate 9,
The diaphragm 8 always tries to come into contact with the backup plate 9 at the end of the suction stroke (an ideal state at the end of the suction stroke).

According to the modification of FIG. 3, since the preset force acts on the diaphragm 8, even when the viscosity of the oil becomes high and the operability deteriorates at low ambient temperature, the diaphragm 8 is completed at the end of the suction stroke. Returns to the position on the side of the backup plate 9 and the pump performance is maintained.
Further, even when the pump chamber 12 is out of gas, the oil contained in the portion between the diaphragm 8 and the backup plate 9 due to the preset force that acts on the diaphragm 8 is at the end of the suction stroke. Therefore, it is possible to prevent the diaphragm 8 from being damaged due to excessive swelling.

[0014]

In the hydraulic diaphragm pump of the present invention, the diaphragm is sandwiched between the backup plate and the upper plate, and a preset force for returning the diaphragm to its original position is applied. When the ambient temperature decreases, the viscosity of the oil increases, but since a preset force is applied to the diaphragm, the diaphragm returns to the backup plate side position at the end of the suction stroke,
The pump performance is maintained at a low temperature by preventing the pump discharge rate from decreasing. Even if the pump chamber runs out of gas, the preset force that acts on the diaphragm causes the oil contained between the diaphragm and the backup plate to return to the oil working chamber, causing excessive swelling of the diaphragm. Damage due to can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a hydraulic diaphragm pump of the present invention.

FIG. 2 (a) is a cross-sectional view of three members forming a main part, and FIG. 2 (b) is a cross-sectional view showing a state where the three members are welded and plastically deformed.

FIG. 3 is a cross-sectional view of three members constituting a main part of a modified example of the hydraulic diaphragm pump of the present invention.

FIG. 4 (a) is a sectional view showing an example of a conventional hydraulic diaphragm pump, and FIG. 4 (b) is a plan view of a backup plate.

[Explanation of symbols]

 1 Pump body 6 Cylinder 7 Plunger 8 Diaphragm 9 Backup plate 11 Oil working chamber 12 Pump chamber 15 Suction pipe (conveyance passage) 17 Feed pump 18 Discharge pipe (conveyance passage) 19 Suction side check valve 25 Upper plate

Claims (1)

[Claims] 1. A space in a pump body is partitioned into an oil working chamber and a pump chamber in an airtight manner by a diaphragm, and a plunger is reciprocally inserted into a cylinder connected to the oil working chamber and conveyed to the pump chamber. In the hydraulic diaphragm pump to which the flow path is connected, the diaphragm is sandwiched by the backup plate and the upper plate,
A hydraulic diaphragm pump characterized by being given a preset force for returning the diaphragm to its original position.