JPH0777166A - Hydraulic diaphragm pump - Google Patents

Abstract

PURPOSE:To prevent a pump discharge rate from decreasing by discharging air out of an oil operating chamber with certainty. CONSTITUTION:An oil operation chamber 11 and a pump chamber 12 is partitioned by means of a diaphragm 8 in an air-tight condition in a space of a pump main body 1. A plunger 7 is reciprocatively inserted into a cylinder 6 continued from an oil operation chamber 11, and a transferring flow passage is connected to the pump chamber 12. An oil suction port 28 is arranged on a lower portion of a side wall of the cylinder 6, while an oil discharge port 26 is arranged on an upper portion thereof. An oil suction valve 29 is arranged in the oil suction port 28, while an oil discharge valve 27 is arranged in the oil discharge port 26. Oil is flowed into the oil operation chamber 11 through the oil suction valve 29 and the suction port 28 in a terminal period of the pump suction process. Oil is then discharged through the oil discharge valve 27 and the oil discharge port 26 in an initial period of the pump discharge process.

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, in a fuel injection system of a gasoline engine, a high fuel pressure is being studied (for example, from 250 KPa to 10 MPa), and there is a hydraulic diaphragm pump as a pump capable of pumping gasoline at a high pressure. FIG. 2 shows a conventional hydraulic diaphragm pump (for example, Japanese Utility Model Publication No. 55-88088, Japanese Patent Publication No. 1-381).
No. 98), the pump body 2, the cylinder member 4, and the cover 3 are sequentially connected to form the pump main body 1. The pump body 2 and the cylinder member 4 form a plunger chamber (cam chamber) 5 It is formed. Cylinder member 4
A cylindrical cylinder 6 projecting into the plunger chamber 5 is integrally formed in the upper part of the, and a plunger 7 is inserted into the cylinder 6 in a reciprocally movable and airtight state 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. 2, a diaphragm 8 and a backup plate 9 are hermetically sandwiched between a cylinder member 4 and a cover 3, and a large number of oil passage holes 10 extending substantially horizontally are formed in the backup plate 9. Is formed. The diaphragm 8 is arranged between the backup plate 9 and the cover 3, and the space formed between the cylinder member 4 and the cover 3 is divided into an oil working chamber (hydraulic chamber) 11 and a pump chamber 12 by the diaphragm 8. It is airtightly divided (separated). Backup plate 9 is diaphragm 8
The shape of the side surface in contact with is the designed displacement shape of the diaphragm 8 at the bottom dead center. A suction port 13 and a discharge port 14 communicating with the pump chamber 12 are formed in the cover 3, and the suction port 13 is communicated with a discharge port of an in-tank type feed pump 17 in the fuel tank 16 via a suction pipe 15, Outlet 14 of chamber 12
Is communicated with a delivery pipe (not shown) of the engine through a discharge pipe 18. A suction side check valve 19 and a discharge side check valve 20 are provided in the suction pipe 15 and the discharge pipe 18, respectively, and the suction side check valve 19 causes the fluid to flow only from the feed pump 17 to the pump chamber 12 and the discharge side check valve. 20 makes the fluid flow only from the pump chamber 12 to the delivery pipe.

An oil replenishment port 21 is formed in the upper part of the side wall of the cylinder 6 and near the bottom dead center of the tip of the plunger 7 (the position on the leftmost solid line in FIG. 2).
The lower end of the oil pipe 22 is communicated with. 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. Oil working chamber 11
Is filled with oil from the oil chamber 23, and the oil refill port 21 is opened and closed by the cylindrical side surface of the plunger 7 moving inside the oil refill port 21. When the plunger 7 is at the bottom dead center, the oil refill port 21 is completely opened, and the oil chamber 23 and the oil working chamber 11 are communicated with each other. An oil communication pipe is provided at the bottom of the oil chamber 23.
The upper end of 24 is connected, and the oil communication pipe 24 is the pump body 2
And extends downward, and the lower end of the oil communication pipe 24 communicates with the upper end of the plunger chamber 5. 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. 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. 2). Then, the pump action is performed.
When the plunger 7 moves from the bottom dead center to the top dead center, while the tip of the plunger 7 closes the oil replenishment port 21 and then moves to the top dead center, the oil corresponding to the stroke volume of the plunger 7 is collected. The oil is sent through the oil passage hole 10 of the backup plate 9 to a 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 high pressure and discharged to the discharge pipe 18. 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.

Oil leaks from the oil working chamber 11 during the pump discharge process, and the leaked oil is replenished every time the oil replenishment port 21 is opened near the bottom dead center of the plunger 7. The oil refill port 21 is located above the oil working chamber 11, and the air in the oil working chamber 11 moves to the oil chamber 23 through the oil refilling port 21 and the oil refilling pipe 22. However, due to the reciprocating movement of the plunger 7, the oil in the oil replenishment pipe 22 reciprocates up and down, so that the air that has just moved from the oil working chamber 11 to the oil replenishment pipe 22 is generated especially when the engine rotates at a high speed of 2000 rpm or more. During the pump suction stroke, the oil that flows through the oil replenishment pipe 22 toward the oil working chamber 11 rides on and returns to the oil working chamber 11. In this way, the air is not discharged and remains in the oil working chamber 11 to reduce the pump discharge amount.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent air in an oil working chamber from being reliably discharged in a hydraulic diaphragm pump and prevent a decrease in pump discharge amount.

[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 closed by the diaphragm (8).
(11) and pump chamber (12) are airtightly divided, and the plunger (7) is reciprocally inserted into the cylinder (6) that is connected to the oil working chamber (11), and the pump chamber (12) The transfer channel is connected to the oil intake port (28) at the bottom of the side wall of the cylinder (6).
And an oil discharge port (26) is formed in the upper part of the side wall, and an oil suction valve (29) is arranged in the oil suction port (28).
The technical means is that the oil discharge port (26) is provided with an oil discharge valve (27).

[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. Oil flows into the oil working chamber (11) through the oil suction valve (29) and suction port (28) at the end of the pump suction stroke, and the oil discharge valve (27) and oil discharge port at the beginning of the pump discharge stroke. Oil is discharged through (26).

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A configuration of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the hydraulic diaphragm pump of the present invention. The same parts as those of the conventional example shown in FIG. 2 are designated by the same reference numerals and the description thereof is omitted in principle. . In the embodiment, as shown in FIG. 1, an oil discharge port 26 is formed at the position of the oil replenishment port 21 of the conventional example, and the oil discharge port 26 is opened above the plunger chamber 5 and An oil discharge valve 27 is provided. The oil discharge valve 27 is composed of a check valve and allows oil to flow only from the oil working chamber 11 to the plunger chamber 5. The oil discharge port 26 is formed on the upper side wall of the cylinder 6, but an oil suction port 28 is formed on the lower side wall of the cylinder 6 at a position facing the oil discharge port 26 (just below the oil discharge port 26).
An oil intake valve 29 is provided in the oil intake port 28,
Furthermore, one end of the oil suction pipe 30 is communicated. Oil suction pipe
30 extends upward from the lower side of the cylinder 6 through the side portion,
The other end (upper end) of the oil suction pipe 30 penetrates through the upper wall of the pump body 2 and the bottom of the oil chamber 23
22 was communicated with)). Oil intake valve
Reference numeral 29 is a check valve and allows oil to flow only from the oil chamber 23 to the oil working chamber 11 through the oil suction pipe 30.

In the hydraulic diaphragm pump of the embodiment, when the oil suction port 28 is opened by the tip of the plunger 7 at the end of the pump suction stroke, the oil in the oil chamber 23 is the oil suction pipe 30, the oil suction valve. 2
9, through the oil suction port 28, flows into the oil working chamber 11 (inside the cylinder 6). Then, when the oil discharge port 26 is closed by the tip of the plunger 7 at the beginning of the pump discharge stroke, the oil in the oil working chamber 11 passes through the oil discharge valve 27 and the oil discharge port 26, and the plunger chamber 5
Spill to. In this way, the oil flow is in the oil working chamber 11 → oil discharge valve 27 → oil discharge port 26 → plunger chamber 5 → oil port 25 → oil communication pipe 24 → oil chamber 23 → oil suction pipe 30 → oil suction valve 29 → Oil suction port 28 → Only one side of the oil working chamber 11 flows. Therefore, once the oil discharge valve 27
The air flowing out to the oil discharge port 26 does not return and flow into the oil working chamber 11 again. Oil drain valve 27
・ Air flowing out to the oil discharge port 26
The oil enters the oil chamber 23 from 11 through the oil port 25 and the oil communication pipe 24, and is discharged from the oil chamber 23 to the atmosphere.

[0012]

In the hydraulic diaphragm pump of the present invention, an oil suction port is formed in the lower part of the side wall of the cylinder and an oil discharge port is formed in the upper part of the side wall, and an oil suction valve is arranged in the oil suction port. An oil discharge valve is provided in the oil discharge port. Then, at the end of the pump suction stroke, oil flows into the oil working chamber through the oil suction valve and suction port, and is discharged through the oil discharge valve and oil discharge port at the beginning of the pump discharge stroke. In this way, the oil flows only to one side, and the air in the oil working chamber is reliably discharged, so that it is possible to prevent the pump discharge amount from decreasing.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a conventional hydraulic diaphragm pump.

[Explanation of symbols]

 1 Pump body 6 Cylinder 7 Plunger 8 Diaphragm 11 Oil working chamber 12 Pump chamber 26 Oil discharge port 27 Oil discharge valve 28 Oil suction port 29 Oil suction valve

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 a hydraulic diaphragm pump to which a flow path is connected, an oil suction port is formed in the lower part of the side wall of the cylinder and an oil discharge port is formed in the upper part of the side wall, and an oil suction valve is arranged in the oil suction port. A hydraulic diaphragm pump, in which an oil discharge valve is provided.