JPH05187360A - Diaphragm pump - Google Patents

Abstract

PURPOSE:To stabilize pump discharge quantity by securing air vent. CONSTITUTION:An oil working chamber 9 and a pump chamber 10 partitioned by a diaphragm 8 are provided, and suction and discharge of fluid are performed by deflection of the diaphragm 8 caused by oil flow in the oil working chamber 9 in accordance with a reciprocating motion of a plunger 7. An oil replenishing passage 22 communicated with a lower part of the oil working chamber 9 and an oil pump 23 arranged in the replenishing passage 22 are provided. An oil discharge port 24 opened/closed by the reciprocating motion of the plunger 7 when the plunger 7 is in proximity to a bottom dead point thereof is provided at an upper part of a cylinder wall 5 where the plunger 7 is insertingly fitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic diaphragm pump which sucks and discharges a fluid by bending the diaphragm by the flow of oil accompanying the displacement of a plunger.

[0002]

2. Description of the Related Art Generally, in such a diaphragm pump, the oil pressure in the oil working chamber is increased or decreased by the reciprocating motion of a plunger (or a piston), which reciprocates the diaphragm to pump the fluid. When air accumulates in the oil working chamber, the reciprocating stroke of the plunger and the reciprocating stroke of the diaphragm are deviated, and the pump discharge amount becomes unstable. A conventional diaphragm pump that has dealt with such a problem is provided with a refueling / air vent hole in a cylinder wall into which a plunger is reciprocally fitted, and when the plunger reaches the vicinity of bottom dead center, the refueling / air vent hole There is one that releases (for example, see Japanese Patent Publication No. 1-38198).

[0003]

According to the conventional diaphragm pump, the air in the oil is naturally discharged by its buoyancy, so that the air bleeding tends to be insufficient and a stable pump discharge amount can be obtained. Hateful.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a diaphragm pump capable of ensuring air bleeding and stabilizing the pump discharge amount. is there.

[0005]

A diaphragm pump according to the present invention for solving the above-mentioned problems has an oil working chamber and a pump chamber defined by a diaphragm, and a reciprocating plunger is provided in the oil working chamber. A diaphragm pump that interposes a pump chamber in a fluid transfer passage and sucks and discharges a fluid by bending the diaphragm by the flow of oil in the oil working chamber accompanying the reciprocating motion of the plunger. The oil replenishment passage communicating with the lower part of the piston, the oil pump provided in this oil replenishment passage, and the upper part of the cylinder wall into which the plunger is reciprocally fitted and which is provided near the bottom dead center of the plunger. It is provided with an oil discharge port that is opened and closed by reciprocating motion.

[0006]

In the diaphragm pump, the air in the oil in the oil working chamber is discharged from the oil discharge port that opens and closes as the plunger reciprocates. The air discharged at this time is positively discharged together with the oil around the air by the oil being pumped into the oil working chamber by the oil pump.

[0007]

An embodiment of the present invention will be described with reference to the drawings. The diaphragm pump of this embodiment is used, for example, in a high-pressure fuel injection system of an engine. The state during the discharge stroke is shown in FIG. 1 and the state near the bottom dead center is shown in FIG. ing. The pump body 1 includes a body body 2, a cover 3 that covers an open side surface of the body body 2, and a cylinder member 4 that is interposed between the body body 1 and the cover 3. The cylinder member 4 has a cylindrical cylinder wall 5 formed on the body side thereof. An oil chamber 6 is formed by the cylinder member 4 and the body body 2. A drive mechanism (not shown) for a plunger 7, which will be described later, is incorporated in the oil chamber 6 and oil is loaded therein. A plunger 7 is reciprocally fitted in the cylinder wall 5. The plunger 7 is reciprocated by the drive mechanism. A diaphragm 8 is provided between the cover 3 and the cylinder member 4.
Is sandwiched between. The diaphragm 8 partitions the cover 3 and the cylinder member 4 into an oil working chamber 9 and a pump chamber 10 in a sealed state. The cylinder wall 5 is eccentric with respect to the diaphragm 8 so that the upper wall surface of the oil working chamber 9 and the upper wall surface of the cylinder wall 5 are substantially flush with each other. This causes the air in the oil to collect on the upper wall surface.

A suction port 11 and a discharge port 12 communicating with the pump chamber 10 are formed in the cover 3. The suction port 11 and the discharge port 12 are respectively provided with a suction valve 13 and a discharge valve 14 which are check valves. Further, the suction port 11 is communicated with a discharge port of an in-tank feed pump 17 in the fuel tank 16 via a fluid suction passage 15. With this feed pump 17, the pump chamber 10
The fuel pressure inside is the feed pressure Pa. The feed pressure Pa is set to about 250 kPa, for example. The discharge port 12 is communicated with a delivery pipe (not shown) of the engine via a fluid discharge passage 18. The discharge pressure Pb of the fuel discharged to the fluid discharge passage 18 is, for example, about 1
It is set to 0 MPa. The fluid suction passage 15 and the fluid discharge passage 18 correspond to the fluid transfer passage in the present invention.

An oil replenishing hole 20 communicating with the oil working chamber 9 is provided in the lower portion of the cylinder member 4.
An oil replenishment valve 21 which is a check valve is provided in the replenishment hole 20.
Is provided. The oil replenishment valve 21 is a cylindrical case 2
1a, a ball 21b charged therein, and the ball 21b
And a spring 21c for urging the valve in the closing direction. Further, the oil replenishing valve 21 opens when the pressure in the oil working chamber 9 becomes less than the valve opening pressure Pc. The valve opening pressure Pc is set to Pc = Pa-Pd. It should be noted that Pd is a pressure necessary for the diaphragm 8 to bend by a predetermined amount, and the predetermined amount here is the maximum deflection amount of the design value of the diaphragm 8. Furthermore, the oil replenishment valve 21 is installed in the oil working chamber 9.
An oil replenishment path 22 communicating with the oil chamber 6 is communicated via the. In the oil replenishment path 22, the oil chamber 6
Oil pump 23 for pressure-feeding the oil in the oil working chamber 9
Is intervening. The oil discharge pressure Pe of the oil pump 23 is set below the valve opening pressure Pc of the oil replenishing valve 21.

An oil discharge port 24, which is opened and closed by the outer surface of the reciprocating plunger 7, is opened at the upper part of the circumference of the cylinder wall 5. The discharge port 24 connects the oil working chamber 9 and the oil chamber 6 at the time of bottom dead center of the plunger 7 and at the time of opening at the vicinity thereof.

In the above-mentioned diaphragm pump, the plunger 7 moves to the right in the drawing from the bottom dead center (see FIG. 2) during the discharge stroke, so that the oil discharge port 24 is closed and the oil in the oil working chamber 9 is closed. Is boosted. At this time, the oil replenishment valve 21 is closed by the urging force of the built-in spring 21c and the pressure increase of the oil, and the pressure Pf in the oil working chamber 9 becomes substantially equal to the fuel discharge pressure Pb. Then, the diaphragm 8 is bent toward the right cover 3 side as shown in FIG. 1 by the flow of oil accompanying the movement of the plunger 7. As a result, the pump chamber 1
When the fuel in 0 rises and exceeds the pressure for closing the discharge valve 14, the discharge valve 14 is opened, and the fuel is discharged from the discharge port 12 to the fuel discharge passage 18 at a predetermined fuel discharge pressure Pb.

Then, in the suction stroke, as the plunger 7 moves from the top dead center to the left in the drawing, the oil working chamber 9
The pressure Pf becomes lower than the pressure in the pump chamber 10, and the diaphragm 8 is pulled toward the cylinder member side. As a result, the pressure in the pump chamber 10 decreases, the discharge valve 14 closes, the suction valve 13 opens, and the fuel is pumped through the suction port 11
Inhaled to 0. At this time, the pressure in the pump chamber 10 is maintained at the feed pressure Pa by the feed pump 17.
Therefore, even if the fuel contains air, a high fuel filling efficiency can be obtained, and thus the pump efficiency is improved.

The pressure Pf in the oil working chamber 9 during the suction process and while the oil discharge port 24 is closed is
If the pressure for bending the diaphragm 8 is represented by Pg, the pressure is approximately equal to the pressure obtained by Pa-Pg. For this reason, the oil replenishing valve 21 remains closed, so that the pump chamber 10 is filled with fuel due to the pressure difference between the pressure Pf in the oil working chamber 9 and the pressure in the pump chamber 10. The pressure Pg for bending the diaphragm 8 is smaller than the pressure Pd for bending the diaphragm 8 by a predetermined amount.

When the plunger 7 further moves to the left in the drawing, the diaphragm 8 further bends, and the oil discharge port 24 is opened as the plunger 7 approaches the bottom dead center. At this time, the pressure Pf in the oil working chamber 9 becomes almost atmospheric pressure, and becomes equal to or lower than the pressure obtained by Pa−Pg. Therefore, the oil replenishment valve 21 is opened, the oil is pumped into the oil working chamber 9 by the oil pump 23, and the air is positively discharged from the oil discharge port 24 together with the oil around the upper wall surface of the cylinder wall 5. It In this way, the oil in the oil working chamber 9 is replaced with new oil that does not contain air. As a result of the above-described operation, air can be reliably removed from the oil working chamber 9 as compared with the conventional one, so that a stable pump discharge amount can be obtained for each stroke.

If oil leaks from between the plunger 7 and the cylinder wall 5 during the discharge stroke,
Before the oil discharge port 24 opens, the pressure in the oil working chamber 9 becomes equal to or lower than the pressure required by Pa-Pd, and therefore, the insufficient oil is replenished each time. Oil replenishment valve 2
Since the valve opening pressure Pc of 1 is the pressure required by Pa-Pd, it is possible to avoid the deterioration of durability due to the addition of extra stress to the diaphragm 8. Further, since the upper wall surface of the oil working chamber 9 and the upper wall surface of the cylinder wall 5 are substantially flush with each other, air easily collects in the peripheral portion of the upper wall surface of the cylinder wall 5 having the oil discharge port 24, so that air can be removed easily. You can do it even more effectively.

[0016]

According to the present invention, the oil in the oil working chamber is positively discharged from the oil discharge port by pumping the oil into the oil working chamber by the oil pump. Withdrawing is reliable, and a stable pump discharge amount can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a diaphragm pump.

FIG. 2 is a cross-sectional view showing an air bleeding state.

[Explanation of symbols]

 5 Cylinder Wall 7 Plunger 8 Diaphragm 9 Oil Working Chamber 10 Pump Chamber 22 Oil Replenishing Path 23 Oil Pump 24 Oil Discharge Port

Claims (1)

[Claims] 1. A reciprocating motion of the plunger having an oil working chamber and a pump chamber defined by a diaphragm, a plunger for reciprocating the oil working chamber, and the pump chamber being interposed in a fluid transfer passage. A diaphragm pump that sucks and discharges a fluid by bending the diaphragm by the flow of oil in the oil working chamber, and an oil replenishing passage communicating with the lower part of the oil working chamber and provided in the oil replenishing passage. And an oil discharge port provided on the upper portion of a cylinder wall into which the plunger is reciprocally fitted and which is opened and closed by the reciprocating motion of the plunger near the bottom dead center of the plunger.