JP2933767B2 - Diaphragm pump - Google Patents

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 for use in, for example, a high-pressure fuel injection system of an engine and for pumping a fluid such as fuel by reciprocating a diaphragm by hydraulic pressure.

[0002]

2. Description of the Related Art An example of a conventional diaphragm pump will be described with reference to FIG . The box-shaped pump body 18 includes a body body 18a, a cover 11 that covers an open side surface thereof, and the cylinder 2 interposed between the body 18a and the cover 11. The cylinder 2 has a cylindrical cylinder wall 2a at the center thereof and the wall 2a.
a has a flange portion 2b that protrudes on the outer periphery. The oil chamber 1 is located between the cylinder 2 and the body 18a.
9 are formed. The oil chamber 19 accommodates a drive mechanism 15 described later and is loaded with oil. Further, a diaphragm 9 is sandwiched between the flange 2 b of the cylinder 2 and the cover 11. The diaphragm 9 includes the flange 2b and the cover 1
1 is partitioned into an oil working chamber 8 on the cylinder side and a pump chamber 10 on the cover side in a sealed state.

The suction port 27 and the discharge port 26 communicating with the pump chamber 10 are respectively provided with a suction valve 17 and a discharge valve 16 which are check valves. Although not shown, the suction port 27 is connected to a pressure source of a fluid (for example, fuel), and the discharge port 26 is connected to a fluid supply unit (for example, a delivery pipe of an engine). The body main body 18a is provided with a cylinder portion 24 located at a substantially central portion so as to be coaxial with the cylinder wall 2a. The tappet 3 is slidably fitted to the cylinder portion 24. The plunger 1 is mounted on a surface of the tappet 3 facing the cylinder wall 2a by a mounting plate 20. The plunger 1 is connected to the cylinder wall 2
a is reciprocally inserted into the a. Tappet 3
A spring 7 for urging the plunger 1 together with the tappet 3 in the retreating direction (leftward in the figure) is interposed between the cylinder and the cylinder 2.

A rolling roller 4 is rotatably supported on the tappet 3 by a support pin 22. A drive shaft 6 having an eccentric cam 5 is rotatably mounted on the body body 18a. The rolling roller 4 is in contact with the outer peripheral surface of the eccentric cam 5 by the urging force of the spring 7. The drive shaft 6 includes an external drive source,
For example, it is connected to an electric motor so that power can be transmitted. Accordingly, the eccentric cam 5 rotates together with the drive shaft 6 by the driving of the external drive source, and the rolling roller 4 rotates along the outer periphery of the cam 5 to reciprocate the tappet 3. As described above, the drive mechanism 15 mainly includes the eccentric cam 5 and the rolling roller 4,
The drive mechanism 15 is immersed in the oil in the oil chamber 19. The cylinder wall 2a has an oil supply hole 12 that can be opened and closed by the outer surface of the reciprocating plunger 1. The replenishing hole 12 connects the oil working chamber 8 and the oil chamber 19 at the time of opening, that is, at the time of the bottom dead center of the plunger 1 and at the time of opening in the vicinity thereof.

In the above-described diaphragm pump, when the drive shaft 6 is rotated by an external drive source, the plunger 1 reciprocates (piston motion) via the drive mechanism 15. When the plunger 1 enters the compression stroke from the bottom dead center, the oil supply hole 12 is closed, and the inside of the oil working chamber 8 becomes airtight. When the compression stroke of the plunger 1 further advances, the oil pressure in the oil working chamber 8 increases, and the diaphragm 9 is pushed toward the pump chamber by the pressure. When the diaphragm 9 is pushed, the discharge valve 16 is opened when the pressure of the fluid in the pump chamber 10 rises and exceeds the pressure for closing the discharge valve 16, and the fluid is discharged from the discharge port 26.
Subsequently, when the plunger 1 enters the suction stroke, the pressure in the oil working chamber 8 drops below the pressure in the pump chamber 10, and the diaphragm 9 is pulled toward the oil working chamber. As a result, the pressure in the pump chamber 10 decreases, the discharge valve 16 closes, and the suction valve 17 opens, so that fluid is sucked into the pump chamber 10 from the suction port 27. As the plunger 1 approaches the vicinity of the bottom dead center, the oil supply hole 12 is opened. As a result, for example, the oil corresponding to the amount leaked from the oil working chamber 8 to the oil chamber 19 through the seal portion between the plunger 1 and the cylinder wall 2a is refilled into the oil working chamber 8 through the oil replenishing hole 12.

[0006]

According to the diaphragm pump, the oil for lubricating the drive mechanism 15 in the oil chamber 19 is replenished to the oil working chamber 8.
Air generated in the oil by the operation of the drive mechanism 15 enters the oil working chamber 8 together with the oil. The cylinder wall 2a of the cylinder 2 and the diaphragm 9 are arranged substantially on the same axis. Therefore, as the operation time elapses, air gradually accumulates in the upper end portion of the oil working chamber 8 (indicated by a two-dot chain line A in FIG. 2 ). Then, it becomes difficult for the pressure in the oil working chamber 8 to rise due to the air in the oil, and the discharge amount of the pump decreases by the amount of the mixed air under high pressure. In an extreme case, the discharge becomes impossible. This means that the pump output becomes unstable,
Pump efficiency will be degraded. Note that a diaphragm pump having a structure different from that of the conventional example is disclosed in
There is one disclosed in JP-A-9-162378.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a stable pump discharge amount even after a long operation, and to perform an efficient pumping operation. It is to provide a diaphragm pump which can be used.

[0008]

A diaphragm pump according to the present invention for solving the above-mentioned problems is provided with a pump chamber and an oil working chamber formed in a pump body and partitioned by a diaphragm, and a suction port communicated with the pump chamber. And a discharge port, a plunger reciprocally fitted in a cylinder wall communicating with the oil working chamber, and an oil chamber in which a driving mechanism for reciprocating the plunger is housed and oil is loaded. An oil replenishing hole opened in the cylinder wall to communicate the oil working chamber and the oil chamber and opened and closed by reciprocating operation of the plunger, wherein the oil replenishing hole is set on an upper wall surface of the cylinder wall. together are, the space portion of the cylinder wall is communicated with the upper end of the oil working chamber, or
The upper wall of the cylinder wall and the upper wall of the oil working chamber
The surface is substantially the same as the surface.

[0009]

According to the diaphragm pump described above, the air that has entered the oil in the oil working chamber rises due to its buoyancy and is discharged into the oil chamber from the oil replenishing hole that is opened and closed with the reciprocating operation of the plunger. It is difficult for air to accumulate in the oil working chamber .

[0010]

An embodiment of the present invention will be described with reference to FIG . In the present embodiment, a part of the conventional example is modified. Therefore, the modified part will be described in detail. Is omitted. In this example, oil supply hole 1
2 is an upper wall surface (symbol,
Add 2A. ) . Further, the cylinder wall 2 a is arranged eccentrically with respect to the diaphragm 9, and a space in the cylinder wall 2 a communicates with an upper end of the oil working chamber 8. Upper wall surface (marks on the wall surface 2A and the oil working chamber 8 of the cylinder wall 2a
Number, 8A. ) Is almost the same plane. According to the diaphragm pump of this embodiment, the air that has entered the oil in the oil working chamber 8 rises due to its buoyancy, and is discharged from the oil replenishing hole 12 that opens at the bottom dead center of each stroke of the plunger 1 to the oil chamber 19. Therefore, it is difficult for air to accumulate in the oil working chamber 8. Therefore, a stable pump discharge amount can be obtained even when the pump is operated for a long time, and an efficient pump operation can be performed.

[0011]

According to the diaphragm pump of the present invention,
Since it is difficult for air to accumulate in the oil working chamber, problems such as a decrease in pump discharge amount due to air or a failure to discharge can be solved, and a stable and efficient pump operation can be performed even after a long operation .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a diaphragm pump according to an embodiment.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plunger 2a Cylinder wall 8 Oil working chamber 9 Diaphragm 10 Pump chamber 12 Oil refill hole 15 Drive mechanism 18 Pump body 19 Oil chamber 26 Discharge port 27 Suction port

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04B 43/06 F04B 53/06

Claims (1)

(57) [Claims] A pump chamber and an oil working chamber formed in the pump body and partitioned by a diaphragm;
A suction port and a discharge port communicating with the pump chamber, a plunger reciprocally fitted in a cylinder wall communicating with the oil working chamber, and a drive mechanism for reciprocating the plunger are housed. An oil chamber in which oil is loaded, and an oil replenishing hole opened in the cylinder wall so as to communicate the oil working chamber and the oil chamber and opened and closed by reciprocating operation of the plunger. There together are set to the upper wall surface of the cylinder wall, communicates at the upper end of the space portion of the cylinder wall the oil working chamber, also, the sheet
The upper wall of the Linda wall and the upper wall of the oil working chamber are almost
A diaphragm pump characterized by having the same surface .