JPH05296151A - Diaphragm pump - Google Patents

Abstract

PURPOSE:To prevent the excessive deformation, plastic deformation and destruction of a diaphragm by detecting the lowering of feed pressure and feed pump discharge pressure and the abnormal displacement of the diaphragm or abnomality such as the defective operation of the feed pump, and preventing excess oil from flowing into an oil operating chamber from an oil replenishing hole at the time of the above-mentioned abnormality being generated. CONSTITUTION:The space in a pump body 1 is airtightly partitioned into an oil operating chamber 9 and a pump chamber 10 by a diaphragm 7, and a plunger 6 is inserted in the freely reciprocating state into a cylinder 4a provided in line with the oil operating chamber 9. An oil replenishing hole 19 is formed at the side wall of the cylinder 4a, and the pump chamber 10 is communicated with a feed pump 17 through an inlet valve 13 and an inlet pipe 15. An oil cutoff valve 26 is then disposed in the outer opposed position to the oil replenishing hole 19. Sensors 20, 23, 24 for detecting the abnormality of the feed pump 17 are disposed, and the oil cutoff valve 26 is closed according to the abnormality detection signals of the sensors.

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 in-cylinder injection for directly injecting fuel into a cylinder of an engine and which reciprocates a diaphragm by hydraulic pressure to pump a fluid. Is.

[0002]

2. Description of the Related Art At present, in a fuel injection system of a gasoline engine, the fuel pressure is being increased. First
The present applicant has applied for a patent for a hydraulically driven diaphragm pump that is a pump capable of pumping gasoline at high pressure into a cylinder of an engine (Japanese Patent Application No. 4-64618).
I went. In the diaphragm pump (see FIG. 2) of this prior application (not yet published), the body body 2, the cylinder member 4
Further, the cover 3 and the cover 3 are sequentially connected to form the pump body 1, and the body 2 and the cylinder member 4 form the oil chamber 5. A cylindrical cylinder 4a projecting into the oil chamber 5 is integrally formed at the center of the cylinder member 4, and a plunger 6 is reciprocally inserted in the cylinder 4a in a hermetically sealed state as much as possible. The oil chamber 5 is filled with oil and a plunger drive mechanism (not shown) is incorporated therein, and the plunger drive mechanism applies reciprocating motion to the plunger 6.

As shown in FIG. 2, a diaphragm 7 and a backup plate 8 are hermetically sandwiched between a cylinder member 4 and a cover 3, and a large number of oil passage holes 8a are formed in the backup plate 8. Diaphragm 7
Is disposed between the backup plate 8 and the cover 3, and the space formed between the cylinder member 4 and the cover 3 is defined by the diaphragm 7 and the oil working chamber 9 and the pump chamber.
It is airtightly divided (separated) into 10. The shape of the side surface of the backup plate 8 that is in contact with the diaphragm 7 is a designed displacement shape of the diaphragm 7 at the bottom dead center.

The cover 3 has a suction port communicating with the pump chamber 10.
11 and a discharge port 12 are formed, the suction port 11 is communicated with a discharge port of an in-tank feed pump 17 in a fuel tank 16 through a suction pipe 15, and the discharge port 12 of the pump chamber 10 is discharged through a discharge pipe 18. Is connected to a delivery pipe (not shown) of the engine. A suction valve 13 and a discharge valve 14 which are check valves are provided in the suction pipe 15 and the discharge pipe 18, respectively. The suction valve 13 allows the fluid to flow only from the feed pump 17 to the pump chamber 10, and the discharge valve 14 is a pump. The fluid is circulated only from the chamber 10 to the delivery pipe. An oil replenishment hole 19 is formed near the bottom dead center of the tip of the plunger 6 on the side wall of the cylinder 4a. The oil replenishment hole 19 moves inside the oil replenishment hole 19.
It is opened and closed by the cylindrical side surface of. Oil replenishment hole when the plunger 6 is at the bottom dead center (position indicated by the solid line in FIG. 2)
19 is opened and the oil chamber 5 and the oil working chamber 9 are connected. 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 10) + P2
([Opening pressure required to open intake valve 13] + [Pressure loss in intake pipe 15]) The opening pressure of the discharge valve 14 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 diaphragm pump of the prior application, the diaphragm 6 reciprocates between the bottom dead center and the top dead center (the position indicated by the chain double-dashed line in FIG. 2) to cause the diaphragm 7 to move.
Is driven (reciprocating) to perform a pumping action. During operation of the diaphragm pump, an abnormality such as a lock may occur in the feed pump 17, and the feed pressure P1 of the fuel flowing into the pump chamber 10 may become insufficient. When the feed pressure P1 is less than or equal to the minimum pressure P1min required to press the diaphragm 7 against the backup plate 8, even if the plunger 6 reaches the bottom dead center, the diaphragm 7 will not reach the predetermined bottom dead center (backup plate shown in FIG. 2). Cannot move to the position where it touches. However, in the vicinity of the bottom dead center of the plunger 6, the oil in the oil chamber 5 flows into the oil working chamber 9 through the oil replenishing hole 19, so that the oil amount in the oil working chamber 9 becomes excessive. Therefore, when the plunger 6 moves to the top dead center by the next discharge stroke, the diaphragm 7 is excessively displaced toward the cover 3 side, the diaphragm 7 is excessively deformed, and when the suction stroke moves to the bottom dead center, the oil is again discharged. It flows into the oil working chamber 9. If such a process continues, the diaphragm 7 is plastically deformed and destroyed.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a hydraulically driven diaphragm pump, which detects abnormalities such as a decrease in feed pressure, a decrease in discharge pressure of the feed pump, an abnormal displacement of the diaphragm or a malfunction of the feed pump. , It prevents excessive oil from flowing into the oil working chamber from the oil refill hole at the time of such an abnormality, and excessive deformation of the diaphragm,
The object is to prevent plastic deformation and fracture. In addition,
As described in claim 2 of the specification relating to the prior application, it is possible to prevent excessive deformation and breakage of the diaphragm by letting the oil in the oil working chamber escape to the outside by the oil relief valve. The invention pays particular attention to the existence of the oil replenishment hole, and attempts to prevent excess oil from flowing into the oil working chamber from the oil replenishment hole.

[0007]

In order to solve the above-mentioned problems, the diaphragm pump of the present invention is constructed such that the space inside the pump body is airtightly divided by a diaphragm into an oil working chamber and a pump chamber. A plunger is reciprocally inserted into the cylinder continuously connected to the cylinder, an oil supplement hole is formed in the side wall of the cylinder, and the pump chamber is communicated with the feed pump through the intake valve and the intake pipe. , An oil cut valve is installed at a position facing each other, and a sensor for detecting an abnormality of the feed pump is installed.
The oil cut valve was made to close according to the abnormality detection signal of the sensor. As a sensor for detecting the abnormality of the feed pump, a first pressure sensor for detecting the pressure in the pump chamber can be provided in the cover, and a second pressure sensor for detecting the pressure in the suction pipe is sucked. It can be arranged in a tube and a current sensor (ammeter) can be arranged in the wiring from the power supply to the feed pump.
Then, one or more of the above-mentioned means can be selected and adopted.

[0008]

When the plunger is reciprocated at a predetermined speed, the pressure in the oil working chamber fluctuates periodically, and the diaphragm is displaced according to the pressure fluctuation. The displacement of the diaphragm causes the volume of the pump chamber to fluctuate, and the pump action is performed. When an abnormality occurs in the feed pump, the sensor detects the abnormality and closes the oil cut valve. When the oil cut valve is closed, replenishment of oil into the oil working chamber is stopped, and excessive displacement of the diaphragm is prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the 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 will be omitted in principle. The cover 3 is provided with a first pressure sensor 20 for detecting the pressure in the pump chamber 10, and an oil replenishment hole 19
An oil cut valve 26 for opening and closing is disposed at a position facing the outside of the oil replenishment hole 19 in the oil chamber 5. The oil cut valve 26 has a solenoid and a valve body 27.When the solenoid is not energized, the valve body 27 comes into contact with the oil replenishment hole 19 to close the oil cut valve 26, and by energizing the solenoid, the valve body 27 is closed. Separate from the oil refill hole 19 and cut off the oil 26
Is opened. The detection signal of the first pressure sensor 20 is ECU
(Electronic control unit) 22 is input and an operation signal for the oil cut valve 26 is output from the ECU 22 to the oil cut valve 26.

A second pressure sensor 23 for detecting the pressure in the suction pipe 15 is provided in the suction pipe 15 at a position upstream of the suction valve 13, and wiring from a power source (battery) 25 to the feed pump 17 is provided. (In FIG. 1, it is abstracted and shown by one line.)
A current sensor (ammeter) 24 is provided in the ECU 22, and detection signals of the second pressure sensor 23 and the current sensor 24 are input to the ECU 22, respectively. First pressure sensor 20, second pressure sensor 23
Alternatively, the current sensors 24 are all for detecting an abnormality of the feed pump 17, and one or more of them may be selected and arranged.

Next, the operation of the embodiment of the present invention will be described. When normal, the oil cut valve 26 is open, and when the plunger drive mechanism moves the plunger 6 from the bottom dead center to the right in FIG. 1 and enters the discharge stroke of the diaphragm pump, the oil refill hole 19 first opens the plunger 6 Closed by. The oil working chamber 9 follows the movement of the plunger 6.
The oil inside is pressurized, the diaphragm 7 is displaced to the cover 3 side, and the fuel in the pump chamber 10 is pressurized. As a result, the pressure in the pump chamber 10 rises above the feed pressure P1,
When the pressure that closes the discharge valve 14 is exceeded, the discharge valve 14 is opened, and fuel is discharged from the pump chamber 10 to the discharge pipe 18 at a discharge pressure of, for example, 100 bar or more. During this discharge stroke, the oil in the oil working chamber 9 leaks to the oil chamber 5 through the gap between the plunger 6 and the cylinder 4a, though a small amount. After that, the plunger 6 reaches the top dead center indicated by the chain double-dashed line in FIG.

When the plunger 6 moves from the top dead center to the left in FIG. 1 and shifts to the suction stroke, the pressure in the oil working chamber 9 decreases, and accordingly, the pressure in the pump chamber 10 lowers and discharges. The valve 14 is closed. When the pressure in the pump chamber 10 further decreases to the feed pressure P1 or less, the suction valve 13 opens, and the fuel sent by the feed pump 17 is sucked into the pump chamber 10. Due to the pressure difference between the feed pressure P1 and the pressure in the oil working chamber 9, the diaphragm 7 moves to the back plate 8 side. When the plunger 6 approaches the bottom dead center, the oil replenishment hole 19 is opened by the plunger 6, so that the oil that has leaked through the gap between the plunger 6 and the cylinder 4a during the discharge stroke is replenished in the oil working chamber 9. ..

As described above, when the plunger 6 is at the bottom dead center, the oil replenishment hole 19 is fully opened by the plunger 6, so that the pressure in the oil working chamber 9 is the pressure in the oil chamber 5 (atmospheric pressure). And the pressure in the pump chamber 10 is equal to the feed pressure P1. At this time,
Due to the pressure difference between the internal pressure of the pump chamber 10 and the internal pressure of the oil working chamber 9, the diaphragm 7 is deformed and moved to the oil working chamber 9 side, and is pressed against the backup plate 8 as shown by the solid line in FIG. Therefore, the extra stress applied to the diaphragm 7 by the feed pressure of the feed pump 17 is received by the backup plate 8, so that the diaphragm 7 is prevented from being excessively deformed, and by extension, the damage due to the deformation is prevented.

When the feed pressure P1 falls below the minimum required pressure P1min due to a failure of the feed pump 17 or the like, the plunger 6 approaches the bottom dead center and before the oil replenishment hole 19 is opened by the plunger 6, for example, the first pressure sensor. 20 detects an abnormality. The abnormality detection signal from the first pressure sensor 20 is ECU
The solenoid of the oil cut valve 26 is de-energized by the operation signal from the ECU 22 and the oil cut valve is processed.
26 is closed. Therefore, the replenishment of the oil to the oil working chamber 9 thereafter is stopped, the excess oil does not flow into the oil working chamber 9, and the diaphragm is excessively deformed,
Prevents plastic deformation and fracture.

When an abnormality is detected by the second pressure sensor 23, the pressure in the suction pipe 15 is equal to the above [P1min (the minimum required feed pressure P1) + P2 (the opening pressure required to open the suction valve 13). )] In the following cases, the second pressure sensor 23 detects the abnormality, and the abnormality detection signal from the second pressure sensor 23 closes the oil cut valve 26. When the current sensor 24 detects an abnormality, the feed pump 17 is locked (at this time, the feed pressure decreases).
The oil cut valve 26 is closed by the abnormality detection signal from the current sensor 24, which is detected by the abnormal value of the drive current of 17. When detecting an abnormal displacement of the diaphragm 7, an appropriate position detection sensor is provided in the pump chamber 10,
The oil cut valve 26 is set to be closed according to the abnormality detection signal from the position detection sensor. Second pressure sensor
When the abnormality is detected by the current sensor 24 and the current sensor 24, excessive deformation, plastic deformation and breakage of the diaphragm are prevented in the same manner as when the first pressure sensor 20 detects the abnormality.

[0016]

In the diaphragm pump of the present invention, the oil cut valve is provided at the opposite position outside the oil refill hole, the sensor for detecting the abnormality of the feed pump is provided, and the abnormality detection signal of the sensor is provided. The oil cut valve is closed accordingly. Therefore, when the feed pressure or the discharge pressure of the feed pump decreases due to a failure of the feed pump, etc., the oil cut valve is closed without delay, the oil replenishment to the oil working chamber is stopped, and the oil working chamber is stopped. Excessive oil does not flow in, and excessive deformation, plastic deformation and breakage of the diaphragm are prevented.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of a conventional diaphragm pump.

[Explanation of symbols]

 1 Pump body 4a Cylinder 6 Plunger 7 Diaphragm 9 Oil working chamber 10 Pump chamber 13 Suction valve 15 Suction pipe 17 Feed pump 19 Oil refill hole 20 First pressure sensor 23 Second pressure sensor 24 Current sensor 26 Oil cut valve

Claims (1)

[Claims] 1. A space in a pump body is airtightly divided into an oil working chamber and a pump chamber by a diaphragm, and a plunger is reciprocally inserted into a cylinder connected to the oil working chamber, and a side wall of the cylinder. In the diaphragm pump in which an oil refill hole is formed in the pump chamber and the pump chamber communicates with the feed pump through the suction valve and the suction pipe,
An oil cut valve is provided at an opposite position outside the oil refill hole, a sensor for detecting an abnormality of the feed pump is provided, and the oil cut valve is closed according to an abnormality detection signal of the sensor. Diaphragm pump.