JPH05321841A - Diaphragm type pump - Google Patents

Abstract

PURPOSE:To prevent a diaphragm from being excessively displaced and broken by providing an overflow passage for overflowing an operating liquid from an operating liquid chamber, and providing a control valve for opening or closing the overflow passage on the overflow passage. CONSTITUTION:A plunger 14 is lowered to reduce the oil pressure in an oil chamber 12, and a diaphragm 10 is displaced downward. The fuel pressure in a pump chamber 11 is reduced by this displacement, a discharge quantity control valve 20 is opened, and the fuel pressurized by a feed pump 23 is fed into the pump chamber 11. The plunger 14 is lifted to increase the oil pressure in the oil chamber 12, and the diaphragm 10 is displaced upward. The discharge quantity control valve 20 is closed by this displacement, the fuel pressure in the pump chamber 11 is increased, a check valve 29 is opened, and fuel is discharged. When the fuel pressure detected by a feed fuel sensor 26 becomes lower than a preset value, an overflow control valve 18 is opened, the operating liquid in the oil chamber 12 is overflowed through an overflow passage 17, and the excessive displacement of the diaphragm 10 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm type pump.

[0002]

2. Description of the Related Art Japanese Utility Model Laid-Open No. 55-88088 discloses a pump chamber and an oil chamber defined by a diaphragm, which is connected to a cylinder into which a plunger is inserted and which is filled with oil. In addition to being connected to the oil reservoir chamber, the plunger reciprocates in the cylinder to periodically change the oil pressure in the oil chamber so that the liquid supplied into the pump chamber can be discharged from the discharge port of the pump chamber. A diaphragm type pump is disclosed.

[0003]

In such a diaphragm type pump, when the liquid supplied into the pump chamber is a liquid pressurized to a substantially constant pressure, the pressure of the pressurized liquid is, for example, the liquid supply. If the pressure drops excessively due to a system abnormality, the force that presses the diaphragm toward the oil chamber decreases, so the diaphragm does not move sufficiently toward the oil chamber even at the bottom dead center of the plunger. Therefore, excess oil remains in the oil chamber. In this state, if the plunger rises to reach the top dead center, the diaphragm may be excessively displaced toward the pump chamber side and may be damaged.

[0004]

In order to solve the above problems, according to the present invention, there is provided a pump chamber and a hydraulic fluid chamber defined by a diaphragm, and the hydraulic fluid chamber has a plunger inserted therein and actuated. It is connected to a cylinder filled with liquid, and the plunger reciprocates in the cylinder to cyclically change the hydraulic fluid pressure in the hydraulic fluid chamber to supply the liquid pressurized to a substantially constant pressure to the pump chamber. In a diaphragm type liquid pump adapted to discharge from a discharge port of a pump chamber, an overflow passage is provided for overflowing the working fluid from the working fluid chamber, and the overflow passage is opened and closed for opening and closing the overflow passage. A control valve is provided to open the control valve when the pressure of the pressurized liquid supplied to the pump chamber becomes lower than a predetermined pressure to overflow the hydraulic fluid in the hydraulic fluid chamber. It is way.

[0005]

When the pressure of the pressurized liquid supplied into the pump chamber becomes lower than the predetermined pressure, the control valve is opened to overflow the hydraulic fluid in the hydraulic fluid chamber. Therefore, even at the top dead center of the plunger, the diaphragm is not excessively displaced toward the pump chamber side.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 is a diaphragm type fuel pump for supplying fuel to a fuel injection valve 3 which directly injects fuel into a combustion chamber 2 of an engine. The diaphragm fuel pump 1 includes a pump housing 4 and a housing cover 5 fixed to an upper portion of the pump housing 4. A cam chamber 6 is formed in the pump housing 4,
A cam shaft 8 having a cam 7 formed therein is arranged in the cam chamber 6. The camshaft 8 is rotationally driven in synchronization with the crankshaft of the engine.

A closed chamber 9 is formed between the top of the pump housing 4 and the bottom of the housing cover 5. This closed chamber 9
Is divided into a pump chamber 11 and an oil chamber 12 by a diaphragm 10. A cylinder 13 that connects the cam chamber 6 and the oil chamber 12 is formed in the pump housing 4. A plunger 14 is slidably inserted into the cylinder 13, and the lower end of the plunger 14 is constantly engaged with the outer peripheral surface of the cam 7.

Two ports 15 are formed on the inner peripheral side surface of the cylinder 13, and each port 15 is connected to the cam chamber 6 via each oil passage 16. Each port 15 opens into the cylinder 13 when the plunger 14 is at bottom dead center,
The plunger 14 is closed when it slightly rises from the bottom dead center. The oil chamber 12 is connected to the cam chamber 6 via an overflow passage 17, and an overflow control valve 18 for opening and closing the overflow passage 17 is arranged in the middle of the overflow passage 17.

In the cam chamber 6, the oil chamber 12, the cylinder 1
3, the oil passage 16 and the overflow passage 17 are filled with oil, and the hydraulic pressure in the cam chamber 6 is maintained at about atmospheric pressure. The fuel inlet port 1 is located above the fuel chamber 11.
9 is formed. A discharge amount control valve 20 for opening and closing the fuel inflow port 19 is arranged in the fuel inflow port 19. The discharge amount control valve 20 is constantly urged downward by the spring 35, and when the solenoid 36 is turned on, the discharge amount control valve 20 is displaced upward against the spring force of the spring 35, and the fuel inflow port 19 is closed.

The fuel inflow port 19 is connected to the fuel supply pipe 21.
Is connected to the fuel tank 22 via. In the middle of the fuel supply pipe 21, the feed pump 2
3, a filter 24, a pressure regulator 25, and a supply fuel pressure sensor 26 are arranged. The pressure regulator 25 is connected to the fuel tank 22 via a return passage 27. As a result, the diaphragm fuel pump 1 is supplied with the pressurized fuel adjusted to a substantially constant pressure preset by the pressure regulator 25.

The pump chamber 11 is connected to the fuel injection valve 3 via a fuel discharge passage 28. A check valve 29 is arranged in the fuel discharge passage 28, and a discharge fuel pressure sensor 30 is arranged in the fuel discharge passage 28 between the check valve 29 and the fuel injection valve 3. An electronic control unit (ECU) 40 including a digital computer is connected to the supply fuel pressure sensor 26, the discharge fuel sensor 30, and a crank angle sensor 31 that generates an output pulse proportional to the engine speed.

The overflow control valve 18 and the discharge amount control valve 20 are connected to the ECU 40 and controlled by the ECU 40. Next, the operation of the diaphragm fuel pump 1 will be described. The overflow control valve 18 is normally closed.
When the plunger 14 is located at the top dead center, the solenoid 36 is already turned off, but the discharge amount control valve 20 is closed by the fuel pressure in the fuel chamber 11.

When the plunger 14 starts to descend from the top dead center, the oil pressure in the oil chamber 12 decreases, which causes the diaphragm 10 to be displaced downward and the fuel pressure in the pump chamber 11 to decrease. The fuel pressure in the pump chamber 11 is controlled by the discharge amount control valve 2
The valve closing force that urges 0 upward is determined by the pressure regulator 25 and the supply fuel pressure and the spring 35.
When and become smaller than the valve opening force that urges the discharge amount control valve 20 downward, the discharge amount control valve 20 is opened, and the fuel flows into the pump chamber 11 from the fuel inflow port. The diaphragm 10 is displaced downward as the plunger 14 descends while balancing the fuel pressure in the pump chamber 11 and the oil pressure in the oil chamber 12. Port 15 is fully opened just before bottom dead center.

When the plunger 14 starts to rise from the bottom dead center and the port 15 is fully closed, the diaphragm 10 starts to be displaced upward. Since the discharge amount control valve 20 is opened, the fuel in the pump chamber 11 will not flow into the fuel inflow port 19
And flows back to the fuel supply pipe 21 via. Next, when the solenoid 36 is turned on, the discharge amount control valve 20 is closed, so that the fuel in the pump chamber 11 starts to be pressurized. The solenoid 36 is turned on for a short time according to the engine operating state, and is turned off when the plunger 14 is located at the top dead center as described above. The discharge amount control valve 20 is kept closed by the fuel pressure in the pump chamber 11.

When the fuel pressure in the pump chamber 11 rises with the rise of the plunger 14 and becomes higher than the opening pressure of the check valve 29, the check valve 29 opens and fuel is injected into the fuel injection valve 3. Supplied. The fuel supply amount of the fuel pump 1 is controlled by the closing timing of the discharge amount control valve 20.
The valve closing timing of is controlled such that the fuel pressure detected by the discharge fuel pressure sensor 30 becomes the target fuel pressure.

By the way, when the fuel pressure supplied to the pump chamber 11 is not sufficiently increased due to a failure of the feed pump 23 or the pressure regulator 25, for example, the diaphragm 10 is also at the bottom dead center position of the plunger 14. Is not sufficiently displaced downwards, which causes the volume of the oil chamber 12 to increase from the normal level and
Excess oil remains in 2. Therefore, when the plunger 14 rises to reach the top dead center, the diaphragm 10 may be excessively displaced and damaged.

Therefore, in this embodiment, an overflow passage 17 for connecting the oil chamber 12 and the cam chamber 6 is provided.
7, the overflow control valve 18 is arranged so that the overflow control valve 18 is opened when the supply fuel pressure detected by the supply fuel pressure sensor 26 becomes lower than a predetermined lower limit pressure. When the fuel pressure supplied into the pump chamber 11 drops excessively and becomes lower than a predetermined lower limit pressure,
Since the diaphragm 10 may be damaged as described above, the overflow control valve 18 is opened so that the oil in the oil chamber 12 overflows into the cam chamber 6. As a result, it is possible to prevent excessive displacement of the diaphragm and prevent it from being damaged.

When the overflow control valve 18 is opened, the fuel in the pump chamber 11 is not pressurized, and therefore the fuel injection valve 3
The engine shuts down because no fuel is supplied to the engine. FIG. 2 shows a routine for controlling the overflow control valve 18. This routine is executed by interruption at regular time intervals. Referring to FIG. 2, in step 50, the pressurized fuel pressure P supplied into the pump chamber 11 is the lower limit pressure P.
It is determined whether it is lower than _MIN . If P <P _MIN ,
Proceeding to step 51, the overflow control valve 18 is opened. P
If ≧ P _MIN , the overflow control valve 18 is maintained in the current state.

To close the overflow control valve 18 after the overflow control valve 18 is opened, for example, after repairing a defective portion such as the feed pump 23 or the pressure regulator 25, the port 15 is opened in the cylinder 13. The overflow control valve 18 is closed within the period. Overflow control valve 1 except when the port 15 is open in the cylinder 13
If the valve 8 is closed, the amount of oil in the oil chamber 12 becomes too small, and the diaphragm 10 may be excessively displaced downward when the plunger 14 is located at the bottom dead center.
Overflow control valve 18 must be closed during the period that port 15 is open in cylinder 13.

Since the camshaft 8 rotates in synchronization with the crankshaft of the engine, the position of the plunger 14 can be detected by the crank angle sensor 31.

[0021]

The diaphragm can be prevented from being excessively displaced and damaged.

[Brief description of drawings]

FIG. 1 is an overall view of a diaphragm pump.

FIG. 2 is a flowchart for executing control of an overflow control valve.

[Explanation of Codes] 1 ... Diaphragm fuel pump 10 ... Diaphragm 11 ... Pump chamber 12 ... Oil chamber 13 ... Cylinder 14 ... Plunger 17 ... Overflow passage 18 ... Overflow control valve

Claims (1)

[Claims] 1. A pump chamber and a hydraulic fluid chamber defined by a diaphragm, the hydraulic fluid chamber communicating with a cylinder in which a plunger is inserted and filled with the hydraulic fluid, and the plunger moves in the cylinder. A diaphragm type in which the hydraulic fluid pressure in the hydraulic fluid chamber is cyclically changed by reciprocating motion, and the liquid pressurized to a substantially constant pressure supplied to the pump chamber is discharged from the discharge port of the pump chamber. In the liquid pump, an overflow passage for overflowing the working fluid from the working fluid chamber is provided, and a control valve for opening / closing the overflow passage is provided in the overflow passage, and a supply valve is provided to the pump chamber. A diaphragm pump in which the control valve is opened to overflow the hydraulic fluid in the hydraulic fluid chamber when the pressure of the pressurized liquid becomes lower than a predetermined pressure.