JPH0617757A - Diaphragm pump - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the diaphragm from being excessively displaced and damaged. [Composition] When the blanker 14 descends, the hydraulic pressure in the hydraulic fluid chamber 12 decreases and the diaphragm 10 is displaced downward.
Therefore, the fuel pressure in the pump chamber 11 decreases, the discharge amount control valve 20 opens, and the fuel pressurized by the feed pump 23 flows into the pump chamber 11. Next, when the plunger 14 rises, the hydraulic pressure in the hydraulic fluid chamber 12 rises, the diaphragm 10 is displaced upward, and the discharge amount control valve 20
When the valve is closed, the fuel pressure in the pump chamber 11 rises, the check valve 29 is opened, and the fuel is discharged. When the engine water temperature is lower than a predetermined value, the heating means provided in the stopper is energized to heat the working fluid.

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, and more particularly, to a diaphragm type pump which drives a diaphragm by displacing the diaphragm by a reciprocating motion of the plunger.

[0002]

2. Description of the Related Art A pump chamber and a hydraulic fluid chamber defined by a diaphragm are provided, and a plunger is inserted into a cylinder communicating with the hydraulic fluid chamber and the plunger reciprocates to change the pressure of the hydraulic fluid chamber. On the other hand, a diaphragm pump in which the diaphragm pulsates and the liquid supplied into the pump chamber is discharged from the pump chamber to perform a pumping action has been filed. (Actual application No. 4-122235)

In this diaphragm type pump, the diaphragm is set to a predetermined lower position when the plunger is located at the bottom dead center, and the diaphragm is also set to a predetermined upper position when the plunger is located at the top dead center. A stopper having a communication hole is provided to limit the maximum displacement of the diaphragm.

[0004]

In such a diaphragm type pump, when the viscosity of the hydraulic fluid increases at low temperature, the hydraulic fluid between the diaphragm and the protective plate is transferred to the cylinder through the communication hole of the protective plate when the plunger descends. Even if the return is delayed and the plunger is located at the bottom dead center, the diaphragm does not return to the predetermined position and the cylinder and the hydraulic fluid reservoir communicate with each other, so that the hydraulic fluid is replenished from the hydraulic fluid reservoir into the cylinder. It will be. After that, if the plunger rises without returning the diaphragm to the specified position, the diaphragm will try to displace more than the position of the stopper that limits it within the specified range, and the diaphragm may be subjected to concentrated stress in the communication hole of the stopper. Occurs. An object of the present invention is to improve the return of the hydraulic fluid from the hydraulic fluid chamber to the inside of the cylinder even at a low temperature and prevent the diaphragm from being damaged.

[0005]

In order to solve the above problems, according to the present invention, there is provided a stopper that includes a pump chamber and a hydraulic fluid chamber defined by a diaphragm, and that limits the displacement of the diaphragm within a predetermined range. In the diaphragm type pump, which is provided, the diaphragm pulsates based on the pressure change in the hydraulic fluid chamber due to the reciprocating movement of the plunger, and the liquid supplied into the pump chamber is discharged from the pump chamber. A heating means for heating the working fluid between the two is provided.

[0006]

By operating the heating means for heating the working fluid between the stopper and the diaphragm at low temperature, the temperature of the working fluid is raised and the viscosity is lowered. For this reason, the return of the hydraulic fluid from the hydraulic fluid chamber to the inside of the cylinder improves as the plunger descends, and the diaphragm also comes to a predetermined position when the plunger is located at the bottom dead center, so that when the plunger is located at the top dead center. However, the diaphragm does not move beyond the predetermined position.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 denotes a combustion chamber 2 of an engine.
It is a diaphragm type fuel injection pump for supplying fuel to a fuel injection valve 3 that directly injects fuel into the inside. 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 hydraulic fluid storage chamber 6 is formed in the pump housing 4, and a cam shaft 8 having a cam 7 is disposed in the hydraulic fluid storage chamber 6. The camshaft 8 is rotationally driven in synchronization with the crankshaft of the engine.

A diaphragm 10 defines a pump chamber 11 and a hydraulic fluid chamber 12 between the top of the pump housing 4 and the bottom of the housing cover 5. The bottom of the housing cover 5 and the top of the pump housing 4, which form the pump chamber 11 and the hydraulic fluid chamber 12, respectively form stoppers 17 and 18 for limiting the displacement of the diaphragm within a predetermined range. A heating means (heater) 30 is provided on the top of the pump housing 4, which serves as the stopper 18 on the hydraulic fluid chamber side, to generate heat when energized when the engine water temperature is low. A cylinder 13 that communicates with the hydraulic fluid chamber 12 is formed in the pump housing 4, and a plunger 14 is slidably inserted into the cylinder 13, and the lower end of the plunger 14 is in contact with the outer peripheral surface of the cam 7.

A port 15 is formed on the inner peripheral side surface of the cylinder 13, and the port 15 is communicated with the hydraulic fluid reservoir chamber 6 via a hydraulic fluid passage 16. The port 15 opens into the cylinder 13 when the plunger 14 is at bottom dead center, and closes when the plunger 14 rises slightly from bottom dead center. The hydraulic fluid storage chamber 6, the hydraulic fluid chamber 12, the cylinder 13, and the hydraulic fluid passage 16 are filled with oil, and the hydraulic pressure in the hydraulic fluid storage chamber 6 is maintained at substantially atmospheric pressure.

A fuel inflow port 19 is provided above the pump chamber 11.
Is formed. A discharge amount control valve 20 that opens and closes 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 is opened. The valve 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, and a pressure regulator 25 are arranged. The pressure regulator 25 has a return passage 2
It is connected to the fuel tank 22 via 7. 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, and a check valve 29 is arranged in the fuel discharge passage.

Next, the operation of the diaphragm pump 1 will be described. When the plunger is located at the bottom dead center, the inside of the cylinder 13 and the hydraulic fluid storage chamber 6 are
It communicates through the port 15. When the plunger 14 starts to rise from the bottom dead center and the port is fully closed, the diaphragm starts to be displaced upward from the lower end position in contact with the stopper 18. Since the discharge flow control valve 20 is opened, the fuel in the hydraulic fluid chamber 11 flows back to the fuel supply pipe 21 via the fuel inflow port 19. Next, when the solenoid 36 is turned on, the discharge flow rate control valve 20 is closed, so that the fuel in the hydraulic fluid chamber 11 starts to be pressurized. The solenoid 36 is turned on only for a time corresponding to the engine operating state,
It is turned off when the plunger 14 is located at the top dead center.

As the plunger 14 rises, the pump chamber 1
When the fuel pressure in 1 rises and becomes higher than the valve opening pressure of the check valve 29, the check dead valve 29 opens and fuel is supplied to the fuel injection valve 3. The fuel supply amount of the fuel pump 1 is controlled by the closing timing of the discharge flow rate control valve 20.
The zero valve closing timing is controlled so that the fuel pressure becomes the target pressure.

When the plunger 14 starts to descend from the top dead center, the hydraulic pressure in the hydraulic fluid chamber 12 decreases, whereby the diaphragm 10 is displaced downward and the fuel pressure in the pump chamber 11 also decreases. The valve closing force generated by the fuel pressure in the pump chamber 11 urging the discharge flow rate control valve 20 upward causes the supply fuel pressure adjusted by the pressure regulator 25 and the spring 35 to operate the discharge flow rate control valve 20. When it becomes smaller than the valve opening force generated by urging downward, the discharge flow rate control valve 20 is opened, and the fuel flows into the pump chamber 11 from the fuel inflow port. While balancing the fuel pressure in the pump chamber 11 and the hydraulic pressure in the hydraulic fluid chamber 12,
As the plunger 14 descends, the diaphragm 10 is displaced downward.

Therefore, for example, when the engine water temperature is detected and the engine water temperature is low, the heating means (heater) provided in the hydraulic fluid chamber is heated to raise the temperature of the hydraulic fluid between the diaphragm and the pump housing. The viscosity of the liquid is reduced. This improves the return of the hydraulic fluid from the hydraulic fluid chamber through the cylinder, and prevents the excess hydraulic fluid from remaining in the hydraulic fluid chamber when the plunger is located at the bottom dead center, and the diaphragm has a predetermined size. Can return to position. Therefore, even when the plunger is located at the top dead center, it is possible to prevent abnormal displacement of the diaphragm and abnormal stress.

FIG. 2 shows a routine for controlling the heating means. This routine is executed by interruption at regular intervals. Referring to FIG. 2, in step 50, it is determined whether the engine water temperature THW is lower than the predetermined temperature TMIN. If THW <TMIN, step 51
Then, the heating means is energized and heated. THW ≧ TMI
If it is N, energization of the heating means is prohibited.

Although the heating is performed by detecting the engine water temperature, the temperature of the hydraulic fluid may be directly detected instead of the engine water temperature.

[0018]

As described above, according to the present invention, the fluidity of the working fluid is improved even in the cold state, so that it is possible to prevent the diaphragm from being excessively displaced and damaged.

[Brief description of drawings]

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

FIG. 2 is a side sectional view of a part of a diaphragm pump.

FIG. 3 is a flowchart for executing control of heating means.

[Explanation of symbols]

 1- ・ Diaphragm fuel pump 10 --- Diaphragm 11-Pump chamber 12-Hydraulic fluid chamber 14-Plunger 17,18-Stopper 30- .... Heating means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Masubuchi, Toyota Town, Toyota City, Aichi Prefecture, Toyota 1 (72) Inventor, Akihiro Yamanaka 1, Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation

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 hydraulic fluid, and the plunger reciprocates in the cylinder. The movement causes the diaphragm to be displaced to discharge the liquid supplied to the pump chamber from the pump chamber, and a stopper for limiting the displacement of the diaphragm within a predetermined range is provided at least on the hydraulic fluid chamber side, and the reciprocating motion of the plunger A diaphragm pump that replenishes the working fluid by providing a working fluid reservoir that communicates with the inside of the cylinder is provided with heating means for heating the working fluid between the stopper and the diaphragm at low temperature. Diaphragm pump.