JP2002021684A - Variable discharge flow rate plunger pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger pump or a variable high pressure plunger pump discharge flow rate provided with a small back pressure chamber having a cup-form small back pressure chamber body to close the end part of the slide hole of a suction check valve element, and having a small back pressure chamber the port of which is caused to selectively communicate with a feed fuel passage through opening and closing of the rod of a small electromagnetic switching valve, and capable of eliminating operation of the small electromagnetic switching valve at a suction process. SOLUTION: The plunger pump is provided in the suction check valve element 30 with the small back pressure chamber 33, a communication passage 36 capable of communicating with a suction port 12, and in the communication passage 36 with a check valve 37 to block a flow of fluid from the interior of the small back pressure chamber 33 to the suction port 12. When the suck check valve element 30 is closed, the check vale 37 is also operated to close the communication passage 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and structure of a small back pressure chamber of a pre-stroke type variable discharge flow rate plunger pump suitable for controlling a high-pressure fluid, such as a fuel injection device for supplying fuel to a diesel engine or a gasoline engine. About.

[0002]

2. Description of the Related Art As such a fuel injection device, a high-pressure fuel pump used in a system in which high-pressure fuel is accumulated in a pressure accumulator or a pressure accumulation pipe called a common rail and this high-pressure fuel is injected into an engine through an electromagnetic injector. These are disclosed in JP-A-9-112731 and JP-A-6-2575333.

[0003] PCT Application No. PCT / JP00 / 01746, which has been filed by the applicant of the present invention and has not been disclosed, discloses a variable discharge flow rate plunger pump constituted by using a normally closed solenoid valve as shown in FIG. It has been disclosed. The pump has springs 9 formed in pump housing 250, respectively.
Pump plunger 3 reciprocatingly urged by force, pump chamber 2 pressurized by pump plunger 3, pump chamber 2
Check valve 256 and discharge port of pump chamber 2 which are arranged at suction port 26 of
A discharge check valve connected to 27 and a plunger pump pumped by
256 sliding holes 208 Cup-shaped small back pressure chamber body 60 closing the end
The small back pressure chamber 62 having a small back pressure chamber 62 is provided, and the port 61 of the small back pressure chamber 62 is selectively communicated with the feed fuel passage 4 by opening and closing the rod 712 of the small electromagnetic switching valve 7. When operated, the rod 71 of the switching valve 7 is
By closing the port 61 of 62, the suction check valve
256 is controlled so that it can maintain the valve open position even if it receives the force of the suction check spring 255 and the pressure of the pump chamber 2,
This is a variable discharge flow rate plunger pump with a variable pump discharge amount.

FIG. 6 is a control time chart showing an operation timing concept of the variable discharge flow rate plunger pump when the normally closed type electromagnetic switching valve shown in FIG. 5 is used. The control of the electromagnetic switching valve 7 is performed in synchronization with the rotation speed of the pump, that is, the vertical stroke cycle of the pump plunger 3, and the flow control is performed by closing the port 61 hole of the small back pressure chamber 62 by turning on and off the electromagnetic switching valve 7. This realizes the closing and opening of the suction check valve body 256 for sealing the pressure and opening the port 61 hole. It is necessary to control ON / OFF of the electromagnetic switching valve in both the suction process and the compression process for the small back pressure chamber 62. As shown in FIG. 6, in the pump control of FIG. 5, the oil suction also passed through the port 61 hole of the small back pressure chamber 62, so that the ON / OFF control of the electromagnetic switching valve 7 was necessary not only in the compression process but also in the suction process. there were. First, in the suction process starting from the top dead center of the pump plunger 3, the suction check valve body 256 is opened (down) due to the lowering of the pump plunger 3. At this time,
The small back pressure chamber 62 is in a somewhat low pressure state. At this time, the electromagnetic switching valve 7
6, the rod 71 of the solenoid-operated switching valve 7 opens the port 61 of the small back pressure chamber 62, the small back pressure chamber 62 is opened, and oil flows in from the port 61 hole of the small back pressure chamber 62 (the suction in FIG. 6). (Equivalent to 25% of section). Then, near the bottom dead center position of the pump plunger 3, when the energization of the electromagnetic switching valve 7 is released, the rod 71 of the electromagnetic switching valve 7 closes the port 61 of the small back pressure chamber 62 and the port of the small back pressure chamber 62. 61 is sealed. In this state, the suction check valve body 256 can be kept open by the pressure sealing oil pressure of the small back pressure chamber 62, and the pump chamber 2 is filled with fuel oil. If the compression process is started as it is, the fuel oil once flowing into the pump chamber 2 starts to be discharged into the feed fuel passage 4 through the suction check valve body 256 (corresponding to the discharge section in FIG. 6).
Thereafter, for the purpose of flow control, if the electromagnetic switching valve 7 is energized at any time in the compression process, the rod 71 of the electromagnetic switching valve 7 opens the port 61 of the small back pressure chamber 62, and the small back pressure chamber 62 is opened. As a result, the oil pressure is lost and the suction check valve body 256 is closed (corresponding to the control duty 65% section in FIG. 6). From the moment the suction check valve 256 closes, the fuel oil remaining in the pump chamber 2 is pressurized by the rising force of the pump plunger 3, and when it exceeds the common rail pressure (not shown), the internal oil is discharged. Discharged through check valve 130. That is, the discharge amount can be controlled at the timing when the electromagnetic switching valve 7 is operated in the compression step. This is the so-called pre-stroke method.

[0005]

In the pre-stroke system in which the small back pressure chamber is controlled, an appropriate small back pressure chamber space is taken into consideration in consideration of the amount of fuel oil discharged and the pressure holding time of the small back pressure chamber at a low rotational speed. is necessary. In order to minimize the internal pressure of the small back pressure chamber with as little labor as possible while maintaining the opening of the suction check valve body, the port diameter of the small back pressure chamber in which the switching valve rod closes must be as small as possible. is there. However, if the port diameter of the small back pressure chamber is reduced, the small port diameter may obstruct the fluid in a high rotation speed range, and a sufficient amount of oil may not be sucked into the small back pressure chamber. In order to maintain the opening of the suction check valve body during the compression process of the pump plunger, it is necessary to self-prime the oil from the through hole opened in the suction check valve body, and then close the small hole to seal the small back pressure chamber. there were.

An object of the present invention is to provide a pump plunger, which is formed in a pump housing and reciprocates by being biased by a spring force, a pump chamber pressurized by the pump plunger, and a suction port of the pump chamber. In a plunger pump that is pumped by a suction check valve body connected to a feed fuel passage and a discharge check valve connected to a discharge port of a pump chamber, a cup shape closing an end of a sliding hole of the suction check valve body. A small back pressure chamber having a small back pressure chamber main body is provided, and a port of the small back pressure chamber is selectively communicated with the feed fuel passage by opening and closing a rod of a small electromagnetic switching valve, and in the suction process, An object of the present invention is to provide a variable discharge flow high-pressure plunger pump that can omit switching valve operation.

[0007]

According to the present invention, a pump plunger formed in a pump housing and reciprocating by a spring force, a pump chamber pressurized by the pump plunger, and suction of the pump chamber are provided. A plunger pump that is pumped by a suction check valve body disposed in the port and communicating with the feed fuel passage and a discharge check valve connected to the discharge port of the pump chamber. A small back pressure chamber having a cup-shaped small back pressure chamber body whose end is closed is provided, and a port of the small back pressure chamber is selectively communicated with the feed fuel passage by opening and closing a rod of a small cutoff solenoid valve. West,
When the suction check valve body operates, the switching valve rod closes the port of the small back pressure chamber, so that the suction check valve body opens even if it receives the suction check valve spring force and the pressure of the pump chamber. The position is maintained so that the pump discharge amount is variable, and a communication path that can communicate with the small back pressure chamber and the suction port in the suction check valve body, and a communication path from the small back pressure chamber to the communication path. A discharge valve, wherein a check valve for closing the flow of fluid to the suction port is provided, and the check valve also closes the communication passage when the suction check valve body is closed. The above problem has been solved by providing a pump.

FIG. 2 is a control time chart of the discharge flow rate variable plunger pump of the present invention when a normally closed type electromagnetic switching valve is used. According to the above configuration, as shown in FIG. 2, in the suction process, the electromagnetic switching valve is turned off and the rod of the electromagnetic switching valve closes the port of the small back pressure chamber, but the pump chamber becomes negative pressure. Under the influence, the suction check valve body is pushed down and the small back pressure chamber also has a negative pressure, so that the oil flows from the feed fuel passage 4 into the small back pressure chamber through the communication passage in the suction check valve body and the check valve. Conversely, in the compression process, the OFF state of the electromagnetic switching valve is maintained during the suction process and the port of the small back pressure chamber is closed, but the pressure in the pump chamber rises and the suction check valve body moves upward in FIG. Trying to be pushed up. However, since the port of the small back pressure chamber is closed, the pressure in the small back pressure chamber increases, the check valve is closed, and the small back pressure chamber is closed. As a result, the pressure in the small back pressure chamber is maintained, and the suction check valve body is kept open. If the solenoid switching valve is energized at any time during the compression process according to the required flow rate, the rod of the solenoid switching valve opens the port of the small back pressure chamber, the small back pressure chamber is opened, the hydraulic pressure is lost, and the suction check valve body Is closed and the suction check valve body is closed, the check valve also closes the communication path and the communication path is shut off.From the moment the suction check valve body is closed, the fuel oil remaining in the pump chamber is removed from the pump plan. It is pressurized by the rising force of the jar and discharged from the discharge check valve to the outside. Thus, the operation of the electromagnetic switching valve can be omitted in the suction process by sucking oil from the communication passage provided in the suction check valve body constituting the small back pressure chamber.

Preferably, since many of the target variable discharge flow plunger pumps have a two-cylinder structure in which the suction and compression processes are 180 ° out of phase, each of the two small discharge pressure plunger pumps has a small back pressure. The ports of the chambers are substituted for the spring chambers of the two check valves, and each of the two spring chambers is opened and closed by a check valve element pressed by the springs of the two check valves, respectively. Each spring chamber of the check valve is connected to two output ports of one 3-position all-port block solenoid-operated switching valve, and the pump port and the tank port of the 3-position all-port block solenoid-operated switching valve are: By connecting to the feed fuel passage and the drain port respectively, the compression process of the two cylinders is repeated in opposite phases, so that both small back pressure chambers communicate with each other. By performing control of a single electromagnetic selector valve other electromagnetic selector valve may be removed.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially enlarged cross-sectional view showing a normally closed electromagnetic switching valve 7, a small back pressure chamber 33, and a suction check valve body 30 according to a first embodiment of the present invention. These parts are used in the discharge flow rate variable plunger pump shown in FIG. 5, and only the members different from FIG. 5 are shown in FIG. 1 and the description of the members described in FIG. 5 is omitted. The variable discharge flow rate plunger pump according to the first embodiment of the present invention has a pump plunger 3 which is formed in a pump housing 250 and reciprocates by being urged by a spring 9 as shown in FIG. A pump chamber 2 pressurized by a pump plunger 3, a suction check valve disposed at a suction port of the pump chamber 2 and connected to a feed fuel passage 4, and a discharge check valve connected to a discharge port 27 of the pump chamber 2.
130, used by plunger pump to work by pumping.

In FIG. 1, a small back pressure chamber 33 having a cup-shaped small back pressure chamber body 32 for closing an end of a sliding hole 31 of a suction check valve body 30 is provided. Solenoid switching valve
7 to selectively communicate with the feed fuel passage 4 by opening and closing the rod 71, and when the suction check valve body 30 is operated, the rod 71 of the electromagnetic switching valve 7 is connected to the port 34 of the small back pressure chamber 33.
By closing the valve, the suction check valve 30 is controlled so that it can maintain the valve open position even if it receives the force of the suction check spring 35 and the pressure of the pump chamber 2, and the discharge flow rate of the pump is made variable. A plunger pump is formed. In the present invention, the communication path 36 that can communicate with the small back pressure chamber 33 and the suction port 12 in the suction check valve body 30 and the flow of the fluid from the small back pressure chamber 33 to the suction port 12 in the communication path 36 are closed. When the suction check valve body 30 is closed, the check valve 37 also closes the communication passage 36.

In the present invention, since the oil is sucked into the small back pressure chamber 33 without the rod 71 of the electromagnetic switching valve 7 opening and closing the port 34 of the small back pressure chamber 33, the above-described problem occurs. Can be eliminated. The check valve 37 has a seat structure in which a ball 39 is received on an upper end surface of the suction check valve body 30 by a check valve spring 38. In this structure, the control timing chart of the control timing chart of FIG. 2 shows the concept of the operation timing of the discharge flow variable plunger pump using the normally closed solenoid switching valve, the small back pressure chamber and the suction check valve body of FIG. As a result, the valve opening control command of the electromagnetic switching valve in the suction section as shown in FIG. 6 becomes unnecessary.

Referring to the control time chart of FIG. 2, in the suction process, the electromagnetic switching valve 7 is turned off and the rod 71 of the electromagnetic switching valve 7 closes the port 34 of the small back pressure chamber 33.
2, the suction check valve body 30 is pushed down under the influence of this, and the small back pressure chamber 33 also becomes a negative pressure, so that the communication passage 36 in the suction check valve body 30 from the feed fuel passage 4 and the check valve Oil flows into the small back pressure chamber 33 through the valve 37. Conversely, in the compression step, the OFF state of the electromagnetic switching valve is maintained during the suction step, and the port 34 of the small back pressure chamber 33 is closed.
2, the suction check valve body 30 is about to be pushed upward as seen in FIG. But port of small back pressure chamber 33
Since the valve 34 is closed, the pressure in the small back pressure chamber 33 increases, the check valve 37 is closed, and the small back pressure chamber 33 is closed. Thus, the pressure in the small back pressure chamber 33 is maintained, and the suction check valve body 30 is kept open. If the solenoid valve 7 is energized at any time during the compression process according to the required flow rate, the solenoid valve 7
Of the small back pressure chamber 33 opens the port 34 of the small back pressure chamber 33.
Is released and loses hydraulic pressure, the suction check valve body 30 is closed, and when the suction check valve body 30 is closed, the check valve 37 also communicates with the
The fuel oil remaining in the pump chamber 2 is pressurized by the rising force of the pump plunger 3 from the moment the suction check valve body 30 is closed and the internal pressure is increased when the pressure exceeds a common rail pressure (not shown). Oil discharge check valve shown in FIG.
Is discharged through. That is, the discharge amount can be controlled at the timing when the electromagnetic switching valve 7 is operated in the compression step. As a result, the pressure in the small back pressure chamber 33 can be maintained in the compression step.

FIG. 3 shows a second embodiment of the present invention.
A mechanism for controlling the flow rates of the two cylinders of the two discharge flow rate variable plunger pumps with a single electromagnetic switching valve will be described. Instead of the ON-OFF electromagnetic switching valve located above the back pressure chamber of each cylinder in FIG. 1, the ports of each small back pressure chamber of the two discharge flow variable plunger pumps have two check valves 37, 37. 'Spring Chamber
Each of the two spring chambers 40, 40 'is replaced with a check valve body 45, 4 which is pushed by two check valve springs 44, 44'.
Each of the spring chambers 40, 40 'of the two check valves is opened and closed by 5', and two output ports A, B of one 3-position all-port block electromagnetic switching valve 42 are connected by pipes 46, 46 '. The pump port P and the tank port T of the three-position all-port block electromagnetic switching valve are connected to the feed fuel passage 4 and the drain port 43, respectively.

As shown in the control time chart of FIG.
For each cylinder valve opening control command, the control mode is classified as follows based on the timing. First, the first cylinder spring chamber
When the spring 40 is opened and the spring chamber 40 'of the second cylinder is closed (control mode (3)), the right coil of the electromagnetic switching valve 42 is turned on. As a result, the output port A of the electromagnetic switching valve 42 communicates with the tank port T, and the output port A communicates with the pump port P. Conversely, when the spring chamber 40 of the first cylinder is closed and the spring chamber 40 'of the second cylinder is opened ((2) in the control mode), the coil on the left side of the electromagnetic switching valve 42 is disconnected. Turn ON. Then, the output port A communicates with the pump port P, and the output port B communicates with the tank port T. Also, when the solenoid valve is not energized at all,
The spool position of the electromagnetic switching valve is in the neutral state, and the spring chambers 40 and 40 'of both cylinders are closed ((1) of the control mode classification).
In other words, if such a spring chamber 40, 40 'configuration is adopted,
Only 3 position all port block solenoid switching valve 42
A variable discharge flow plunger pump flow control of the cylinder is now possible.

[0016]

The PCT filed by the applicant of the present invention and unpublished
Application PCT / JP00 / 01746 discloses that a check valve is provided inside a suction check valve for a variable discharge flow rate plunger pump that is configured using a normally closed electromagnetic switching valve. If the oil is sucked into the air, the operation of the electromagnetic switching valve in the suction process becomes unnecessary. Therefore, the number of actuations of the electromagnetic switching valve is halved, so that the port of the small back pressure chamber and the rod that closes the port have a long service life. Preferably, the structure is developed by removing the ON-OFF type electromagnetic switching valve provided in the small back pressure chamber of the two cylinders, and the port of each small back pressure chamber is substituted for the spring chamber of the two check valves. Each of the two spring chambers is opened and closed by a check valve body pushed by a spring of the two check valves, and each spring chamber of the two check valves is connected to one closed center electromagnetic valve by piping. By connecting to a switching valve and performing collective control, the number of electromagnetic switching valves can be reduced from two to one.

[Brief description of the drawings]

FIG. 1 shows a normally closed solenoid switching valve of a discharge flow rate variable plunger pump according to a first embodiment of the present invention;
FIG. 4 is a partially enlarged cross-sectional view in which a small back pressure chamber and a suction check valve body are enlarged.

FIG. 2 is a control time chart showing an operation timing concept of the discharge flow rate variable plunger pump using the normally closed electromagnetic switching valve, the small back pressure chamber, and the suction check valve of FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention, in which the flow rate of two cylinders of two discharge flow rate variable plunger pumps is controlled by a single closed center electromagnetic switching valve.

FIG. 4 is a control time chart showing the timing of each cylinder opening control command of the closed center electromagnetic switching valve of FIG. 3;

FIG. 5 PCT application PC which has been filed by the applicant of the present invention and has not been published yet.
FIG. 1 is a schematic cross-sectional view of a variable discharge flow rate plunger pump configured using a normally closed electromagnetic switching valve disclosed in T / JP00 / 01746.

6 is a control time chart showing an operation timing concept of a discharge flow rate variable plunger pump using the normally closed electromagnetic switching valve of FIG.

[Explanation of symbols]

2 ・ ・ ・ Pump chamber 3 ・ ・ ・ Pump plunger 4 ・ ・ ・ Feed fuel passage 7 ・ ・ ・ Solenoid switching valve 12 ・ ・ ・ Suction port 27 ・ ・ ・ Discharge port 30 ・ ・ ・ Suction check valve 31 ・ ・・ Sliding hole of suction check valve 32 ・ ・ ・ Cup-shaped small back pressure chamber 33 ・ ・ ・ Small back pressure chamber 34 ・ ・ ・ Small back pressure chamber port 35 ・ ・ ・ Suction check valve spring 36 ・ ・ ・Communication passage 37, 37 '... Check valve 40, 40' ... Check valve spring chamber 42 ... Closed center solenoid switching valve 45, 45 '... Check valve valve body 71 ... Rod of small electromagnetic switching valve 130 ・ ・ ・ Discharge check valve 250 ・ ・ ・ Pump housing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 59/46 F02M 59/46 Y

Claims (2)

[Claims] A pump plunger formed in a pump housing and reciprocated by a spring force, a pump chamber pressurized by the pump plunger, and a suction port of the pump chamber are communicated with a feed fuel passage. And a discharge check valve connected to a discharge port of the pump chamber, the cup-shaped small back pressure closing an end of a slide hole of the suction check valve. A small back pressure chamber having a chamber body is provided, and a port of the small back pressure chamber is selectively communicated with the feed fuel passage by opening and closing a rod of a small disconnection solenoid valve, and the suction check valve body is operated. When the rod of the switching valve closes the port of the small back pressure chamber at the time of A communication passage that can control the valve opening position even when receiving the pressure, makes the pump discharge amount variable, and can communicate with the small back pressure chamber and the suction port in the suction check valve body; A check valve for closing the flow of fluid from the small back pressure chamber to the suction port, and the check valve also closes the communication passage when the suction check valve body is closed. Characteristic variable discharge flow plunger pump. 2. The port of each of the small back pressure chambers of the two variable discharge flow rate plunger pumps is substituted for two spring chambers of the check valve, and each of the two spring chambers is provided with two of the two spring chambers. Each of the two check chambers is opened and closed by a check valve body pressed by a check valve spring.
Pump ports and tank ports of the three-position all-port block solenoid-operated switching valve are respectively connected to the feed fuel passage and the drain port. 2. The variable discharge flow rate plunger pump according to claim 1, wherein