JP2006118380A - Liquid pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid pump with a lifter easily rotatable. <P>SOLUTION: A high pressure fuel pump 1 as the liquid pump comprises a main body 502 having an internal space 520 for storing fuel 150, a plunger 503 fitted in the internal space 520 and reciprocating to pressure-feed the fuel 150 in the internal space 520, the lifter 504 having a central region 544 contacting with the plunger 503 and an outer peripheral region 545 remote from the plunger 503 and reciprocating the plunger 503 in contact with an inner surface 541 with an outer surface 542 pushed by a pump cam 4, a plate 505 contacting with the inner surface 541 of the lifter 504 at the central region 544 of the lifter 504 and separated from the inner surface 541 of the lifter 504 at the outer peripheral region 541 of the lifter 504, and a spring 506 interposed between the main body 502 and the plate 505 to bias the plate 505 in a direction going away from the main body 502. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid pump, and more particularly to a high-pressure pump for pumping fuel for automobiles.

Conventional liquid pumps are disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-31017 (Patent Document 1) and Japanese Society of Invention and Innovation Publication No. 2003-502916 (Non-Patent Document 1).
JP 2002-31017 A Japan Society for Invention and Innovation Open Technical Bulletin No. 2003-502916

  Patent Document 1 discloses a problem that a lifter must be rotated to prevent uneven wear of the lifter.

  Non-Patent Document 1 discloses a technique in which an axial clearance is provided between the plunger neck and the plate in order to prevent uneven wear of the plunger, and the plunger is rotated by a torsional force of a coil spring.

  Since the conventional high pressure pump has a structure in which the lifter is difficult to rotate, an expensive material or an expensive surface treatment is required to ensure wear resistance. As a cause of this, the plunger type high-pressure gasoline pump is conventionally driven by a cam, and two or three mountain cams are used so as to be driven a plurality of times by one rotation of the cam in order to secure a discharge amount. For this reason, in the conventional valve operating system, the contact is released at the base edge, whereby the lifter rotates due to inertia. The high pressure pump has to be designed to contact even at the base edge, and there is a problem that the lifter is difficult to rotate as compared with the valve operating system.

  Furthermore, in order to ensure the clearance between the neck of the plunger and the plate, the bottom surface of the lifter and the plate spring receiving portion have a contact structure, which makes rotation difficult.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a liquid pump in which a lifter can rotate.

  A liquid pump according to the present invention includes a main body having an internal space for storing liquid, a plunger that fits into the internal space and reciprocates to pump the liquid in the internal space, and a central region that contacts the plunger. A lifter that has an outer peripheral region that is separated from the plunger, and the outer surface is pressed by a pressing member so that the plunger that contacts the inner surface can be reciprocated; and in contact with the inner surface of the lifter in the central region of the lifter, An intermediate member spaced from the inner surface of the lifter in an outer peripheral region of the lifter, and an urging member interposed between the main body and the intermediate member to urge the intermediate member in a direction away from the main body.

  In the liquid pump configured as described above, the intermediate member is in contact with the inner surface of the lifter in the central region of the lifter and is separated from the inner surface of the lifter in the outer peripheral region of the lifter, so that no load is applied to the outer peripheral region of the lifter. It becomes easy to rotate the lifter relative to the intermediate member and the plunger. As a result, it is possible to provide a liquid pump having a structure in which the lifter easily rotates.

  More preferably, the inner surface of the central region of the lifter is convex and contacts the plunger and the intermediate member. In this case, the inner surface of the central region of the lifter has a convex shape, and contact between the convex portion and the plunger can be ensured.

  More preferably, the lifter can rotate about the plunger as a rotation axis, and when the pressing member contacts and rotates on the outer surface of the lifter, the lifter also rotates.

  According to the present invention, it is possible to provide a liquid pump that facilitates rotation of the lifter and prevents wear of the lifter.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a cross-sectional view of an engine having a high-pressure fuel pump according to the present invention. Referring to FIG. 1, in the fuel pump drive structure according to the present invention, high pressure fuel pump 1 as a fuel pump (liquid pump) is attached to head cover 2. The head cover 2 is fixed to the cylinder head 3 and serves to cover a member such as a cam provided on the cylinder head 3. In the cylinder head 3, engine valves 61 and 62 are provided in the vicinity of the combustion chamber. The engine valve 61 is an intake valve, and the engine valve 62 is an exhaust valve. The engine valves 61 and 62 are pushed up by the valve spring 11, and this pushing force is transmitted to the hydro lash adjuster 10 through the valve rocker arm 9. The pushing force is transmitted to the valve cams 121 and 122. Valve cams 121 and 122 are attached to camshafts 57 and 58, respectively, and rotate together with camshafts 57 and 58. The valve cams 121 and 122 are in contact with the roller 14, respectively, and the roller 14 rotates in a direction opposite to the rotation direction of the valve cams 121 and 122 when the valve cams 121 and 122 rotate. This reduces friction. When the crest portions of the valve cams 121 and 122 come into contact with the roller 14, the roller 14 operates to push down the engine valves 61 and 62 via the valve rocker arm 9.

  Next, the function of the high pressure fuel pump 1 will be described. The high-pressure fuel pump 1 according to the present invention is used in a direct injection system, and the fuel sent from the fuel pump in the fuel tank is sent to the high-pressure fuel pump 1 attached to the head cover 2 and depends on the operating state. The fuel is pressurized by the high-pressure fuel pump 1 and sent to the high-pressure fuel injector. The fuel sent to the fuel injector is injected into the cylinder (combustion chamber) and then ignited to explode.

  The pressure of the fuel is increased by pressing the lifter 504 of the high-pressure fuel pump 1. A mechanism for boosting the lifter 504 is a pump cam 4. The pump cam 4 is attached to the cam shaft 58 on the exhaust side. The pump cam 4 rotates together with the camshaft 58 and the valve cam 122. Although the pump cam 4 is provided with three peaks, the number of the peaks of the pump cam 4 is not limited to this, and three or more or three or less peaks may be provided. .

  When the pump cam 4 rotates and the peak portion of the pump cam 4 approaches the lifter 504, the lifter 504 is pushed up. The fuel is boosted by this pushing force.

  FIG. 2 is a cross-sectional view of the high-pressure fuel pump shown in FIG. Referring to FIG. 2, the high-pressure fuel pump 1 fits into the internal space 520 having an internal space 520 that stores the fuel 150 as a liquid, and reciprocates to pump the fuel 150 in the internal space 520. A plunger 503, a central region 544 in contact with the plunger 503, and an outer peripheral region 545 spaced from the plunger 503, and the outer surface 542 is pressed by the pump cam 4 as a pressing member to contact the inner surface 541. A lifter 504 capable of reciprocating the plunger 503, and a plate as an intermediate member that contacts the inner surface 541 of the lifter 504 in the central region 544 of the lifter 504 and separates from the inner surface 541 of the lifter 504 in the outer peripheral region 545 of the lifter 504 505, and between the main body 502 and the plate 505 The door 505 and a spring 506 as a biasing member for biasing in a direction away from the body 502.

  An inner surface 541 of the central region 544 of the lifter 504 has a convex shape 547 and is in contact with the plunger 503 and the plate 505 as an intermediate member.

  The lifter 504 can rotate with the plunger 503 as a rotation axis. When the pump cam 4 comes into contact with the outer surface 542 of the lifter 504 and rotates, the lifter 504 also rotates.

  The main body 502 functions as a casing, and the fuel 150 is stored in the internal space 520 thereof. The fuel 150 is an example of gasoline in this embodiment, but is not limited to this, and various fuels such as light oil, kerosene, and heavy oil can be used. The fuel 150 is pumped by a plunger 503 as a piston. The plunger 503 can be fitted into the internal space 520 and the volume of the internal space 520 can be changed. Thereby, the plunger 503 can extrude the fuel 150.

  The plunger 530 is provided with an oil seal 508. The oil seal 508 can prevent liquid leakage.

  The tip of the plunger 503 is in contact with the central region 544 of the lifter 504. The plunger 503 is in contact with the convex shape 547 of the lifter 504, and the lifter 504 is rotatable around the plunger 503. The plunger 503 has a cylindrical shape and serves as a rotation axis of the lifter 504. The lifter 504 has a cylindrical shape, and the inner surface 541 is raised in the central region 544. The plunger 503 and the plate 505 are in contact with each other at the raised portion. The lifter 504 has a cylindrical shape with a bottom, and is provided so as to surround the plunger 503. A plate 505 for receiving stress by a spring is disposed on the outer periphery of the plunger 503. The plate 505 is in contact with the inner surface 541 of the lifter 504 in the central region 544, but is not in contact with the inner surface 541 of the lifter 504 in the outer peripheral region 545. The central region 544 has a circular shape, and the outer peripheral region 545 has a donut shape. A spring 506 configured by a coil spring is disposed so as to contact the plate 505 and the main body 502. The spring 506 presses the plate 505 so as to approach the pump cam 4. Thereby, the contact between the pump cam 4 and the lifter 504 is maintained.

  3 to 5 are diagrams for explaining a method of driving the high-pressure fuel pump. Referring to FIG. 3, a high-pressure fuel pump 1 includes a pump inlet 19 as a fuel inlet, an electromagnetic spill valve 18 that prevents backflow of fuel, a plunger 503 for boosting (pressurizing) fuel, and high-pressure fuel. And a check valve 16 for discharging. The fuel path is configured so as to continue from the pump inlet 19 to the plunger 503 and the check valve 16. The plunger 503 moves up and down to pressurize the fuel. At the time of inhalation shown in FIG. 3, the flat portion from the peak portion of the pump cam 4 comes into contact with the lifter 504. As a result, the lifter 504 and the plunger 503 are lowered and the fuel is sucked toward the plunger 503.

  Referring to FIG. 4, when the flat portion of the pump cam 4 is in contact with the lifter 504, the lifter 504 is in the most depressed position, and accordingly, the plunger 503 is also most depressed. It becomes. In this state, the amount of fuel 150 sucked by the plunger 503 is maximized.

  Referring to FIG. 5, when pump cam 4 further rotates from the position shown in FIG. 4, the contact portion between pump cam 4 and lifter 504 approaches the peak portion of pump cam 4. Thereby, the lifter 504 is pushed up and the plunger 503 is also pushed up. At this time, the fuel 150 has a high pressure. Further, at the time of pressure increase, the electromagnetic spill valve 18 is closed, and the fuel 150 does not flow backward to the pump inlet 19 side. When the pressure of the fuel 150 exceeds a predetermined pressure, the fuel 150 is discharged from the check valve 16. The discharged fuel is sent to the injector through the delivery pipe and then injected in the combustion chamber.

  The above is the basic operation of the high-pressure fuel pump 1, but the timing for closing the electromagnetic spill valve 18 can be changed as appropriate. In other words, by closing the electromagnetic spill valve 18 at an optimal timing during the pressurizing process, it becomes possible to control the fuel pressure and the fuel amount as necessary. When the electromagnetic spill valve 18 is closed at an early timing, the effective stroke length of the plunger 503 becomes longer, and more fuel can be pressurized. The fuel pressure is detected by a fuel pressure sensor set in the delivery pipe, and the closing timing of the electromagnetic spill valve 18 can be set using an engine control computer so as to reach a target value.

  Further, the pressure of the discharged high-pressure fuel can be changed according to the operating state. Thereby, reduction of friction loss can be aimed at.

  FIG. 6 is a diagram for explaining rotation of the lifter. The lifter viewed from the direction indicated by the arrow VIB in FIG. 6A is shown in FIG. With reference to FIGS. 6A and 6B, since the pump cam 4 and the center of the lifter 504 are offset, the pump cam 4 contacts and rotates on the bottom surface of the lifter 504. Accordingly, since the lifter 504 also rotates, the frictional resistance between the lifter 504 and the pump cam 4 can be reduced as compared with the case where the lifter 504 does not rotate. The lifter 504 rotates around the plunger 503.

  FIG. 7 is a view showing an inclined plunger. During operation, a lateral force is applied to the plunger 503, and the plunger 503 may be inclined as compared with the position shown in FIG. Clearances B and C are provided between the plunger 503 and the plate 505, and excessive stress between the plunger 503 and the main body 502 can be reduced.

  The contact between the lifter 504 and the plate 505 is limited to the central region 544 of the lifter 504, and a clearance A is secured between the plate 505 and the inner surface 541 of the lifter 504 in the outer peripheral region 545. Thereby, the restraining force of the lifter 504 by the plate 505 is reduced.

  By providing a convex shape 547 in the central region 544 of the lifter 504 and making the plate 505 into a Mt. Fuji type, the discharge amount from the main body 502 of the plunger 503 is reduced. Thus, the stress between the plunger 503 and the main body 502 is reduced by reducing the moment. In addition, the set length of the spring 506 can be secured, and the degree of freedom in designing the spring 506 can be improved.

  FIG. 8 is a graph showing the relationship between the camshaft rotation speed and the lifter rotation speed in the product of the present invention and the conventional product. It can be seen that the lifter rotational speed is improved in the product of the present invention compared to the conventional product. This is because the rotational resistance of the lifter 504 is reduced.

  In the present invention as described above, when the high-pressure fuel pump 1 as a plunger-type high-pressure gasoline pump is driven by the pump cam 4, the contact portion between the plate 505 and the lifter 504 is provided in order to improve the rotational performance of the lifter 504. It is concentrated in the central area 544. Thereby, the braking force is reduced. Furthermore, the lifter 504 can be easily rotated by reducing the braking force, the wear resistance can be improved, and the reliability of the pump drive unit can be improved. Further, clearances B and C are provided between the plunger 503 and the plate 505 so that a large lateral force does not act on the sliding portion between the plunger 503 and the main body 502, and the plunger 503 is plate-shaped while the plunger 503 compresses fuel. The structure is not in contact with 505. Further, a clearance A is provided between the lifter 504 and the plate 505 in the outer peripheral region 545 in order to reduce the braking force by the plate 505 so that the lifter 504 can easily rotate. In order to implement this, for example, a convex shape 547 is provided in the central region 544 of the lifter 504. With this structure, wear of the outer peripheral portion of the lifter 504 can be prevented, and an inexpensive material or surface treatment can be used for the sliding portion between the lifter 504 and the pump cam 4.

  Furthermore, by making the central region 544 of the lifter 504 into a protruding shape and making the plate 505 a Mt. Fuji type, the protruding amount of the plunger 503 can be shortened and the lateral force can be reduced. As a result, it is possible to adopt a structure that ensures the set length of the spring and ensures the degree of freedom in design.

  Although the embodiment of the present invention has been described above, the embodiment shown here can be variously modified.

  First, the valve rocker arm 9 is provided to drive the engine valves 61, 62, but without the valve rocker arm 9, the valve cams 121, 122 push the engine valves 61, 62 directly without going through the rocker arm. It may be lowered.

  In this embodiment, the pump cam 4 is provided on the exhaust side camshaft 58, but the present invention is not limited to this, and the pump cam 4 may be provided on the intake side camshaft 57.

  In this embodiment, a so-called double overhead type engine having two camshafts 57 and 58 is shown. However, the present invention is not limited to this, and an overhead cam type engine constituted by one camshaft is used. The present invention may be applied to an engine. Further, the present invention can be applied to an overhead valve type engine.

  Further, the present invention can be applied to various engines such as a series type, a V type, a W type, and a horizontally opposed type as engine types.

  Further, the present invention can be applied not only to an engine mounted on a vehicle but also to an engine such as a generator. Further, the present invention can be applied to any fuel pump of a gasoline engine or a diesel engine.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used in the field of an engine having a high-pressure fuel pump.

1 is a cross-sectional view of an engine having a high-pressure fuel pump according to the present invention. It is sectional drawing of the high pressure fuel pump shown in FIG. It is a figure for demonstrating the drive method of a high pressure fuel pump. It is a figure for demonstrating the drive method of a high pressure fuel pump. It is a figure for demonstrating the drive method of a high pressure fuel pump. It is a figure for demonstrating rotation of a lifter. It is a figure which shows the inclined plunger. It is a graph which shows the relationship between the camshaft rotation speed and lifter rotation speed in this invention product and a conventional product.

Explanation of symbols

  1 High-pressure fuel pump, 2 Head cover, 3 Cylinder head, 4 Pump cam, 150 Fuel, 502 Main body, 503 Plunger, 504 Lifter, 505 Plate, 506 Spring, 520 Internal space, 541 Inner surface, 542 Outer surface, 544 Central region, 545 Peripheral area, 547 Convex shape.

Claims (3)

A body having an internal space for storing liquid;
A plunger that fits into the internal space and pumps the liquid in the internal space by reciprocating;
A lifter having a central region in contact with the plunger and an outer peripheral region separated from the plunger, and capable of reciprocating the plunger in contact with the inner surface when the outer surface is pressed by a pressing member;
An intermediate member that is in contact with the inner surface of the lifter in the central region of the lifter and is spaced apart from the inner surface of the lifter in the outer peripheral region of the lifter;
A liquid pump comprising: a biasing member that is interposed between the main body and the intermediate member and biases the intermediate member in a direction away from the main body.   The liquid pump according to claim 1, wherein an inner surface of a central region of the lifter has a convex shape and contacts the plunger and the intermediate member. The lifter can rotate around the plunger as a rotation axis,
The liquid pump according to claim 1, wherein when the pressing member contacts and rotates on the outer surface of the lifter, the lifter also rotates.

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