JPH0385366A - Distributor type fuel-injection pump - Google Patents

Abstract

PURPOSE:To prevent oil film breakage by forming a cylindrical recession in a shoe, which gives a fuel press-transferring plunger the operating force, and fitting therein a sub-plunger, which is integrated into one body together with the plunger, in a freely slidable manner, thereby forming a sufficiently strong lubricating oil film between the shoe and a roller. CONSTITUTION:As a rotor 2 rotates, an injection pump receives the operating force via both a roller 5 and a shoe 4, sucks the fuel into the central part of the rotor 5 by means of a plunger 3, which makes reciprocal movement in the direction of the rotor diameter, and discharges the fuel toward a distributing port. In this case, a cylindrical recession 41 is provided in the shoe 4, and a sub-plunger 6 having a small diameter, which is fitted into the recession 41 form a pressure chamber P, which is opened at a roller receiving surface 4a of the shoe 4 via a high pressure passage 42. In addition, the pressure chamber P is connected to the outside through a low pressure passage 61 provided with a check valve, which is closed when the internal pressure of the chamber P goes up. Meanwhile, the sub-plunger 6 is energized to the outside by a coil spring 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distribution type fuel injection pump, and particularly to an inner cam type fuel injection pump that enables high pressure injection.

[Prior Art] Fig. 10 is a sectional view of a main part showing an example of an inner cam type fuel injection pump. Plungers 3 are provided at several locations to be movable in the radial direction. Each plunger 3
Shoes 4 are brought into contact with the outer ends of the rollers, and these shoes 4 have receiving surfaces 4a having an arcuate cross section and hold the rollers 5.

Each roller 5 is in contact with a cam surface 1a on the inner circumference of the cam ring 1. The cam surface 1a has a shape in which the same number of arcuate surfaces as the number of cylinders of the engine are connected, and protrudes inward at equal intervals in the circumferential direction.

The lubricating oil present between the rotor 2 and the cam ring 1 adheres to the outer periphery of the roller 5 in the form of an oil film, and the roller 5 is slidably rotatable relative to the receiving surface 4a due to the lubricating action of the oil film. When the rotor 2 rotates, each roller 5 rolls on the cam surface 1a, and at the same time reaches the protrusion, causing all the plungers 3 to advance toward the center of the rotor 2.

A flow passage 21 is formed in the center of the rotor, which communicates with an inlet port and a distribution port in a known manner. Thus, the low-pressure fuel introduced from the inlet port when the plunger 3 is in the retracted position (the state shown in the figure) is forced into a predetermined distribution port by the advancing operation of the plunger 3.

Incidentally, a fuel injection pump having a shoe and a roller is disclosed in, for example, Japanese Patent Laid-Open No. 145359/1983.

[Problems to be Solved by the Invention] Incidentally, in the conventional fuel injection pump described above, when the fuel injection pressure is increased, the reaction force received by the plunger 3 increases, and the receiving surface 4a of the shoe 4 and the outer circumferential surface of the roller 5 are As a result, the oil film is cut and the smooth rolling of the roller 5 is inhibited, and there is a risk that pitching or the like may occur on the cam surface 1a, which is a bottleneck in high-pressure injection.

The present invention was made in view of this background, and an object of the present invention is to provide a distribution type fuel injection pump that does not cause the oil film to run out even during high-pressure injection, allows the roller to roll smoothly, and performs good pump operation. do.

[Means for Solving the Problems] To explain the present invention in detail, a cam ring 1 (FIG. 4) having a cam surface 1a projecting inward at a radially symmetrical position on an inner circumferential surface, and a A rotor 2 that rotates concentrically and has a distribution port therein, a plunger 3 that is movably disposed in a radial direction at a radially symmetrical position within the rotor 2, and a rotor 2 that rotates and has a distribution port therein; A shoe 4 is provided at the end and has a receiving surface 4a having an arcuate cross section for slidably receiving the roller 5 rolling on the cam surface la.
As the rotor 2 rotates, it receives an operating force via the roller 5 and shoe 4, and the plunger 3, which reciprocates in the radial direction of the rotor, sucks fuel into the center of the rotor and discharges it to the distribution port. is the above shoe 4
A cylindrical recess 41 (Fig. 1) is provided in the
A sub-1 plunger 6 having a smaller diameter is provided at the outer end of the plunger 3 and is slidably fitted into the recess 41.
is formed and opened at the center of the receiving surface 4a by a high pressure passage 42, and an oil reservoir 43 ( 2 and 3>, a spring member 7 is disposed in the pressure chamber P to urge the end face of the sub-plunger 6 toward the outside, and a low pressure is provided to communicate the pressure chamber P with the outside. A passage 61 is provided, and a check valve 62 that closes when the internal pressure of the pressure chamber P rises is provided in the low pressure passage 61.

[Function] In the above configuration, when the roller 5 is located at a location other than the protrusion of the cam surface 1a, the pressure that the sub-plunger 6 receives from the plunger 3 is small, and the spring member 7 pushes the pressure chamber P toward the outside. Internal pressure decreases. Then, the check valve 62 opens and low-pressure lubricating oil is introduced into the pressure chamber P from the outside.

When the roller 5 reaches the protruding part of the cam surface 1a as the rotor 2 rotates, the plunger 3 receives an actuation force via the shoe 4 and the sub-plunger 6, moves into the rotor 2, and pumps fuel at high pressure. Send.

At this time, the sub-plunger 6 receives a reaction force from the plunger 3, moves into the pressure chamber P against the spring force of the spring member 7, and increases its internal pressure.

At this time, since the sub-plunger 6 has a smaller diameter than the plunger 3, the internal pressure of the pressure chamber P becomes sufficiently higher than the fuel discharge pressure, the check valve 62 closes, and the high-pressure lubricating oil flows into the high-pressure passage. 42 and is supplied to the oil reservoir 43 on the receiving surface 4a of the shoe 4, forming a strong oil film.

Thus, even if the plunger 3 receives a reaction force when it delivers high-pressure fuel and this is applied to the oil film through the sub-plunger and the shoe, the oil film will not break and the roller 5
Allows for smooth rotation.

[First Embodiment] FIG. 4 shows a cross section of the main parts of the pump, and the differences from the conventional example will be mainly explained below.

The rotor 2 rotating inside the cam ring 1 has four rotors in the circumferential direction.
Cylinders are cut in the radial direction at several locations, and a plunger 3 is slidably installed in the inner small diameter part of these cylinders, and a shoe 4 is slidably installed in the outer large diameter part. . A sub-plunger 6 having a smaller diameter than the outer end of the plunger 3 is provided in contact with the outer end of the plunger 3.

The shoe 4 has a cylindrical recess 41 at the center of the inner end surface.
is formed (FIGS. 1 and 2), and the tip of the sub-plunger 6 is slidably fitted into the recess 41, and a pressure chamber P is defined within the recess 41. There is. The sub-plunger 6 is formed with a low-pressure passage 61 that passes through the center and bends on the contact surface with the plunger 3 to communicate the pressure chamber P with the outside. The diameter is expanded in steps, and a spherical check valve 62 is provided at the first stepped portion, and a spring receiving plate 71 having a through hole is provided at the next stepped portion.
A coil spring 7 is installed between the spring receiving plate 71 and the end wall of the pressure chamber P.
is arranged.

A high pressure passage 42 connecting the pressure chamber P and the receiving surface 4a is provided at the center of the shoe 4. At the center of the receiving surface 4a where the high pressure passage 42 opens, as shown in FIG.
An oil reservoir 43 having the same width as the diameter of 2 and extending in the longitudinal direction is formed.

In the fuel injection pump having the above structure, if the roller 5 is located at a position other than the protruding part of the cam surface 1a, the X position in FIG.
The pressure that the sub-plunger 6 receives from the plunger 3 is small, and the sub-plunger 6 is pushed toward the outdoors by the coil spring 7.

When the roller 5 reaches the protrusion of the cam surface 1a as the rotor 2 rotates (Y position in FIG. 5), the plunger 3 receives an operating force via the shoe 4 and the sub-plunger 6, and The fuel is delivered under high pressure. At this time, the sub-plunger 6 receives a reaction force from the plunger 3, moves into the pressure chamber P against the spring force of the spring member 7, and increases its internal pressure. Since the sub-plunger 6 has a smaller diameter than the plunger 3, the internal pressure of the pressure chamber P at this time becomes sufficiently higher than the fuel discharge pressure, the check valve 62 closes, and the high-pressure lubricating oil flows through the high-pressure passage 42. The oil is then supplied to the oil reservoir groove 43 on the receiving surface 4a of the shoe 4.

As will be described later, this oil reservoir groove 43 is formed with a suitable area ratio to the area of the receiving surface, so that the high pressure lubricating oil supplied to the groove 43 has sufficient strength between it and the roller 5. Forms an oil film. Thus, even when high-pressure fuel is delivered by the plunger 3, the lubricating oil film does not break, and the roller 5 rotates smoothly without pitching or the like.

When the rotor 2 rotates and the roller 5 passes the protrusion of the cam surface 1a (Z position in FIG. 5), the pressure applied to the plunger 3 and sub-plunger 6 decreases, and the spring force of the coil spring 7 causes the sub-plunger 6 to I am forced to leave room P. As a result, the internal pressure of the pressure chamber P decreases and the check valve 6
2 opens, and low-pressure lubricating oil is introduced into the pressure chamber P from the outside through the low-pressure passage 61.

Note that the plunger 3 gradually moves outward in the radial direction under the pressure of the low-pressure fuel, and the roller 5 comes into contact with the cam surface 1a again.

Now, the ratio (%) of the area A of the oil sump groove 43 to the projected area AO of the receiving surface 4a is variously changed, and the fuel injection pressure at which the rolling of the roller 5 stops is investigated, and the results are shown on the line X in Figure 6. Indicated by The line y in the figure is the conventional example.

As can be seen from the figure, the fuel injection pressure that stops rolling in the range from around 4% to 6% exceeds the conventional one,
Considering processing issues, etc., the above area ratio is 2.5 to 5%.
It is best to set it within the range of . The length of the arm 43 is 2/3 of the axial length of the receiving surface 4a in order to prevent oil film pressure from leaking.
The width of the groove (i.e., the diameter of the high pressure passage) is determined to satisfy the above area ratio.

[Second Embodiment] In FIG. 7, unlike the first embodiment (FIG. 1), the bent portion of the low pressure passage 61 is formed on the side wall of the sub-plunger 6 instead of on the end surface, which makes machining easier. It's easy.

[Third Embodiment] The low pressure passage 61 may be formed within the shoe 4 as shown in FIG.

[Fourth Embodiment] During operation, the angle formed by the plunger 3 and the shoe 4 may vary, and in order to maintain good sliding of the sub-plunger 6 even in such a case, as shown in FIG. The contact surface 3a of the sub-1 langeer 6 is made spherical.

[Effects of the Invention] As described above, according to the distribution type fuel injection pump of the present invention,
A sufficiently strong lubricating oil film can be formed between the roller and the shoe that applies the operating force to the fuel pumping plunger, so the oil film will not be cut off by the plunger reaction force when fuel is delivered at high pressure, and the fuel High pressure injection can be performed satisfactorily.

[Brief explanation of drawings]

1 to 6 show a first embodiment of the present invention.
The figure is a cross-sectional view of the shoe, Figure 2 is a longitudinal cross-sectional view of the shoe, Figure 3 is a view taken in the direction of arrow A in Figure 2, Figure 4 is a cross-sectional view of the pump section,
FIG. 5 is a sectional view showing the operating process, FIG. 6 is a graph showing the effects of the invention, FIGS. 7 to 9 are longitudinal sectional views of shoes showing second to fourth embodiments of the invention, respectively. FIG. 10 is a sectional view of a pump section showing a conventional example. 1... Cam ring 1a... Cam surface 2... Rotor 3... Plunger 4... Shoe 4a... Receiving surface 41... Recess 42... High pressure passage 43... Oil reservoir Groove 5...Rotor 6...Sub plunger 61...Low pressure passage 62...Check valve 7...Coil spring (spring member) P...Pressure chamber Fig. 3 Fig. 4 Fig. 6 Figure 7z Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] A cam ring that has a cam surface that protrudes inward at radially symmetrical positions on its inner peripheral surface, a rotor that rotates concentrically within the cam ring, and has a distribution port therein; Plungers are arranged at symmetrical positions so as to be movable in the radial direction, and a shoe is provided at the outer end of each plunger and has a receiving surface with an arcuate cross section that slidably receives the roller rolling on the cam surface. Distributed fuel injection, which receives operating force through rollers and shoes as the rotor rotates, and sucks fuel into the center of the rotor by the plunger that reciprocates in the radial direction of the rotor and discharges it to the distribution port. In the pump, a cylindrical recess is provided in the shoe, and a sub-plunger with a smaller diameter is provided at the outer end of the plunger, and this is slidably fitted into the recess, and the end surface of the sub-plunger and the recess are provided. A pressure chamber is formed in some places, and this is opened in the center of the receiving surface by a high pressure passage, and an oil sump groove is formed in the receiving surface that has the same width as the opened high pressure passage and extends in the axial direction of the receiving surface. A spring member is disposed in the pressure chamber to urge the end face of the sub-plunger toward the outside, and a low pressure passage is provided to communicate the pressure chamber with the outside, and the low pressure passage is provided with a spring member that biases the end face of the sub-plunger toward the outside. A distribution type fuel injection pump characterized by being provided with a check valve that closes when the pump is closed.