JPH05157042A - Radial piston pump for low-viscosity fluid - Google Patents

Abstract

PURPOSE:To prevent adhesion of carbon or seizure on an impulse part between a piston and a cylinder bore by dislocating a center axis of the piston in the direction opposite to the rotation direction of a pump shaft. CONSTITUTION:There are provided a fixed cylinder in which an intake passage and a discharge passage for a fluid with low viscosity are formed and a plurality of pistons 51, each of which are arranged in capable of reciprocating in a plurality of cylinder bores 23 formed in the radial state in this fixed cylinder 3. Also, an eccentric cam 16 of a pump shaft for reciprocating the pistons 51 is provided. And a center axis PC of the piston 51 is dislocated from a center CC of the pump shaft in the direction opposite to the rotation direction of the pump shaft so that the center axis PC of the piston 51 does not pass the center CC of the pump shaft. By this, the piston 51 is prevented from falling down, and adhesion of carbon and seizure to its impulse part can be appropriately prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial piston pump for low-viscosity fluid, and is particularly suitable for preventing the piston from collapsing and for pumping a low-viscosity fluid such as fuel such as gasoline or alcohol under high pressure. The present invention relates to a radial piston pump for low viscosity fluid.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for improving combustion efficiency as a countermeasure against pollution problems and resource depletion problems caused by exhaust gas from internal combustion engines such as vehicles. When using gasoline, it is effective to promote atomization of the spray by increasing the pressure. Further, the use of alcohol or something similar thereto (hereinafter simply referred to as alcohol) in place of gasoline has been considered. Since this alcohol is inferior in cold startability, it is necessary to atomize it by increasing the pressure.

In order to realize such atomization, a fuel pump capable of exhibiting a high pressure performance of a discharge pressure of 70 to 100 Kgf / square centimeter is required in place of the discharge pressure of a normal fuel pump of 3 to 4 Kgf / square centimeter. is there. As one type of this fuel pump,
Radial piston pumps are considered in terms of capacity and efficiency. For example, there is JP-A-60-216081. However, the conventional radial piston pump is
As a hydraulic pump, that is, a highly viscous oil (viscosity of 30 cst or more) as disclosed in Japanese Patent Laid-Open No. 64-367.
It was generally used as a pressure feeding means of the. That is, when used for a highly viscous oil, there is no problem in performance, but alcohol has a very low viscosity of about 0.5 cst.

When a low-viscosity fuel having such characteristics is to be discharged at high pressure, the pump structure is changed from a rotary type in which the cylinder block rotates to a fixed cylinder type in which only the piston reciprocates while the cylinder block is fixed. The pump performance cannot be maintained only by doing. That is, for example, the problem that the grease enclosed in the bearing of the drive shaft is washed and diluted by the low-viscosity fuel, and the problem of galling or seizure between the piston and the barrel or between the eccentric cam and the tip of the piston occurs. Cannot be eliminated. That is, there is a problem that the conventional radial piston pump cannot smoothly and stably pump the low-viscosity fuel under high pressure.

In order to solve these problems, the applicant of the present invention, namely, uses a low-viscosity fuel typified by gasoline or alcohol without damaging the bearing portion and causing galling or seizure on the sliding portion of the piston. None, 70K
As a practical radial piston pump capable of stably performing the pumping action even at a high pressure of gf / square centimeter or more, a radial piston pump for low-viscosity fuel oil has been developed by Japanese Patent Laid-Open No. 3-175158.

The radial piston pump 1 for low viscosity fuel will be described below with reference to FIGS. 9 to 12.
9 is an overall sectional view of the radial piston pump 1 for low viscosity fuel, FIG. 10 is an exploded perspective view, and FIG. 11 is XI-XI of FIG.
1 is a cross-sectional view of a radial piston pump 1 for low-viscosity fuel, which includes a housing 2, a fixed cylinder 3, and a cover 4.
A suction side gasket 5 and a suction side leaf valve 6; a discharge side gasket 7 and a discharge side leaf valve 8; and a pump shaft 9. The housing 2, the fixed cylinder 3, the cover 4, the suction side gasket 5, the suction side leaf valve 6, the discharge side gasket 7, and the discharge side leaf valve 8 are positioned by the positioning pin 10 and the stud bolt 11 is positioned. To fix them together.

[0007] The pump shaft 9 is rotatably inserted into the thus integrated inner hole portion. The pump shaft 9 is supported by a radial bearing 12 provided in the housing 2, a thrust bearing 13 and a radial bearing 14 provided in the cover 4. The bearing is rotatably driven by an external engine (not shown) through the drive pulley 15. An eccentric cam 16 is formed at a portion of the pump shaft 9 located inside the fixed cylinder 3.

The housing 2 is provided with a first oil seal 17 and a second oil seal 18 on the left and right sides of the radial bearing 12, so that the grease filled in the radial bearing 12 is diluted with a low-viscosity fuel having cleanability. Is being prevented. The housing 2 has a fuel intake port member 1
9 is attached and communicates with the suction port member 19, and the number of cylinder holes 23 or cap-shaped pistons 24 described later (for example, 5 as shown in FIG. 11 is provided therein).
Number of suction passages 20 and radial annular chamber inlets 2
1, and the central inner space 22 is formed. The annular chamber inlet 21 introduces a low-viscosity fuel into an annular chamber 33 described later,
It is an introduction passage for supplying this to the plurality of cylinder holes 23 and performing lubrication.

A plurality of fixed cylinders 3 (for example, 5
This cylinder hole 23 is radially provided at equal angular intervals, and a cap-shaped piston 24 is reciprocally housed inside the cylinder hole 23. The piston 24 biases the piston 24 in the centripetal direction by a spring 26 provided between the piston 24 and a plug 25 fixed by screwing in the cylinder hole 23. The head of the piston 24 abuts and slides on the eccentric cam 16 of the pump shaft 9 and reciprocates under the action of the eccentric cam 16 to perform a pumping action of sucking and discharging the low-viscosity fuel. The sliding portion between the piston 24 and the eccentric cam 16 is located substantially at the center of the fixed cylinder 3.

A suction side passage 27 and a discharge side passage 28 are formed in the fixed cylinder 3 on the left and right sides of the cylinder hole 23 so as to communicate therewith. The suction side passage 27 and the discharge side passage 28 communicate these with a pressurizing chamber 29 (FIG. 11) formed between the piston 24 and the plug 25.

The leaf valve 6 on the suction side is provided with a suction valve 30 (FIG. 10) consisting of a tongue spring.
A substantially rectangular stopper 31 arranged in the fixed cylinder 3.
The movable range is controlled by the above, and fuel can be selectively sucked from the suction valve 30 and the suction side passage 27 in accordance with the reciprocating movement of the piston 24.

The central inner space 32 of the fixed cylinder 3 is
An annular chamber 33 for suction lubrication is formed together with the central inner space 22 of the housing 2.

The cover 4 has a discharge passage 34 communicating with the discharge side passage 28 of the fixed cylinder 3, and the discharge passage 34 is provided with a discharge port member 36 via an annular collecting groove 35 (FIG. 10).
Is in communication with.

A discharge valve 37 (FIG. 10) formed of a tongue-shaped spring is formed on the leaf valve 8 on the discharge side, and its movable range is controlled by a substantially rectangular stopper 38 arranged in the cover 4, and the piston 24 According to the reciprocating motion of
Fuel can be selectively discharged from the discharge passage 28 and the discharge valve 37.

By providing a third oil seal 39 on the cover 4, it is possible to prevent the grease filled in the radial bearing 14 from being diluted with the low-viscosity fuel, and to prevent the third oil seal 39 and the second oil seal 39 from being diluted. Oil seal 18
By means of the annular chamber 3 at the pump shaft 9
3 can be shut off from the outside.

Further, as shown in FIG. 12, the cover 4 includes:
The relief valve 40 is provided in communication with the discharge passage 34 and the discharge port member 36, and the annular chamber 3 is provided at the valve opening position.
By forming the return hole 41 communicating with the fuel cell 3, the low viscosity fuel is returned to the annular chamber 33 when the low viscosity fuel has an abnormally high pressure.

Thus, the low-viscosity fuel in the fuel tank 42 is supplied to the suction port member 19 by the feed pump 43 (FIG. 9), and the piston 24 that reciprocates by sliding on the eccentric cam 16 by the rotational driving of the pump shaft 9. Is pumped to a predetermined injector 44 under high pressure.

That is, in the suction process in which the piston 24 moves toward the centripetal direction, the suction valve 30 opens and the discharge valve 37 closes, and the suction port member 19 passes through the suction passage 20 and the suction valve 30 passes through the suction side passage. 27
And is sucked into the pressurizing chamber 29. Also the piston 24
In the discharging process in which the suction valve 3 moves toward the centrifugal direction, the suction valve 3
When 0 is closed, the discharge valve 37 is opened, and high pressure is sent from the pressure chamber 29 through the discharge passage 28, the discharge valve 37, the discharge passage 34, and the discharge port member 36 to the injector 44.

The low-viscosity fuel that has entered the annular chamber 33 from the annular chamber inlet 21 is blocked from the outside at the pump shaft 9 by the second oil seal 18 and the third oil seal 39 inside the annular chamber 33. So it can be filled inside. Therefore, the piston 2
4 and the eccentric cam 16 and between the cylinder hole 23 and the piston 24 can be lubricated. That is, the low-viscosity fuel itself can be guided to the annular chamber 33 inside the fixed cylinder 3 and used as the lubricating oil for the piston 24 and the eccentric cam 16.

However, since the head portion of the piston 24 has an arcuate cross section, the sliding contact portion with the eccentric cam 16 has a dot shape. Therefore, especially in the case of high-pressure and high-speed rotation, the surface pressure of the sliding contact portion becomes high, so that the wear of the sliding contact portion also becomes a problem as the discharge pressure becomes high.

In order to solve such a problem, Japanese Unexamined Patent Publication (Kokai) No.
If the discharge pressure is constant by providing a regular polygonal ring between the eccentric cam and the piston and making the head of the piston flat, as in No. 16370.
There is one that can reduce the surface pressure between the head of the piston and the ring.

The main part of such a configuration will be outlined with reference to FIGS. 13 to 16. However, in the following description, the same parts as those in FIGS. 9 to 12 are designated by the same reference numerals, and the detailed description thereof will be omitted. FIG. 13 is a longitudinal cross-sectional view of a main part of the central inner space 32 or the annular chamber 33 of the fixed cylinder 3 in this radial piston pump. However, for simplification, only one of the five cylinder holes 23 formed in a radial shape communicating with the central inner space 32 is shown. FIG. 13 shows the state at the time of starting the intake of fuel, FIG. 14 shows the state during the intake, FIG. 15 shows the state at the start of the compression of fuel, and FIG. 16 shows the state during the compression in sequence. 16 shows a state in which the angle is rotated by 90 degrees. Note that FIG. 17 is a graph showing the moment to the piston 51 with respect to the rotation angle of the eccentric cam 16 with respect to its rotation, the eccentric amount of the center EC of the eccentric cam 16 from the central axis PC of the piston 51, and the pressure acting on the piston 51. Is.

As shown in FIGS. 13 to 16, a ring 50 having a regular pentagonal outer shape is provided on the outer periphery of the eccentric cam 16. The eccentric cam 16 can rotate in sliding contact with the inner wall surface of the ring 50. Further, inside the cylinder hole 23, a piston 51 corresponding to the piston 24 but having a flat head is housed so as to be slidably contactable with the outer surface of the ring 50.

In such a structure, the flat outer surface of the ring 50 and the flat head portion of the piston 51 are in surface contact with each other. Therefore, even when the rotation speed is high, the discharge pressure is constant. , The surface pressure can be reduced.

However, with the rotation of the pump shaft 9, the ring 50 or the eccentric cam 16 is swinging. The moment generated due to this swinging motion causes the problem that the piston 51 reciprocates with the piston 51 slightly tilted from its central axis.

In each figure, the center of the pump shaft 9 is CC. The center CC of the pump shaft 9 coincides with the centers of the fixed cylinder 3 and the central inner space 32. EC is the center of the eccentric cam 16. The center EC of the eccentric cam 16 coincides with the center of the ring 50. The central axis of the piston 51 is PC.

However, in the conventional radial piston pump, the central axis PC of the piston 51 passes through the center CC of the pump shaft 9.

First, as shown in FIG. 13, when starting the intake of fuel, the eccentric cam 16 rotates around the center CC of the pump shaft 9 as the center of rotation by the rotation of the pump shaft 9 in the counterclockwise direction from the illustrated state. To do. This turning radius is the center CC of the pump shaft 9 and the eccentric cam 1.
6 is the distance from the center EC, that is, the eccentric distance E.

With the rotation of the eccentric cam 16, the ring 50 is guided by the rotating eccentric cam 16 without rotating itself, and the eccentric distance E is set to the eccentric radius along the inner wall of the central inner space 32. Displace along a circular orbit.

Next, in the state shown in FIG. 14, the center EC of the eccentric cam 16 is displaced leftward from the center CC of the pump shaft 9 by the eccentric distance E.

In the state where the eccentric cam 16 is rotated 90 degrees further from FIG. 14 and is rotated 180 degrees as shown in FIG.
C is located below the center CC of the pump shaft 9 by an eccentric distance E and on the center axis PC of the piston 51. In the displacement up to this point, the piston 51 moves the spring 26
The fuel is sucked by being biased by the eccentric cam 16 and the ring 50 to descend and follow.

As shown in FIG. 17, the moment and pressure applied to the piston 51 are zero.

However, in the process from the start of compression shown in FIG. 15 to the process of compression shown in FIG. 16 and the end of compression shown in FIG. 13, that is, the start of suction, a moment for tilting the piston 51 is generated.

That is, when the ring 50 tries to push up the piston 51 upward against the urging force of the spring 26, there is a gap between the center EC of the eccentric cam 16 or the ring 50 and the center axis PC of the piston 51. Since there is a predetermined amount of deviation, as shown in FIG.
6 forces FS to push the piston 51 downward and the eccentric cam 16
A moment is generated by the force FE that the ring 50 tries to push up the piston 51, and this moment acts to force the piston 51 to the left side in FIG.

Therefore, the piston 51 has the cylinder hole 2
By falling inside 3, the clearance of the sliding part with the cylinder hole 23, especially the clearances of the parts A and B is reduced and the fuel does not pass through this part and the oil film is cut off during this part, so the lubrication effect by the fuel is expected. Can not do it.

In other words, since the state is close to that of metal contact, the deterioration of the low-viscosity fuel adheres to the sliding portion between the cylinder hole 23 and the piston 51, or seizure occurs. There is a problem that causes the failure of.

Such a problem also occurs in the case of the piston 24 having the arcuate head portion in the radial piston pump 1 shown in FIGS.

At the same time as the generation of the moment from the start to the end of compression as described above, the head of the piston 51 is moved by the frictional force between the ring 50 and the piston 51 during the full rotation of the eccentric cam 16. There is also the problem of being dragged in the left and right reciprocating motion directions.

That is, in the rotation range of the rotation angle of the eccentric cam 16 shown in FIG. 16 from 270 degrees to the rotation angle of 90 degrees shown in FIG. Since the ring 50 moves to the left in the figure, the head of the piston 51, which is in contact with the upper surface of the ring 50, is also dragged to the left.

Further, from the rotation angle of 90 degrees in FIG.
The rotation angle 27 of FIG.
In the rotation range up to 0 degrees, the ring 50 moves to the right in the figure, so the head of the piston 51 is also dragged to the right.

Therefore, for example, FIGS.
In the compression process of No. 1, the head of the piston 51 remains the same between the rotation angles of 180 degrees and 270 degrees due to the movement of the ring 50 to the right in the figure based on the counterclockwise rotation of the eccentric cam 16. Dragged to the right. As a result, in addition to the above-mentioned moment, the piston 51 acts so as to tilt further to the left.

However, in the rotation range from FIG. 16 to FIG. 13, since the ring 50 moves to the left, a force acts in a direction that slightly corrects the tilt of the piston 51. Of course, the force of this friction does not completely prevent the piston 51 from falling.

During the suction process in which no moment is generated (FIGS. 13 and 14), the above-mentioned frictional force is
14 to 15, it causes a force that tilts the piston 51 to the right in the drawing, and in the rotation range of FIGS. 14 to 15, it causes a force that tilts the piston 51 to the left in the drawing.

However, the piston 5 due to such frictional force
The action on 1 is smaller and slightly smaller than that due to the moment generated in the compression process, and it is more important to solve the problem due to the moment in the compression process in the radial piston pump for low viscosity fuel.

[0045]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a radial piston pump for low viscosity fluid, the moment generated in the piston portion based on the movement of the eccentric cam or ring is controlled. An object of the present invention is to provide a radial piston pump for a low-viscosity fluid that ensures smooth reciprocating motion of the piston by minimizing the amount and prevents carbon adhesion and seizure of the sliding part between the piston and the cylinder hole. And

[0046]

That is, according to the present invention, the moment generated due to the displacement of the eccentric cam can be reduced by shifting the center axis of the reciprocating piston from the center of the pump shaft in advance. Focusing on, a fixed cylinder in which a suction side passage and a discharge side passage for a low-viscosity fluid are formed, and a plurality of pistons respectively reciprocally arranged in a plurality of cylinder holes radially formed in the fixed cylinder, An eccentric cam of a pump shaft that reciprocates these pistons, and a low viscosity that sucks and discharges the low-viscosity fluid from the suction side passage and the discharge side passage by reciprocating movement of the piston along its central axis. A radial piston pump for fluid, wherein the central axis of the piston is from the center of the pump shaft, The direction of rotation of Npushafuto shifted in the opposite direction, the central axis of the piston is low viscosity fluid radial piston pump, characterized in that to not pass through the center of the pump shaft.

[0047]

In the radial piston pump for low viscosity fluid according to the present invention, the central axis of the reciprocating piston is displaced in advance from the center of the pump shaft or the fixed cylinder in the direction opposite to the direction of rotation of the eccentric cam.
In the process of compressing the fluid, the moment generated due to the displacement of the eccentric cam can be reduced, so it is possible to minimize the extent to which the piston falls from the central axis of the cylinder bore, and the piston lubricates with the fluid. It is possible to guarantee the operation and prevent the seizure and the accumulation of fluid deterioration products.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A radial piston pump 60 for a low viscosity fuel according to an embodiment of the present invention, particularly a ring 50 portion, will be illustrated and described with reference to FIGS. FIG. 1 shows the state at the start of fuel intake, FIG. 2 shows the state during intake, FIG. 3 shows the state at the start of fuel compression, and FIG. 4 shows the state during compression. Note that FIG. 5 shows the moment to the piston 51 with respect to the rotation angle of the eccentric cam 16 with respect to its rotation, the eccentric amount of the center EC of the eccentric cam 16 from the central axis PC of the piston 51, and the pressure acting on the piston 51, respectively. It is a graph.

Radial piston pump 60 for low viscosity fuel
13 to 16 is different from that shown in FIGS. 13 to 16 in that the center axis PC of the piston 51 does not pass through the center CC of the pump shaft 9 in the fixed cylinder 3 so that the position of the cylinder hole 23 is eccentric from the center CC. In a direction opposite to the rotation direction of 16 (to the right in the figure), a gap H is previously set.
That is, the setting was made by shifting it.

Specifically, even at the top dead center of the piston shown in FIG. 1, that is, when the suction is started, unlike the state in the conventional radial piston pump 1 for low viscosity fuel shown in FIG. The central axis PC of is located at a position displaced to the right from the center CC of the pump shaft 9. In addition, the above-mentioned gap H (offset amount) is arbitrarily determined according to the pump.

In this structure, the pump shaft 9
The rotation of the eccentric cam 16 causes the center C of the pump shaft 9 to move.
It rotates counterclockwise from the state shown in the figure with C as the center of rotation.

As shown in FIG. 5, in the state from the intake of fuel to the start of compression shown in FIGS. 1 to 3, the piston 51 is urged by the spring 26 and eccentric cam 16 and ring 5 are urged.
Since only the fuel is sucked by descending following 0, the moment and the pressure are the same as in the states of FIGS. 13 to 15.

Regarding the amount of eccentricity of the center EC of the eccentric cam 16 from the central axis PC of the piston 51, the center EC of the eccentric cam 16 is displaced leftward from the center CC of the pump shaft 9 by the eccentric distance E ( It becomes maximum (E + H) in FIG. 2).

Further, when the piston 51 descends and the fuel is sucked, the piston 51 pushes the eccentric cam 16 or the ring 50 by the urging force of the spring 26, and there is the action of a moment to suppress the rotation of the eccentric cam 16. ,
The biasing force of the spring 26 is small with respect to the force of the fuel, and does not cause a problem.

As shown in FIG. 5, the moment begins to be generated from the start of compression shown in FIG. 3 (bottom dead center of the piston 51),
The moment is kept low during the compression shown in FIG. 4 and in the process from the end of the compression shown in FIG. 1, that is, the start of suction.

That is, in the 270-degree rotation state shown in FIG. 4, the pressure on the piston 51 becomes maximum, but since the center CC of the pump shaft 9 and the center axis PC of the piston 51 coincide, the spring 26 causes the piston 26 to move. 51, the direction of action of the force FS pushing downward, and the eccentric cam 16 or the ring 50.
Are opposite to the acting direction of the force FE that tries to push up the piston 51, the moment becomes zero at this time.

From the 270 degree state (FIG. 4) to the 360 degree inhalation start state (FIG. 1), a moment is generated again, but since the moment arm is shorter than in the conventional case, the moment The value is kept low.

In short, in the example shown in the drawing, the center axis PC of the piston 51 and the center CC of the pump shaft 9 are displaced in advance by a predetermined amount, whereby the spring 26
Ring 50 pushes the piston 51 upward against the urging force of the
In the state where the rotation angle is 270 degrees in which the pressure acts most on 1 and the discharge pressure is applied, the central axis PC of the piston 51 and the center EC of the eccentric cam 16 approach or intersect each other. By crossing the directions of the forces and minimizing the deviation between the force point and the action point of the eccentric cam 16 or the ring 50,
Moment can be prevented from occurring.

Therefore, it is possible to reciprocate the piston 51 in the cylinder hole 23 along the central axis PC while preventing the piston 51 from falling, and to cut the oil film between the piston 51 and the cylinder hole 23. Without doing so, the lubricating action can be guaranteed by keeping the clearance of the sliding portion constant.

Next, the moment at the contact point between the piston 51 and the eccentric cam 16 or the ring 50 will be calculated. FIG. 6 is a schematic illustration of the above-mentioned configuration (however, it is exaggerated for clarity), the generated moment is M, the center EC of the eccentric cam 16 and the center CC of the pump shaft 9 are shown. The eccentricity interval (amount of eccentricity) between E,
The displacement distance between the center axis PC of the piston 51 and the center CC of the pump shaft 9 is H, the general displacement distance between the center EC of the eccentric cam 16 and the contact P is D, and the rotation angle is θ (the piston's When the force acting on the piston 51 by the eccentric cam 16 or the ring 50 is F, the equations shown in FIG. 7 hold.

That is, the moment M is expressed by the equation (1). The displacement distance D is represented by the equation (2).

The displacement of the piston 51 is expressed as -Ecos θ, and becomes -E at the bottom dead center of θ = 0 and + E at the top dead center of θ = π.

The rising speed of the piston 51 is Eωsin θ
Is expressed as However, ω indicates the angular velocity.

Assuming that the pressure acting on the piston 51 is proportional to this ascending speed, if the axial pressure during the rotation of the piston 51 is T, this T is expressed by equation (3). Therefore, T is calculated by the equation (4).

Since the direction of the moment is reversed at θ = α, T is expressed by equation (6).

Therefore, when H that minimizes T is obtained, from the calculation such as equation (7), when H / E takes the value of equation (8), dT / dH = 0, and T is minimized. can do.

FIG. 8 shows a table of these calculation results. As is clear from this table, when H = 0, that is, when there is no deviation between the central axis PC of the piston 51 and the center CC of the pump shaft as in the conventional case, the axial pressure T
= Π / 2E (about 1.57E). This value is 100%
Then, when the shift interval H is set as shown in the table,
The axial pressure T is 22% and 27%, respectively, which shows that the case of the formula (8) has the smallest T.

Thus, the piston 51 and the cylinder hole 23
It is possible to eliminate the seizure of the sliding part between and and the adhesion of carbon.

Further, the plate bearing mounted inside the eccentric cam 16, that is, between the eccentric cam 16 and the pump shaft 9 is softer than the other parts, but the deviation of the direction of the force generated as in the conventional case. Became a shearing force and caused wear and damage, but as a result of suppressing the generation of the moment as described above, the wear can be suppressed.

Further, since it is only necessary to change the formation position of the cylinder hole 23 without changing the shape of the conventional radial piston pump 1 for low-viscosity fuel, it is advantageous in manufacturing.

[0071]

As described above, according to the present invention, by shifting the relative position between the cylinder hole in which the piston reciprocates and the central inner space, the central axis of the piston and the center of the pump shaft are mutually displaced. Since the generation of the moment is suppressed by shifting the piston, it is possible to prevent the piston from falling down, and it is possible to accurately prevent carbon from sticking to or seizing the sliding portion of the piston.

[0072]

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a central inner space 32 or an annular chamber 33 of a fixed cylinder 3 in a radial piston pump 60 for low-viscosity fuel according to an embodiment of the present invention, showing a state at the time of starting fuel intake. FIG.

FIG. 2 is a vertical cross-sectional view of relevant parts showing a state during fuel intake.

FIG. 3 is a longitudinal sectional view of relevant parts showing a state at the start of fuel compression.

FIG. 4 is a vertical cross-sectional view of relevant parts showing a state during compression of fuel.

FIG. 5 is a diagram showing the moment of the eccentric cam 16 with respect to the rotation angle of the eccentric cam 16 as the eccentric cam 16 rotates.
5 is a graph showing the amount of eccentricity of the center EC of the piston 51 from the central axis PC and the pressure acting on the piston 51.

FIG. 6 is an explanatory view diagrammatically illustrating the configuration of FIGS. 1 to 4;

FIG. 7 is a diagram showing each equation for calculating a moment at a contact point between the piston 51 and the eccentric cam 16 or the ring 50.

FIG. 8 is a table showing axial pressure during rotation of the piston 51 with respect to the gap H.

FIG. 9 Conventional radial piston pump 1 for low-viscosity fuel
FIG.

FIG. 10 is a radial piston pump 1 for low viscosity fuel of the same.
FIG.

11 is a sectional view taken along line XI-XI of FIG.

FIG. 12 is a vertical sectional view of a relief valve 40 portion of the same.

FIG. 13 is a vertical cross-sectional view of a main inner space 32 or an annular chamber 33 of a fixed cylinder 3 in a conventional radial piston pump, showing a state at the time of starting fuel intake.

FIG. 14 is a vertical cross-sectional view of relevant parts showing a state during fuel suction.

FIG. 15 is a longitudinal sectional view of relevant parts showing a state at the time of starting compression of fuel.

FIG. 16 is a vertical cross-sectional view of relevant parts showing a state during compression of fuel.

FIG. 17 is a diagram showing a moment of the eccentric cam 1 with respect to a rotation angle of the eccentric cam 16 as the eccentric cam 16 rotates.
6 is a graph showing the amount of eccentricity of the center EC of 6 from the central axis PC of the piston 51 and the pressure acting on the piston 51.

[Explanation of symbols]

1 Radial Piston Pump for Low Viscosity Fuel 2 Housing 3 Fixed Cylinder 4 Cover 5 Suction Side Gasket 6 Suction Side Leaf Valve 7 Discharge Side Gasket 8 Discharge Side Leaf Valve 9 Pump Shaft 10 Positioning Pin 11 Stud Bolt 12 Radial Bearing 13 Thrust bearing 14 Radial bearing 15 Drive pulley 16 Eccentric cam 17 First oil seal 18 Second oil seal 19 Suction port member 20 Suction passage 21 Radial annular chamber inlet 22 Central inner space 23 Cylinder hole 24 Cap-shaped piston 25 Plug 26 Spring 27 Suction-side passage 28 Discharge-side passage 29 Pressurizing chamber 30 Suction valve 31 Nearly rectangular stopper 32 Central inner space 33 Intake lubrication annular chamber 34 Discharge passage 35 Assembly groove 36 Discharge port member 37 Discharge port Lube 38 Almost rectangular stopper 39 Third oil seal 40 Relief valve 41 Return hole 42 Fuel tank 43 Feed pump 44 Injector 50 Regular pentagonal ring 51 Piston 60 Radial piston pump for low viscosity fuel CC Pump shaft 9 center ( Center of fixed cylinder 3 and central inner space 32) EC Center of eccentric cam 16 (center of ring 50) PC Central axis of piston 51 E Distance between center CC of pump shaft 9 and center EC of eccentric cam 16 (eccentric distance) ) Center axis PC of H piston 51 and pump shaft 9
Gap (offset amount) from the center CC of the FS FS The force that the spring 26 pushes the piston 51 downward FE The force that the eccentric cam 16 or the ring 50 tries to push the piston 51 up D The center EC of the eccentric cam 16 and the contact point P General displacement distance F between the piston 5 and the eccentric cam 16 or ring 50
Force acting on 1

Claims (1)

[Claims] 1. A fixed cylinder having a suction-side passage and a discharge-side passage for a low-viscosity fluid, and a plurality of pistons reciprocally disposed in a plurality of cylinder holes radially formed in the fixed cylinder. An eccentric cam of a pump shaft that reciprocates these pistons, and reciprocates along the central axis of the piston to suck and discharge the low-viscosity fluid from the suction side passage and the discharge side passage, respectively. A radial piston pump for low-viscosity fluid, wherein the central axis of the piston is displaced from the center of the pump shaft in a direction opposite to the rotation direction of the pump shaft.