JP2000027761A - Bellows type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bellows type pump aiming at improvement of durability of a bellows while preventing loose-out of a columnar member in a bellows type pump provided with the columnar member for lowering the waste volume inside of the bellows by effectively reducing the waste volume inside of the bellows while eliminating contact of the bellows with the columnar member. SOLUTION: A cylindrical member 39 for lowering the waste volume of a pump chamber 24 is arranged inside of a bellows 20 along the axial direction of the bellows 20. An end of an end plate 22 of the cylindrical member 39 and an end of a pedestal 23 are provided with large diameter parts 39A, 39B formed larger than the diameter of a nearly intermediate part of the cylindrical member 39 positioned at a gathers part 20A, and the nearly intermediate part of the columnar member 39 positioned at the gathers part 20A of the bellows 20 is formed into a nearly hand drum shape, of which intermediate part in the axial direction is narrowed. With this structure, a clearance between the columnar member 39 arranged in the bellows 20 and the gather part 20A of the bellows 20 is set larger than a clearance between the end plate 22 of the columnar member 39 and the pedestal 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bellows type pump used for a fuel supply device of an internal combustion engine and the like.
The present invention relates to a technique for reducing a waste volume in a bellows.

[0002]

2. Description of the Related Art In an internal combustion engine that supplies fuel by using an injector, a higher fuel pressure is often advantageous in view of atomization of injected fuel and prevention of generation of vapor in a fuel passage. As a pump that can easily obtain a relatively high pressure, there is a plunger pump that pressurizes fuel by a plunger that slides in a cylinder.However, in a plunger pump that seals at a gap between the cylinder and the plunger, for example, as a fuel, When gasoline having a relatively low viscosity is used, the amount of leakage from the gap becomes excessive, and the consumption torque may increase.

As a technique for solving the above problems, there is known a bellows type pump in which a pump chamber is formed in each of a plurality of bellows which can expand and contract, and each bellows is operated to expand and contract to perform a pump action. (Japanese Patent Laid-Open No. 9-1
No. 95944). Conventionally, in such a bellows type pump, the structure of the bellows and the mounting structure thereof are as shown in FIG.

That is, each bellows 41 is connected to the pump head 4
2, a plurality of bellows storage holes 4 formed around a central axis of a cylinder 45 disposed in a pump casing 43 fixed to the support plate 44 on the pump head 42 side.
6 is stored. Each bellows 41 has a fold 41A,
The plunger 41A is fixed to one end of the pleat 41A, and is located in a concave portion of a slide guide 47 slidably disposed in the bellows storage hole 46. And an annular base 49 fixed to the other end of the fold 41A.

Each pedestal 41 is fixed to a support plate 44 by a cylinder 45. Each of the bellows 41 whose base end is fixed in this manner is extended and contracted by the swinging motion of a swash plate 50 as a bellows operating member that comes into contact with the slide guide 47.

[0006]

By the way, in such a bellows type pump, in order to increase the pump capacity, the number of folds of the folds 41A of the bellows 41 is increased to reduce the amount of expansion and contraction stroke of the bellows 41. Need to increase. However, in such a bellows 41, as a result of increasing the number of pleats in the pleats 41A, a waste volume in the bellows 41 becomes large, and the following problem occurs.

That is, for a certain bellows 41, a swash plate 50
Is moved away from the sliding guide 47, the volume of the pump chamber 51 in the bellows 41 is increased by the spring force of the bellows 41 itself, and the pressure in the pump chamber 51 is reduced. Accordingly, fuel flows from the suction port 52 to the fuel passage 5.
3, and is sucked into the pump chamber 51. However, if the dead volume in the bellows 41 is large, the pressure in the pump chamber 51 is hardly reduced, and the fuel is hardly sucked into the pump chamber 51. There is a problem that stable pump action cannot be performed.

For this reason, in order to reduce the dead volume in the bellows 41, a columnar member 54 is built in the bellows 41 as shown in FIG. The base end of the columnar member 54 is supported by a support plate 44 interposed between the cylinder 12 and the pump head 11. However, in order to more effectively reduce the waste volume described above, it is inevitable that the inner peripheral surface of the bellows 41 and the outer peripheral surface of the cylindrical member 54 have a structure closer to each other. The contact may cause the columnar member 54 to fall off, and the fold 41A of the bellows 41
Of the bellows 41 and the durability of the bellows 41 is reduced.

In view of the above-mentioned problems, the present invention is directed to a bellows pump in which a columnar member is provided in a bellows to reduce a waste volume. The contact between the bellows and the columnar member is reduced as much as possible to prevent the columnar member from falling,
It is an object of the present invention to provide a bellows type pump in which the durability of the bellows is improved.

[0010]

SUMMARY OF THE INVENTION For this reason, the invention according to claim 1 is a bellows pump in which a pump chamber is formed inside a plurality of bellows which can be extended and retracted, and each bellows is extended and contracted to perform a pumping operation. A columnar member for reducing the dead volume of the pump chamber inside the bellows is arranged and supported along the axial direction of the bellows, while the gap between the pleat between both ends of the bellows and the columnar member is formed. It is characterized in that it is larger than the gap between both ends of the bellows and the columnar member.

[0011] The invention according to claim 2 is that the length of the both ends of the columnar member at the both ends of the bellows in the direction orthogonal to the central axis of the bellows is set between the both ends of the columnar member at the folds of the bellows. The bellows at the substantially middle portion is formed to be longer than the length in the direction orthogonal to the central axis. Claim 3
According to the invention, the bellows and the columnar member are formed in a substantially cylindrical shape and a substantially columnar shape, respectively, and at both ends of the columnar member at both end positions of the bellows, a diameter of a substantially intermediate portion of the columnar member at the fold portion of the bellows. It is characterized in that a larger diameter portion is provided.

The invention according to claim 4 is characterized in that the substantially middle portion of the columnar member at the position of the fold portion of the bellows is formed in a substantially hollow shape in which the substantially middle portion in the axial direction is narrowed.
According to a fifth aspect of the present invention, in a bellows type pump in which a pump chamber is formed inside a plurality of bellows which can be extended and contracted, and each bellows is extended and contracted to perform a pumping operation, a dead volume of the pump chamber is reduced inside the bellows. While the columnar member for the bellows is disposed along the axial direction of the bellows, the gap between the bellows and the columnar member is formed so as to increase as the distance from the fixed end of the both ends of the bellows increases. I do.

The invention according to claim 6 is characterized in that a tapered surface is formed on the outer surface of the columnar member such that the gap between the bellows and the columnar member increases as the distance from the fixed end of the bellows increases. The invention according to claim 7 is that, between a columnar member support portion provided on the bellows fixed end portion side and a columnar member base end portion supported by the support portion, the central axis of the bellows of the columnar member is orthogonal to the central axis. And a play that allows movement in the direction of movement.

According to an eighth aspect of the present invention, in the columnar member, a concave portion communicating with a fluid suction passage and a discharge passage is provided on a bottom surface of a base end portion thereof, and the inside of the concave portion, the bellows and the columnar member are provided. A fluid passage communicating with a space between the fluid passages is provided. According to a ninth aspect of the present invention, the column-shaped member support portion provided on the bellows fixed end portion side includes a pedestal provided on a base end portion of the bellows, and a concave portion formed on the support portion supporting the pedestal. The base end of the columnar member is inserted into the concave portion to support the columnar member in a direction orthogonal to its central axis, and to support the columnar member in the central axis direction on the pedestal. It is characterized by having comprised in.

The operation of the present invention will be described. The invention according to claim 1 achieves the following operation by setting the gap between the columnar member and the fold of the bellows larger than the gap between the columnar member and both ends of the bellows. The bellows receives a free end of the bellows at one end of the columnar member at the time of shape deformation due to the vertical fluctuation of the internal pressure. Since the gap between the columnar member and the fold of the bellows is larger than the gap between the columnar member and both ends, the contact between the fold and the columnar member can be avoided as much as possible. The risk of the members falling off can be avoided as much as possible, and wear of the folds of the bellows can be suppressed, so that the durability can be improved.

Moreover, since the diameter of the columnar member is not particularly reduced but the diameter of only the portion corresponding to the fold is reduced, the waste volume can be reduced more effectively. In the invention according to claim 2, the length in the direction orthogonal to the central axis of the bellows at both ends of the columnar member at both ends of the bellows is set to substantially the intermediate portion between both ends of the columnar member at the folds of the bellows. Is formed longer than the length of the bellows in the direction orthogonal to the center axis, the gap between the columnar member and the fold of the bellows can be made larger than the gap between the columnar member and both ends of the bellows.

In the invention according to claim 3, when the bellows and the columnar member are formed in a substantially cylindrical shape and a substantially cylindrical shape, respectively, the columnar member and the bellows are provided by providing large diameter portions at both ends of the columnar member. The gap between the folds can be larger than the gap between the columnar member and both ends of the bellows. In the invention according to claim 4, the substantially middle portion of the columnar member at the position of the fold portion of the bellows is formed in a substantially wrapped shape in which the substantially middle portion in the axial direction is narrowed, so that the bellows increases and decreases its internal pressure. When the shape is repeatedly changed into a substantially barrel shape with a substantially middle portion bulging and a roughly gourd shape with a contraction at the time of shape deformation due to fluctuation, contact between the pleat portion and the columnar member can be avoided as much as possible.

In the invention according to claim 5, the gap between the bellows and the columnar member is formed so as to be farther away from the fixed end of the both ends of the bellows, so that even if the bellows is bent, The contact between the bellows and the columnar member can be prevented as much as possible. In the invention according to claim 6, the gap between the bellows and the columnar member is formed by forming a tapered surface on the outer surface of the columnar member such that the gap between the bellows and the columnar member increases as the distance from the fixed end of the bellows increases. Can be formed so as to be farther away from the fixed end of both ends of the bellows.

In the invention according to claim 7, the columnar member can move in the direction orthogonal to the central axis of the bellows in accordance with the movement of the bellows, and even if the bellows comes into contact with the columnar member, the columnar member falls off. Risk is reduced. In the invention according to claim 8, there is no need to provide a space between the columnar member and the end plate of the bellows, and the waste volume can be reduced more effectively.

According to the ninth aspect of the present invention, the support of the columnar member can be supported by the pedestal provided in the pump and the support portion for supporting the pedestal, and it is not necessary to newly provide a support part.

[0021]

As described above, according to the first aspect of the present invention, in a bellows pump in which a columnar member for reducing a waste volume is disposed in the bellows, the waste volume in the bellows is effectively reduced. Thus, the contact between the bellows and the columnar member can be minimized, and the columnar member can be prevented from falling off and the durability of the bellows can be improved.

According to the second and third aspects of the invention, the gap between the columnar member and both ends of the bellows can be made larger by changing the shape of the columnar member. According to the fourth aspect of the invention, the contact between the fold and the columnar member can be avoided as much as possible, and the columnar member can be prevented from falling off and the durability of the bellows can be more effectively improved.

According to the fifth aspect of the present invention, even if the bellows is bent, the contact between the bellows and the columnar member can be prevented as much as possible, and the columnar member can be prevented from falling off.
The durability of the bellows can be more effectively improved. According to the invention according to claim 6, by changing the shape of the columnar member, the gap between the bellows and the columnar member can be formed to be larger as the distance from the fixed end of the both ends of the bellows increases.

According to the seventh aspect of the present invention, it is possible to more effectively prevent the columnar member from falling off. According to the invention according to claim 8, the waste volume in the bellows can be reduced more effectively. According to the ninth aspect of the present invention, it is possible to easily support the columnar member with existing components without newly providing components, and to improve the manufacturability.

[0025]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. First, a fuel injection system for an internal combustion engine to which the bellows type pump according to the present invention is applied as a fuel pump will be described with reference to FIG. In this figure, fuel is pumped from a fuel tank 1 to a suction side of a fuel pump 4 by a feed pump 3 driven by an electric motor 2. The low pressure regulator 5 controls the fuel pump 4
Is maintained at a predetermined value.

The fuel pressurized by the fuel pump 4 is fed under pressure to the injector 6 through a high-pressure pipe, and is injected into the intake air of the internal combustion engine by the injector 6. The pressure in the high-pressure pipe on the discharge side of the fuel pump 4 is maintained at a predetermined value by the high-pressure regulator 7. Further, the inside of the casing of the fuel pump 4 and a return passage (low pressure) to the fuel tank 1 in the fuel piping system are communicated via a return oil passage 8, and a check valve 9 is connected to the return oil passage 8. Are connected.

The fuel pump 4 is fixed to an outer wall of a cylinder head of an internal combustion engine, and a rotary shaft of the fuel pump 4, which will be described later, is connected to an end of an intake camshaft by an axially free joint. Power is transmitted by the camshaft. Next, the configuration of the fuel pump 4 will be described in detail with reference to FIG. In FIG. 1, a pump head 11, a cylinder 12, and a casing 13 that define the outer shape of the fuel pump 4 are shown.
Are connected by bolts 15 and 16. A support plate 17 as a support and a check valve mounting plate 18 are sandwiched and fixed between the joint surfaces of the pump head 11 and the cylinder 12.

The cylinder 12 has three bellows storage holes 19 formed around its central axis. A cylindrical bellows 20 is accommodated in each bellows accommodation hole 19, and a sliding guide 21 is fitted slidably.
The bellows 20 includes a fold portion 20A formed in a cylindrical shape,
A disk-shaped end plate 22 that is welded to the tip (the upper end in FIG. 1) of the fold 20A and closes the tip of the fold 20A.
And a pedestal 23 welded to the base end (lower end in FIG. 1) of the fold, and a pump chamber 24 is formed therein.

The pedestal 23 of the bellows 20 has an opening 23A.
At the center of the ring. An annular stepped portion 12A is formed on the end surface of the cylinder 12 around the support plate 17 on the support plate 17 side by counterboring along the bellows storage hole 19, and each pedestal 23 has an outer periphery. With the end positioned inside the step 12A, the pump head 11 is pressed and fixed to the support plate 17 by the cylinder 12 fastened to the pump head 11 by bolts 16.

An annular groove 23B is formed on the abutment surface of the pedestal 23 with the support plate 17, and an O-ring 27 as a seal member mounted in the annular groove 23B abuts on the pedestal 23 and the support plate 17. Interposed between the surfaces prevents leakage of fuel to the outside of the pump chamber 24. In this fuel injection system, a feed pump is provided on the upstream side of the fuel pump 4, and pressure is constantly applied to the pump chamber 24 during operation.

The check valve mounting plate 18 is formed with a suction port 28 and a discharge port 29 for a fuel as a fluid which communicates with a concave portion of a cylindrical member described later. A suction check valve 30 is interposed, and a discharge port 29 is interposed with a discharge check valve 31. On the other hand, the sliding guide 21 is formed in a cap shape so as to cover an end (end plate 22) of the bellows 20,
The outer peripheral surface is slidably fitted in the bellows storage hole 19. The tip surface is formed in a spherical shape.

The end plate 22 of the bellows 20 is
1, and the flat surface thereof abuts on the inner surface of the sliding guide 21 at its tip end surface. The casing 13 rotatably supports a rotating shaft 34 on its central axis via a radial bearing 32. Reference numeral 33 denotes an oil seal provided between the casing 13 and the rotating shaft 34.

The rotating shaft 34 is connected to the camshaft at its outer end and rotates, but has a flange 3 at its inner end.
5 is formed. Here, the casing 13 of the flange portion 35
The side surface (upper surface in FIG. 1) is a thrust bearing 36
Are rotatably supported by the casing 13 via
The surface on the cylinder 12 side (the lower surface in FIG. 1) is inclined.

The inclined surface of the flange 35 of the rotating shaft 34 is configured to transmit a swinging motion to the three sliding guides 21 via the thrust bearing 37 and the swash plate 38. Thus, when the rotating shaft 34 (the flange 35) rotates, the thrust bearing 36 and the radial bearing 3
2, the rotation of the swash plate 38 is oscillated, that is, each part of the swash plate 38 is moved back and forth in the axial direction and transmitted to the slide guide 21, and the bellows 20 is expanded and contracted through this. It has become.

The rotation is interrupted by the thrust bearing 36 and the radial bearing 32 because the rotation shaft 3
This is to prevent the torsion caused by the rotation of 4 from being transmitted to the bellows 20. Here, inside the bellows 20, a columnar member 39 for reducing the waste volume of the pump chamber 24 is provided and supported along the axial direction of the bellows 20.

The end of the cylindrical member 39 at the end plate 22 position and the end of the pedestal 23 position are each formed to have a diameter larger than the diameter of a substantially intermediate portion of the cylindrical member 39 at the fold 20A. Large diameter portions 39A, 39B are provided, and large diameter portions 39A, 3B are provided at the base end of the columnar member 39 connected to the large diameter portion 39B.
A flange portion 39C having a larger diameter than that of 9B is provided.

A substantially middle portion of the columnar member 39 at the position of the fold 20A of the bellows 20 is formed in a substantially wrapped shape in which a substantially middle portion in the axial direction is narrowed. A concave portion 39D communicating with the suction port 28 and the discharge port 29 is provided on the bottom surface of the flange portion 39C of the cylindrical member 39. Further, the cylindrical member 39 has a concave portion 39D, a bellows 20, a cylindrical member 39, A fuel passage is provided as a fluid passage that communicates with a space between the two.

One end of the fuel passage is formed in the recess 39D.
A hole 39E communicating with the inside and extending along the central axis direction of the columnar member 39;
The cylindrical member 39 extends to both sides in a direction orthogonal to the central axis of
And a hole 39F opening on the outer peripheral surface. The columnar member 39 having the above-described configuration has the flange portion 39C inserted into the concave portion 17A formed in the support plate 17,
The pedestal 23 is fixed on the support plate 17 by the cylinder 12 fastened to the pump head 11 by the bolt 16, and is supported by the support plate 17.

That is, the cylindrical member 39 has its flange portion 39C inserted into the concave portion 17A of the support plate 17, and is supported in a direction perpendicular to its central axis. Support is provided. In this case, the outer peripheral surface of the flange portion 39C of the cylindrical member 39 and the concave portion 17 of the support plate 17 are formed.
It is preferable to provide a play between the inner peripheral surface A and the cylindrical member 39 to allow the bellows 20 to move in a direction perpendicular to the central axis of the bellows 20.

With the columnar member 39 thus supported, one large diameter portion 39A of the columnar member 39 is located inside the end plate 22 of the bellows 20, and the other large diameter portion 39B
Is located inside the pedestal 23, and a substantially intermediate portion between the large diameter portions 39A and 39B is located inside the fold portion 20A. The gap between the columnar member 39 disposed in the bellows 20 and the fold 20A as described above is determined by the columnar member 39, the end plate 22, and the pedestal 2.
3 is set larger than the gap.

In a state where the columnar member 39 is supported, the concave portion 39D of the flange portion 39C of the columnar member 39 is provided.
Communicates with the suction port 28 and the discharge port 29 of the check valve mounting plate 18. Next, the operation of such a configuration will be described. When the rotary shaft 34 is rotated by the camshaft of the internal combustion engine via the joint, the swash plate 38 is supported by being inclined with respect to the rotary shaft 34. The bellows 20 is extended / contracted through the sliding guide 21 of FIG.

Here, with respect to a certain bellows 20, the swash plate 3
8 moves in a direction away from the sliding guide 21,
The volume of the pump chamber 24 increases due to the spring force of the bellows 20 itself, and the pressure in the pump chamber 24 decreases. Along with this, fuel flows from the suction port 28 to the recess 39D, the hole 39E,
It is guided through the hole 39F and is sucked into the pump chamber 24.
When the swash plate 38 moves toward the slide guide 21 and presses it, the bellows 20 is compressed, the volume of the pump chamber 24 is reduced, and the pressure in the pump chamber 24 increases. Along with this, the fuel reaches the discharge port 29 via the holes 39F, the holes 39E and the concave portions 39D, and is discharged.

Here, in the fuel pump 4 having such a configuration, the gap between the cylindrical member 39 and the fold 20A of the bellows 20 is larger than the gap between the cylindrical member 39 and the end plate 22 of the bellows 20 and the pedestal 23. By setting it to be large, the following operation is achieved. Fig. 1 (A), bellows 2
This shows the shape of the bellows 20 when the zero internal pressure is the atmospheric pressure, and the bellows 20 has a substantially gourd shape in which a substantially middle portion in the axial direction is narrowed.

FIG. 2 shows the shape of the bellows 20 when the internal pressure of the bellows 20 is increased.
Has a substantially barrel shape in which a substantially middle portion in the axial direction swells. That is, the bellows 20 receives the end plate 22 of the bellows 20 at the large-diameter portion 39A of the cylindrical member 39 when the bellows 20 is deformed due to the vertical fluctuation of the internal pressure, as shown in FIGS. 1A and 2. The shape changes repeatedly between a barrel and a gourd,
Since the gap between the cylindrical member 39 and the fold 20A of the bellows 20 is larger than the gap between the cylindrical member 39, the end plate 22, and the pedestal 23, the contact between the fold 20A and the cylindrical member 39 is avoided as much as possible. It is possible to minimize the possibility that the cylindrical member 39 will fall off,
The wear and the like of the fold 20A can be suppressed, and the durability can be improved.

Further, since the diameter of only the portion corresponding to the fold portion 20A is particularly reduced without reducing the overall diameter of the columnar member 39, the waste volume can be reduced more effectively. In particular, according to the above-described embodiment, the substantially middle portion of the columnar member 39 at the position of the fold portion 20A of the bellows 20 is formed in a substantially wrapped shape in which the substantially middle portion in the axial direction is narrowed. The contact between the folds and the columnar members can be more effectively suppressed in response to the repetitive shape change between the barrel shape and the approximately gourd shape.

According to the above embodiment, the outer peripheral surface of the flange portion 39C of the cylindrical member 39 and the concave portion 17 of the support plate 17 are formed.
A clearance is provided between the inner peripheral surface of the bellows A and the cylindrical member 39 to allow the bellows 20 to move in a direction perpendicular to the central axis of the bellows 20. The bellows 20 can move in a direction perpendicular to the central axis of the cylindrical member 20, and even if the bellows 20 and the cylindrical member 39 come into contact with each other, the possibility that the cylindrical member 39 falls off is reduced.

Further, the fuel passage for communicating the pump chamber 24 with the suction port 28 and the discharge port 29 is formed with the cylindrical member 3.
9, the recess 39D formed in the flange 39C and the holes 39E and 39F formed in the columnar member 39. Therefore, as shown in FIG.
There is no need to provide a space between the end plate 9 and the end plate 22 of the bellows 20, and the columnar member 39 can be brought as close to the end plate 22 as possible. As a result, the dead volume can be reduced more effectively. .

The flange 39C at the base end of the columnar member 39 is inserted into a recess 17A formed in the support plate 17 to support the columnar member 39 in a direction perpendicular to its central axis. Since the cylindrical member 39 is supported by the pedestal 23 in the central axis direction, the support of the cylindrical member 39 can be supported by a component provided in the pump in advance, and a new supporting component is provided. Since there is no need, manufacturability can be improved.

In the above embodiment, the large-diameter portions 39A and 39B are provided at both ends of the cylindrical member 39, and the cylindrical member 39 at the position of the fold 20A of the bellows 20 is provided.
The intermediate portion of the cylindrical member 39 at the position of the fold 20A of the bellows 20 has a uniform diameter along the central axis direction, as shown in FIG. May be used as a simple columnar shape.

The invention is not limited to these. In short, the length in the direction orthogonal to the central axis of the bellows at both ends of the bellows at both ends of the bellows is determined by the length of the columnar member at the pleat position between both ends of the bellows. The gap between the cylindrical member and the fold of the bellows is formed longer than the length of the portion between both ends in the direction orthogonal to the center axis of the bellows, and the gap between the cylindrical member and the bellows at both ends (end plate and pedestal) Should be larger than the gap.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the gap between the bellows 20 and the columnar member 40 is formed to be larger as the distance from the fixed end of the both ends of the bellows 20 increases. Is formed in a substantially conical shape having a tapered surface (conical surface) on its outer surface such that a gap between the bellows 20 and the columnar member 40 increases as the distance from the fixed end of the bellows 20 increases.

In this case, the bellows 20 of the columnar member 40
A large-diameter portion 40B is formed at an end corresponding to the pedestal 23, and a flange 40C is formed at a base end. According to this embodiment, as shown in FIG. 4, even if the bellows 20 is bent, contact between the bellows 20 and the columnar member 40 can be prevented as much as possible.

The clearance C between the outermost peripheral surface of the columnar member 40 and the inner peripheral surface of the end plate 22 shown in FIG. 5 is used to prevent the contact between the bellows 20 and the columnar member 40 as much as possible.
It is preferable to set as follows. That is, the clearance between the outer peripheral surface of the end plate 22 and the inner peripheral surface of the slide guide 21 is A,
When the clearance between the outer peripheral surface of the sliding guide 21 and the inner peripheral surface of the bellows storage hole 19 is B, the clearance C between the outermost peripheral surface of the cylindrical member 40 and the inner peripheral surface of the end plate is C ≧ A +
B.

By setting the clearance C in this manner, the outer peripheral surface of the sliding guide 21 is
Even when the outer peripheral surface of the end plate 22 contacts the inner peripheral surface of the slide guide 21, the cylindrical member 40 does not contact the end plate 22, and the contact between the bellows 20 and the cylindrical member 40 is more effectively achieved. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a bellows type pump according to the present invention, wherein (A) is a front sectional view, and (B) is a plan view of a cylinder.

FIG. 2 is a front sectional view of one embodiment of the bellows pump according to the first embodiment;

FIG. 3 is a front sectional view showing another embodiment.

FIG. 4 is a front sectional view showing still another embodiment.

FIG. 5 is an enlarged cross-sectional view showing a relationship among a cylindrical member, an end plate, a sliding guide, and a cylinder in the embodiment.

FIG. 6 is a diagram illustrating a fuel injection system of an internal combustion engine in which the bellows type pump according to the present invention is used as a fuel pump.

FIG. 7 is a front sectional view showing a configuration of a conventional bellows pump.

[Explanation of symbols]

 Reference Signs List 4 fuel pump 11 pump head 12 cylinder 13 casing 17 support plate 19 bellows storage hole 20 bellows 20A fold 21 sliding guide 22 end plate 23 pedestal 24 pump chamber 28 suction port 29 discharge port 39 cylindrical member 39A, 39B large diameter portion 39C Flange 39D Recess 39E, 39F Hole 40 Columnar member

Claims (9)

[Claims] 1. A bellows-type pump in which a pump chamber is formed inside a plurality of bellows which can be extended and retracted, and each bellows is operated to extend and contract to perform a pumping operation. While the member is arranged and supported along the axial direction of the bellows, the gap between the pleat between both ends of the bellows and the columnar member is made larger than the gap between both ends of the bellows and the columnar member. Bellows pump. 2. The length of a direction perpendicular to the central axis of the bellows at both ends of the columnar member at the both ends of the bellows is set to the length of the bellows at a substantially intermediate portion between both ends of the columnar member at the folds of the bellows. The bellows type pump according to claim 1, wherein the length is formed to be longer than a length in a direction orthogonal to the central axis. 3. The bellows and the columnar member are formed in a substantially cylindrical shape and a substantially columnar shape, respectively, and a diameter of a substantially intermediate portion of the columnar member at a position of a fold of the bellows is provided at both ends of the columnar member at both ends of the bellows. The bellows type pump according to claim 2, wherein a larger diameter portion is provided. 4. The bellows type pump according to claim 3, wherein a substantially middle portion of the columnar member at the position of the fold of the bellows is formed in a substantially hollow shape in which a substantially middle portion in the axial direction is narrowed. . 5. A bellows type pump in which a pump chamber is formed inside a plurality of bellows which can be extended and retracted, and each bellows is operated to extend and contract to perform a pumping operation. The bellows type wherein the member is arranged along the axial direction of the bellows, and the gap between the bellows and the columnar member is formed so as to be farther away from the fixed end of both ends of the bellows. pump. 6. A bellows type pump according to claim 5, wherein a tapered surface is formed on an outer surface of said columnar member such that a gap between said bellows and said columnar member increases as a distance from a fixed end of said bellows increases. . 7. A columnar member supporting portion provided on the bellows fixed end portion side, and a columnar member base end portion supported by the supporting portion, in a direction perpendicular to a central axis of the bellows of the columnar member. The bellows type pump according to any one of claims 1 to 6, further comprising a play allowing movement. 8. The columnar member is provided with a concave portion communicating with a fluid suction passage and a discharge passage on a bottom surface of a base end portion thereof, and a space between the bellows and the columnar member is formed in the concave portion. The fluid passage which communicates was provided, The claim 1 characterized by the above-mentioned.
8. The bellows pump according to any one of 7 above. 9. A pedestal provided at a base end of a bellows, wherein a columnar member supporting portion provided at the bellows fixed end side is provided.
A concave portion formed in a support portion supporting the pedestal, and a base end portion of the columnar member is inserted into the concave portion to support the columnar member in a direction orthogonal to its central axis, and The bellows type pump according to any one of claims 1 to 8, wherein the pedestal is configured to support the columnar member in the center axis direction thereof.