JPH1061557A - Bellows pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of twist stress on a bellows so as to prevent reduction of fatigue strength by forming a projection surface part on at least one side of the inner end surface of a guide or a bellows crest part, and abutting them on each other by point contact. SOLUTION: A disk shim 31 is interposed between a bellows crest part 21 and a guide 18. A spherical projection surface part 31a is formed on only one surface of the shim 31, and abuts on a guide inner end surface 18a. The back surface part 31b of the shim 31 is brought into contact with the crest surface of the crest part 21 at a flat surface. Since the guide inner end surface 18a and the shim projection surface part 31a are brought into point contact with each other, rotation of the guide 18 is not transmitted to the bellows crest part 21 even if the guide 18 is rotated by eccentric force from reciprocation driving means by a cam, a wash plate, and the like. Since twist stress is not generated on a bellows main body 20, it is possible to prevent reduction of fatigue strength of the bellows main body 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a bellows type pump.

[0002]

2. Description of the Related Art A bellows pump has been proposed as a pump suitable for applications requiring high pressure, such as a fuel injection pump for a direct injection internal combustion engine. This uses a bellows with a sealed structure as a pump chamber to suck and compress fuel by expansion and contraction, so that there is no leakage compared to a cylinder structure such as a piston or plunger, and high pressure can be obtained efficiently. There is a feature.

As a mechanism, a mechanism having a structure in which a bellows attached to a pump housing is reciprocated through driving means such as a cam and a swash plate is generally used. The bellows is not driven directly by a cam or the like, but a cylindrical guide with a bottom is slidably fitted into the insertion hole that houses the bellows, and the swash plate or cam is brought into contact with the head of this guide to indirectly connect it. The bellows is pushed in a specific manner (see, for example, Japanese Patent Application Laid-Open No. 4-191461 as a known document of this type of pump).

[0004]

However, in such a bellows type pump, there is a problem that the fatigue strength of the bellows may be reduced due to the action of the rotational force from the guide and the shape error of the bellows itself. There is.

That is, if the center of the frictional force acting on the contact portion with the swash plate or the cam is slightly eccentric with respect to the guide center, the guide rotates due to the frictional force. At this time, the crown at the tip of the bellows and the inner end face of the guide abutting on the crown are flat and in surface contact with each other, so that the frictional force between them is large. receive. The stress caused by the action of the torsion is added to the stress caused by the expansion and contraction of the bellows, thereby impairing the fatigue strength of the bellows. The solution to this problem is to increase the outer diameter of the bellows in consideration of the elasticity required of the bellows. However, in that case, there is a problem that the pump becomes large.

On the other hand, the bellows has a structure in which a crown portion and a base end portion are welded to the front and rear of the bellows-shaped main body, respectively. Therefore, an error in assembly at the time of welding or a shape error of the bellows itself is caused. The bellows may have some bends or inclinations. If there is such a bend or inclination, when the compressive force acts from the guide, the contact surfaces try to come into close contact with each other, so that a bias stress is generated in the bellows, thereby impairing the fatigue strength. In order to solve this problem, it is conceivable to increase the assembly and shape accuracy of the bellows. However, an increase in cost is inevitable in order to satisfy the required and sufficient accuracy requirements.

An object of the present invention is to solve such a conventional problem.

[0008]

According to a first aspect of the present invention, a bellows constituting a pump chamber is inserted into a bellows insertion hole of a pump housing, and a base end of the bellows is fixed to the pump housing side. The bellows crown is brought into contact with the inner end surface of the bottomed cylindrical guide slidably fitted, and the bellows is extended and contracted by reciprocating the guide via reciprocating drive means connected to the head. In the bellows type pump configured as described above, a convex portion is formed on at least one of the inner end face of the guide and the bellows crown, and the inner face of the guide and the bellows crown are brought into contact with each other by point contact.

[0009] The second invention is the above-mentioned first invention, wherein:
The guide inner end face or the bellows crown portion that comes into contact with the convex portion is formed into a concave shape having a larger radius of curvature than the convex portion.

According to a third aspect of the present invention, in the above inventions, the convex portion is formed on a shim interposed between the bellows and the guide.

According to a fourth aspect of the present invention, the bellows crown is formed so as to be fitted to the inner peripheral surface of the guide in each of the above inventions.

According to a fifth aspect of the present invention, in the third or fourth aspect, the shim is formed such that a convex portion is formed in contact with the guide inner end face, and a bellows is provided between the bellows crown and the shim. A fitting portion for restraining the shim from moving in the radial direction with respect to the crown portion is formed.

[0013] In a sixth aspect based on the fifth aspect,
The shim was formed so as to fit on the inner peripheral surface of the guide.

In a seventh aspect based on the first to fourth aspects, the convex portion is formed so as to face the bellows crown.

According to an eighth aspect based on the seventh aspect,
The bellows crown portion was provided with a flat shim made of a material having a higher hardness than the bellows crown portion at least at a portion abutting on the convex portion from the guide side.

According to a ninth aspect of the present invention, a bellows constituting a pump chamber is inserted into a bellows insertion hole of a pump housing, a base end of the bellows is fixed to the pump housing side, and is slidably fitted in the bellows insertion hole. A bellows pump in which the crown of the bellows is brought into contact with the inner end surface of the bottomed cylindrical guide, and the guide is reciprocated through reciprocating drive means connected to the head thereof, so that the bellows is expanded and contracted. In the above, a recess having a predetermined depth is formed in the bellows crown toward the base end of the bellows, and the bellows and the guide are connected via a push rod housed in the recess.

In a tenth aspect based on the ninth aspect, the guide and the abutting portion of the bellows recess with the push rod are each formed as a spherical surface.

In an eleventh aspect based on the tenth aspect, the radius of curvature of the end of the push rod abutting on the bellows recess is smaller than that of the end of the push rod abutting on the guide.

[0019]

According to the first and second aspects of the present invention, the inner end face of the guide and the bellows crown come into contact with each other in a very limited area of point contact with a convex or spherical surface. Even if the guide rotates due to the eccentric force from the reciprocating drive means having the swash plate, the rotation is not transmitted to the bellows, and therefore, no torsional stress is generated in the bellows. . Further, since the contact is made on a spherical surface, the bellows and the guide come into contact with each other at the center of each other irrespective of the inclination of the bellows crown and the bending of the bellows main body. As a result, a reduction in the fatigue strength of the bellows is avoided, and its reliability is improved.

According to the second aspect of the present invention, the centering action of urging the other convex portion toward the center position can be obtained by the concave shape formed on one of the guide inner end surface and the bellows crown.
For example, it is possible to avoid the inconvenience that the crown of the bellows is eccentrically inclined when the guide is inclined.

According to the third aspect of the present invention, since the convex portion which is easily worn is formed in the shim, the crown of the guide and the bellows can be easily formed of a material having relatively good workability. In particular, since the bellows is generally configured such that its crown is welded to the cylindrical bellows main body, there is a problem that when a high-hardness material is applied to the crown, the material is likely to deteriorate due to heat during welding. The use of the shim eliminates the need for applying a high-hardness material to the crown, and facilitates welding.

According to the fourth aspect of the present invention, since the bellows crown is positioned in the radial direction of the inner circumferential surface of the guide, even if the guide is tilted, the crown acts by the radial acting force at the point contact portion. No eccentricity causes the bellows to bend.

According to the fifth aspect, the third or fourth aspect is provided.
According to the invention, since the shim is positioned in the radial direction by the fitting portion with the bellows crown, the shape can be simplified and downsized, and the workability and cost can be improved.

According to the sixth aspect, in the fifth aspect, the shim fitted to the bellows crown portion and positioned in the radial direction prevents eccentricity of the shim and the bellows. The bellows can be prevented from bending.

According to the seventh aspect, since the convex portion is formed toward the bellows crown portion, even if the bellows is bent or inclined, the guide presses the bellows from the direction of the bent or inclined. Therefore, there is no occurrence of biased stress due to the action of correcting the bend and inclination of the bellows when the bellows and the guide come into planar contact, thereby avoiding a decrease in the fatigue strength of the bellows and further increasing durability. And reliability are improved.

According to the eighth invention, in the above-mentioned seventh invention, only the portion which comes into contact with the convex portion from the guide inner end surface side by point contact is formed by a plane shim made of a high-hardness material. The size and cost of the shim can be reduced.

According to the ninth aspect, the acting force from the guide when the bellows is driven in the compression direction is transmitted to the concave portion of the bellows crown via the push rod. The recess is located a predetermined amount deeper on the base end side than the bellows crown, that is, the load point on the bellows is closer to the base end side, so that the deviation of the load vector from the bellows center is smaller. Therefore, eccentricity and buckling of the bellows can be reliably avoided.

According to the tenth aspect, in the ninth aspect, the contact portions of the guide and the bellows recess with the push rod are each formed as a spherical surface. Is automatically centered,
The displacement can be reliably prevented.

According to the eleventh aspect, in the tenth aspect, since the radius of curvature of the end portion of the push rod abutting on the bellows recess is relatively small, the alignment sensitivity is high, and therefore, the displacement of the load point can be more reliably achieved. Can be prevented. Also,
It is possible to reduce the inertial mass of the lower end of the push rod on the swing end side. On the other hand, since the radius of curvature of the end of the push rod on the guide side is relatively large and the alignment sensitivity is relatively weak, the vibration of the guide is suppressed from acting on the push rod. Can be further prevented.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will now be described with reference to the drawings. First, FIG. 1 shows an example of a bellows type fuel pump to which the present invention can be applied.
In the figure, 1 is a pump body, 2 is a pump drive shaft, and 3 is a bellows. The pump body 1 includes a first pump housing 4 supporting a drive shaft 2, a second pump housing 5 containing a bellows 3 therein, and these housings 4, 5 sequentially coaxially with bolts 6, 7. It comprises a valve housing 8 and a cover plate 9 to be tightened.

The drive shaft 2 is rotatably supported by a first pump housing 4 via a radial bearing 10 and is connected to a camshaft of an engine (not shown) and driven to rotate. In order to support a reaction force from a bellows 3 which will be described later, a flange portion 12 is provided on the inner end surface of the housing 4 via a thrust bearing 11 so as to be relatively rotatable.
Is provided. The end surface of the flange portion 12 is inclined at a predetermined angle, and a swash plate 15 is supported via a radial bearing 14 on a support shaft portion 13 projecting vertically from the inclined surface. A thrust bearing 16 is interposed between the swash plate 15 and the flange portion 12 so that the swash plate 15 can be relatively rotated with respect to the flange portion 12 of the drive shaft while a reaction force from the bellows 2 is acting. I have.

A second pump housing 5 is housed inside the pump housing 4 so as to face the drive shaft flange 12. A plurality of, for example, three bellows insertion holes 17 are formed in the pump housing 5 so as to penetrate in the axial direction so as to surround the rotation center line of the drive shaft 2 in parallel with the center line (FIG. Shows only one).

A cylindrical guide 18 having a bottom and a bellows 3 are inserted into the bellows insertion holes 17, respectively. The guide 18 is fitted slidably in the axial direction with respect to the insertion hole 17, and its spherical outer end face is brought into contact with the end face of the swash plate 15 by elastic force from the bellows 3. ing.

The bellows 3 has a bellows body 20 formed in a hollow cylindrical shape as a whole, a crown 21 welded to close one end thereof, and an annular base end welded to the other end. 22. Insert bellows 3 into insertion hole 1
7, the crown 21 has its distal end abutting on the inner end surface of the guide 18, while its proximal end 22 is oil-tightly seated on the valve housing 8 via a seal ring 23. Thereby, a pump chamber 24 is defined between the pump chamber 24 and the valve housing 8.

The valve housing 8 is provided with a suction passage 27 and a discharge passage 28 provided with a suction check valve 25 and a discharge check valve 26 respectively so as to face the pump chamber 24 within the opening of the bellows base end 22. Have been. The suction passage 27 and the discharge passage 28 communicate with a suction port 29 and a discharge port 30 formed in the cover plate 9, respectively. The suction port 29 is supplied with relatively low-pressure fuel from a feed pump, and the discharge port 30 is connected to a fuel injection nozzle via a pressure regulating valve or the like.

The fuel pumping action by the fuel pump is performed as follows. As the drive shaft 2 rotates, the swash plate 15
Deflects on the flange 12, thereby causing the swash plate 15
Reciprocating at the contact portion with the guide 18. Guide 18
Is constantly pressed against the swash plate 15 by the elastic force of the bellows 3, so that the bellows 3 expands and contracts in the axial direction with the reciprocating movement. That is, the bellows 3 is compressed by the swash plate 15 pushing the guide 18, and when the swash plate 15 tries to separate from the guide 18, the bellows 3 is extended by its own elastic force and follows the swash plate 15 together with the guide 18.

With the expansion and contraction of the bellows 3,
As the bellows 3 extends, the pump chamber 24 expands and the pressure decreases, so that the fuel from the suction port 29 opens the suction check valve 25 and is sucked into the pump chamber 24. When the bellows 3 is compressed, the pump chamber 24 contracts and becomes high pressure, so that the discharge check valve 26 is opened and the high pressure fuel is sent out to the discharge port 30. Such suction and discharge operations are sequentially performed by the plurality of bellows 3, whereby high-pressure fuel is supplied substantially continuously to the injection nozzle side.

Although the bellows 3 is driven by the swash plate 15 in this example, other means for driving the bellows include, for example, one in which the guide 18 is driven by an eccentric cam.

When the bellows 3 is driven reciprocally by the swash plate or the cam, as described above, the guide 1 may be eccentric due to the eccentricity of the contact friction center between the guide 18 and the swash plate or the cam.
8 may be affected by rotational force. At this time, if the bellows crown 21 and the inner end surface of the guide 18 are in surface contact with each other as shown in FIG. 1, the rotational force of the guide 18 is transmitted to the bellows 3 almost as it is, so that durability is reduced. Is not preferred. Further, if the bellows 3 is bent, the bellows 3 receives a force in a direction for forcing the bending at the surface contact portion, which is also not preferable in terms of durability.

The gist of the present invention is to solve such a problem by bringing the bellows 3 and the guide 18 into contact with each other by point contact. A specific example thereof will be described below with reference to FIGS. A description will be given based on the illustrated embodiment of the bellows. 2 and the following figures, parts corresponding to those in FIG. 1 or parts corresponding to each other in the respective drawings are denoted by common reference numerals. That is, reference numeral 18 denotes a guide, and 20 to 22 denote a main body, a crown, and a base end of the bellows, respectively. Reference numeral 31 or 32 denotes a shim.

In FIG. 2, a disk-shaped shim 31 is interposed between the bellows crown 21 and the guide 18 as shown. In this case, a spherical convex surface portion 31a is formed only on one surface of the shim 31, the convex surface portion 31a is brought into contact with the guide inner end surface 18a, and the back surface portion 31b of the shim 31 is a crown surface 21a of the crown portion 21. In a plane. According to this configuration, since the guide inner end surface 18a and the shim convex portion 31a are in point contact with each other, the guide 18 may rotate due to the eccentric force from the reciprocating drive means such as a cam or a swash plate. , Its rotation is bellows crown 21
To the bellows body 20
No torsional stress is generated. Further, even when the bellows crown 21 is inclined or the bellows body 20 is bent due to an assembly error or a shape error at the time of welding, the convex surface 31 of the shim 31 seated on the bellows crown 21.
a and the guide inner end surface 18a are in contact with each other at the center thereof, so that there is no generation of biased stress due to the above-mentioned inclination or bending. Therefore, the fatigue strength of the bellows body 20 is not impaired.

In this example, the convex portion is provided on the shim 31, but it may be formed on the crown surface 21a of the bellows crown portion 21. However, by forming the shim 31 separately from the bellows, there is an advantage that a material having high hardness that can withstand high surface pressure due to point contact can be easily applied. That is, since the bellows crown 21 is joined to the bellows main body 20 by welding as described above, if a high-hardness material is used for the crown 21, the material deteriorates at a high temperature during welding and the hardness is impaired. May be Sim 3
By adopting the configuration provided with 1, it is possible to avoid such a problem and ensure durability.

In the configuration shown in FIG. 2, the shim 31 and the bellows crown 21 are fitted to the inner peripheral surface of the guide 18. If the inner end face 18a of the guide 18 is inclined with respect to the central axis due to wear or shape error, the bellows crown 21 is displaced in the radial direction by a radial load vector generated due to the inclination during compression. This may cause bending when the bellows is compressed. According to the fitting structure, such a problem can be prevented and the bellows can always be compressed in a straight direction.

In order to obtain such an effect, as shown in FIG. 3 or FIG.
Only one of them may be fitted to the inner peripheral surface of the guide 18. That is, in FIG. 3, only the shim 31 is formed to have an outer diameter that fits into the guide 18, and the concave fitting portion 2 formed at the center of the fitting surface of the bellows crown 21 is formed.
1b and a convex fitting portion 31c formed at the center of the back surface of the shim 31 so as to correspond thereto, and the shim 31 is radiused with respect to the bellows crown portion 21 at the fitting portion. Positioning in the direction prevents the bellows from bending. 4, only the bellows crown 21 is formed to have an outer diameter that fits into the inner peripheral surface of the guide 18, and the shim 31 itself is fitted to the fitting portion 21b of the bellows crown 21.
The bellows crown 21 is used for positioning in the radial direction. FIG. 3 is advantageous in that the bellows crown 21 does not wear due to contact with the guide 18. On the other hand, the one shown in FIG. 4 is advantageous in terms of workability and cost since the shim 31 is small and simple in shape.

FIG. 5 shows the shape of the inner end surface 18a of the guide 18 formed as a concave spherical surface having a larger radius of curvature than the convex surface portion 31a of the shim 31. According to this configuration, when a compressive load is applied to the guide 18, a load vector in a direction in which the convex portion 31a is biased toward the center position of the inner end surface 18a by the concave shape of the inner end surface 18a is obtained. Therefore, it is possible to avoid such a disadvantage that the bellows crown portion 21 is eccentric when the guide 18 is inclined by the centering action.

FIG. 6 to FIG. 8 show a configuration in which the convex portion is formed toward the bellows crown 21 so that the bellows crown 21 and the convex portion are in point contact with each other. That is,
6 or 7, a spherical convex portion 31a is formed on the surface of the shim 31 interposed between the bellows crown 21 and the guide inner end surface 18a on the side facing the bellows crown 21. . In FIG. 8, the inner end surface 18a of the guide 18 itself is a spherical convex surface. In any case, a concave fitting portion 21b is formed at the center of the crown surface of the bellows crown portion 21, and a flat shim 32 made of a high-hardness material is fitted into the fitting portion 21b. Durability is improved by performing point contact with the convex portion.

According to the above configuration, as shown in FIG. 7 or FIG. 8, even if the bellows main body 20 has an inclination s with respect to the center axis due to a shape error thereof, the guide 18 can be straightened from the direction of the inclination. The bellows will be pushed and therefore the bellows crown 21 and the guide inner end face 18
There is no generation of partial stress due to the action of correcting the bending or inclination of the bellows when a is in planar contact, and therefore, it is possible to avoid a decrease in the fatigue strength of the bellows and improve the durability and reliability.

FIG. 9 shows that a recess 33 having a predetermined depth is formed in the center of the bellows crown 21 toward the base end 22, and the push rod 34 is accommodated in the recess 33. The compression force from the guide 18 is transmitted to the bellows crown 21. With this configuration, since the load input point with respect to the concave portion 33 is deviated toward the base end portion 22 with respect to the bellows crown 21, the deviation of the load vector from the center of the bellows is reduced, and therefore, the bellows body 20 eccentricity and buckling can be avoided more reliably.

In the configuration shown in FIG. 9, both ends 34a and 34b of the push rod 34 are formed in a spherical shape as shown in the figure, and the center of the inner end surface of the guide 18 corresponding to the spherical ends 34a and 34b. A concave spherical receiving portion 33a, 18d is formed at the deepest portion of the concave portion 33, and these are brought into spherical contact with each other. In this case, the load points at the push rod both end portions 34a and 34b are automatically aligned, and the displacement can be more reliably prevented. Further, the push rod 34 has a concave portion 33 in comparison with the radius of curvature of the end portion 34 a on the side that contacts the guide 18.
The radius of curvature of the end 34b on the side in contact with is reduced. In this way, the centering sensitivity can be enhanced by the end 34b having a small radius of curvature, and the inertial mass of the end 34b on the swing end side can be reduced. On the other hand, since the radius of curvature of the push rod end 34a on the guide 18 side is relatively large and the alignment sensitivity is relatively low, the guide 18
Is suppressed from acting on the push rod 34,
Thereby, the effect of the unbalanced load on the bellows main body 20 can be better prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a bellows type pump to which the present invention is applied.

FIG. 2 is a longitudinal sectional view of the first embodiment of the bellows according to the present invention.

FIG. 3 is a longitudinal sectional view of a bellows according to a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a third embodiment of the bellows according to the present invention.

FIG. 5 is a longitudinal sectional view of a fourth embodiment of the bellows according to the present invention.

FIG. 6 is a longitudinal sectional view of a fifth embodiment of the bellows according to the present invention.

FIG. 7 is a longitudinal sectional view for explaining the operation of the bellows in FIG. 6;

FIG. 8 is a longitudinal sectional view of a sixth embodiment of the bellows according to the present invention.

FIG. 9 is a longitudinal sectional view of a bellows according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump main body 2 Pump drive shaft 3 Bellows 4 1st pump housing 5 2nd pump housing 8 Valve housing 9 Cover plate 12 Flange part of pump shaft 15 Swash plate 17 Bellows insertion hole 18 Guide 18a Guide inner end face 20 Bellows main body 21 Bellows crown 21a Bellows crown 21b Fitting part 22 Bellows base end 24 Pump chamber 25 Suction check valve 26 Discharge check valve 31 Shim 31a Spherical convex part 31c Fitting part 32 Flat shim 33 Concavity in bellows crown 34 Push rod

Claims (11)

[Claims] A bottomed cylinder in which a bellows constituting a pump chamber is inserted into a bellows insertion hole of a pump housing, a base end of the bellows is fixed to the pump housing side, and is slidably fitted in the bellows insertion hole. A bellows type pump, wherein a bellows crown is brought into contact with an inner end face of a shaped guide, and the guide is reciprocated through reciprocating drive means connected to the head thereof to expand and contract the bellows. A bellows type pump, wherein a convex surface is formed on at least one of the inner end surface and the bellows crown portion, and the guide inner end surface and the bellows crown portion are brought into contact with each other by point contact. 2. The bellows type pump according to claim 1, wherein the guide inner end surface or the bellows crown portion which comes into contact with the convex portion is formed in a concave shape having a larger radius of curvature than the convex portion. 3. The shim interposed between the bellows and the guide, wherein the convex portion is formed.
A bellows type pump according to claim 2. 4. The bellows type pump according to claim 1, wherein the bellows crown portion is formed so as to be fitted to the inner peripheral surface of the guide. 5. The shim has a convex surface portion abutting on the inner end surface of the guide, and a gap between the bellows crown portion and the shim.
5. The bellows type pump according to claim 3, wherein a fitting portion for restricting movement of the shim with respect to the bellows crown portion in a radial direction is formed. 6. The bellows type pump according to claim 5, wherein the shim is formed so as to fit on the inner peripheral surface of the guide. 7. The bellows pump according to claim 1, wherein the convex portion is formed toward the bellows crown. 8. The bellows crown portion is provided with a flat shim made of a material having a higher hardness than the bellows crown portion, at least at a portion abutting on the convex portion from the guide side. The bellows pump described. 9. A bottomed cylinder in which a bellows constituting a pump chamber is inserted into a bellows insertion hole of a pump housing, a base end of the bellows is fixed to the pump housing side, and is slidably fitted in the bellows insertion hole. A bellows type pump configured to abut a crown portion of a bellows on the inner end surface of a shaped guide and reciprocate the guide via reciprocating drive means connected to the head thereof to expand and contract the bellows. A bellows type pump, wherein a concave portion having a predetermined depth is formed in a portion toward a base end portion of the bellows, and the bellows and the guide are connected via a push rod accommodated in the concave portion. 10. The bellows type pump according to claim 9, wherein the guide and the contact portion of the bellows recess with the push rod are each formed in a spherical surface. 11. The bellows type pump according to claim 10, wherein a radius of curvature of an end of the push rod abutting on the bellows recess is smaller than that of an end of the push rod abutting on the guide.