GB2097066A

GB2097066A - A diaphragm pump

Info

Publication number: GB2097066A
Application number: GB8209356A
Authority: GB
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1981-03-31
Filing date: 1982-03-30
Publication date: 1982-10-27
Also published as: DE3209252A1; IT8253128V0; ES510981A0; FR2503265A1; GB2097066B; IT1155474B; IT8267414A0; ES8303620A1

Abstract

To increase the discharge capacity of a diaphragm pump, particularly for high pumping frequencies, the volume of its suction chamber 19 is larger than that of the pressure chamber (21) preferably 3 times as large as described the pumps housing (1) is made of plastics material and comprises an inlet port (23) for the suction chamber (19) and an outlet port (25) for the pressure chamber (21). One or several non-return inlet valve (29) and a non-return outlet valve (31) connect a working chamber (7) to the suction chamber (21) and the pressure chamber (21). A tappet (11) acts on a working diaphragm (9) for carrying out the suction stroke against the force exerted by a spring (17). The spring (17) acts op the working diaphragm (9) for carrying out the pressure stroke. The suction chamber (19) and possibly the pressure chamber (21) are designed as annulus segments which are curved around the tappet (11). <IMAGE>

Description

SPECIFICATION A diaphragm pump The invention relates to a diaphragm pump, more especially a fuel diaphragm pump for an internal-combustion engine, the pump comprising a housing, which comprises a suction chamber provided with an inlet port and a pressure chamber provided with an outlet port, a flexible working diaphragm, which partitions off a working chamber in the housing, a non-return inlet valve arrangement connecting the suction chamber to the working chamber, and a nonreturn outlet valve arrangement connecting the working chamber to the pressure chamber, a spring which acts on the working diaphragm for carrying out the pressure stroke in the direction of reducing the size of the working chamber, and comprising a tappet which is slidably guided in the housing and acts on the working diaphragm for carrying out the suction stroke, against the force exerted by the spring, in the direction of enlarging the working chamber.

Such a fuel diaphragm pump is known from British Patent 983 694. The tappet acting on the working diaphragm is frictionally moved at a predetermined velocity during the suction stroke by means of a cam driven from the internalcombustion engine. During the pressure stroke, the fuel consumption of the internal-combustion engine determines the movement of the working diaphragm, in which connection the tappet may lift from the cam. The known diaphragm pump requires only relatively low driving forces.

However, it has turned out that the discharge capacity varies in dependence on the speed and rises inadequately, particularly as the speed increases and the fuel requirement consequently rises.

It is the object of the invention to increase the discharge capacity of a diaphragm pump of the kind described in detail at the beginning, particularly for high pumping frequencies.

According to the invention, this problem is solved in that the volume of suction chamber is larger than the volume of the pressure chamber.

The volume of the suction chamber should be at least double the size, but preferably treble the size of the volume of the pressure chamber. In this way, it is ensured that the fuel is available in a sufficient quantity in the direct vicinity of the inlet valve arrangement and can be sucked into the working chamber without any time delay.

At least the suction chamber, but preferably also the pressure chamber, has the shape of an annulus segment which is curved around the longitudinal axis of the tappet. In this way, optimum use is made of the housing diameter provided for the working diaphragm. Expediently, the annulus segments are partitioned off by two substantially radially extending partition walls from an annulus extending over 3600. The size of the pressure chamber is substantially only limited by the size of the outlet valve. The suction chamber covers the remainder of the annulus.

In a preferred constructional form, several nonreturn inlet valves are provided along the suction chamber. The inlet valves are arranged along a diameter circle of the working chamber so that the working chamber can be quickly and evenly filled.

In a preferred constructional form, provision is made for the suction chamber and the pressure chamber to be sealed towards the working chamber by means of a ring-shaped valve holder which is tightly secured to the housing and carries the inlet and outlet valve arrangements. The valve holder which is, for example, plate-shaped forms a constructional unit provided with all the valves.

The valve holder may additionally carry a filtering screen which completely covers the inlet valve arrangement on the side pointing to the suction chamber. In this way, additional seats or fastening elements for the filtering screen on the housing are dispensed with.

In a preferred constructional form, the working diaphragm comprises a central stiff plate which carries a rod which is slidably guided on the housing and projects transversely to the plate and which is sealed with respect to the housing by means of a seal. The rod acts on the plate during the suction stroke on the side directed towards the working chamber. The spring bears against the side of the plate which is directed away from the working chamber. The rod may be the tappet which is then integrally connected to the plate. In order to uncouple the tappet movement from the movement of the working diaphragm during the pressure stroke, the tappet may be slidably guided in the housing separately from the rod. The sliding movement of the tappet can be directly transferred to the rod if the tappet and the rod are coaxially arranged.If the tappet extends at an angle to the rod, then a lever gear may be interposed.

In a preferred constructional form, the tappet is designed as a tube which is slidable in the housing and in which the rod engages. The tube guides the rod and thus the diaphragm plate which is preferably integrally formed with the rod.

The pushing force can be directly transferred by the tube. However, preferred are constructional forms wherein the tube comprises a filler, which strikes against the rod during the suction stroke, and at its end that is directed away from the working diaphragm carries a cam follower. The tube may then be relatively thin-walled.

The rod attached to the plate is sealed with respect to the housing. Suitable are gaskets which are secured to the housing and comprise sealing lips, or the like, enclosing the rod.

However, due to the relative movement between the gasket and the rod, there may occur leaks, particularly when the gasket has been in use for some considerable time. It is better if the rod passes through a sealing diaphragm, whose external edge that is remote from the rod is held on the housing. The sealing diaphragm extends at an axial distance from the working diaphragm and is deflected together with the latter. The sealing diaphragm edge that is close to the rod is tightly secured to the rod or the plate, for example by means of a sleeve-shaped gasket which forms the edge that is close to the rod and tightly embraces the rod. It is also favourable if the working diaphragm and the sealing diaphragm are integrally formed. The working diaphragm edge that is remote from the tappet may be glued to the housing or be secured thereto in a different manner.Expediently, the valve holder is utilised for fastening, for example in such a way that the external edge of the sealing diaphragm is clamped between the valve holder and the housing. The surface of the sealing diaphragm is smaller than the surface of the working diaphragm.

The spring which is arranged on the working diaphragm side that is remote from the tappet is supported on a cover which is fixed to the housing and caps the working diaphragm on the side that is remote from the tappet. The cover is expediently completely closed and is sealed towards the working diaphragm. In this way, there is formed between the cover and the working diaphragm an elastic air cushion which supports the action of the spring so that the latter can be less amply dimensioned and which thermally insulates the working chamber The housing zones forming the suction chamber, the pressure chamber and the working chamber as well as the guides for the tappet.

including a fastening flange, preferably consist of plastics material. By this means, the housing thermally insulates the working chamber with respect to the engine block and the comparatively high temperatures thereof. The housing may be integrally formed as an injection-moulded part or the like. The valve holder may also consist of plastics material and may be glued or welded into the housing. In this way, it is possible to produce the diaphragm pump largely from plastics material which considerably reduces the production costs. The fact that plastics material can be used for the production of the housing results not least from the principle applied in connection with the diaphragm pump, according to which the tappet causes the suction stroke and the spring causes the pressure stroke.Pumps working according to this principle require relatively low operating forces so that it is possible to use materials of relatively low mechanical strength, such as plastics material.

Some exemplified embodiments of the invention will hereinafter be explained in more detail with reference to the drawings, in which Figure 1 shows a section through a first constructional form of a fuel diaphragm pump; Figure 2 shows a section along a line Il-Il through the diaphragm pump of Fig. 1, and Figures 3 to 5 show different constructional forms of fuel diaphragm pumps.

Figs. 1 and 2 show a fuel diaphragm pump for an internai-combustion engine. The diaphragm pump comprises a housing 1 with a distance foot 5 which is integrally formed therewith and carries a fastening flange 3. In the housing 1 ,there is provided a working chamber 7 which, on the side that is directed away from the fastening flange 3, is sealed by a flexible working diaphragm 9. A tappet 11, which is slidably guided in the distance foot 5, co-operates, with the end that is remote from the diaphragm, with an eccentric cam 13 which is continuously driven from the internalcombustion engine, and moves the working diaphragm 9 in the direction of enlarging the working chamber 7.Between a cover 15, which is attached to the housing 1 on the side of the working diaphragm 9 that is remote from the tappet, and the working diaphragm 9 there is clamped a helical compression spring 1 7 which biases the working diaphragm 9 in the direction of reducing the size of the working chamber 7. On the side of the working diaphragm 9 that points to the fastening flange 3 there is provided in the housing 1 a suction chamber 19 and a pressure chamber 21. A fuel supply line 23 opens into the suction chamber 19, while a fuel delivery line 25 passes on from the pressure chamber 21. The suction chamber 1 9 and the pressure chamber 21 are sealed towards the working chamber 7 by a valve-holder plate 27.The valve-holder plate 27 has several non-return inlet valves 29 which allowa passage from the suction chamber 1 9 to the working chamber 7 and which automaticaily cut off in the opposite direction. A non-return outlet valve 31 connects the working chamber 7 to the pressure chamber 21. The non-return outlet valve opens from the working chamber 7 to the pressure chamber 21 and automatically shuts in the opposite direction.

The eccentric cam 13 frictionally drives the working diaphragm 9, against the force exerted by the spring 17, in the direction of enlarging the working chamber 7. During this suction stroke, fuel is sucked from the suction chamber 19 through the non-return inlet valves 29 into the working chamber 7. During the subsequent working or pressure stroke, the spring 1 7 presses the fuel, which has been sucked into the working chamber 7, through the non-return valve 31 into the pressure chamber 21 and the delivery line 25.

The movement is not effected frictionally, the pressure-stroke movement of the working diaphragm 9 being effected in accordance with the fuel consumption of, for example, the internalcombustion engine carburettor which is connected to the delivery line 25. If the fuel consumption is low, only a proportion of the quantity of fuel contained in the working chamber 7 is withdrawn. Accordingly, the frictional suction stroke is also limited to a smaller angle of rotation of the eccentric cam 13 of, for example, 700. The pressure force of the tappet, which has to be applied by the eccentric cam 13 during the suction stroke, is low and, for example, is of the order of 6 kp.

Fig. 2 shows details of the suction chamber 1 9 and the pressure chamber 21. The suction chamber 19 and the pressure chamber 21 are in the shape of annulus segments which completely enclose the tappet and are separated only by two approximately radially extending partition walls 33 and 35. The suction chamber 19 is considerably larger than the pressure chamber 21, the volume ratio being approximately 3:1.

The non-return inlet valves 29 are arranged in an angularly offset manner on a diameter circle of the annulus so that the working chamber 7 is filled quickly and evenly despite a comparatively large working chamber surface. The large volume of the suction chamber 1 9 ensures that there cannot occur any delivery rate variations if the speeds are high or if the speed of the internalcombustion engine is suddenly increased. Due to the large-dimensioned suction chamber 19, fuel can flow into the working chamber 7 with virtually no time delay.

The working diaphragm 9 comprises a diaphragm plate 36, with the circumferential flange 37 of which an elastic diaphragm ring 39 has been integrally moulded. The integrally moulded diaphragm ring 39 passes through fastening openings 41 in the circumferential flange 37. The external edge of the diaphragm ring 39 is tightly clamped between the cover 1 5 and the axial front edge of a ring-shaped, radially outwardly projecting housing flange 43. A flange edge 45 of the cover 1 5, which engages behind the annular flange 43. holds the cover on the housing 1.

A central guide pin 47, which projects at a right angle, is integrally formed with the diaphragm plate 36. The guide pin slidably engages in a tube 49 which is slidably guided in the distance foot 5. A ring seal 51 seals the tube 49, at the outlet point thereof on the working chamber side, with respect to the housing 1. At the end that is on the eccentric cam side and emerges from the fastening flange 3, the tube 49 carries a mushroom-shaped cam follower 53, the head 55 of which radially projects from the tube 49 and axially bears against the eccentric cam 13.

A biasing spring 57 clamped between the head 55 and the fastening flange 3 keeps the cam follower 53 in abutting contact with the eccentric cam 13, whereby the tube 49 also follows the movement of the cam follower 55. The tube 49 contains a filler 59, the axial end on the working diaphragm side of which forms a stop face for the guide pin 47 of the diaphragm plate 35. The eccentric cam 1 3 pushes, via the cam follower 55 and the filler 59, the guide pin 47 and consequently the working diaphragm 9 in the direction of an enlarging working chamber 7.

During the pressure stroke, the filler 59 lifts from the guide pin 47. The guide pin 47 then follows the movement of the tappet 11 in accordance with the fuel consumption of the carburettor connected to the delivery pipeline 25.

The guide pin 47 is sealed with respect to the housing by means of an elastic sealing diaphragm 61. The sealing diaphragm 61 carries, on its internal edge on the guide pin side, a sealing sleeve 63 which tightly embraces the guide pin 47 or is integrally injection-moulded therewith.

The external edge of the sealing diaphragm 61 carries a torus 65 which is clamped between the housing 1 and the valve holder plate 27 in a formlocked and tight manner. The sealing diaphragm 61 may be additionally glued both on its internal edge and on its external edge.

The housing 1, including the distance foot 5 and the fastening flange 3, is formed as a onepiece plastic moulding. The valve holder plate 27 is also made of plastics material. Due to the relatively low operating forces which act on the housing 1 via the tappet 11, the mechanical load is low so that, despite the use of plastics material, the fuel pump can withstand the operational stresses. However, the plastic housing 1 thermally insulates the working chamber 7, the suction chamber 19 and the pressure chamber 21 from the internal-combustion engine. Consequently, there is no danger of the delivered fuel being overheated in spite of the fact that the working chamber 7 is provided on the internal-combustion engine side of the working diaphragm 9. The cover 1 5 is completely closed, in other words does not have any vent hole.Between the working diaphragm 9 and the cover 15 there is enclosed an air cushion which additionally thermally shields the working chamber 7 against the temperatures in the engine compartment. The air cushion enclosed between the working diaphragm 9 and the cover 1 5 supports the action of the spring 17.

Fig. 1 furthermore shows that on the suction chamber side of the valve holder plate 27 there is fitted a sieve 67 which covers the inlet valves 29.

The sieve 67 is, for example, glued or welded to the valve holder plate 27. The valve holder plate 27, for its part, is glued or welded to the housing 1.

Fig. 3 shows a different constructional form of a fuel diaphragm pump which differs from the diaphragm pump of Figs. 1 and 2 only in the design of its tappet. For explaining the diaphragm pump shown in Fig. 3, reference is therefore made to the description of Figs. 1 and 2, parts acting in the same way having been provided in Fig. 3 with reference numerals which have been increased by the number 100 compared to Figs. 1 and 2. In contrast to the pump shown in Figs. 1 and 2, the tappet 111 is fixedly connected to the diaphragm plate 1 36. In this constructional form, the head 1 55 of the tappet 111 can lift from the eccentric cam 11 3 during the pressure stroke of the working diaphragm 109.Shown in broken lines in Fig. 3 is an alternative to tha arrangement of the fuel sieve which, as depicted at 171, is provided in the fuel supply line 123. The dimensioning of the suction chamber 119 and of the pressure chamber 121 corresponds to that of the constructional form shown in Fig. 1. Likewise, the inlet and outlet valves 129 and 131 respectively have been pre-assembled on a common valve holder plate 127. Furthermore, the housing 101 including the distance foot 105 and fastening flange 103 consists of plastics material.

The cover 11 5 is again completely closed and, with the working diaphragm 109, encloses an insulating air cushion.

The diaphragm pump shown in Fig. 4 differs from the diaphragm pump shown in Fig. 3 substantially only in that an additional ring seal 273 is provided rather than a sealing diaphragm 1 61. The other parts of the diaphragm pump have been given reference numerals which are increased by the number 200 compared to the constructional form shown in Fig. 1. For explaining these parts, reference is made to the description of Figs. 1 and 2. The tappet 211 is again fixedly connected to the diaphragm plate 236 so that its cam follower head 255 can lift off during the pressure stroke. The housing 201 again consists of plastics material and comprises a suction chamber 219 which is large as compared to the pressure chamber 221. The cover 215 encloses, with the working diaphragm 209, an insulating air cushion.The inlet and outlet valves 229 and 231 respectively have been preassembled on a common valve holder plate 227.

Fig. 5 shows another fuel diaphragm pump wherein, in contrast to the above-described diaphragm pumps, the tappet 311 is not guided vertically to the working diaphragm 309 but is guided approximately parallel thereto in a slidable manner in the housing 301. Parts acting in the same way as those shown in Fig. 1 have been provided in Fig. 5 with reference numerals increased by the number 300. For the explanation, reference is made to the description of Figs. 1 and 2.

The tappet 311, the cam follower head 355 of which explores the eccentric cam 313, displaces via a shift lever 375, which is pivotally mounted in the housing 301, the guide pin 347 which projects vertically from the diaphragm plate 336 and is slidably guided along the housing 301 in a manner not shown in detail. A ring seal 377 seals the tappet 31 7 with respect to tne housing 30'1.

The volume of the suction chamber 319, which is designed as an annulus segment, has again been dimensioned larger than that of the pressure chamber 321. The housing 301 consists of plastic material and the inlet and outlet valves 329 and 331 have been pre-assembled on the common valve holder plate 327. The cover 315 and the working diaphragm 309 tightly seal an air cushion.

Claims

1. A diaphragm pump, comprising a housing (1) which comprises a suction chamber (19) provided with an inlet port (23) and a pressure chamber (21) provided with an inlet port (23) and a pressure chamber (21) provided with an outlet port (25), and comprising a flexible working diaphragm (9), which partitions off a working chamber (7) in the housing (1), and comprising a non-return inlet valve arrangement (29) connecting the suction chamber (19) to the working chamber (7) and a non-return outlet valve arrangement (31) connecting the working chamber (7) to the pressure chamber (21), and comprising a spring (17) which acts on the working diaphragm (9) for carrying out the pressure stroke in the direction of reducing the size of the working chamber (7), and comprising a tappet (11) which is slidably guided in the housing (1) and acts on the working diaphragm (9) for carrying out the suction stroke, against the force exerted by the spring (17), in the direction of enlarging the working chamber (7), characterised in that the volume of the suction chamber (19) is larger than the volume of the pressure chamber (21).

2. A diaphragm pump as claimed in Claim 1, characterised in that the volume of the suction chamber (19) is at least double as large as the volume of the pressure chamber (21).

3. A diaphragm pump as claimed in Claim 2, characterised in that the volume of the suction chamber (19) is approximately three times as large as the volume of the pressure chamber (21).

4. A diaphragm pump as claimed in Claim 1, characterised in that at least the suction chamber (19),end preferably also the pressure chamber (21), has the shape of an annulus segment which is curved around the longitudinal axis of the tappet (11).

5. A diaphragm pump as claimed in Claim 4, characterised in that the tappet (1 1) passes through a central opening in an annulus which is divided by two substantially radial partition walls (33, 35) into the pressure chamber (21) and the suction chamber (19).

6. A diaphragm pump as claimed in Claim 4, characterised in that there are provided several non-return inlet valves (29) which lead from the suction chamber (19) to the working chamber (7).

7. A diaphragm pump as claimed in Claim 4, characterised in that the suction chamber (19) and the pressure chamber (21) are sealed towards the working chamber (7) by means of a ring-shaped valve holder (27) which is tightly secured to the housing (1) and carries the inlet and outlet valve arrangements (29 and 31 respectively).

8. A diaphragm pump as claimed in Claim 7, characterised in that the valve holder (27) carries a filtering screen (67) which completely covers the inlet valve arrangement (29) on the side pointing to the suction chamber (19).

9. A diaphragm pump as claimed in Claim 7, characterised in that the valve holder (27) is substantially plate-shaped.

10. A diaphragm pump as claimed in Claim 1, characterised in that the working diaphragm (9) has a stiff central zone (36), and in that the spring (17) bears against the side of the stiff zone (36) which is directed away from the working chamber (7), and in that the tappet (11) acts, during the suction stroke, on the side which is directed towards the working chamber (7).

11. A diaphragm pump as claimed in Claim 10, characterised in that the working diaphragm (9) comprises a central plate (36) which carries a rod (47; 111; 211; 347) which is slidably guided along the housing (1) and projects transversely to the plate (36) and is sealed with respect to the housing (1) by means of a seal (61; 151; 161; 251; 273; 361).

12. A diaphragm pump as claimed in Claim 11, characterised in that the rod (111; 211) forms the tappet.

13. A diaphragm pump as claimed in Claim 11, characterised in that the rod (47; 347) is slidable by means of the tappet (11; 311).

14. A diaphragm pump as claimed in Claim 13, characterised in that the sliding movement directions of the rod (347) and the tappet (311) extend at an angle to each other, and in that a lever gear (375) is connected between the tappet (311) and the rod (347).

1 5. A diaphragm pump as claimed in Claim 13, characterised in that the rod (47) and the tappet (11) are coaxially arranged.

1 6. A diaphragm pump as claimed in Claim 15, characterised in that the rod (47) slidably engages in a front-end guide opening in the tappet (11) which, for its part, is guided in the housing (1).

17. A diaphragm pump as claimed in Claim 16, characterised in that the tappet (11) is designed as a tube (49) which is slidable in the housing (1) and in which the rod (47) engages.

18. A diaphragm pump as claimed in Claim 17, characterised in that the tube (49) comprises a filler (59) which strikes against the rod (47) during the suction stroke.

19. A diaphragm pump as claimed in Claim 17, characterised in that the end of the tube (49) that is directed away from the working diaphragm (9) carries a cam follower (53).

20. A diaphragm pump as claimed in Claim 15, characterised in that the tappet (11) is biased away from the working diaphragm (9) by means of a spring (57).

21. A diaphragm pump as claimed in Claim 11, characterised in that the rod (47) passes through a sealing diaphragm (61), whose external edge that is remote from the rod is held on the housing (1).

22. A diaphragm pump as claimed in Claim 21, characterised in that the sealing diaphragm (61) comprises a sleeve-shaped gasket (63) which tightly embraces the rod.

23. A diaphragm pump as claimed in Claim 21, characterised in that the inlet and outlet valve arrangements (29 and 31 respectively) are provided on a joint valve holder (27) which seals the suction chamber (19) and the pressure chamber (21) towards the working chamber (7), and in that the external edge of the sealing diaphragm (61) is held between the valve holder (27) and the housing (1).

24. A diaphragm pump as claimed in Claim 10, characterised in that the spring (17) is clamped between the working diaphragm (9) and a cover (15) which is secured to the housing (1), and in that, for forming an elastic air cushion, the cover (15) is completely closed and is sealed towards the working diaphragm (9).

25. A diaphragm pump as claimed in Claim 1, characterised in that the zones of the housing (1) forming the suction chamber (19), the pressure chamber (21) and the working chamber (7) as well as the guides (5) for the tappet (11) and including a fastening flange (3) consist of plastics material.

26. A diaphragm pump as claimed in Claim 25, characterised in that the inlet and outlet valve arrangements (29 and 31 respectively) are provided on a joint valve holder (27) which seals the suction chamber (19) and the pressure chamber (21) towards the working chamber (7), and in that the valve holder (27) also consists of plastics material and has been glued or welded into the housing (1).

27. A diaphragm pump as claimed in Claim 1, and substantially as described with reference to the accompanying drawing.