Control diaphragm for diaphragm carburetor

Abstract

A control diaphragm for controlling fuel supply in a carburetor of an internal combustion engine includes a functional region enclosing a sensing region concentrically and a peripheral fastening border for fastening the control diaphragm in the diaphragm carburetor. The control diaphragm closes a control chamber of the diaphragm carburetor and is operatively connected via the central sensing region to a control lever in the control chamber and senses the axial deflection of the sensing region in a manner dependent on operation-induced pressure change in the control chamber. The control diaphragm consists in one piece of temperature-resistant and fuel-resistant, non-elastomeric plastic and the functional region is configured by way of a multiplicity of concentric corrugations. The outermost corrugation directly adjoins the fastening border, and the radius of the outermost corrugation corresponds substantially to the radius of the control chamber. The sensing region directly adjoins the innermost corrugation and the radius of the sensing region corresponds to from 5 to 25% of the outer radius of the functional region.

Claims

1. A control diaphragm for controlling a supply of fuel in a diaphragm carburetor of an internal combustion engine, the control diaphragm comprising a central sensing region, a functional region enclosing the sensing region concentrically and a peripheral fastening border for fastening the control diaphragm in the diaphragm carburetor; wherein, in the installed state, the control diaphragm closes a control chamber of the diaphragm carburetor in a sealing manner and is operatively connected via the central sensing region to a control lever of the diaphragm carburetor arranged in the control chamber, the control lever sensing axial deflection of the sensing region in a manner which is dependent on an operation-induced pressure change in the control chamber; wherein: the control diaphragm consists in one piece of temperature-resistant and fuel-resistant, non-elastomeric plastic; the functional region is constituted by a multiplicity of concentric corrugations between the fastening border and the sensing region, wherein the outermost concentric corrugation directly adjoins the fastening border and the radius of the outermost concentric corrugation essentially corresponds to the radius of the control chamber; the sensing region directly adjoins the innermost concentric corrugation of the functional region and the radius of the sensing region corresponds to 5 to 25% of the outer radius of the functional region; and the sensing region comprises means for reinforcing the control diaphragm.

2. The control diaphragm according to claim 1, wherein the means for reinforcing is constituted by a thickening of the sensing region, wherein the thickness of the sensing region corresponds to 2 to 12 times the diaphragm thickness in the functional region.

3. The control diaphragm according to claim 1, wherein the sensing region has a maximum thickness of 10 to 500 micrometres.

4. The control diaphragm according to claim 1, wherein the means for reinforcing comprises radial reinforcing ribs and/or reinforcing corrugations in the sensing region.

5. The control diaphragm according to claim 4, wherein the reinforcing ribs and/or reinforcing corrugations have a maximum height of 10 to 500 micrometres.

6. The control diaphragm according to claim 1, wherein the diaphragm in the functional region has a thickness of 5 to 200 micrometres.

7. The control diaphragm according to claim 1, wherein four to ten concentric corrugations are formed in the functional region.

8. The control diaphragm according to claim 1, wherein the concentric corrugations are constituted wave-shaped in the radial direction and have an amplitude of 0.2 to 1.0 millimetres from wave crest to wave trough and/or a wavelength of 1.0 to 2.5 millimetres.

9. The control diaphragm according to claim 7, wherein the wavelength increases towards the central sensing region and/or the amplitude diminishes towards the central sensing region.

10. The control diaphragm according to claim 1, wherein the radius of the sensing region amounts to less than 20%.

11. The control diaphragm according to claim 1, wherein the radius of the sensing region amounts to 1 to 5 millimetres and/or the inner radius of the functional region amounts to 1 to 5 millimetres and the outer radius of the functional region amounts to the 10 to 20 millimetres.

12. The control diaphragm according to claim 1, wherein a plurality of radial reinforcing ribs are constituted in the functional region.

13. The control diaphragm according to claim 1, wherein the control diaphragm is made of a plastic with a temperature resistance of at least 150, selected from the group of polybenzimidazole (PBI), polyimides (PI), thermoplastic polyimides (TPI), polyamide-imide (PAI), polyether sulphone (PES), polyphenyl sulphone (PPSU), polyether imide (PEI), polysulphone (PSU), polyether ketone (PEK), polyaryletherketone (PAEK), polyphenylene sulphide (PPS), perfluoroalkoxy polymer (PFA), ethylene tetrafloroethylene (ETFE), polychlorine trifloroethylene (PCTFE), polyvinylidene fluoride (PVDF), polybutylene terephthalate (PBT), polyetheretherketone (PEEK) or combinations thereof.

14. The control diaphragm according to claim 1, wherein the plastic has a modulus of elasticity measured according to DIN EN ISO 527 of more than 800 N/mm.sup.2.

15. A diaphragm carburetor with the control diaphragm according to claim 1.

16. The control diaphragm according to claim 2, wherein the means for reinforcing is constituted by a thickening of the sensing region, wherein the thickness of the sensing region corresponds to 4 to 8 times the diaphragm thickness in the functional region.

17. The control diaphragm according to claim 5, wherein the reinforcing ribs and/or reinforcing corrugations have a maximum height of 20 to 300 micrometres.

18. The control diaphragm claim 12, wherein the plurality of radial reinforcing ribs extend only over the innermost concentric corrugations.

19. A control diaphragm for controlling a supply of fuel in a diaphragm carburetor of an internal combustion engine, comprising a central sensing region, a functional region enclosing the sensing region concentrically and a peripheral fastening border for fastening the control diaphragm in the diaphragm carburetor; wherein, in the installed state, the control diaphragm closes a control chamber of the diaphragm carburetor in a sealing manner and is operatively connected via the central sensing region to a control lever of the diaphragm carburetor arranged in the control chamber, which control lever senses the axial deflection of the sensing region in a manner which is dependent on an operation-induced pressure change in the control chamber; wherein: the control diaphragm consists in one piece of temperature-resistant and fuel-resistant, non-elastomeric plastic; the functional region is constituted by a multiplicity of concentric corrugations between the fastening border and the sensing region, wherein the outermost concentric corrugation directly adjoins the fastening border and the radius of the outermost concentric corrugation essentially corresponds to the radius of the control chamber; the sensing region directly adjoins the innermost concentric corrugation of the functional region and the radius of the sensing region corresponds to 5 to 25% of the outer radius of the functional region; and the sensing region includes radial reinforcing ribs and/or reinforcing corrugations.

20. A diaphragm carburetor having a control diaphragm, the control diaphragm comprising: a central sensing region, a functional region enclosing the sensing region concentrically and a peripheral fastening border for fastening the control diaphragm in the diaphragm carburetor, wherein, in the installed state, the control diaphragm closes a control chamber of the diaphragm carburetor in a sealing manner and is operatively connected via the central sensing region to a control lever of the diaphragm carburetor arranged in the control chamber, the control lever sensing the axial deflection of the sensing region in a manner which is dependent on an operation-induced pressure change in the control chamber; wherein the control diaphragm consists in one piece of temperature-resistant and fuel-resistant, non-elastomeric plastic; wherein the functional region is constituted by a multiplicity of concentric corrugations between the fastening border and the sensing region, wherein the outermost concentric corrugation directly adjoins the fastening border and the radius of the outermost concentric corrugation essentially corresponds to the radius of the control chamber; wherein the sensing region directly adjoins the innermost concentric corrugation of the functional region and the radius of the sensing region corresponds to 5 to 25% of the outer radius of the functional region; and wherein the sensing region includes means for reinforcing the control diaphragm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention is to be explained in greater detail below on the basis of examples of embodiment in connection with the drawing. In the figures:

(2) FIG. 1 shows a plan view of a known control diaphragm with a riveted reinforcing plate;

(3) FIG. 2 shows a cross-sectional representation of the control diaphragm from FIG. 1 in the installed state;

(4) FIG. 3 shows a cross-sectional representation of the control diaphragm from FIG. 1 with a diagrammatic representation of the deflection;

(5) FIG. 4 shows a plan view of a control diaphragm according to the invention;

(6) FIG. 5 shows a cross-sectional representation of the control diaphragm from FIG. 4 in the installed state;

(7) FIG. 6 shows a cross-sectional representation of the control diaphragm from FIG. 4 with a diagrammatic representation of the deflection;

(8) FIGS. 7A & 7B show displacement-pressure diagrams of a known control diaphragm (FIG. 7A) and of control diaphragms according to the invention (FIG. 7B);

(9) FIGS. 8A & 8B show a plan view (FIG. 8A) and a perspective view (FIG. 8B) of a control diaphragm according to the invention with radial reinforcing ribs;

(10) FIGS. 9A & 9B show a cross-sectional representation of a control diaphragm with a one-sided thickening;

(11) FIGS. 10A & 10B show a cross-sectional representation of a control diaphragm with a two-sided thickening; and

(12) FIGS. 11A-11C show a diagrammatic representation of three variants of a radially reinforced sensing region.

WAYS OF PERFORMING THE INVENTION

(13) A control diaphragm known from the prior art is shown in FIGS. 1 to 3. FIG. 1 shows the control diaphragm in a plan view. FIG. 2 shows a cross-sectional representation of the control diaphragm from FIG. 1 in the installed state. A control chamber and a control lever are represented diagrammatically.

(14) The control diaphragm made of a rubber-coated fabric comprises in the centre a disc-shaped riveted reinforcing plate 6, which forms a central sensing region 1 of the control diaphragm. Adjoining sensing region 1, the control diaphragm also comprises a functional region 2 formed by a circumferential peripheral corrugation 8, which is bordered by a fastening border 3. The control diaphragm is held by fastening border 3 in fastening means 7 of a diaphragm carburetor and closes a control chamber 5 (dashed lines) in a sealing manner. Arranged in control chamber 5 is a control lever 4, which can sense the diaphragm stroke of the control diaphragm and thus controls the supply of fuel for the diaphragm carburetor. As already described, reinforcing plate 6 brings about a uniform diaphragm stroke over the region covered by the reinforcing plate (see arrows in FIG. 3). In the ideal case, the region covered by the reinforcing plate oscillates uniformly in the axial direction. Under real conditions, however, reinforcing plate 6 tends to flutter or wobble, i.e. reinforcing plate 6 can become tilted slightly out of the diaphragm plane, especially in the presence of rapid positional changes of the carburetor, which can lead to irregularities of the carburetor control during operation.

(15) A measurement of the displacement-pressure characteristic of the known diaphragm from FIG. 1 is represented in FIG. 7A. The curve flattens out markedly from a pressure change of approximately 4 millibars, so that the control sensitivity from 4 millibars underpressure is markedly reduced.

(16) An embodiment of a control diaphragm with a multiplicity of concentric corrugations is shown in FIGS. 4 to 6. The control diaphragm has a thickness of approximately 20 to 100 micrometres. The plastic with a heat resistance of at least 150 C. is used for the control diaphragm, selected from the group of polybenzimidazole (PBI), polyimides (PI), thermoplastic polyimides (TPI), polyamide-imide (PAI), polyether sulphone (PES), polyphenyl sulphone (PPSU), polyether imide (PEI), polysulphone (PSU), polyether ketone (PEK), polyaryletherketone (PAEK), polyphenylene sulphide (PPS), perfluoroalkoxy polymer (PFA), ethylene tetrafloroethylene (ETFE), polychlorine trifloroethylene (PCTFE), polyvinylidene fluoride (PVDF), polybutylene terephthalate (PBT), polyetheretherketone (PEEK) or combinations thereof. Good results have been obtained with a PEEK film with a thickness of 25 micrometres (see FIG. 7B).

(17) The control diaphragm comprises a sensing region 1, a functional region 2 and a fastening border 3. Sensing region 1 and functional region 2 define the active exposed region of the control diaphragm, which is deflected on account of pressure changes in control chamber 5. The control diaphragm is held in a sealing manner in fastening means 7 of the carburetor by means of fastening border 3. A control lever 4 arranged in control chamber 5 senses the deflection of sensing region 1 of the control diaphragm and thus controls the supply of fuel in the carburetor.

(18) In the embodiment shown, sensing region 1 has a radius of less than 20% of the radius of the active region of the control diaphragm. The remaining part of the active region is constituted by functional region 2. Especially in the case of an embodiment in which a reinforcing means is constituted as a thickening (see FIGS. 9A & 9B and 10A & 10B), only a small mass is added to the control diaphragm with the small radius of the sensing region relative to the outer radius of the functional region or the radius of the control chamber.

(19) In the embodiment shown, seven concentric, circular corrugations are formed in the control diaphragm in functional region 2. The concentric corrugations are constituted wave-shaped with a constant wavelength w and amplitude a in the radial direction. The wave-shaped corrugations increase the flexibility and stretching capacity of the control diaphragm in functional region 2. During operation of the carburetor, the generated underpressure in the control chamber brings about a deflection of the control diaphragm, wherein the maximum diaphragm stroke in central sensing region 1 is at a maximum. On the other hand, sensing region 1 of the control diaphragm, said sensing region being constituted flat, experiences a curvature on account of the, in itself, relatively stretch-free control diaphragm and the reinforcing means.

(20) The flexibility of the control diaphragm is influenced by the concentric corrugations in such a way that the maximum deflection is directed in a controlled manner towards the central sensing region, which is selected small, such that no wobbling movements can arisesuch as occur with the known control diaphragms with a stiff oscillating plate and a merely peripheral functional region.

(21) Simulations have shown that the rigidity of the control diaphragm increases with increasing amplitude and increasing thickness and diminishes with increasing wavelength. By varying the number of corrugations and the corrugation geometry (wavelength, amplitude) in the radial direction, the response behaviour of the control diaphragm can thus be adjusted almost arbitrarily between a non-linear displacement-pressure characteristic (dominance of the material stretching) up to a linear displacement-pressure characteristic (dominance of the bending behaviour).

(22) The number of corrugations and their amplitudes a and wavelengths w can be selected such that the axial deflection of sensing region 1 runs essentially linear depending on the operation-induced pressure change in control chamber 5. An example of such a course is shown in FIG. 7B. FIG. 7B shows the measurement data of four control diaphragms, which have been produced from a PEEK film with a thickness of 25 micrometres. Functional region 2 comprises in each case seven circular corrugations 8, which are constituted wave-shaped in the radial direction. The amplitude amounts to approximately 0.44 millimetres and wavelength w amounts to approximately 1.6 millimetres. The radius of sensing region 1 is approximately 3 millimetres in size. The outer radius of functional region 2 is approximately 12.5 millimetres in size.

(23) In contrast with the previously described control diaphragms, the control diaphragm in FIG. 8A and FIG. 8B also comprises radial reinforcing ribs 9, which start at the outer edge region of sensing region 1 and run radially outwards over the first three concentric corrugations 8 of functional region 2. The height of reinforcing ribs 9 can vary, but usually lies in the plane of sensing region 1. The reinforcing ribs, which like the concentric corrugations are moulded into the control diaphragm, lead to a local reinforcement of the diaphragm without increasing the mass. The degree of reinforcement can be influenced by the number, the length, the width and the height of the reinforcing ribs. Viewed from the represented side, the reinforcing ribs are constituted as elevations in the wave troughs. Viewed from the other side, the reinforcing ribs are constituted as indents in the wave troughs.

(24) Two types of embodiment with a reinforcing means constituted as thickening 10 are shown in FIGS. 9A & 9B and 10A & 10B. FIGS. 9A and 10A show a cross-section through the entire diaphragm with fastening border 3, functional region 2 and sensing region 1. FIGS. 9B and 10B show in each case an enlarged detail of the sensing region of the control diaphragm. In FIGS. 9A & 9B, the reinforcing means in the sensing region is constituted as a one-sided thickening 10. The latter can be arranged on the side facing away from or facing towards the control lever. FIGS. 10A & 10B show a two-sided thickening of the sensing region.

(25) FIGS. 11A-11C show a diagrammatic representation of sensing region 1 of a control diaphragm with reinforcing means, which are constituted in the form of a plurality of radial reinforcing ribs (integrally moulded reinforcing means) and reinforcing corrugations (moulded-in reinforcing means). Three different arrangements are shown in FIG. 11A to 11C: (a) radial reinforcement ribs or reinforcing corrugations, which extend from the edge of the sensing region approximately into the centre of the sensing region; (b) as in (a) with an additional annular rib or corrugation in the centre; (c) a plurality of radial reinforcing ribs or reinforcing corrugations of differing length and offset with respect to one and otherin the variant shown, with an inner and an outer ring with in each case eight reinforcing ribs or corrugations.

(26) In the variant shown, eight or sixteen reinforcing ribs or corrugations are shown in each case, wherein at least six are preferably present.

(27) The reinforcing corrugations, in contrast with the reinforcing ribs, are wave-shaped embossments as in the case of the corrugations in the functional region (moulded-in reinforcing means). The latter can be produced for example by means of thermoforming processes. In this case, the thickness of the control diaphragm remains essentially the same also in the sensing region. The reinforcing ribs, on the other hand, are local thickenings of the diaphragm (integrally moulded reinforcing means).

(28) Reinforcing ribs can have a maximum height of 10 to 500 micrometres, preferably 20 to 300 micrometres, relative to the plane of the sensing region. Reinforcing corrugations can have a maximum height or depth also of 10 to 500 micrometres, preferably 20 to 300 micrometres.

LIST OF REFERENCE NUMBERS

(29) 1 sensing region 2 functional region 3 fastening border 4 control lever 5 control chamber 6 reinforcing plate 7 fastening means 8 concentric corrugations 9 radial reinforcing ribs 10 thickening 11 radial reinforcing ribs or reinforcing corrugations