WO1995015446A1

WO1995015446A1 - Vibration damping arrangement for injection pumps on internal combustion engines

Info

Publication number: WO1995015446A1
Application number: PCT/SE1994/001151
Authority: WO
Inventors: Hilding Nilsson; Göran Masus
Original assignee: Scania Cv Aktiebolag
Priority date: 1993-11-30
Filing date: 1994-11-29
Publication date: 1995-06-08
Also published as: DE4499420T1; SE9303975L; SE9303975D0; SE502183C2; BR9408114A

Abstract

Vibration damping arrangement on a fuel injection pump (12) fitted to the side of a combustion engine, whereby the pump driven by the engine crankshaft incorporates a substantially box-shaped pump housing (14) fitted to the side of the engine cylinder block. A cylindrical vibration damper (48) is arranged in the region of one end of the pump housing (14), directed transversely to the longitudinal extent of the pump housing and fastened in a holder (50) mounted on the top of an end housing (36) fastened to the pump housing. The vibration damper (48) incorporates a cylindrical housing with an internal damping chamber in which an axially movable damping body is arranged.

Description

Vibration damping arrangement for injection pumps on internal combustion engines

The present invention relates to a vibration damping arrangement of the kind indicated in the preamble of claim 1 and to a vibration damper of the kind indicated in claim 12, which damper may with advantage be incorporated in a vibration damping arrangement of the aforesaid kind.

State of the art

It is a known fact that vibrations nearly always occur in the operation of a motor vehicle engine and gearbox and of relating units and equipment items fitted to the engine and/or the gearbox, as for example the fuel injection pump on a diesel engine or on other kinds of injection engines.

Fuel pump vibration problems are greater where use is made of so-called in-line pumps which supply fuel at high pressure to directly injected engines. Such vibrations give rise to noise and material-fatiguing oscillations in affected components and units, and it is therefore necessary as far as possible to prevent their occurrence or, if this cannot be achieved to a sufficient extent, to damp them efficiently.

Currently known solutions for damping fuel injection pump vibrations most commonly involve designs intended to shift the critical frequency range by varying the rigidity of fastenings or the mass of the vibration system.

An example of a known arrangement for external damping of vibrations in mechanisms and machine components in general is a vibration damper described in US A 3 173 514. This known vibration damper incorporates a gastight cylindrical housing intended for fastening to the mechanism or machine component whose vibrations are to be damped. Inside the cylindrical housing there is a likewise cylindrical central tubular piston steering component which is coaxial with the housing. Accommodated for axial movement on this central piston steering component is a circular piston in the form of a relatively heavy solid body which has its outside in sealing contact with the inside of the housing and its inside in sealing contact with the inside of the piston steering component. In the region of the opposite ends of the tubular piston steering component there are valve apertures in the wall of the piston steering component, and via these valve apertures and the open inner pipe passage of the tubular piston steering component the end spaces of the housing are in communication with each other. At the movable weight body's respective end positions in the housing the valve apertures at the pertinent end of the piston steering component are closed by the weight body, thereby forming with the pertinent end of the weight body an enclosed circular compression chamber. Compressible fluid in this chamber then forms at the end of the weight body a movement- damping "fluid cushion" whereby axial movement of the body in the housing is braked so as to prevent the weight body striking the inside of the respective end of the housing.

This known vibration damper does however require precision machining of the damper's cylindrical housing, the circular piston and the tubular piston steering component in order to achieve the desired seal between their mutually cooperating constructional elements. This precision manufacturing does mean, however ,that this type of vibration damper is relatively expensive to produce, at the same time as its probably being sensitive from the operating safety point of view, at least in the long term.

Objects of the invention

The object of the present invention is above all to provide a new type of vibration damping arrangement intended for a fuel injection pump which is fastened to the side of an internal combustion engine. It applies particularly to an injection pump of the so-called in-line type which supplies fuel at high pressure to a multi-cylinder directly injected diesel engine, preferably intended for powering heavy vehicles. Such an in-line pump is usually driven by the engine crankshaft via spur gearing or chain drive and a separate pump drive shaft clutch.

The fuel pump usually incorporates in a conventional manner a number (corresponding to the engine cylinders) of pump elements incorporated in series in a mainly box-shaped pump housing which is fastened to the side of the engine block. The pump is generally secured to the side of the engine cylinder block either by fastening to the lower edge of a shelf-like mounting portion or by means of a vertical flange portion which is usually arranged in the engine transmission case. There may also be other supplementary fastening points.

The vibrations to be damped out consist predominantly of oscillation movements about a rotary oscillation axis which is usually parallel with and situated close to the pump's fastening surface. Thus in applications where the pump is fastened to a shelf which faces vertically upwards, the vibrations are directed transversely to the longitudinal central plane of the fuel pump and consist in practice of transverse outward oscillation movements at the upper part of the pump housing, as a result of the swinging rotary movement (oscillation movement) of the housing about a longitudinal rotary axis through the fastening of the pump housing.

If the pump is instead secured at one of its ends to a vertical flange, the pump can oscillate about a vertical axis which runs substantially through the fastening. Depending on the position of the fastening points, however, the main oscillation in such cases may also be about a substantially horizontal axis perpendicular to the longitudinal vertical central plane of the pump housing.

The effective vibration damping device of the vibration damping arrangement, i.e. the actual vibration damper, has in the aforesaid applications to be placed level with or in the region of the outer delineating lines of the pump housing as far away as possible from the oscillation axis where the vibrations have their maximum amplitude.

A further object of the invention is that the effective device of the vibration damping arrangement, i.e. the vibration damper, should take the form of a technically uncomplicated type of damper which is operationally reliable and relatively inexpensive to manufacture and which can be fitted in a holder with a very simple design and which is removably secured to the outside of the pump housing or to the outside of an end housing connected to the pump housing.

Description of the invention

The aforesaid objects are achieved with a vibration damping arrangement of the kind indicated in the introduction by the arrangement exhibiting the features indicated in the characterising part of claim 1. Preferred embodiments of the arrangement according to claim 1 may also exhibit the features indicated in the independent claims 2-11.

A distinguishing feature of the invention is therefore that a vibration damper is arranged on the pump housing or on an end housing fastened to the end of the pump housing. The vibration damper incorporates a housing with an internal damping chamber in the form of a hollow space. A damping body is arranged in the damping chamber, which bodyis in frictional contact with the housing so that it is radially steered in the damping chamber. The damping chamber is wholly or partially filled with liquid and/or provided with axially effective spring devices clamped between the damping body and the surrounding end walls of the housing. The damping body is axially movable in a substantially tangential direction about the pertinent rotary oscillation axis in order to achieve maximum damping.

In an embodiment used where the pump housing has one of its ends fastened to a mounting portion which faces vertically upwards and where the oscillation axis of the vibrations runs vertically, it is advantageous for the vibration damper to be arranged on the pump housing and to have its operating direction transverse to the longitudinal extent of the pump housing. For example, the damper may be fastened in a holder mounted on the upper side of the pump housing or on an end housing fastened to the end of the pump housing.

According to a preferred embodiment, the housing is cylindrical with an internal damping chamber which takes the form of a circular hollow space and which is bounded by an outer wall of the housing, an inner cylindrical wall of the housing and transverse end walls of the housing at the ends of said walls. The damping body is provided with radially directed surface portions via which the damping body is in frictional contact with at least one of the two walls so as to be axially steered in the damping chamber. The damping body is further clamped and axially centred in the damping chamber by means of axially effective spring devices.

The weight of the vibration damper, the rigidity of the springs and the viscosity of the liquid are optimised towards as effective damping as possible in the critical frequency range.

In the application described above, the vibration damper is therefore fastened and directed in relation to the pump housing so that the vibrations to be damped out are mainly directed in the effective axial direction of operation of the vibration damper. The vibration damper is placed just above the top of the pump housing or of the end housing connected to the pump housing, since the vibrations to be damped have their maximum amplitude in this region. Theoretically, fastening the vibration damper still further away from the rotary oscillation axis of the pump housing would result in better damping, since the effective lever of the vibration damper would in that case be longer and the vibration amplitude higher, but practical experience shows that in that case the vibration damper could for many practical reasons not be provided with sufficiently rigid fastening. Too weak fastening would lead to loss of the theoretically increased damping. The invention is therefore based on the principle of using as compact and rigid fastening of the vibration damper as possible. It is also advantageous for this endeavour to be combined with a very space-effective design solution whereby the vibration damper is fitted in a holder which is fastened directly to the top of the pump housing or of the end housing connected to the pump housing.

In cases where the fuel injection pump of in-line type is in a conventional manner oriented vertically and fastened to a vertical flange portion, which may form part of the engine transmission case, the rotary oscillation axis may, as mentioned above, be a vertical axis through the flange portion. In that case the damper has to be arranged on the rear edge of the pump housing, i.e. on the opposite side relative to the flange portion, and be directed horizontally.

Research carried out has shown that a vibration damping arrangement according to the invention may reduce vibrational accelerations from approximately 120 m/s² to approximately 80 m/s², a value which corresponds to, or is lower than, an acceptable critical lower limit value of the order of approximately 80-90 m/s².

It is also possible to achieve more rigid fastening by increasing the number of fastening points. This may however lead to undesirable bending stresses which may increase further under the effect of vibration. It also leads to higher vibration frequencies which in their turn lead to increased vibration amplitudes, which are of course undesirable.

The vibration damper holder may quite simply be a baseplate which may be fastened to the pump housing or end housing, e.g. by bolting on, and which has a pair of holder elements which stand up on opposite sides of the plate and between which the vibration damper is fastened. It is advantageous for such holder elements to be made integral with the baseplate and to form tongues of the latter which are of uniform width, are angled outwards substantially perpendicular to the planar elements of the baseplate fastened to the top of the housing and extend parallel with each other and with the pump housing.

A very simple and at the same time very operationally reliable design of the vibration damper is achieved if the inner cylindrical wall of the damper consists of a tubular sleeve which is inserted between the end walls and has its ends fastened in central holes in the end walls, whereby the tubular sleeve is mounted on a supporting pin or bolt which runs through it and which itself has its ends fastened in holes in the holder elements.

The damping body is preferably provided with axial through holes or ducts via which the sections of the damping chamber which are separated by the damping body are in mutual communication. On the insides of the end walls and in the damping body ends facing these end walls it is advantageous having circular recesses of which the inner ends form seats for the spring devices, preferably coil springs. It is in this case advantageous for the holes running axially through the damping body themselves to extend between the circular spring seat recesses. It is advantageous for the axial steering of the damping body in the damping chamber to be achieved by the damping body being in frictional contact with the inner cylindrical wall of the chamber via a number of bearing portions on each end of the damping body which are separate in the circumferential direction. This creates further passages via which the sections of the damping chamber separated by the damping body are in communication with each other as well as it reduces friction surfaces.

The damping chamber may be wholly or partially filled with a liquid, e.g. oil, which liquid then helps to brake the axial movement of the damping body in the damping chamber by the liquid being forced to flow through small gaps on the cylindrical outside and/or inside of the damping body, i.e. on the inside of the outer wall of the housing and/or on the outside of the inner cylindrical wall of the housing.

A preferred embodiment of the vibration damper which may with advantage be incorporated in a vibration damping arrangement according to the invention may, for example, exhibit the features indicated in patent claim 12.

Brief description of drawings

The invention will now be described and clarified further below with reference to the attached drawings which depict a vibration damping arrangement for a fuel injection pump on a combustion engine and the construction of a vibration damper incorporated in the arrangement. Figure 1 shows a side view of a diesel engine provided with a fuel injection pump to which a vibration damping arrangement according to the invention may be fitted.

Figure 2 shows in perspective a drive arrangement for such an injection pump, with controls and components belonging to and connected to the pump.

Figure 3 shows in side view (Fig.3a), in end view (Fig.3b) and in horizontal projection (3c) how a vibration damping arrangement according to the invention may be fitted to an injection pump of the kind shown in Fig.2, in which for the sake of clarity the mounting shelf is simplified.

Figure 4 shows the vibration damper itself, whereby Fig.4a shows an end view of the cylindrical vibration damper depicted in Figs.3a-3b, while Fig.4b shows the vibration damper according to Fig.4a in partial longitudinal section and side view along the line INb-INb in Fig.4a. The section A- A in Fig.4b is shown on the 45° line in the first quadrant of Fig.4a.

Description of embodiments

Fig.1 shows in side view a six-cylinder diesel engine 10 of the in-line type. A fuel injection pump 12 is secured to the side of the engine cylinder block by means of fastening devices at the lower part of the pump's box-shaped housing 14. The fuel injection pump 12 is fastened to a shelf-like fastening device 15 which incorporates a contact surface 17 which faces substantially upwards. The mounting shelf 15 has its front edge clamped to the transmission case of the engine 10, and its rear edge fastened to brackets (not depicted) which are in their turn fastened to the engine block. The pump is driven conventionally by the engine crankshaft via a gear or chain transmission, which is not visible in Fig.1.

Fig.2 shows in perspective and partly in cut-away sketch form the fuel injection pump 12 depicted in Fig.1. In the pump housing 14, six pump elements 16 corresponding to the six cylinders of the pertinent internal combustion engine are arranged in-line and are driven conventionally by a camshaft 18 via the latter's cams 20 and lifters 22 cooperating with them. The camshaft 18 is in its turn driven by the engine crankshaft 24 via spur gears 26,28,30 and the clutch 32 of the pump drive shaft 25. The injection pump 12 is controlled by an in this case mechanical control unit 34 contained in a housing 36 which forms an end housing fastened to a short side of the pump housing 14. The control unit 34 is operated via an accelerator pedal 38 and a starting arm 40 and via a stop arm 44 operated by means of a stop control 42.

Control of the pump elements 16 is by means of a control rod 46 which is movable in a longitudinal direction of the pump 12 and which is operated by the control unit 34, which in this case is a mechanical unit but might alternatively be an electronic control arrangement.

The camshaft drive 18,20, the impact movements of the pump elements 16 and the inherent vibrations of the engine block result in undesirable vibrations in the pump 12 whereby the various components of the pump will be subjected to vibrations which may gradually lead to fatigue failure. The most critical component here from the fatigue point of view is the longitudinally directed control rod 46, which will vibrate in a lateral direction because the whole pump vibrates and at the same time undergoes rotary movement about a rotary oscillation axis 19 which is parallel with the longitudinal direction of the pump housing 14 and is situated in or close to the fastening surface 17. Since the control rod 46 is situated in the region of the upper part of the pump housing 14, i.e. at a relatively great distance above the aforesaid rotary oscillation axis of the pump, the control rod will be subjected to a relatively great vibration movement in a lateral direction.

We now go on to consider in more detail the injection pump 12 and its vibration damper 48 which is fastened to the top of the pump housing 14 and forms part of the vibration damping arrangement according to the invention.

We now refer to Fig.3a, Fig.3b and Fig.3c. As may be seen in Fig.3a, the vibration damper 48 is arranged in the region of one end of the pump housing 14. The vibration damper 48 is a cylindrical damper which is arranged transversely to the longitudinal direction of the pump housing 14. The vibration damper 48 is fastened in a holder 50 which is mounted on the top of the end housing 36 which is fastened to the left side of the pump housing 14. The holder 50 of the vibration damper 48 incorporates, as depicted, a baseplate 52 which is bolted to the top of the end housing 36 and which has a pair of holder elements 54 which stand up on opposite sides of the plate and between which the vibration damper is fastened to a bearing shaft or bearing pin 56 which runs through it and which has its ends fastened in holes 58 in the holder elements 54. The holder elements are integral with the baseplate 52 and form tongues of the baseplate material which are of equal width. These two tongues are bent outwards substantially perpendicular to the baseplate 52 and extend parallel with each other and with the long sides of the pump housing 14.

With reference to Fig.4a and Fig.4b we now go on to consider in more detail the construction of the vibration damper 48.

The vibration damper 48 made in the form of a straight circular cylinder incorporates a cylindrical housing 60 with an internal damping chamber 62 in the form of an annular hollow space. This damping chamber is bounded outwards by the outer wall 64 of the housing 60, an inner cylindrical wall 66 and transverse end walls 68 and 70 which by means of annular seals 72 and 74 connect sealingly with the inside of the outer wall 64 and the outside of the inner wall 66. The inner cylindrical wall 66 consists, as depicted, of a tubular sleeve which is inserted between the end walls 68,70 and which has its ends fastened in central holes 76 and 78 in the end walls.

In the damping chamber 62 is arranged a damping body 80 (steered on the inner cylindrical wall 66) which therefore surrounds the wall 66 in an annular manner. At its opposite ends the annular damping body 80 has surface portions 82 directed radially inwards by means of which the damping body is in frictional contact with the outside of the inner wall 66. The damping body 80 is so dimensioned that there is an annular gap 84 between the outside of the damping body and the inside of the outer wall 64. The damping body 80 is therefore steered in axial movement on the inner cylindrical wall 66. The damping body is also centred axially in the damping chamber 62 by means of axially effective coil springs 86 and 88 clamped between the damping body 80 and the respective end walls 68 and 70. On the insides of the end walls 68 and 70 and in the ends of the damping body 80 which face the end walls there are respective annular recesses 90 and 92, the inner ends of which form seats for the coil springs 86 and 88. In the transverse intermediate wall between the recesses 92 of the damping body 80 there are throughflow holes 94 directed axially and distributed in the circumferential direction, via which holes the sections of the damping chamber 62 which are separated by the damping body are in communication with each other. These damping chamber sections are also in mutual communication via the annular slits 84 on the outside of the damping body. The surface portions 82 which are on the ends of the damping body 80 and which are directed radially inwards and are separated in the circumferential direction, form steering shoulders via which the damping body is in frictional contact with the outside of the inner wall 66. Between the shoulder-like bearing portions 82 on the outside of the wall 66 there are therefore axial passages 98 which are separate in the axial direction and which together with the annular gap 96 on the inside of the damping body 80 allow further throughflow communication between the sections of the damping chamber 62 which are separated by the damping body 80 and which are preferably at least partially filled with a liquid such as oil. This arrangement also results in a smaller friction surface between the damping body 80 and the inner wall 66.

Vibrations in the longitudinal direction of the vibration damper 48 which are to be damped cause axial displacement of the damping body 80 along the inner cylindrical wall 66. This axial displacement movement is damped by the braking frictional effect brought about by the contact surfaces of the bearing portion 82 relative to the outside of the inner wall 66. In addition, axial movement of the damping body 80 in the damping chamber 62 is also braked by the axially acting clamping springs 86 and 88. Finally, axial movement of the damping body 80 is also counteracted by viscous forces from the liquid in the damping chamber 62 when that liquid flows through the gap 84, through the axial holes 94 and through the axial passages 98 between the shoulders 82 and via the gap 96.

The embodiment described above has no limiting effect upon the invention, which may be implemented according to a multiplicity of alternative embodiments. Thus the placing of the vibration damper in the longitudinal direction of the fuel injection pump may be varied so long as the directional movement of the damping body remains unchanged.

The vibration damper itself may of course also be designed in a very large number of alternative forms, e.g. any of those indicated in SE 93 03 975. Thus the housing need not necessarily be cylindrical. If the through bearing pin is replaced by direct fastening to the end portions or the holder, the damping chamber need likewise not be designed as an annular hollow space. In such a design the damping body has to be frictionally steered relative to the outer wall. The springs may also be eliminated, in which case damping is only by liquid flow. In such a design the space inside the end wall portions should be provided with compressible elements for absorbing some of the volume change of the free space of the damping chamber which is caused by movement of the damping body. It is, however, advantageous to use springs, since they make it easier to optimise the vibration damper towards maximum possible damping effect within the specific critical frequency range in pertinent applications. In embodiments in which springs are used, liquid need not necessarily be used, but in that case a good damping effect is only achieved within a very narrow frequency range.

The description states that the mounting surface faces upwards. It is of course not necessary for the mounting surface to be absolutely flat, so a number of normal directions are possible. For interpretation of these directions, it may be assumed that the surface is flat where it abuts against the pump housing and that the directions are indicated relative to that flat part.

If the mounting surface has vertical extent, in which case the rotary oscillation axis is vertical or has horizontal direction transverse to the vertical central plane of the pump, then in this case also the vibration damper is placed as far away as practically possible from the rotary oscillation axis on the opposite side of the pump housing or an end housing fastened to the pump housing.

Claims

Patent claims

1. Vibration damping arrangement on a fuel injection pump (12) of in-line type fitted to the side of a multi-cylinder combustion engine (10) whereby the pump, which is preferably driven by the engine crankshaft (24), incorporates an at least mainly box-shaped pump housing (14) fitted to the side of the engine cylinder block, characterised in that a vibration damper (48) is fitted to the pump housing or an end housing (36) fastened to the end of the latter and incorporates a housing (60) with an internal damping chamber (62) bounded by at least one wall (64,66) and transverse end walls (68,70) at the ends of the wall (64,66), a damping body (80) being arranged in the damping chamber (62), the damping body (80) being in frictional contact with the wall so as to be radially steered in the damping chamber via surface portions (82), the damping chamber (62) being wholly or partially filled with liquid and/or provided with axially effective spring devices (86,88) clamped between the damping body and the surrounding end walls of the housing, and that the damping body (80) is movable axially in a substantially tangential direction about an axis (19) which forms the rotary oscillation axis for vibration movements of the fuel injection pump.

2. Arrangement according to claim 1 in which the fuel injection pump (12) is fastened to a fastening element (15) which is secured to the engine and which incorporates a fastening surface (17) to which the fuel injection pump (12) is fastened, and in which the rotary oscillation axis (19) is substantially parallel with the fastening surface (17) and situated in or close to that surface, characterised in that the vibration damper (48) is fastened to a fastening surface on the opposite side of the pump housing or of the end housing (14,36).

3. Arrangement according to claim 2, characterised in that the fastening surface (17) has a vertically upward normal direction and that the damper is fastened to the top of the pump housing or of the end housing (14,36).

4. Arrangement according to any one of the foregoing claims, characterised in that the vibration damper (48) is fastened in a holder (50) fitted to the pump housing or to the end housing (14), which holder incorporates a baseplate (52) with a pair of holder elements (54) which stand up on opposite sides of the plate and between which the vibration damper is fastened.

5. Arrangement according to claim 4, characterised in that the holder elements are integral with the baseplate (52) and form tongues of the baseplate which are of equal width and which are bent outwards substantially perpendicular to the part of the baseplate (52) secured to the top of the housing and extend parallel with each other and with the pump housing.

6. Arrangement according to any one of the foregoing claims, characterised in that the housing (60) is cylindrical with an internal damping chamber (62) in the form of an annular hollow space bounded by an outer wall (64) to the housing, an inner cylindrical wall (66) in the housing, which inner wall (66) is surrounded by the damping body (80) in an annular manner by means of radially directed surface portions (82) via which the damping body is in frictional contact with at least one of the two walls, preferably the inner one (66), and that the damping body is axially centred in the damping chamber (62) by means of axially effective spring devices (86,88) clamped between the damping body and the surrounding end walls (68,70) of the housing.

7. Arrangement according to claim 6, characterised in that the inner cylindrical wall (66) of the vibration damper consists of a sleeve which is arranged between the end walls and which has its ends fastened in central holes in the end walls, and that the sleeve is mounted on a through bearing shaft or pin (56) which has its ends fastened in holes (58) in the holder elements (54).

8. Arrangement according to any one of the foregoing claims, characterised in that the damping body has holes (94) running through it axially via which the sections of the damping chamber (62) separated by the damping body are in communication with each other.

9. Arrangement according to any one of the foregoing claims, characterised in that on the insides of the end walls (68,70) and in the ends of the damping body (80) which face the end walls there are annular recesses (90,92) the inner ends of which form seats for the spring devices (86,88), which are preferably coil springs, and that the through holes (94) extend between the annular recesses (90,92) through the damping body (80).

10. Arrangement according to any one of the foregoing claims, characterised in that the damping body (80) is in frictional contact with the inner cylindrical wall (66) of the damping chamber via a number of bearing portions (82) at each end of the damping body which are separate in the circumferential direction.

11. Arrangement according to any one of the foregoing claims, characterised in that the damping chamber (62) is at least partially filled with liquid, preferably oil.

12. Vibration damper (48), which may for example form part of an arrangement according to claim 1, incorporating a cylindrical housing (60) with an internal annular damping chamber (62) which is at least partially filled with liquid and is bounded by an outer wall (64), an inner cylindrical wall (66) and transverse end walls (68,70) which connect sealingly with the ends of the walls, characterised in that a damping body (80) is arranged in the damping chamber (62) which body surrounds the inner wall (66) in an annular manner and which body is in frictional contact with one wall (66) via a number of bearing portions (82), preferably situated at each end of the damping body and separated in the circumferential direction, and that the damping body (80) is clamped between axially effective springs (80,88) inserted between the damping body and adjacent end walls (68,70) at each end of the damping body, whereby the sections of the damping chamber (62) which are separated by the damping body have fluid communication with each other.