GB2248272A

GB2248272A - Mounting throttle valve biasing springs

Info

Publication number: GB2248272A
Application number: GB9120372A
Authority: GB
Inventors: Gianni Fargnoli; Silvana Torri
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1990-09-28
Filing date: 1991-09-25
Publication date: 1992-04-01
Anticipated expiration: 2011-09-25
Also published as: FR2667359A1; GB9120372D0; FR2667359B1; DE4131502A1; IT9067730A0; GB2248272B; IT1241693B; IT9067730A1

Abstract

To permit preloading of the carburettor or throttle body valve biasing spring 31 the free end 42 of the spring is received in a slot 27 in an annular body projection 25. The slot 27 permits unrestricted rotation of the valve control lever 10 on which the other end (44, Fig. 1) of the spring is located prior to full seating of the spring in the projection 25 and of the lever to the valve shaft 5 by the nut 46. When fixed lever rotation is limited by a body abutment (40, Fig. 1). A further biasing spring (32. Fig. 3) associated with the other end of the shaft 5 is located in a similar slotted body projection (26) for spring preloading. Spring centring bushes 62, 63 hold the spring 31 assembled to the lever 10. <IMAGE>

Description

1 A FUEL SUPPLY DEVICE PARTICULARLY FOR HEAT ENGINES The present invention

relates to a fuel supply device adapted to control the rate of f low of gas through a duct; in particular, the invention relates to fuel supply devices for internal combustion engines, such as carburettors or butterfly bodies for fuel injection systems.

It is known that the power which can be developed by an internal combustion engine is controlled by regulating the rate of f low -of air aspirated by the engine by increasing or decreasing the opening of a butterfly valve controlled by the accelerator; in the case of engines having fuel supply by carburation, the butterfly valve is carried by the carburettor in which the fuel is directly aspirated by the ef f ect of the passage of the f low of air, thereby forming the fuel mixture; in the case of fuel injection engines, on the other hand, the butterfly valve is carried by the so-called "butterfly body" which regulates only the rate of flow of air, on the basis of which the fuel is then directly injected into the cylinders (or into the induction manifold) by the injectors. In both cases, a particularly significant constructional problem, both from the point of view of production costs and from the point of view of the ease, 2 rapidity and precision of assembly, is how to form the support and actuation of the control spindle for the butterfly valve, on which spindle the valve is carried, via a slot, for rotation.

In particular, during the assembly phase', a plurality of components have to be mounted on the body or casing of the carburetter or the butterfly body, such as the supports for the spindle, the control crank therefor to which, in use, is connected to the control cable from the accelerator and the biasing spring or springs for the spindle, which serve the purpose of holding the butterfly valve in the normally closed position and which must therefore be mounted pre-loaded. All this involves having to manage a plurality of different components which can change from model to model of the fuel supply device and which require complex movements for assembly, in particular to obtain the pre-load of the biasing spring.

The object of the present invention is that of providing a fuel supply device, such as a carburetter or a butterfly body for a fuel injection system, the structure of which makes it possible to assemble it quickly with few simple movements and utilising few sub-groups requiring off line pre- assembly.

3 The said object is achieved by the invention which relates to a fuel supply device, in particular a carburetter or butterfly body of a fuel injection system for a heat engine, of the type comprising a body defining, within its interior, part of a fuel supply duct for a gas stream, and a butterfly valve for the regulation of the said stream controlled by a spindle mounted passing through the said body, in respective coaxial seats thereof, and provided with a control crank fixed thereto to which is fixedly secured a first end of a biasing coil spring disposed coaxially with the spindle; in which the said body is provided with an abutment shoulder to define a limit of rotation of the said control crank; characterised by the f act that a first of the said seats is defined within a sleeve portion of the body adapted to house the said coil spring within its interior and provided with a longitudinal slot open towards a respective mouth of the seat through which the said spindle can be inserted; a second end of the said coil spring engaging in the said slot in an axially slidable manner, and the said abutment shoulder for the control crank being disposed, with respect to the said slot, in such a way that, with the spindle partially introduced into the said seats, in an axial position such that the crank does not interfere with the said abutment shoulder, the slot is already engaged by the said second end of the coil spring.

1 4 For a better understanding of the invention a nonlimitative description of an embodiment thereof is now given with reference to the attached drawings, in which:

Figure 1 illustrates a side view of a fuel supply device, in the specific example a butterfly body for a fuel injection system, formed according to the invention; Figures 2 and 3 illustrate on an enlarged scale a sectioned side view, respectively of the right and left halves of the device of Figure 1; Figures 4, 5 and 6 illustrate in perspective three different assembly stages of the device of Figure 1; and Figures 7 and 8 illustrate on an enlarged scale a detail of a pre- assembled sub-group of the device of Figure 1.

With ref erence to Figures from 1 to 6, a fuel supply device for a gas stream through a duct, in the specific example a fuel supply device for a heat engine, is generally indicated with the reference numeral 1; in the non limitative example illustrated the device 1 is constituted by a butterfly body usable for fuel injection systems: all that will be described can, however, be applied identically also to a different type of fuel supply device, for example to a carburettor.

The device 1 essentially comprises a body or casing 2, for example made of dye-cast metal, defining within its interior a part,of a fuel supply duct 3 for a gas stream (in the specific example the air supply of an engine) and a known butterfly valve 4 (hereinafter indicated simply as "butterfly") for the regulation of this gas stream; the butterfly 4 is carried in a known way by a control spindle 5, for example mounted passing through a longitudinal slot 6 in the spindle 5 retained, for example, by radial screws not illustrated f or simplicity. The valve 4, depending on the angular position assumed by the spindle 5, is movable between a closure position in which the duct section 3 is closed, illustrated in solid outline, and an open position, illustrated in broken outline.

The spindle 5 is mounted transversely passing through the body 2 within respective coaxial seats 8 and 9 and is provided with a known fixed control crank 10; this has a forked projection 11 to which, in use, is connected an accelerator control cable 12 in a known manner. Preferably, the cable 12 is passed over a pulley sector 13, for example made by moulding synthetic plastics material, carried on the crank 10, fixed thereto for example by co-moulding. In particular, the spindle 5 includes a central cylindrical abutment 15 of entirely ground constant diameter, and two opposite end spigots 16 and 18 which, when the device 1 is assembled, project out from opposite ends of the seats 8, 9 respectively with a 6 threaded pin 19 provided with a pair of opposite longitudinal flats 20 and with a pin 21 having a prismatic end part 21a adapted in a known way to receive a known potentiometer, not illustrated f or simplicity, adapted to detect the angular position of the butterfly 4; the end 18, between the pin 21 and the abutment 15, is moreover provided with opposite flats 22 similar to the flats 20: these flats 20, 22 are formed as chords of the respective cylinders defined by the pin 19 and the end 18 and therefore def ine on the spindle 5 respective axial shoulders 23, 24 to the central abutment 15.

According to the invention the seats 8, 9 are def ined within respective coaxial diametrically opposite sleeve portions 25, 26 of the body 2, which are provided with respective longitudinal through slots 27, 28 open towards the respective mouths of the seats 8, 9 indicated respectively with reference numerals 29, 30, in such a way as to interrupt the edge thereof; the sleeve portions 25, 26 are shaped in such a way that the seats 8, 9 are adapted to house within them respective biasing coil springs 31, 32 for the spindle 5, as well as respective rolling element bearings 33, 34 for supporting the spindle 5; these are mounted with an interference fit on opposite ends of the abutment 15, adjacent to the ends 16, 18 and are housed in the seats 8, 9, in the specific example in respective recesses 35 thgreof the concavity 7 of which faces towards the respective mouths 291 30, in which the rolling element bearing 34 is mounted with an interference f it and the rolling element bearing 33 is mounted with a radial clearance such as to permit relative axial movements between the seat and the bearing, but so as not to permit relative rotations in such a way that the spindle 5 can ef f ect, with respect to the seat 8, small displacements consequent, for example, on thermal expansions which take place in use. The seal between the seats 8, 9 and the duct section 3 (and vice versa) is ensured by the bearings 33, 34 themselves, which are of the sealed type, and by a sealing ring 37 which is mounted with a radial interference fit in the recess 35 of the seat 8 clamped between the outer ring of the bearing 33 and an axial shoulder 38 of the seat 8.

The springs 31, 32 have the purpose of normally holding the spindle 5 so as to maintain the valve 4 in the closure position; consequently, they must be pre-loaded upon assembly and on the body 2 there must be provided an adequate end-of- stroke stop for the spindle 5: in the example illustrated the stop is defined by an abutment shoulder 40 adapted to interfere, when the device 1 is assembled, with a projection 41 of the crank 10 to define a limit for the rotation thereof. The springs 31, 32, on the other hand, have respective ends 42, 43 by which they are connected fixedly to the body 2, these ends being 8 slidably engaged in the slots 27, 28 and respective opposite ends 44, 45 fixed to the spindle 5. In particular, the end 44 is fixedly secured to the crank 10 which is in turn fixedly secured to the end 16 in which it is engaged on the pin 19, which thanks to the flat 20 serves as a prismatic coupling, clamped in abutment against the shoulder 23 by means of the removable locking element defined by a known self- locking nut 46. The nut 46, thanks to its hexagonal prismatic form and to the fact that it is a standardised element, as well as functioning as a locking element is also able to serve, as will be seen, as a gripping point for an automatic manipulator. The end 45 is on the other hand fixed to a centring bush 48 on which the spring 32 is coaxially wound and which is in turn fixed angularly and axially to the spindle 5, being mounted on the pin 18, in engagement with the flats 22 and retained against the shoulders-24 by a locking member, for example a circlip 47.

According to the invention, the mouth 29 of the seat 8 has dimensions such as to permit the axial insertion through it of a sub-group 50 formed by the spindle 5, the spring 31, the bearing 33 and the crank 10, and possibly with the sector 13 (Figure 4); moreover, the abutment shoulder 40 for the crank 10 is disposed with respect to the slot 27, in such a way that, with the spindle 5 partially introduced into the seats 8, 9 (Figure 5) in an 9 axial position such that the projection 41 of the crank 10 does not yet interfere with the shoulder 40, the slot 27 is on the other hand engaged by the end 42 of the coil spring 31. This latter is r by the way, disposed in a predetermined and well defined axial position with respect to the spindle 5 in that the spring 31 is mounted externally on a centring bush 60 (Figure 2) fitted externally with play on the end 16 of the spindle 5, axially fixed to the crank 10 and, when assembly is complete (Figure 6) adapted to cooperate with at least one portion of an internal surface 61 of the sleeve portion 25 of the body 2.

In particular, the centring bush 60 includes a pair of opposite bushes 62, 63 snap engaged together axially head to head, for example by means of a series of radial teeth carried by respective resiliently deformable arms 64 (for example three in number disposed spaced circumferentially by 120) which project axially from the bush 62 towards the bush 63 and which are adapted to snap engage a frontal annular projection 65 of this latter; the bushes 62, 63 are externally provided with respective radial centring teeth 66 for the spring 31, which is fitted on them, clamped between the crank 10 and a flange portion 67 of the bush 62 f ormed by the opposite part of the crank 10 and having a diameter such as to cooperate with the surface 61 to centre the sub group 50 with respect to the seat 8. The bush 63 is further securely fixed to the crank 10, for example, through the sector 13, by means of a pin 70. In this way the sub group 50 def ines a self supporting unit which can be preassembled before insertion of the spindle 5 into the seats 8, 9 in the non limitative specific example illustrated the spring 31, for the purpose of being able to eliminate the biasing spring of the accelerator cable 12, is a double spiral spring formed by two wires 71 wound coaxially with the turns alongside one another.

With reference also to Figures 7 and 8, the second biasing spring 32 is fixed to the bush 48 via the end 45 in such a way to form with the bush 48 itself a unit which can be preassembled and which allows the spring 32 to be preloaded easily; in particular, the bush 48 includes a sleeve portion 75 and a terminal flange portion 76 from which axially project two semi circular ribs 78 concentric with and external to the sleeve portion 75, terminating with respective hook ends 79 diametrically opposite one another and facing the flange portion 76; the spring 32 is fixedly secured to the bush 48 in that it is inserted and fitted on to the semi circular ribs 78 in abutment against the flange portions 76 and has its ends 45 substantially omega shaped and inserted, through respective radial spaces 80 defined between the ribs 78, in an annular seat 85 defined 11 between these and the sleeve portion 75, in such a way that the end 45 is mounted straddling the sleeve portion 75.

The assembly of the device 1 formed according to the invention takes place as follows. First three main subgroups are assembled, constituted by the body 2 complete with the possible accessories, the sub-group 50, and the bush 45 - spring 52 assembly. This latter is obtained by fitting the end 45 of the spring 32 onto the ribs 78 by making the end 45 (which extends transversely in the sense of the diameter of the spring 32) radial spaces 80 in such a wayas straddling the sleeve portion 75, into abutment against the flange portion 76; and bush 48 are made to turn relatively to insert the end 45 under the hook illustrated in solid outline in Figure fixing the spring 32 to the bush 45 both radial senses.

pass through the to insert it, the seat 85, in then, spring 32 in such a way as portions 79 as 8, in this way in the axial and The assembly of the sub-groups 50 takes place on the other hand by fitting onto the spindle 5 first the bearing 33 and then the bush 60 with the spring 31, the crank 10 and the locking nut 46, which is screwed onto the threaded pin 19; in this way the spring 31 remains stacked between the flange portion 67 and the crank 10, 12 which remains connected to the hub 60 and axially locked between the shoulders 23 and the nut 46. Then assembly of the sub-groups 50 onto the body 2 takes place as illustrated in Figures 4, 5 and 6 by manipulating the sub-groups 50 manually or with an automatic manipulator, such as a robot, by gripping the nut 46 which is a readily accessible and grippable element. Therefore, holding the sub-groups 50 by the nut 46 the spindle 5 is introduced (Figure 4) in an axial direction (as shown by the arrow) through the mouth 29 until (Figure 5) the end 42 of the spring 31, which projects radially with respect to the rest of the spring, is inserted frontally into the slot 27. At this point, still acting on the nut 46, the spindle 5 is made to rotate in the direction of the arrow, whilst the body 2 remains stationary:

consequently, whilst the end 34 of the spring 31 rotates, together with the crank 10 and the spindle 5, the end 42 is maintained stationary by the slot 27, fixed to the body 2, and therefore the spring 31 is placed under load.

The magnitude of the rotation which is imparted to the spindle 2 is such as to put the spring 31 under tension to the value of the desired pre load and to carry the projection 41 beyond the abutment shoulder 40.

The assembly is completed by pressing the spindle 5 axially again, in such a way as to complete its introduction into the seats 8, 9 (Figure 6): this

13 movement carries the bearing 33 into the recess 35,. in abutment against the seal 37 previously assembled in the body 2, and the bush 60 with the spring 31 completely within the seat 8, whilst the end 21 projects from the seat 9. At this point the bearing 34 is mounted in a known way and then the spring 32 - bush 48 sub-groups is mounted; this sub-groups is manipulated by holding it by the bush 48 with a tool or with a robot manipulator and is partially inserted into the seat 9 with an axial movement similar to that previously described for the sub-groups 50 until the end 43 of the spring 32 is engaged in the slot 28: the axial dimensions of the pin 21 and the slot 28 are such that, in this position, not illustrated for simplicity, the bush 48 cannot yet engage the part 18 provided with the flats 22 and is therefore free to rotate with the spindle 5; simultaneously, however, the spring 32 is already in engagement against the bottom of the seat 9 (in the specific example against a shoulder 90) and is therefore hooked by the teeth 79. Similarly to what has been previously described for the sub-groups 50, therefore, the axial movement of the bush 48 is stopped and this is made to rotate causing displacement of the end 45 into the position illustrated in broken outline in Figure 8 in which the rotation of the bush 48 is also transmitted to the end 45, whilst the end 43 cannot rotate in that it is engaged by the slot 28. The spring 32 is therefore put under tension until is 14 it reaches the desired pre load value: then rotation is stopped and the axial displacement continued until the bush 48 is brought into contact against the shoulder 24 and consequently engaged with the flats 22 thus rendering it fixed with respect to the spindle 5 and therefore able to maintain the spring 32 pre-loaded when the tool or manipulator is removed. Finally, the circlip 47 is fitted and the nut 46 is released so that the springs 31, 32 carry the projection 41 against the abutment 40 in the operative rest position. The abutment 40, for the purpose of allowing small adjustments of this position, can possibly be provided with an adjustment screw 94 (Figure 1) for engagement against the projection 41.

From what has been described, the advantages associated with the invention will be apparent; thanks to the particular structure adopted for the assembly comprising the spindle, springs and seats, the majority of the elements comprising the assembly lend themselves to being preassembled in sub-groupss which constitute independent units, which can be manipulated without problems. These sub-groups can then be assembled with small simple movements (translations and rotations), which can be easily achieved by automatic assembly devices: these movements, moreover also make it possible to obtain automatically the pre-load of the spindle _biasing springs.

1 Consequently, assembly can be automated and, even if performed by hand in a conventional manner, can nevertheless be achieved in shorter times and ensuring a much improved quality control of the finished products.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

X 16

Claims

A f uel supply device, in particular a carburettor or butterfly body of a fuel injection system for a heat engine, of the type comprising a body defining within its interior a part of a supply duct for a gas stream and a butterf ly valve for the regulation of the said stream controlled by a spindle mounted passing through the said body in respective coaxial seats thereof and provided with a f ixed control crank to which a f irst end of a biasing coil spring disposed coaxially with the spindle is securely f ixed; in which the said body is provided with an abutment for defining a limit of rotation of the said control crank; characterised by the fact that a first of the said seats is defined within a sleeve portion of the body adapted to house the said coil spring within its interior and provided with a longitudinal slot open towards a respective mouth of the seat through which the said spindle is insertable; a second end of the said coil spring engaging within the said slot in an axially slidable manner and the said abutment shoulder for the control crank being disposed, with respect to the said slot, in such a way that, with the spindle partially introduced into the said seat, in an axial position such that the crank does not interfere with the said abutment shoulder, the slot is already engaged by the said second end of the coil spring.

b 17
2. A device according to Claim 1, characterised by the fact that the said coil spring is a double spiral spring formed by two wires wound coaxially with the turns adjacent one another.

is
3. A device, according to Claim 1 or Claim 2, characterised by the f act that the said coil spring is mounted externally on a centring bush fitted externally with clearance on a first end of the said spindle, provided with the said control crank; the said centring bush cooperating with at least one portion of an internal surface of the said sleeve portion of the body.
4. A device according to Claim 3, characterised by that f act that the said centring bush comprises a pair of opposite bushes axially snap engaged head to head, each of which is provided externally with respective radial centring teeth f or the said coil spring; this latter being clamped between the said control crank of the spindle and the f lange portion of a f irst of the said bushes opposite the said control crank, which is in turn clamped between an axial shoulder of the control spindle and a locking element mounted f ixedly to the control spindle and shaped in such a way as to be adapted to function as a gripping point for an automatic manipulator.

18
5. A device according to Claim 4, characterised by the fact that a pulley sector is carried on the said control crank, adapted to receive a crank control cable, a second of the said bushes being fixedly coupled to the said pulley sector in such a way that the spindle with the control crank, spring and the said centring bush form a self-supporting unit which can be preassembled before insertion of the said spindle into the seats of the said body.
6. A device according to any preceding claim, characterised by the fact that a second end of the said spindle opposite the said first end carries a second biasing coil spring mounted on a second centring bush which is mounted axially and angularly fixed to the spindle; the said second spring and second bush being housed within a second of the said seats def ined by a second sleeve portion of the said body coaxial and opposite to the first, comprising a second longitudinal slot open towards a respective mouth of the second seat and which is slidably engaged by a first end of the said second spring.
7. A device according to Claim 6, characterised by the f act that the said second spring is fixed to the said second bush in such a way as to form with it a unit which can be preassembled; the bush comprising a sleeve portion 19 and a terminal flange portion axially from which project two semi- circular concentric ribs externally of the sleeve portion terminating with respective diametrically opposite hooked ends facing towards the flange portion, and the spring being fitted onto the said ribs in abutment against the flange portion, and including a second substantially omega shaped end which is inserted, through respective radial spaces defined between the said ribs, into an annular seat defined by this and the sleeve portion.
8. A device according to any preceding claim characterised by the fact that the said spindle includes a central cylindrical abutment of constant, entirely ground diameter and on opposite ends of which are mounted, with an interference fit, respective rolling element bearings of sealed type; the said bearings being housed in the support seats f or the spindle formed by the said body, a first with an interference fit and a second with a radial clearance such as to permit relative axial movements between the seat and bearings: the said second bearing clamping a sealing element against an axial shoulder of a respective seat, the sealing element being inserted with interference into the seat itself.
9. A fuel supply device, in particular a carburettor or butterfly body of a heat engine fuel injection system, r substantially as described with reference to the attached drawings.