FR3059069B1 - METHOD FOR MAKING A VALVE BODY AND CORRESPONDING VALVE - Google Patents

Abstract

The present invention relates to a method for producing a valve body (1) for fluid dosing, in particular for a combustion engine, comprising the following steps: - placing a metal insert (2) in a mold (3) of the body of valve, - Position a retaining pin (4) in a housing (5) of the insert (2), - Inject plastic material into the mold (3) so as to at least partially cover the metal insert (2). ) of plastic material, - machining at least a portion of a surface of the housing (5) of the insert (2) to obtain a predetermined shape.

Description

METHOD FOR MAKING A VALVE BODY AND CORRESPONDING VALVE

The present invention relates to a method for producing a valve body, in particular a combustion air flow control valve supplying an automobile heat engine.

It is known to control the combustion air flow of a heat engine by a flow control valve made entirely of plastic. Compared with solutions using a metal valve, this solution makes it possible to obtain a lighter part, with a lower cost price. One difficulty is to guarantee the precision and stability of the dimensions of the combustion air flow duct. Indeed, the injection molding does not always achieve the desired level of dimensional accuracy. In addition, most plastics have dimensions that change with temperature, or with ambient humidity.

In order to avoid this drawback, it is also known to produce the combustion air duct in a metallic material, then to mold a plastic material around this metal insert in order to make the body of the valve. It is said that the valve body consists of an overmolded insert. When the valve is in the minimum flow position, the movable flap for controlling the air flow rests against the wall of the duct. The tightness of the valve therefore depends on the precision of the contact between the flap and the duct. By machining the surface of the metal insert, it is possible to obtain a good dimensional accuracy of the duct, and thus a low level of leakage of the valve, while enjoying the advantages of plastic in the other parts of the valve.

Machining, generally cylindrical, is thus performed on the inner surface of the insert. When the plastic is overmolded on the insert, compressive forces are applied to the insert, which tends to deform it. These deformations degrade the precision of the contact between the conduit and the shutter, and therefore deteriorate the seal of the valve. The object of the present invention is to provide a valve in which the duct surface is not deformed by the internal stresses resulting from the molding of the plastic material on the insert. A second aspect of the invention is to guarantee the accuracy of the positioning of the intermediate shaft guiding a gear gearing the rotation of the electric motor driving the flap of the valve. For this purpose, the invention proposes a method for producing a fluid metering valve body, in particular for a combustion engine, comprising the following steps:

Arrange a metal insert in a valve body mold, (step 50)

Position a holding pin in a housing of the insert, (step 51)

Injecting plastic material into the mold so as to at least partially cover the metal plastic insert, (step 52)

Machining at least a portion of a surface of the housing of the insert to obtain a predetermined shape, (step 53) The insert being machined after the plastic injection step, the deformations generated by the constraints related to the cooling of the injected plastic material are eliminated. The accuracy of the shape obtained is thus improved.

Preferably, the positioning housing of the holding pin in the insert is in the form of a truncated cone extending along an axis.

The holding pin, also of frustoconical shape, and allows to naturally center the insert on the holding pin.

More preferably, the angle between the axis of the truncated cone and a generator of the truncated cone is between 1 ° and 10 °.

This value range makes it possible, at the end of the molding operation, to disengage the pin from the insert without risk of jamming due to the friction between the pin and the insert.

According to one embodiment, the holding pin of the insert holds the insert against a stop of the mold, the stop being in contact with at least a portion of an axial surface of the insert.

The frustoconical pin introduced into the insert plates the insert against the abutment of the mold, which ensures precise positioning of the insert during the molding operation. The dimensions of the molded parts are thus little dispersed, that is to say, very repeatable from one manufactured part to another.

According to one embodiment, the injection step covers at least a portion of the axial surface of the insert with plastic.

The injected plastic is thus in contact with several sides of the insert, which improves the cohesion between the metal insert and the plastic covering it.

According to one embodiment, the method comprises, after the step of injecting the plastic into the mold, the step:

Machining in the metal insert a passage opening of a rotating shaft,

Machining in the metal insert a cylindrical housing arranged to receive a guide bearing of the rotation shaft.

The machining being performed after the step of injecting the plastic, there is no deformation of the machined areas due to the constraints related to the injection of the plastic material. The positioning accuracy of the guide bearing (s) of a rotary shaft is improved. Similarly, the positioning accuracy of the rotary shaft is improved, which improves the quality of the finished product.

According to one embodiment, the method comprises, after the step of injecting the plastic into the mold, the step:

Machine a portion of the metal insert protruding from the plastic material to form a cylindrical shape.

The cylindrical shape is formed on the outer periphery of the projecting portion. The cylindrical shape obtained by the machining phase is precisely localized and can serve as a reference for the positioning of the components assembled on the molded product.

According to one embodiment, the method comprises after the machining step of the cylindrical shape: Machining in the cylindrical shape a transverse groove.

The transverse groove can be used to provide a seal and thus seal the machined cylindrical portion. The invention also relates to a valve body obtained by a method as previously described.

Advantageously, a machined surface of the housing at least partially defines a fluid flow conduit in the valve body.

The frustoconical shape given to the inner part of the insert, in order to allow effective maintenance of the retaining pin, is eliminated by machining after the molding operation. The machined surface is in contact with the fluid passing through the valve body, i.e., it forms a portion of the fluid flow conduit.

Advantageously, the machined surface defining at least in part the fluid flow conduit is cylindrical.

According to one embodiment, the valve body comprises a movable shutter disposed in the conduit and arranged to control a flow of fluid in the conduit, the movable shutter being located opposite the machined surface of the flow conduit when the shutter is in the position of minimum fluid flow in the conduit.

According to one embodiment, the shutter is rotatable about a rotation shaft.

The angular position of the shutter thus makes it possible to control the passage section of the fluid circulation duct and consequently to control the flow rate.

Preferably, the movable shutter engages the machined surface of the flow conduit when the shutter is in the minimum fluid flow position in the flow conduit.

The minimum flow position is obtained when the rotary shutter rests on the duct wall. The rotary shutter then completely closes the duct. Nevertheless, there remain areas of leakage, corresponding in particular to areas where there is clearance between the shutter and the duct due to geometric defects affecting one or the other of the two parts. A game is also necessary to avoid jamming the shutter against the pipe. By machining the rotary shutter before assembly, and also machining the insert, it is possible to obtain a very small clearance between the two parts and therefore a very low level of residual leakage.

According to one embodiment, the valve body comprises a mechanism for driving the movable shutter, the drive mechanism comprising at least one gear rotating about an intermediate axis, the intermediate axis being arranged in a housing made in the metal insert. The movable shutter of the valve body is actuated via an electric motor and a gearbox to increase the rotation of the electric motor. At least one of the gearing participating in the reduction gear rotates on an intermediate axis of rotation. The fact of arranging the intermediate axis in a housing forming part of the metal insert makes it possible to ensure precise positioning of the intermediate axis. This ensures the inter-axis between the gears and therefore a good mechanical performance of the drive mechanism.

According to one embodiment, the housing of the intermediate axis is machined. The positioning of the housing can be assured precisely.

According to one embodiment, the intermediate axis is fitted into the housing of the intermediate axis. The holding of the intermediate axis in the valve body is thus provided without adding additional part.

Alternatively, the intermediate axis is floating in the housing of the intermediate axis. The mounting of the axis is thus performed without any tools.

According to one embodiment, the intermediate axis is knurled. The knurling of the surface of the axis makes it possible to improve the tear resistance of the axis of its housing.

According to one embodiment, the insert is obtained by molding. The insert can thus be manufactured at low cost.

Advantageously, the plastic portion covering the insert forms on either side of the insert a duct portion is connected with the duct portion of the insert.

The plastic material thus marries the insert on several faces.

According to one embodiment, the surfaces of the pipe portions are connected continuously.

In this case, the fluid flow duct consists of several sections connected in a continuous manner, which minimizes the pressure losses of the fluid flow.

According to one embodiment, the surfaces of the conduit portions are connected with a discontinuity, the metal portion being protruding from the plastic portion.

It is thus possible to perform a machining of the metal part without damaging the plastic part that has been molded.

According to one embodiment, the insert has a generally hollow cylinder shape, comprising two parts projecting from an outer lateral surface arranged to receive the rotation shaft of the movable shutter.

The two protruding portions of the outer lateral surface of the insert can receive the shutter rotation shaft and provide precise guidance of the shaft.

Advantageously, the rotating shaft of the movable shutter and the housing of the intermediate axis extend along parallel axes.

The mechanical efficiency of the gears is thus improved.

According to one embodiment, the insert has an outgrowth protruding from the outer lateral surface, the protuberance being arranged to receive the housing of the intermediate axis.

According to one embodiment, the protrusion comprises a hole.

The hole allows the passage of a screw for fixing the valve body if necessary.

Preferably, the insert has a circular rib projecting from the outer lateral surface of the insert.

The rib makes it possible to increase the contact surface between the insert and the injected plastic, and thus to improve the resistance of the connection between the two elements.

According to one embodiment, the circular rib has orifices extending in a direction parallel to the axis of the duct.

Advantageously, the orifices comprise a chamfer.

The orifices facilitate the flow of the plastic during the molding operation.

According to one embodiment, the distance between two consecutive orifices is constant.

According to one embodiment, the distance between two consecutive orifices is different from the distance between two other consecutive orifices.

In other words, the spacing between the orifices is not necessarily regular. The orifices can thus be arranged in areas where access tools is easier.

According to one embodiment, the periphery of the circular rib has recesses.

The recesses make it possible to reduce the size of the valve body in the recessed areas, and facilitate the screw driver passages for fastening the component to the motor.

According to one embodiment, an edge of the recesses has an arcuate shape. The invention also relates to a control valve of a fluid flow, comprising a valve body as described above, wherein the fluid passing through the valve supplies combustion gas to a combustion engine. The invention described provides an oxidizing gas supply valve having a low level of leakage. The control of the combustion air flow sent to the engine is thus improved.

According to one embodiment, the fluid passing through the valve comprises recirculated exhaust gas between an exhaust circuit and an intake circuit of the combustion engine.

This architecture corresponding to the so-called "low pressure" architecture, in which a portion of the exhaust gases are reintroduced at the intake of the engine upstream of the metering valve of the combustion air flow of the engine. Other characteristics and advantages of the invention will appear on reading the detailed description of the embodiments given by way of non-limiting examples, accompanied by the figures below:

FIG. 1 represents a perspective view of a metal insert according to an embodiment,

FIG. 2 schematically illustrates, in section, the plastic injection operation on an insert to obtain a valve body,

FIG. 3 schematically illustrates, in section, the machining operation following the plastic injection operation,

FIG. 4 is a view of a valve body obtained by carrying out the method according to the invention,

FIG. 5 illustrates is a perspective view of a combustion air flow control valve of a combustion engine,

FIG. 6 represents a perspective view of a metal insert according to an embodiment different from that of FIG. 1,

FIG. 7 is a block diagram illustrating the various steps of the method according to the invention.

In order to facilitate the reading of the figures, the different elements are not necessarily represented on the scale.

FIG. 5 shows a fluid flow control valve 30 comprising a valve body 1 in which the fluid flowing through the valve supplies combustion engine with a combustion engine. The combustion engine can propel a motor vehicle.

The valve body 1 comprises a fluid circulation duct, and a movable shutter 12. The shutter 12 is rotatable about a rotation shaft 13. The shutter 12, here a shutter, is on the example of Figure 5 inserted in a slot of the shaft 13 and fixed to the shaft 13 by screws.

An electric motor 29, arranged in a housing of the valve body 1, makes it possible to control the position of the flap 12. The electric motor 29 actuates the flap 12 via a drive mechanism 14.

For this, the valve body 1 comprises a drive mechanism 14 of the movable shutter 12, the drive mechanism 14 comprising at least one gear 15 rotating about an intermediate axis 16, the intermediate axis 16 being disposed in a housing 17 formed in the metal insert 2. FIG. 4 illustrates the valve body 1 equipped with the intermediate pin 16 disposed in the housing 17. FIG. 5 illustrates the complete actuating mechanism, with the pinion 31 of the motor 29 which drives an intermediate wheel 15, itself causing an angular sector 32 integral in rotation with the shaft 13. The angular sector 32 comprises a magnet 33, the magnetic field is analyzed by a position sensor, not shown. The valve 30 comprises a cover, not shown, for closing the volume occupied by the control mechanism. The hood also receives the position sensor (s) of the rotation shaft 13 of the shutter 12 and the electrical connector making it possible to electrically power the motor 29.

An electronic control unit, for example that controlling the operation of the heat engine, controls the power supply current of the electric motor of the valve to ensure the desired degree of opening to the flap, and thus ensure the desired flow of oxidant gas .

The valve body of the valve of FIG. 5 is detailed in FIG. 4.

The valve body 1 is formed of a metal insert 2 on which a plastic material has been overmolded. The insert 2 is thus surrounded by a plastic part 18.

The hollow portion of the valve body 1 forms a fluid flow conduit. Part 19 of the circulation duct is formed of plastics material. Part 11 of the circulation duct is formed by the inner surface of the insert 2.

More specifically, the plastic portion 18 covering the insert 2 forms on either side of the insert 2 a duct portion 19 connecting with the duct portion 11 of the insert 2.

In this embodiment, the surfaces of the conduit portions are connected with a discontinuity, the metal portion being protruding from the plastic portion. It is thus possible to perform a machining of the metal part without damaging the plastic part that has been molded.

The duct portion 11, formed by the insert, is a machined surface 10 of the insert 2.

In the example, the machined surface 10 defining at least in part the fluid flow conduit 11 is cylindrical.

The valve body 1 comprises a movable shutter 12 disposed in the duct 11 and arranged to control a flow of fluid in the duct 11, the movable shutter 12 being situated facing the machined surface 10 of the flow duct when the shutter is in the position of minimum fluid flow in the conduit 11.

More specifically, the movable shutter 12 comes into contact with the machined surface 10 of the flow duct 11 when the shutter 12 is in the minimum fluid flow position in the flow duct 11.

The edge of the flap 12 has a shape complementary to the shape of the duct 11. The shutter 12 thus completely closes the duct when the shutter 12 rests on the machined surface 10. In order to avoid jamming of the flap, a game is present between the periphery of the flap and the surface of the duct. This game is at the origin of a leak rate, and must be minimized.

FIG. 1 details the constitution of the insert 2. The insert 2 has the general shape of a hollow cylinder, comprising two parts 20a, 20b projecting from an external lateral surface 21 and arranged to receive the rotation shaft 13 of the movable shutter 12.

The two parts 20a, 20b protruding from the outer lateral surface of the insert receive the guide bearings of the rotation shaft 13 of the movable shutter 12. The insert 2 has an outgrow 22 protruding from the outer lateral surface 21 , the protrusion 22 being arranged to receive the housing 17 of the intermediate axis 16.

The housing 17 of the intermediate axis is machined. The intermediate axis 16 is fitted into the housing 17. The rotation shaft 13 of the movable shutter 12 and the housing 17 of the intermediate shaft 16 extend along parallel axes. By machining the housing 17, the spacing between the intermediate wheel 15 and the angular sector 32 integral with the rotation shaft 13 of the flap 12 is precisely controlled. It is the same for the distance between the intermediate wheel 15 and the gear 31 of the electric motor 29. The general operation of the drive mechanism 14 of the flap 12 is optimized. Wear and friction are minimized.

In the example described in Figure 1, the protrusion 22 has a hole 23. This hole 23 allows the passage of a fixing screw of the valve body 1 of the engine intake manifold, not shown. The insert 2 has a circular rib 24 projecting from the outer lateral surface 21 of the insert 2.

The rib makes it possible to increase the contact surface between the insert and the injected plastic, and thus to improve the resistance of the connection between the two elements.

The circular rib 24 has orifices 25 extending in a direction parallel to the axis of the conduit 11. During the molding operation, the injected plastic material passes through the orifices 25. These orifices are therefore filled with plastic on the body molded valve.

The distance between two consecutive orifices 25 is constant.

The periphery 26 of the circular rib 24 has recesses 27.

The recesses make it possible to reduce the bulk of the valve body in the recessed areas. In the example of Figure 1, the edge of the recesses 27 has a shape of an arc.

Preferably, the insert 2 is obtained by molding. The insert 2 may be aluminum alloy.

The method of producing the valve body as described above will now be detailed. The method for producing a valve body 1 for fluid dosing, in particular for a combustion engine, comprises the following steps:

Arrange a metal insert 2 in a mold 3 of the valve body, (step 50)

Position a holding pin 4 in a housing 5 of the insert 2, (step 51)

Injecting plastic material into the mold 3 so as to at least partially cover the metal insert 2 of plastic, (step 52)

Machining at least a portion of a surface of the housing 5 of the insert 2 to obtain a predetermined shape, (step 53)

Figure 2 shows schematically the steps 50 to 52. The insert 2 is disposed in the mold 3, consisting of several contiguous elements. In order to ensure the precise positioning and maintenance of the insert 2 in the mold 3, a holding pin 4 is inserted into a hollow housing 5 of the insert 2. Once the insert 2 is positioned and held in the mold 3, the molten plastic material is injected into the hollow cavity of the mold 3. In FIG. 2, the injection channels of the molten plastic material have not been shown.

The housing 5 for positioning the holding pin 4 in the insert 2 has the shape of a truncated cone 6 extending along an axis D.

The pin 4, also frustoconical, has a shape complementary to the shape of the housing of the insert and thus allows to naturally center the insert 2. The angle A between the axis D of the truncated cone and a generator 7 of the trunk cone 6 is between 1 and 10 °. This value range makes it possible, at the end of the molding operation, to disengage the pin from the insert without risk of jamming due to the friction between pin and insert.

The holding pin 4 of the insert 2 holds the insert 2 against a stop 8 of the mold 3, the stop 8 being in contact with at least a portion of an axial surface 9 of the insert 2.

The frustoconical pin introduced into the insert 2 plates the insert against the abutment 8 of the mold 3. The insert 2 is thus positioned precisely, both in the axial direction of the truncated cone and in the radial direction. In addition, the insert is held in place against the stop 8. This ensures a small variability of the dimensions of the parts obtained by the method of producing the valve body. The injection step covers with plastic at least a portion of the axial surface 9 of the insert.

The injected plastic is thus in contact with several faces of the insert 2, which allows good cohesion between the metal insert 2 and the plastic covering it.

After the injection step, the mold 3 is opened after a delay for cooling the injected material, and the valve body 1 is recovered. A finishing treatment can be applied to eliminate molding burrs. Step 53 consists of machining at least a portion of the surface of the housing 5 against which the pin 4 was supported. As shown schematically in Figure 3, the portion 28 of the insert is removed by machining. The machining operation reveals a machined surface 10. The machined surface 10 of the housing 5 at least partly defines a fluid flow conduit 11 in the valve body 1. The machining tool is introduced by the opening of the fluid flow conduit. In the example of Figure 3, the machining only concerns the portion 28 of the metal insert, and the plastic portion is not modified.

In the example of FIG. 3, the machined part extends from one axial end of the insert 2 to the other axial end of the insert 2. In this case, the part of the fluid circulation duct in the insert 2 consists entirely of a machined surface.

On the assembled valve, the movable shutter 12 bears on a portion of the machined surface 10 when the shutter is in the minimum flow position of the valve.

The cooling of the plastic material surrounding the insert 2 generates internal stresses in the valve body 1. These internal stresses tend to deform the inner surface of the insert 2. These deformations have no significant influence on the However, the contact between the inner surface of the duct and the shutter, when that is in the closed position, is degraded. As the deformations of the inner surface of the insert prevent the shutter 12 from perfectly matching the shape of the conduit, the leakage rate tends to increase.

By machining the insert after the molding operation, the deformed portion of the insert is removed. The method according to the invention thus makes it possible to obtain very precisely the desired shape for the inner surface of the insert. It is thus possible to reduce the level of leakage with respect to a valve according to the state of the art.

Preferably, the machining of the insert 2 is performed without machining the plastic material surrounding the insert.

According to one embodiment, the method comprises, after the step of injecting the plastic into the mold, the step:

Machine in the metal insert 2 a passage opening 34 of a rotation shaft 13,

Machine in the metal insert 2 a cylindrical housing 35 arranged to receive a guide bearing of the rotation shaft 13.

FIG. 6 shows an insert thus machined. For reasons of legibility, the plastic material surrounding the insert is not shown in FIG.

The machining of the passage orifices 34 of the shaft 13 as well as the housing 35 of the bearings of the shaft 13 being made after the step of injecting the plastic material, there is no deformation of the machined zones. because of the constraints related to the injection of the plastic material. The accuracy of the positioning of the guide bearings of the shaft 13 is improved. Similarly, the positioning accuracy of the shaft 13 is improved. Games can be reduced, which in particular reduces the level of leakage between the rotation shaft 13 and the body.

According to one embodiment, the method comprises, after the step of injecting the plastic into the mold, the step:

Machining a portion of the metal insert 2 protruding from the plastic material so as to form a cylindrical shape 37.

The machined portion is a portion of the portion 20a of the insert 2. The machining is performed on the outer periphery of the projecting portion 20a. The cylindrical shape 37 obtained by the machining phase is precisely localized and can serve as a reference for positioning the components assembled on the molded product. This machining can thus simplify the assembly operation of the valve and reduce the positioning dispersions.

According to one embodiment, the method comprises after the machining step of the cylindrical shape: Machining in the cylindrical shape 37 a transverse groove 38.

The transverse groove 38 can be used to provide a seal and thus seal the machined cylindrical portion.

According to embodiments not shown, the method of producing the valve body and the corresponding valve body may also comprise one or more of the following characteristics, considered individually or in combination with one another:

The fluid passing through the valve may comprise recirculated exhaust gas between an exhaust circuit and an intake circuit of the combustion engine.

This architecture corresponds to the so-called "low pressure" exhaust gas recirculation architecture, in which a portion of the exhaust gases are reintroduced at the intake of the engine upstream of the air flow metering valve. engine. The intermediate axis 16 can be mounted floating in the housing 17 of the intermediate shaft 16. The intermediate axis 16 can be knurled. The insert 2 can be obtained by machining a metal block.

The surfaces of the duct portions 11, 19 can be connected continuously.

The distance between two consecutive orifices may be different from the distance between two other consecutive orifices.

The orifices 25 of the insert 2 may comprise a chamfer.

Of course, the invention is not limited to the embodiments described and illustrated, which have been given only as examples.

Claims (9)

A method for producing a valve body (1) for fluid dosing, in particular for a combustion engine, comprising the following steps: placing a metal insert (2) in a mold (3) of the valve body, 50) Position a holding pin (4) in a housing (5) of the insert (2), (step 51), the holding pin (4) of the insert (2) holding the insert (2) against a stop (8) of the mold (3), the abutment (8) being in contact with at least part of an axial surface (9) of the insert (2), Injecting plastic into the mold (3) so as to at least partially cover the metal insert (2) of plastic, (step 52) machining at least a portion of a surface of the housing (5) of the insert (2) to obtain a predetermined shape, (step 53) 2. Method according to the preceding claim, wherein the housing (5) for positioning the holding pin (4) in the insert (2) has the shape of a truncated cone (6) extending along an axis. (D). Valve body (1) obtained by a method according to one of the preceding claims, wherein the insert (2) has a circular rib (24) projecting from an outer lateral surface (21) of the insert ( 2). 4. Valve body (1) according to the preceding claim, wherein a machined surface (10) of the housing (5) at least partially defines a conduit (11) of fluid flow in the valve body (1). 5. Valve body (1) according to claim 3 or 4, comprising a drive mechanism (14) of the movable shutter (12), the drive mechanism (14) comprising at least one gear (15) rotating around an intermediate axis (16), the intermediate axis (16) being disposed in a housing (17) formed in the metal insert (2). 6. Valve body (1) according to the preceding claim, wherein the housing (17) of the intermediate axis is machined. 7. Valve body (1) according to one of claims 3 to 6, wherein a plastic portion (18) covering the insert (2) forms on either side of the insert (2) a portion conduit (19) connecting with the conduit portion (11) of the insert (2). 8. Valve body (1) according to one of claims 3 to 7, wherein the circular rib (24) has orifices (25) extending in a direction parallel to the axis of the conduit. '' 9. valve (30) for controlling a fluid flow, comprising a valve body (1) according to one of claims 3 to 8, wherein the fluid flowing through the valve supplies combustion gas combustion engine.