WELDING A THROTTLE PLATE TO A THROTTLE SHAFT ULTRASONICALLY

Abstract: A throttle plate-throttle shaft construction (10) is formed by molding both components from composite plastic, the shaft (12) having integral bosses (16) which are received in holes (22) formed in the throttle plate (18). The bosses (16) are ultrasonically staked to lock the throttle plate (18) onto the throttle shaft.

Description: ELDING A THROTTLE PLATE TO A THROTTLE SHAFT ULTRASONICALLY BACKGROUND OF THE INVENTION This invention concerns a throttle valve construction for automotive engines. Throttle valves typically comprise a throttle plate disc attached to a throttle shaft mounted extending across the bore of a throttle body receiving inlet air flow from an intake manifold. The throttle shaft is rotated to control the air flow by variably restricting the throttle bore with the throttle plate by rotating the throttle shaft. Conventional practice has been to construct both the throttle blade and shaft of metal, attaching the plate to the shaft with small screws passing through holes in the plate and received into small threaded holes in the shaft. These small screws can become loose and get drawn into the engine, creating severe mechanical problems. The use of separate fasteners also increases manufacturing costs. It is the object of the present invention to provide an improved throttle shaft and plate construction which eliminates separate fasteners such as the small screws described above. SUMMARY OF THE INVENTION The above object and others which will become apparent upon a reading of the following specification and claims are achieved by a throttle valve construction in which the throttle shaft component is molded from a plastic composite material, and is formed with a flattened side against which one side of the throttle plate is held. One or more bosses integrally formed projecting from the flattened side of the throttle shaft, are received into corresponding holes in the throttle plate which is also molded from a composite plastic. The bosses project above the throttle plate and are heat staked, preferably ultrasonically, to securely attach the plate to the throttle shaft. DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of a throttle shaft component and a throttle plate to be assembled thereto. Figure 2 is an enlarged fragmentary view of a lengthwise section taken through the assembled throttle shaft and plate prior to heat staking of the bosses formed on the throttle shaft. Figure 3 is an enlarged fragmentary view of a lengthwise section taken through the assembled throttle shaft and plate, showing the bosses formed on the shaft heat staked to lock the plate onto the shaft. Figures 4 and 5 are fragmentary lengthwise sectional views of the throttle plate and shaft connected by an alternate form of heat staked connection. DETAILED DESCRIPTION In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 1 1 2, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. Referring to the drawings, a molded throttle shaft component 10 is shown, which includes the throttle shaft 1 2 itself. The shaft 1 2 is integrally formed with other features of the throttle shaft component 1 0, such as the spring retainer and lever indicated generally at 20. The throttle shaft component maybe formed by injection molding of the part from a composite plastic material. The plastic material should be selected so as to allow an efficient ultrasonic staking operation as described herein. Suitable semicrystalline materials include LCP (liquid crystal polymers) or polyphenylene (PPS) filled with glass or mineral fibers. The throttle shaft 12 has a recess formed on one side to create a blade mounting flat 14, from which projects perpendicularly a pair of spaced apart cylindrical bosses 1 6, molded integrally with the shaft component 10. The bosses 1 6 should be of a height low enough as to lie within the diameter of the throttle shaft 12 thereby allowing assembly by insertion of the shaft 1 2 through an opening in the throttle body (not shown) in which the throttle shaft component 10 is installed prior to heat staking of the bosses 1 6. The throttle plate 1 8 comprises a disc also molded of a composite plastic material, such as the PPS or LCP materials described above, and having a pair of spaced apart holes 22 formed therein. The holes 22 are spaced apart and sized to receive the bosses 16 when the plate 1 8 is placed on the surface 14. The holes 22 may be chamfered on the side of the throttle plate 1 6 away from the throttle shaft 12, as shown in Figure 2, to improve the strength of the connection produced when the bosses 1 6 are ultrasonically staked. A clearance space between each of the bosses 1 6 and a respective one of the holes 22 allows alignment of the throttle plate 1 8 as necessary within the throttle body air induction bore prior to the staking operation. When proper alignment has been achieved, the bosses 1 6 are heat staked ultrasonically causing portions thereof to melt and reflow to completely fill the chamfered hole sides, including the clearance gap and the chamfer space as shown in Figure 3. Upon cooling, the staked head 16A of the bosses 1 6 securely locks the throttle plate 1 8 onto the throttle shaft 12. Conventional ultrasonic staking techniques and equipment can be employed in the process and details of this technique and equipment are not set forth herein inasmuch as these are well known in the art. Suffice it to say that a horn is used to engage the head 1 6A of each boss 16, and mechanical vibrations set up in the horn are transmitted into the head 1 6A of the boss 1 6 causing localized melting and reformation as described above. The chamfering allows smooth orientation of the fibers in extending outwardly to the larger diameter head 1 6A formed by the staking if the entire boss is completely remelted, such that this technique is a preferred way of conducting the staking operation. A less smooth orientation results if only the top of the boss is remelted during staking. A smooth fiber orientation as well as the increased area of the chamfer provides greater strength in the head of the bosses. Straight holes 24 may also be used for some applications as shown in Figures 4 and 5. Ultrasonic staking of the bosses 26 melts the material comprising the head and lower portions of the boss to completely fill the clearance space and flow over the adjacent surface 28 of the throttle disc 1 8B to lock the same to the throttle shaft 1 2B, as before. Accordingly, a secure high strength locking attachment of the throttle plate to the throttle shaft is provided without separate fasteners to achieve the object of the present invention.

Claims: C AI S 1 . A throttle shaft-throttle plate assembly comprising: a throttle shaft component of composite plastic having a throttle shaft portion formed with a flat surface, at least one boss projecting from said surface; a throttle plate, comprising a disc of plastic composite formed with at least one hole, said throttle plate having one side positioned abutting against said throttle shaft surface with said boss projecting through said hole; said boss heat staked over said throttle plate to lock said throttle plate to said throttle shaft. 2. The assembly according to claim 1 wherein a pair of spaced bosses project from said throttle shaft flat surface, and a pair of correspondingly located holes are formed in said throttle plates, and wherein said holes in said throttle plate are chamfered on a side of said throttle plate away from said throttle shaft. 3. A method of constructing a throttle shaft-throttle plate assembly, comprising the steps of: molding a throttle shaft component from composite plastic material, said component including an elongated shaft having a flat formed on one side, a plurality of bosses projecting out of said shaft flat surface; molding a throttle plate from composite plastic material formed with a plurality of holes located and sized to be fit over said bosses; assembling said throttle plate onto said bosses and against said throttle shaft flat surface; and, heat staking said bosses over said throttle plate to lock said throttle plate to said throttle shaft. 4. The method according to claim 3 wherein said step of molding said throttle shaft includes the step of molding said bosses to be of a height lying within a diameter of said throttle shaft prior to heat staking. 5. The method according to claim 3 wherein said step of molding said throttle plate includes the step of molding said holes in said throttle plate to be chamfered on a side of said throttle plate away from said throttle shaft surface. 6. The method according to claim 5 wherein said step of staking said bosses comprises the step of ultrasonically staking said bosses so as to remelt portions of said bosses below said chamfer during said staking step to create a smooth orientation of fibers extending into said chamfer. 7. The method of claim 3 wherein in said step of molding said throttle plate, said holes are formed of a sufficiently large diameter to create a clearance space with said bosses, and further including the step of assembling said throttle plate and shaft into a throttle body and aligning said throttle plate prior to staking said bosses.

Inventors: BECKER CHRISTINE CYNTHIA, BECKER, CHRISTINE, CYNTHIA
Applicants: SIEMENS ELECTRIC LTD, SIEMENS ELECTRIC LIMITED
Application year: 1997
Main classification: B29C65
IPC codes: B29C65, F02D9, F16K1