Method of securing intake tubes in intake manifold

A method of securing intake tubes in an intake manifold is provided in which leakage of brazing material from the joint between the intake tubes and the intake tube mounting rings is prevented. For securing each intake tube in the intake manifold, the intake tube 3 is fitted into the intake tube mounting ring 5. Then, a jig 13 of a tubular shape is inserted into insert areas of the intake tube 3 and the intake tube mounting ring 5. The jig 13 includes separate sections 16 defined by slits extending to a predetermined length in parallel to the axis and has a plurality of projections 19 and 20 provided on the outer side of the separate sections 16 thereof. A bar-like pressing tool 14 reduced in the diameter towards its front end is inserted into the interior of a tubular shape of the peen locking jig 13, and it is then advanced relatively towards the insert area by the action of pressing means. As a result, the projections 19 and 20 are dislocated radially and press the outer side of the intake tube 3 against the inner side of the intake tube mounting ring 5 to join each other by the effect of plastic deformation.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an intake manifold for an engine and
 particularly, a method of securing intake tubes in an intake manifold.
 2. Description of the Related Art
 Intake manifolds for combining intake tubes to a multi-cylinder engine to
 groups or a single bundle are arranged to prevent interference between the
 intake tubes and to provide uniform distribution of intake air.
 A known intake manifold 1 includes, as shown in FIG. 8, a collector 2
 formed of aluminum die-casting, a plurality of intake tubes 3 made of
 aluminum pipe, and an intake tube mount 4 formed of aluminum die-casting
 for fixedly mounting the intake tubes 3 to the engine. The intake tubes 3
 are inserted into intake tube mounting rings 5 formed on the collector 2
 and the intake tube mount 4 as shown in FIG. 9 and fixedly joined to the
 intake tube mounting rings 5 by point welding such as spot welding at
 points A or A' on the periphery shown in FIG. 9.
 In such a conventional method of securing the intake tubes 3 to the intake
 tube mounting rings 5, brazing in a furnace for jointing the intake tube
 mount 4 with the intake tube mounting rings 5 may produce a leakage of
 brazing material from the points A of spot welding between the intake
 tubes 3 and the intake tube mounting rings 5. Accordingly, an extra
 amendment for the brazing is needed and the leakage of brazing material
 runs out to a portion B of the intake tube mounting ring 5, thus resulting
 in loss of the brazing material. This may cause a sealing failure when the
 intake manifold 1 is installed in the engine. Also, the point welding such
 as spot welding may be likely to have the intake tubes 3 joined to the
 intake tube mounting rings 5 in tilted state as denoted by 3' in FIG. 9.
 SUMMARY OF THE INVENTION
 The present invention is intended to eliminate the foregoing problems and
 its object is to provide a method of securing the intake tubes in an
 intake manifold with producing no leakage of brazing material from joint
 interface between the intake tubes and the intake tube mounting rings.
 For eliminating the foregoing problems of the prior art, a method of
 securing intake tubes in an intake manifold according to the present
 invention is provided comprising the steps of: inserting one end of an
 intake tube into a corresponding intake tube mounting ring; inserting into
 insert areas of the intake tube mounting ring and the intake tube a jig of
 a tubular shape which includes separate sections defined by parallel slits
 extending to a predetermined length along the axis and has a plurality of
 projections on the outer side of the separate sections thereof; inserting
 into the interior of a tubular body of the jig a pressing tool which is a
 bar reduced in the diameter towards its front end; and driving the
 pressing tool to advance relative to the insert areas using a pressing
 means so that the projections of the jig move radially and causes the
 outer side of the intake tube to press against the inner side of the
 intake tube mounting ring, whereby the intake tube can be joined to the
 intake tube mounting ring by its plastic deformation.
 Accordingly, while leakage of the brazing material can be prevented by some
 of the projections, the joint between the intake tubes and the intake tube
 mounting rings can be ensured by the other of the projections.
 It may be arranged that the projections of the jig comprise spot
 projections and an annular projection and the spot projections are used
 for joining the intake tube to the intake tube mounting ring while the
 annular projection is used for the plastic deformation to prevent leakage
 of brazing material. In this case, the jig has a plurality of (for
 example, three) spot projections and an annular projection spaced from the
 spot projections which act in combination to prevent the intake tubes from
 being joined at tilted state to the intake tube mounting rings.
 Therefore, the intake tubes can be reliably prevented from being joined at
 tilted state to the intake tube mounting rings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 An embodiment of the present invention will be described in connection with
 a method of securing intake tubes in an intake manifold 1 with reference
 to FIGS. 1 to 7. The intake manifold 1 of this embodiment is identical in
 construction to that of the prior art shown in FIG. 8 and will not be
 explained in detail.
 As shown in FIGS. 1 and 2, the intake tubes denoted at 3 are inserted into
 corresponding intake tube mounting rings 5 and fixedly joined to the same
 by brazing at points aligned along the outer side of each intake tubes 3
 to the inner side of the corresponding intake tube mounting ring 5. Prior
 to the brazing, the intake tube 3 has to be secured to its corresponding
 intake tube mounting ring 5. The securing process is commonly carried out
 using a peen locking jig 13 shown in FIGS. 5 and 6 and a pressing tool 14
 shown in FIG. 7.
 The jig 13 has a tubular shape having a plurality of slits 15 (three in
 this embodiment) provided therein at equal intervals of an angle along the
 circumference and extending in parallel to the axis up to about 1/2 of its
 length. More specifically, the jig 13 comprises three separated sections
 16. The inner side of a tubular body of the jig 13 is tapered as reduced
 in the inner diameter towards the open end 17 of the slits 15. The jig 13
 has two rows of projection 18 provided on the outer side of each section
 16 thereof which are spaced from each other along a circumferential
 direction orthogonal to the axis. One of the two rows 18 closed to the
 open end 17 of the slit 15 is a series of raised-shaped spot projections
 19 aligned at equal intervals (six in this embodiment). The other row 18
 far from the open end 17 is an annular projection 20 extending throughout
 the circumference.
 The pressing tool 14 is a bar having a diameter at the front end 21 that is
 slightly smaller than the inner diameter at the open end 17 of the slits
 15 of the jig 13. The diameter of the pressing tool 14 increases towards
 the rear end. The rear end of the pressing tool 14 is adapted for joining
 to pressing means such as a hydraulic cylinder.
 The method of securing the intake tubes 3 is now explained.
 First, the intake tube 3 is fitted into the intake tube mounting ring 5
 from above as shown in FIG. 3. Then, the jig 13 is inserted from below
 into the intake tube mounting ring 5 with its slits 15 moving into the
 interior of the intake tube 3 fitted into the intake tube mounting ring 5.
 The pressing tool 14 is inserted from below into the jig 13 with its front
 end 21 engaging the jig 13 as shown in FIG. 4. The pressing tool 14 is
 then advanced relatively towards the jig 13 by the action of a hydraulic
 cylinder not shown. As a result, the spot projections 19 and the annular
 projection 20 are dislocated radially to press the inner side of the
 intake tube 3 and develop recesses 22 in the same due to plastic
 deformation. This causes the outer side of the intake tube 3 to press
 against the inner side of the intake tube mounting ring 5, resulting in
 the joining the intake tube 3 to the intake tube mounting ring 5 (See
 FIGS. 1 and 2). At the time, the spot projections 19 prevent jerky
 movement between the intake tube 3 and the intake tube mounting ring 5 and
 thus ensures no tilting of the intake tube 3 at the joint with the intake
 tube mounting ring 5. In addition, the annular projection 20 prevents the
 brazing material applied to a location C from entering the intake tube
 mounting ring 5 and reaching at the location B.