GB2205922A

GB2205922A - Built-up liquid-cooled piston for internal combustion engines

Info

Publication number: GB2205922A
Application number: GB08810717A
Authority: GB
Inventors: Dieter Messmer
Original assignee: Mahle GmbH
Current assignee: Mahle GmbH
Priority date: 1987-06-11
Filing date: 1988-05-06
Publication date: 1988-12-21
Anticipated expiration: 2008-05-06
Also published as: JPS643252A; FR2616484B1; GB2205922B; FR2616484A1; GB8810717D0; DE3719469A1

Description

fl 1 - Title: Built-up liquid-cooled piston for internal combustion

engines 2205922

The invention. relates to-a built-up liquid-cooled piston for internal combu_st-ion enEines according to the opening statement of Claim 1.

Such a piston is known from DE-T 32 49 290. 'In this piston the piston head and the piston skirt are connected by way of a centrally arranged screw, where the screw head abuts throuE'-t--l a pack of springs on an aperture of the piston skirt and the threading of the screw is screwed into the piston head. For the one part in this embodiment; it is disadvantageous that to guarantee an adequate strength the axial wall thickness of the piston skirt, on which the screw head rests -t,--hrouE'-n- the spring pack, must be made very great, whereby the overall height of the Diston becomes very large, and for the other part the.supportinF : of the spring force and, when the enEine is in operation, also that of the inertia forces takes place on the aperture of the piston skirt, on which the spring pack rests, so that unacceptable stresses occur here and damage can occur.

It is therefore the problem of the present invention to produce a builtup liquid-cooled piston with low overall height - that is low compression height - and to improve its supporting with respect to the occurring forces.

The solution to this problem consists in accordance wth the invention in a built-up liquid-cooled piston L having the features according to the characterising part of Claim 1.

Further advantaEeous embodiments accer,,-,Jng to the invention are contai-r.ed in the Sub-Clairs.

As general prior art reference should also be made to DE-AS 22 12 922, from w11ich a built-up piston is known which is provided with a screw ring or a bolt with two opposite threadings in order to connect the piston head with the piston skirt. In this piston however the connection is rigid and not made elastic.

The Invention will be explained in greater detail by way of example with refe--ence to the drawing, which shows a detail of a Diston in accordance with the invention in sectlion.

The built-up piston 1 consists of a piston head 3 of a material capable of high loading, as regards strength, such for example as steel, which accomniodates pist-on --inEs in ring grooves 2, and of a piEton skirt 4 of an aluminium alloy. The connection of piston head 3 and piston skirt 4 takes place by means of a centrally arranged screw 5, which for the one part is in operative connection with the piston skirt 4 throuEh a spring pack 6 of dished springs 7 on a sleeve 8 screwed centrally into the piston skirt 4, and for the other iart is screwed into the piston head 3 with its threading 9, which is provided on the end opposite to the screw head 10. The sleeve 8 of steel is provided, at its end facing the piston head 3, with an annular flange 11 which rests under initial stress on the piston skirt 4, after the fitting of the sleeve 8. The sleeve 8 engaEes with a threading 12 provided on its 4 11 - 3 exterior, here for example K148 x 1.5 lef-'t-l-hpnd thread, in the correspondingly formed threading provided on the central aperture 13 of the piston skirt 4. The dished sprinEs 7 of the spring pack 6 for the one part lie with their external 5 circumferences on the internal circumference of the sleeve 8 for guidance and fixing of their position andfor the other part they have a spacing from the shank of the screw 5 in order that the throughflowing cooling oil required for cooling may be drained into the crank-ease. This cooling oil is introduced through an in.jection nozzle (not shown) by way of a supply cond-ait 14, arrow 15, into an external annular cooling passage 16, whence it passes by way of apertures 17, arrow 18, in the piston skirt 4 to an inner cooling chamber 19, fron which, as indicated by the arrow 209 it flows throughbetween screw 5 and dished springs 7 by way of recesses 21 of a washer 22 into the cran k-case, or partially enters an opening of the connecting rod for lubrication.

In the fitting of the piston the sleeve 8, provided wit^ln left-hand thread 12, is screwed with initial stress into the piston skirt 4. Since the screw 5 has an opposite threading, slackening of the sleeve 8 is prevented in the production of the connection of piston head 3 and piston skirt 4 by the screw 5.

After the assembly of the piston 1 the piston head 3 lies for the one part with an external, annularly surrounding rib 23 and for the other part with an inner annular rib 24, surrounding separately therefrom, against correspondingly shaped counter-abutments of the piston skirt 4, the two ribs 235 24 being so formed, as regards dimensionsg.that in the tightening of the screw 5 firstly the outer rib 23 and then the inner rib 24 is applied to its counter-surface on the piston skirt 4.

With such a piston construction, with simple means a piston with very low overall height is realised in which, when the engine is operating, a uniform stress distribution is guaranteed without local stress peaks.

C 0 1

Claims

Claims

I.) Built-up liQuid-ccoled piston for internal combustion engines, consisting of a piston head accommodating the Diston rings and a piston skirt, which are connected with one another through an elastic central screw connection, characterised in that a sleeve (8) accommodating a spring pack (6) in its interior is centrally screwed with the piston skirt (4) and a screw (5), which rests axially on the spring pack (6) and engages through the sleeve (8), is made fast on the piston head (3).
2.) Built-up liquid-cooled piston according to Claim 1, characterised in that the spring pack (6) rests with its external circumference on the internal circumference of the sleeve (8), for the guidance of the individual dished springs (7).
3.) Built-up liquid-cooled piston according t.o Claim 1 or 2, charFcteri-sed in that for the draining of the cooling oil liauid out of the central cooling chamber (1q) the spring pack (6) surrounds the shank of the screw (5) with spacing and the annular washer (22) provided between screw head (10) and spring pack (6) is provided with radial recesses (21).
4.) Built-up liquid-cooled piston according to one of the preceding Claims, characterised in that the threading (12) of the sleeve (8) isuith opposite direction to that of the screw (5).
5.) Built-up liquid-cooled piston substantially as described with reference to t/he accompanying drawing.

published 1988 aT The Patent Office, 'tate House, 66'71 F4,6h Holb.,rj,. Lonj,)n WC1R 4TP. FU-ther copies may be obtained from The Patent Office, Sales Branch, St Mazy Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniquer ltd. St Mary Cray. Kent. Con. L'87.