GB2336194A

GB2336194A - Insulating device

Info

Publication number: GB2336194A
Application number: GB9907695A
Authority: GB
Inventors: Frank Buehner; Lutz Westenberger; Bruno Hezel; Markus Ulrich
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-04-06
Filing date: 1999-04-01
Publication date: 1999-10-13
Anticipated expiration: 2019-04-01
Also published as: DE19815284A1; GB2336194B; DE19815284C2; GB9907695D0

Abstract

An insulating device for shielding heat-sensitive plastic components of internal combustion engines from the effects of thermal radiation, comprises a foil 14 made of thermostable material such as a metalised plastic foil. An additional insulation element 18 may be provided. The reflector foil 14 may be coated with a self-adhesive layer.

Description

2336194 1 Insulating device The invention relates to an insulating device

having the features described in the preamble of clain 1.

Background art

It is known that internal combustion engffies are a source of considerable heat emission. Admittedly, in the case of liquid-cooled i.e. engines a considerable portion of the heat produced by the high combustion temperatures is dissipated via an air-swept heat exchanger into the ambient air, but particularly in the region of an exhaust section, e.g. in the vicinity of an exhaust manifold, much higher temperatures arise than 'm the remairmg installation compartment of the i.e. engine. Because of increasirig use of plastic parts as functional or ftm components, preferably for reasons of weight but also appearance, a problem which is becoming increasingly more manifest in known i.e. engines is effective thermal shielding of temperature-sensitive parts which are positioned close to heat hearths.

Thus, cylinder head covers, intake manifolds or exhaust gas recirculation valves, which are made of e.g. polyamide or polyphenylene sulfide, as a protection agamist damage as a result of excessive thermal stress are shielded by means of so-called heat shields acting as radiation reflectors.

As radiation reflectors, so-called thermal or shieldmig plates are known, which are fastened to the functional components made of plastic material, with minimal clearance relative to the latter, with the aid of clips or webs. They are preferably riveted to the plate components with the aid of spring clips for thermal isolation 2 and/or latched with the plastic components by means of spring clips. A low clearance of a few rru'llimetres relative to the plastic parts gives rise to an additional air cushion with the result that, because of the poor heat transfer properties of air, a more effective insulation arises than with contacting assembly. Furthermore, 'm said manner the risk of acoustically problematical sympathetic vibrations is minimized. Usually, such plates comprise at least three layers. Two outer plate layers are thermally aluminized for optimum radiation reflection, and an inner layer serves both as a heat insulator and to provide additional acoustic damping.

i 0 2 5 The drawbacks of the known insulating devices are 1.a. their relatively complex and hence expensive manufacture and assembly, because the three plate layers which are normally used have to be first individually punched and then brought into their final shape by means of a deformation step. In a further work step, one of the plate layers is provided with a circumferential flange. Rivet fastening of the bows and clips and hence a further assembly step is additionally required.

Advantages of the invention The insulating device according to the mivention has the advantage of beffig highly versatile while being at the same time extremely easy to assemble. Its use results m much lower costs, both in terms of labour and materials, compared to the known insulating devices. Furthermore, compared to conventional thermal plates. substantial savings in weight are possible.

Additional acoustic baffles may be integrated in a simple manner by means of a further insulating layer between plastic component and insulating device or insulating foil. By virtue of the extremely low spatial requirement of the 3 insulating device in the form of a reflector foil, it is possible to realize very low clearances between plastic flisictional components and heat-ernitting engine components such as, for example, exhaust manifolds. It is moreover possible in said manner to optimize an assembly clearance between the exhaust manifold and the cylinder head cover.

A greater design freedom as regards a configuration and grouping of components may also prove particularly advantageous. Thus, given use of the insulating device according to the invention it is possible, for example, significantly to reduce the clearances between exhaust manifold and heat-sensitive plastic components, particularly 'm the case of micIffied cylider head covers.

Further advantageous refinements of the invention are evident from the remaining features described in the sub-claims.

Drawings There now follows a detailed description of embodiments of the invention with reference to the accompanying drawings. The drawings show:

Figure 1 an insulating device for a cylinder head cover of an Le. engine; Figure 2 an insulating device having an additional acoustic baffle and 2 _S Figure 3) a conventional insulating device made of sheet steel.

Description of the embodiments

4 Figure 1 shows in a diagrammatic partial view a cutout of an 1.c. engine 2 with a laterally emanating exhaust section, represented by an exhaust manifold 4, and with a cylinder head 6 above the 1.c. engine 2. The cylinder head 6 has, as a covering, trim and/or acoustic baffle, a cylinder head cover 10. The latter may be made, for example, of a plastic material such as polyamide or polyphenylene sulfide which is not resistant to all of the high temperatures which may arise in the i.e. engine 2. Especially when positioned in the vicmity of the exhaust mahifold 4, such plastic components require additional thermal insulation and/or shielding in order, on the one hand, to prevent acute damage as a result of local overheating and, on the other hand, to reduce or prevent medium- and longer-term material changes such as, for example. embnttlement.

In order to protect the cylMider head cover 10 Mi the vicinity of the exhaust manifold 4 from the effects of heat, an insulating device in the form of a reflector foil 14 is applied onto the surface of the cylinder head cover 10. Said reflector foil may comprise, for example, a thin metal foil or a metallized plastic foil. A good join between reflector foil 14 and cylinder head cover 10 is advantageously produced by surface adhesion, e.g. by coating the reflector foil 14 with a selfadhesive layer.

The reflector foil 14 may easily be applied over a large area of such heat-sensifive plastic components as the cylinder head cover 10 and may, by virtue of a preferably flexible and/or expandable structure and a resultant adaptability, also be laid and/or positively applied onto curved and irregularly shaped surfaces.

Figure 2 shows a view of a part of the 1.c. engmie 2 corresponding to Figure 1. Unlike the thin reflector foil provided in Figwe 1, the reflector foil 14 according to Figure 2 is additionally provided with an insulation element 18, which may be used both for an improved heat-insulating effect and for an additional soundinsulating effect. The insulation element 18 may either be applied prior to application of the reflector foil 14 on the cylinder head cover 10 or alternatively as an intermediate layer between two thin foil layers - form pan of the reflector foil 14 itself Assembly is effected in said case also by adhesion, e.g. by means of a self-adhesive layer on the reflector foil 14.

To illustrate the particular advantages of the insulating device according to the invention, Figure 3 shows a further view of a part of the 1.c. engine 2 corresponding to Figures 1 and 2. Here, however, a conventional insulating device of the type which mi a known manner is widely used in 1.c. engines is shown. A thermal plate 20 may be seen, to which is fastened a spring clip 22 for latching connection of the thermal plate to the cylinder head cover 10 made of plastic material. The spring clip 22 may be attached e.g. by a nivetedjoint to the thermal plate 20.

On the cylinder head cover 10 a plurality of webs 24 may be seen, which advantageously are to be already provided Mi the casting mould m order to enable the thermal plate 20 to be capable of assembly - and, in particular, of disassembly in the event of repair - without screwed or riveted joints. Clearly visible are the necessary undercuts of the webs 24, which make manufacture of the cylinder head cover 10 more complex and hence more costly than is the case with the embodiments according to Figures 1 and 2.

6

Claims

Claims

1.

i 0 2.

J.

- W, -L 4.

L0 5.

6.

Insulating device for shielding heat-sensitive components of internal combustion engmies from the effects of thermal radiation, m particular an insulating layer for thermally shielding heat-sensitive components made of plastic material which are installed at points subject to extreme thermal stress, characterized in that the insulating layer comprises a foil made of thermostable material.

Insulating device according to claim 1, characterized in that the foil is a reflector foil (14) which reflects radiant heat.

Insulating device according to claim 2, characterized in that the reflector foil (14) is provided with a self-aMesive layer.

Insulating device according to one of claims 2 or 3), characterized in that the reflector foil (14) is flexible and longitudinally expandable.

Insulating device accordmig to one of the preceding claims, characterized in that the reflector foil (14) is a thermostable metal foil.

Insulating device according to one of claims 2 to 4, characterized in that the reflector foil (14) is made of thermostable plastic material.

7 7.

8.

1 11.

9.

10.

12.

1 J1).

Insulating device according to claim 6, characterized in that the reflector foil (14) is a metallized plastic foil.

Insulating device according to one of the preceding claims, characterized in that the reflector foil (14) comprises an additional insulation element (18).

Insulating device according to claim 8, characterized in that the insulation element (18) presents a high degree of acoustic damping.

Insulating device according to one of claims 8 or 9, characterized in that the insulation element (18) presents a high heat transfer resistance.

Insulating device according to one of claims 8 to 10, characterized in that the insulation element (18) is disposed between cylinder head cover (10) and reflector foil (14).

An insulating device substantially as hereffibefore descnibed with reference to Figure 1 of the accompanying drawings.

An insulating device substantially as heremibefore described with reference to Figure 2 of the accompanying drawings.