GB2339596A

GB2339596A - Mounting i.c. engine plug-top ignition coils

Info

Publication number: GB2339596A
Application number: GB9914967A
Authority: GB
Inventors: Karl-Heinz Nuebel; Reinhold Herrmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-07-14
Filing date: 1999-06-25
Publication date: 2000-02-02
Anticipated expiration: 2019-06-25
Also published as: FR2781255A3; JP3065710U; DE29812536U1; ITMI990415V0; IT246816Y1; GB9914967D0; ITMI990415U1; GB2339596B; FR2781255B3

Description

2339596 Ignition device for a multi-cylinder internal combustion engine

Prior art

The invention is based on an ignition device for a multi-cylinder internal combustion engine of the type according to clain 1. EP 0 512 357 A2 discloses an ignition device of this kind in which a plurality of individual ignition coils are individuaUy mounted in a support unit and project out of the latter with their highvoltage domes.

A support unit which is thus completed may then be placed as a one-piece mounting assembly on the cylinder head of an 'internal combustion engine and all the ignition coils at the same time connected to the associated spark plugs of the internal combustion engine.

However the ignition coils are rigidly fixed in the support unit in a disadvantageous manner such that after being connected to the spark plugs, which are mounted so as to be stationary and rigid, their position may be distorted due to temperature fluctuations or installation tolerances, and this may jeopardise the operational reliability of the ignition device.

Advantages of the invention In contrast the ignition device according to the invention with the characterising features of claim I has the advantage of avoiding the above-mentioned inadequacy to a satisfactory degree. Each ignition coil is thus held in the support unit via a bearing device which allows a relative movement between the ignition coil and the support unit to take place. This non-positive arrangement provides the necessary 2 flexibility in the connection between the ignition coils and the support unit, even when temperature fluctuations occur and installation conditions vary due t'O manufacturing tolerances, so that the operational reliability, of the ignition device is also guaranteed under these less favourable conditions of use.

Advantageous measures for implementing the invention are presented "in the subclau"ns.

Drawings An embodiment of the invention is represented in the drawings and explained in detail in the description. of the figures. Figure I shows the ignition device 'in separate construction units and Figure 2 a beaning device of an ignition coil "in a support unit, both as perspective views.

Description of the embodiment

An ignition device 11, represented 'in Figure 1, of a multi-cylinder internal combustion engine comprises a plurality of ignition coils 12 corresponding to the number of cylinders of the internal combustion engine. The ignition device I I is designed in a known manner, which is not shown in detail, for mounting on a cylinder head of the internal combustion engmie. So-called spark plug shafts with a round crosssectional area of passage are disposed 'in the cylinder head, each bemig associated with a cylinder and extending from an entrance opening. A spark plug 13 is placed "in a stationary position 'in each spark plug shaft, so as to produce a rigid, immobile spark plug arrangement resulting from these Mistallation. locations, which are 'in particular disposed 'in a row. Each of the spark plugs 13 comprises a high-voltage terminal, facmig the entrance opening, for making contact with an ignition coil 12.

The ignition coils 12 are preferably each formed as rod-type ignition coils with a housing 16 of a cylindrical basic shape. The diameter of the housing 16 is smaller than that of the spark plug shaft by an interstitial clearance, so that rather than being rigidly clamped in the spark plug shafts, the ignition coils 12 have a certain mobility within the interstitial clearance.

A first end portion 17 projects in axial alignment out of the end of the housing 16 of the ignition coils 12 so as to be disposed at the highvoltage terminal of the associated spark plug 13, while a second end portion 18 projects out of this housing in the opposite direction on the other side.

Axially directed contact elements 19 "in the form of flat-plug studs are located on the second end portion 18, these flat-plug studs being provided for making contact with mating contact elements, which are not shown, in a support unit 2 1, wherein the mating contact elements are bundled as a primary terminal in a connection plug 22 located on the end of the support unit 2 1.

Besides serving to contact the ignition coils 12 on the low-voltage side, the cuboidal support uruit 2 1, which consists of a basic body 23 and a cover 24, which can be pushed onto the body and locked thereon, serves as a support element for the coils. For this purpose a bearing device 26 is provided for each ignition coil 12.

The bearing device 26 according to Figure 2 comprises at the second end portion 18 of the ignition coil 12 a suspension element 27 in the form of a mushroomshaped locking hook of a plastics material. The bearing device 26 in the basic body 23 also comprises a locating element 28 'in the form of two catch rails 29 which are disposed parallel to one another and which each have sawtooth catch hooks 3 1 located "in rows.

4 Upon the ignition coil 12 being inserted axiallymi the basic body 23 of the support unit 2 1, the catch rails 29 are widened radially as the suspension element 27 enters the engagement region of the catch hooks 31 while the suspension element 27 slides along the pair of catch hooks, which are just then in engagement until this locks behind the locating element 28 and prevents the latter from movig 'in the opposite direction. This operation is repeated until the ignition coil 12 has been inserted to the full depth in the basic body 23.

By pushing the cover 24, which is shown at a distance 'in Figure 1, onto the basic body 23, strip-shaped limiting elements 32 of the cover 24 are brought up to the catch rails 29, so that these can no longer widen radially. The radial spring travel of the catch rails 29 is thus restricted to an extent such that the igru"fion coil 12 is on the one hand positively retamied in the support unit 21, yet on the other is disposed in the support unit 21 with play which gives it angular mobility of approximately +/- 5' "in the direction of the longitudial extent of the support unit 2 1.

This method of securing the ignition coils 12 to the support unit 21 on the one hand gives this assembly a rigidity which allows it to be mounted on or dismounted from the cylinder head of the internal combustion engine in a single mounting step each time.

On the other hand, because of the angular mobility, the individual ignition coils 12 have a degree of freedom and the possibility of adapting their position in optimum fashion to the support unit 21 when thermal expansions occur during operation of the internal combustion engine or installation conditions vary due to manufacturing tolerances.

This prevents distortion of the ignition coils 12, which are mounted in a single C assembly, at the cylinder head of the "internal combustion engie and guarantees I operational reliability of the ignition device I I even under less favourable conditions of use.

6

Claims

1. Ignition device for a mulfi-cylm"der internal combustion engine, with a plurality of igruition coils (12), preferably of the same type, which are held 'in a support unit (2 1) for simultaneously mounting at 'installation locations, which are in particular disposed in a row, of the 'internal combustion engine, characterised in that each of the ignition coils (12) is held 'in the support unit (2 1) via a bearing device (26) which allows a relative movement between the igruition coil (12) and the support unit (2 1) to take place.

2. Ignition device according to claim 1, characterised in that the bearing device (26) comprises at least one suspension element (27) at the ignition coil (12) and a locating element (28), corresponding to the suspension element, at the support unit (2 1), and the suspension element (27) is coupled to the locating element (28) when the ignition coil (12) is inserted in the support unit (2 1).

3. Igruition device according to claim 2, characterised in that the relative movement between the igruition coil (12) and the support unit (2 1) is restricted by a limiting element (32).

4. Ignition device according to any one of the preceding claims, charactenised in that the ignition coils (12) are formed as rod-type coils.

5. Ignition device substantially as hereinbefore described with reference to the accompanying drawings.