AU605942B2

AU605942B2 - Apparatus for detecting the position of a piston ring in an internal combustion engine

Info

Publication number: AU605942B2
Application number: AU26570/88A
Authority: AU
Inventors: George G. Lassanske
Original assignee: Outboard Marine Corp
Current assignee: Outboard Marine Corp
Priority date: 1988-01-19
Filing date: 1988-12-06
Publication date: 1991-01-24
Anticipated expiration: 2008-12-06
Also published as: AU2657088A; GB2214642A; IT8848674A0; FR2626042A1; GB8828316D0; IT1224826B; JPH01240773A

Description

t o" 59,4

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: a1l l *1 0 Priority: 4 d Related Art: "a 4 TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: OUTBOARD MARINE CORPORATION 100 SEA-HORSE DRIVE

WAUKEGAN

ILLINOIS 6008';

USA

Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: APPARATUS FOR DETECTING THE POSITION OF A PISTON RING IN AN INTERNAL COMBUSTION ENGINE The following statement is a full description of this invention including the best method of performing it known to me:-

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-la- APPARATUS FOR DETECTING THE POSITION OF A PISTON RING IN AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION The invention relates to timing systems for internal combustion engines and more particularly to apparatus for monitoring the position of a piston in a two-stroke engine by detecting the presence of a piston ring.

The desirability of timing events coo, °f during engine operation with respect to piston 00 :44 position is known. Application of highly accurate 0 4measuring systems which correlate an engine's spark o c ignition or fuel injection with the piston position .oo aid in the development of engines with greater fuel efficiency and performance.

4 I t 4 A known method of monitoring piston position entails mounting a magnetic core on the 44 4 4 1flywheel of the engine at a position which correlates to a reference position of the piston Pat il 4,471,652). By monitoring the position of the magnet as it rotates during engine operation, the relative piston position can be calculated. Commonly, the reference position of the piston selected is the top dead center position. Alternatively, the reference position may be the bottom dead center position.

L i I O4444 4444 4* 4 4I 44 4 S'4 -2- While at the outset this method affords accurate measurement, engine wear results in decreased accuracy.

Another technique of detecting a piston's position requires the insertion of a probe into a combustion cylinder through a spark plug or glow plug hole in the cylinder head. Several different types of probes have been particularized, including mechanical proximity probes Pat.

4,296,629). Also known are probes which radiate microwaves and calculate the piston's position by the reflected microwave patterns which resonate at known cylinder volumes equally spaced to either side of top dead center Pat. 4,528,845). While these methods do not suffer inaccuracies due to engine wear, they are not particularly well suited for monitoring of ordinary engine operation as they require the displacement of a spark plug, or an additional hole in the cylinder head.

According to another technique, a piston's position is detected by magnetic sensing means. In one known arrangement, a magnetic "fin" is attached to the piston Pat. 4,407,155). As the piston approaches the bottom dead center position, the fin passes between a pair of electromagnetic coils which protrude into the combustion cylinder.

Inherent deficiencies of this technique include the necessary modification of the piston, and a r- -r **,cfS it i '-1 ':i

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cr ~p~ 15 20 -3restriction of the selected reference position of the sensing means to near or at bottom dead center.

According to another technique, a piston's position is determined by detecting the passage of a piston ring as it passes by a sensor at a known position Pat. 4,444,049). One such method known in the art requires a source and receiver of ultrasonic waves placed in the engine block. The sensor detects ultrasonic waves reflected by the cylinder and detects the passage of the piston ring by sensing the damping effect that the passing piston ring has on the reflected ultrasonic waves.

Attention is also directed to the following U.S. Patents: April 28, 1981 May 24, 1983 February 28, 1984 September 18, 1984 April 3, 1979 October 27, 1981 October 4, 1983 April 24, 1984 September 18, 1984 January 8, 1985 January 15, 1985 July 16, 1985 October 8, 1985 May 20, 1986 4,263,868 4,384,480 4,433,572 4,471,653 4,147,054 4,296,629 4,407,155 4,444,049 4,471,652 4,492,114 4,493,208 4,528,845 4,545,238 4,589,278 Fukui Kraoe Sundeen Kawamura Hohenberg Vuyovich Sundeen Hitchcock Yasuhara Yamanaka Grover Esaki Kinoshita Ginns L -4- SUMMARY OF THE INVENTION The invention provides an internal combustion engine comprising an engine block including a generally cylindrical inner wall defining a combustion cylinder, a piston which is located within the combustion cylinder and which reciprocally slides in said combustion cylinder between a top dead center position and bottom dead center position, a piston ring attached to the piston and having an outer circumference in sliding contact with the inner wall, the piston ring U being fabricated of magnetic material, and magnetic sensing means located at said inner wall for detecting the position of the piston ring.

In one embodiment, the magnetic sensing means is recessed relative to the inner wall such that no mechanical interference results from the passage of the piston ring as the piston reciprocally slides between the top dead center position and the bottom dead center position.

The invention also provides an internal combustion engine comprising an engine block including a generally cylindrical inner wall, the inner wall K defining a combustion cylinder and having therein a recess, a piston which is located within the combustion cylinder and which reciprocally slides in the combustion cylinder between a top dead center position and a bottom dead center position during engine operation, a piston ring attached to the piston and having an outer circumference in sliding contact with the inner wall, the piston ring being fabricated of a magnetic material and being located such that the piston ring passes the recess as the piston reciprocally slides between the top dead center position and the bottom dead center 7 position, and magnetic sensing means located in the recess for detecting the position of the piston ring.

In one embodiment, the sensing means is recessed relative to the inner wall such that no mechanical interference results from the passage of the piston ring as the piston reciprocally slides between top dead center and bottom dead center.

A principal feature of the invention is the provision of sensing means which is located in a recess in the combustion cylinder and which detects the passage of a magnetic piston ring.

Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.

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i r. Y F-il. ii-1.I- DESCRIPTION OF THE DRAWINGS Fig. 1 is an elevational view, partially in section, of an internal combustion engine embodying the invention.

Fig. 2 is an enlarged cross-sectional view taken generally along line 2-2 in Fig. 1 and showing the piston below the top dead center position.

Fig. 3 is a view similar to Fig. 2 and showing the piston in the top dead center position.

10 Before one embodiment of the invention is explained in detail, it is to be understood that o o the invention is not limited in its application to o the details of construction and the arrangements of o0 0 components set forth in the following description or illustrated in the drawings. The invention is .o capable of other embodiments and of being practiced ^or being carried out in various ways. Also, it is to o"°o S be understood that the phraseology and terminology H used herein is for the purpose of description and o 20 should not be regarded as limiting.

GENERAL DESCRIPTION Shown in Figure 1 is a two-stroke internal combustion engine 10. While the illustrated embodiment of the invention is a two-stroke engine, the invention is equally advantageous in its application to four-stroke engines.

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'1 -7- The engine 10 comprises an engine block 12 which includes a main portion 14 and a cylinder head portion 16. The main portion 14 includes a t generally cylindrical inner wall 18 which defines a combustion cylinder 20. In the preferred embodiment, the inner wall 18 is formed by a cylinder liner 24 Swhich is considered part of the engine block 12 and which is mounted in the main portion 14 of the engine i block 12, as is known in the art. In alternative 1 0 embodiments, the inner wall 18 need not be formed by i!l r °a separate cylinder liner 24. The main portion 14 Shas therein a threaded bore 46, and the cylinder liner 24 has therein a bore 48 that is aligned with Sthe bore 46. The bores 46 and 48 define a recess 22 I 15 in the inner wall 18. The reasons for the recess 22 is explained hereinafter. The main portion 14 also I includes an exhaust outlet 26 communicating with the cylinder 20. The cylinder head portion 16 supports a spark plug 27.

The engine 10 also comprises a crankcase 28 which, in the preferred embodiment, is, in part, an integral part of the main portion 14 of the engine block 12. The crankcase 28 includes an inlet 30 and communicates with th cylinder 20 via an inlet or transfer passage 32. This construction is known in the art. Suitable means, such as a carburetor (not shown), can be used for controlling the flow of air, oil and fuel into the inlet i -i ii 1 -8- The engine 10 also comprises a piston 34 which is located within the cylinder 20 and which reciprocally slides in the clinder 20 between a top dead center position (shown in Fig. 3) and a bottom dead center position (not shown) during engine operation. The engine 10 also comprises at least one piston ring 36. Preferably, a pair of piston rings 36 are carried by the piston 34, and each has an outer circumference which is in sliding contact with the inner wall 18. The piston rings 36 are o preferably fabricated of magnetic material, are ferromagnetic, and are located such that the piston rings 36 pass the recess 22 as the piston 34 moves °4 between the top dead center position and the bottom dead center position.

The engine 10 also comprises a crankshaft 38 rotatably supported within the crankcase 28, and a connecting rod 40 connected between the piston 34 and the crankshaft 38 for causing rotation of the crankshaft 38 in response to reciprocation of the piston 34.

The engine 10 also comprises sensing means for detecting the position of the piston rings 36. While various suitable sensing means can be employed, in the illustrated construction, such sensing means is located in the recess 22 and is recessed relative to the inner wall 18 such that no mechanical interference results as the piston rings 36 pass the recess 22. Furthermore, in the preferred embodiment, the sensing means includes magnetic sensing means 42 which includes an electromagnet 44 operable to indicate an interruption of the flux field created by the electromagnet when a piston ring 36 passes the electromagnet 44. Such electromagnetic sensing means are well-known in the art and generate an electrical signal which is usable by known control means. In the preferred embodiment, the electromagnet 44 is screwed into the threaded bore 46 in the engine block 12. In the illustrated construction, the magnet 44 extends partially into the bore 48 in the cylinder liner 24 but is recessed o from the wall 18, as described above.

04 The signal generated by the oa S 15 electromagnet 44 when it is passed by the piston rings 36 can be used, for example, to control fuel injection into the cylinder 20. Suitable control systems that can utilize the signal generated by the electromagnet 44 are known in the art.

S 20 Various features of the invention are set forth in the following claims.

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Claims

1. An internal combustion engine comprising an engine block including a generally cylindrical inner wall defining a combustion cylinder, a piston which is located within said combustion cylinder and which reciprocally slides in said combustion cylinder between a top dead center position and a bottom dead center position, a piston ring attached to said piston and having an outer circumference in sliding contact with said inner wall, said piston ring being fabricated of magnetic material, and magnetic sensing means located at said inner wall for detecting the position of said piston ring.

2. An internal combustion engine in accordance with Claim 1 wherein said magnetic sensing means is recessed relative to said inner wall.

3. An internal combustion engine comprising an engine block including a generally cylindrical inner wall, said inner wall defining a combustion cylinder and having therein a recess, a piston which is located within said combustion cylinder and which reciprocally slides in said combustion cylinder between a top dead center position and a bottom dead center position during engine operation, a piston ring attached to said piston and having an outer circumference in sliding contact with said inner wall, said piston ring being fabricated of a magnetic material and being located such that said J *nt 000 0 0 00 0 4o 00 0 000 0 O 00 II 0 11 piston ring passes said recess as said piston moves between said top dead center position and said bottom dead center position, and magnetic sensing means located in said recess for detecting the position of said piston ring.

4. An internal combustion engine in accordance with claim 3 wherein said sensing means is recessed relative to said inner wall.

An internal combustion engine in accordance with claim 3 wherein said sensing means is recessed relative to said inner wall.

6. An internal combustion engine comprising an engine block including a generally cylindrical inner wall, said inner wall defining a combustion cylinder and having therein a recess, a piston which is located within said combustion cylinder and which reciprocally slides in said combustion cylinder between a top dead center position and a bottom dead center position during engine operation, a piston ring attached to said piston and having an outer circumference in sliding contact with said inner wall, said piston ring being fabricated of magnetic material and being located such that said piston ring passes said recess as said piston reciprocally slides between said top dead center position and said bottom dead center position, and magnetic sensing means for detecting the position of said piston ring, said sensing means being located in said recess and recessed relative to said inner wall. 0 00 0~ 0 L L 12

7. An internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS 15th DAY OF October 1990 OUTBOARD MARINE CORPORATION By Its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 0 ,4 o 0 0 o o 0 0 0 oo 0000f 4' (I J: /cl? i