LU85979A1 - SENSOR FOR DETECTING THE PASSAGE OF A PISTON OR PISTON GROUP OF AN INTERNAL COMBUSTION ENGINE BY THE POSITION OF THE HIGH DEATH POINT - Google Patents

Description

i! 'ι

The present invention relates to a sensor making it possible to detect the displacement of a piston or group of pistons of an internal combustion engine up to the position of top dead center.

5 In particular / the invention relates to a sensor of the type comprising a rotary element which can rotate in synchronism with the drive shaft and having several detectable references each associated with a respective piston or group of pistons 10 and. a fixed terminal instrument associated with a rotary element and serving to detect the passage of each of the references and to produce a corresponding predetermined electrical signal.

A conventional sensor of this type, used in connection with a four-stroke four-cylinder internal combustion engine, is shown diagrammatically in FIG. 1. In this drawing, the rotary element is designated by 10 and the instrument terminal is designated by 11. The detectable references consist of teeth 12, 13 diametrically opposite. In the embodiment 20 represented in FIG. 1, the tooth 12 is associated with the pistons 1 and 4, while the tooth 13 is associated with the pistons 2 and 3. The rotary element 10 is mounted so that the tooth 12 passes in front of the terminal instrument 11 when the pistons 1 and 4 are at top dead center (or at a predetermined advance or delay angle 25 relative to the movement to top dead center).

FIG. 2 shows / as a function of time £, the typical trend of the signal which can be obtained at the output of the terminal instrument 11: this signal S comprises a succession of pulses, which are each associated with the passage of a tooth 12 30 or 13 in front of the terminal instrument 11. In this signal, it is impossible to distinguish the pulses associated with the displacement of the pistons 1, 4 to the top dead center with respect to the pulses t associated with the displacement of the pistons 2 , 3 to top dead center.

In other words, the conventional sensor shown in Figure 1 35 does not make it possible to make a difference in the "row" of cylinders in which the pistons move to top dead center.

2

This is a problem for I electronic ignition systems with static distribution.

The object of the invention is to produce a sensor of the type indicated above, which is designed so as to make it possible to obtain additional information very simply and very easily about the "row" in which the pistons $ e move to the top dead center at a certain moment.

The object according to the invention is ctbti-erct by means of a sensor which is distinguished in that the rotary element has an additional detectable reference which is placed in the vicinity of the reference associated with a predetermined piston or group of pistons.

The following description, intended to illustrate the invention, aims to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: FIGS. 1 and 2, already described, illustrate a sensor according to the prior art and the electrical signal which can be obtained using this sensor, and FIGS. 3 and 4 , which will be described below, respectively represent an embodiment of the sensor according to the invention and the trend of the electrical signal which can be obtained using this sensor as a function of time.

FIG. 3 shows a sensor according to the invention associated, for example, with the shaft of a four-stroke four-cylinder engine. According to the invention, the rotary element 10 has an additional reference, which is for example an additional tooth 14, adjacent to the tooth 12. Preferably, the additional tooth 14 is placed so as to be angularly offset behind the 30 reference tooth 12, in operation.

FIG. 4 illustrates the signal SS which can be obtained using the terminal instrument 11 of FIG. 3: this signal has respective cycles of pulses A, C and B produced by the passage of the teeth 12, 14 and 13 opposite the terminal instrument 11, in the direction of rotation of the arrow F in FIG. 3.

3

The duration separating a pulse A from the next pulse C and the duration Tg separating a pulse C from the next pulse B must always be different. Consequently, it is possible to distinguish pulse A (relating to 5 the pair of cylinders 1 and 4) from pulse 6 (relating to U pair of cylinders 2 and 3) by simple comparison of the durations and T2.

As stated above / these durations should generally be different from each other. Their ratio is constant when the motor drive shaft rotates at a constant angular speed. The ratio of these times can vary when the drive shaft (and consequently the rotary element 10) is subjected to an angular acceleration or deceleration "The position of the tooth 14 must therefore be such that, for acceleration 15 maximum expected angular / The duration is in any case different from the T2 duration (it is / in this example / less than this duration).

While reference has been made to a four-cylinder four-stroke engine in the embodiments explained above / those skilled in the art will immediately understand that the application of the sensor according to the invention is not not limited to such an engine, but allows, in general, to distinguish the piston or group of pistons of an engine moving to top dead center.

In addition, the detectable references can be of a very different nature from the teeth represented by means of a nonlimiting example. Thus, they could for example be constituted by notches, inserts made of a material having magnetic characteristics different from the material 30 constituting the rotary element 10, etc.

* In addition, each piston or group of pistons can have several angularly equidistant references associated with it.

Of course, a person skilled in the art will be able to imagine, from sensors whose description has just been given by way of illustration and in no way limitative, various other variants and modifications which do not depart from the scope of the invention.

Claims (2)

4 * E V * N 6 I CATIONS 1. Sensor intended to detect the displacement of a piston or group of pistons ¢ 1/4; 2, 3) of an internal combustion engine up to the position of top dead center / comprising t 5 a rotary element ¢ 10) which can rotate in syn chronism with the drive shaft and having several detectable references ¢ 12 / 13) each associated with a respective piston or group of pistons (1/4; 2, 3) / and a fixed terminal instrument ¢ 11) associated with the rotating element ¢ 10) and used to detect the passage of each references ¢ 12/13) and to produce a corresponding predetermined signal / characterized in that the rotary element ¢ 10) has an additional detectable reference (14) placed on the track of a reference 15 ¢ 12) associated with a piston or predetermined group of pistons (1, 4). 2, sensor according to claim 1, characterized in that the additional detectable reference (14) is placed so as to be angularly offset with respect to said reference (12) associated with the predetermined piston or group of pistons (1/4). finished / in use.