WO2020164689A1

WO2020164689A1 - Method for monitoring uneven wear of a transmission chain

Info

Publication number: WO2020164689A1
Application number: PCT/EP2019/053417
Authority: WO
Inventors: Bertrand AUGE; Luc VERCAUTEREN
Original assignee: Toyota Motor Europe
Priority date: 2019-02-12
Filing date: 2019-02-12
Publication date: 2020-08-20

Abstract

The present invention concerns a method for monitoring uneven wear of a transmission chain (31) which operatively connects a first and a second sprocket (32,33) for transmitting rotation between them. The method comprises the steps of obtaining successive measurements of a phase shift between the first and second sprocket (32,33) and determining whether a difference between a maximum measurement and a minimum measurement, among the successive measurements, exceeds a predetermined threshold.

Description

METHOD FOR MONITORING UNEVEN WEAR OF A TRANSMISSION CHAIN

TECHNICAL FIELD

The disclosure relates to the field of transmission chains, and more specifically to a method for monitoring uneven wear thereof.

BACKGROUND

Transmission chains are used in a wide range of applications to transmit rotation between two or more sprockets. In particular, they may be used in applications wherein it is required to maintain an accurate synchronization between the two or more sprockets. Ensuring accurate synchronization can be particularly important for the timing of camshafts driving the gas exchange of internal combustion engines. An accurate synchronization of the one or more camshafts driving inlet and/or outlet valves of an internal combustion engine with a driving shaft, such as the crankshaft of the internal combustion engine, may contribute to optimum combustion conditions and, in so-called interference engines, prevent collision of the inlet and/or outlet valves with a piston.

In these and other applications, transmission chains are subject to wear. In particular, tension and bending strains may lead to plastic deformation of each link, and in particular to plastic elongation. Such elongation presents multiple drawbacks. At worst, it may lead to such slackening of the transmission chain that it disengages the sprockets, but even a more limited elongation may increase a phase shift between the sprockets beyond acceptable tolerances.

In order to monitor such wear of a transmission chain operatively connecting a first and a second sprocket for transmitting rotation therebetween, monitoring methods are known for determining a global elongation of the chain.

However, the transmission chain may not wear evenly over its whole length. In particular peak loads and/or a relative weakness of individual chain links may lead to an uneven wear, wherein at least one of the chain links elongates more than the rest. Even if the global elongation of the chain remains below a given tolerance, an excessive local elongation may also affect the accurate synchronization between sprockets, and even lead to the transmission chain disengaging the sprockets. SUMMARY

A first object of the disclosure is that of providing a method for monitoring uneven wear of a transmission chain operatively connecting a first and a second sprocket for transmitting rotation between the first and second sprockets.

According to a first aspect of the disclosure, the method comprises the steps of obtaining successive measurements of a phase shift between the first and second sprocket, and determining whether a difference between a maximum measurement and a minimum measurement, among the successive measurements, exceeds a predetermined threshold.

Because the phase shift fluctuates depending on the elongation of just the traction side of the transmission chain, an excessive local elongation of the transmission chain may be determined, even when the global elongation of the whole transmission chain remains moderate ,by determining whether a difference between a maximum measurement and a minimum measurement, among the successive measurements, exceeds the predetermined threshold. Each successive measurement of the phase shift between the first and second sprocket may be obtained by measuring a time lag between a first sprocket angular position signal and a second sprocket angular position signal. The first sprocket angular position signal may be a pulse signal generated by a passage, in a vicinity of a first sprocket angular position sensor, of one or more beacons rotating with the first sprocket. Analogously, the second sprocket angular position signal may be a pulse signal generated by the passage, in a vicinity of a second sprocket angular position sensor, of one or more beacons rotating with the second sprocket. According to a second aspect, the method may further comprise the steps of averaging the successive measurements of the phase shift, to obtain an average phase shift and determining whether the average phase shift exceeds another predetermined threshold. Accordingly, the method may contribute to determining not only whether there is an excessive local elongation of the transmission chain due to uneven wear, but also whether the global elongation is excessive due to more even wear.

According to a third aspect, the first sprocket may be a driving sprocket and the second sprocket a driven sprocket. In particular, the second, driven sprocket may be operatively connected to a camshaft, which may for instance drive drives inlet and/or outlet valves of an internal combustion engine. Monitoring the uneven wear of the transmission chain may thus contribute to ensuring accurate timing of the inlet and/or outlet valves, and thus an efficient gas exchange of the internal combustion engine. The first sprocket may further be operatively connected to a crankshaft of the internal combustion engine, so that the camshaft is driven by the crankshaft over the transmission chain and sprockets.

A fourth aspect of the present disclosure relates to an electronic monitoring device configured to carry out the abovementioned method, a fifth aspect relates to an internal combustion engine comprising one or more inlet and/or outlet valves, a camshaft with one or more cams for driving the one or more inlet and/or outlet valves, a first sprocket that is a driving sprocket, a second sprocket that is a driven sprocket and is operatively connected to the camshaft, a chain for transmitting rotation from the first sprocket to the second sprocket, and an electronic monitoring device configured to carry out the abovementioned method, and a sixth aspect relates to a motor vehicle comprising the abovementioned internal combustion engine.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the invention. In particular, selected features of any illustrative embodiment within this specification may be incorporated into an additional embodiment unless clearly stated to the contrary.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of the following detailed description of an embodiment in connection with the accompanying drawings, in which :

- FIG. 1 is a schematic drawing of a motor vehicle ;

- FIG. 2 is a schematic drawing of a reciprocating internal combustion engine for driving the motor vehicle of FIG. 1;

- FIG. 3 illustrates pulsed driving shaft and camshaft angular position signals from the reciprocating internal combustion engine of FIG. 2;

- FIG. 4 is a flowchart illustrating a method of monitoring uneven wear of a transmission mechanism for driving the camshaft of the reciprocating internal combustion engine of FIG. 2 based on the pulsed signals of FIG. 3; and

- FIG. 5 is another flowchart illustrating in detail a subroutine within the method of FIG. 4.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be preceded by the term "about", whether or not explicitly indicated. The term "about" generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e. having the same function or result). In many instances, the term "about" may be indicative as including numbers that are rounded to the nearest significant figure. Any recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes a.o. 1, 4/3, 1.5, 2, e, 2.75, 3, n, 3.80, 4, and 5).

Although some suitable dimension ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed. As used in this specification and the appended claims, the singular forms”a", "an", and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary. Fig. 1 illustrates schematically a vehicle 10 equipped with an internal combustion engine 20 for its propulsion. Although in the illustrated example the vehicle 10 is a wheeled road vehicle, it could also be an offroad vehicle, a tracked vehicle or even a boat or an aircraft. Similarly, although in the illustrated example the internal combustion engine 20 is a single-cylinder reciprocating internal combustion engine, it could be a multi-cylinder engine or even a single- or multi-rotor rotary engine. As seen in Fig. 2, the internal combustion engine 20 may comprise inlet and/or outlet valves 21,22 for driving its gas exchange. The internal combustion engine 2 may further comprise respective cams 23, 24 for driving the valves 21, 22 open, either directly or over respective valve rockers and/or pushrods, as well as respective return springs 25,26 for driving the valves 21, 22 closed against the cams 23, 24.

As also seen in Fig. 2, the internal combustion engine 20 may further comprise a camshaft 27 operatively connected to the cams 23, 24 for driving their rotation. In particular, the cams 23,24 may be integrally formed with the camshaft 27. Although in the illustrated example the internal combustion engine 2 comprises a single camshaft 27 for both the inlet and outlet cams 23, 24, such an internal combustion engine may instead comprise multiple camshafts, for instance separate camshafts for the inlet and outlet valves and/or for different cylinders or banks of cylinders.

As in Fig. 2, the internal combustion engine 2 may further comprise a transmission mechanism 30 for driving the camshaft 27. More specifically, this transmission mechanism 30 may be configured to transmit rotation from a driving shaft to the camshaft 27. Typically, when the internal combustion engine 20 is a reciprocating internal combustion engine as in the illustrated example, this driving shaft may be the crankshaft 28, so that the movement of the valves 21, 22 is synchronized with that of the corresponding piston 29. However, according to circumstances, a different driving shaft, such as for instance the output shaft of an electric motor synchronized with the crankshaft, may be chosen as the source of the rotation transmitted to the camshaft 27.

As in the illustrated example, the transmission mechanism 30 may be a timing chain mechanism comprising a timing chain 31, a driving sprocket 32, one or more driven sprockets 33, and a chain tensioner 34. Driving sprocket 32 may be operatively connected to the driving shaft (crankshaft 28 in the illustrated example) and each driven sprocket 33 to a respective camshaft 27. Timing chain 31 may engage both the driving sprocket 32 and each driven sprocket 33, operatively connecting them to transmit the rotation of the driving sprocket 32 to each driven sprocket 33. In a four- stroke internal combustion engine 20, each driven sprocket 33 may have twice the number of teeth of the driving sprocket 32, so as to rotate at half the angular speed, and the chain tensioner 34 may press laterally against the timing chain 31 to maintain chain tension and thus chain length C on the traction side 31a of the timing chain 31 from the driving sprocket 32 to each driven sprocket 33 and thus ensure synchronization between the driving shaft and the camshaft 27. Accurate synchronization is important not only to ensure combustion efficiency within the internal combustion engine 20, but also, in so-called interference engines, to prevent collision of one or more of valves 21, 22 against the corresponding piston. However, wear in transmission mechanism 30 may affect the synchronization between the driving shaft and the one or more camshafts 27. In particular, in the illustrated example, the elongation of one or more of the links of timing chain 31 due to wear may shift the angular position of the one or more camshafts 27 with respect to the driving shaft. Although in the illustrated example the transmission mechanism is a timing chain mechanism, it may alternatively be a timing belt mechanism or a timing gear mechanism. In either case, accurate synchronization may also be affected by wear. To address this, the internal combustion engine 20 may further comprise angular position sensors 35, 36 for detecting the angular position of, respectively, the driving shaft and the one or more camshafts 27, and an electronic monitoring device 40. The angular position sensors 35, 36 may be configured to generate pulse signals in response to the nearby passage of one or more beacons rotating with, respectively, the driving shaft and the one or more camshafts 27. For example, as shown in Fig. 2, different-sized ferromagnetic blocks 38 fixed to the camshaft 27 may form the beacons for camshaft angular position sensor 36, which may be an inductive sensor. The driving shaft angular position sensor 36 may also be an inductive sensor, and the corresponding beacons may be formed by ferromagnetic teeth 39 fixed to the driving shaft, around its axis of rotation, wherein one of the teeth 39 may differ from the rest so as to index each full rotation of the driving shaft. In response to the rotation of camshaft 27, angular position sensors 35, 36 may thus respectively generate camshaft angular position signal V₂ and driving shaft angular position signal Vi, for instance as pulses in a voltage V over time t, as illustrated in Fig. 3. The electronic monitoring device 40 may be connected to the angular position sensors 35, 36 to monitor the wear of the transmission mechanism based on the camshaft angular position signal V₂ and driving shaft angular position signal Vi, according to a method such as illustrated by the flowchart of Fig. 4.

In the illustrated method, a counter n may be first set to zero in a step SI 10. Subsequently, in step S120, the electronic monitoring device 40 may receive the camshaft angular position signal V₂ and driving shaft angular position signal Vi. In a third step S130, a measurement of a phase shift between the driven sprocket 33 and the driving sprocket 32 may be obtained, for example as a time lag Dt_n between the camshaft angular position signal V₂ and driving shaft angular position signal Vi. If the camshaft angular position signal V₂ and driving shaft angular position signal Vi are pulsed signals, this time lag Dt_n may be measured between corresponding pulses, as shown in Fig. 3, and stored in a memory of electronic monitoring device 40. In subsequent step S140, it may be determined whether the value of counter n is equal or higher than a predetermined minimum integer value N that is higher than zero. If the value of counter n has not yet reached this threshold N, the value of counter n may be increased by one in step S150, and the process cycled back to step S120. On the other hand, if the determination in step S140 is positive, the process may continue on to step S160, wherein the electronic monitoring device 40 may determine the highest and lowest measurements D_max , Dt_min out of the last N stored measurements {Dt_n- N -Dt_n} of the phase shift. These determinations of step S160 may be carried out using a subroutine as illustrated in the flowchart of Fig. 5, wherein a counter m may be set, in step S210, to the difference n-N between the counter n and predetermined minimum integer value N. The value of both the highest and lowest measurements Dt_max, Dt_min may be then provisionally set to that of stored measurement Dtn-N in subsequent step S220. In the next step S230, the value of counter m may be increased by one, and then, in step S240, it may be determined whether the value of the next stored measurement Dt_m is greater than the value provisionally set as highest measurement Dt_max. If the determination in step S240 is positive, the subroutine may proceed to step S250, wherein the value of the highest measurement Dt_max may be updated to be that of stored measurement Dt_m. On the other hand, if the determination in step S240 is negative, the subroutine may proceed to step S260, wherein it may be determined whether the value of stored measurement Dt_m is smaller than the value provisionally set as lowest measurement Dt_min. If the determination in step S260 is positive, the subroutine may proceed to step S270, wherein the value of the lowest measurement Dt_min may be updated to be that of stored measurement Dt_m. In any case, after any of steps S250, S270 or a negative determination in step S260, the subroutine may proceed to step S280, wherein it may be determined whether the value of counter m is still smaller than n. If this determination is positive, the subroutine may cycle back to step S230, whereas if it is negative, the subroutine may be ended.

Going back to the main routine illustrated in Fig. 4, after the subroutine of step S160, the electronic monitoring device 40 may then proceed to calculate, in step S165, the difference Dt_max,min between the the highest and lowest measurements Dt_max, Dt_min out of the last N stored measurements {Dt_n-N...Dt_n> of the phase shift. In the following step S170, the electronic monitoring device 40 may proceed to determine whether this difference Dt_max,min exceeds a predetermined threshold T. If the determination in step S170 is positive, the process may progress to step S175, wherein the electronic monitoring unit 40 may generate a warning of excess uneven wear of the transmission chain before ending the process. On the other hand, if the determination in step S170 is negative, the process may progress to step S180, wherein the electronic monitoring unit 40 may calculate an average value Dt_n,_ave of the last N stored measurements { Dt_n-N··· Dt_n} of the phase shift, and on to step S190, wherein the electronic monitoring unit 40 may determine whether the average value D t_n,ave of the last N stored measurements {Dt_n-N·.· Dt_n} of the phase shift exceeds another predetermined threshold Dt_ave,max, which is a threshold for even chain elongation and may be lower than the predetermined threshold Dt_max for uneven transmission chain elongation. If the determination in step S190 is positive, the process may progress to step S200, wherein the electronic monitoring unit 40 may generate a warning of excess uneven wear of the transmission chain before ending the process. On the other hand, if the determination in step S190 is negative, the value of counter n may be increased by one in step S150, and the process cycled back to step S120. Consequently, the illustrated method may ensure monitoring of both even and uneven wear of the transmission chain.

Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiment described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope of the present invention as described in the appended claims.

Claims

1. Method for monitoring uneven wear of a transmission chain (31) operatively connecting a first and a second sprocket (32,33) for transmitting rotation between the first and second sprocket (32,33), the method comprising the steps of:

obtaining successive measurements of a phase shift between the first and second sprocket (32,33);

determining whether a difference between a maximum measurement and a minimum measurement, among the successive measurements, exceeds a predetermined threshold.

2. Method according to claim 1, wherein each successive measurement of the phase shift between the first and second sprocket (32,33) is obtained by measuring a time lag between a first sprocket angular position signal (Vi) and a second sprocket angular position signal (V₂).

3. Method according to claim 2, wherein the first sprocket angular position signal (Vi) is a pulse signal generated by a passage, in a vicinity of a first sprocket angular position sensor (35), of one or more beacons rotating with the first sprocket (32).

4. Method according to any one of claims 2 or 3, wherein the second sprocket angular position signal (V₂) is a pulse signal generated by the passage, in a vicinity of a second sprocket angular position sensor (36), of one or more beacons (38) rotating with the second sprocket (33).

5. Method according to any one of the previous claims, further comprising the steps of:

averaging the successive measurements of the phase shift, to obtain an average phase shift; and

determining whether the average phase shift exceeds another predetermined threshold.

6. Method according to any one of the previous claims, wherein the first sprocket (32) is a driving sprocket and the second sprocket (33) is a driven sprocket. 7. Method according to claim 6, wherein the second sprocket (33) is operatively connected to a camshaft (27).

8. Method according to claim 7, wherein the camshaft (27) drives inlet and/or outlet valves (21,22) of an internal combustion engine (20).

9. Method according to claim 8, wherein the first sprocket (32) is operatively connected to a crankshaft (28) of the internal combustion engine (20). 10. Electronic monitoring device (40) configured to carry out the method according to any one of the previous claims.

11. Internal combustion engine (20) comprising:

one or more inlet and/or outlet valves (21, 22);

a camshaft (27) with one or more cams (23,24) for driving the one or more inlet and/or outlet valves (21,22);

a first sprocket that is a driving sprocket;

a second sprocket that is a driven sprocket and is operatively connected to the camshaft (27);

a chain for transmitting rotation from the first sprocket to the second sprocket; and

an electronic monitoring device (40) configured to carry out the method according to any one of claims 8 or 9. 12. Motor vehicle (10) comprising the internal combustion engine

(20) according to claim 11.