GB2539970A

GB2539970A - Chain guide assembly f 5 or an internal combustion engine

Info

Publication number: GB2539970A
Application number: GB1511783.1A
Authority: GB
Inventors: Pagliaro Pierluigi; Zallio Iacopo
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2015-07-03
Filing date: 2015-07-03
Publication date: 2017-01-04
Also published as: GB201511783D0

Abstract

A chain guide assembly (540a fig. 3) for an internal combustion engine (110 fig. 1) comprising a guide member 545b configured to guide a chain (530) along its path between a first rotatable shaft (135) and a second rotatable shaft (145) of the Internal combustion engine. The guide member is provided with at least one guide bore 550 for fastening the guide member to a fixing portion (120, 130) of the engine by at least one fastener 560 passing through the bore, wherein the assembly comprises at least one dampening bushing 670 arranged in the guide bore. The dampening bushing may comprise of one or two flanges 570a, 570b giving the bushing an I-shape. The dampening bushing may also comprise an anti-wear bushing 580 that is co-moulded or bonded to the dampening bushing. The dampening bushing may be made from a material having a smaller elastic modulus than that of the chain guide member, such that the guide member may be made a metallic or plastic material and the dampening bushing may be made from an elastomeric material.

Description

CHAIN GUIDE ASSEMBLY FOR AN INTERNAL COMBUSTION ENGINE TECHNICAL FIELD

The present invention relates to a chain guide and more specifically to a chain guide assembly comprising a guide member used for guiding a chain, e.g. a timing chain, of an internal combustion engine.

BACKGROUND

It is known that internal combustion engines are provided with a chain connecting a first rotatable shaft to a second rotatable shaft of the engine.

For example, internal combustion engines are provided with a timing chain that synchronizes the rotation of the crankshaft and the camshaft(s) so that the engine's valves open and close at the proper times during each cylinder's intake and exhaust strokes.

The timing chain is typically a roller, bushing or inverted tooth (IT) chain connecting a crankshaft sprocket (i.e. a drive wheel) and a camshaft sprocket (i.e. a driven wheel). The timing chain is guided by means of chain guides having a guide member arranged in contact with the tight side of the timing chain. Chain guides are coupled to the engine by fasteners, such as bolts or screws, in order to guide the timing chain along its path between the crankshaft and the camshaft.

In particular, the chain guide can be coupled to the internal combustion engine in a fixed or in a movable manner. In other words, fixed chain guides are rigidly fixed to the engine with the aim of guiding the timing chain in a path imposed by the guide, while mobile chain guides are hinged to the engine with the aim of guiding the timing chain and adjusting the timing chain tensioning during the crankshaft rotation. The timing chain tensioning is adjusted by means of a tensioner which acts as a piston, using a spring and/or hydraulic pressure. The tensioner pushes the mobile chain guide that, rotating around a hinge, abuts against the timing chain to obtain a proper timing chain tensioning.

Both the fixed and the mobile chain guides are induced to vibrate when the timing chain is driven by the rotation of the crankshaft sprocket and specially on Diesel engines wherein the timing chain used has a high chain pitch. In particular, a periodic transversal movement of the timing chain relative to the sprockets revolution can produce vibrations transferred through the timing chain to the chain guides. The chain guides, being fastened to the engine structure (e.g. to the cylinder head and/or cylinder block), transmit said vibrations in turn to the engine structure with frequencies which can match one of the many natural frequencies of the system, thus driving it into resonance.

Vibrations are radiated by the engine surface producing the undesired so called "structure-borne” noise. Said noise is transmitted via a variety of paths, and then radiated acoustically into the vehicle as a sort of whine, which is undesirable for the occupants of the vehicle.

In view of the above, an object of an embodiment of the present invention is to provide a chain guide assembly that allows to reduce the structure-born noise radiated by the internal combustion engine.

Another object of an embodiment of the present invention is to provide an internal combustion engine with an overaii engine sound power ievei reduced.

Another object is that of accomplishing the above-mentioned goals with a simple, rational and rather inexpensive solution.

SUMMARY

These and other objects are achieved by a chain guide assembly according to an embodiment of the invention as defined in the independent claim. The dependent claims include preferred and/or advantageous aspects of said embodiments.

An embodiment of the invention provides for a chain guide assembly for an internal combustion engine comprising a guide member configured to guide a chain along its path between a first rotatable shaft (e.g. a camshaft or a balance shaft, or in general a driven shaft) and a second rotatable shaft (e.g. a crankshaft, or in general a drive shaft) of the internal combustion engine. The guide member is provided with at least one guide bore (for example a through hole) for fastening the guide member to a fixing portion of the internal combustion engine by at least one fastener passing through said at least one guide bore. The chain guide assembly comprises at least one dampening bushing arranged in said at least one guide bore of the guide member.

Advantageously, the dampening bushing allows to absorb vibrations of the chain guide assembly so that the chain guide assembly, and in particular of the guide member, is decoupled from the fastener and then from the engine structure.

It has to be noted that the term "bushing" is used herein to indicate a generic tubular element with a substantially hollow cylindrical shape (tubular shape), such as a sleeve or a grommet. According to an aspect of the invention, the dampening bushing comprises at least one flange extending outside said guide bore. According to still another aspect of the invention, the dampening bushing comprises two flanges, extending outside said guide bore, thus providing a substantially l-shape section.

The at least one flange, preferably the two flanges extending outside two opposite ends of the guide bore, allows to decouple the chain guide assembly, and in particular the guide member, from the fastener’s head and/or from the fixing portion of the internal combustion engine. The flange extending outside the guide bore reduces, in the selected frequency range, the energy directly transferred from the guide member to the engine and/or through the fastener.

In fact, a fastener is usually a screw provided with an elongated, and typically threaded, body protruding from a head. The elongated body is typically inserted within the guide bore, while the head remains outside the guide bore. A dampening bushing comprising at least one flange extending outside said guide bore can thus prevent contact between the head of the fastener and the guide member.

According to another aspect of the invention, the chain guide assembly comprises an anti-wear bushing, made of an anti-wear material, that is arranged at least partially on the internal surface of the dampening bushing.

Thanks to this aspect, the guide member, and in particular the dampening bushing arranged in the guide bore, can be protected, thus reducing frictions especiaiiy in the case of a mobile chain guide assembiy, wherein the guide member is movabie. In fact, the anti-wear bushing substantiaiiy acts as bearing eiement for the mobiie guide member of the chain guide assembly, that is rotatable at the fastener inserted in the guide bore.

According to an aspect of the invention, the anti-wear bushing comprises at ieast one flange extending outside said guide bore. According to still another aspect of the invention, the anti-wear bushing comprises two flanges, extending outside said guide bore, thus providing a substantially l-shape section.

The at least one flange, preferably the two flanges extending outside two opposite ends of the guide bore, allows to increase the anti-wear protection.

According to a particular aspect of the invention, the dampening bushing and the anti-wear bushing are co-molded or bonded.

This aspect of the invention allows to realize the dampening bushing and the antiwear bushing in a simple manner.

According to another aspect of the invention, the anti-wear bushing is made of an anti-wear materiai seiected from a plastic material (e.g. PTFE, also known as Teflon), ceramic materiai, metallic material.

Thanks to this, it is possible to avoid friction between the internal surface of the dampening and the fastener and/or the fixing portion of the internal combustion engine (in particular with the head of the fastener, to avoid loosening of the clamp provided by the fastener itselO-

According to another aspect of the invention, the dampening bushing is made of a material having an elastic modulus value minor than the elastic modulus value of the material of which is made the guide member. This aspect of the invention allows to realize the dampening bushing able to absorb vibrations of a chain guide assembly.

According to an aspect of the invention, the dampening bushing is made of a material having an elastic modulus value minor than one or more orders of magnitude of the elastic modulus value of the material of which is made the guide member.

According to another aspect of the invention, the guide member is made of plastic material. As an example polyamide materials such as PA66, PA66+GF (i.e. glass fiber reinforced), PA46, PA46+GF, or aluminum, steel or cast iron.

Thanks to this aspect, the vibrations induced by the timing chain are at least partially absorbed by the guide member.

According to another aspect of the invention, the dampening bushing is made of an elastomeric material, e.g. material comprising a natural and/or synthetic rubber.

Acxjording to a possible embodiment, the dampening bushing is made of TPO, HNBR, ACM, AEM or EPDM rubber.

Thanks to this, it is possible to absorb vibrations of a chain guide assembly, and in particular of its guide member, that in general made of a material having an elastic modulus value higher than that of the dampening bushing.

According to another aspect of the invention, the fasteners comprise at least one screw passing through said dampening bushing and fastened to said fixing portion of the internal combustion engine.

Thanks to this, it is possible to mount in a simple manner a chain guide assembly to a fixing portion of the internal combustion engine. In particular it is possibie to decouple the chain guide assembly, and in particular the guide member, from the internal combustion engine by means of the dampening bushing arranged in the guide bore of the guide member.

According to a particular aspect of the invention, the dampening bushing is dimensioned to obtain a chain guide assembly decoupling frequency higher than the engine firing order maximum frequency.

Thanks to this, it is possible to improve the durability of the chain guide assembly.

According to another aspect of the invention, the dampening bushing is dimensioned to, or in any case configured to, obtain a chain guide assembly decoupling frequency lower than the chain meshing minimum frequency.

With the term “chain guide assembly decoupling frequency” it is meant the vibration frequency characterizing the first eigenmode of the chain guide assembly, i.e. the first normal mode of the chain guide assembly.

The chain meshing minimum frequency can be defined by the following formula:

wherein erpnimm is the minimum engine rpm and N is the number of teeth of the shaft sprocket on which the chain is mounted. Thanks to this, it is possibie to improve the sound quaiity of the engine.

Another embodiment of the invention provides for an intemai combustion engine comprising a first rotatabie shaft, a second rotatable shaft, and a chain connecting said first rotatabie shaft with said second rotatabie shaft, wherein at least one chain guide assembiy according to an embodiment of the present invention is fastened to a fixing portion (e.g. the engine block and/or the cylinder head) of the intemai combustion engine by at least one fastener.

Thanks to this, it is possibie to provide an intemai combustion engine with an overail engine sound power level reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, with reference to the accompanying drawings, in which: • Figure 1 schematically shows an automotive system belonging to a motor vehicle; • Figure 2 is the section A-A of an internal combustion engine belonging to the automotive system of figure 1; • Figure 3 shows a chain guide assembly according to an embodiment of the present invention in an internal combustion engine belonging to the automotive system of figure 1; • Figure 4 is the section B-B of a chain guide assembly according an embodiment of the present invention; • Figure 5 is the section C-C of a chain guide assembly according an embodiment of the present invention.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that inciudes an internai combustion engine (ICE) 110 having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140.

The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam Phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifoid 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel Injectors 160, the throttle body 330, the EGR valve 320, the VGT actuator 290, and cam Phaser 155. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for ciarity.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The memory system 460 may include various storage types including optical storage, magnetic storage, soiid state storage, and other non-volatile memory. The Interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices.

The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

The program stored in the memory system 460 is transmitted from outside via a cable or in a wireless fashion. Outside the automotive system 100 it is normally visible as a computer program product, which is also called computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or non-transitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a WiFi connection to a laptop.

In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

With reference to figures 3 - 5, a possible embodiment of a chain guide assembly 540a, 540b for an internal combustion engine 110 will be now discussed.

Figure 3 shows a portion of an internal combustion engine wherein a timing chain 530 connects the camshaft 135 and the crankshaft 145 shown in figure 2.

An alternative embodiment (not shown) can provide that a chain connects a balance shaft (not shown) with the crankshaft 145.

In general, the chain connects a first rotatable shaft (e.g. a camshaft 135 or a balance shaft) with a second rotatable shaft (e.g. a crankshaft 145). A camshaft sprocket 510 is attached to one end of the camshaft 135, and a crankshaft sprocket 520 is attached to one end of the crankshaft 145,

The chain 530 (e.g. a timing chain 530) connects the crankshaft sprocket 520 and the camshaft sprocket 510 so that the timing chain may transmit power from rotating crankshaft 145 to camshaft 135. In this particular embodiment, the timing chain 530 is guided by two chain guide assemblies 540a, 540b according an embodiment of the present invention.

In particular, chain guide assembly 540a is a fixed chain guide assembly, while chain guide assembly 540b is a mobile chain guide assembly. Both chain guide assemblies 540a, 540b comprise a guide member 545a, 545b, preferably made of plastic, arranged in contact with the timing chain 530. More in particular, the guide member 545a, 545b has a slide surface bounded by shoulders so that the guide member has a U-shaped contour forming a rail for the timing chain.

The guide member 545a, 545b is provided with at least one guide bore 550, e.g. a through hole connecting two opposite surface of the guide member, for fastening the guide member 545a, 545b to a fixing portion 120, 130 of the internal combustion engine 110 by at least one fastener 560 passing through the guide bore 550. The fixing portion 120, 130 comprises e.g. the engine block 120 and/or the cylinder head 130 of the internal combustion engine 110, depending on possible layouts of the internal combustion engine.

In the case of a fixed chain guide assembly 540a, the guide member 545a can be provided with one or more guide bore 550, e.g. with two guide bores 550, preferably arranged in two opposite end portions of the guide member 545a, as shown in figure 3, for fastening the guide member 545a to the fixing portion 120, 130 of the engine 110. In this case, the guide member 545a is fixed to the fixing portion 120,130 of the engine 110 by two fasteners 560 such as screw and/or bolts, so that the guide member 545a is constrained rigidly to the fixing portion. As already mentioned above, the fastener usually comprises an elongated, and typically threaded, body protruding from a head. The elongated body is inserted within the guide bore 550, while the head 560a remains outside the guide bore 550.

In the case of a mobile chain guide assembly 540b, the guide member 545b has only one guide bore 550. In particular, the guide member 545b is hinged to the fixing portion 120 or 130 of the engine 110 at the guide bore 550 by a fastener 560 such as a screw or a bolt acting as a pivot in order to provide a rotation point. By means of a tensioner 600, the mobile chain guide assembly 540b, and in particular the guide member 545b, can be rotated in order to adjust the tensioning of the timing chain 530. The tensioner 600 can be e.g. a hydraulic operated piston for applying a force at an end of the guide member 545b so that the chain guide assembly 540b pivots about the rotation point provided on the guide bore 550. Thus a lateral force is applied to the timing chain 530 so as to reduce the slack therein.

The chain guide assembly 540a, 540b according to an embodiment of the present invention comprises at least one dampening bushing 570 arranged in the guide bore 550. The dampening bushing 570 has a substantially cylindrical shape. Preferably, the dampening bushing 570 has an external diameter substantially equal to, or slightly bigger than the diameter of the guide bore 550 in which it is arranged, so that the dampening bushing can be press-fitted in it.

Figure 4 shows the section B-B of the chain guide assembly 540a according an embodiment of the present invention. In this embodiment, the fastener 560 is in contact with the internal surface of the dampening bushing 570. In this way the dampening bushing 570 decouples the chain guide assembly 540a, and in particular of the guide member 545a, from the fastener 560 and consequently from the fixing portion 120, 130 of the internal combustion engine 110. Thus, the vibrations of the chain guide assembly 540a can be absorbed by the dampening bushing 570 and not transferred to the fastener 560, reducing the structure-borne noise radiated by the engine 110.

In one embodiment, the dampening bushing 570 extends outside the guide bore.

Preferably, the dampening bushing 570 comprises at least one flange 570a, 570b extending outside the guide bore 550. In an embodiment, a flange 570a can be provided on the side of the chain guide assembly 540a, and in particular of the guide member 545a, facing the fixing portion 120, 130 of the internal combustion engine 110 in order to decouple the fixing portion 120, 130 from the chain guide assembly 540a. In a further embodiment, a flange 570b can be provided on the other side, i.e. the side of the chain guide assembly 540a in contact with the fastener’s head 560a in order to decouple it from the chain guide assembly 540a.

More preferably, an embodiment provides that the dampening bushing 570 comprises two flanges 570a, 570b extending outside the guide bore 550 in both the chain guide assembly’s sides, thus providing an l-shape section, as shown in figure 4.

In this latest case the dampening bushing 570 can be realized e.g. in two or more pieces, wherein each piece can be inserted in the guide bore from both side of the guide member 545a of the chain guide assembly 540a.

An alternative embodiment provides that dampening bushing 570 is realized in a single piece and it can be press-fitted or bounded to the guide bore 550.

The dampening bushing 570 is made of a material having an elastic modulus value minor than the elastic modulus value of the material of which the guide member 545a is made. Preferably, evaluating the elastic modulus in GPa, the dampening bushing 570 is made of a material having an elastic modulus value minor than one or more orders of magnitude of the elastic modulus value of the material of which the guide member 545a is made. In the case in which the guide member 545a is made of plastic, the dampening bushing 570 can be made e.g. of elastomeric material, such as a HNBR rubber.

Figure 5 shows the section C-C of the chain guide assembly 540b according an embodiment of the present invention. In particular, the chain guide assembly 540b comprises an anti-wear bushing 580 arranged on the internal surface of the dampening bushing 570.

The anti-wear bushing 580 has a substantialiy cylindricai shape encirciing the internal surface of the dampening bushing 570. Preferably, the dampening bushing 570 is co-moided or bonded to the anthwear bushing 580. An alternative embodiment provides that the anthwear bushing 580 is realized in two or more pieces, wherein each piece can be inserted from both side of the dampening bushing 570 and preferably bonded to it.

An alternative embodiment provides that the anti-wear bushing 580 is realized in a single piece and it can be press-fitted or bounded to the dampening bushing 570.Thanks to the anti-wear bushing 580, the dampening bushing 570 of the chain guide assembly 540b according to the invention is protected from the fastener 560, avoiding the friction between the fastener 560 and the dampening bushing 570, so that the lifespan of the dampening bushing 570, and consequently of the chain guide assembly 540b, is increased.

The anti-wear bushing 580 can be provided with both a fixed chain guide assembly 540a and a chain guide assembly 540b. It has to be noted that, this embodiment is particularly advantageous in the case of mobile chain guide assembly 540b as shown In figure 5. In fact, in this latest case, the friction between the dampening bushing 570 and the fastener 560 is greater than that in the fixed chain guide assembly 540a, due to the rotation of the chain guide assembly 540b around the fastener 560 (e.g. a pivot screw or bolt).

The anti-wear bushing 580 is preferably made of an anti-wear material, selected from a plastic material (e.g. PTFE, also known as Teflon), ceramic material, metallic material. The fastener 560 is normally made of steel or in general metallic material, thus the anti-wear bushing 580 is preferably made of a metallic material. Alternative embodiments can provide that the guide member is made of the same material of the anti-wear bushing. In other word the anti-wear material can be selected from a plastic material, aluminum, steel or cast iron.

The anti-wear bushing 580 is preferably shaped in order to cover at least partially one or both flanges 570a, 570b of the dampening bushing 570, by at least one corresponding flange 580a, 580b extending outside said guide bore 550.

In this way, at least one flange 570a, 570b of the dampening bushing 570 can be protected from the friction with the fastener’s head 560a and/or with the fixing portion 120,130 of the internal combustion engine 110.

The embodiment shown in figure 5 comprises a dampening bushing 570, provided with two flanges 570a, 570b extending outside the guide bore 550, and an anti-wear bushing 580 provided with an l-shaped section so that the internal surface of the dampening bushing 570 is protected from the friction with the fastener 560 as well as with the fastener’s head 560a and with the fixing portion 120, 130 of the engine 110 and/or other parts of the engine (not shown in figure).The anti-wear bushing 580 is interfaced between the dampening bushing 570 and the fastener 560 so that, no contact is provided between the anti-wear bushing 580 and the guide member 545b in order to avoid the transmission of vibration from the chain guide assembly 540b to the fastener 560 and/or to the fixing portion 120, 130 of the engine 110 that are in contact with the anti-wear bushing 580.

The dampening bushing 570 is designed in order to obtain a chain guide assembly 540a, 540b with a determined decoupling frequency fo. In particular, the chain guide assembly decoupling frequency fo, is the vibration frequency characterizing the first eigenmode of the chain guide assembly, i.e. the first normal mode of the chain guide assembly, and can be determined by simulations. More particularly, the dampening bushing dimensions are determined from simulations in order to obtain a chain guide assembly with a chain guide assembly decoupling frequency fo greater than the engine firing order maximum frequency and/or lower than the chain meshing minimum frequency.

The engine firing order maximum frequency can be defined by the following formula:

wherein erprnmax is the maximum engine rpm and Fo is the firing order.

The chain meshing minimum frequency can be defined by the following formula:

wherein erprnmm is the minimum engine rpm and N is the number of teeth of the crankshaft sprocket 520.

More preferably, the dampening bushing 570 is dimensioned to obtain a chain guide assembly decoupling frequency fo comprised into the interval defined by the following formula:

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCES

Fo firing order ermprnin minimum engine rpm erpmtnax maximum engine rpm N number of teeth of the crankshaft sprocket fo chain guide assembly decoupling frequency 100 automotive system 110 internal combustion engine 120 engine block 125 cylinder 130 cylinder head 135 camshaft 140 piston 145 crankshaft 150 combustion chamber 155 cam phaser 160 fuel injector 170 fuel rail 180 fuel pump 190 fuel source 200 intake manifold 205 air intake pipe 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 exhaust aftertreatment device 290 VGT actuator 300 EGR system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor

450 electronic control unit ECU 460 memory system 510 camshaft sprocket 520 crankshaft sprocket 530 timing chain 540a fixed chain guide assembly 540b mobile chain guide assembly 545a guide member of the fixed chain guide assembly 545b guide member of the mobile chain guide assembly 550 guide bore 560 fastener 560a fastener’s head 570 dampening bushing 570a flange of the dampening bushing 570b flange of the dampening bushing 580 anti-wear bushing 580a flange of the anti-wear bushing 580b flange of the anti-wear bushing 600 tensioner

Claims

1. A chain guide assembly (540a, 540b) for an internal combustion engine (110) comprising a guide member (545a, 545b) configured to guide a chain (530) along its path between a first rotatable shaft (135) and a second rotatable shaft (145) of the internal combustion engine (110), said guide member (545a, 545b) being provided with at least one guide bore (550) for fastening said guide member (545a, 545b) to a fixing portion (120, 130) of the internal combustion engine (110) by at least one fastener (560) passing through said at least one guide bore (550), wherein said chain guide assembly (540a, 540b) comprises at least one dampening bushing (570) arranged in said at least one guide bore (550) of the guide member.

2. The chain guide assembly (540a, 540b) according to claim 1, wherein said dampening bushing (570) comprises at least one flange (570a, 570b) extending outside said guide bore (550).

3. The chain guide assembly (540a, 540b) according to claim 1 or 2, wherein said dampening bushing (570) comprises two flanges (570a, 570b) providing a substantially l-shape section.

4. The chain guide assembly (540a, 540b) according to any preceding claims, comprising an anti-wear bushing (580) arranged at least partially on the internal surface of the dampening bushing (570).

5. The chain guide assembly (540a, 540b) according to claim 4, wherein said anti-wear bushing (580) comprises at least one flange (580a, 580b) extending outside said guide bore (550).

6. The chain guide assembly (540a, 54Gb) according to claim 4 or 5, wherein the dampening bushing (570) and the anti-wear bushing (580) are co-molded or bonded.

7. The chain guide assembly (540a, 540b) according to any claim 4 to 6, wherein the anti-wear bushing (580) is made of an anti-wear material.

8. The chain guide assembly (540a, 540b) according to any of the preceding claims, wherein said dampening bushing (570) is made of a material having an elastic modulus value minor than the elastic modulus value of the material of which the guide member (545a, 545b) is made.

9. The chain guide assembly (540a, 540b) according to any of the preceding claims, wherein said guide member (545a, 545b) Is made of a material selected from aluminum, steel, cast iron, or plastic material.

10. The chain guide assembly (540a, 540b) according to any of the preceding claims, wherein said dampening bushing (570) is made of an elastomeric material.

11. The chain guide assembly (540a, 540b) according to any of the preceding claims, wherein said at least one fastener (560) comprises a screw passing through said dampening bushing (570) and fastened to said fixing portion (120, 130) of the internal combustion engine (110).

12. The chain guide assembly (540a, 540b) according to any preceding claims, wherein the dampening bushing (570) is dimensioned to provide a chain guide assembly decoupling frequency (fo) higher than the engine firing order maximum frequency.

13. The chain guide assembly (540a, 540b) according to any preceding claims, wherein the dampening bushing (570) is dimensioned to provide a chain guide assembly decoupling frequency (fo) lower than the chain meshing minimum frequency.

14. An internal combustion engine (110) comprising a first rotatable shaft (135), a second rotatable shaft (145) and a chain (530) connecting said first rotatable shaft (135) with said second rotatable shaft (145), and at least one chain guide assembly (540a, 540b) comprising a guide member (545a, 545b) according to any of the preceding claims is fastened to a fixing portion (120, 130) of the internal combustion engine (110) by at least one fastener (560).

15. The internal combustion engine (110) according to claim 14, wherein said fixing portion (120, 130) comprises the engine block (120) and/or the cylinder head (130) of the internal combustion engine (110).