GB2498591A

GB2498591A - Internal Combustion Engine with a Variable Compression Ratio

Info

Publication number: GB2498591A
Application number: GB201201204A
Authority: GB
Inventors: Fiorello Losano; Domenico Palmisani
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-01-23
Filing date: 2012-01-23
Publication date: 2013-07-24
Also published as: GB201201204D0

Abstract

The invention provides an internal combustion engine 110 comprisÂing a cylinder block 120 defining at least a cylinder 125, and a reciprocating piston 140 accommodated inside the cylinder 125, wherein the piston 140 is made from a material having a thermal expansion coefficient lower than a thermal expansion coeffiÂcient of a material which the cylinder block 120 is made from. The piston 140 material may be steel and the cylinder block 120 material may be aluminium. As the engine warms up and the cylinder increases in length more than the piston does, thus providing a bigger gap above the piston, and the compression ratio of the cylinder will be lowered. Independent cooling systems for the piston and the cylinder block are also disclosed.

Description

INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The present invention relates to an internal combustion engine, especially an internal combustion engine for a motor vehicle.

BACKGROUND

It is known that an internal combustion engine for a motor vehicle generally comprises an engine block which defines at least one cylinder accommodating a reciprocating piston coupled to rotate a crankshaft. The cylinder is closed by a cylinder head that cooperates with the reciprocating piston to define a combustion chamber. A fuel and air mixture is cyclically disposed in the combustion chamber and ignited, thereby generating hot ex-panding exhaust gasses that cause the reciprocating movements of the piston.

Due to the reciprocating movements of the piston, the volume of the combustion cham-ber cyclically varies between a minimum value, reached when the piston is at the top of its stroke, and a maximum value, reached when the piston is at the bottom of its stroke.

The ratio between the maximum value and the minimum value of the combustion cham-ber volume is conventionally referred as the compression ratio of the internal combustion engine.

Generally a high value of the compression ratio has the advantage of facilitating the cranking of the internal combustion engine when it is cold, whereas a low value of the compression ratio has the advantage of reducing the polluting emissions (principally NON) and the noises generated by the intemal combustion engine when it is already warmed-up.

For this reason, many internal combustion engines have been proposed which allows a variation of the compression ratio on the basis of the operating conditions. However, most of the proposed solutions have the drawback of involving a very complex mechani-cal design of the internal combustion engine, which also implies a sensible increase of the production costs.

An object of an embodiment of the present invention is to solve this drawback by provid-ing an internal combustion engine having an adjustable compression ratio, as well as a simple and cost saving mechanical design.

SUMMARY

This and other objects are attained with the by the characteristics of the embodiments of the invention as reported in the independent claims. The dependent claims recite pre-ferred and/or especially advantageous features of the embodiments of the invention.

In particular, an embodiment of the invention provides an internal combustion engine comprising a cylinder block defining at least a cylinder, and a reciprocating piston ac-commodated inside the cylinder, wherein the piston is made from a material having a thermal expansion coefficient lower than a thermal expansion coefficient of a material which the cylinder block is made from.

Thanks to this solution, as long as the internal combustion engine is cold, the lengths of the cylinder and of the piston therein define a certain compression ratio, which can have a value quite high (e.g. of about 16.0 for a Diesel engine) to advantageously facilitate the cranking of the internal combustion engine. As the temperature of the internal conibus- tion engine increases, the length of the cylinder increases more than the length of the re- ciprocating piston, so that the compression ratio of the internal combustion engine pro-gressively decreases. In this way, when the internal combustion engine is completely warmed-up, the compression ratio may assume a value quite low (e.g. of about 15.0 for a Diesel engine) to advantageously reduce the polluting emissions and the noises gen-erated by the internal combustion engine.

To enhance this effect, an aspect of the invention provides that the thermal expansion coefficient of the piston material may be lower than 60% of the thermal expansion coeffi-cient of the cylinder block material.

By way of example, the piston material may be steel and the cylinder block material may be aluminum.

These materials have the advantages of being quite cheap and easily available, and of guaranteeing the realization of cylinder block and piston having good quality.

According to another aspect of the invention, the piston may be coupled to rotate a crankshaft by means of a connecting rod made from a material having a thermal expan- sion coefficient lower than the thermal expansion coefficient of the cylinder block materi-al. In this way, as the temperature of the internal combustion engine increases, the length of the cylinder increases more than the length of the connecting rod and consequently more than the stroke of the reciprocating piston, thereby further reducing the compression ratio of the internal combustion engine.

To enhance this effect, an aspect of the invention provides that the thermal expansion coefficient of the connecting rod material is lower than 60% of the thermal expansion coefficient of the cylinder block material.

By way of example, the connecting and the piston rod may be made from the same ma-terial.

This solution has the advantage of simplifying the production and the coupling of these parts.

According to another aspect of the invention, the internal combustion engine further comprises a piston cooling circuit, which includes an oil pump arranged to draw oil from an oil sump and to deliver it to at least a nozzle provided for jetting the oil inside the cy-linder onto the piston.

Thanks to this solution, during the operation of the internal combustion engine, the piston may be advantageously cooled down so as to reduce the piston elongation and then the compression ratio of the internal combustion engine.

To improve the cooling of the piston, the above named piston cooling circuit may com-prise an oil cooler located between the oil sump and the nozzle.

The oil pump of the piston cooling circuit may be coupled and driven by an electric motor, which advantageously allow to regulate the oil flow supplied to the piston.

According to an aspect of this solution, the internal combustion engine may comprise a sensor for measuring a parameter indicative of an engine temperature, such as for ex- ample an engine metal temperature, an engine coolant temperature or an engine lubri-cant temperature, and an electronic control unit connected with the sensor and with the oil pump of the piston cooling circuit, which is configured to: -monitor a value of the engine temperature parameter through the sensor, and -activate the oil pump of the piston cooling circuit if the monitored value of the engine temperature parameter exceeds a predetermined threshold value thereof.

This aspect of the invention has the advantage of providing an effective thermal man- agement of the piston, which allows to control the compression ratio of the internal com-bustion engine.

According to still another aspect of the invention, the internal combustion engine com-prises also an engine cooling circuit, which includes a coolant pump arranged to draw a coolant from a coolant tank and to deliver it into at least a first coolant jacket defined by the cylinder block in heat exchange relation with the cylinder.

Thanks to this solution, during the operation of the internal combustion engine, the en-gine black may be advantageously cooled so as to avoid thermo-structural problem.

The coolant pump of the engine cooling circuit may be coupled and driven by an electric motor, which advantageously allow to regulate the coolant flow supplied to the coolant jacket.

According to an aspect of this solution, the internal combustion engine may comprise a sensor for measuring a parameter indicative of an engine temperature, such as for ex- ample an engine metal temperature, an engine coolant temperature or an engine lubri-cant temperature, and an electronic control unit connected with the sensor and with the coolant pump of the engine cooling circuit, which is configured to: -monitor a value of the engine temperature parameter through the sensor, and -activate the coolant pump of the engine cooling circuit if the monitored value of the en-gine temperature parameter exceeds a predetermined threshold value thereof.

This aspect of the invention has the advantage of providing an effective thermal man-agement of the cylinder block.

According to still another aspect of the invention, the cylinder of the internal combustion engine has an upper part which is closed by a cylinder head cooperating with the piston to define a combustion chamber, and the cylinder block defines at least a second coolant jacket, which is in heat exchange relation with the upper part of the cylinder and which is connected with the coolant pump through a second pipe separated by a first pipe con-necting the coolant pump to the first coolant jacket, a valve being located in the first pipe for selectively prevent the coolant to flow from the coolant pump to the first coolant jack-et.

Thanks to this solution, it is advantageously possible to differentiate the cooling of the upper part of cylinder from the remaining part thereof.

According to an aspect of this solution, the internal combustion engine may comprise a sensor for measuring a parameter indicative of an engine temperature, such as for ex- ample an engine metal temperature, an engine coolant temperature or an engine lubri-cant temperature, and an electronic control unit connected with the sensor and with the valve of the engine cooling circuit, which is configured to: -monitor a value of the engine temperature parameter through the sensor, and -keep the valve of the engine cooling circuit closed if the monitored value of the engine temperature parameter is below a predetermined threshold value thereof.

This aspect of the invention has the advantage of providing a more effective thermal management of the engine block, which allows to keep the temperature of the cylinder block at higher values than usual and then to reduce the compression ratio of the internal combustion engine, while continuing to effectively cool down the upper part of the cylind- er, which is more exposed to the heat generated by the fuel combustion in the combus-tion chamber, in order to prevent thermal-structural problem.

Another embodiments of the invention eventually provide an automotive system and a motor vehicle comprising the internal combustion engine described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 is a schematic view of an internal combustion engine system according to an embodiment of the invention.

Figure 2 is a schematic view of the section A-A of the internal combustion engine shown in figure 1.

Figure 3 is a schematic view of the section B-B of figure 2.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100, as shown in Figures 1, that includes an internal combustion engine (ICE) 110, in this example a Diesel engine. The internal combustion engine 110 comprises a cylinder block 120 defining at least one cy-linder 125, in this example four cylinders 125 disposed in line. Each of the cylinders 125 accommodates a reciprocating piston 140, which is coupled to rotate a crankshaft 145 by means of a respective connecting rod 141. A cylinder head 130 is fixed on top of the cy-linder block 120 and cooperates with each of the pistons 140 to define a combustion chamber 150.

The pistons 140 are made from a material having a thermal expansion coefficient that is lower than the thermal expansion coefficient of the material which the cylinder block 120 is made from. For example, the thermal expansion coefficient of the material of the pis-tons 140 may be lower than 60% of the thermal expansion coefficient of the material of the cylinder block 120. In one such example, the cylinder block 120 may be made from aluminum and the pistons 140 may be made from steel, but other materials are possible.

The connecting rods 141 may be made from steel too, or from any other material having a thermal expansion coefficient that is lower than the thermal expansion coefficient of the material which the cylinder block 120 is made from, for example rower than 60% thereof.

The cylinder head 130 may be made from aluminum, generally from the same material of the cylinder block 120, or other material having a similar thermal expansion coefficient.

Each of the combustion chamber 150 is provided for receiving a fuel and air mixture (not shown), whose ignition results in hot expanding exhaust gasses causing the reciprocal movements of the piston 140. It should be observed that, due to the reciprocating movements of the piston 140, the volume of the combustion chamber 150 cyclically va-ries between a minimum value, reached when the piston 140 is at the top of its stroke, and a maximum value, reached when the piston 140 is at the bottom of its stroke. The ratio between the maximum value and the minimum value of the combustion chamber volume is conventionally referred as the compression ratio of the internal combustion engine 110.

Each of the combustion chambers 150 is supplied with fuel by at least one fuel injector and with air through at least one intake port 210. The fuel is provided at high pres- sure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pres-sure fuel pump 180 that increases 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 intake port 210 and alternately allow exhaust gases to exit through at least one exhaust port 220.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200.

An air intake pipe 205 may provide air from the ambient environment to the intake mani- fold 200. A forced air system such as a turbocharger 230, having a compressor 240 rota- tionally coupled to a turbine 250, may be provided. Rotation of the compressor 240 in-creases the pressure and temperature of the air in the intake pipe 205 and manifold 200.

An intercooler 260 disposed in the intake pipe 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250.

The exhaust gases exiting the turbine 250 are directed into an exhaust system 270. The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust after-treatment 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.

As shown in figure 3, the internal combustion engine 110 may include an engine coaling circuit 500. The engine cooling circuit 500 schematically comprises a coolant pump 505 that delivers a coolant, typically a mixture of water and antifreeze, from a coolant tank 510 to a plurality of coolant chambers internally defined by the cylinder block 120 and by the cylinder head 130, and a radiator 520 for cooling down the coolant, once it has passed through the coolant chambers and before it returns to the coolant tank 510. The coolant pump 505 is coupled and driven by an electric motor 515, which allows to regu-late the flow of the coolant that is supplied into the coolant chambers, More particularly, for each of the cylinder 125, the coolant chambers include two separated coolant jackets surrounding the cylinder 125, including a first coolant jacket 525 and a second coolant jacket 530. The second coolant jacket 530 is internally defined by the cylinder block 120 so as to be in heat exchange relation with an upper part 125' of the cylinder 125, namely the part which is closed by the cylinder head 130 to define the combustion chamber 150.

The first coolant jacket 525 is internally defined by the cylinder block 120 too, but it is in heat exchange relation with a lower part 125" of the cylinder 125, which is located below the upper part 125'. The first coolant jacket 525 is in communication with the coolant pump 505 and the radiator 520 independently from the second coolant jacket 530. More particularly, the first and the second coolant jackets 525 and 530 are in communication with the coolant pump 505 through a first feeding pipe 535 and a second feeding pipe 540 respectively, and they are also in communication with the radiator 520 through a first draining pipe 545 and a second draining pipe 550 respectively. An valve 555 is located in the first feeding pipe 535 to selectively allow or prevent the coolant to flow into the first coolant jacket 525. The valve 555 may be an on-off valve, which in operation may be on- ly completely closed or completely open. Alternatively, the valve 555 may be a modulat-ing controllable valve, which also allows a flow regulation between the completely closed and completely open configuration. In order to allow this regulation, a modulating control- lable valve may generally differ from an on-off valve either in the structural design (hard-ware) or in the control system (software) associated thereto. The engine cooling circuit 500 may further comprise a coolant temperature sensor 560, which may be located in the second feeding pipe 540.

The internal combustion engine 110 may further include a dedicated piston cooling circuit 600 for cooling each of the reciprocating pistons 140, to modulate the temperature of the piston 140. The piston cooling circuit 600 may comprise an oil pump 605 that draws oil from an oil sump 610. The oil sump 610 may be fastened at the bottom of the cylinder block 120. The oil may be conventional lubricating oil. The oil pump 605 delivers the oil under pressure towards one nozzle 615 for each of the cylinders 125. According to an embodiment of the invention, a controlled valve 606 may be interposed between the oil pump 605 and the nozzle 615, in order to regulate the flow of oil delivered thereto. Each of the nozzles 615 jets the oil inside the respective cylinder 125 onto the bottom side of the piston 140 accommodated therein. In this way, the oil cools the pistons 140 down and then returns into the oil sump 610. The oil pump 605 is coupled and driven by an electric motor 620, which allows to regulate the flow of oil that is jetted toward the pistons 140. The oil jetted towards the pistons 140 may be previously cooled down by an oil coo- 3C ler 625, which is located between the oil sump 610 and the oil pump 605. The oil cooler 625 may be a conventional heat exchanger, wherein the heat of the oil is transferred to another coolant circulating in a specific circuit (not shown). The piston cooling circuit 600 may further comprise an oil temperature sensor 630, which may be located in the oil sump 610. It should be understood that the piston cooling circuit 600 described above is separated by the engine cooling circuit 500 described above, as well as by the engine lubricating circuit (not shown) which is conventionally provided for lubricating the sliding and rotating components of the internal combustion engine 110, such as for example the crankshaft bearings (main bearings and big-end bearings), camshaft bearings operating the valves, tappets and the like.

The automotive system 100 may further include an electronic control unit (ECU) 700 in communication with one or more sensors and/or devices associated with the internal combustion engine 110. The ECU 700 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters asso-ciated with the internal combustion engine 110. The sensors include, but are not limited to a crankshaft position sensor 705, an accelerator pedal position sensor 710, the coo- lant temperature sensor 560, the oil temperature sensor 630, and an engine metal tern- perature sensor 715 provided for measuring the temperature of a metal block of the in-ternal combustion engine 110, such as for example the cylinder black 120 or the cylinder head 130. Furthermore, the ECU 450 may generate output signals to various control de-vices that are arranged to control the operation of the internal combustion engine 110, including, but not limited to the fuel injectors 160, the electric motor 515 of coolant pump 505, the valve 555, the electric motor 620 of the oil pump 605, and the controlled valve 606. Note, dashed lines are used to indicate communication between the ECU 700 and the various sensors and devices, but most of them are omitted for clarity.

Turning now to the ECU 700, this apparatus may include a digital central processing unit (CPU) in communication with a data carrier 720 and an interface bus. The data carrier 720 may include various storage types including optical storage, magnetic storage, solid 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 CPU is configured to execute instructions stored as a program in the data carrier 720, and send and receive signals to/from the interface bus. The pro-gram may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the internal combustion engine 110.

In particular, from the starting of the internal combustion engine 110, the ECU 700 is configured to constantly monitor a parameter indicative of an engine temperature. This engine temperature parameter may be the engine metal temperature measured by the sensor 715, the coolant temperature measured by the sensor 560 or the oil temperature measured by the sensor 630.

Soon after the starting, the internal combustion engine 110 is still cold and its compres- sion ratio depends only on the constructional dimensions of the cylinders 125, the pis- tons 140, the connecting rods 141 and the crankshaft 145. These constructional dimen-sions may be chosen so that, in this condition, the compression ratio has a relatively high value, such as for example 16.0 in case of Diesel engine, in order to facilitate the crank-ing of the internal combustion engine 110 when it is cold.

As long as the monitored value of the engine temperature parameter is below a first pre-determined threshold value Ti thereof, the ECU 700 keeps the coolant pump 505 of the engine cooling circuit 500 and the oil pump 605 of the piston cooling circuit 600 inactive, in order to speed-up the warm-up of the internal combustion engine 110. In this way, the temperatures of the cylinder block 120, the pistons 140 and the connecting rods 141 ra-pidly increases. The first threshold value Ti of the engine temperature parameter may be empirically determined during a calibration activity and stored in the data carrier 720. In this case, the first threshold value Ti may be a cylinder block temperature of 120°C, which generally corresponds to a piston temperature of about 300°C.

Since the cylinder block 120 is made from a material having a thermal expansion coeffi-cient higher than the material of the pistons 140, the elongation of each cylinder 125 is greater than the elongation of the correspondent piston 140, so that the compression ra-tio of the internal combustion engine 110 gradually decrease. This effect is enhanced by the fact that also the connecting rod 141 is made from a material having a thermal ex-pansion coefficient lower than that of the cylinder block material. In this way, when the engine temperature parameter reaches the above mentioned first threshold value Ti, the compression ratio of the internal combustion engine 110 has a relatively low value, such as for example 15.3, which is advantageous for reducing the polluting emission (particu- larly NOX) and the noises generated by the internal combustion engine 110 when it is al-ready warmed-up.

When the monitored value of the engine temperature parameter exceeds the first thre-shold value Ti, the ECU 700 may activate the electric motor 620 of the oil pump 605, in order to jet oil onto each of the pistons 140 and cool the latter down. Afterwards, the ECU 700 may operate and control the oil pump 605 on the basis of other engine operat-ing parameters, such as for example the engine load measured by the pedal position sensor 710 and/or the engine speed measured by the crankshaft position sensor 705. In this way, the temperature of each piston 140 may be reduced and then kept at a very low value, for instance of about 180°C. The ECU 700 may also control the operation of the controllable valve 606, in order to regulate the flow of oil towards the piston 140, for ex- ample on the basis of the driving conditions as represented by the above mentioned en-gine operating parameters. This solution helps to save energy and therefore to reduce the fuel consumption.

At the same time, as soon as the monitored value of the engine temperature parameter exceeds the first threshold value 11, the ECU 700 may activate also the coolant pump 505, in order to cool the cylinder block 120 for preventing thermal-structural problem.

As long as the monitored value of the engine temperature parameter is below a second threshold value T2 thereof, which is greater than the first threshold value Ti, the ECU

S

700 may keep the valve 555 closed1 so that the coolant flows through the second coolant jacket 530 only. In this way, the upper portion 125' of the cylinder 125, which is more af- fected by the heat generated by the fuel combustion, is effectively cooled down to pre-vent damages, whereas the temperature of the lower portion 125" may still increase. The second threshold value T2 of the engine temperature parameter may be empirically de-termined during a calibration activity and stored in the data carrier 720. In this case, the second threshold value T2 may be a cylinder block temperature of about 150°C.

When the monitored value of the engine temperature parameter exceeds the second threshold value T2, the ECU 700 may open the valve 555 and operate the coolant pump 505, in order to keep the temperature of the cylinder block 120 constant. In particular, the ECU 700 may operate and control the coolant pump 505 on the basis of other engine operating parameters, such as for example the engine load measured by the accelerator pedal position sensor 710 and/or the engine speed measured by the crankshaft position sensor 705. In this way, with the temperature of the cylinder block 120 at about 150°C and the temperature of the pistons 140 at about 180°C, the different elongation of each cylinder 125 with respect to the corresponding piston 140 and connecting rod 141 may cause the compression ratio of the internal combustion engine 110 to reach a very low value, for instance of about 14.8, which further reduces the polluting emissions and the noises.

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 forgoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment1 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 in their legal equivalents.

REFERENCES

automotive system internal combustion engine 120 cylinder block cylinder cylinder head camshaft piston 141 connecting rod crankshaft combustion chamber fuel injector fuelrail 180 fuelpump fuel source 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 aftertreatment devices 500 engine cooling circuit 505 coolant pump 510 coolant tank 515 electric motor 520 radiator 525 first coolant jacket 530 second coolant jacket 535 first feeding pipe 540 second feeding pipe 545 first draining pipe 550 second draining pipe 555 valve 560 coolant temperature sensor 600 piston cooling circuit 605 oil pump 606 controlled valve 610 oil sump 615 nozzle 620 electric motor 625 oil cooler 630 oil temperature sensor 700 ECU 705 crankshaft position sensor 710 accelerator pedal position sensor 715 engine metal temperature sensor 720 data carrier Ti first threshold value T2 second threshold value

Claims

<claim-text>CLAIMS1. An internal combustion engine (110) comprising a cylinder block (120) defining at least a cylinder (125), and a reciprocating piston (140) accommodated inside the cylinder (125), wherein the piston (140) is made from a material having a thermal expansion coefficient lower than a thermal expansion coefficient of a material which the cylinder block (120) is made from.</claim-text> <claim-text>2. An internal combustion engine (110) according to claim 1, wherein the thermal ex- pansion coefficient of the piston material is lower than 60% of the thermal expan-sion coefficient of the cylinder block material.</claim-text> <claim-text>3. An internal combustion engine (110) according to any of the preceding claims, wherein the piston material is steel and the cylinder block material is aluminum.</claim-text> <claim-text>4. An internal combustion engine (110) according to any of the preceding claims, wherein the piston (140) is coupled to rotate a crankshaft (145) by means of a con-necting rod (141) made from a material having a thermal expansion coefficient lower than the thermal expansion coefficient of the cylinder block material.</claim-text> <claim-text>5. An internal combustion engine (110) according to claim 4, wherein the thermal ex-pansion coefficient of the connecting rod material is lower than 60% of the thermal expansion coefficient of the cylinder block material.</claim-text> <claim-text>6. An internal combustion engine (110) according to any claim from 4 to 5, wherein the connecting rod (141) and the piston (140) are made from the same material.</claim-text> <claim-text>7. An internal combustion engine (110) according to any of the preceding claims, comprising a piston cooling circuit (600) which includes an oil pump (605) arranged to draw oil from an oil sump (610) and to deliver it to at least a nozzle (615) pro-vided for jetting the oil inside the cylinder (125) onto the piston (140).</claim-text> <claim-text>8. An internal combustion engine (110) according to claim 7, wherein the piston cool-ing circuit (600) comprises an oil cooler (625) located between the oil sump (610) and the nozzle (615).</claim-text> <claim-text>9. An internal combustion engine (110) according to any claim from 7 to 8, wherein an electric motor (620) is coupled to drive the oil pump (605) of the piston cooling cir-cuit (600).</claim-text> <claim-text>10. An internal combustion engine (110) according to any claim from 7 to9, comprising a sensor (560, 630, 715) for measuring a parameter indicative of an engine tem-perature, and an electronic control unit (700) connected with the sensor (560, 630, 715) and with the oil pump (605) of the piston cooling circuit (600), wherein the electronic control unit (700) is configured to: -monitor a value of the engine temperature parameter through the sensor (560, 630, 715), and -activate the oil pump (605) of the piston cooling circuit (600) lithe monitored value of the engine temperature parameter exceeds a predetermined thre-shold value (Ti) thereof.</claim-text> <claim-text>11. An internal combustion engine (110) according to any of the preceding claims, comprising an engine cooling circuit (500) which includes a coolant pump (505) ar-ranged to draw a coolant from a coolant tank (510) and to deliver it into at least a first coolant jacket (525) defined by the cylinder block (120) in heat exchange rela-tion with the cylinder (125).</claim-text> <claim-text>12. An internal combustion engine (110) according to claim 11, wherein an electric mo-tor (515) is coupled to drive the coolant pump (505) of the engine cooling circuit (500).</claim-text> <claim-text>13. An internal combustion engine (110) according to any claim from 11 to 12, compris-ing a sensor (560, 630, 715) for measuring a parameter indicative of an engine temperature, and an electronic control unit (700) connected with the sensor (560, 630, 715) and with the coolant pump (505) of the engine cooling circuit (500), wherein the electronic control unit (700) is configured to: -monitor a value of the engine temperature parameter through the sensor (560, 630, 715), and -activate the coolant pump (505) of the engine cooling circuit (500) if the moni-tored value of the engine temperature parameter exceeds a predetermined threshold value (Ti) thereof.</claim-text> <claim-text>14. An internal combustion engine (110) according to any of claim from 11 to 13, wherein the cylinder (125) has an upper part 025') which is closed by a cylinder head (130) cooperating with the piston (140) to define a combustion chamber (150), and wherein the cylinder block (120) defines at least a second coolant jacket (530), which is in heat exchange relation with the upper part (125') of the cylinder (125) and which is connected with the coolant pump (505) through a second pipe (540) separated by a first pipe (535) connecting the coolant pump (505) to the first coolant jacket (525), a valve (555) being located in the first pipe (535) for selective-ly prevent the coolant to flow from the coolant pump (505) to the first coolant jacket (525).</claim-text> <claim-text>15. An internal combustion engine 010) according to claim 14, comprising a sensor (560, 630, 715) for measuring a parameter indicative of an engine temperature, and an electronic control unit (700) connected with the sensor (560, 630, 715) and with the valve (555) of the engine cooling circuit (500), wherein the electronic con-trol unit (700) is configured to: -monitor a value of the engine temperature parameter through the sensor (560, 630, 715), and -keep the valve (555) of the engine cooling circuit (500) closed if the moni-tored value of the engine temperature parameter is below a predetermined threshold value (12) thereof.</claim-text>