Engine with piston heating system and method of operating the same

Abstract

Methods and systems are provided for actively heating pistons in combustion chambers to reduce torque imbalance in an engine. In one example, a method for operating an engine includes determining a variance between compression ratios in a first combustion chamber and a second combustion chamber, and operating a piston heating system to apply a target amount of heat to a first piston assembly based on the variance between the compression ratios, the first piston assembly including a first piston positioned within the first combustion chamber.

Description

TECHNICAL FIELD

[0001] The present specification generally relates to an engine having a piston heating system and to a method of operating an engine having a piston heating system designed to adjust a compression ratio in a combustion chamber in the engine.

[0002] BACKGROUND / SUMMARY

[0003] Variations in cylinder compression ratios can occur in an engine due to manufacturing tolerances of different components and stack-up tolerances in component groups. For example, tolerances of components that affect piston squish height and bowl volume can cause variations in cylinder compression in a multi-cylinder engine. Typically, the compression ratio can vary from cylinder to cylinder by + / - 1.0%, for example, which can cause variations in power produced by each cylinder. As a result, the power and fuel consumption of the engine can be reduced and the drivability of a vehicle in which the engine is located can be adversely affected. These problems can be particularly prevalent in compression ignition engines. However, variations in compression ratio can also adversely affect spark ignition engines.

[0004] One example approach shown in Cannata, U.S. 7,827,943 B2, includes a system that changes the compression ratio in a cylinder by a mechanical assembly that adjusts the position at which a connecting rod and a piston are attached. However, Cannata’s system achieves compression ratio adaptability at the expense of engine reliability. For example, Cannata’s mechanical compression ratio adjustment system can be prone to breakdowns and malfunctions due to the complexity of the mechanical components used to adjust the compression ratio.

[0005] The inventors have recognized the above-described problems of previous engines and, in the face of these challenges, in one example, developed a method for operating an engine to address these problems. The method includes determining a variation between compression ratios in a first combustion chamber and a second combustion chamber and operating a piston heating system to apply a target amount of heat to a first piston assembly based on the variation between the compression ratios, the first piston assembly including a first piston positioned within the first combustion chamber. In this way, through a robust and reliable compression ratio adjustment system, the compression ratio of each cylinder can be adjusted to reduce the variation between the compression ratios in the engine and stabilize the amount of torque produced by the cylinders, if desired. As a result, engine efficiency can be improved while reducing noise, vibration, and harshness (NVH) caused by torque imbalances. This compression ratio adjustment is also performed using a reliable system that is not prone to breakdowns. As a result, drivability and reliability of a vehicle can be improved, thereby improving customer satisfaction.

[0006] In one example, operating the piston heating system can include activating a heater connected to a lubrication line that includes a nozzle that directs lubricant to a first piston rod connected to the first piston and crankshaft during engine operation. In this way, a piston assembly heater can be incorporated into a lubrication system in order to cause compression ratio adjustment in an efficient and reliable manner.

[0007] In another example, the amount of heat delivered to the combustion chambers in the engine can be varied based on engine load. In this example, during low load conditions (e.g., when the engine load is below a predetermined threshold value), a piston assembly heater connected to the first and second combustion chambers can be activated or operated to increase the amount of heat delivered to the combustion chambers, thereby increasing the compression ratio in the combustion chambers. Thus, the piston heating system can also be used to improve combustion efficiency in the engine, for example, during low load conditions.

[0008] It should be appreciated that the above Summary is provided merely for purposes of summarizing an array of concepts that are further described below in the DETAILED DESCRIPTION. This Summary is not intended to identify key or essential BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A schematic diagram of an internal combustion engine including a piston heating system is shown.

[0010] Figure 2 A cross-sectional view of a first example of an engine and piston heating system is shown. Figure 1

[0011] Figure 3 A cross-sectional view of a second example of an engine and piston heating system is shown. Figure 1

[0012] A method for operating an internal combustion engine and piston heating system is shown. Figure 4

[0013] Another method for operating an internal combustion engine and piston heating system is shown. Figure 5

[0014] A timing diagram of an example piston heating system control strategy is shown. Figure 6 DETAILED DESCRIPTION

[0015] ​​The following description relates to a piston heating system and a method for operating a piston heating system to adjust a compression ratio in one or more combustion chambers in an engine. The piston heating system includes a piston assembly heater that provides independent targeted heating to an engine piston assembly (e.g., a piston and a piston rod) such that the compression ratio of an associated combustion chamber can be changed. As defined herein, the compression ratio is a value that represents the ratio of the volume of a combustion chamber at its maximum capacity to the volume at its minimum capacity. It will be appreciated that heating or cooling a piston assembly can increase or decrease the compression ratio of a combustion chamber due to the material properties of the piston, piston rod, cylinder block, and cylinder head. Specifically, temperature affects the volume shape of a piston in all directions. If a piston is heated isothermally, then the volume shape of the piston expands in all directions. However, in a real engine, the piston temperature is not isothermal, so the expansion along any axis X (width, height, radius) can vary according to a function Cexp = dT / dX, where Cexp is the coefficient of thermal expansion of the piston material. When variations in the compression ratio are ascertained, for example, from pressure or proximity sensor signals, the piston assembly (e.g., a piston and a piston rod) corresponding to a combustion chamber with a smaller compression ratio can be heated to reduce the compression ratio variation. Thus, engine efficiency can be improved while reducing noise, vibration, and harshness (NVH) in the engine. Moreover, it will be appreciated that the piston heating system is more reliable than previous mechanical systems for adjusting cylinder compression ratios. Additionally, the piston heating system can also be designed to heat the piston and / or piston rod during low load and cold start conditions to further improve engine efficiency.

[0016] Figure 1 A schematic view of an engine employing a piston heating system designed to change combustion chamber compression ratios in the engine is shown. Figure 2 A first example of a piston heating system with a lubricant heater is shown. Figure 3 A second example of a piston heating system with an induction heater is shown. Figure 4 and Figure 5 A method for operating an engine and a piston heating system to adjust compression ratios in the engine is shown. Figure 6 A timing diagram of an example piston heating system control strategy for reducing torque imbalance and improving engine efficiency in an engine is shown.

[0017] Turning to Figure 1 , an engine 10 with a piston heating system 12 in a vehicle 14 is shown schematically. Although Figure 1 schematic views of various engine and piston heating system components are provided, it will be appreciated that at least some of the components can have different spatial locations and greater structural complexity than the components shown. Figure 1 Structural details of the components are discussed in greater detail herein with respect to Figures 2-3 Structural details of the components are discussed in greater detail herein with respect to

[0018] Figure 1 Also shown is an intake system 16 that provides intake air to the first and second combustion chambers 18, 20. A first piston 17 is positioned in the first combustion chamber 18, and a second piston 19 is positioned in the second combustion chamber 20. The pistons 17 and 19 are connected to a crankshaft 21 via mechanical components 23 (e.g., piston rods). Each pair of pistons and associated mechanical components (e.g., piston rods) can be referred to as a piston assembly. The combustion chambers 18 and 20 are formed by a cylinder block 22 that is connected to a cylinder head 24. Although Figure 1 The engine 10 is depicted as having two combustion chambers. However, in other examples, the engine 10 can have an alternative number of combustion chambers. For example, in other examples, the engine 10 can include a single combustion chamber, three combustion chambers, six combustion chambers, eight combustion chambers, etc. Moreover, in some examples, the combustion chambers can be arranged in different groups. For example, the first combustion chamber 18 can be arranged in a first cylinder group, while the second combustion chamber 20 can be arranged in a second cylinder group.

[0019] The intake system 16 includes an intake duct 26 and a throttle valve 28 connected to the intake duct. The throttle valve 28 is configured to adjust the flow of air provided to the combustion chambers 18 and 20. In the depicted example, the intake duct 26 feeds air to an intake manifold 30. In turn, the intake manifold 30 directs air to the first and second intake valves 32, 34 via first and second intake runners 36, 38, respectively. However, in other examples, such as in the case of a single cylinder engine, the intake duct 26 can direct intake air directly to an intake valve in one combustion chamber.

[0020] Intake valves 32 and 34 can be actuated by intake valve actuators 40 and 42, respectively. Likewise, exhaust valves 44 and 46 can be actuated by exhaust valve actuators 48 and 50, respectively. In one example, intake valve actuators 40 and 42 and exhaust valve actuators 48 and 50 can employ cams connected to intake and exhaust camshafts (not shown) to open / close the valves, respectively. Continuing the cam-driven valve actuator example, the intake and exhaust camshafts can be rotatably connected to a crankshaft. Further, in such an example, the valve actuators can utilize one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and / or variable valve lift (VVL) systems to vary the operation of the valves. Thus, if desired, cam timing devices can be used to vary the valve timing. It will be appreciated, therefore, that valve overlap can occur. In another example, intake and / or exhaust valve actuators 40, 42, 48 and 50 can be controlled by electronic valve actuation. For example, valve actuators 40, 42, 48 and 50 can be electronic valve actuators controlled by electronic actuation. In yet another example, engine 10 can alternatively include exhaust valves controlled by electric valve actuation and intake valves controlled by cam actuation including a CPS and / or VCT system, or vice versa. In still other embodiments, intake and exhaust valves can be controlled by a common valve actuator or actuation system.

[0021] Engine 10 also includes a lubrication system 52 that provides lubricant to engine components such as pistons 17 and 19, crankshaft 21, mechanical components 23, etc. Lubrication system 52 includes a lubricant reservoir 54 that receives lubricant from lubricated components (e.g., pistons, crankshaft, piston rods, etc.). Accordingly, lubricant reservoir 54 in lubrication system 52 can be designed to receive drain oil from lubricated components such as pistons 17 and 19, crankshaft 21, mechanical components 23, etc. For example, lubricant reservoir 54 can be located below lubricated components to receive oil that has been sprayed or otherwise delivered to the lubricated components. In the illustrated example, a lubricant pump 56 is positioned in lubricant reservoir 54. However, in other examples, lubricant pump 56 can be positioned outside of the lubricant reservoir with a pickup line extending into the reservoir. Lubricant pump 56 is configured to flow pressurized lubricant to a plurality of lubrication lines 58. The plurality of lubrication lines 58 are shown schematically. However, it should be appreciated that lubrication lines can extend through different sections of cylinder block 22 and / or cylinder head 24 to provide lubricant to pistons 17 and 19, crankshaft 21, mechanical components 23, etc. Lubrication system 52 can also include nozzles designed to spray or otherwise direct lubricant to pistons, crankshafts, etc., and are discussed in greater detail herein with respect to Figure 2 and Figure 3 Figure 2 and Figure 3

[0022] ​​The piston heating system 12 includes a first piston assembly heater 62 connected to the first combustion chamber 18 and a second piston assembly heater 64 connected to the second combustion chamber 20. The piston assembly heaters 62 and 64 are configured to provide different amounts of heat to the pistons 17 and 19. Varying the amount of heat provided to the pistons enables adjustment of the compression ratio in the combustion chambers. In this manner, the compression ratio in a particular cylinder can be adjusted to reduce torque imbalance in the engine and improve combustion efficiency in the engine 10. Control strategies for varying the compression ratio in an engine are discussed in more detail herein. In one example, the first piston assembly heater 62 and / or the second piston assembly heater 64 can be an electric heater designed to heat a lubricant directed to the first piston 17, the second piston 19, and / or a mechanical component 23 (e.g., a piston rod) connected to the pistons. In such an example, the energy storage device 66 can deliver electrical power to the first piston assembly heater 62 and the second piston assembly heater 64. However, in other examples, the first piston assembly heater 62 and / or the second piston assembly heater 64 can be an induction heater designed to provide a target amount of heat to the first piston 17, the second piston 19, and / or the mechanical component 23 (e.g., a piston rod) via induction heating. Specifically, in one example, the induction heater can be designed to heat the piston rod as it descends below the combustion chamber liner. Further, in other examples, the first piston assembly heater 62 and / or the second piston assembly heater 64 can include a heat exchanger configured to transfer heat from engine coolant to a lubricant delivered to the first piston 17, the second piston 19, and / or a mechanical component 23 (e.g., a piston rod) connected to the pistons and the crankshaft 21. In this manner, excess heat in the engine cooling system can be transferred to the piston heating system to improve engine efficiency. Other types of piston assembly heaters that can be used in the piston heating system include electric heating elements, heat pump devices, coolant-to-oil heat exchangers, etc. It should be appreciated that heating the piston assembly (e.g., the piston and / or the piston rod) allows the piston and / or the piston rod to thermally expand to increase the combustion ratio of the corresponding combustion chamber. The thermal expansion of the piston and the piston rod can be proportional to their vertical length. In some examples, the piston rod can be taller (e.g., three times taller) than the piston. Thus, heating the piston rod can have a significant impact on the compression ratio growth.

[0023] The piston heating system 12 can be designed to vary the heat delivered to the target piston and / or piston rod to reduce the compression ratio variation in the engine 10. By reducing the compression ratio variation, the NVH in the engine is reduced while the combustion efficiency is improved. For example, if it is determined that one of the combustion chambers has a smaller compression ratio compared to the other combustion chamber, the piston and / or piston rod within the combustion chamber with the smaller compression ratio can be heated to increase the compression ratio of the combustion chamber. Thus, the compression ratio variation can be reduced. In one example, the piston heating system 12 can also be configured to deliver heat to the pistons 17 and 19 during low load and / or cold start conditions to further improve engine efficiency. The low load condition can be a condition in which the engine load is less than a threshold value, and the cold start condition can be a condition in which the engine temperature is less than a threshold value. In one example, the engine load threshold pressure can be 10 bar brake mean effective pressure (BMEP). However, it should be understood that the engine load threshold can depend on the size and application of the engine. In another example, in one case, the low load condition threshold can be approximately equal to the maximum BMEP experienced by the engine during city or highway drive cycles. It should also be understood that the engine load threshold can also be highly dependent on the transmission ratio or drive axle reduction ratio of the vehicle. In one example, in one case, the engine temperature threshold value can be equal to the coolant temperature of the engine at which the controller changes operating modes at approximately 65 °C. Alternatively, the engine temperature threshold value can be determined based on whether the exhaust manifold temperature or catalyst out temperature exceeds the T80 temperature of the catalyst, which is the temperature at which the catalyst converts 80% of the NOx or total hydrocarbon emission (THC) exhaust emissions.

[0024] The engine 10 additionally includes an engine cooling system 68 configured to remove heat from the engine 10 and, in particular, from the cylinder block 22 and the cylinder head 24. The engine cooling system 68 includes an engine coolant jacket 70. The engine coolant jacket 70 is shown positioned in the cylinder head 24. However, it should be appreciated that, in other examples, the cylinder block 22 can additionally or alternatively include a coolant jacket. Further, it should be appreciated that the engine coolant jacket 70 can include a plurality of passages that direct coolant around high temperature areas in the engine, such as the combustion chambers. The engine coolant jacket 70 includes an inlet 72 that receives coolant from a coolant pump 74 and an outlet 76 that delivers coolant to a heat exchanger 78 (e.g., a radiator) designed to remove heat from the coolant flowing therethrough. In this way, a coolant circuit can be formed in the engine cooling system 68. A coolant line 80 can also be included in the engine cooling system 68 having a valve 82 positioned in the coolant line. However, in other examples, only one of the coolant lines 80 can include a valve. The coolant line 80 can be configured to direct heated coolant through a lubrication line in the lubrication system to heat the lubricant. In such an example, the engine coolant can be used to heat the lubricant towards the pistons 17 and 19. Accordingly, in one example, the coolant line 80 can be included in the piston assembly heaters 62 and 64.

[0025] Figure 1 A fuel delivery system 84 is also shown. The fuel delivery system 84 provides pressurized fuel to fuel injectors 86. In the example shown, the fuel injectors 86 are direct fuel injectors connected to the first and second combustion chambers 18 and 20, respectively. Additionally or alternatively, the fuel delivery system 84 can also include port fuel injectors designed to inject fuel into the intake system 16 upstream of the combustion chambers. The fuel delivery system 84 includes a fuel tank 88 and a fuel pump 90 designed to flow pressurized fuel to downstream components. The fuel delivery system 84 can include conventional components such as a high pressure fuel pump, check valves, return lines, etc. to enable fuel to be provided to the injectors at a desired pressure.

[0026] Figure 1Also included in the illustrated vehicle 14 is an exhaust system 92 configured to manage exhaust gas from the combustion chambers 18 and 20. The exhaust system 92 includes exhaust valves 44 and 46 designed to open and close to allow and inhibit the flow of exhaust gas from the combustion chambers to downstream components. The exhaust system 92 also includes exhaust runners 93 providing fluid communication between an exhaust manifold 94 and the first and second combustion chambers 18 and 20. The exhaust system 92 also includes an emission control device 96 downstream of the exhaust manifold 94, which is connected to an exhaust pipe 98. The emission control device 96 can include filters, catalytic converters, absorbers, etc., for reducing exhaust tailpipe emissions.

[0027] Figure 1 Also shown in the middle is an exhaust gas recirculation (EGR) system 140. The EGR system 140 includes an EGR pipe 142 fluidly connected to the intake system 16 and the exhaust system 92. Thus, the EGR system 140 can be designed to flow exhaust gas from the exhaust system 92 to the intake system 16. The EGR system 140 also includes an EGR valve 144 configured to regulate the flow rate of exhaust gas flowing through the EGR pipe 142. Also included in the EGR system 140 is an EGR cooler 146. The EGR cooler 146 is configured to remove heat from exhaust gas flowing through the EGR pipe 142. For example, the EGR cooler 146 can include a coolant pipe that circulates coolant in the vicinity of the exhaust pipe. However, numerous EGR cooler designs have been contemplated.

[0028] During engine operation, the combustion chambers 18 and 20 typically undergo a four stroke cycle, which includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, typically the exhaust valve is closed and the intake valve is open. Air is introduced into the combustion chamber via the corresponding intake duct, and the piston moves to the bottom of the combustion chamber to increase the volume within the combustion chamber. The position where the piston is located near the bottom of the combustion chamber and at the end of its stroke (e.g., when the combustion chamber is at its maximum volume) is commonly referred to by those skilled in the art as the bottom dead center (BDC). During the compression stroke, both the intake and exhaust valves are closed. The piston moves toward the cylinder head to compress the air within the combustion chamber. The point where the piston is located at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber is at its minimum volume) is commonly referred to by those skilled in the art as the top dead center (TDC). During a process referred to herein as injection, fuel is introduced into the combustion chamber. During a process referred to herein as ignition, the injected fuel in the combustion chamber ignites via compression, causing combustion. In other examples, however, a spark from an ignition device can be used to ignite the air-fuel mixture in the combustion chamber. During the expansion stroke, the expanding gases push the piston back to the BDC. The crankshaft converts this piston motion into rotational torque of the rotational shaft. During the exhaust stroke, in conventional designs, the exhaust valve opens to release the residual combustion air-fuel mixture to the corresponding exhaust passage, and the piston returns to the TDC.

[0029] Figure 1 A controller 100 in the vehicle 14 is also shown. Specifically, the controller 100 is shown in Figure 1 a conventional microcomputer, which includes a microprocessor unit (CPU) 102, input / output ports (I / O) 104, read only memory (ROM) 106, random access memory (RAM) 108, keep alive memory (KAM) 110, and a conventional data bus. The controller 100 is configured to receive various signals from sensors connected to the engine 10. The sensors can include an engine coolant temperature sensor 120, an exhaust composition sensor 122, an exhaust gas flow sensor 123, an intake gas flow sensor 124, a combustion chamber temperature sensor 126, pressure transducers 128 connected to the combustion chambers 18 and 20, an engine speed sensor 130, a knock sensor 132, etc. In other examples, the sensors can additionally include proximity sensors connected to the combustion chambers 18 and 20. The pressure transducers and / or proximity sensors can be used to ascertain the compression ratio of the associated combustion chamber. In other examples, proximity sensors can be used in place of pressure transducers. Additionally, the controller 100 is also configured to receive a throttle position (TP) from a throttle position sensor 112 connected to a pedal 114 actuated by an operator 116.

[0030] Additionally, the controller 100 can be configured to trigger one or more actuators and / or send commands to components. For example, the controller 100 can trigger adjustments to the throttle 28, the lubrication system 52, the intake valve actuators 40 and 42, the exhaust valve actuators 48 and 50, the piston heating system 12, the engine cooling system 68, the EGR system 140, and / or the fuel delivery system 84. In particular, the controller 100 can be configured to send signals to the first piston assembly heater 62 and the second piston assembly heater 64 to adjust the amount of heat provided to the pistons. In one example, the controller 100 can also be configured to send control signals to the lubricant pump 56 to adjust the flow rate of heated lubricant provided to the pistons. Additionally, the controller 100 can be configured to send control signals to the valve 82 to vary the amount of coolant flow provided to the lubrication system 52. Furthermore, the controller 100 can be configured to send control signals to the fuel pump 90 and the fuel injectors 86 to control the amount and timing of fuel injection provided to the combustion chambers 18 and 20. In one example, the controller 100 can also be configured to send command signals to the EGR valve 144 and the EGR cooler 146.

[0031] Accordingly, the controller 100 receives signals from various sensors and employs various actuators to adjust engine operation based on the received signals and instructions stored in the controller’s memory (e.g., non-transitory memory). Thus, it should be understood that the controller 100 can send and receive signals from the piston heating system 12.

[0032] For example, adjusting the first piston assembly heater can include adjusting a piston assembly heater actuator to adjust the piston assembly heater. In yet another example, the amount of heat delivered to the pistons via the piston assembly heaters 62 and 64 can be empirically determined and stored in predetermined lookup tables and / or functions. For example, one table can correspond to determining the amount of piston heating delivered to the pistons when there is a variation in the combustion chamber compression ratio, one table can correspond to determining the amount of piston heating delivered to the pistons in the engine based on changes in engine load. These tables can be tied to engine operating conditions such as engine temperature and engine load, among other engine operating conditions. Furthermore, the tables can output the amount of fuel to be injected into the combustion chamber via the fuel injectors at each cylinder cycle.

[0033] Figure 2 A first example of an internal combustion engine 200 and a piston heating system 202 is shown in cross-section. Figure 2 and Figure 3 A z-axis and an x-axis are provided for reference in FIGS. 1-3. In one example, the z-axis can be parallel to the gravitational axis. However, other z-axis orientations have been contemplated in other examples. It should be understood that the z-axis and the x-axis are provided for reference only and that the engine can be oriented in any direction.Figure 2 The engine 200 and the piston heating system 202 shown are Figure 1 The engine 10 and the piston heating system 12 shown are Figure 2 The engine 200 and the piston heating system 202 shown can include Figure 1 The engine 10 and the piston heating system 12 shown can include the features of the engine 200 and the piston heating system 202 shown, or vice versa.

[0034] Figure 2 An engine 200 is shown that includes a cylinder block 204 connected to a cylinder head 206 forming a combustion chamber 208. Although Figure 2 Only one cylinder is depicted in the engine 200, it should be understood that the engine 200 can include additional combustion chambers and piston heating system components similar to those shown in Figure 2 The other combustion chambers in the engine can include similar piston assembly heaters, lubrication lines, etc. Additionally, an exhaust valve 210 and an intake valve 212 are shown connected to the combustion chamber 208. Accordingly, Figure 2 An intake duct 214 and an exhaust duct 216 are also depicted in the engine 200 providing fluid communication between upstream intake system components and downstream exhaust system components.

[0035] A piston 218 is positioned within the combustion chamber 208. The piston 218 includes a piston ring 220 designed to seal the combustion chamber 208. A piston rod 222 is attached to the piston 218 and a crankshaft 224. The piston 218 and the piston rod 222 can be included in a piston assembly.

[0036] The piston heating system 202 includes a lubrication line 226 and a valve 228 connected to the lubrication line. The valve 228 is configured to regulate the amount of lubricant flowing to the lubrication line 226. The valve 228, as well as other lubricant valves described herein, can be an on / off electric solenoid valve, an on / off pneumatic solenoid valve, an on / off electric piezoelectric stack valve, an electric proportional valve, or a pneumatic proportional valve.

[0037] A nozzle 230 is positioned at the end of the lubrication line 226. The nozzle 230 is designed to direct a spray of lubricant toward an underside 232 of the piston 218. The piston heating system 202 also includes a piston assembly heater 234 connected to the lubrication line 226. In one example, the piston assembly heater can be an electric heater. However, in other examples, the piston assembly heater can receive heated coolant from Figure 1 The engine cooling system 68 shown is configured to heat the coolant to heat the lubricant flowing through the lubrication line 226.

[0038] The piston heating system 202 can also include a lubricant line 240 and a valve 238 connected to the lubricant line. The valve is configured to regulate the amount of lubricant that flows to the lubricant line 240. A nozzle 242 is positioned at the end of the lubricant line 240. The nozzle 242 is designed to spray lubricant toward the piston rod 222. Another piston assembly heater 244 can be connected to the lubricant line 240. However, in other examples, only one of the piston assembly heaters 234 and 244 can be included in the piston heating system 202. Again, in one example, the piston assembly heater 244 can be an electric heater, or in other examples, can receive heated coolant from the engine cooling system, as previously discussed. When the piston assembly heater receives heated coolant from the engine cooling system, the flow of coolant to the heater can be varied to adjust the amount of heat provided by the piston assembly heater to the lubricant flowing therethrough.

[0039] Figure 2 Also shown in FIG. 2 is a pressure sensor 246 (e.g., a pressure transducer). The pressure sensor 246 extends through the cylinder head 206 into the combustion chamber 208. The pressure sensor 246 is configured to sense the pressure in the combustion chamber 208. The pressure signal from the pressure sensor 246 can be used to determine the compression ratio of the combustion chamber. In other examples, the engine 200 can additionally or alternatively include a proximity sensor that senses the proximity of the piston to an upper portion of the cylinder head 206 to enable determination of the compression ratio of the combustion chamber 208. In such examples, the proximity sensor can extend through the cylinder head in a similar manner as the pressure sensor. Also shown is a temperature sensor 248 that extends through the cylinder block 204 into the combustion chamber 208. The temperature sensor 248 is configured to determine the temperature in the combustion chamber 208. The engine 200 also includes an engine speed sensor 250 connected to the crankshaft 224 that is designed to sense the rotational speed of the crankshaft.

[0040] Also shown is a direct fuel injector 252 connected to the combustion chamber 208. However, a port fuel injector can additionally or alternatively be included in the engine. It should be understood that the valve 228, the valve 238, the piston assembly heater 234, and the piston assembly heater 244 can be removed from the engine 200 and replaced with other components, such as a fuel injector, a spark plug, or other components. Figure 1The controller 100 shown receives control signals. Thus, the amount of heat delivered to the lubricant flowing through the lubrication lines 226 and 240 and the flow rate of the lubricant flowing through the lubrication lines can be varied. The variation in lubricant heating and / or lubricant flow rate enables the amount of heat delivered to the piston and / or piston rod to be varied, thereby causing a modulation of the compression ratio in the combustion chamber. For example, when the piston is heated, the axial length 253 of the piston increases, thereby decreasing the compression ratio in the combustion chamber 208. In one example, the piston can be composed of a metal such as steel, aluminum, etc. The growth of the piston can depend on the coefficient of thermal expansion, the thermal conductivity, and the heat transfer coefficient (e.g., conduction and / or convective heat transfer coefficient) of the piston. The coefficient of thermal expansion and the thermal conductivity are properties of the piston material, and can vary along the height of the piston if the piston is not composed of a single material, such as being an assembly of smaller parts having different materials (i.e., aluminum, steel, etc.) or alloys. The heat transfer coefficient varies depending on the surface area, roughness, and material of the piston. In one example, the bottom of the piston can be roughened to increase the surface area and enhance convective heat transfer, which will increase the sensitivity of the compression ratio to the cooling / heating jets and the heater. Furthermore, the cross-sectional shape of the piston will affect the thermal gradient within the piston, which will affect the sensitivity of the compression ratio to the cooling / heating jets and the heater.

[0041] Figure 3 Another example of an internal combustion engine 300 and a piston heating system 302 is shown in cross-section. The engine 300 and the piston heating system 302 are similar to the engine 10 and the piston heating system 12 shown in FIGS. 1-3, respectively, and thus features of the engine 10 and the piston heating system 12 shown in FIGS. 1-3 can be included in the engine 300 and the piston heating system 302 shown in FIG. 4, or vice versa. Furthermore, the internal combustion engine 300 and the piston heating system 302 can have similar features to the internal combustion engine 200 and the piston heating system 202 shown in FIGS. 5-7, respectively. Thus, redundant descriptions are omitted. Figure 1 The example of the engine 10 and the piston heating system 12 shown in FIGS. 1-3. Thus, Figure 3 The example of the engine 10 and the piston heating system 12 shown in FIGS. 1-3. Thus, Figure 1 The example of the engine 10 and the piston heating system 12 shown in FIGS. 1-3. Thus, Figure 2 The example of the engine 10 and the piston heating system 12 shown in FIGS. 1-3. Thus,

[0042] The engine 300 includes a cylinder block 304 connected to a cylinder head 306, thereby forming a combustion chamber 308. The engine 300 also includes a combustion chamber liner 310. Additionally, an exhaust valve 312 and an intake valve 314 are shown connected to the combustion chamber 308. Accordingly, Figure 3 The example of the engine 10 and the piston heating system 12 shown in FIGS. 1-3. Thus,

[0043] The piston heating system 302 includes an induction heater 320. The induction heater 320 can extend at least partially around a piston rod 322 that is connected to a piston 324 positioned in the combustion chamber 308. In one example, the induction heater 320 can include insulated wire that is repeatedly looped to form a ring commonly referred to as an induction coil. In some cases, the inner diameter of the induction coil can be no less than the bore diameter of the cylinder of the engine. Further, in such examples, the induction coil can be attached to the cylinder liner or the bottom of the bore such that the piston rod passes through the center of the induction coil. In one example, the induction coil can be wrapped around a bushing. In another example, the induction coil can be embedded in the block material. However, in these examples, the bushing and the engine block are typically composed of metal and, thus, would interfere with the induction heating of the piston rod. Continuing with the induction coil example, an alternating current can be applied to the induction coil that has an electrically conductive metal piece positioned within. The alternating current in the induction coil creates an eddy current inside the electrically conductive metal piece that heats the electrically conductive metal piece. It should also be understood that, in one example, the induction heater 320 can heat the piston rod 322 as it descends below the combustion chamber liner 310. In such examples, the induction heater 320 can not directly heat the piston but rather the piston rod, which in turn heats the piston. Thus, in one example, the induction heater 320 can be positioned vertically below the combustion chamber liner 310 to avoid directly heating the liner. However, other induction heater positions have been contemplated.

[0044] The piston rod 322 is also shown as being rotatably attached to a crankshaft 326. The induction heater 320 also extends through the combustion chamber liner 310. The induction heater 320 can be configured to heat the piston rod and / or the piston via induction. Thus, the induction heater 320 can include components such as electromagnets, electronic oscillators, coils, etc. that enable the creation of an eddy current in the piston rod and / or the piston to generate heat therein as discussed above. Using an induction heater to heat the piston has the benefit of operating the heating of the piston independently of the lubrication system. Further, the induction heater can provide targeted heating of the piston if desired to avoid unwanted heating of surrounding components.

[0045] An energy storage device 328 (e.g., battery, flywheel, capacitor, etc.) is configured to provide energy to the induction heater 320. It should be understood that, in some examples, the energy storage device 328 can provide energy to other engine systems. Further, in some examples, the energy storage device 328 can be recharged via an alternator connected to the crankshaft 326.

[0046] Figure 3A lubrication line 330 is also depicted. The lubrication line 330 includes a nozzle 332 positioned at one end. The nozzle 332 is configured to spray lubricant toward the piston rod 322. A valve 334 is also connected to the lubrication line 330. The valve 334 is designed to enable adjustment of the flow rate of lubricant through the lubrication line. The valve 334, the induction heater 320, and the energy storage device 328 can be from Figure 1 The controller 100 shown receives control signals to adjust operation of components.

[0047] Figure 3 A direct fuel injector 336 is also shown. Figure 3 A pressure sensor 338 (e.g., pressure transducer) is also shown in the example. The pressure sensor 338 extends through the cylinder head 306 into the combustion chamber 308. The pressure sensor 338 is configured to sense pressure in the combustion chamber 308. A temperature sensor 340 is also shown extending through the cylinder block 304 into the combustion chamber 308. The temperature sensor 340 is configured to determine temperature in the combustion chamber 308. The engine 300 also includes an engine speed sensor 342 connected to the crankshaft 326, which is designed to sense rotational speed of the crankshaft.

[0048] Additionally, in some examples, it will be appreciated that the engine 300 can include a set of pistons with corresponding induction heaters (such as the induction heater shown) and a set of pistons with corresponding lubrication line piston assembly heaters (such as the piston assembly heater shown). Figure 3 Figure 2

[0049] Figure 4 A method 400 for operating an engine with a piston heating system is shown. The method 400, as well as other methods described herein, can be implemented by the engine and piston heating system described above with respect to Figures 1-3 or, in other examples, by other suitable engines and piston heating systems. Instructions for carrying out the method 400 and other methods described herein can be executed by a controller based on instructions stored in memory (e.g., non-transitory) that are executable by the controller and in conjunction with signals received from sensors in the engine and corresponding systems, such as the sensors described above with respect to Figures 1-3 The controller can employ engine actuators of the engine system to adjust engine operation according to the methods described below.

[0050] At 402, the method includes determining engine operating conditions. The engine operating conditions can include: combustion chamber pressure, intake flow rate, engine temperature, exhaust flow rate, exhaust composition, engine speed, engine load, combustion chamber temperature, piston position, etc.

[0051] ​​Next, at 404, the method includes determining whether the compression ratios of the plurality of combustion chambers are biased. Specifically, in one example, it can be determined whether the difference between the first compression ratio and the second compression ratio is greater than an acceptable value. In one example, the threshold value can be related to engine size, engine speed, and / or engine load. Further, in one example, the threshold value can be strongly correlated to the coefficient of variation (COV) of indicated mean effective pressure (IMEP). In such an example, for a given speed and load point of the engine, the COV of mean effective pressure (MEP) can be calculated and used to calculate the cycle to cycle + / - 3 sigma spread for each cylinder. Continuing with such an example, the maximum variation in cylinder to cylinder MEP due to compression ratio should not exceed the cycle to cycle 3 sigma spread of 3 sigma. Thus, the engine can have to be tested at different compression ratios to quantify the effect of compression ratio on MEP under the same calibration and boundary condition settings. Based on these measurements, the maximum compression ratio variation can be calculated for a given engine, speed, and load. In one example, the compression ratio variation between combustion chambers can be determined using Equation 1 shown below.

[0052]

[0053] (Equation 1)

[0054] However, other suitable techniques for determining compression ratio variation have been considered. In one example, the compression ratio in each of the combustion chambers can be determined based on a signal from a pressure sensor connected to the combustion chamber, a signal from a proximity sensor connected to the combustion chamber, and / or a signal from a temperature sensor connected to the combustion chamber.

[0055] If it is determined that the compression ratios are not biased (NO at 404), the method proceeds to 406. At 406, the method includes maintaining the engine operating parameters. Maintaining the engine operating parameters can include continuing the closure of the piston assembly heater and operating the lubrication system according to the predetermined control strategy.

[0056] On the other hand, if it is determined that there is a deviation between the compression ratios (YES at 404), the method proceeds to 408. At 408, the method includes operating a piston heating system to apply a target amount of heat to a piston assembly based on the compression ratio deviation, the piston assembly including at least a piston positioned within a combustion chamber. In another example, step 408 can include actively heating at least a first piston assembly including a first piston to reduce a torque imbalance between a first combustion chamber having the first piston positioned therein and a second combustion chamber having a second piston positioned therein. Further, in one example, operating the piston heating system to apply the target amount of heat to the piston assembly can include operating a piston assembly heater to initiate piston and / or piston rod heating. In one example, operation of the piston assembly heater can include sending power to an electric heater, the electric heater connected to a lubrication line that sprays lubricant toward an underside of the piston rod and / or piston. In other examples, operation of the piston assembly heater can include sending power to an induction heater designed to inductively heat the piston and / or piston rod. In another example, operation of the piston assembly heater can include increasing an amount of heated coolant provided to the piston assembly heater. In such an example, heat from the coolant flowing through the piston assembly heater is transferred to the lubricant flowing through the piston assembly heater. As previously discussed, the piston heating will increase the compression ratio in the corresponding combustion chamber. Further, in one example, the piston can only be heated when the engine coolant temperature is below a threshold value. In one example, the threshold temperature can be determined based on a temperature used to indicate a transition from a catalyst light-off mode to a standard operating mode. However, other techniques for determining the above-mentioned threshold have been contemplated.

[0057] Next at 410, the method includes inhibiting heating of a second piston via a piston heating system, the second piston positioned in a second combustion chamber. For example, activation of a second piston assembly heater designed to heat the second piston can be prevented. In other words, deactivation of the second piston assembly heater can be sustained. In this way, one piston assembly heater can be activated while the other piston assembly heater is deactivated to enable a reduction in the deviation between the compression ratios. As a result, torque imbalance in the engine can be reduced, thereby reducing NVH in the engine. The reduction in torque imbalance also enables improved combustion efficiency. Further, in other examples, the amount of heating of the second piston can be reduced rather than inhibiting heating of the second piston.

[0058] At 412, the method includes determining whether the engine load is increasing or decreasing. If the engine load is increasing, the method proceeds to 414. At 414, the method includes operating the piston heating system to decrease the amount of heat provided to the pistons in the engine. Operating the piston heating system to decrease the amount of heat provided to the pistons includes deactivating first and second piston assembly heaters corresponding to the first and second combustion chambers, respectively. In other examples, the output of the piston assembly heaters for each combustion chamber can be reduced to decrease the amount of heat provided to the pistons via the piston heating system. Reducing the compression ratio of the combustion chambers during high load conditions can improve combustion efficiency.

[0059] However, if the engine load is decreasing, the method proceeds to 416. At 416, the method includes operating the piston heating system to increase the amount of heat provided to the pistons in the engine. Operating the piston heating system to increase the amount of heat provided to the pistons includes activating first and second piston assembly heaters corresponding to the first and second combustion chambers, respectively, or increasing their heat output. Heating the pistons during low load conditions enables the compression ratio of the combustion chambers to be increased to improve combustion efficiency.

[0060] Figure 5 Another method 500 for operating an engine having a piston heating system is shown. As discussed above, the method, as well as other methods described herein, can be implemented by the engine and piston heating system described above with respect to Figures 1-3 or can be implemented by other suitable engines and piston heating systems.

[0061] At 502, the method includes determining an engine operating condition. The engine operating condition can include a combustion chamber pressure, an intake flow rate, an engine temperature, an exhaust flow rate, an exhaust composition, an engine speed, an engine load, a combustion chamber temperature, a piston position, etc.

[0062] Next at 504, the method includes determining whether a torque imbalance exists in the engine. In one example, a torque imbalance in the engine can be identified based on combustion chamber pressure signals. For example, if the amount of change in the compression ratio in the two combustion chambers is greater than a threshold value, a torque imbalance in the engine can be identified. In one example, the threshold value can be determined using the techniques described above with respect to Figure 4 However, other strategies for determining whether a torque imbalance is occurring have been contemplated. For example, a torque imbalance can be determined based on a comparison between the temperature and / or pressure in the first and second combustion chambers. Further, it should be appreciated that under certain conditions, the engine can be operated with a torque imbalance and during other conditions, operated without a torque imbalance.

[0063] If it is determined that there is no torque imbalance in the engine (NO at 504), the method proceeds to 506. At 506, the method includes maintaining engine operating parameters. Maintaining engine operating parameters can include continuing the closure of the piston assembly heater and operating the lubrication system according to a predetermined control strategy.

[0064] On the other hand, if it is determined that there is a torque imbalance in the engine (YES at 504), the method proceeds to 508. At 508, the method includes operating the piston heating system to apply a target amount of heat to the piston assembly corresponding to the combustion chamber to reduce the torque imbalance. For example, an electric or induction heater that provides heat to the piston and / or piston rod can be powered to increase the amount of heat provided to the piston to increase the compression ratio of the combustion chamber in which the piston resides.

[0065] At 510, the method includes determining whether a knock condition occurs in the engine. The knock condition can include one or more engine operating conditions that result in knock, such as engine temperature, engine speed, engine load, etc. In particular, in one example, a signal from a knock sensor coupled to the engine can be used to determine whether knock occurs in the engine. For example, if a signal from the knock sensor indicative of vibration exceeds a threshold value, it can be determined that knock occurs. Further, it will be appreciated that the engine can be operated in a knock condition. If no knock condition occurs in the engine (NO at 510), the method proceeds to 512. At 512, the method includes maintaining engine operating parameters. For example, a predetermined valve timing and / or injection timing strategy can be maintained.

[0066] On the other hand, if it is determined that knock conditions are occurring in the engine (YES at 510), the method proceeds to 514. At 514, the method includes adjusting engine operating parameters to reduce (e.g., stop or prevent) engine knock. Adjusting engine operating parameters to reduce (e.g., stop or prevent) engine knock can include retarding or advancing valve timing, retarding injection timing, and / or reducing fuel injection quantity. In this way, combustion efficiency in the engine can be improved by reducing engine knock. In one example, the EGR flow rate can be adjusted to reduce engine knock. For example, the flow rate of cooled EGR gas can be increased when knock is detected. This knock control strategy can be implemented in a compression ignition engine. In another example, in a spark ignition engine, the spark timing can be retarded to reduce (e.g., stop or prevent) knock. Continuing with the spark ignition example, the spark timing can be advanced to improve combustion efficiency when the engine is below the knock limit. In another example, the temperature of oil sprayed onto the piston assembly can be reduced to reduce (e.g., stop or prevent) knock. In another example, the pilot injection quantity can be increased to reduce (e.g., stop or prevent) knock. Pilot injection can be an injection event that occurs prior to the main fuel injection event. In yet another example, the injection timing can be retarded to reduce (e.g., stop or prevent) knock. Further, in some examples, knock reduction strategies can be used in combination to stop or prevent knock. Next at 516, the method includes determining whether the engine is below a threshold temperature. The threshold temperature can correspond to a cold start threshold temperature (e.g., 80°C). In one example, an engine temperature sensor can be used to determine the engine temperature. If it is determined that the engine is not below the threshold temperature (NO at 516), the method proceeds to 518. At 518, the method includes maintaining engine operating parameters, such as maintaining the current piston heating strategy. However, if it is determined that the engine is below the threshold temperature (YES at 516), the method moves to 520. At 520, the method includes operating the piston heating system to increase the amount of heat applied to the pistons in the engine. For example, the amount of heat generated by the piston assembly heaters that provide heat to the first and second pistons can be increased to reduce the cold start duration. Specifically, the piston heating system can be operated to increase the amount of heat delivered to the combustion chamber until the engine temperature exceeds the threshold temperature. As a result, engine emissions are reduced.

[0067] Now turning to Figure 6 , FIG. 600 depicts exemplary piston heating system control signals in conjunction with engine load and compression ratio for different combustion chamber profiles such as described in Figures 1-5 Figure 6 ​The examples of the plots are drawn to scale substantially, even though each point is not labeled with a numerical value. In this way, the relative variation in timing can be estimated by the size of the plot. However, other relative timings can be used if desired. Also, each of the plots and plot times are represented on the x-axis.

[0068] Continuing Figure 6 Plot 602 depicts the compression ratio of the first combustion chamber, and plot 604 depicts the compression ratio of the second combustion chamber (along the y-axis). Signal 606 indicates a control signal sent to the first piston assembly heater, and signal 608 indicates a control signal sent to the second piston assembly heater. Plot 610 depicts the engine load in the engine (along the y-axis). Figure 6 The control signals shown for the piston assembly heaters are intended for an electric heater or an induction heater. However, it should be understood that in other examples, control signals can be sent to piston assembly heaters that utilize heated engine coolant to warm engine lubricant directed to the pistons.

[0069] At to, there is a variation 612 between the compression ratio plots 602 and 604. Specifically, the compression ratio corresponding to the first combustion chamber is less than the compression ratio corresponding to the second combustion chamber. When this variation is identified, the first piston assembly heater is turned on at ti. Turning on the first piston assembly heater causes the pistons to heat up. When the first pistons are heated, the compression ratio of the first combustion chamber increases to reduce the variation between the compression ratios. Once the compression ratios are substantially equal or within an acceptable range, the first piston assembly heater is turned off, as shown at t2. Thus, when there is a deviation between the compression ratios in different combustion chambers, the pistons in the combustion chamber with the smaller compression ratio are heated to reduce the deviation between the compression ratios, thereby reducing the torque imbalance in the engine. As a result, the NVH in the engine is reduced and the engine efficiency is improved. Thus, the technical effect of heating the pistons to reduce the compression ratio variation is to reduce the NHV in the engine and improve combustion efficiency.

[0070] Additionally, the engine load plot 610 is above a threshold 614 until ti is reached. When the engine load decreases below the threshold 614, both the first piston assembly heater and the second piston assembly heater are turned on. In this way, the compression ratio of the combustion chambers in the engine can be increased during low load conditions to improve engine efficiency.

[0071] Further, in some examples, the piston assembly heater can be designed to output variable amounts of heat, such as in a step-wise fashion or a continuous fashion. In such examples, the degree to which the piston assembly heater outputs can be determined based on a variance between compression ratios of combustion chambers, engine load (e.g., a rate of change of engine load), engine temperature, and the like. In this way, the degree of piston heating can be fine-tuned based on engine operating conditions. Moreover, it should be appreciated that, Figure 6 The illustrated graphs are exemplary in nature, and in other examples, the compression ratio and piston heating system control scheme can be different.

[0072] Figures 1-3 Exemplary configurations are shown with relative positioning of various components. At least in one example, elements shown as directly contacting one another or directly connected can be referred to as being directly in contact or directly connected, respectively. Similarly, at least in one example, elements shown as connected or adjacent to one another can be referred to as being connected or adjacent to one another, respectively. As an example, components laid out in co-planar contact with one another can be referred to as being co-planarly in contact. As another example, in at least one example, elements positioned apart from one another such that only a certain space exists therebetween and no other components can be referred to as being such. As yet another example, elements shown as above / below one another, on opposite sides of one another, or to the left / right of one another can be referred to as being such relative to one another. Further, as shown in the figures, in at least one example, the top-most element or top-most point of an element can be referred to as the "top" of the component, while the bottom-most element or bottom-most point of an element can be referred to as the "bottom" of the component. As used herein, top / bottom, up / down, above / below can be relative to the longitudinal axis of the figures, and used to describe the positioning of elements of the figures relative to one another. As such, in one example, an element shown above other elements is positioned vertically above the other elements. As yet another example, the shapes of elements depicted in the figures can be referred to as having those shapes (e.g., such as circular, straight, planar, curved, rounded, chamfered, angled, etc.). Further, in at least one example, elements shown intersecting one another can be referred to as intersecting elements or as intersecting one another. Still further, in one example, an element shown within another element or shown outside of another element can be referred to as being such.

[0073] The present application will be further described in the following paragraphs. In one aspect, a method for operating an engine is provided. The method includes determining a variance between compression ratios in a first combustion chamber and a second combustion chamber, and operating a piston heating system to apply a target amount of heat to a first piston assembly based on the variance between the compression ratios, the first piston assembly including at least a first piston positioned within the first combustion chamber.

[0074] In another aspect, an internal combustion engine is provided. The internal combustion engine includes a first combustion chamber having a first piston positioned therein, the first piston connected to a crankshaft via a first piston rod; a second combustion chamber having a second piston positioned therein, the second piston connected to the crankshaft via a second piston rod; a piston heating system including a first heating device designed to provide heat to the first piston and a second heating device designed to provide heat to the second piston; and a controller including code stored in non-transitory memory, the code executable by a processor to: determine a variance between compression ratios of the first combustion chamber and the second combustion chamber; and operate the piston heating system to apply a target amount of heat to at least one of the first piston, the first piston rod, the second piston, and the second piston rod based on the variance between the compression ratios.

[0075] In another aspect, a method for operating an engine system is provided. The method includes actively heating at least a first piston assembly including a first piston to reduce a torque imbalance between a first combustion chamber and a second combustion chamber, the first combustion chamber having a first piston positioned therein and the second combustion chamber having a second piston positioned therein.

[0076] In any of these aspects herein, or a combination of these aspects, operating the piston heating system can include activating a heater connected to a lubrication line including a nozzle that directs lubricant to a first piston rod connected to the first piston and the crankshaft during engine operation.

[0077] In any of these aspects herein, or a combination of these aspects, operating the piston heating system can include activating a heater connected to a lubrication line including a nozzle that directs lubricant to an underside of the first piston during engine operation.

[0078] In any of these aspects herein, or a combination of these aspects, operating the piston heating system can include activating an induction heater connected to a section of a cylinder block adjacent to the first piston.

[0079] In any of these aspects herein, or a combination of these aspects, the method can further include inhibiting heating of a second piston assembly based on the variance between the compression ratios, the second piston assembly including at least a second piston positioned in the second combustion chamber.

[0080] In any of these aspects or combinations of aspects herein, the method can further include increasing a pilot injection amount into at least one of the first combustion chamber and the second combustion chamber to reduce knock in response to identifying the knock condition.

[0081] In any of these aspects or combinations of aspects herein, the method can further include increasing a flow rate of cooled exhaust gas recirculation in the engine to reduce knock in response to identifying the knock condition.

[0082] In any of these aspects or combinations of aspects herein, the variance between the compression ratios can be determined based on at least one of a combustion chamber pressure and a combustion chamber temperature.

[0083] In any of these aspects or combinations of aspects herein, the first heating device can be a heater connected to a lubrication line.

[0084] In any of these aspects or combinations of aspects herein, the lubrication line can include a nozzle that directs lubricant to the first piston rod connected to the first piston and the crankshaft during engine operation.

[0085] In any of these aspects or combinations of aspects herein, the first heating device can be an induction heater connected to a portion of a cylinder block adjacent to the first piston.

[0086] In any of these aspects or combinations of aspects herein, the internal combustion engine can be configured to implement compression ignition in the first combustion chamber and the second combustion chamber.

[0087] In any of these aspects or combinations of aspects herein, the first piston can be included in a first cylinder bank and the second piston is included in a second cylinder bank.

[0088] In any of these aspects or combinations of aspects herein, the method can further include determining a knock condition in the combustion chamber, and advancing a spark timing in the first combustion chamber to prevent knock in response to determining the knock condition.

[0089] In any of these aspects or combinations of aspects herein, the torque imbalance can be determined based on a comparison between at least one of a temperature and a pressure in the first combustion chamber and the second combustion chamber.

[0090] In any of these aspects or combinations of aspects herein, the method can further include inhibiting heating of a second piston assembly based on the torque imbalance, the second piston assembly including at least the second piston.

[0091] In any of these aspects or combinations of aspects herein, heating the first piston assembly can include actuating a heater connected to a lubrication line having a nozzle that sprays lubricant at a first piston rod connected to the first piston.

[0092] In any of these aspects or combinations of aspects herein, heating the first piston assembly can include actuating a heater connected to a lubrication line having a nozzle that sprays lubricant at an underside of the first piston.

[0093] In any of these aspects or combinations of aspects herein, the method can further include adjusting an amount of active heating of the first piston and actively heating the second piston based on a change in engine load.

[0094] In any of these aspects or combinations of aspects herein, the torque imbalance can be determined based on a comparison between temperatures in the first combustion chamber and the second combustion chamber.

[0095] In any of these aspects or combinations of aspects herein, the method can further include increasing an amount of heat delivered by the piston heating system to the combustion chamber during low load to increase the compression ratio of the combustion chamber.

[0096] In any of these aspects or combinations of aspects herein, the method can further include decreasing an amount of heat delivered to the combustion chamber during high load conditions to decrease the compression ratio of the combustion chamber.

[0097] In any of these aspects or combinations of aspects, the method can further include increasing an amount of heat delivered to the combustion chamber when the engine is below a threshold temperature.

[0098] In any of these aspects or combinations of aspects, the first piston assembly can include a first piston rod.

[0099] It should be noted that the example control and estimation routines included herein can be employed with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by control systems comprising controllers to implement various aspects of the exemplary embodiments described herein in combination with various sensors, actuators, and other engine hardware. The particular routines described herein can represent one or more of any number of processing strategies such as event-driven, intermittent, multitask, multithread, and the like. As such, various acts, operations, and / or functions illustrated can be performed in the manner shown, can be performed concurrently, or can be performed with steps that are added, omitted, or performed in an order other than as described. Similarly, the order in which some of the acts, operations, and / or functions are described is not necessarily the order in which these operations will be performed. The acts, operations, and / or functions can be repeated any suitable number of times, with or without iteration. Moreover, the described acts, operations, and / or functions can graphically represent code to be programmed into non-transitory memory of a computer readable storage medium in a computer readable storage medium to be executed by an electronic controller in a system including various engine hardware components, where the described acts are implemented by executing the instructions in combination with the electronic controller.

[0100] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6 cylinder, inline-4 cylinder, inline-6 cylinder, V-12 cylinder, opposed-4 cylinder, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or properties.

[0101] The following claims particularly point out certain combinations and subcombinations that are regarded as novel and nonobvious. These claims can be further combined with a dependent claim to provide yet a further set of examples and subcombinations. Inclusion of one or more integrations of one or more claims, whether dependent or independent, in the same application or in a related application, does not preclude the claim or claims from being combined with a dependent claim or claims in the same or a related application, whether such combinations are pursued then or at a later date. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties can be claimed through amendment of the following claims or presentation of additional claims in the application or related applications. Such amended claims, whether they expand the claims or narrow them, are intended to be within the subject matter of the disclosure.

[0102] According to the present disclosure, there is provided a method for operating an engine, comprising: determining a variance between compression ratios in a first combustion chamber and a second combustion chamber; and operating a piston heating system to apply a target amount of heat to a first piston assembly based on the variance between the compression ratios, the first piston assembly comprising at least a first piston positioned within the first combustion chamber.

[0103] According to one embodiment, operating the piston heating system includes activating a heater connected to a lubrication line that includes a nozzle that directs lubricant to a first piston rod connected to the first piston and the crankshaft during engine operation.

[0104] According to one embodiment, operating the piston heating system includes activating a heater connected to a lubrication line that includes a nozzle that directs lubricant to an underside of the first piston during engine operation.

[0105] According to one embodiment, operating the piston heating system includes activating an induction heater connected to a section of the cylinder block adjacent to the first piston.

[0106] According to one embodiment, the above invention is further characterized by inhibiting heating of a second piston assembly based on the variation between the compression ratios, the second piston assembly including at least a second piston positioned in the second combustion chamber.

[0107] According to one embodiment, the above invention is further characterized by increasing a lead injection amount into at least one of the first combustion chamber and the second combustion chamber to reduce knock in response to identifying a knock condition.

[0108] According to one embodiment, the variation between the compression ratios is determined based on at least one of a combustion chamber pressure and a combustion chamber temperature.

[0109] According to one embodiment, the first piston assembly includes a first piston rod.

[0110] According to the invention, there is provided an internal combustion engine having a first combustion chamber with a first piston positioned therein connected to a crankshaft via a first piston rod, a second combustion chamber with a second piston positioned therein connected to the crankshaft via a second piston rod, a piston heating system including a first heating device designed to provide heat to the first piston and a second heating device designed to provide heat to the second piston, and a controller including code stored in a non-transitory memory executable by a processor to determine a variation between compression ratios of the first combustion chamber and the second combustion chamber, and operate the piston heating system to apply a target amount of heat to at least one of the first piston, the first piston rod, the second piston, and the second piston rod based on the variation between the compression ratios.

[0111] According to one embodiment, the first heating device is a heater connected to a lubrication line.

[0112] According to one embodiment, the lubrication line includes a nozzle that directs lubricant to the first piston rod connected to the first piston and the crankshaft during engine operation.

[0113] According to one embodiment, the first heating device is an induction heater connected to a portion of the cylinder block adjacent to the first piston.

[0114] According to the present invention, there is provided a method for operating an engine system, comprising: actively heating a first piston assembly including at least a first piston to reduce a torque imbalance between a first combustion chamber having a first piston positioned therein and a second combustion chamber having a second piston positioned therein.

[0115] According to one embodiment, the above invention is further characterized by: determining a knock condition in the combustion chamber, and advancing a spark timing in the first combustion chamber to prevent knock in response to determining the knock condition.

[0116] According to one embodiment, the torque imbalance is determined based on a comparison between at least one of a temperature and a pressure in the first combustion chamber and the second combustion chamber.

[0117] According to one embodiment, the above invention is further characterized by: inhibiting heating of a second piston assembly including at least the second piston based on the torque imbalance.

[0118] According to one embodiment, heating the first piston assembly includes: actuating a heater connected to a lubrication line having a nozzle that sprays lubricant at a first piston rod connected to the first piston.

[0119] According to one embodiment, heating the first piston assembly includes: actuating a heater connected to a lubrication line having a nozzle that sprays lubricant at an underside of the first piston.

[0120] According to one embodiment, the above invention is further characterized by: adjusting an amount of active heating of the first piston and actively heating the second piston based on a change in engine load.

[0121] According to one embodiment, the first piston assembly includes a first piston rod.

Claims

1. A method for operating an engine, comprising: determining a variance between compression ratios in a first combustion chamber and a second combustion chamber; and operating a piston heating system to apply a target amount of heat to a first piston assembly based on the variance between the compression ratios, the first piston assembly including at least a first piston positioned within the first combustion chamber, wherein operating the piston heating system includes activating a heater connected to a lubrication line, the lubrication line including a nozzle that directs lubricant to a first piston rod connected to the first piston and a crankshaft during engine operation.

2. The method of claim 1, wherein operating the piston heating system comprises: activating the heater so that the nozzle directs lubricant to an underside of the first piston during engine operation.

3. The method of claim 1, wherein the other way of applying the target amount of the heat comprises: activating an induction heater connected to a section of a cylinder block adjacent to the first piston.

4. The method of claim 1, further comprising: inhibiting heating of a second piston assembly based on the variance between the compression ratios, the second piston assembly including at least a second piston positioned in the second combustion chamber.

5. The method of claim 1, further comprising: increasing a pilot injection amount into at least one of the first combustion chamber and the second combustion chamber to reduce knock in response to identifying a knock condition.

6. The method of claim 1, wherein the variance between the compression ratios is determined based on at least one of a combustion chamber pressure and a combustion chamber temperature.

7. The method of claim 1, wherein the first piston assembly includes the first piston rod.

8. The method of claim 1, further comprising: determining a knock condition in the combustion chamber, and advancing a spark timing in the first combustion chamber to prevent knock in response to determining the knock condition.

9. The method of claim 1, further comprising: adjusting an amount of target heating of the first piston and actively heating a second piston in the second combustion chamber based on a change in engine load.

10. An internal combustion engine, comprising: a first combustion chamber having a first piston positioned therein, the first piston connected to a crankshaft via a first piston rod; a second combustion chamber having a second piston positioned therein, the second piston connected to the crankshaft via a second piston rod; a piston heating system including a first heating device designed to provide heat to the first piston and a second heating device designed to provide heat to the second piston; and a controller including code stored in a non-transitory memory, the code executable by a processor to: determine a variance between compression ratios of the first combustion chamber and the second combustion chamber; and operate the piston heating system to apply a target amount of heat to at least one of the first piston, the first piston rod, the second piston, and the second piston rod based on the variance between the compression ratios, wherein the first heating device is a heater connected to a lubrication line, the lubrication line including a nozzle that directs lubricant to the first piston rod connected to the first piston and the crankshaft during engine operation.

11. The internal combustion engine of claim 10, wherein another form of the first heating device is an induction heater connected to a section of a cylinder block adjacent to the first piston.

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