JP6536422B2 - Piston cooling device for internal combustion engine and internal combustion engine having the same - Google Patents

Description

  The present invention relates to a piston cooling device for an internal combustion engine and an internal combustion engine provided with the same.

  The heat of the piston of the engine is dissipated to the cooling water of the water jacket through the cylinder. In recent years, the engine is required to have a high output while keeping the size of the engine small, and since the amount of heat generation is large, it is necessary to further dissipate heat.

  For this reason, in recent engines, an oil jet is adopted which injects lubricating oil to the back side of a piston to cool it. In particular, in a turbocharged engine in which the temperature of the piston tends to rise or a direct cylinder injection type engine having a cavity with a high thermal load, an annular cavity is formed in which a lubricating oil called cooling channel flows in the piston. The cooling effect of the jet is enhanced.

  Japanese Patent Laid-Open No. 10-68319 (Patent Document 1) discloses an engine that cools a piston having such a cooling channel (also called an oil gallery) by oil jet.

  Generally, oil jet lubricating oil is supplied from an oil pump. The oil pressure from the oil pump rises as the engine speed rises. When this oil pressure exceeds the pressure of the check valve provided in the lubricating oil supply path of the oil jet, the oil is injected and the piston is cooled. On the other hand, in the engine disclosed in the above-mentioned JP-A-10-68319, oil is injected from the oil jet in the high speed and high load area, and the injection of oil from the oil jet is stopped in the low, medium speed, low and medium load area. , Over cooling is suppressed.

Japanese Patent Application Laid-Open No. 10-68319

  The lubricating oil injected from the oil jet is charged into the interior of the cooling channel from the inlet of the cooling channel. The lubricating oil in the cooling channel is agitated by the upper and lower sides of the piston, and heat exchange with the piston takes heat of the piston and is discharged from the oil outlet. In order to achieve such good heat exchange by heat exchange, it is desirable that the filling ratio of the cooling channel by the lubricating oil be 50% or more on average.

  Therefore, in the engine disclosed in JP-A-10-68319, oil is constantly jetted from the oil jet in the high speed and high load region. However, when the piston is rising while the engine is rotating, the oil injection speed from the oil jet may fall below the piston speed, and the lubricating oil does not reach the inside of the cooling channel and does not contribute to the piston cooling.

  Therefore, oil injection from the oil jet at the time of piston rise causes unnecessary work of the oil pump. In addition, part of the lubricating oil that does not enter the cooling channel adheres to the cylinder inner wall surface (bore surface). When the adhesion amount of the lubricating oil to the cylinder inner wall surface becomes excessive, the piston ring is scraped up to the combustion chamber by the piston ring and burned with the fuel when the piston ascends, so the consumption amount of the lubricating oil increases.

  The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a piston cooling device for an internal combustion engine with an improved piston cooling efficiency for oil pump work, and an internal combustion engine having the same. To provide.

  The present invention relates to a piston cooling device of an internal combustion engine which cools a piston by an oil jet. Inside the piston is provided a cooling channel for cooling the piston by letting lubricating oil in and out. The piston cooling device controls the injection and the injection stop of the lubricating oil from the oil jet nozzle by opening and closing during one rotation of the crankshaft and an oil jet nozzle for injecting the lubricating oil toward the inlet of the cooling channel. And a solenoid valve. The solenoid valve closes in a first crank angle range that includes the crank angle corresponding to the piston position at which the speed at which the piston moves away from the oil jet nozzle is the fastest. The second crank angle range does not overlap with the first crank angle range. Open at

  Preferably, the control unit further includes a control unit that controls the solenoid valve. The control unit changes the open period of the solenoid valve in accordance with the flow rate of the lubricating oil required to cool the piston below the target temperature, which is determined based on the operating state of the internal combustion engine.

  More preferably, the control unit sets the open period of the solenoid valve longer as the spray angle indicating the spread of the injection of the lubricating oil from the oil jet nozzle determined based on the pressure and the temperature of the lubricating oil is wider.

  Preferably, when the crank angle corresponding to the top dead center of the piston is 0 °, the first crank angle range includes a range of at least 0 to 180 °.

  This invention is an internal combustion engine provided with the piston cooling device of any one of the said, in another aspect.

  According to the present invention, piston cooling efficiency for oil pump work is improved. In addition, the consumption of lubricating oil can be reduced.

FIG. 1 is a diagram showing a schematic configuration of an engine 1 provided with a cooling device according to Embodiment 1. It is the figure which expanded and showed the detail of a piston and an oil jet nozzle. It is a figure which shows spray angle (theta) of the oil injected from an oil jet nozzle. It is an operation | movement wave form diagram for demonstrating oil injection control in this Embodiment. FIG. 6 is a flowchart for describing control of an oil jet that is executed by the ECU in the first embodiment. FIG. FIG. 10 is a flowchart for describing an outline of injection control of an oil jet that is executed in Embodiment 2. FIG. It is a block diagram for demonstrating the detail of processes, such as estimation of a spray angle. It is a figure which shows an example of the engine oil temperature map referred in FIG. It is a figure which shows an example of the piston temperature map referred in FIG. It is a figure for demonstrating the relationship between a spray angle and the oil inflow to a cooling channel. It is a wave form diagram for explaining control which changes a valve-opening period of a solenoid valve according to a difference of a spray angle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated.

First Embodiment
FIG. 1 is a view showing a schematic configuration of an engine 1 provided with a cooling device according to a first embodiment. The engine 1 may include a plurality of cylinders, and a cross section of one cylinder is typically shown schematically in FIG.

  The engine 1 includes a cylinder head 2, a cylinder block 4, an oil pan 6, a piston 26, a crankshaft 27 and a connecting rod 28.

  Although not illustrated, each cylinder includes an injector (fuel injection valve) for injecting fuel into the combustion chamber, an intake valve for opening and closing an intake passage for supplying air into the combustion chamber, and an exhaust passage for discharging exhaust gas after combustion. The exhaust valve etc. which open and close are provided.

  A piston 26 is accommodated inside the cylinder, and the piston 26 is capable of reciprocating up and down. The piston 26 is connected to the crankshaft 27 via a connecting rod (connecting rod) 28. A crank angle sensor plate (pulsar plate) 14 is attached to the rotation shaft of the crankshaft 27. The crank angle is measured by the crank angle sensor 12 to obtain the engine rotation speed Ne.

  The cylinder block 4 is attached with an oil jet for injecting lubricating oil (hereinafter, simply referred to as oil) toward the back surface of the piston 26. The oil jet includes an oil jet nozzle 30 and a solenoid valve 29.

  Further, in the cylinder block 4, an oil passage 38 for supplying oil to the solenoid valve 29 is formed. An oil pressure sensor 37 is disposed in the oil passage 38, and the oil pressure Po is measured.

  Water jackets 22 and 24 are formed on the cylinder head 2 and the cylinder block 4 respectively. A water temperature sensor 36 is disposed in the water jacket 22, and the water temperature Tw of the engine cooling water is measured.

  An ECU (Electric Control Unit) 40 receives an accelerator opening Acc from an accelerator opening sensor (not shown), and receives a crank angle CA and an engine rotational speed Ne from the crank angle sensor 12. The ECU 40 further receives the water temperature Tw and the oil pressure Po from the water temperature sensor 36 and the oil pressure sensor 37, respectively. The ECU 40 controls the solenoid valve 29 based on the received signals.

  FIG. 2 is an enlarged view of the details of the piston and the oil jet. Referring to FIGS. 1 and 2, the piston 26 is formed with a cooling channel 32 into which the oil injected from the oil jet nozzle 30 is introduced. The oil jet injects oil toward the oil inlet 31 of the cooling channel 32 on the back surface of the piston 26. In FIG. 2, the piston 26 is located at the bottom dead center, and the tip of the oil jet nozzle 30 is shown to be closest to the oil inlet 31.

  The introduction of the oil into the cooling channel 32 efficiently cools the piston 26. The oil introduced into the cooling channel 32 is discharged from the oil discharge port 33 to the outside of the piston 26.

  FIG. 3 is a view showing the spray angle θ of oil jetted from the oil jet. In an engine having an oil jet and a cooling channel, when the piston 26 ascends, the oil injection set speed Vo from the oil jet may fall below the piston speed Vp, and the lubricating oil does not reach the inside of the cooling channel 32. Do not contribute to The oil injection in such a case causes the oil pump to generate useless work.

  Further, as indicated by the spray angle θ, when the distance between the piston 26 and the oil jet nozzle 30 is far, a part of the oil spreads and strikes the outside of the oil inlet 31 and does not enter into the cooling channel 32. Therefore, part of the oil is repelled by the lower surface of the piston and adheres to the cylinder inner wall surface (bore surface). If the amount of oil attached to the inner wall surface of the cylinder becomes excessive, the oil is scraped up by the piston ring when the piston is elevated, enters the combustion chamber, and burns with the fuel. For this reason, oil consumption will increase.

  Therefore, in the present embodiment, the oil jet is stopped when the piston is lifted, and the oil jet is injected when the piston is lowered.

  FIG. 4 is an operation waveform diagram for describing oil injection control in the present embodiment. The piston position, the piston speed, the piston-oil relative speed, and the oil injection period are shown from top to bottom in FIG. 4.

  Assuming that the crank angle at the top dead center TDC is 0 ° and the crank angle at the bottom dead center BDC is ± 180 °, at a crank angle of −180 ° to 0 °, the piston rises and the piston speed Vp> 0. At a crank angle of 0 ° to 180 °, the piston descends, and the piston speed Vp <0.

  Here, assuming that the velocity of the oil jet is Vo, the piston-oil relative velocity is expressed by Vo-Vp. In FIG. 4, at time t1 to t2, the piston-oil relative velocity is a negative value (-V1). Therefore, even if oil is injected during this time, the piston is separated from the oil, so oil injection is not performed at time t1 to t2 (oil injection OFF) in order to suppress unnecessary work of the oil pump.

  On the other hand, in FIG. 4, at time t2 to t3, the piston-oil relative velocity is a positive value (+ V2). Therefore, if oil is injected during this time, the piston approaches the oil, so oil injection is performed from time t2 to t3 (oil injection ON).

  Thus, the piston cooling device according to the present embodiment cools the piston by the oil jet. Inside the piston 26 is provided a cooling channel 32 for cooling the piston 26 by letting oil in and out. The piston cooling device jets and jets oil from the oil jet nozzle 30 by opening and closing the oil jet nozzle 30 which jets oil toward the oil inlet 31 of the cooling channel 32 and rotating the crankshaft 27 once. And a solenoid valve 29 for controlling the stop. The closed period of the solenoid valve 29 is set to a period in which the injection set speed Vo of oil is smaller than the speed at which the piston 26 moves away from the oil jet nozzle 30 (piston speed Vp). That is, as shown in FIG. 4, the period in which Vo−Vp <0 is set as the closed period of the solenoid valve 29.

  However, it is not necessary to set all of the periods in which Vo-Vp <0 as the closing period of the solenoid valve 29. That is, if the electromagnetic valve 29 is closed even in a part of the period Vo-Vp <0, the work of the oil pump can be reduced by that amount, so improvement of fuel consumption by suppressing unnecessary work can be expected.

  Preferably, the piston cooling device of the present embodiment further includes an ECU 40. In the first crank angle range (CA1 to CA2) including the crank angle (-90.degree. In FIG. 4) corresponding to the piston position at which the speed (-Vp) at which the piston 26 moves away from the oil jet nozzle 30 is the fastest. The solenoid valve 29 is closed (oil injection is stopped) and the solenoid valve 29 is opened (oil is injected) in a second crank angle range (CA2 to CA3) not overlapping the first crank angle range. The valve 29 is controlled.

  More preferably, when the crank angle corresponding to the top dead center of the piston is 0 °, the first crank angle range (CA1 to CA2) includes at least a range of 0 to 180 °. Note that the opening / closing timing of the solenoid valve may be appropriately adjusted in consideration of the delay of the arrival time of the oil jet to the piston or the like.

  FIG. 5 is a flowchart for illustrating control of oil jets executed by the ECU in the first embodiment. The processing of this flowchart is called from the main routine of engine control and executed at fixed time intervals or whenever a predetermined condition is satisfied. First, when the process is started, the ECU 40 determines whether the crank angle CA detected by the crank angle sensor 12 satisfies CA1 <CA <CA2.

  If CA1 <CA <CA2 holds in step S1 (YES in S1), the process proceeds to step S2, and the ECU 40 transmits a control signal SV to the solenoid valve 29 so as to close the valve. Then, the process proceeds to step S5, and the control is returned to the main routine.

  On the other hand, if CA1 <CA <CA2 does not hold in step S1 (NO in S1), the process proceeds to step S3. In step S3, it is determined whether the crank angle CA detected by the crank angle sensor 12 satisfies CA2 <CA <CA3.

  If CA2 <CA <CA3 holds in step S3 (YES in S3), the process proceeds to step S4, where the ECU 40 transmits a control signal SV to the solenoid valve 29 so as to open. Then, the process proceeds to step S5, and the control is returned to the main routine.

  If CA2 <CA <CA3 is not satisfied in step S3 (NO in S3), the process proceeds to step S5, the control signal SV is not changed, and the control is returned to the main routine.

  In the above, CA1, CA2 and CA3 which are the determination values of step S1 and step S3 may be values determined in advance by experiment etc., and engine rotation speed, oil temperature, water temperature, accelerator opening degree, etc. It may be a value determined with reference to the map based on the engine operating conditions of Further, it is not necessary to make both of the determinations in step S1 and step S3. For example, when the process branches to NO in step S1, the process may be immediately advanced to step S4 without performing the determination in step S3.

  As described above, according to the piston cooling device according to the first embodiment, the period is divided into the injection period and the stop period during one rotation of the crankshaft. As a result, since the oil is injected only in the region where the piston to oil relative velocity is high, the piston can be efficiently cooled.

  In addition, since the amount of injected oil per one rotation of the crankshaft is reduced by performing the above control, the oil pump discharge work (oil pump capacity) can be reduced. By this, it is possible to reduce the friction of the engine caused by driving the oil pump, and the fuel consumption can be improved.

  Furthermore, since oil is diffused and oil injection near the piston top dead center where oil adhesion to the inner surface of the cylinder is likely to occur is stopped, excessive oil adhesion to the bore surface is reduced, and oil consumption is reduced.

Second Embodiment
In the first embodiment, unnecessary work of the oil pump is reduced by providing the injection stop period during one rotation of the crankshaft. As an example, CA2-CA3 including the crank angle 0 degree-180 degree was made into the injection period, and others were made into the stop period.

  However, in the low and medium load operating region, it may be possible to further reduce the amount of oil required to cool the piston.

  FIG. 6 is a flow chart for explaining an outline of the injection control of the oil jet performed in the second embodiment. Also in the second embodiment, the configurations of FIG. 1 and FIG. 2 are common. When the process of the flowchart of FIG. 6 is started, first, in step S11, the ECU 40 estimates a piston temperature. Subsequently, in step S12, the ECU 40 estimates the lubricant temperature.

  Then, in step S13, the spray angle θ of the oil from the oil jet nozzle 30 at the estimated lubricating oil temperature is estimated. Further, in step S14, the amount of lubricating oil necessary to cool the piston of the piston temperature estimated by the oil of the estimated lubricating oil temperature to an appropriate temperature, that is, the oil inflow into the cooling channel 32 is estimated.

  Then, in step S15, the efficient injection timing for securing the necessary amount of lubricating oil is determined. Thereafter, the process proceeds to step S16, and the control is returned to the main routine.

  FIG. 7 is a block diagram for explaining the details of processing such as estimation of the spray angle. Each block shown in FIG. 7 is a functional block diagram implemented by the ECU 40, and each may be implemented by hardware or software.

  The ECU 40 includes a fuel injection amount determination unit 42, a torque calculation unit 44, an oil temperature correction unit 48, a temperature correction unit 52, a flow rate / spray angle calculation unit 58, a cooling oil amount calculation unit 56, and a solenoid valve drive. And a signal generation unit 60. The ECU 40 further includes a storage device that stores an engine oil temperature map 46, a piston temperature map 50, a viscosity coefficient map 54, and the like.

  The fuel injection amount determination unit 42 determines a fuel injection amount from a fuel injection valve (not shown) based on the accelerator opening Acc and the engine rotation speed Ne. The torque calculation unit 44 calculates an engine torque based on the fuel injection amount and the engine rotation speed Ne.

  FIG. 8 is a diagram showing an example of an engine oil temperature map referred to in FIG. As shown in FIG. 8, in the engine oil temperature map 46, the horizontal axis represents the engine rotational speed Ne, and the vertical axis represents the engine torque Te, and the non-use areas are indicated by hatching. In the use range, the engine oil temperature is specified such that the smaller the torque and the lower the engine rotational speed, the lower the temperature, and the larger the torque and the higher the engine rotational speed, the higher the temperature. Such a map can be obtained in advance by experiment or simulation.

  FIG. 9 is a view showing an example of a piston temperature map referred to in FIG. As shown in FIG. 9, in the piston temperature map 50, the horizontal axis indicates the engine rotational speed Ne, and the vertical axis indicates the engine torque Te, and the non-use areas are indicated by hatching. In the use region, the piston temperature is specified such that the smaller the torque and the lower the engine rotational speed, the lower the temperature, and the larger the torque and the higher the engine rotational speed, the higher the temperature. Such a map can be obtained in advance by experiment or simulation.

  Referring back to FIG. 7 again, the engine oil temperature estimated by the engine oil temperature map 46 is corrected by the oil temperature correction unit 48. The oil temperature correction unit 48 corrects the oil temperature based on the water temperature Tw measured by the water temperature sensor 36. The corrected oil temperature To is performed by adding a value obtained by multiplying the water temperature Tw by the correction coefficient A with respect to the oil temperature B before correction (To = A × Tw + B).

  Instead of the correction of the water temperature, the engine oil temperature map 46 may be a three-dimensional map including the influence of the water temperature Tw.

  On the other hand, the piston temperature estimated by the piston temperature map 50 is similarly corrected by the temperature correction unit 52. The temperature correction unit 52 corrects the piston temperature based on the water temperature Tw measured by the water temperature sensor 36. The piston temperature Tp after correction is performed by adding a value obtained by multiplying the water temperature Tw by the correction coefficient C with respect to the piston temperature D before correction (Tp = C × Tw + D).

  Instead of the correction of the water temperature, the piston temperature map 50 may be a three-dimensional map including the influence of the water temperature Tw.

  The oil temperature To is used to determine the viscosity coefficient of the oil in the viscosity coefficient map 54. Then, the viscosity coefficient and the hydraulic pressure Po are given to the flow rate / spray angle calculation unit 58. First of all. The oil injection flow rate F from the oil jet nozzle 30 is given as a function f1 of the oil pressure Po and the nozzle diameter φ (F = f1 (Po, φ)). Further, the spray angle θ is given as a function f2 of the hydraulic pressure Po, the nozzle diameter φ and the viscosity coefficient k (θ = f2 (Po, φ, k)). In place of the functions f1 and f2, a map in which values experimentally obtained in advance are stored may be used. Further, in FIG. 7, the flow rate / spray angle calculation unit 58 uses the hydraulic pressure Po measured by the sensor, but the hydraulic pressure Po may be estimated and used from the engine rotation speed Ne and the engine oil temperature To.

  In parallel to the processing of the flow rate / spray angle calculation unit 58, the cooling oil amount calculation unit 56 obtains the flow rate Fcool to the cooling channel necessary to cool the piston temperature. For example, when the piston temperature Tp is higher than the oil temperature To, the larger the difference ΔT (= Tp−To), the smaller the required flow rate Fcool, and the smaller the difference, the larger the required flow rate Fcool.

  At the end of the process of FIG. 7, the solenoid valve drive signal generation unit 60 receives the flow rate F, the spray angle θ, the required flow rate Fcool and the crank angle CA, and outputs a control signal SV for opening and closing the solenoid valve 29. The relationship between the control signal SV of the solenoid valve drive signal generator 60 and the spray angle θ will be described below.

  FIG. 10 is a view for explaining the relationship between the spray angle and the amount of oil flowing into the cooling channel. FIG. 10A shows the case of the spray angle θ1, and FIG. 10B shows the case of the spray angle θ2 (> θ1). When the distance between the piston 26 and the tip of the oil jet nozzle 30 is equal, the oil jet flow is wider at the spray angle θ2 than at the spray angle θ1, and the oil density is thinner. Therefore, if the opening area of the oil inlet 31 of the cooling channel is equal, the flow rate F2 in the case of the spray angle θ2 becomes smaller than the flow rate F1 in the case of the spray angle θ1.

  FIG. 11 is a waveform diagram for describing control for changing the open period of the solenoid valve in accordance with the difference in the spray angle. Since the piston-oil relative velocity Vo-Vp> 0 is basically between the crank angle CA of 0 to 180 °, the oil flows into the cooling channel.

  However, at crank angle CA = 0, the distance between the piston and the nozzle is the largest, and at crank angle CA = 180 °, the distance between the piston and the nozzle is the closest. In consideration of the relative velocity and the distance, it is desirable to set the period T1 corresponding to the crank angles CA11 to CA12 as the valve opening period in order to efficiently obtain the flow rate Fcool necessary for the spray angle θ1.

  On the other hand, in the case of the spray angle θ2 (> θ1), the oil inflow to the cooling channel per time decreases as shown in FIG. 11 (θ = θ2). For example, the amount corresponding to the area A1 runs short. Therefore, the timing at which the solenoid valve 29 is closed is delayed to the crank angle CA13 to change it to the valve opening period T2. In this case, the flow rate flowing into the increased valve opening period corresponds to the area A2. The opening period may be extended to make the area A2 equal to the area A1.

  In the example shown in FIG. 11, the timing of opening the solenoid valve 29 is the same as in the case of the spray angle θ2, and the timing of closing is delayed. However, the present invention is not limited to this. For example, the timing at which the solenoid valve 29 is opened (corresponding to CA11 in FIG. 11) may be advanced.

  As described above, the piston cooling device according to the second embodiment further includes the ECU 40 that controls the solenoid valve 29. The ECU 40 changes the open period of the solenoid valve 29 (the injection period of the oil from the oil jet nozzle 30) in accordance with the oil flow rate Fcool required to cool the piston 26 to the target temperature or lower. The flow rate Fcool is determined based on the operating state of the engine 1 (accelerator opening degree, engine rotational speed, piston temperature determined from water temperature, etc., oil temperature, etc.), as shown in FIG.

  More preferably, as described in FIGS. 10 and 11, the ECU 40 has a wide spray angle θ indicating the spread of the injection of oil from the oil jet nozzle 30, which is determined based on the pressure Po and the temperature To of the oil. The opening period (oil injection period) of the solenoid valve 29 is set long by estimating the amount of oil flowing into the cooling channel 32 to a small extent.

  According to the second embodiment, in addition to the effect obtained in the first embodiment, by controlling the injection condition to be limited further, the piston temperature is high, and only the necessary amount of oil is used under the use condition that really requires cooling. Inject. For this reason, further reduction in fuel consumption and consumption of lubricating oil can be expected.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  1 engine, 2 cylinder heads, 4 cylinder blocks, 6 oil pans, 12 crank angle sensors, 22 and 24 water jackets, 26 pistons, 28 connecting rods, 29 solenoid valves, 30 oil jet nozzles, 31 oil inlets, 32 cooling channels, 33 oil outlet, 36 water temperature sensor, 37 oil pressure sensor, 38 oil flow path, 42 fuel injection amount determination unit, 44 torque calculation unit, 46 engine oil temperature map, 48 oil temperature correction unit, 50 piston temperature map, 52 temperature correction Part, 54 Viscosity coefficient map, 56 Cooling oil amount calculation part, 58 Spray angle calculation part, 60 Solenoid valve drive signal generation part.

Claims (5)

A piston cooling device for an internal combustion engine, wherein the piston is cooled by an oil jet,
Inside the piston, a cooling channel is provided for cooling the piston by letting lubricating oil enter and leave it,
An oil jet nozzle for injecting the lubricating oil toward the inlet of the cooling channel;
A solenoid valve for controlling the injection and stop of injection of the lubricating oil from the oil jet nozzle by opening and closing during one rotation of a crankshaft ;
And a controller for controlling the solenoid valve.
The solenoid valve is closed in a first crank angle range including a crank angle corresponding to a piston position at which the speed at which the piston moves away from the oil jet nozzle is fastest, and the second crank angle does not overlap with the first crank angle range. the-out solenoid valve is opened at a crank angle range,
The control unit sets the open period of the solenoid valve longer as the spray angle indicating the spread of the injection of the lubricating oil from the oil jet nozzle determined based on the pressure and the temperature of the lubricating oil is wider . Piston cooling system for internal combustion engines. Before SL control unit, said to correspond to the flow rate of lubricating oil required to cool the piston is determined based on the operating state of the internal combustion engine below the target temperature to change the opening period of the electromagnetic valve, A piston cooling device for an internal combustion engine according to claim 1. The control unit estimates the spray angle based on the pressure and temperature of the lubricating oil, and the spray angle is wider than the first angle when the estimated spray angle is the first angle. The piston cooling device for an internal combustion engine according to claim 2, wherein, in the case of the second angle, the open period is extended by delaying the timing of closing the solenoid valve.   The piston cooling device for an internal combustion engine according to claim 1, wherein the first crank angle range includes a range of at least 0 to 180 °, where a crank angle corresponding to a top dead center of the piston is 0 °.   An internal combustion engine comprising the piston cooling device according to any one of claims 1 to 4.

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