JP2017141779A - Piston cooling device for internal combustion engine, and internal combustion engine with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston cooling device for an internal combustion engine improved in piston cooling efficiency with respect to oil pump work.SOLUTION: A piston cooling device cools a piston with an oil jet. A cooling channel for cooling the piston by allowing oil to go in and out is provided in an inside of the piston. The piston cooling device includes an oil jet nozzle for injecting the oil toward an oil inlet of the cooling channel, and a solenoid valve for controlling injection and injection stop of the oil from the oil jet nozzle by being opened and closed during one rotation of a crankshaft. In a closed period of the solenoid valve (oil injection stop period t1-t2), an injection set speed (Vo) of the oil is lower than a speed (Vp) at which the piston is separated from the oil jet nozzle.SELECTED DRAWING: Figure 4

Description

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

  The heat of the piston of the engine is radiated to the cooling water of the water jacket through the cylinder. In recent years, an engine is required to have a high output while keeping its physique small, and since it generates a large amount of heat, it needs to dissipate heat.

  For this reason, an oil jet that cools a recent engine by injecting lubricating oil onto the back side of the piston is employed. Especially in turbocharged engines where the temperature of the piston tends to rise, and direct in-cylinder injection engines where a cavity with high heat load is formed, an annular cavity called cooling channel is formed in the piston, and the oil 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 in which such a cooling channel (also called an oil gallery) is formed by an oil jet.

  Generally, oil jet lubricating oil is supplied from an oil pump. The oil pressure from the oil pump increases as the engine speed increases. When this hydraulic pressure exceeds the pressure of a check valve provided in the lubricating oil supply path of the oil jet, oil is injected and the piston is cooled. On the other hand, in the engine disclosed in Japanese Patent Laid-Open No. 10-68319, oil is injected from the oil jet in the high speed and high load region, and oil injection from the oil jet is stopped in the low, medium and low load regions. To suppress overcooling.

JP-A-10-68319

  Lubricating oil injected from the oil jet is filled into the cooling channel from the inlet of the cooling channel. Lubricating oil in the cooling channel is stirred by the upper and lower sides of the piston, takes heat of the piston by heat exchange, and is discharged from the oil discharge port. In order to perform exhaust heat by such good heat exchange, the filling rate of the cooling channel with the lubricating oil is desirably 50% or more on average.

  For this reason, in the engine disclosed in JP-A-10-68319, oil is always injected from an oil jet in a high-speed and high-load region. However, when the piston rises while the engine is rotating, the oil injection speed from the oil jet may be lower than the piston speed, and the lubricating oil does not reach the inside of the cooling channel and does not contribute to piston cooling.

  Therefore, the oil injection from the oil jet when the piston is raised causes useless work of the oil pump. Further, a part of the lubricating oil that does not enter the cooling channel adheres to the cylinder inner wall surface (bore surface). If the amount of the lubricating oil adhering to the cylinder inner wall surface becomes excessive, the piston ring is scraped up by the piston ring and burned together with the fuel when the piston is raised, so that the amount of consumption of the lubricating oil increases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to improve the piston cooling efficiency with respect to oil pump work, and an internal combustion engine including the same. Is to provide.

  The present invention relates to a piston cooling device for an internal combustion engine that cools a piston by an oil jet. A cooling channel for cooling the piston by allowing the lubricating oil to enter and exit is provided inside the piston. The piston cooling device controls the injection and stoppage of the lubricating oil from the oil jet nozzle by opening and closing the oil jet nozzle that injects the lubricating oil toward the inlet of the cooling channel and the crankshaft rotating once. And a solenoid valve. The solenoid valve closes in a first crank angle range including a crank angle corresponding to the piston position at which the piston moves away from the oil jet nozzle at the fastest speed, and does not overlap with the first crank angle range. Open at.

  Preferably, a control unit for controlling the electromagnetic valve is further provided. The control unit changes the opening period of the electromagnetic valve in accordance with the flow rate of the lubricating oil necessary for cooling the piston determined based on the operating state of the internal combustion engine to a target temperature or less.

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

  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 °.

  In another aspect, the present invention is an internal combustion engine including the piston cooling device according to any one of the above.

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

It is a figure which shows schematic structure of the engine 1 provided with the cooling device which concerns on Embodiment 1. FIG. It is the figure which expanded and showed the detail of the piston and the oil jet nozzle. It is a figure which shows the spray angle (theta) of the oil injected from an oil jet nozzle. It is an operation | movement waveform diagram for demonstrating the oil injection control in this Embodiment. 4 is a flowchart for illustrating control of an oil jet executed by an ECU in the first embodiment. 6 is a flowchart for explaining an outline of oil jet injection control executed in a second embodiment. 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 amount to a cooling channel. It is a wave form diagram for demonstrating the control which changes the valve opening period of a solenoid valve according to the difference in 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 parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a diagram illustrating a schematic configuration of an engine 1 including the cooling device according to the first embodiment. The engine 1 may include a plurality of cylinders. FIG. 1 schematically shows a cross section of one cylinder.

  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 shown, each cylinder has 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 Exhaust valves and the like for opening and closing are provided.

  A piston 26 is accommodated in the cylinder, and the piston 26 can reciprocate up and down. The piston 26 is connected to a 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, and the engine rotation speed Ne is obtained by measuring the crank angle with the crank angle sensor 12.

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

  The cylinder block 4 is formed with an oil passage 38 for supplying oil to the electromagnetic valve 29. A hydraulic pressure sensor 37 is disposed in the oil flow path 38, and the hydraulic pressure Po is measured.

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

  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 a crank angle sensor 12. ECU 40 further receives water temperature Tw and hydraulic pressure Po from water temperature sensor 36 and hydraulic pressure sensor 37, respectively. Based on these received signals, the ECU 40 controls the electromagnetic valve 29.

  FIG. 2 is an enlarged view showing details of the piston and the oil jet. With reference to FIGS. 1 and 2, a cooling channel 32 into which oil injected from an oil jet nozzle 30 is introduced is formed in the piston 26. The oil jet injects oil toward the oil inlet 31 of the cooling channel 32 on the back surface of the piston 26. FIG. 2 shows a state where the piston 26 is located at the bottom dead center and the tip of the oil jet nozzle 30 is closest to the oil inlet 31.

  By introducing the oil into the cooling channel 32, the piston 26 is efficiently cooled. 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 diagram showing the spray angle θ of oil injected from the oil jet. In an engine having an oil jet and a cooling channel, when the piston 26 is raised, the oil injection set speed Vo from the oil jet may be lower than the piston speed Vp, and the lubricating oil does not reach the inside of the cooling channel 32, and the piston is cooled. Does not contribute to The oil injection in such a case generates useless work for the oil pump.

  Further, as shown 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 hits the outside of the oil inlet 31 and does not enter the cooling channel 32. Accordingly, 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 adhering to the inner wall surface of the cylinder becomes excessive, the oil is scraped up by the piston ring when the piston is raised, enters the combustion chamber, and burns with the fuel. For this reason, the consumption of oil will increase.

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

  FIG. 4 is an operation waveform diagram for explaining oil injection control in the present embodiment. FIG. 4 shows the piston position, piston speed, piston-oil relative speed, and oil injection period in order from the top.

  When the crank angle at the top dead center TDC is 0 ° and the crank angle at the bottom dead center BDC is ± 180 °, the piston rises at a crank angle of −180 ° to 0 °, 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 speed of the oil jet is Vo, the piston-oil relative speed is expressed as Vo-Vp. In FIG. 4, the piston-oil relative speed is a negative value (−V1) at times t1 to t2. Therefore, even if oil is injected during this time, the piston is separated from the oil, so that oil injection is not performed at time t1 to t2 (oil injection OFF) in order to suppress useless work of the oil pump.

  On the other hand, in FIG. 4, at time t2 to t3, the piston-oil relative speed is a positive value (+ V2). Accordingly, if oil is injected during this time, the piston approaches the oil, and therefore oil injection is performed at 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 allowing oil to enter and exit. The piston cooling device is configured to inject and inject oil from the oil jet nozzle 30 by opening and closing the oil jet nozzle 30 that injects oil toward the oil inlet 31 of the cooling channel 32 and the crankshaft 27 making one rotation. And an electromagnetic valve 29 for controlling the stop. The closing period of the solenoid valve 29 is set to a period in which the oil injection set speed Vo 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 closing period of the electromagnetic valve 29.

  However, it is not necessary that the entire period where Vo−Vp <0 be the closing period of the solenoid valve 29. That is, if the solenoid valve 29 is closed even during a part of the period when Vo−Vp <0, the work of the oil pump can be reduced correspondingly, so that an improvement in fuel consumption by suppressing useless 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 ° 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 electromagnetic valve 29 is closed (oil injection is stopped) and the electromagnetic valve 29 is opened (oil is injected) in the second crank angle range (CA2 to CA3) that does not overlap with 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 a range of at least 0 to 180 °. Note that the opening / closing timing of the solenoid valve may be appropriately adjusted in consideration of delays such as the arrival time of the oil jet to the piston.

  FIG. 5 is a flowchart for illustrating oil jet control executed by the ECU according to the first embodiment. The process of this flowchart is called from the main routine of engine control and executed every predetermined time or every time a predetermined condition is satisfied. First, when the process is started, the ECU 40 determines whether or not the crank angle CA detected by the crank angle sensor 12 satisfies CA1 <CA <CA2.

  When CA1 <CA <CA2 is established in step S1 (YES in S1), the process proceeds to step S2, and the ECU 40 transmits a control signal SV to the electromagnetic 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 is not satisfied in step S1 (NO in S1), the process proceeds to step S3. In step S3, it is determined whether or not the crank angle CA detected by the crank angle sensor 12 satisfies CA2 <CA <CA3.

  When CA2 <CA <CA3 is established in step S3 (YES in S3), the process proceeds to step S4, and the ECU 40 transmits a control signal SV to the electromagnetic valve 29 so as to open the valve. 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, and control is returned to the main routine without changing the control signal SV.

  In the above, CA1, CA2, and CA3, which are the determination values in steps S1 and S3, may be values determined in advance through experiments or the like, and may include engine rotation speed, oil temperature, water temperature, accelerator opening, and the like. The value may be determined by referring to a map based on the engine operating conditions. Further, it is not always necessary to perform both the determinations of step S1 and step S3. For example, when branching 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 apparatus according to the first embodiment, the period is divided into the injection period and the stop period during one rotation of the crankshaft. Thereby, since oil is injected only in the region where the piston-oil relative speed is high, the piston can be efficiently cooled.

  Further, since the amount of injected oil per one rotation of the crankshaft is reduced by performing the above control, it is possible to reduce the oil pump discharge work (oil pump capacity). As a result, it is possible to reduce engine friction caused by driving the oil pump and improve fuel efficiency.

  Further, since the oil injection is stopped near the top dead center of the piston where the oil diffuses and the oil is likely to adhere to the inner wall surface of the cylinder, excessive oil adhesion to the bore surface is reduced and the oil consumption is reduced.

[Embodiment 2]
In the first embodiment, wasteful work of the oil pump is reduced by providing an injection stop period during one rotation of the crankshaft. As an example, CA2 to CA3 including a crank angle of 0 ° to 180 ° are set as the injection period, and the others are set as the stop period.

  However, in the middle and low load operation region, the amount of oil required for cooling the piston may be further reduced.

  FIG. 6 is a flowchart for explaining the outline of the oil jet injection control executed in the second embodiment. In the second embodiment, the configurations of FIGS. 1 and 2 are also common. When the processing of the flowchart of FIG. 6 is started, first, in step S11, the ECU 40 estimates the piston temperature. Subsequently, in step S12, the ECU 40 estimates the lubricating oil temperature.

  In step S13, the spray angle θ of 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 for cooling the piston having the estimated piston temperature to the appropriate temperature with the oil having the estimated lubricating oil temperature, that is, the amount of oil flowing into the cooling channel 32 is estimated.

  In step S15, an 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 details of processing such as estimation of the spray angle. Each block shown in FIG. 7 is a functional block diagram realized by the ECU 40, and each block can be realized 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. A signal generator 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 speed Ne. The torque calculation unit 44 calculates 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 indicates the engine rotational speed Ne, the vertical axis indicates the engine torque Te, and the unused area is indicated by shading. In the use region, the engine oil temperature is regulated such that the lower the torque and the lower the engine speed, the lower the temperature, and the higher the torque and the higher the engine speed, the higher the temperature. Such a map can be obtained in advance by experiments or simulations.

  FIG. 9 is a diagram 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 rotation speed Ne, the vertical axis indicates the engine torque Te, and the unused area is indicated by shading. In the use region, the piston temperature is regulated such that the lower the torque and the lower the engine speed, the lower the temperature, and the higher the torque and the higher the engine speed, the higher the temperature. Such a map can be obtained in advance by experiments or simulations.

  Returning 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 to the oil temperature B before correction (To = A × Tw + B).

  Instead of correcting 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 corrected piston temperature Tp is obtained by adding a value obtained by multiplying the piston temperature D before correction by a correction coefficient C to the water temperature Tw (Tp = C × Tw + D).

  Instead of correcting 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 oil viscosity coefficient 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. The oil injection flow rate F from the oil jet nozzle 30 is given as a function f1 of the hydraulic pressure Po and the nozzle diameter φ (F = f1 (Po, φ)). 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. In FIG. 7, the flow rate / spray angle calculation unit 58 uses the hydraulic pressure Po measured by the sensor. However, the hydraulic pressure Po may be estimated from the engine rotational speed Ne and the engine oil temperature To.

  In parallel with the processing of the flow rate / spray angle calculation unit 58, the cooling oil amount calculation unit 56 determines the flow rate Fcool to the cooling channel necessary for cooling 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 greater the required flow rate Fcool.

  At the end of the process in FIG. 7, the electromagnetic valve drive signal generator 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 electromagnetic valve 29. Hereinafter, the relationship between the control signal SV of the electromagnetic valve drive signal generator 60 and the spray angle θ will be described.

  FIG. 10 is a diagram 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 the same, the oil jet flow is wider at the spray angle θ2 than at the spray angle θ1, and the oil density is low. Therefore, if the opening area of the oil inlet 31 of the cooling channel is equal, the flow rate F2 at the spray angle θ2 is smaller than the flow rate F1 at the spray angle θ1.

  FIG. 11 is a waveform diagram for explaining the control for changing the valve opening period of the electromagnetic valve in accordance with the difference in the spray angle. When the crank angle CA is between 0 and 180 °, the piston-oil relative speed Vo-Vp> 0 is basically satisfied, so that the oil flows into the cooling channel.

  However, the distance between the piston and the nozzle is the farthest at the crank angle CA = 0, and the distance between the piston and the nozzle is the closest at the crank angle CA = 180 °. Considering the relative speed and 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 amount of oil flowing into the cooling channel per hour decreases as shown in FIG. 11 (θ = θ2). In this case, the amount corresponding to the area A1 is insufficient. Therefore, the timing for closing the electromagnetic valve 29 is delayed to the crank angle CA13 and changed 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 valve opening period may be extended so that the area A2 is equal to the area A1.

  In the example of FIG. 11, an example in which the timing of opening the electromagnetic valve 29 is the same and the closing timing is delayed in the case of the spray angle θ <b> 2 is shown, but the present invention is not limited to this. For example, the timing for opening the electromagnetic valve 29 (corresponding to CA11 in FIG. 11) may be advanced.

  As described above, the piston cooling apparatus according to the second embodiment further includes the ECU 40 that controls the electromagnetic valve 29. The ECU 40 changes the opening period of the electromagnetic valve 29 (the period of oil injection from the oil jet nozzle 30) in accordance with the oil flow rate Fcool required to cool the piston 26 below the target temperature. As shown in FIG. 7, the flow rate Fcool is determined based on the operating state of the engine 1 (piston temperature, oil temperature, etc. determined from the accelerator opening, engine rotation speed, water temperature, etc.).

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

  According to the second embodiment, in addition to the effects obtained in the first embodiment, by further restricting the injection conditions, control is performed so that only a necessary amount of oil is supplied under a use condition where the piston temperature is high and cooling is really necessary. Spray. For this reason, further reduction in fuel consumption and reduction in consumption of lubricating oil can be expected.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Engine, 2 Cylinder head, 4 Cylinder block, 6 Oil pan, 12 Crank angle sensor, 22, 24 Water jacket, 26 Piston, 28 Connecting rod, 29 Solenoid valve, 30 Oil jet nozzle, 31 Oil inlet, 32 Cooling channel, 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 Unit, 54 viscosity coefficient map, 56 cooling oil amount calculation unit, 58 spray angle calculation unit, 60 solenoid valve drive signal generation unit.

Claims (5)

A piston cooling device for an internal combustion engine that cools a piston by an oil jet,
Inside the piston is provided with a cooling channel for cooling the piston by allowing lubricant to enter and exit,
An oil jet nozzle that injects the lubricating oil toward an inlet of the cooling channel;
An electromagnetic valve that controls injection and stop of injection of the lubricating oil from the oil jet nozzle by opening and closing during one rotation of the crankshaft,
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 the fastest, and the second does not overlap with the first crank angle range. A piston cooling device for an internal combustion engine, wherein the solenoid valve opens in a crank angle range. A control unit for controlling the solenoid valve;
The control unit changes an open period of the electromagnetic valve in accordance with a flow rate of lubricating oil necessary for cooling the piston, which is determined based on an operating state of the internal combustion engine, to a target temperature or less. Item 2. A piston cooling device for an internal combustion engine according to Item 1.   The control unit sets the open period of the solenoid valve longer as the spray angle indicating the spread of the injection of the lubricant from the oil jet nozzle determined based on the pressure and temperature of the lubricant is wider. The piston cooling device for an internal combustion engine according to claim 2.   2. 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 ° when 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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