WO2022065126A1

WO2022065126A1 - Abutment gap estimation device, abutment gap control device, abutment gap estimation method, and abutment gap control method

Info

Publication number: WO2022065126A1
Application number: PCT/JP2021/033666
Authority: WO
Inventors: 拓朗三田
Original assignee: いすゞ自動車株式会社
Priority date: 2020-09-24
Filing date: 2021-09-14
Publication date: 2022-03-31
Also published as: JP2022053303A

Abstract

This abutment gap estimation device comprises: a part temperature estimation unit that estimates the temperature of a part other than a ring groove in a piston constituting an internal combustion engine; a ring groove temperature estimation unit that estimates the temperature of the ring groove on the basis of the temperature of the part estimated by the part temperature estimation unit; a piston ring temperature estimation unit that estimates the temperature of a piston ring on the basis of the temperature of the ring groove estimated by the ring groove temperature estimation unit; and a gap estimation unit that estimates the size of an abutment gap of the piston ring on the basis of the temperature of the piston ring estimated by the piston ring temperature estimation unit.

Description

Abutment gap estimation device, abutment gap control device, abutment gap estimation method and abutment gap control method

The present disclosure relates to a joint gap estimation device, a joint gap control device, a joint gap estimation method, and a joint gap control method.

Conventionally, a method of adjusting the size of the joint of a piston ring provided on a piston of an internal combustion engine is known (see, for example, Patent Documents 1 and 2).

In the method described in Patent Document 1, the size of the joint of the piston ring is estimated based on the engine cooling water temperature and the fuel injection amount history.

In the method described in Patent Document 2, the size of the joint of the piston ring is estimated based on the amount of blow-by gas.

Japanese Patent Application Laid-Open No. 2019-127840 Japanese Patent Application Laid-Open No. 2010-285944

However, with the methods described in

Patent Documents

1 and 2, there is a possibility that the size of the joint of the piston ring is not properly estimated.

An object of the present disclosure is to provide a joint gap estimation device, a joint gap control device, a joint gap estimation method, and a joint gap control method that can appropriately estimate the size of a joint of a piston ring.

The joint gap estimation device according to the present disclosure includes a temperature estimation unit for other parts that estimates the temperature of other parts other than the ring groove in the piston constituting the internal combustion engine, and the temperature of the other part estimated by the temperature estimation unit for other parts. Based on the ring groove temperature estimation unit that estimates the temperature of the ring groove and the temperature of the ring groove estimated by the ring groove temperature estimation unit, the temperature of the piston ring mounted on the ring groove is set. It includes a piston ring temperature estimation unit for estimating, and a gap estimation unit for estimating the size of the gap at the abutment of the piston ring based on the temperature of the piston ring estimated by the piston ring temperature estimation unit.

The abutment gap control device according to the present disclosure controls the size of the abutment gap based on the abutment gap estimation device described above and the size of the abutment gap of the piston ring estimated by the abutment gap estimation device. A gap control unit is provided.

The method for estimating the gap between the joints according to the present disclosure is a step of estimating the temperature of a portion other than the ring groove in the piston constituting the internal combustion engine, and the ring groove in the piston based on the estimated temperature of the other portion. Based on the step of estimating the temperature, the step of estimating the temperature of the piston ring mounted on the ring groove based on the estimated temperature of the ring groove, and the step of estimating the temperature of the estimated piston ring. The step of estimating the size of the gap at the joint of the piston ring is performed.

The abutment gap control method according to the present disclosure is based on the step of executing the above-mentioned abutment gap estimation method and the size of the abutment gap of the piston ring estimated by the execution of the abutment gap estimation method. Perform steps to control the size of the gap.

According to the present disclosure, it is possible to provide a joint gap estimation device, a joint gap control device, a joint gap estimation method, and a joint gap control method that can appropriately estimate the size of the joint of a piston ring.

Sectional drawing which shows the schematic structure of the engine which concerns on one Embodiment of this disclosure. Top view showing the structure of the piston ring which concerns on one Embodiment of this disclosure. A block diagram showing a configuration of a joint gap control device according to an embodiment of the present disclosure. A graph showing the relationship between the temperature of the mouth portion and the temperature of the ring groove in the state where the cooling oil is injected and the state where the cooling oil is not injected according to the embodiment of the present disclosure. A flowchart showing an example of the operation of the joint gap control device according to the embodiment of the present disclosure. A flowchart showing an example of the operation of the joint gap control device according to the embodiment of the present disclosure. A flowchart showing an example of the operation of the joint gap control device according to the embodiment of the present disclosure.

[Embodiment]
Hereinafter, an embodiment of the present disclosure will be described.

[Outline configuration of engine]
First, a schematic configuration of an engine controlled by the joint gap control device of the present disclosure will be described. The engine is an example of an internal combustion engine. FIG. 1 is a cross-sectional view showing a schematic configuration of an engine.

The engine 10 shown in FIG. 1 is a diesel engine mounted on an automobile such as a truck. The engine 10 includes a cylinder 20 and a piston 40. The internal combustion engine of the present disclosure is not limited to a diesel engine, and may be a gasoline engine or the like.

The cylinder 20 is provided with a cooling passage 21. The cooling water of the cylinder 20 is supplied to the cooling passage 21. A liner 22 is provided on the inner peripheral surface of the cylinder 20. The liner 22 may not be provided. An injector 24 is provided on the cylinder head 23 above the cylinder 20 so as to face the center of the top surface of the piston 40. The cylinder head 23 is provided with an intake port 25 and an exhaust port 26 so as to be located on the left and right sides of the injector 24. The intake port 25 and the exhaust port 26 are provided with an intake valve 27 and an exhaust valve 28, respectively.

The piston 40 is installed so as to be able to reciprocate in the cylinder 20 along the liner 22. The piston 40 is made of, for example, an aluminum alloy.

A cavity 42 is provided on the top surface of the piston upper portion 41 of the piston 40. The piston upper portion 41 has a cooling channel 44 formed along the circumferential direction, an introduction hole 45 for introducing oil into the cooling channel 44, and a discharge hole 46 for discharging oil from the cooling channel 44. It is provided. Oil is introduced into the cooling channel 44 from the oil jet 61 through the introduction hole 45. The introduced oil circulates in the cooling channel 44 and is discharged from the discharge hole 46, so that the piston 40 is efficiently cooled. The oil injected from the oil jet 61 may be referred to as "cooling oil". A ring groove 47 formed along the circumferential direction is provided on the outer periphery of the piston upper portion 41 of the piston 40. A piston ring 48 that is in sliding contact with the liner 22 is mounted on the ring groove 47.

As shown by the solid line in FIG. 2, the piston ring 48 includes a first joint surface 48A and a second joint surface 48B. When the piston ring 48 is heated by the combustion of the engine 10 shown by the chain double-dashed line in FIG. 2 (heat state), the piston ring 48 has a standard temperature (for example, 25 ° C., which is room temperature) (cold) shown by the solid line in FIG. It expands and becomes larger than the state of (between). Due to this expansion, the gap C between the first joint surface 48A and the second joint surface 48B during hot weather (hereinafter, may be referred to as “joint gap C”) is smaller than the gap C during cold weather. Become.

If the joint gap C during hot weather is too large, the flow rate of blow-by gas will be too large. When the abutment gap C in the hot state becomes 0 and the first abutment surface 48A and the second abutment surface 48B come into contact with each other, the tension acting on the piston ring 48 changes, and the piston ring 48 and the piston ring 48 The sliding resistance between the cylinder 20 and the cylinder 20 increases, and the cylinder 20 and the piston ring 48 may be worn or the sliding surface of the cylinder 20 and the piston ring 48 may be seized. Therefore, the size of the joint opening gap C of the piston ring 48 when it is cold is set to a size so that the above-mentioned problems do not occur when it is hot.

A clearance P is provided between the skirt portion 49 of the piston 40 and the cylinder 20. By supplying an appropriate amount of oil to the clearance P, the lubrication state between the skirt portion 49 and the cylinder 20 is properly maintained. The skirt portion 49 of the piston 40 is provided with a pair of pin boss portions 50 facing each other (only one pin boss portion 50 is shown in FIG. 1). The pair of pin boss portions 50 are each provided with pin fitting holes 51 penetrating from the center side of the piston 40 toward the outer peripheral side of the piston. The upper end of the connecting rod 53 is connected to the pin fitting hole 51 via the piston pin 52. The lower end of the connecting rod 53 is connected to the crankshaft 55 via the crankpin 54. The crankshaft 55 converts the reciprocating motion of the piston 40 into a rotary motion.

The oil jet 61 includes a supply valve 62 and a nozzle 63. When the supply valve 62 is “closed”, the cooling oil is not injected from the nozzle 63. When the supply valve 62 is “open”, cooling oil is injected from the nozzle 63. Since the configuration of the oil jet 61 is known, detailed description thereof will be omitted.

An oil passage 65 is provided between the oil jet 61 and an oil pan (not shown). The oil passage 65 is provided with a variable oil pump 64 capable of changing the flow rate of oil. The portion of the oil passage 65 on the oil jet 61 side of the variable oil pump 64 is connected to a supply passage (not shown) that supplies oil to a portion of the engine 10 that requires lubrication. The variable oil pump 64 supplies the oil (lubricating oil) stored in the oil pan to a portion requiring lubrication, an oil jet 61, or the like.

[Structure of abutment gap control device]
Next, the configuration of the joint gap control device will be described. FIG. 3 is a block diagram showing a configuration of a joint gap control device. FIG. 4 is a graph showing the relationship between the temperature of the mouth portion and the temperature of the ring groove in the state where the cooling oil is injected and the state where the cooling oil is not injected.

As shown in FIG. 3, the abutment gap control device 100 includes an abutment gap estimation device 110, a storage unit 120, and a gap control unit 130. The gap estimation device 110 and the gap control unit 130 have, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like as hardware. Each function of the joint gap estimation device 110 and the gap control unit 130 described below is realized by executing a computer program read from the ROM by the CPU on the RAM.

The joint gap estimation device 110 includes an acquisition unit 111, a mouth temperature estimation unit 112, a determination unit 113, a ring groove temperature estimation unit 114, a cylinder temperature estimation unit 115, a piston ring temperature estimation unit 116, and a gap estimation unit. 117 and.

The acquisition unit 111 acquires engine status information representing the engine status from various sensors.

The mouth temperature estimation unit 112 estimates the temperature of the mouth portion 43 of the cavity 42 of the piston 40. The mouth portion 43 is a portion of the piston 40 where the temperature is highest. Hereinafter, the temperature of the mouth portion 43 estimated by the mouth temperature estimation unit 112 may be referred to as “estimated mouth portion temperature”. The mouth temperature estimation unit 112 is an example of another unit temperature estimation unit, and the mouth unit 43 is an example of another unit.

The determination unit 113 determines whether or not the oil jet 61 injects cooling oil toward the piston 40.

The ring groove temperature estimation unit 114 estimates the temperature of the ring groove 47 in the piston 40 based on the temperature estimation information stored in the storage unit 120 and the estimated mouth temperature estimated by the mouth temperature estimation unit 112. do. Hereinafter, the temperature of the ring groove 47 estimated by the ring groove temperature estimation unit 114 may be referred to as an “estimated ring groove temperature”.

The cylinder temperature estimation unit 115 estimates the temperature of the cylinder 20. Hereinafter, the temperature of the cylinder 20 estimated by the cylinder temperature estimation unit 115 may be referred to as an “estimated cylinder temperature”.

The piston ring temperature estimation unit 116 estimates the temperature of the piston ring 48 based on the estimated ring groove temperature obtained by the processing of the ring groove temperature estimation unit 114 and the estimated cylinder temperature estimated by the cylinder temperature estimation unit 115. do. Hereinafter, the temperature of the piston ring 48 estimated by the piston ring temperature estimation unit 116 may be referred to as an “estimated ring temperature”. The piston ring temperature estimation unit 116 selects a predetermined time constant from a plurality of time constants stored in the storage unit 120, and corrects the estimated ring temperature using the selected time constant. Hereinafter, the temperature of the piston ring 48 corrected by using the time constant may be referred to as “corrected ring temperature”.

The gap estimation unit 117 estimates the size of the abutment gap C based on the estimated cylinder temperature and the correction ring temperature.

The storage unit 120 stores the mouth temperature estimation map. The mouth temperature estimation map is a map showing the relationship between the rotation speed of the crankshaft 55, the fuel injection amount, and the estimated temperature of the mouth portion 43. The mouth temperature estimation map is used for estimating the estimated mouth temperature in the mouth temperature estimation unit 112.

The storage unit 120 stores the first estimation formula represented by the following formula (1) and the second estimation formula represented by the formula (2). The first estimation formula is an example of the first estimation information, and the second estimation formula is an example of the second estimation information. The temperature estimation information is composed of the first estimation formula and the second estimation formula. The first estimation formula and the second estimation formula are used for estimating the estimated ring groove temperature in the ring groove temperature estimation unit 114. The first estimation formula and the second estimation formula are not limited to the formulas (1) and (2). Further, the first estimation information and the second estimation information may be in a map format such as a mouth temperature estimation map.
T _ON = α _ON × _TK + β _ON・・・ (1)
T _OFF = α _OFF × _TK + β _OFF・・・ (2)
T _ON : Estimated ring groove temperature when cooling oil is injected α _ON, β _ON : Coefficient when cooling oil is injected _TK : Estimated mouth temperature T _OFF : Cooling oil is injected Estimated ring groove temperature when not in place α _OFF, β _OFF : Coefficient when cooling oil is not injected

The first estimation formula and the second estimation formula are obtained, for example, as follows. The relationship between the temperature of the mouth portion 43 and the temperature of the ring groove 47 in the state where the cooling oil is injected and the state where the cooling oil is not injected is obtained. When a graph is created in which the horizontal axis is the temperature of the mouth portion 43 and the vertical axis is the temperature of the ring groove 47, as shown in FIG. 4, the temperature of the mouth portion 43 is set regardless of whether or not the cooling oil is injected. It can be seen that there is a linear relationship between the temperature and the temperature of the ring groove 47. The first-order approximation formula of the data when the cooling oil is injected is obtained as the first estimation formula, and the first-order approximation formula of the data when the cooling oil is not injected is obtained as the second estimation formula. When the temperature of the mouth portion 43 is the same, the temperature of the ring groove 47 when the cooling oil is injected is lower than the temperature of the ring groove 47 when the cooling oil is not injected. Therefore, the coefficient α _ON of the first estimation formula is smaller than the coefficient α _OFF of the second estimation formula. The temperature of the mouth portion 43 and the temperature of the ring groove 47 used for creating the first estimation formula and the second estimation formula may be values obtained by simulation or may be measured values.

The storage unit 120 has a first time constant, a second time constant, a third time constant, a fourth time constant, a fifth time constant, a sixth time constant, a seventh time constant, and an eighth time constant. Memorize the time constant. The first to eighth time constants indicate the degree of change rate of the temperature of the piston ring 48. The first to eighth time constants are used to calculate the corrected ring temperature in the piston ring temperature estimation unit 116.

The first to fourth time constants are selected when the cooling oil is not injected into the piston 40.

The first time constant is selected when the estimated ring temperature has dropped, fuel injection has not been performed, and the engine 10 has stopped. The second time constant is selected when the estimated ring temperature has dropped, fuel injection has not been performed, and the engine 10 is running.

When the estimated ring temperature is lowered, fuel injection is not performed, and the engine 10 is operating, the cooling oil and the cooling water circulate in the engine 10, so that the temperature of the piston ring 48 is lowered. The speed will be faster.

On the other hand, when the estimated ring temperature drops, fuel injection is not performed, and the engine 10 is stopped, the circulation of cooling oil and cooling water is stopped. Therefore, the rate of decrease in the temperature of the piston ring 48 becomes slow. Therefore, the value of the first time constant is larger than the value of the second time constant.

The third time constant is selected when the estimated ring temperature has dropped and fuel injection is taking place. When fuel injection is performed, since the engine 10 burns fuel, the temperature of the piston 40 changes significantly with respect to the change in the fuel injection amount, and the rate of decrease in the temperature of the piston ring 48 is the fuel injection. Is equal to or faster than if was not done. Therefore, the value of the third time constant is smaller than the value of the first time constant, and is equal to or smaller than the value of the second time constant.

The fourth time constant is selected when the estimated ring temperature is rising. The value of the fourth time constant is larger than the value of the third time constant.

The fifth to eighth time constants are selected in a state where the cooling oil is injected into the piston 40.

The fifth time constant is selected when the estimated ring temperature has dropped, fuel injection has not been performed, and the engine 10 has stopped. When the cooling oil is injected into the piston 40, the temperature of the piston ring 48 drops faster than when the cooling oil is not injected into the piston 40. Therefore, the value of the fifth time constant is smaller than the value of the first time constant.

The sixth time constant is selected when the estimated ring temperature has dropped, fuel injection has not been performed, and the engine 10 is running. When the cooling oil is injected into the piston 40, the temperature of the piston ring 48 drops faster than when the cooling oil is not injected into the piston 40. Therefore, the value of the sixth time constant is smaller than the value of the second time constant.

The seventh time constant is selected when the estimated ring temperature has dropped and fuel injection is taking place. When the cooling oil is injected into the piston 40, the temperature of the piston ring 48 drops faster than when the cooling oil is not injected into the piston 40. Therefore, the value of the seventh time constant is smaller than the value of the third time constant.

The eighth time constant is selected when the estimated ring temperature is rising. When the cooling oil is injected into the piston 40, the temperature rise rate of the piston ring 48 is faster than that in the case where the cooling oil is not injected into the piston 40. Therefore, the value of the eighth time constant is smaller than the value of the fourth time constant.

Hereinafter, detailed configurations of the acquisition unit 111, the mouth temperature estimation unit 112, the determination unit 113, the ring groove temperature estimation unit 114, the cylinder temperature estimation unit 115, the piston ring temperature estimation unit 116, the gap estimation unit 117, and the gap control unit 130 will be described. explain.

(Acquisition unit 111)
The acquisition unit 111 provides engine state information such as the rotation speed of the crank shaft 55 of the engine 10, the fuel injection amount to the combustion chamber 11 surrounded by the piston 40 of the engine 10, the cylinder 20 and the cylinder head 23, the fuel injection timing, and the fuel. Injection pressure, presence / absence of injection of cooling oil to piston 40, oil pressure of cooling oil, oil temperature of cooling oil, intake air temperature, intake pressure, intake air amount, intake air temperature, cooling water temperature of cylinder 20, exhaust Acquires the operation signal of the brake, the exhaust temperature, the EGR (Exhaust Gas Recirculation) gas flow rate, and the like.

(Mouth temperature estimation unit 112)
The mouth temperature estimation unit 112 of the mouth portion 43 of the piston 40 is based on the rotation speed and fuel injection amount of the crankshaft 55 acquired by the acquisition unit 111 and the mouth temperature estimation map stored in the storage unit 120. Estimate the temperature. The mouth temperature estimation unit 112 corrects the temperature estimated based on the mouth temperature estimation map or the like using the information such as the fuel injection timing acquired by the acquisition unit 111, and estimates the corrected value as the estimated mouth temperature. do.

(Determining unit 113)
The determination unit 113 determines whether or not the cooling oil is injected toward the piston 40 based on the engine state information acquired by the acquisition unit 111.

(Ring groove temperature estimation unit 114)
When the determination unit 113 determines that the cooling oil has been injected, the ring groove temperature estimation unit 114 uses the mouth temperature estimation unit to the first estimation formula (formula (1)) stored in the storage unit 120. The estimated ring groove temperature is obtained by substituting the estimated mouth temperature estimated in 112. When the determination unit 113 determines that the cooling oil has not been injected, the ring groove temperature estimation unit 114 uses the mouth temperature estimation unit to the second estimation formula (formula (2)) stored in the storage unit 120. The estimated ring groove temperature is obtained by substituting the estimated mouth temperature estimated in 112.

(Cylinder temperature estimation unit 115)
The cylinder temperature estimation unit 115 estimates the estimated cylinder temperature based on the temperature of the cooling water of the cylinder 20 acquired by the acquisition unit 111. The cylinder temperature estimation unit 115 may estimate the estimated cylinder temperature based on the measurement result of the sensor that measures the temperature of the cylinder 20 or the liner 22. Further, the cylinder temperature estimation unit 115 may correct the estimated cylinder temperature by using the estimated ring groove temperature, or may correct the estimated cylinder temperature by using a value representing the heat supply amount of the piston 40 such as the fuel injection amount.

(Piston ring temperature estimation unit 116)
The piston ring temperature estimation unit 116 estimates the ring based on the amount of heat radiated from the ring groove 47 to the piston ring 48 based on the estimated ring groove temperature and the amount of heat radiated from the piston ring 48 to the cylinder 20 based on the estimated cylinder temperature. Calculate the temperature.

The heat dissipation amount Q _IN from the ring groove 47 to the piston ring 48 can be obtained based on the following (3). The heat dissipation amount Q _OUT from the piston ring 48 to the cylinder 20 can be obtained based on the following (4).
Q _IN = (T _PIST -T _RING ) / R _PIST-RING ... (3)
Q _OUT = (T _RING -T _CYLI ) / R _RING-CYLI ... (4)
T _PIST : Estimated ring groove temperature T _RING : Estimated ring temperature R _PIST-RING : Thermal resistance between piston 40 and piston ring 48 T _CYLI : Estimated cylinder temperature R _RING-CYLI : Between piston ring 48 and cylinder 20 Thermal resistance

In a steady state, that is, in a state where the heat radiation amount Q _IN from the ring groove 47 to the piston ring 48 and the heat radiation amount Q _OUT from the piston ring 48 to the cylinder 20 are equal, the estimated ring temperature T _RING is expressed by the following equation (5). Meet.
T _RING = (R _RING-CYLI x T _PIST + R _PIST-RING x T _CYLI ) / (R _PIST-RING + R _RING-CYLI )
... (5)

The piston ring temperature estimation unit 116 substitutes the estimated ring groove temperature T _RING obtained by the processing of the ring groove temperature estimation unit 114 and the estimated cylinder temperature T _CYLI estimated by the cylinder temperature estimation unit 115 into the equation (5). By doing so, the estimated ring temperature T _RING is calculated. The formula for calculating the estimated ring temperature T _RING is not limited to the formula (5). Further, the information used for calculating the estimated ring temperature T _RING may be in a map format such as a mouth temperature estimation map.

The estimated ring temperature and the actual temperature of the piston ring 48 may differ depending on the state of the engine 10. In particular, in a situation where the state of the engine 10 changes transiently, the difference between the estimated ring temperature and the actual temperature of the piston ring 48 is remarkable. Then, depending on the state of the engine 10, the time constant indicating the degree of change in the estimated ring temperature changes.

Therefore, the piston ring temperature estimation unit 116 further corrects the estimated ring temperature by using the time constant corresponding to the state of the engine 10, and calculates the corrected ring temperature.

The piston ring temperature estimation unit 116 determines the change status of the estimated ring temperature, the operating state of the engine 10, and the injection state of cooling oil to the piston 40 from among the plurality of time constants stored in the storage unit 120. Based on, select a given time constant. The piston ring temperature estimation unit 116 corrects the estimated ring temperature based on a predetermined time constant selected.

The piston ring temperature estimation unit 116 adds the value obtained by dividing the difference value between the newly estimated estimated ring temperature and the estimated ring temperature estimated one cycle before by a predetermined time constant to the estimated ring temperature one cycle before. By doing so, the estimated ring temperature is corrected. Thereby, the estimated ring temperature can be corrected to correspond to the speed of change in the temperature of the actual piston ring 48.

When the rate of change of the estimated ring temperature is fast, the piston ring temperature estimation unit 116 selects a relatively small time constant. As a result, the corrected ring temperature is greatly affected by the newly estimated estimated ring temperature.

Further, when the rate of change of the estimated ring temperature is slow, the piston ring temperature estimation unit 116 selects a relatively large time constant. As a result, the corrected ring temperature is greatly affected by the estimated ring temperature estimated in the past.

The piston ring temperature estimation unit 116 calculates the corrected ring temperature T _PSC using, for example, the following equation (6). The formula for calculating the correction ring temperature is not limited to the formula (6).
T _PSC = T _PSO + γ × ( _{TPS-T PSO} ₎ / τ ・・・ (6)
T _PSO : Estimated ring temperature estimated one cycle before T _PS : Estimated ring temperature newly estimated γ: Predetermined value τ: Time constant

(Gap estimation unit 117)
The gap estimation unit 117 estimates the size C _SIZE (see FIG. 2) of the joint gap C of the piston ring 48 when it is hot, based on the estimated cylinder temperature and the correction ring temperature. The gap estimation unit 117 calculates the amount of change dC (see FIG. 2) of the abutment gap C using, for example, the following equation (7). The formula for calculating the amount of change dC in the gap C is not limited to the formula (7).
dC = π × D × (K _RING × α _RING × dT _RING －K _CYLI × α _CYLI × dT _CYLI ) ・・・ (7)
π: Pi D: Inner diameter (nominal diameter) of the cylinder 20 (liner 22) at standard temperature
K _RING , K _CYLI : Predetermined value α _RING : Linear expansion coefficient of piston ring 48 dT _RING : Correction of ring temperature increase from standard temperature ( _TPSC -standard temperature)
α _CYLI : Linear expansion coefficient of cylinder 20 dT _CYLI : Estimated increase in cylinder temperature from standard temperature (T _CYLI -standard temperature)

The gap estimation unit 117 estimates the size C _SIZE of the abutment gap C based on the following equation (8). The formula for calculating the size C _SIZE of the joint gap C is not limited to the formula (8).
C _SIZE = C _STD -dC ... (8)
C _STD : The size of the abutment gap C at standard temperature

(Gap control unit 130)
The gap control unit 130 controls the following joint gap controls A, B, in order to control the size C _SIZE of the joint gap C based on the size C _SIZE of the joint gap C obtained by the joint gap estimation device 110. Performs any one of C and D. It should be noted that at least two of the joint gap control A, B, C, and D may be performed.

Abutment gap control A: When the cooling oil is not injected, the supply valve 62 is controlled to inject the cooling oil having a reference amount of injection amount per unit time. Abutment gap control B: The reference amount of cooling oil is injected. If so, the variable oil pump 64 is controlled to increase the injection amount of cooling oil per unit time. Abutment clearance control C: Reduce the supply amount of cooling water to the cylinder 20 per unit time. Abutment clearance control D: Piston. Reduce the amount of heat supplied to 40

When the joint gap control A is performed, the temperature of the piston 40 is lowered by cooling with the newly injected reference amount of cooling oil. As the temperature of the piston 40 decreases, the temperature of the piston ring 48 also decreases. As a result, the piston ring 48 contracts, and the abutment gap C becomes large.

When the joint gap control B is performed, the injection amount of the cooling oil becomes larger than the reference amount, the cooling capacity of the cooling oil is improved, and the temperature of the piston 40 is lowered. As the temperature of the piston 40 decreases, the piston ring 48 contracts and the abutment gap C becomes larger.

When the joint gap control C is performed, the temperature of the cylinder 20 rises, so that the heat radiation amount Q _OUT from the piston ring 48 to the cylinder 20 increases, and the temperature of the piston ring 48 decreases. As a result, the piston ring 48 contracts, and the abutment gap C becomes large.
For example, when the temperature of the cylinder 20 (estimated cylinder temperature T _CYLI ) decreases, the (temperature estimated ring temperature T _RING ) of the piston ring 48 decreases according to the equation (5). On the other hand, the amount of change dC of the joint gap C obtained based on the equation (7) increases as the temperature of the cylinder 20 decreases. However, the thermal resistance between the piston 40 and the piston ring 48 and the thermal resistance between the piston ring 48 and the cylinder 20 are the same (R _PIST-RING = R _RING-CYLI ), and the linear expansion of the piston ring 48 Assuming that the coefficient and the linear expansion coefficient of the cylinder 20 are the same (α _RING = α _CYLI = α), the following equation (9) is obtained from the equations (5) and (7).
dC = π × D × (α / 2) × (K _RING × dT _PIST －K _CYLI × dT _CYLI ) ・・・ (9)
From the above equation (9), by raising the temperature of the cylinder 20, the temperature of the ring groove 47 (estimated ring groove temperature T _PIST ) and the temperature of the piston ring 48 decrease, and the abutment gap C becomes large.

When the abutment gap control D is performed, the temperature of the piston ring 48 drops, the piston ring 48 contracts, and the abutment gap C becomes large. As a result, contact and wear of the abutment portion of the piston ring 48 are suppressed. As the control for reducing the amount of heat supplied to the piston 40, the control for reducing the fuel injection amount to the combustion chamber 11 and the fuel injection timing for the combustion chamber 11 are delayed (the crank shaft 55 is higher than the position where the position of the piston 40 is the highest). Of the control (injecting fuel at the timing when the rotation of the piston advances) and the control for increasing the EGR gas flow rate, at least one control can be exemplified.

[Operation of the joint gap control device]
Next, the operation of the joint gap control device 100 will be described. 5, 6 and 7 are flowcharts showing an example of the operation of the joint gap control device.

First, as shown in FIG. 5, the acquisition unit 111 of the joint gap control device 100 acquires engine state information (step S1).

Next, the mouth temperature estimation unit 112 of the abutment gap control device 100 includes the rotation speed and fuel injection amount of the crankshaft 55 included in the engine state information acquired by the acquisition unit 111, and the mouth temperature stored in the storage unit 120. The estimated mouth temperature is estimated based on the estimation map and the like (step S2).

Next, the determination unit 113 of the joint gap control device 100 determines whether or not the cooling oil is injected based on the information regarding the presence or absence of the injection of the cooling oil included in the engine state information acquired by the acquisition unit 111. Is determined (step S3).

When it is determined by the determination unit 113 that the cooling oil has been injected (step S3: YES), the ring groove temperature estimation unit 114 of the abutment gap control device 100 has the first estimation formula stored in the storage unit 120. The estimated ring groove temperature is estimated based on (Equation (1)) and the estimated mouth temperature (step S4).

On the other hand, when the determination unit 113 determines that the cooling oil has not been injected (step S3: NO), the ring groove temperature estimation unit 114 has a second estimation formula (formula (2)) stored in the storage unit 120. )) And the estimated mouth temperature, and the estimated ring groove temperature is estimated (step S5).

After the process of step S4 or step S5, the cylinder temperature estimation unit 115 of the joint gap control device 100 determines the estimated cylinder temperature based on the temperature of the cooling water of the cylinder 20 included in the engine state information acquired by the acquisition unit 111. Is estimated (step S6).

Next, the piston ring temperature estimation unit 116 estimates the estimated ring temperature based on the calculation formula (formula (5)), the estimated ring groove temperature, and the estimated cylinder temperature (step S7).

Next, the piston ring temperature estimation unit 116 is based on the operating state of the engine 10 and the injection state of the cooling oil included in the engine state information acquired by the acquisition unit 111, and the change state of the estimated ring temperature. Select the time constant (step S8).

Next, the piston ring temperature estimation unit 116 calculates the correction ring temperature based on the calculation formula (formula (6)), the time constant selected in step S8, and the estimated ring temperature (step S9). When performing the joint gap control process in the first cycle, the estimated ring temperature T _PSO estimated one cycle before the equation (6) does not exist. In this case, the oil temperature, the cooling water temperature, the estimated mouth temperature separately calculated, or a preset value may be used as the estimated ring temperature T _PSO .

Next, the gap estimation unit 117 of the joint gap control device 100 is based on the calculation formulas (formulas (7) and (8)), the estimated cylinder temperature, and the correction ring temperature, and the size C of the joint gap C. Estimate the _SIZE (step S10).

Next, as shown in FIG. 6, the gap control unit 130 of the joint gap control device 100 determines whether or not the size C _SIZE of the joint gap C is less than the lower limit value (step S11).

When the gap control unit 130 determines that the size C _SIZE of the joint gap C is equal to or greater than the lower limit value (step S11: NO), the gap control unit 130 stops the injection of the cooling oil (step S12). As described above, by stopping the injection of the cooling oil when the size C _SIZE of the abutment gap C is equal to or larger than the lower limit value, it is possible to suppress an increase in the amount of the cooling oil used. If the injection of the cooling oil is stopped at the time of performing the processing in step S12, the gap control unit 130 does not particularly perform the processing.

Next, the gap control unit 130 determines whether or not to end the joint gap control (step S13).

The gap control unit 130 ends the process when it is determined to end the joint gap control (step S13: YES), for example, when the operation of the engine 10 is completed. On the other hand, when the gap control unit 130 determines that the joint gap control is not terminated (step S13: NO), the joint gap control device 100 performs the process of step S1.

When the gap control unit 130 determines that the size C _SIZE of the joint gap C is less than the lower limit value (step S11: YES), the gap control unit 130 sprays a reference amount of cooling oil (joint gap control A) to reduce the size C of the joint gap C. It is determined whether or not the size C _SIZE is equal to or greater than the lower limit (step S14). For example, when the size C _SIZE of the abutment gap C is less than the lower limit value and is equal to or larger than the first threshold value, the gap control unit 130 sets the size C _SIZE of the abutment gap C to the lower limit value by injecting a reference amount of cooling oil. If it is less than the first threshold value, it is determined that the size C _SIZE of the abutment gap C does not exceed the lower limit value due to the injection of the reference amount of cooling oil. Further, when the reference amount of cooling oil has already been injected, the gap control unit 130 determines that the size C _SIZE of the abutment gap C does not exceed the lower limit value due to the injection of the reference amount of cooling oil.

When the gap control unit 130 determines that the size C _SIZE of the abutment gap C becomes equal to or greater than the lower limit value by injecting a reference amount of cooling oil (step S14: YES), the gap control unit 130 controls the supply valve 62 to control the reference amount. The injection of the cooling oil is started (the joint gap control A is performed) (step S15). After that, the gap control unit 130 performs the process of step S13.

When the gap control unit 130 determines that the size C _SIZE of the joint gap C does not exceed the lower limit value due to the injection of the reference amount of cooling oil (step S14: NO), the injection amount of the cooling oil is increased (the gap control). By B), it is determined whether or not the size C _SIZE of the abutment gap C becomes equal to or greater than the lower limit value (step S16). For example, in the gap control unit 130, when the size C _SIZE of the abutment gap C is less than the first threshold value and equal to or more than the second threshold value, the size C _SIZE of the abutment gap C is the lower limit due to the increase in the injection amount of the cooling oil. It is determined that the value is equal to or greater than the value, and if it is less than the second threshold value, it is determined that the size C _SIZE of the abutment gap C does not exceed the lower limit value due to the increase in the injection amount of the cooling oil.

When the gap control unit 130 determines that the size C _SIZE of the joint gap C becomes equal to or higher than the lower limit value due to the increase in the injection amount of the cooling oil (step S16: YES), the gap control unit 130 controls the variable oil pump 64 to inject the cooling oil. The amount is increased by a predetermined amount (the joint gap control B is performed) (step S17). After that, the gap control unit 130 performs the process of step S13.

When the gap control unit 130 determines that the size C _SIZE of the joint gap C does not exceed the lower limit value due to the increase in the injection amount of the cooling oil (step S16: NO), as shown in FIG. 7, to the cylinder 20. It is determined whether or not the size C _SIZE of the joint gap C becomes equal to or greater than the lower limit value by reducing the supply amount of the cooling water (joint gap control C) (step S18). For example, in the gap control unit 130, when the size C _SIZE of the abutment gap C is less than the second threshold value and equal to or more than the third threshold value, the size C _SIZE of the abutment gap C is the lower limit due to the decrease in the supply amount of the cooling water. It is determined that the value is equal to or greater than the value, and if it is less than the third threshold value, it is determined that the size C _SIZE of the abutment gap C does not exceed the lower limit value due to the decrease in the supply amount of the cooling water.

When the gap control unit 130 determines that the size C _SIZE of the abutment gap C becomes equal to or greater than the lower limit due to the decrease in the supply amount of the cooling water (step S18: YES), the gap control unit 130 sets the supply amount of the cooling water to the cylinder 20 to a predetermined amount. Decrease (perform abutment gap control C) (step S19). After that, the gap control unit 130 performs the process of step S13.

When the gap control unit 130 determines that the size C _SIZE of the joint gap C does not exceed the lower limit due to the decrease in the supply amount of cooling water (step S18: NO), the contact or wear of the joint portion of the piston ring 48 is caused. It is determined whether or not there is a possibility of occurrence (step S20). For example, the gap control unit 130 determines that if the size C _SIZE of the abutment gap C is less than the third threshold value and is greater than or equal to the fourth threshold value, there is no possibility of contact or wear of the abutment portion, and the fourth If it is less than the threshold value of, it is determined that there is a possibility that contact or wear of the abutment portion may occur.

When the gap control unit 130 determines that contact or wear of the abutment portion may occur (step S20: YES), the gap control unit 130 controls to reduce the amount of heat supplied to the piston 40 (step S21). After that, the gap control unit 130 performs the process of step S13.

When the gap control unit 130 determines that there is no possibility of contact or wear of the abutment portion (step S20: NO), the gap control unit 130 performs the process of step S13.

[Action and effect of the embodiment]
The joint gap estimation device 110 of the joint gap control device 100 estimates the estimated mouth portion temperature of the mouth portion 43 of the cavity 42 of the piston 40, and estimates the ring based on the estimated mouth portion temperature and the temperature estimation information. Estimate the groove temperature. The joint gap estimation device 110 estimates the estimated ring temperature of the piston ring 48 based on the estimated ring groove temperature, and estimates the size C _SIZE of the joint gap C based on the estimated ring temperature. Therefore, the size C _SIZE of the abutment gap C can be appropriately estimated based on the estimated ring temperature obtained based on the estimated ring groove temperature close to the actual temperature of the piston ring 48. Further, the abutment gap control device 100 can appropriately control the size C _SIZE of the abutment gap C based on the appropriately estimated size C _SIZE of the abutment gap C. As a result, wear of the cylinder 20 and the piston ring 48 can be suppressed, seizure of the sliding surface of the cylinder 20 and the piston ring 48 can be suppressed, and the durability of the engine 10 can be improved.

The joint gap estimation device 110 estimates the estimated ring groove temperature using different estimation formulas depending on whether or not the cooling oil is injected. Therefore, the estimated ring groove temperature can be estimated more appropriately depending on whether or not the piston 40 is cooled by the cooling oil. As a result, the size C _SIZE of the abutment gap C can be estimated accurately.

The joint gap estimation device 110 calculates the corrected ring temperature obtained by correcting the estimated ring temperature based on a time constant indicating the degree of change in the temperature of the piston ring 48. Therefore, the temperature of the piston ring 48 at the time of estimation can be estimated more appropriately. As a result, the size C _SIZE of the abutment gap C can be estimated accurately.

The joint gap estimation device 110 is selected from a plurality of time constants at a predetermined time based on the change state of the temperature of the piston ring 48, the rotation speed of the crankshaft 55, the fuel injection amount, and the injection state of the cooling oil. The correction ring temperature is calculated using the constant. Therefore, the actual temperature of the piston ring 48 can be estimated accurately. As a result, the size C _SIZE of the abutment gap C can be estimated more accurately.

The joint gap estimation device 110 estimates the size C _SIZE of the joint gap C based on the correction ring temperature and the estimated cylinder temperature. In this way, by reflecting the expansion of the cylinder 20 in addition to the expansion of the piston ring 48, the size C _SIZE of the abutment gap C can be estimated more accurately.

[Modified example of the embodiment]
Needless to say, the present disclosure is not limited to those shown in the embodiments described above, and various modifications can be made without departing from the spirit of the present disclosure.

The ring groove temperature estimation unit 114 may estimate the estimated ring groove temperature using the same estimation formula regardless of whether or not the cooling oil is injected. In this case, for example, the first-order approximation formula of the data when the cooling oil is injected and the data when the cooling oil is not injected, which is shown in FIG. 4, is obtained as an estimation formula and estimated by this estimation formula. Substitute the mouth temperature.

Instead of providing the cylinder temperature estimation unit 115, the gap estimation unit 117 may estimate the size C _SIZE of the abutment gap C based on the estimated ring temperature.

As an example of the other part temperature estimation part, the mouth temperature estimation part 112 is illustrated, but it is a specific part of the top surface or the outer peripheral surface of the piston upper portion 41 which is an example of the other part, and the temperature is higher than that of the ring groove 47. The other part temperature estimation unit that estimates the temperature of the high portion may be applied, and the ring groove temperature estimation unit 114 may estimate the temperature of the skirt portion 49 based on the temperature estimated by the other part temperature estimation unit. Such a configuration using another temperature estimation unit is useful for a gasoline engine in which a cavity does not exist in the piston.

The gap control unit 130 may control the supply valve 62 without controlling the variable oil pump 64 in the joint gap control B to increase the injection amount of the cooling oil per unit time.

The first to eighth time constants were used properly, but it is not limited to this. For example, the time constant may be further subdivided based on the temperature change state of the piston ring 48, the engine operating state, and the injection state of the cooling oil. Other parameters may be taken into consideration when subdividing the time constant.

The gap estimation unit 117 estimates the size C _SIZE of the abutment gap C based on the estimated ring temperature and the estimated cylinder temperature without providing the piston ring temperature estimation unit 116 with a function to correct the estimated ring temperature. You may do so.

All disclosures of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2020-160069 filed on September 24, 2020 are incorporated herein by reference.

The configuration of the present disclosure can be applied to a joint gap estimation device, a joint gap control device, a joint gap estimation method, and a joint gap control method.

10 Engine 11 Combustion chamber 20 Cylinder 21 Cooling passage 22 Liner 23 Cylinder head 24 Injector 25 Intake port 26 Exhaust port 27 Intake valve 28 Exhaust valve 40 Piston 41 Piston upper part 42 Cavity 43 Mouth 44 Cooling channel 45 Intro hole 46 47 Ring groove 48 Piston ring 48A 1st abutment surface 48B 2nd abutment surface 49 Skirt part 50 Pin boss part 51 Pin fitting hole 52 Piston pin 53 Conrod 54 Cylinder pin 55 Cylinder shaft 61 Oil jet 62 Supply valve 63 Nozzle 64 Variable oil Pump 65 Oil passage 100 Joint gap control device 110 Joint gap estimation device 111 Acquisition unit 112 Mouth temperature estimation unit 113 Judgment unit 114 Ring groove temperature estimation unit 115 Cylinder temperature estimation unit 116 Piston ring temperature estimation unit 117 Gap estimation unit 120 Storage unit 130 Gap control unit C Abutment gap P Clearance

Claims

The other part temperature estimation part that estimates the temperature of other parts other than the ring groove in the piston that constitutes the internal combustion engine, and the other part temperature estimation part.
A ring groove temperature estimation unit that estimates the temperature of the ring groove based on the temperature of the other unit estimated by the other unit temperature estimation unit, and a ring groove temperature estimation unit.
A piston ring temperature estimation unit that estimates the temperature of the piston ring mounted on the ring groove based on the temperature of the ring groove estimated by the ring groove temperature estimation unit, and a piston ring temperature estimation unit.
A joint gap estimation device including a gap estimation unit that estimates the size of the gap at the joint of the piston ring based on the temperature of the piston ring estimated by the piston ring temperature estimation unit.
The ring groove temperature estimation unit is based on temperature estimation information indicating the relationship between the temperature of the other unit and the temperature of the ring groove, and the temperature of the other unit estimated by the temperature estimation unit of the other unit. The joint gap estimation device according to claim 1, which estimates the temperature of the ring groove.
Further provided with a determination unit for determining whether or not the oil jet is injecting oil toward the piston.
The temperature estimation information is
The first estimation information used for estimating the temperature of the ring groove when the oil jet is injecting oil, and
A second estimation information used for estimating the temperature of the ring groove when no oil is injected is provided.
The ring groove temperature estimation unit is
When it is determined by the determination unit that the oil jet is injecting oil, the said first estimation information and the temperature of the other part estimated by the other part temperature estimation unit are used. Estimate the temperature of the ring groove and
When the determination unit determines that the oil jet is not injecting oil, the second estimation information and the temperature of the other unit estimated by the temperature estimation unit of the other unit are used as the basis for the determination. The joint gap estimation device according to claim 2, which estimates the temperature of the ring groove.
Further provided with a cylinder temperature estimation unit that estimates the temperature of the cylinder that houses the piston so that it can be reciprocated.
The piston ring temperature estimation unit of the piston ring is based on the temperature of the ring groove obtained by the processing of the ring groove temperature estimation unit and the temperature of the cylinder estimated by the cylinder temperature estimation unit. The joint gap estimation device according to claim 1, which estimates the temperature.
The joint gap estimation device according to claim 1, wherein the piston ring temperature estimation unit corrects the estimated piston ring temperature based on a time constant indicating the degree of change in the temperature of the piston ring.
The other portion is the mouth portion of the cavity of the piston, which is the joint gap estimation device according to claim 1.
The joint gap estimation device according to claim 1 and
A joint gap control device including a gap control unit that controls the size of the gap in the joint based on the size of the gap in the joint of the piston ring estimated by the joint gap estimation device.
The gap control unit has an injection state of oil injected from the oil jet toward the piston, a supply amount of oil supplied to the lubricated portion of the internal combustion engine, in order to control the size of the gap at the abutment. The joint gap control device according to claim 7, which controls at least one of the flow rate of the cooling water of the cylinder that houses the piston so as to be reciprocally movable and the amount of heat supplied to the piston.
The step of estimating the temperature of the parts other than the ring groove in the piston that constitutes the internal combustion engine, and
A step of estimating the temperature of the ring groove in the piston based on the estimated temperature of the other part, and
A step of estimating the temperature of the piston ring mounted on the ring groove based on the estimated temperature of the ring groove, and
A method for estimating a gap between joints, which comprises a step of estimating the size of a gap at the joint of the piston ring based on the estimated temperature of the piston ring.
The other part is the mouth part of the cavity of the piston, which is the method for estimating the gap between the joints according to claim 9.
A step of executing the joint gap estimation method according to claim 9 or 10.
A method for controlling a gap between abutments, which is a step of controlling the size of the gap between the abutments based on the size of the gap at the abutment of the piston ring estimated by executing the method for estimating the gap between the abutments.