JP7119897B2 - Lubrication system for internal combustion engines - Google Patents

Description

The present invention relates to a lubrication system for internal combustion engines.

BACKGROUND ART In order to reduce nitrogen oxides (NOx) in exhaust, a technique is known in which an exhaust passage and an intake passage are connected by an EGR passage and part of the exhaust is introduced into a combustion chamber. When the engine is cold, the wall surface temperature of the bore is low, and moisture in the EGR gas and acids such as sulfuric acid vapor may condense to generate acidic condensed water. Such condensate corrodes and wears the inner walls of the bore. Therefore, a technique for supplying a neutralizing agent that neutralizes acid has been developed (for example, Patent Document 1).

JP-A-9-324706

However, the provision of a new neutralizing agent and its supply device increases the size and cost of the internal combustion engine. Therefore, it is an object of the present invention to provide a lubricating device for an internal combustion engine that can suppress an increase in size and cost, and can suppress corrosion and wear due to condensed water.

The above object is provided with an oil supply section that supplies oil to a bore of an internal combustion engine having an EGR passage through which EGR gas flows, and a control section that controls the amount of oil supplied from the oil supply section. When the EGR gas flows through the passage, if the amount of condensed water that remains in the bore or the rate of retention of the condensed water generated from the EGR gas is equal to or greater than a predetermined value, the amount of retention or the rate of retention of the condensed water is equal to or greater than the predetermined value. Said control can be achieved by means of a lubrication system of an internal combustion engine which increases said quantity of oil compared to when it is less than.

It is possible to provide a lubricating device for an internal combustion engine that can suppress an increase in size and cost, and can suppress corrosion and wear due to condensed water.

FIG. 1 is a schematic diagram illustrating a lubricating device. FIG. 2(a) is a diagram showing the relationship between the water temperature and the wall temperature. FIG.2(b) is a figure which shows a saturated water vapor curve. FIG. 2(c) is a diagram showing the relationship between the distance from the wall surface and the intake air temperature. FIG. 2(d) is a map of the amount of condensation based on the temperature of the intake air and the wall temperature. FIG. 3 is a diagram illustrating the relationship between the water temperature and the amount of condensed water retained. FIG. 4 is a flowchart illustrating processing executed by an ECU. FIG. 5 is a flowchart illustrating processing executed by the ECU.

(First embodiment)
A lubricating device for an internal combustion engine according to this embodiment will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a lubricating device 100. FIG. A lubricating device 100 is applied to an internal combustion engine 10, includes a valve 44, an oil jet 46, and an ECU (Electric Control Unit) 50, and is mounted on a vehicle such as an automobile.

The internal combustion engine 10 is, for example, a gasoline engine, and includes a cylinder head 11 , a cylinder block 12 , a piston 14 , connecting rods 15 , fuel injection valves 22 and spark plugs 24 .

A cylinder head 11 is attached to the upper portion of the cylinder block 12 . A bore 13 is formed in the cylinder head 11 and the cylinder block 12 . Piston 14 is slidably disposed within bore 13 . One end of the connecting rod 15 is connected to the piston 14 and the other end is connected to the crankshaft 16 . A combustion chamber 19 is formed in the bore 13 . A water jacket 17 through which cooling water flows is provided around the bore 13 of the internal combustion engine 10 .

A spark plug 24, an intake valve 26 and an exhaust valve 28 are provided in the cylinder head 11, and an intake passage 20 and an exhaust passage 21 are connected. The intake passage 20 is provided with an air flow meter 23, a throttle valve 25, a temperature sensor 27, and a fuel injection valve 22 in this order from the upstream side. The exhaust passage 21 is provided with a filter and a catalyst (not shown).

The airflow meter 23 measures the intake flow rate. The flow rate of intake air is adjusted according to the opening degree of the throttle valve 25, and the greater the opening degree, the greater the flow rate. A temperature sensor 27 measures the temperature of the intake air.

A fuel injection valve 22 is provided in the intake passage 20 and injects fuel. A mixture of fuel and air is introduced from the intake passage 20 into the combustion chamber 19 by opening the intake valve 26 . Piston 14 rises and the mixture is compressed. When the air-fuel mixture is ignited by the ignition plug 24, the combustion of the air-fuel mixture increases the pressure in the cylinder, causing the piston 14 to slide downward. At this time, power is transmitted to the crankshaft 16 . A crank angle sensor 29 detects the rotational speed of the internal combustion engine 10 . The piston 14 rises and the exhaust valve 28 opens, so that the exhaust after combustion is discharged to the exhaust passage 21 . Part of the exhaust circulates to the intake passage 20 through the EGR passage 30 .

An EGR passage 30 is connected between the intake passage 20 and the exhaust passage 21 . One end of the EGR passage 30 is connected between the throttle valve 25 and the fuel injection valve 22 of the intake passage 20 and the other end is connected to the exhaust passage 21 . Part of the exhaust gas (EGR gas) is recirculated to the intake passage 20 through the EGR passage 30 and supplied to the internal combustion engine 10 .

An EGR cooler 34 is provided in the middle of the EGR passage 30 . The EGR gas and cooling water exchange heat in the EGR cooler 34 to cool the EGR gas. An EGR valve 38 is provided between the EGR cooler 34 and the intake passage 20 in the EGR passage 30 . The flow rate of the EGR gas is adjusted by the degree of opening of the EGR valve 38, and the greater the degree of opening, the greater the flow rate. A temperature sensor 36 is provided in the EGR cooler 34 . A temperature sensor 36 measures the temperature of cooling water in the EGR cooler 34 .

A bypass passage 32 is connected to the EGR passage 30 , and the EGR gas can flow into the intake passage 20 through the bypass passage 32 without passing through the EGR cooler 34 . A bypass valve 33 is provided in the bypass passage 32 , and the flow rate of the EGR gas in the bypass passage 32 is adjusted by the degree of opening of the bypass valve 33 .

The cylinder block 12 of the internal combustion engine 10 is provided with an oil jet 46 (oil supply portion), and the nozzle of the oil jet 46 is arranged inside the bore 13 . Oil is stored in the oil pan 40 , and the oil pan 40 and the oil jet 46 are connected by an oil passage 41 . A pump 42 and a valve 44 are provided in the oil passage 41 .

The pump 42 is operated by the rotation of the crankshaft 16 to pump oil from the oil pan 40 and share it with the oil jets 46 . The oil jet 46 injects oil toward the piston 14 inside the bore 13 . The oil forms an oil film to lubricate and cool the piston 14 .

A valve 44 regulates the supply of oil to an oil jet 46 . When the valve 44 is opened, oil is supplied to the oil jet 46, and when the valve 44 is closed, the supply of oil is stopped.

The ECU 50 includes storage devices such as a CPU (Central Processing Unit), RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 50 performs various controls by executing programs stored in a storage device. The ECU 50 acquires the intake air flow rate from the airflow meter 23 , the intake air temperature from the temperature sensor 27 , and the water temperature from the temperature sensor 36 . The ECU 50 adjusts the opening of the throttle valve 25 and the opening of the EGR valve 38 . The degree of opening of the EGR valve 38 is controlled according to the rotational speed of the internal combustion engine 10, for example. The ECU 50 calculates the flow rate of EGR gas (EGR flow rate) from, for example, the degree of opening of the EGR valve 38, and calculates the EGR rate based on the intake flow rate and the EGR flow rate. For example, if the EGR valve 38 is fully closed, the EGR rate is zero, and if the EGR valve 38 is open, the EGR rate is greater than zero.

As will be described later, the ECU 50 calculates the retention speed and retention amount of the condensed water, and stores the retention amount. Furthermore, the ECU 50 functions as a control unit that controls the amount of oil injected from the oil jet 46 by adjusting the opening of the valve 44 .

For example, when the engine is cold, the temperature of the oil is low, so if the oil jet 46 supplies oil to the bore 13, the warm-up performance of the internal combustion engine 10 deteriorates. In addition, since the viscosity of the oil is high, the work load of the pump 42 increases and the load on the internal combustion engine 10 also increases. Therefore, the ECU 50 can close the valve 44 and stop the supply of oil by the oil jet 46 . Cooling of the piston 14 and the like by oil is suppressed, and warm-up performance is improved. In addition, the amount of work of the pump 42 is reduced and the fuel efficiency is improved.

Since the wall surface temperature of the bore 13 is low when the engine is cold, when the EGR gas is introduced into the internal combustion engine 10, moisture and sulfuric acid vapor in the EGR gas may condense to generate acidic condensed water. The acidic condensed water corrodes the inner wall of the bore 13 and the like, and breaks the oil film to wear the inner wall of the bore 13, the piston 14, and the like. The wear rate of the bore 13 increases as the amount of condensed water retained on the inner wall of the bore 13 increases.

Generation of condensed water will be described. FIG. 2(a) is a diagram showing the relationship between the water temperature and the wall temperature. The horizontal axis represents the water temperature Tw1 of the EGR cooler 34 and the vertical axis represents the temperature Tw2 of the inner wall of the bore 13 . As shown in FIG. 2(a), the higher the water temperature Tw1, the higher the wall temperature Tw2. Therefore, the ECU 50 can estimate the wall temperature Tw2 based on the water temperature Tw1 obtained from the temperature sensor .

FIG.2(b) is a figure which shows a saturated water vapor curve. The horizontal axis represents temperature, and the vertical axis represents saturated water vapor pressure. The temperature corresponding to the saturated water vapor pressure Pm in the intake air mixed with the EGR gas is the dew point Td of the mixed intake air. The saturated water vapor pressure Pm in the intake air mixed with the EGR gas is obtained by the following equation using the saturated water vapor pressure Pe of the EGR gas and the water vapor pressure Pi of the intake air.
Pm = EGR rate x Pe + (1-EGR rate) x Pi

FIG. 2(c) is a diagram showing the relationship between the distance from the wall surface and the intake air temperature. The horizontal axis represents the distance from the inner wall of the bore 13, and the vertical axis represents the temperature of the intake air after mixing. As shown in FIG. 2(c), the temperature of the intake air on the inner wall coincides with the temperature Tw2 of the inner wall, and the temperature rises and approaches a constant as the distance from the inner wall increases. The dotted line is the dew point Td, and the hatched portion is the portion where the intake air temperature is equal to or lower than the dew point Td. Condensed water is generated in this temperature range. That is, the gas in the vicinity of the inner wall of the bore 13 tends to condense. Also, the lower the wall temperature Tw2 and the higher the dew point Td, the wider the shaded area and the greater the amount of dew condensation.

FIG. 2(d) is a map of the amount of condensation based on the temperature of the intake air and the wall temperature. The horizontal axis represents the dew point Td, and the vertical axis represents the wall temperature Tw2. A plurality of solid lines shown in FIG. 2(d) indicate the condensation amount (condensed water generation rate) determined by the dew point Td and the wall temperature Tw2, and the condensation amount increases from the upper side to the lower side. That is, the lower the wall temperature Tw2 and the higher the dew point Td, the greater the amount of dew condensation. As described above, the amount of condensation can be obtained based on the water temperature Tw1, the wall temperature Tw2, the EGR rate, and the saturated steam curve.

Part of the condensed water evaporates, and the evaporation rate is proportional to the difference between the saturated water vapor pressure and the actual water vapor pressure in the intake air after mixing. For example, for the same actual water vapor pressure, the higher the temperature of the intake air, the higher the saturated water vapor pressure, and the greater the difference from the actual water vapor pressure, the greater the evaporation rate. For the same temperature, the lower the actual water vapor pressure, the higher the evaporation rate. As will be described later, the amount of condensed water that remains in the bore 13 is determined based on the condensed water generation rate and the amount of condensed water.

FIG. 3 is a diagram illustrating the relationship between the water temperature and the amount of condensed water retained. The horizontal axis is the water temperature Tw1 of the EGR cooler 34, and the vertical axis is the retention amount of condensed water in the bore 13. As shown in FIG. When the EGR valve 38 opens and the EGR gas flows into the intake passage 20, the retention amount exceeds the threshold value W1 and the wear rate increases within the temperature range from T1 to T2 shown in FIG. In this embodiment, the oil neutralizes the acid in the condensed water.

FIG. 4 is a flowchart illustrating processing executed by the ECU 50, which is performed, for example, when the internal combustion engine 10 is cold. As shown in FIG. 4 , the ECU 50 obtains the water temperature Tw1 from the temperature sensor 36 and the intake air temperature from the temperature sensor 27 . Furthermore, the ECU 50 acquires the EGR rate from the intake flow rate, the opening of the EGR valve 38, and the like (step S10).

The ECU 50 determines whether the EGR rate is 0 (step S11). If the determination is affirmative (Yes), the ECU 50 closes the valve 44 to stop the oil supply (step S22). In the case of a negative determination (No), the ECU 50 determines the condensed water generation speed based on the water temperature Tw1, the wall temperature Tw2, the EGR rate, and the saturated steam curve, as described with reference to FIGS. Calculate (step S12). The ECU 50 calculates the evaporation speed of the condensed water based on the temperature of the intake air (step S14).

The ECU 50 calculates the retention speed V of the condensed water based on the generation speed and the evaporation speed (step S16). The retention rate V is, for example, the difference between the production rate and the evaporation rate, as expressed by the following equation.
Retention rate V = production rate - evaporation rate

The ECU 50 calculates the retention amount W of condensed water (step S18). The ECU 50 stores the retention amount before the start of the current process, and calculates the retention amount W by the following equation including the retention amount and the time integral of the retention speed V, for example.
Retention amount W = Retention amount before treatment start + Time integration of retention speed V

The ECU 50 determines whether or not the retention amount W is equal to or less than the threshold value W1 (step S20). As described above, the retention amount is proportional to the wear rate of the bore 13, and when the retention amount W exceeds the threshold value W1, the wear rate exceeds the allowable limit. If the determination is affirmative (Yes), the ECU 50 closes the valve 44 to stop the oil supply from the oil jet 46 (step S22). On the other hand, if the determination is negative (No), the ECU 50 opens the valve 44 and supplies oil into the bore 13 using the oil jet 46 (step S24). After step S22 or S24, the process ends.

According to the first embodiment, the ECU 50 obtains the residual amount W of condensed water based on the water temperature and the EGR rate, and supplies oil from the oil jet 46 when W is greater than the threshold value W1. The base component in the oil neutralizes the acid component of the condensed water, suppressing corrosion and wear of the inner wall of the bore 13 and the piston 14 due to the condensed water.

Since the oil can be supplied using parts provided in the internal combustion engine 10 such as the oil jet 46 and the valve 44, no additional neutralizer and its supply device are required. Therefore, an increase in size and cost of the internal combustion engine 10 is suppressed.

The ECU 50 can determine the amount of oil injected from the oil jet 46 based on the degree of opening of the valve 44 or the like. The base number of the oil film formed by the oil on the bore 13 and the piston 14 should be high enough to neutralize the acid component of the condensed water.

Although the ECU 50 switches between oil supply and stop, the oil supply amount may be increased or decreased. That is, when the retention amount W is equal to or less than the threshold value W1, the oil supply amount may or may not be zero. If the retention amount W is greater than W1, the oil supply amount is increased compared to the case where it is equal to or less than W1. Note that the threshold value W1 corresponds to the allowable limit of the wear rate, and may be determined according to, for example, the dimensions of the bore 13 and the material of the inner wall.

(Second embodiment)
The configuration of FIG. 1 is also common to the second embodiment. FIG. 5 is a flow chart illustrating the processing executed by the ECU 50. As shown in FIG. Steps S10 to S16 are the same as in FIG. The ECU 50 determines whether or not the residence speed V is positive (step S21). In the case of a negative determination, the ECU 50 stops the oil supply (step S22). If the determination is affirmative, the ECU 50 supplies oil from the oil jet 46 (step S24).

According to the second embodiment, the condensed water retention speed V is obtained based on the water temperature and the EGR rate, and when V is positive, oil is supplied from the oil jet 46 . This suppresses corrosion and wear of the inner wall of the bore 13 and the piston 14 due to condensed water, as in the first embodiment.

If the retention speed V is greater than 0, the ECU 50 immediately supplies the oil, so retention of condensed water can be more effectively suppressed. The threshold value for the residence speed V may be other than 0, for example oil supply may occur when the residence speed V is greater than a predetermined value.

Although the ECU 50 switches between oil supply and stop, the oil supply amount may be increased or decreased. That is, when the residence speed V is zero or less, the oil supply amount may or may not be zero. If the residence velocity V is positive, the oil supply is increased compared to when V is less than or equal to zero.

Although the ECU 50 obtains the condensed water generation speed, evaporation speed, retention speed V, etc. based on the water temperature of the EGR cooler 34, the configuration is not limited to this. The temperature of the internal combustion engine 10, that is, the water temperature or the temperature of the parts can be used, for example the water temperature of the water jacket 17 or the temperature of the intake passage 20, or the like.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the scope of claims. Change is possible.

REFERENCE SIGNS LIST 10 internal combustion engine 11 cylinder head 12 cylinder block 13 bore 14 piston 15 connecting rod 16 crankshaft 17 water jacket 19 combustion chamber 20 intake passage 21 exhaust passage 22 fuel injection valve 23 air flow meter 24 spark plug 25 throttle valve 26 intake valve 27, 36 Temperature sensor 28 exhaust valve 29 crank angle sensor 30 EGR passage 32 bypass passage 33 bypass valve 34 EGR cooler 38 EGR valve 40 oil pan 42 pump 44 valve 46 oil jet 50 ECU
100 Lubricator

Claims (1)

an oil supply unit for supplying oil to a bore of an internal combustion engine having an EGR passage through which EGR gas flows;
a control unit that controls the amount of oil supplied from the oil supply unit,
When the EGR gas flows through the EGR passage, if the amount of condensed water remaining in the bore or the rate of retention of the condensed water generated from the EGR gas is equal to or greater than a predetermined value, the amount of retention or the rate of retention is equal to or higher than the A lubricating device for an internal combustion engine, wherein the control unit increases the amount of the oil compared to when it is less than a predetermined value.

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