WO2010032118A1

WO2010032118A1 - Oil supply control apparatus

Info

Publication number: WO2010032118A1
Application number: PCT/IB2009/006877
Authority: WO
Inventors: Fumio Takamiya
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2008-09-18
Filing date: 2009-09-17
Publication date: 2010-03-25
Anticipated expiration: 2011-03-18
Also published as: JP2010071194A

Abstract

An oil supply control apparatus includes an oil pan (51), a pump mechanism (53) that supplies oil to lubricated portions (10), an ECU (60) that controls supply of the oil, an oil injection nozzle (58), an oil reflux portion (56) that branches off from an oil passage (55t) which leads to the oil injection nozzle (58) and that includes an oil reflux passage (56k) through which part of the oil in the oil passage (55t) is returned to the pump mechanism (53), and an OSV (57) that is provided in the oil reflux portion (56) and that opens and closes the oil reflux passage (56k). When the ECU (60) determines that an engine (1) is in the cold operation mode, the OSV (57) is opened so that part of the oil in the oil passage (55t) is returned to the pump mechanism (53) through the oil reflux passage (56k).

Description

OIL SUPPLY CONTROL APPARATUS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to an oil supply control apparatus, and more specifically to an oil supply control apparatus that controls supply of oil to decrease the amount of toxic substances in the exhaust gas that is discharged from an engine when the engine is in the cold operation mode.

2. Description of the Related Art

[0002] In an engine mounted in a vehicle, for example, an automobile, the oil stored in an oil pan is drawn up by a pump mechanism, pressurized and delivered to an oil passage, for example, a main oil gallery, and then supplied through the oil passage to lubricated portions such as a piston, an intake camshaft journal, an exhaust camshaft journal and a crankshaft journal. An oil supply control apparatus controls the oil supply performed by the pump mechanism in order to lubricate and cool these lubricated portions with the use of an appropriate amount of oil. As a result, these lubricated portions are smoothly operated, and occurrence of damage, for example, burning is prevented.

[0003] For example, Japanese Patent Application Publication No. JP-A-2005-233100 (JP-A-2005-233100) describes an oil supply control apparatus of the above-described type. This oil supply control apparatus includes an oil gallery through which oil is introduced into a cylinder block of an engine, an oil passage for a piston, which is formed in the cylinder block and which communicates with the oil gallery, a jet nozzle for a piston, which is provided in the oil passage for a piston and which injects the oil to the piston of the engine, and an oil relief valve for a piston, which is provided in the oil passage for a piston. In the oil supply control apparatus, the amount of oil that is injected from the jet nozzle for a piston is controlled by operating the oil relief valve for a piston according to a control map and based on the information that indicates the engine operation mode.

[0004] For example, when the engine is operating at high speed and high load and the oil pressure is in a low pressure region that is defined in the control map, the oil relief valve for a piston is closed to increase the oil injection amount. As a result, the cooling effect is enhanced to prevent occurrence of burning. On the other hand, when the engine is operating at high speed and high load and the oil pressure is brought into a considerably high pressure region that is defined in the control map, the oil relief valve for a piston is opened to decrease the oil injection amount. Accordingly, an excessive oil supply is prevented while the cooling effect produced by the oil is sufficiently maintained. As a result, an increase in a mechanical loss is suppressed.

[0005] When the engine is operating at low speed and low load and the oil pressure is in the low pressure region that is defined in the control map, for example, the region where the engine is operating in the cold operation mode, the oil relief valve for a piston is closed to increase the oil injection amount. As a result, the lubrication effect is enhanced to decrease a mechanical loss. On the other hand, when the engine is operating at low speed and low load and the oil pressure is in the high pressure region that is defined in the control map, the oil relief valve for a piston is opened to decrease the oil injection amount. Accordingly, an excessive oil supply is prevented while the cooling effect produced by the oil is sufficiently maintained. As a result, an increase in a mechanical loss is suppressed.

[0006] In the existing oil supply control apparatus described above, when the engine is operating at low speed and low load and the oil pressure is in the low pressure region that is defined in the control map, for example, the region where the engine is operating in the cold operation mode, the oil relief valve for a piston is closed to increase the oil injection amount. As a result, the lubrication effect is enhanced and a mechanical loss is decreased. However, when the engine is operating in the cold operation mode, if the oil injection amount is increased, the following adverse effects may be produced.

[0007] If the oil injection amount is increased, an advantageous effect is produced, that is, a mechanical loss is decreased due to enhanced lubrication of the piston. However, the piston is cooled by the low-temperature oil. If the piston is cooled, the fuel that is supplied into a combustion chamber surrounded by the piston and an engine block adheres to the top face of the piston and vaporization of the fuel is not promoted. Accordingly, an air-fuel mixture in which the proportion between the air and the fuel is not even is formed and the optimum air-fuel ratio is not achieved. As a result, the combustion temperature is decreased and incomplete combustion of the air-fuel mixture occurs. Such an adverse effect becomes prominent especially in a direct-injection engine in which the fuel is injected directly into combustion chambers.

[0008] In this state, combustion is promoted less efficiently than in the optimum state. Therefore, the fuel is discharged in the form of HC (Hydrocarbon), which causes deteriorations of exhaust emission such as increases in the amounts of PM (Particulate Matter) and smoke (soot) that contain so-called SOF (Soluble Organic Fraction). In addition, the fuel consumption rate (g / KWh (g denotes the weight of fuel, KW denotes the output, and h denotes time) is decreased, which decreases so-called fuel efficiency.

[0009] In order to suppress deterioration of the exhaust emission, the fuel injection timing may be retarded so that the fuel injected into the combustion chamber does not adhere to the top face of the piston. In this case, because the fuel injection timing is retarded, the degree to which the air-fuel mixture in the combustion chamber is compressed is increased. Therefore, the temperature in the combustion chamber when the fuel is injected is increased. Also, because the distance between the fuel injection orifice and the top face of the piston increases, the fuel is less likely to adhere to the top face of the piston. As a result, it is possible to suppress formation of PM and smoke to some extent.

[0010] However, if the control for retarding the fuel injection timing is executed, the fuel injection amount is increased as the fuel injection timing is retarded. Therefore, the fuel injection amount is larger when the fuel injection timing is retarded than when the fuel is injected at the optimum injection timing. As a result, the fuel consumption rate decreases, which decreases the fuel efficiency. In addition, when the fuel injection timing is retarded, the fuel combustion period is longer than when the fuel is injected at the optimum fuel injection timing. As a result, the combustion proceeds more slowly and the effective output from the engine may be unstable. In addition, the valve opening/closing timing control and the injection timing retardation control need to be executed in combination, which complicates the controls. <

SUMMARY OF THE INVENTION

[0011] The invention provides an oil supply control apparatus that suppresses cooling of an engine by oil with a simple control to decrease the amount of PM and smoke in the exhaust gas when the engine is in the cold operation mode.

[0012] An aspect of the invention relates to an oil supply control apparatus that includes: an oil pan that stores oil; a pump mechanism that supplies the oil stored in the oil pan to lubricated portions that include a piston of an engine through an oil passage; an oil injection nozzle that injects the oil in the oil passage toward the piston; an oil reflux portion that branches off from the oil passage which leads to the oil injection nozzle and that includes an oil reflux passage through which part of the oil in the oil passage is returned to the pump mechanism; an oil switch valve that is provided in the oil reflux portion and that opens and closes the oil reflux passage; an oil supply control unit that controls supply of the oil; and an operation mode determination unit that determines whether the engine is in a cold operation mode. When the operation mode determination unit determines that the engine is in the cold operation mode, the oil supply control unit opens the oil switch valve so that part of the oil that flows through the oil passage is returned to the pump mechanism through the oil reflux passage.

[0013] With this configuration, when the engine is in the cold operation mode, part of the oil discharged from the pump mechanism is returned to the pump mechanism through the oil reflux portion. Therefore, the pressure of the oil in the oil passage is decreased. In this case, oil injection from the oil injection nozzle toward the piston is stopped, and cooling of the piston by the oil is stopped. In this case, the temperature (⁰C) of the piston becomes higher than that in the related art. Accordingly, vaporization of the fuel supplied into a combustion chamber of the engine is promoted, and the problem that the fuel adheres to the top face of the piston does not occur, unlike the related art. Because part of the oil discharged from the pump mechanism is returned to the pump mechanism through the oil reflux portion, the amount of oil that is supplied into the engine is decreased, and the amount of heat that is transferred from the warmed coolant is decreased. As a result, the temperature (⁰C) of the coolant is made higher than that in the related art and warming-up of the engine that is performed when the engine is cold is promoted. Because vaporization of the fuel is promoted, the air-fuel mixture in which the proportion between the air and the fuel is even is formed and the optimum air-fuel ratio is achieved. Therefore, the air-fuel mixture is completely burned at the appropriate combustion temperature. In this case, the amount of HC contained in the exhaust gas and the amount of PM and smoke that contain so-called SOF (Soluble Organic Fraction) are decreased, and the fuel efficiency is increased. Because part of the oil discharged from the pump mechanism is returned to the pump mechanism through the oil reflux portion, the load on the pump mechanism is decreased and the power (w) of the pump mechanism decreases. In this case, the load on the engine is decreased, and the fuel efficiency is increased.

[0014] In the oil supply control apparatus according to the above-described aspect, the engine may be provided with a cooling device that cools the engine using a coolant, and include a coolant temperature sensor that detects the temperature of the coolant. When the temperature of the coolant detected by the coolant temperature sensor is lower than a preset temperature, the operation mode determination unit may determine that the engine is in the cold operation mode.

[0015] In the configuration described above, when the temperature of the coolant detected by the coolant temperature sensor is lower than the preset temperature, the operation mode determination unit determines that the engine is in the cold operation mode. Therefore, it is possible to determine whether the engine is in the cold operation mode with a simple determination step.

[0016] In the oil supply control apparatus according to the above-described aspect, the engine may include a variable valve timing mechanism that adjusts opening/closing timing of at least one of an intake valve and an exhaust valve using the pressure of the oil, and the oil supply control apparatus may further include an oil pressure sensor that detects the pressure of the oil in the oil passage, and a pressure comparison unit that compares the pressure of the oil detected by the oil pressure sensor with a preset lower limit operation pressure which is the lower limit of pressure for operating the variable valve timing mechanism. When the pressure comparison unit determines that the pressure of the oil detected by the oil pressure sensor is lower than the preset lower limit operation pressure, the oil supply control unit may close the oil switch valve.

[0017] With the configuration described above, even if the engine includes the variable valve timing mechanism, the valve timing control executed by the variable valve timing mechanism is not hindered. This is because the pressure comparison unit compares the detected pressure with the preset lower limit operation pressure. When it is determined that the detected pressure is lower than the preset lower limit operation pressure, the oil switch valve is closed. In this way, a higher priority is given to the control executed by the variable valve timing mechanism than to the oil supply control.

[0018] In the oil supply control apparatus according to the above-described aspect, the engine may include an injection timing control unit that retards fuel injection timing. When the oil switch valve is opened, the oil supply control unit may notify the injection timing control unit that the oil switch valve is opened so that the injection timing control unit suspends the control for retarding the fuel injection timing.

[0019] With this configuration, when the oil switch valve is opened, the injection timing control unit suspends the control for retarding the fuel injection timing and executes the control for optimizing the fuel injection timing. Therefore, the situation where the fuel injection amount is increased as the fuel injection timing is retarded does not occur, unlike the related art. Accordingly, the fuel consumption rate decreases. As a result, deterioration of the so-called fuel efficiency does not occur. In addition, it is possible to avoid the situation where the fuel combustion period is prolonged as the fuel injection timing is retarded, combustion takes place more slowly, and the effective output from the engine becomes unstable. Furthermore, it is no longer necessary to execute the valve opening/closing timing control and the injection timing retardation control in combination. Therefore, it is possible to suppress complication of the controls. At the same time that the operation mode is switched from the cold operation mode to the warm operation mode, suspension of the control for retarding the fuel injection timing is promptly cancelled. At this time, the oil switch valve is closed. Therefore, the oil is injected from the oil injection nozzle toward the piston, and the piston is appropriately cooled and lubricated.

[0020] The oil supply control apparatus according to the above-described aspect of the invention suppresses cooling of an engine by oil with a simple control to decrease the amount of PM and smoke in the exhaust gas when the engine is in the cold operation mode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG 1 is a perspective view schematically showing a vehicle engine to which an oil supply control apparatus according to a first embodiment of the invention is applied;

FIG 2 is a block diagram showing lubricated portions and oil flows in the engine to which the oil supply control apparatus according to the first embodiment of the invention is applied;

FIG 3 is a circuit diagram showing a pump mechanism of the oil supply control apparatus according to the first embodiment of the invention;

FIG. 4 is a partial cross-sectional view showing a cylinder block that houses a piston in the engine to which the oil supply control apparatus according to the first embodiment of the invention is applied;

FIG 5 is a flowchart illustrating the routine of an oil supply control executed by the oil supply control apparatus according to the first embodiment of the invention;

FIG. 6 is a graph showing the oil pressure in a main oil gallery with respect to the engine sped Ne in the oil supply control apparatus according to the first embodiment of the invention;

FIG 7 is a graph showing the relationship between the elapsed time, and the open/closed state of an OSV, the piston temperature and the injection timing when the engine, to which the oil supply control apparatus according to the first embodiment of the invention is applied, is in the cold operation mode;

FIQ 8 is a graph showing the relationship between the elapsed time, and the open/closed state of the OSV, the coolant temperature and the oil temperature when the engine, to which the oil supply control apparatus according to the first embodiment of the invention is applied, is in the cold operation mode;

FIG 9 is a graph showing the relationship between the time that has elapsed after the engine, to which the oil supply control apparatus according to the first embodiment of the invention is applied, is started, and the concentration of PM and smoke in the exhaust gas and the engine speed Ne;

FIG 10 is a perspective view showing an engine to which an oil supply control apparatus according to a second embodiment of the invention is applied;

FIG 11 is a block diagram showing lubricated portions and oil flows in the engine to which the oil supply control apparatus according to the second embodiment of the invention is applied; and

FIG 12 is a flowchart illustrating the routine of an oil supply control executed by the oil supply control apparatus according to the second embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Hereafter, an oil supply control apparatus according to a first embodiment of the invention will be described with reference to the accompanying drawings. FIG 1 is a perspective view schematically showing a vehicle engine to which the oil supply control apparatus according to the first embodiment of the invention is applied. FIG 2 is a block diagram showing lubricated portions and oil flows in the engine. FIG. 3 is a circuit diagram showing a pump mechanism. FIG. 4 is a partial cross-sectional view showing a cylinder block that houses a piston.

[0023] First, the structure of an engine 1 will be described. As shown in FIG. 1, the engine 1 includes a piston 2 that is housed in a cylinder, a variable valve timing (VVT: Variable Valve Timing) mechanism 3, a crankshaft 4, an oil supply control apparatus 5, an engine block 6 that is formed of a cylinder head, a cylinder block and a crankcase, a cooling device 7 that cools the inside of the engine 1, and a fuel injection device (not shown) that injects the fuel directly into the cylinder.

[0024] The piston 2 together with three other pistons (not shown) constitutes the in-line four-cylinder engine 1. The engine 1 is not limited to an in-line four-cylinder engine. A single cylinder engine or a multi-cylinder engine in which cylinders are arranged in any appropriate manner may be used as the engine 1. Also, any known engine that uses a liquid or a gas, which is mixable with the air, as the fuel, for example, a gasoline engine or a diesel engine may be used as the engine 1. For example, an engine that uses hydrocarbon, which is mixable with the air, as the fuel may be used as the engine 1.

[0025] The variable valve timing mechanism 3 includes an intake-side oil pressure controller 33 that is connected to an intake camshaft 31 and that drives a vane actuator 32, and an exhaust-side oil pressure controller 36 that is connected to an exhaust camshaft 34 and that drives a vane actuator 35. The intake-side oil pressure controller 33 and the exhaust-side oil pressure controller 36 are connected to the crankshaft 4 via a chain 37, and driven by the power from the crankshaft 4.

[0026] An intake-side oil control valve (OCV: Oil Control Valve) 33c is connected to the intake-side oil pressure controller 33, and the oil pressure that is supplied to the intake-side oil pressure controller 33 is controlled by the intake-side oil control valve 33c. An exhaust-side oil control valve (OCV) 36c is connected to the exhaust-side oil pressure controller 36, and the oil pressure that is supplied to the exhaust-side oil pressure controller 36 is controlled by the exhaust-side oil control valve 36c.

[0027] An intake valve 42 is connected to the intake camshaft 31 via a rocker arm 41 , and an exhaust valve 44 is connected to the exhaust camshaft 34 via a rocker arm 43. The opening/closing timing of the intake valve 42 is controlled by the intake-side oil pressure controller 33, and the opening/closing timing of the exhaust valve 44 is controlled by the exhaust-side oil pressure controller 36. The intake-side oil pressure controller 33 and the exhaust-side oil pressure controller 36 execute a retardation control and an advance control to increase the efficiency of taking in the air and discharging the exhaust gas and to adjust the output (kW) of the engine 1 and the torque (N x m) that is output from the engine 1.

[0028} For example, if the closing timing of the intake valve 42 is retarded in such a manner that the intake valve 42 is closed after the piston 2 reaches the bottom dead center (BDC), when the air-fuel mixture is compressed in the compression stroke of the engine 1, the volume ratio of the combustion chamber after the intake valve 42 is closed is decreased and the compression ratio is decreased. If the variable valve timing mechanism 3 advances the opening/closing timing that has been retarded, the compression ratio, which has been decreased, is increased.

[0029] The crankshaft 4 is rotatably supported by the engine block 6 via a crankshaft journal 11, and connected to the piston 2 via a connecting rod. With this structure, reciprocation of the piston 2 is transferred to the crankshaft 4 and the crankshaft 4 is rotated.

[0030] The oil supply control apparatus 5 includes an oil pan 51, an oil strainer 52, a pump mechanism 53, an oil filter 54 that filters the oils discharged from the pump mechanism 53, an oil passage portion 55, an oil reflux portion 56, an oil switch valve (OSV) 57, an oil injection nozzle 58, a stop valve 59 that adjusts the flow rate of the oil that flows through the pump mechanism 53 (see FIG. 2), an electronic control unit (ECU) 60, a coolant temperature sensor 61 and an oil pressure sensor 62. The oil supply control apparatus 5 is structured in such a manner that the oil is supplied to lubricated portions 10 in the engine 1 to lubricate and cool the lubricated portions 10.

[0031] The lubricated portions 10 are components that are provided in the engine 1 and that need to be lubricated. As shown in FIG 2, the lubricated portions 10 include, for example, the piston 2, the crankshaft journal 11 that rotatably supports the crankshaft 4, a crank pin 13 that connects a connecting rod 12 to the crankshaft 4, the intake camshaft 31, the exhaust camshaft 34, the rocker arms 41 and 43, an intake camshaft journal 47, and an exhaust camshaft journal 48.

[0032] The oil pan 51 is formed of a case that stores the oil returned from the lubricated portions 10, and fixed to the bottom of the engine block 6. The inlet of the oil strainer 52 is immersed in the oil stored in the oil pan 51, and the oil is introduced into the oil strainer 52 through the inlet.

[0033] As shown in FIG 3, the pump mechanism 53 includes a pump body 53h, an intake pipe 53k through which the oil drawn up through the oil strainer 52 is introduced into the pump body 53h, and a discharge pipe 53t through which the oil discharged from the pump body 53h is introduced into the oil filter 54.

[0034] As shown in FIG. 1, the pump body 53h is formed of a pump that takes in oil and discharges the oil, for example, a trochoid pump or a gear pump. The pump body 53h is connected to the crankshaft 4 via a chain (not shown). The pump body 53h is not coaxial with the crankshaft 4, and is driven by the crankshaft 4 so as to rotate at the same rotational speed as the crankshaft 4. The pump body 53h may be directly connected to the crankshaft 4 without using a chain and driven by the crankshaft 4 so as to rotate at the same rotational speed as the crankshaft 4.

[0035] The oil passage portion 55 includes a plurality of oil passages 55t through which the oil purified by the oil filter 54 is supplied to the lubricated portions 10. The oil passages 55t include a passage that is formed in ati oil pipe 55p through which the pressurized oil is delivered to the lubricated portions 10, a passage that is formed in the wall of the engine block 6, for example, a main oil gallery 55m, and a passage that is formed in an oil shower pipe 55s from which the oil is emitted toward the intake camshaft 31 and the exhaust camshaft 34.

[0036] The oil passages 55t include, for example, a passage formed of an inner space so that the oil dripped from the oil pipe 55p flows through the passage, and a passage formed in the face of the wall so that the oil flows on the face of the wall of the engine block 6. [0037] The oil reflux portion 56 branches off from the oil passages 55t that provides communication between an outlet 54h of the oil filter 54 and the main oil gallery 55m. The oil reflux portion 56 includes an oil reflux pipe 56p that forms an oil reflux passage 56k which communicates with the inlet of the pump mechanism 53. The OSV 57 that opens and closes the oil reflux passage 56k is provided in the oil reflux passage 56k. The OSV 57 is fitted to the engine block 6, and the ECU 60 controls the open/closed state of the OSV 57. The OSV 57 may be fitted to a component other than the engine block 6. For example, the OSV 57 may be fitted to the pump mechanism 53.

[0038J The OSV 57 is formed of an on-off valve that has a function of opening and closing the oil reflux passage 56k. The OSV 57 is formed of, for example, a solenoid valve that is operated by an electromagnetic force.

[0039] As shown in FIGs. 1 and 4, the oil injection nozzle 58 is formed of a pipe in which the oil passages 55t is formed. The base end portion of the oil injection nozzle 58 is supported by the engine block 6 in such a manner that the tip end portion faces the piston 2. The oil injection orifice is formed in the tip end portion, and the oil that is supplied from the main oil gallery 55m to the oil passages 55t is injected from the oil injection orifice toward the piston 2.

[0040] The ECU 60 includes a start determination unit, an operation mode determination unit, a pressure comparison unit, an oil supply control unit and an injection timing control unit. These units continuously execute controls according to a single program or multiple programs. The ECU 60 is formed of a CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), an EE PROM (Electrically Erasable and Programmable Read Only Memory), an input interface circuit including an A/D converter and a buffer, and an output interface circuit including a drive circuit. The ROM stores programs according to which the start determination unit, the operation mode determination unit, the pressure comparison unit, the oil supply control unit, and the injection timing control unit execute controls. The RAM temporarily stores the data. The EEPROM is formed of nonvolatile memory that operates using a battery as a-power source and that is rewritable. [0041] Sensors such as the coolant temperature sensor 61, the oil pressure sensor 62, a crank position sensor 63, a throttle valve opening amount sensor (not shown), an intake air amount sensor (not shown), and an accelerator position sensor (not shown) are connected to the input interface circuit of the ECU 60, and the information output from these sensors is input in the ECU 60 via the input interface circuit.

[0042] The ECU 60 obtains the engine speed Ne (rpm) based on the information received from a sensor that detects the rotational speed (rpm) of the crankshaft 4, for example, the crank position sensor 63. The opening/closing timing of each of the intake valve 42 and the exhaust valve 44 is controlled by the variable valve timing mechanism 3 mounted in the engine 1 based on the information concerning the output from the engine 1, which is detected by the throttle valve opening amount sensor, the intake air amount sensor, the accelerator position sensor, the crank position sensor 63, etc.

[0043] The coolant temperature sensor 61 includes, for example, a thermistor that has excellent temperature characteristics. The thermistor is connected to the ECU 60, detects a resistance value corresponding to the temperature of the coolant that cools the engine 1 , and inputs a voltage signal into the input interface circuit of the ECU 60. The coolant temperature sensor 61 is provided in the engine block 6 at a portion near the cylinder so as to detect the temperature of the coolant that has flowed near the cylinder of the engine block 6 and that has been warmed.

[0044] The oil pressure sensor 62 includes, for example, a semiconductor piezoresistance that has high sensitivity. The semiconductor piezoresistance is connected to the ECU 60, detects a resistance value corresponding to the pressure in the oil passage portion 55, and inputs a voltage signal into the input interface circuit of the ECU 60. The oil pressure sensor 62 is provided in the oil passage 55t at a position upstream of the variable valve timing mechanism 3, and detects the pressure (kPa) of the oil that is supplied to the intake-side oil pressure controller 33 and the exhaust-side oil pressure controller 36.

[0045] The crank position sensor 63 includes, for example, a timing rotor fixed to the crankshaft 4 and an electromagnetic pick up sensor. The crank position sensor 63 is fixed to the engine block 6. The crank position sensor 63 detects the rotation state of the crankshaft 4 such as the position and the angular speed of the crankshaft 4, and outputs a signal indicating the detected rotation state to the ECU 60.

[0046] The start determination unit of the ECU 60 determines whether the engine 1 has been started based on the information indicating whether a starter switch for actuating a starter motor for the engine 1 is turned on or the information indicating whether the time that has elapsed after the starter switch is turned off is shorter than the predetermined time. Whether the engine 1 has been started may be determined based on whether the engine speed Ne (rpm) detected by the crank position sensor 63 is equal to or higher than the predetermined rotational speed (rpm) or whether the pressure (kPa) of the oil in the oil supply passage of the engine 1 is equal to or higher than a predetermined pressure (kPa).

[0047] If the start determination unit determines that the engine 1 has been started, the operation mode determination unit of the ECU 60 determines whether the engine 1 is in the cold operation mode. More specifically, the coolant temperature sensor 61 shown in FIG. 1 detects the temperature of the coolant that flows from the oil passage 55t at a portion near the piston 2 toward the cooling device 7. The detected temperature (⁰C) and the preset temperature ("C) stored in the memory of the ECU 60, for example, the ROM are compared with each other. If the detected temperature (⁰C) is lower than the preset temperature (⁰C), it is determined that the engine 1 is in the cold operation mode. The preset temperature varies depending on the vehicle characteristics such as the vehicle specifications, for example, whether the vehicle specification is the cold area specification or the warm area specification, the types of fuel, and the engine displacements. The preset temperature is set based on the vehicle characteristics and according to the obtained data. In the vehicle according to the first embodiment, the preset temperature is, for example, approximately 88 ⁰C.

[0048] The pressure comparison unit of the ECU 60 compares the pressure (kPa) of the oil in the oil passage 55t detected by the oil pressure sensor 62 with the preset lower limit operation pressure (kPa), which is the lower limit of the pressure for operating the variable valve timing mechanism 3 and which is stored in the memory of the ECU 60, for example, the ROM. The preset lower limit operation pressure (kPa) varies depending on the vehicle characteristics, as in the case of the preset temperature. In the vehicle according to the first embodiment, the preset lower limit operation pressure is, for example, approximately 120 kPa.

[0049] If the operation mode determination unit determines that the engine 1 is in the cold operation mode, the oil supply control unit of the ECU 60 opens the OSV 57 to return part of the oil flowing through the oil passage 55t to the pump mechanism 53 through the oil reflux passage 56k.

[0050] The injection timing control unit of the ECU 60 controls the injection timing for the fuel that is injected from the fuel injection device (not shown) based on the operation mode of the engine 1. More specifically, the injection timing control unit advances or retards the fuel injection start timing and the fuel injection end timing based on the predetermined crank angle obtained from the information detected by the crank position sensor 63. As a result, an increase in flexibility of the air-fuel ratio control and a decrease in exhaust emissions are promoted, and the optimum torque and output from the engine 1 are obtained.

[0051] The engine block 6 is formed by fastening the cylinder head and cylinder block that define the cylinder including a combustion chamber 6a (see FIG 4) to the crankcase with fastening elements, for example, bolts. The engine block 6 is mounted in a vehicle body via a plurality of engine mounts (not shown).

[0052] As shown in FIG 1, the cooling device 7 includes a radiator 7a that cools the high-temperature coolant, which flows into the cooling device 7, with the use of the low-temperature outside air, an upper pipe 7b through which the cooled coolant is introduced from the radiator 7a into the engine block 6, a lower pipe 7c through which the coolant is introduced from the engine block 6 into the radiator 7a, and a water jacket 7w, shown in FIG 4, provided in the engine block 6 so that the coolant flows in the engine block 6.

[0053] The cooling device 7 further includes a water pump 7p, a bypass pipe 7d that connects the upper pipe 7b and the lower pipe 7c to each other, and a thermostat 7t that is provided at a portion at which the bypass pipe 7d branches off from the upper pipe 7b.

[0054] The coolant in the cooling device 7 is cooled in the radiator 7a, flows through the upper pipe 7b into the water jacket 7w in the engine block 6, flows through the coolant passage in the engine block 6, and is returned to the radiator 7a through the lower pipe 7c.

[0055] The thermostat 7t detects the temperature of the coolant that flows into the water jacket 7w, and switches the mode between the mode where the coolant is circulated through the radiator 7a and the mode where the coolant is circulated without flowing through the radiator 7a depending on whether the temperature of the coolant is equal to or higher than the preset temperature, that is, based on the temperature of the coolant. For example, when the temperature of the coolant is lower than 80 ⁰C, the thermostat 7t selects the mode where the coolant is circulated without flowing through the radiator 7a. That is, communication is provided between the upper pipe 7b and the bypass pipe 7d, and the coolant flows from the lower pipe 7c into the water jacket 7w. In this case, the water pump 7p is actuated by the ECU 60, the coolant is circulated through the water jacket 7w, the upper pipe 7b, the bypass pipe 7d and the lower pipe 7c, and warming-up of the engine 1 that is performed when the engine 1 is cold is promoted.

[0056] On the other hand, if the temperature of the coolant is equal to or higher than 80 ⁰C, the thermostat 7t selects the mode where the coolant is circulated through the radiator 7a. In this case, communication is provided between the upper pipe 7b and the radiator 7a, and the mode where the coolant does not flow through the bypass pipe 7d, that is, the mode where the coolant flows through the radiator 7a is selected. Then, the coolant is cooled in the radiator 7a, flows through the upper pipe 7b into the water jacket 7w, and returned to the radiator 7a through the lower pipe 7c. Thus, the engine 1 is appropriately cooled.

[0057] The fuel injection device includes an injector that is provided in the engine block 6 in such a manner that the fuel injection nozzle extends into the cylinder. The fuel injection device injects high-pressure fuel into the combustion chamber 6a, and cause efficient combustion of the air-fuel mixture with a smallest possible amount of fuel. The fuel injection device advances or retards the fuel injection timing according to a command from the injection timing control unit of the ECU 60.

[0058] Next, the routine of the oil supply control executed by the oil supply control apparatus 5 according to the first embodiment will be described. FIG. 5 is a flowchart illustrating the routine of the oil supply control executed by the oil supply control apparatus 5. FIG 6 is a graph showing the oil pressure in the main oil gallery with respect to the engine speed Ne. FIG. 7 is a graph showing the relationship between the elapsed time, and the open/closed state of the OSV, the temperature of the piston, and the injection timing when the engine is in the cold operation mode.

[0059] The flowchart shown in FIG. 5 shows the routine of the oil supply control program stored in the ROM of the ECU 60. The flowchart in FIG. 5 includes a single program or multiple programs according to which the functions of the start determination unit, the operation mode determination unit, the pressure comparison unit, the oil supply control unit, and the injection timing control unit are implemented. The oil supply control program is executed by the CPU of the ECU 60.

[0060] As shown in FIG 5, the ECU 60 determines that the engine 1 has been started if it is determined that the starter switch for actuating the starter motor for the engine 1 is turned on or it is determined that the time that has elapsed after the starter switch is turned off is shorter than the predetermined time (step 1 (hereinafter, step will be referred to as "S")). If it is determined that the starter switch is not turned on and it is determined that the time that has elapsed after the starter switch is turned off is equal to or longer than the predetermined time, the ECU 60 monitors the on/off state of the starter switch at predetermined time intervals until it is determined that the engine 1 has been started.

[0061] If an affirmative determination is made in Sl ("YES" in Sl), the ECU 60 receives a signal indicating the temperature (⁰C) detected by the coolant temperature sensor 61 shown in FIG 1 (S2), and compares the detected temperature with the preset temperature (⁰C) stored in the ROM in advance. If the detected temperature is lower than the preset temperature, for example, 88 ⁰C, the ECU 60 determines that the engine 1 is in the cold operation mode (S3).

[0062] If an affirmative determination is made in S3 ("YES" in S3), the ECU 60 receives a signal indicating the pressure (kPa) detected by the oil pressure sensor 62 shown in FIG 1 (S4), and compares the detected pressure (kPa) with the preset lower limit operation pressure (kPa), which is the lower limit of the pressure for operating the variable valve timing mechanism 3 and which is stored in the ROM in advance (S5).

[0063] If the detected pressure exceeds the preset lower limit operation pressure, for example, if the detected pressure exceeds 120 kPa, the OSV 57 is opened (S6). If the OSV 57 is opened, the pressure (kPa) of the oil discharged from the pump mechanism 53 shown in FIG 3 decreases, and, for example, the pressure of the oil in the main oil gallery 55m becomes equal to or lower than 210 kPa. Therefore, oil injection from the oil injection nozzle 58 shown in FIGs. 1 and 4 is stopped. If the engine speed Ne (rpm) increases and enters, for example, the range from 3200 rpm to 4000 rpm, the pressure of the oil discharged from the pump mechanism 53 is gradually increased in proportion to the engine speed Ne, and the oil pressure exceeds 210 kPa. However, when the engine 1 is in the cold operation mode, the oil injected from the oil injection nozzle 58 does not reach the piston 2.

[0064] As described above, only when the oil pressure exceeds the preset lower limit operation pressure, the OSV 57 is opened. Therefore, a higher priority is given to the control executed by the variable valve timing mechanism 3 than to the oil supply control executed by the oil supply control apparatus 5 according to the first embodiment. Therefore, the control executed by the variable valve timing mechanism 3 is not hindered. At the same time that the OSV 57 is opened, the ECU 60 suspends the control for retarding the injection timing, which is executed by the variable valve timing mechanism 3 (S7). If the control for retarding the injection timing is not being executed, the current control state of the variable valve timing mechanism 3 is maintained so that the control for retarding the injection timing is not executed.

[0065] Next, the ECU 60 receives a signal indicating the temperature (⁰C) detected by the coolant temperature sensor 61, and compares the detected temperature with the preset temperature of 88 ⁰C stored in the ROM in advance. If the detected temperature exceeds 88 ⁰C, the ECU 60 determines that the engine 1 has been shifted from the cold operation mode to the warm operation mode (S9).

[0066] If a negative determination is made in S9 ("NO" in S9), the ECU 60 monitors whether the engine 1 has been shifted from the cold operation mode to the warm operation mode until it is determined that the temperature detected by the coolant temperature sensor 61 exceeds 88 ⁰C. If an affirmative determination is made in S9 ("YES" in S9) or a negative determination is made S3 or S5 ("NO" in S3 or S5), the OSV 57 is closed (SlO). At this time, the ECU 60 cancels suspension of the control for retarding the injection timing, which is executed by the variable valve tuning mechanism 3 (Sl 1 ), and causes the variable valve timing mechanism 3 to execute the original control.

[0067] That is, as shown in FIG 6, in the period from when the ECU 60 determines in S3 that the engine 1 is in the cold operation mode until when the ECU 60 determines in S9 that the engine 1 is in the warm operation mode, the OSV is kept open and the oil injection from the oil injection nozzle is suspended. In this period, the ECU 60 suspends the control for retarding the injection timing, which is executed by the variable valve timing mechanism 3, and the injection timing is adjusted to the optimum injection timing.

[0068] Next, the ECU 60 determines whether the engine 1 has been stopped based on a signal output from the crank position sensor 63. If it is determined that the engine 1 has been stopped, the ECU 60 ends the oil supply control executed by the oil supply control apparatus 5 according to the first embodiment (S 12). If a negative determination is made in S12 ("NO" in S 12), the ECU 60 re-executes S2 in which the temperature of the coolant for the engine 1 is detected by the coolant temperature sensor 61.

[0069] Because the oil supply control apparatus 5 according to the first embodiment is configured as described above, the following effects are obtained.

[0070] FIG. 8 is a graph showing the relationship between the elapsed time, and the open/closed state of the OSV, the coolant temperature and the oil temperature when the engine is in the cold operation mode. FIG. 9 is a graph showing the relationship between the time that has elapsed after the engine 1 is started, and the concentration of the PM and smoke in the exhaust gas and the engine speed Ne.

[0071] The oil supply control apparatus 5 according to the first embodiment includes the oil pan 51, the pump mechanism 53 that supplies the oil in the oil pan 51 to the lubricated portions 10, the ECU 60 that controls the supply of oil, the oil injection nozzle 58, the oil reflux portion 56 that includes the oil reflux passage 56k, and the OSV 57. The ECU 60 includes the operation mode determination unit that determines whether the engine 1 is in the cold operation mode, and the oil supply control unit. If operation mode determination unit determines that the engine 1 is in the cold operation mode, the oil supply control unit opens the OSV 57 so that part of the oil flowing through the oil passage 55t is returned to the pump mechanism 53 through the oil reflux passage 56k.

[0072] As a result, when the engine 1 is in the cold operation mode, part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56. Therefore, the pressure of the oil in the oil passage 55t and the main oil gallery 55m is decreased. If the oil pressure is decreased, oil injection from the oil injection nozzle 58 toward the piston 2 is stopped, and cooling of the piston 2 by the oil is stopped.

[0073] In this case, as shown in FIG. 7, because the piston 2 is not cooled by the oil, when the engine 1 is in the cold operation mode, the temperature (⁰C) of the piston 2 becomes higher than that in the related art indicated by a dashed line. Accordingly, vaporization of the fuel supplied into the combustion chamber 6a surrounded by the piston 2 and the engine block 6 is promoted, and the problem that the fuel adheres to the top face of the piston 2 does not occur, unlike the related art.

[0074] Because part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56, the amount of oil that is supplied into the engine 1 is decreased, and the amount of heat that is transferred from the warmed coolant is decreased. As a result, as shown in FIG. 8, the amount of increase in the temperature (⁰C) of the oil in the engine 1 becomes smaller than that in the related art. However, the temperature (⁰C) of the coolant is made higher than that in the related art by applying the heat, which is supposed to be applied to the oil, to the coolant. As a result, warming-up of the engine 1 that is performed when the engine 1 is cold is promoted.

[0075] Because vaporization of the fuel is promoted, the air-fuel mixture in which the proportion between the air and the fuel is even is formed and the optimum air-fuel ratio is achieved. Therefore, the air-fuel mixture is completely burned at the appropriate combustion temperature. Especially in the direct-injection engine in which the fuel is directly injected into the combustion chamber and the fuel is ignited, the effects described above are prominent

[0076] In this case, as shown in FIG 9, it is possible to produce the effect of decreasing the amount of HC contained in the exhaust gas and the amount of PM and smoke that contain so-called SOF (Soluble Organic Fraction) because the air-fuel mixture is burned completely. In addition, the fuel consumption rate (g / KWh: g denotes the weight of the fuel, KW denotes the output, and h denotes time) is increased. Therefore, it is possible to produce the effect of increasing the so-called fuel efficiency.

[0077] In addition, the power (w) of the pump mechanism 53, which is expressed by "discharge rate (mm³ / sec) x pressure (kPa), decreases. That is, because part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56, the pressure (kPa) of the oil that is discharged from the pump mechanism 53 is decreased and the power (w) of the pump mechanism 53 decreases. In this case, because the load on the pump mechanism 53 connected to the crankshaft 4 is decreased, the friction of the crankshaft 4 is decreased and the load on the engine 1 is decreased. As a result, the so-called fuel efficiency is increased.

[0078] In the oil supply control apparatus 5 according to the first embodiment, with the simple structure in which the oil reflux portion 56 that branches off from the oil passage 55t is provided and the OSV 57 is provided in the oil reflux portion 56 and the simple control, it is possible to decrease the amount of PM and smoke in the exhaust gas that is discharged from the engine 1 when the engine 1 is in the cold operation mode. [0079J The engine 1 is provided with the radiator 7a that cools the engine 1 using the coolant, and includes the coolant temperature sensor 61 that detects the temperature of the coolant. The ECU 60 determines that the engine 1 is in the cold operation mode when the coolant temperature detected by the coolant temperature sensor 61 is lower than the preset temperature of 88 ⁰C. Therefore, it is easily determined whether the engine 1 is in the cold operation mode with a simple determination step.

[0080] Even if the engine 1 includes the variable valve timing mechanism 3 that may adjust the opening/closing timing of at least one of the intake valve 42 and the exhaust valve 44 using the oil pressure, the control executed by the variable valve timing mechanism 3 is not hindered. That is, in the engine 1, the ECU 60 compares the oil pressure in the oil passage 55t that is detected by the oil pressure sensor 62 with the preset lower limit operation pressure (kPa) that is the lower limit of the pressure for operating the variable valve timing mechanism 3. If the ECU 60 determines that the detected pressure is lower than the preset lower limit operation pressure, the ECU 60 closes the OSV 57. In this way, a higher priority is given to the control executed by the variable valve timing mechanism 3 than to the oil supply control.

[0081] When the OSV 57 is opened, the ECU 60 suspends execution of the control for retarding the fuel injection timing and executes the control for optimizing the fuel injection timing. As shown in FIG 7, when the control for retarding the fuel injection timing is suspended, the fuel injection timing is maintained at the optimum fuel injection timing as indicated by a heavy solid line. Therefore, the situation where the fuel injection amount is increased as the fuel injection timing is retarded does not occur, unlike the related art. Therefore, the fuel consumption rate decreases. As a result, deterioration of the so-called fuel efficiency does not occur. In addition, it is possible to avoid the situation where the fuel combustion period is prolonged as the fuel injection timing is retarded, combustion takes place more slowly, and the effective output from the engine becomes unstable. Furthermore, it is no longer necessary to execute the valve opening/closing timing control and the injection timing retardation control in combination. Therefore, it is possible to suppress complication of the controls. [0082] Also, as shown in FIQ 6, the OSV 57 is kept open by the ECU 60 until the cold operation mode ends. When the cold operation mode ends, the operation mode is switched from the cold operation mode to the warm operation mode. At the same time that the operation mode is switched .to the warm operation mode, suspension of the control for retarding the fuel injection timing is promptly cancelled, and the OSV 57 is closed. Therefore, the oil is injected from the oil injection nozzle 58 toward the piston 2, and the piston 2 is appropriately cooled and lubricated.

[00831 In the description above, the pump mechanism 53 of the oil supply control apparatus 5 according to the first embodiment is connected to the crankshaft 4, the pump mechanism 53 is driven by the power from the engine 1, and the oil reflux passage 56k through which the oil is returned from the oil passage 55t to the pump mechanism 53 is formed. In the description above, when the engine 1 is in the cold operation mode, the OSV 57 provided in the oil reflux passage 56k is opened so that the oil injection from the oil injection nozzle is stopped.

[0084] However, the pump mechanism of the oil supply control apparatus according to the invention may have another structure. For example, the pump mechanism may be formed of a variable capacity oil pump. When the engine 1 is in the cold operation mode, the capacity of the pump mechanism may be decreased to stop the oil injection from the oil injection nozzle. Alternatively, the pump mechanism may be formed of an electric oil pump. When the engine 1 is in the cold operation mode, the discharge rate of the pump mechanism may be decreased to stop the oil injection from the oil injection nozzle. Further alternatively, the pump mechanism may be formed of a large-capacity pump mechanism and a small-capacity pump mechanism. When the engine 1 is in the cold operation mode, the small-capacity pump mechanism may be selected to stop the oil injection from the oil injection nozzle.

(0085] In the description above, in the oil supply control apparatus 5 according to the first embodiment, when the ECU 60 determines whether the engine 1 is in the cold operation mode, the ECU 60 compares the temperature (⁰C) detected by the coolant temperature sensor 61 with the preset temperature (⁰C). If the detected temperature (⁰C) is lower than the preset temperature (⁰C), it is determined that the engine 1 is in the cold operation mode. However, in the oil supply control apparatus according to the invention, whether the engine is in the cold operation mode may be determined in another method. For example, whether the engine is in the cold operation mode may be determined based on the temperature detected by the oil temperature sensor and the idling speed (rpm) of the engine.

[0086] FIG. 10 is a perspective view schematically showing a vehicle engine to which an oil supply control apparatus according to a second embodiment of the invention is applied. FIG 11 is a block diagram showing lubricated portions and oil flows in the engine. FIG. 12 is a flowchart illustrating the routine of the oil supply control executed by the oil supply control apparatus.

[0087] An oil supply control apparatus 105 according to the second embodiment differs from the oil supply control apparatus 5 according to the first embodiment in that a valve mechanism 103 is provide^'d instead of the variable valve timing mechanism 3. The other configurations of the oil supply control apparatus 105 are the same as those of the oil supply control apparatus 5. Therefore, the same reference numerals as those in the first embodiment shown in FIGs. 1 to 9 are used to denote the same configurations, and only the differences will be described below.

[0088] First, the structure of an engine 100 will be described. As shown in FIG 10, the structure of the engine 100 is similar to that of the engine 1 in the first embodiment. The engine 100 includes the piston 2 housed in the cylinder, the valve mechanism 103, the crankshaft 4, the oil supply control apparatus 105, the engine block 6 formed of the cylinder head, the cylinder block and the crankcase, the cooling device 7 that cools the inside of the engine 1, and the fuel injection device that injects the fuel directly into the cylinder.

[0089] The valve mechanism 103 includes an intake camshaft 131 and an exhaust camshaft 134. The intake camshaft 131 and the exhaust camshaft 134 are connected to the crankshaft 4 via the chain 37, and driven by the power from the crankshaft 4. The intake valve 42 is connected to the intake camshaft 131 via the rocker arm 41, and the exhaust valve 44 is connected to the exhaust camshaft 134 via the rocker arm 43.

[0090] The structure of the oil supply control apparatus 105 is similar to the structure of the oil supply control apparatus 5 according to the first embodiment. The oil supply control apparatus 105 includes the oil pan 51, the oil strainer 52, the pump mechanism 53, the oil filter 54 that filters the oil discharged from the pump mechanism 53, the oil passage portion 55, the oil reflux portion 56, the OSV 57, the oil injection nozzle 58, the stop valve 59 that regulates the flow rate of the oil that flows through the pump mechanism 53 (see FIG 11), an ECU 160, and the coolant temperature sensor 61. The oil supply control apparatus 105 supplies the oil to lubricated portions 110 in the engine 100 to lubricate and cools the lubricated portions 110.

[0091] The lubricated portions 10 are components that are provided in the engine 100 and that need to be lubricated. As shown in FIG 11, the lubricated portions 110, as well as the lubricated portions 10 in the first embodiment, include, for example, the piston 2, the crankshaft journal 11 that rotatably supports the crankshaft 4, the crank pin 13 that connects the connecting rod 12 to the crankshaft 4, the intake camshaft 131, the exhaust camshaft 134, the rocker arms 41 and 43, the intake camshaft journal 47, and the exhaust camshaft journal 48.

[0092] The ECU 160 includes the start determination unit, the operation mode determination unit, and the oil supply control unit. These units continuously execute controls according to a single program or multiple programs. The ECU 160, as well as the ECU 60 in the first embodiment, is formed of the CPU, the ROM, the RAM, the EE PROM, the input interface circuit including the A/D converter and the buffer, and the output interface circuit including the drive circuit. The ROM stores programs according to which the start determination unit, the operation mode determination unit, and the oil supply control unit execute controls. The RAM temporarily stores the data. The EEPROM is formed of the nonvolatile memory that operates using the battery as a power source and that is rewritable.

[0093] Sensors such as the coolant temperature sensor 61, the crank position sensor 63, the throttle valve opening amount sensor (not shown), the intake air amount sensor (not shown), and the accelerator position sensor (not shown) are connected to the input interface circuit of the ECU 160, and the information output from these sensors is input in the ECU 160 via the input interface circuit. The ECU 160 obtains the engine speed Ne (rpm) based on the information received from the sensor that detects the rotational speed (rpm) of the crankshaft 4, for example, the crank position sensor 63.

[0094J Next, the routine of the oil supply control executed by the oil supply control apparatus 105 according to the second embodiment will be described. FIG 12 is a flowchart illustrating the routine of the oil supply control executed by the oil supply control apparatus 105.

[0095] The flowchart shown in FIG 12 shows the routine of the oil supply control program stored in the ROM of the ECU 160. The oil supply control program illustrated in flowchart in FIG 12, as well as the oil supply control program stored in ROM of the ECU 60 in the first embodiment, includes a single program or multiple programs according to which the functions of the start determination unit, the operation mode determination unit, and the oil supply control unit are implemented. The oil supply control program is executed by the CPU of the ECU 160.

[0096] As shown in FIG 12, the ECU 160, as well as the ECU 60 in the first embodiment, determines that the engine 100 has been started when it is determined that the starter switch for actuating the starter motor of the engine 100 is turned on or it is determined that the time that has elapsed after the starter switch is turned off is shorter than the predetermined time. (SlOl). If it is determined that the starter switch is not turned on and it is determined that the time that has elapsed after the starter switch is turned off is equal to or longer than the predetermined time, the ECU 160 monitors the on/off state of the starter switch at predetermined time intervals until it is determined that the engine 100 has been started.

[009η If an affirmative determination is made in SlOl ("YES" in SlOl), the ECU 160 receives a signal indicating the temperature (⁰C) detected by the coolant temperature sensor 61 shown in FIG. 10 (S 102), and compares the detected temperature with the preset temperature (⁰C) stored in the ROM in advance. If the detected temperature is lower than the preset temperature, for example, 88 ⁰C, the ECU 160 determines that the engine 1 is in the cold operation mode (S 103).

[0098J If an affirmative determination is made in S 103 ("YES" in S 103), the ECU 160 opens the OSV 57 (S104). If the OSV 57 is opened, the pressure (kPa) of the oil discharged from the pump mechanism 53 shown in FIQ 3 decreases as in the first embodiment, and, for example, the pressure of the oil in the main oil gallery 55m becomes equal to or lower than 210 kPa as shown in FIG 6. Therefore, the oil injection from the oil injection nozzle 58 shown in FIGs. 1 and 4 is stopped. As in the first embodiment, if the engine speed Ne (rpm) increases and enters, for example, the range from 3200 rpm to 4000 rpm, the pressure of the oil discharged from the pump mechanism 53 is gradually increased in proportion to the engine speed Ne, and the oil pressure exceeds 210 kPa. However, when the engine 1 is in the cold operation mode, the oil injected from the oil injection nozzle 58 does not reach the piston 2.

[0099] Next, the ECU 160 receives a signal indicating the temperature (⁰C) detected by the coolant temperature sensor 61 (S 105), and compares the detected temperature with the preset temperature of 88 ⁰C stored in the ROM in advance. If the detected temperature exceeds 88 ⁰C, the ECU 160 determines that the engine 100 has been shifted from the cold operation mode to the warm operation mode (S 106).

[0100] If a negative determination is made in S106 ("NO" in S106), the ECU 160 monitors whether the engine 100 has been shifted from the cold operation mode to the warm operation mode until it is determined that the temperature detected by the coolant temperature sensor 61 exceeds 88 ⁰C. If an affirmative determination is made in S 106 ("YES" in S106) or a negative determination is made in S103 ("NO" in S103), the OSV 57 is closed (S 107).

[0101] Next, the ECU 160 determines whether the engine 100 has been stopped. If it is determined that the engine 100 has been stopped, the ECU 160 ends the oil supply control executed by the oil supply control apparatus 105 in the second embodiment (S 108). If a negative determination is made in S 108 ("NO" in S 108), the ECU 160 executes S 102 in which the ECU 160 receives a signal indicating the coolant temperature detected by the coolant temperature sensor 61 of the engine 100.

[0102] Because the oil supply control apparatus 105 according to the second embodiment is configured as described above, the following effects are obtained.

[0103] The oil supply control apparatus 105 according to the second embodiment, as well as the oil supply control apparatus 5 according to the first embodiment, includes the oil pan 51, the pump mechanism 53 that supplies the oil in the oil pan 51 to the lubricated portions 110, the ECU 160 that controls the supply of oil, the oil injection nozzle 58, the oil reflux portion 56 that includes the oil reflux passage 56k, and the OSV 57. The ECU 160 includes the operation mode determination unit that determines whether the engine 100 is in the cold operation mode, and the oil supply control unit If operation mode determination unit determines that the engine 100 is in the cold operation mode, the oil supply control unit opens the OSV 57 so that part of the oil flowing through the oil passage 55t is returned to the pump mechanism 53 through the oil reflux passage 56k.

[0104] As a result, as in the first embodiment, when the engine 100 is in the cold operation mode, part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56. Therefore, the pressure of the oil in the oil passage 55t and the main oil gallery 55m is decreased. If the oil pressure is decreased, the oil injection from the oil injection nozzle 58 toward the piston 2 is stopped, and cooling of the piston 2 by the oil is stopped.

[0105] In this case, as shown in FIG 7, because the piston 2 is not cooled by the oil, when the engine 100 is in the cold operation mode, the temperature (⁰C) of the piston 2 becomes higher than that in the related art indicated by a dashed line. Accordingly, vaporization of the fuel supplied into the combustion chamber surrounded by the piston 2 and the engine block 6 is promoted, and the problem that the fuel adheres to the top face of the piston 2 does not occur, unlike the related art.

[0106] Because part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56, the amount of oil that is supplied into the engine 100 is decreased and the amount of heat that is transferred from the warmed coolant is decreased. As a result, as shown in FIG 8, the amount of increase in the temperature (⁰C) of the oil in the engine 100 becomes smaller than that in the related art. However, the temperature (⁰C) of the coolant is made higher than that in the related art by applying the heat, which is supposed to be applied to the oil, to the coolant. As a result, warming-up of the engine 100 that is performed when the engine 100 is cold is promoted.

[0107] Because vaporization of the fuel is promoted, the air-fuel mixture in which the proportion between the air and the fuel is even is formed and the optimum air-fuel ratio is achieved. Therefore, the air-fuel mixture is completely burned at the appropriate combustion temperature. Especially in the direct-injection engine in which the fuel is directly injected into the combustion chamber and the fuel is ignited, the effects described above are prominent.

[0108] In this case, as shown in FIG 9, it is possible to produce the effect of decreasing the amount of HC contained in the exhaust gas and the amount of PM and smoke that contain so-called SOF (Soluble Organic Fraction) because the air-fuel mixture is burned completely, as in the first embodiment. In addition, the fuel consumption rate (g / KWh: g denotes the weight of the fuel, KW denotes the output, and h denotes time) is increased. Therefore, it is possible to produce the effect of increasing the so-called fuel efficiency.

[0109] In addition, the power (w) of the pump mechanism 53, which is expressed by "discharge rate (mm³ / sec) x pressure (kPa), decreases. That is, because part of the oil discharged from the pump mechanism 53 is returned to the pump mechanism 53 through the oil reflux portion 56, the pressure (kPa) of the oil that is discharged from the pump mechanism 53 is decreased and the power (w) of the pump mechanism 53 decreases. In this case, because the load on the pump mechanism 53 connected to the crankshaft 4 is decreased, the friction of the crankshaft 4 is decreased and the load on the engine 1 is decreased. As a result, the so-called fuel efficiency is increased. In the oil supply control apparatus 105 according to the second embodiment, with the simple structure in which the oil reflux portion 56 that branches off from the oil passage 55t is provided and the OSV 57 is provided in the oil reflux portion 56 and the simple control, it is possible to decrease the amount of PM and smoke in the exhaust gas that is discharged from the engine 100 when the engine 100 is in the cold operation mode.

[0110] As in the first embodiment, the engine 100 is provided with the radiator 7a that cools the engine 100 using the coolant, and includes the coolant temperature sensor 61 that detects the temperature of the coolant. The ECU 160 determines that the engine 100 is in the cold operation mode when the coolant temperature detected by the coolant temperature sensor 61 is lower than the preset temperature of 88 ⁰C. Therefore, it is easily determined whether the engine 100 is in the cold operation mode with a simple determination step,

[0111] Also, as shown in FIG 6, the OSV 57 is kept open by the ECU 160 until the cold operation mode ends. When the cold operation mode ends, the operation mode is switched from the cold operation mode to the warm operation mode. At the same time that the operation mode is switched to the warm operation mode, the OSV 57 is closed. Therefore, the oil is injected from the oil injection nozzle 58 toward the piston 2, and the piston 2 is appropriately cooled and lubricated.

[0112] As described above, the oil supply control apparatus according to the invention produces the effect of decreasing the amount of PM and smoke in the exhaust gas by suppressing cooling of the engine by the oil with a simple control when the engine is in the cold operation mode, and supplies oil to the lubricated portions of the engine to lubricate the lubricated portions.

Claims

CLAIMS:

1. An oil supply control apparatus, characterized by comprising: an oil pan that stores oil; a pump mechanism that supplies the oil stored in the oil pan to lubricated portions that include a piston of an engine through an oil passage; an oil injection nozzle that injects the oil in the oil passage toward the piston; an oil reflux portion that branches off from the oil passage which leads to the oil injection nozzle and that includes an oil reflux passage through which part of the oil in the oil passage is returned to the pump mechanism; an oil switch valve that is provided in the oil reflux portion and that opens and closes the oil reflux passage; an oil supply control unit that controls supply of the oil; and an operation mode determination unit that determines whether the engine is in a cold operation mode, wherein when the operation mode determination unit determines that the engine is in the cold operation mode, the oil supply control unit opens the oil switch valve so that part of the oil that flows through the oil passage is returned to the pump mechanism through the oil reflux passage.

2. The oil supply control apparatus according claim 1, wherein: the engine is provided with a cooling device that cools the engine using a coolant, and includes a coolant temperature sensor that detects a temperature of the coolant; and when the temperature of the coolant detected by the coolant temperature sensor is lower than a preset temperature, the operation mode determination unit determines that the engine is in the cold operation mode.

3. The oil supply control apparatus according claim 1 , further comprising: an oil temperature detection sensor that detects a temperature of the oil, wherein the operation mode determination unit determines whether the engine is in the cold operation mode based on the temperature of the oil detected by the oil temperature detection sensor and an idling speed of the engine.

4. The oil supply control apparatus according to any one of claims 1 to 3, wherein: the engine includes a variable valve timing mechanism that adjusts opening/closing timing of at least one of an intake valve and an exhaust valve using a pressure of the oil; the oil supply control apparatus further includes an oil pressure sensor that detects the pressure of the oil in the oil passage, and a pressure comparison unit that compares the pressure of the oil detected by the oil pressure sensor with a preset lower limit operation pressure which is a lower limit of pressure for operating the variable valve timing mechanism, and when the pressure comparison unit determines that the pressure of the oil detected by the oil pressure sensor is lower than the preset lower limit operation pressure, the oil supply control unit closes the oil switch valve.

5. The oil supply control apparatus according to claim 4, wherein: the engine includes an injection timing control unit that retards fuel injection timing; and when the oil switch valve is opened, the oil supply control unit notifies the injection timing control unit that the oil switch valve is opened so that the injection timing control unit suspends a control for retarding the fuel injection timing.

6. The oil supply control apparatus according to any one of claims 1 to 3, wherein: the engine includes a variable valve timing mechanism that adjusts opening/closing timing of at least one of an intake valve and an exhaust valve using a pressure of the oil; the oil supply control apparatus further includes an oil pressure sensor that detects the pressure of the oil in the oil passage, and a pressure comparison unit that compares the pressure of the oil detected by the oil pressure sensor with a preset lower limit operation pressure which is a lower limit of pressure for operating the variable valve timing mechanism, and when the operation mode determination unit determines that the engine is in the cold operation mode and the pressure comparison unit determines that the pressure of the oil detected by the oil pressure sensor exceeds the preset lower limit operation pressure, the oil supply control unit opens the oil switch valve.

7. The oil supply control apparatus according to claim 6, wherein when the operation mode determination unit determines that the engine has been shifted from the cold operation mode to a warm operation mode, the oil supply control unit closes the oil switch valve.

8. The oil supply control apparatus according to claim 6, wherein: the engine includes an injection timing control unit that retards fuel injection timing; and when the oil switch valve is opened, the oil supply control unit notifies the injection timing control unit that the oil switch valve is opened so that the injection timing control unit suspends a control for retarding the fuel injection timing.

9. The oil supply control apparatus according to claim 8, wherein: when the operation mode determination unit determines that the engine has been shifted from the cold operation mode to a warm operation mode, the oil supply control unit closes the oil switch valve; and suspension of the control for retarding the fuel injection timing is cancelled.