JP2004293405A - Variable valve system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a system and to reduce its cost and friction by miniaturizing/reducing the capacity of an oil pump without causing degradation of actuation responsiveness. <P>SOLUTION: An inlet valve side and an exhaust valve side are respectively provided with a valve timing change mechanism (VTC) actuated by oil pressure from the oil pump for changing a valve lift characteristic. When an oil temperature Ot detected by an oil temperature sensor becomes higher than a predetermined second oil temperature threshold Ot2 (S15a), actuation of the exhaust VTC is prohibited (S16a). When the oil temperature Ot exceeds a first oil temperature threshold Ot1 which is higher than the Ot2, actuation of the inlet VTC is prohibited. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a variable valve operating device for an internal combustion engine provided with a variable valve operating on both the intake side and the exhaust side by hydraulic pressure.
[0002]
[Prior art]
2. Description of the Related Art Various variable valve mechanisms capable of changing valve lift characteristics of intake and exhaust valves have been conventionally proposed in order to improve the output and fuel efficiency of an internal combustion engine. For example, Patent Document 1 discloses a variable valve mechanism using both a hydraulic actuator and an electric actuator.
[0003]
[Patent Document 1]
JP-A-2002-161721
[Problems to be solved by the invention]
When variable valve mechanisms that change valve lift characteristics by operating with hydraulic pressure from a hydraulic source such as an oil pump are provided on both the intake side and the exhaust side, there are the following problems. In situations where the oil pressure is low (oil temperature is high), in order to ensure the responsiveness of operation of both variable valve mechanisms, the capacity and size of the oil pump must be increased, resulting in increased costs and larger equipment. I will invite you. Alternatively, when at least one of the variable valve mechanisms is electrically operated, the cost is increased, the power consumption is increased, and the variable fuel valve mechanism can sufficiently obtain the original effect of improving fuel efficiency. Can not.
[0005]
The present invention has been made in view of such a problem, and a variable valve of an internal combustion engine in which a variable valve mechanism that operates by hydraulic pressure to change a valve lift characteristic is applied to each of an intake side and an exhaust side. In equipment, it is possible to reduce the cost and fuel consumption by reducing the size and capacity of hydraulic sources such as oil pumps, while avoiding the inability to ensure the operational responsiveness of the variable valve mechanism due to a decrease in oil pressure, an increase in oil temperature, etc. It is a main object of the present invention to provide a novel variable valve operating device for an internal combustion engine that can be improved.
[0006]
[Means for Solving the Problems]
On each of the intake valve side and the exhaust valve side, there is provided a variable valve mechanism that operates by hydraulic pressure from a hydraulic pressure source and changes valve lift characteristics. A hydraulic parameter related to the hydraulic pressure is detected, and based on the hydraulic parameter, the operation of at least one of the intake-side variable valve mechanism and the exhaust-side variable valve mechanism is prohibited.
[0007]
【The invention's effect】
According to the present invention, since the operation of at least one of the variable valve mechanisms is prohibited based on the hydraulic parameters, the operation of the variable valve mechanisms can be performed without increasing the size and capacity of a hydraulic source such as an oil pump. The responsiveness can be prevented from being carelessly reduced. Therefore, it is possible to reduce the size and capacity of the hydraulic power source, reduce costs, improve fuel efficiency, and the like, without lowering the fail-safe performance.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an intake-side variable valve timing mechanism (hereinafter referred to as intake VTC) 13 as an intake-side variable valve mechanism is capable of continuously changing the valve timing of an intake valve, and has an exhaust-side variable valve mechanism. An exhaust-side variable valve timing mechanism (hereinafter, referred to as an exhaust VTC) 15 as a valve mechanism can continuously change the valve timing of the exhaust valve. These VTCs (Valve Timing Controls) themselves are known as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2002-161721, and will be described only briefly here.
[0009]
Each VTC includes a housing 43 fixed to a cam sprocket 47 that rotates in conjunction with a crankshaft, a vane 44 housed in the housing 43 and fixed to the intake camshaft 14 or the exhaust camshaft 16. have. Between the vane 44 and the housing 43, two systems of hydraulic chambers 45, 46 connected to two VTC oil supply passages 34 or 35 (34a, 34b on the intake side; 35a, 35b on the exhaust side) are liquid-tight. Is defined. In accordance with the hydraulic pressure supplied to the hydraulic chambers 45, 46, the vane 44 rotates with respect to the housing 43, the phase of the camshafts 14, 16 with respect to the phase of the crankshaft changes, and the operating angles of the intake and exhaust valves Changes to the advance side and the retard side.
[0010]
The engine control unit 1 is a known digital computer having a CPU, a ROM, a RAM, and an input / output interface, and stores and executes various control processes described later. That is, the engine control unit 1 controls the vehicle temperature signal 2, the intake air amount signal 3, the throttle sensor signal 4, the oxygen sensor signal 5, the engine rotation signal 6, the intake cam angle sensor signal 19, the exhaust cam angle sensor signal 20, and the like. Control signals are output to various actuators based on various detection signals representing the operating state, and in particular, commands are sent to an intake VTC solenoid 11 as an intake hydraulic control valve and an exhaust VTC solenoid 12 as an exhaust hydraulic control valve, respectively. An intake VTC control signal 9 and an exhaust VTC control signal 10 are output as values (amount of power). The VTC solenoids 11 and 12 control the connection state and the degree of opening of the VTC oil supply passages 34 and 35 according to the command value, and control the oil pressure supplied to the hydraulic chambers 45 and 46.
[0011]
2 and 6 schematically show hydraulic circuits of the VTCs 13 and 15. The cylinder block 41 is provided with an oil pump 31 as a hydraulic pressure source. Hydraulic oil (lubricating oil / engine oil) pressurized by the oil pump 31 passes through the block main gallery 32, the VTC solenoid oil supply passage 33, the above-described VTC solenoids 11, 12 and the VTC oil supply passages 34, 35, and then the cylinder oil. The power is supplied to the VTCs 13 and 15 provided in the head 42.
[0012]
In the first, second, and fifth embodiments to be described later, as shown in FIG. 2, the hydraulic parameters related to the hydraulic pressure are set in the middle of the hydraulic pressure supply path from the oil pump 31 to the VTC solenoids 11 and 12, for example, in the block main gallery 32. An oil temperature sensor (hydraulic parameter detection means) 24 for detecting the temperature of the hydraulic oil, that is, the oil temperature, is provided. In the third, fourth, and sixth embodiments to be described later, as shown in FIG. 6, the pressure of the hydraulic oil, that is, the hydraulic pressure is supplied to the middle of the hydraulic pressure supply path from the oil pump 31 to the VTC solenoids 11, 12, for example, to the VTC solenoid oil supply path 33. Is provided with a hydraulic pressure sensor (hydraulic parameter detecting means) 22 for detecting the pressure.
[0013]
3 to 5, 7, 8, 10, and 11 are flowcharts showing the control processing stored and executed by the engine control unit 1. Referring to FIG. 3, in S (step) 1, intake VTC switching permission flag Vi and exhaust VTC switching permission flag Ve are initialized to zero. In S2, it is determined based on mainly the engine speed and the engine load whether or not the operating region (ON region) in which the hydraulic pressure is supplied to at least one of the hydraulic chambers 45 and 46 of the intake VTC 13 to operate the intake VTC 13. If it is determined that it is in the operation region of the intake VTC 13, the process proceeds to S3, and the intake VTC switching permission flag Vi is set to 1. If it is determined that it is not in the operation range of the intake VTC 13, S3 is bypassed and Vi remains at 0. Similarly, in S4, it is determined whether or not the operating area (ON area) in which the oil pressure is supplied to at least one of the hydraulic chambers 45 and 46 of the exhaust VTC 15 to operate the exhaust VTC 15 based mainly on the engine speed and the engine load. judge. If it is determined that it is within the operation range of the exhaust VTC 13, the process proceeds to S5, and the exhaust VTC switching permission flag Ve is set to 1. If it is determined that it is not in the operation range of the exhaust VTC 15, S5 is bypassed, and Ve remains at 0.
[0014]
In S2 and S4 of FIG. 3, it is determined whether or not it is a region in which the hydraulic pressure is supplied to the VTC and the VTC is operated mainly based on a request based on the engine speed and the engine load. The effect of rising oil pressure and decreasing oil pressure is not taken into account.
[0015]
FIG. 4 is a flowchart showing the flow of control according to the first embodiment of the present invention. In S11, the values of the intake VTC switching permission flag Vi and the exhaust VTC switching permission flag Ve set by the routine of FIG. 3 are read. In S12, it is determined whether the intake VTC switching permission flag Vi is 1 or not. In S13, it is determined whether the exhaust VTC switching permission flag Ve is 1. Only when it is determined that both Vi and Ve are 1, that is, when it is in the operation region of the intake VTC 13 and in the operation region of the exhaust VTC 15, the processing after S14 is performed. To end.
[0016]
In S14, the output value Ot (the oil temperature sensor signal 23 in FIG. 1) of the oil temperature sensor 24 shown in FIG. 2 is read. In S15, it is determined whether the output value (oil temperature) Ot is in a first high oil temperature state exceeding a predetermined first oil temperature threshold Ot1 (for example, 120 to 130 ° C.). If it is determined that the state is the first high oil temperature state, the process proceeds to S16, where the value of the intake VTC switching permission flag Vi is set to 0 and the value of the exhaust VTC switching permission flag Ve is set to 0. That is, the operation of the intake VTC 13 is prohibited, and the operation of the exhaust VTC 15 is prohibited.
[0017]
According to the first embodiment, in the first high oil temperature state in which the oil temperature is high, the viscosity of the hydraulic oil decreases, and the oil pressure decreases, the operation of both the intake VTC 13 and the exhaust VTC 15, that is, the supply of the oil pressure is prohibited. are doing. Therefore, in order to guarantee the operation responsiveness of the VTC, it is possible to prevent the operation responsiveness of the VTC from being inadvertently reduced without securing an excessively large capacity of the oil pump 31, and to reduce the size of the oil pump 31. By reducing the size and the capacity, the cost can be reduced, the size of the device can be reduced, and the friction can be reduced.
[0018]
FIG. 5 is a flowchart showing a control flow according to the second embodiment of the present invention. The processes in S11 to S14 are the same as those in the first embodiment in FIG. In S15a, it is determined whether the output value (oil temperature) Ot of the oil temperature sensor 24 is in a second high oil temperature state exceeding a predetermined second oil temperature threshold Ot2. When it is determined that the state is the second high oil temperature state, the process proceeds to S16a, and the value of the exhaust VTC switching permission flag Ve is set to 0. That is, only the operation of the exhaust VTC 15 is prohibited without prohibiting the operation of the intake VTC 13.
[0019]
The operation and effect according to the second embodiment will be described with reference to FIG.
[0020]
{Circle around (1)} For example, in the partial range, the intake VTC 13 advances the intake valve opening timing IVO to increase the overlap from IVO to the exhaust valve opening timing EVO, thereby increasing the internal EGR amount and improving fuel efficiency. Aim.
[0021]
{Circle around (2)} In a low-speed range, the intake valve closing timing IVC is advanced to bring this IVC closer to the bottom dead center, thereby increasing the actual compression ratio and improving the torque.
[0022]
(3) Due to exhaust pulsation in the exhaust passage (exhaust pipe), exhaust is easier to be exhausted when exhaust pressure is low, so in a fully open area, etc., EVC is retarded to accelerate exhaust exhaust And improve the output.
[0023]
Therefore, as in the second embodiment, in the second high oil temperature state (at the time of a failure), the operation of only the exhaust VTC 15 is prohibited, so that the effects (1) and (2) by the operation of the intake VTC 13 are achieved. As in the first embodiment, the size and capacity of the oil pump 31 can be reduced while reducing costs and reducing friction.
[0024]
Since the operation of the exhaust VTC 15 is prohibited when the oil temperature is high, the output improvement effect of (3) cannot be obtained. However, at such a high oil temperature, there is little need to improve the output, and there is no practical problem.
[0025]
Referring to FIG. 9, a comparison is made between (a) a case in which valve overlap is provided by advancing intake VTC 13 and (b) a case in which valve overlap is provided by retarding exhaust VTC 15. In (a), since EGR is obtained mainly before the top dead center, it is easy to discharge EGR with the rise of the piston. Easy to pull into the cylinder.
[0026]
In a VTC operated by hydraulic pressure, there is a certain delay in response from the input of a signal to the actual operation. For this reason, for example, if the state (b) is maintained during the transition period in which a sudden brake is applied from the operation area (a) or (b) to a state (c) such as an idling area by suddenly depressing the brake, the EGR is stored in the cylinder. , The combustion tends to be unstable. On the other hand, in the state (a), combustion is relatively stable. Therefore, as in the second embodiment, the operation of only the exhaust VTC is prohibited at the time of high oil temperature, thereby suppressing and avoiding the valve overlap as shown in (b) and improving the combustion stability. can do.
[0027]
Further, by setting the second oil temperature threshold Ot2 to be lower than the first oil temperature threshold Ot1 of the first embodiment, the operating range of the VTC can be expanded, and the drivability can be improved.
[0028]
FIG. 7 is a flowchart showing a flow of control according to the third embodiment of the present invention. The processing from S11 to S14 is the same as in the first embodiment of FIG. 4 described above. In S15b, the output of the hydraulic pressure sensor 22 shown in FIG. 6 (the hydraulic pressure sensor signal 21 in FIG. 1), that is, the hydraulic pressure Op is a first low hydraulic pressure state lower than a predetermined first hydraulic pressure threshold value (for example, 100 to 150 Pa) Op1. Is determined. When it is determined that the state is the first low oil pressure state, the process proceeds to S16b, and the value of the intake VTC switching permission flag Vi and the value of the exhaust VTC switching permission flag Ve are set to 0. As a result, the operation of the intake VTC 13 is prohibited, and the operation of the exhaust VTC 15 is prohibited.
[0029]
The intake VTC and the exhaust VTC are operated by hydraulic pressure, and when the hydraulic pressure is low, the operation characteristics are deteriorated (responsiveness is slowed). As the oil temperature increases, the oil pressure decreases as the viscosity decreases. Therefore, in the above-described first and second embodiments, the oil pressure substitute characteristic is generally used in a conventional engine. The oil temperature of the oil temperature sensor is used as a parameter related to the oil pressure to reduce the number of parts and cost. On the other hand, in the third embodiment, since the oil pressure is directly detected instead of the oil temperature, which is a substitute characteristic, the control accuracy of the intake VTC and the exhaust VTC is excellent.
[0030]
FIG. 8 is a flowchart showing a control flow according to the fourth embodiment of the present invention. The processes in S11 to S14 are the same as those in the first embodiment of FIG. In S15c, it is determined whether or not the output (oil pressure) Op of the oil pressure sensor 22 is in a second low oil pressure state lower than a predetermined second oil pressure threshold value Op2. If it is determined that the state is the second low oil pressure state, the process proceeds to S16c, and only the value of the exhaust VTC switching permission flag Ve is set to 0 without changing the intake VTC switching permission flag Vi. As a result, only the operation of the exhaust VTC 15 is prohibited without prohibiting the operation of the intake VTC 13.
[0031]
According to such a fourth embodiment, the main functions and effects of the second embodiment and the third embodiment described above can be obtained together. In other words, by prohibiting the operation of only the exhaust VTC, the operation range of the intake VTC relating to the hydraulic pressure can be expanded to the limit, the operability is improved, and the combustion stability is improved as compared to the case where the operation of only the intake VTC is prohibited. The performance is improved. Further, since the hydraulic pressure can be directly detected, the control accuracy can be improved as in the third embodiment. Further, by setting the second oil pressure threshold value Op to be higher than the first oil pressure threshold value Op1 of the third embodiment, the operation range of the VTC can be expanded, and the drivability can be improved.
[0032]
FIG. 10 is a flowchart showing a control flow according to the fifth embodiment of the present invention. The processing from S11 to S16a is the same as in the second embodiment in FIG. That is, in the second high oil temperature state where the oil temperature Ot detected by the oil temperature sensor 24 is higher than the second oil temperature threshold Ot2, the process proceeds from S15a to S16a, the exhaust VTC switching permission flag Ve is set to 0, and the operation of the exhaust VTC 15 is performed. Ban. In S17, it is determined whether the oil temperature Ot is in a first high oil temperature state that exceeds a first oil temperature threshold Ot1 (Ot1> Ot2) that is higher than the second oil temperature threshold Ot2. If it is determined that the state is the first high oil temperature state, the process proceeds to S18, where the intake VTC switching permission flag Vi is set to 0, and the operation of the intake VTC 13 is prohibited.
[0033]
According to the fifth embodiment, in addition to obtaining substantially the same effects as the second embodiment, the prohibition of the operation of the exhaust VTC 15 and the prohibition of the operation of the intake VTC 13 are appropriately performed in this order in accordance with the rise in the oil temperature. Therefore, a failure state such as an inadvertent decrease in VTC operation responsiveness can be reliably avoided, a sufficient VTC operation region can be ensured, and engine operability can be improved.
[0034]
FIG. 11 is a flowchart showing a control flow according to the sixth embodiment of the present invention. The processing from S11 to S16c is the same as in the fourth embodiment in FIG. That is, in the second low oil pressure state where the oil pressure Op detected by the oil pressure sensor 22 is lower than the second oil pressure threshold value Op2, the process proceeds from S15c to S16c, the exhaust VTC switching permission flag Ve is set to 0, and the operation of the exhaust VTC 15 is prohibited. In S17a, it is determined whether the oil pressure Op is in a first low oil pressure state lower than the first oil pressure threshold value Op1 (Op1 <Op2), which is a value lower than the second oil pressure threshold value Op2. If it is determined that the state is the first low oil pressure state, the process proceeds to S18, where the intake VTC switching permission flag Vi is set to 0, and the operation of the intake VTC 13 is prohibited.
[0035]
According to the sixth embodiment, in addition to obtaining substantially the same effects as the fourth embodiment, the prohibition of the operation of the exhaust VTC 15 and the prohibition of the operation of the intake VTC 13 are performed stepwise in this order in accordance with the decrease in the oil pressure. Therefore, the operation range of the VTC can be expanded and the engine operability can be improved while reliably avoiding the failure of the VTC (reduction in operation responsiveness).
[0036]
Although the present invention has been described based on the specific embodiments as described above, the present invention is not limited to these embodiments and includes various modifications and changes without departing from the gist of the present invention. It is a thing. For example, in the above-described embodiment, a variable valve mechanism capable of continuously changing the valve lift characteristic is used. However, the present invention is not limited to this. A switching type variable valve mechanism may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a variable valve operating device for an internal combustion engine according to the present invention.
FIG. 2 is a hydraulic circuit diagram showing an example in which an oil temperature sensor is provided in a hydraulic circuit.
FIG. 3 is a flowchart illustrating a flow of a setting process of a switching permission flag.
FIG. 4 is a flowchart showing a control flow according to the first embodiment of the present invention.
FIG. 5 is a flowchart showing a control flow according to a second embodiment of the present invention.
FIG. 6 is a hydraulic circuit diagram showing an example in which a hydraulic sensor is provided in the hydraulic circuit.
FIG. 7 is a flowchart showing a control flow according to a third embodiment of the present invention.
FIG. 8 is a flowchart showing a control flow according to a fourth embodiment of the present invention.
FIG. 9 is an explanatory diagram for explaining the operation and effect when only the operation of the exhaust VTC is prohibited.
FIG. 10 is a flowchart showing a control flow according to a fifth embodiment of the present invention.
FIG. 11 is a flowchart showing a control flow according to a sixth embodiment of the present invention.
[Explanation of symbols]
1: Engine control unit (operation inhibition means)
11 ... intake VTC solenoid (intake side hydraulic control valve / operation inhibiting means)
13. Intake VTC (intake side variable valve mechanism)
12. Exhaust VTC solenoid (exhaust side hydraulic control valve / operation inhibiting means)
15 Exhaust VTC (exhaust side variable valve mechanism)
22 ... Hydraulic sensor (hydraulic parameter detecting means)
24 ... oil temperature sensor (hydraulic parameter detection means)
31 ... oil pump (hydraulic power source)

Claims (8)

A hydraulic pressure source for pressurizing hydraulic oil,
An intake-side variable valve mechanism that operates by hydraulic pressure to change the valve lift characteristics of the intake valve;
An exhaust-side variable valve mechanism that operates by hydraulic pressure to change the valve lift characteristics of the exhaust valve;
Hydraulic pressure parameter detecting means for detecting a hydraulic parameter related to the hydraulic pressure,
Operation inhibiting means for inhibiting at least one of the intake-side variable valve mechanism and the exhaust-side variable valve mechanism based on the hydraulic parameter;
A variable valve device for an internal combustion engine having the same. The oil pressure parameter detecting means is an oil temperature sensor for detecting an oil temperature,
The operation prohibiting means prohibits the operation of at least one of the intake-side variable valve mechanism and the exhaust-side variable valve mechanism when the oil temperature detected by the oil temperature sensor exceeds a first oil temperature threshold. 3. The variable valve device for an internal combustion engine according to claim 1. The method according to claim 2, wherein the operation prohibiting means prohibits the operation of both the intake-side variable valve mechanism and the exhaust-side variable valve mechanism when the oil temperature detected by the oil temperature sensor exceeds the first oil temperature threshold. A variable valve train for an internal combustion engine according to claim 1. The operation prohibiting means prohibits the operation of only the exhaust-side variable valve mechanism when the oil temperature detected by the oil temperature sensor exceeds a second oil temperature threshold which is a value lower than the first oil threshold. 4. The variable valve operating device for an internal combustion engine according to 2 or 3. The hydraulic pressure parameter detecting means is a hydraulic pressure sensor that detects a hydraulic pressure,
The said operation prohibition means prohibits operation | movement of at least one of an intake side variable valve mechanism and an exhaust side variable valve mechanism when the hydraulic pressure detected by a hydraulic pressure sensor is lower than a 1st hydraulic pressure threshold value. Variable valve train for internal combustion engines. 6. The device according to claim 5, wherein the operation prohibiting unit prohibits the operation of both the intake-side variable valve mechanism and the exhaust-side variable valve mechanism when the oil pressure detected by the oil pressure sensor is lower than the first oil pressure threshold value. Variable valve gear for internal combustion engines. The operation prohibiting means prohibits the operation of only the exhaust-side variable valve mechanism when the oil pressure detected by the oil pressure sensor is lower than a second oil pressure threshold which is higher than the first oil pressure threshold. 7. The variable valve train for an internal combustion engine according to 6. An intake hydraulic control valve for switching and controlling the hydraulic pressure supplied from the hydraulic source to the intake variable valve mechanism, and an exhaust hydraulic control valve for switching and controlling the hydraulic pressure supplied from the hydraulic source to the exhaust variable valve mechanism. And
8. The variable valve operating device for an internal combustion engine according to claim 1, wherein the operation prohibiting unit prohibits the operation of the variable valve mechanism by prohibiting the supply of the hydraulic pressure by the hydraulic control valve.

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