JP2011021572A - Variable cam phase type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable cam phase type internal combustion engine improved in control accuracy of VTC actuator and the like. <P>SOLUTION: A front end side journal 43 of an intake shaft 4 is rotatably supported by bearing surfaces 61, 62 of a first cam holder 50, and the rear end surface of a VTC attachment flange 41 and the front end surface of a thrust flange 42 come in slide-contact with the axial direction end surfaces of the first cam holder 50. Pulser teeth 71, 72 are projectingly provided on an outer circumference of a back plate 25. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cam phase variable internal combustion engine in which a cam phase is continuously variably controlled, and more particularly to a technique for improving control accuracy of a VTC actuator.

  Many 4-cycle engines (hereinafter simply referred to as engines) are equipped with various variable valve mechanisms in order to improve output and fuel consumption and reduce harmful exhaust gas components. In recent years, variable valve mechanisms have been mainly used in which the cam phase and the valve lift are variably controlled in place of the conventional switching of a plurality of cams (for example, a low speed cam and a high speed cam). It is coming. A valve timing control device (Variable Timing Control device: hereinafter referred to as VTC) used for variable control of a cam phase is disposed on the axis of a vane-type VTC actuator or VTC actuator attached to the tip of a camshaft. A spool valve that switches a hydraulic circuit, a linear solenoid that drives the spool of the spool valve in the axial direction, and the like (see Patent Document 1).

  In a VTC-equipped engine, it is necessary to detect the actual camshaft angle (cam angle) in real time by a cam angle sensor in order to perform feedback control of the cam phase. As a cam angle sensor, a pulsar rotor having a plurality of teeth (pulsar teeth) on the outer periphery is fastened / integrated to the rear end of the camshaft, and a sensor body (pickup coil or the like) is installed in the vicinity of the pulsar rotor. (See Patent Document 2). In an engine in which a VTC actuator is mounted on only one of the intake and exhaust camshafts, a TDC (Top Dead Center: top dead center) is provided at the rear end of the fixed (the cam phase is not controlled) camshaft. Point) A sensor is often attached.

Japanese Patent No. 4059673 JP 2009-36189 A

  In a VTC-equipped engine, the VTC actuator is fastened to the tip of the camshaft, while the linear solenoid is mounted on the engine body (cylinder head or the like). Therefore, in order to increase the control accuracy of the VTC, it is necessary to regulate the relative distance between the linear solenoid (rod end) and the VTC actuator (spool end of the spool valve) with high accuracy. The operation stroke of the linear solenoid is generally about 3 mm, and the accumulation of machining tolerances and assembly tolerances of each member is about 0.5 mm. Therefore, even when the relative distance between the linear solenoid and the VTC actuator does not change at all, the operating stroke that can be used for phase control is 2.5 mm, and the cam phase and the phase conversion speed are adjusted within this operating stroke range. .

  However, in the case of a conventional VTC-equipped engine, as shown in FIG. 5, the camshaft 4 is regulated by a pulsar rotor 80 of a cam angle sensor attached to the rear end of the camshaft 4 so that the engine is warmed up. The accompanying temperature rise causes the VTC actuator 21 to move relatively large in the axial direction. For example, when the cast steel camshaft 4 is held by the aluminum alloy cylinder head 1, the distance L1 from the pulsar rotor 80 to the tip of the VTC actuator 21 is 435 mm, and the distance from the pulsar rotor 80 to the center point of the linear solenoid 31 When L2 is 450 mm, when the temperature rises about 100 ° C., the linear expansion coefficient is different between the linear solenoid 31 and the VTC actuator 21 due to the difference in linear expansion coefficient (the linear expansion coefficient of the camshaft 4 is smaller than the linear expansion coefficient of the cylinder head 1). The relative distance increases by about 0.5 mm. As a result, the relative distance between the rod end of the linear solenoid 31 and the spool end of the spool valve increases correspondingly, and in the case of the above-described example, the phase control is performed with an operating stroke of 2.0 mm. As a result, the control resolution (the change width of the operating speed of the VTC actuator 21 with respect to the stroke amount of the linear solenoid 31) is lowered, resulting in a deterioration in control accuracy that cannot be ignored.

  On the other hand, as shown in FIG. 5, the conventional VTC actuator 21 is fastened to a VTC mounting flange 41 formed at the front end of the camshaft 4, and receives a supply of hydraulic oil from the front end side cam holder 50. Yes. Therefore, when the relative displacement in the axial direction of the VTC mounting flange 41 described above occurs, between the hydraulic oil supply groove formed in the front end side cam holder 50 and the hydraulic oil introduction hole formed in the journal of the camshaft 4. There is a possibility that a deviation occurs, and the amount of hydraulic oil supplied to the VTC actuator 21 is reduced to deteriorate the controllability. Further, since the pulsar rotor of the TDC sensor described above is fastened / integrated to the rear end of the camshaft, if a large-diameter one is adopted in order to increase detection accuracy, the outline of the cylinder head or cam cover becomes large. There was a problem.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a variable cam phase internal combustion engine that realizes improvement in control accuracy of a VTC actuator.

  The first invention is rotatably supported by a plurality of cam holders, a VTC mounting flange is fastened to one end of the camshaft, and the VTC mounting flange is used for variable control of the cam phase. A cam phase variable internal combustion engine having a VTC actuator, wherein the camshaft is provided with a thrust flange in the axial direction with respect to the VTC mounting flange, and the VTC mounting flange and the VTC. At least one of the actuators and the thrust flange are each formed with a thrust surface slidably contacting the axial end surface of the cam holder closest to the VTC actuator.

  According to a second invention, in the cam phase variable internal combustion engine according to the first invention, the VTC actuator has a cylindrical housing, and a pulsar rotor of a TDC sensor is formed on an outer periphery of the housing. And

  According to the first invention, since the camshaft thrust direction is regulated in the immediate vicinity of the VTC actuator, the axial movement of the VTC actuator due to the temperature change of the engine is suppressed, and the VTC is controlled by the linear solenoid attached to the cylinder head. Even when the actuator is driven, it is difficult for the control accuracy to decrease due to a change in the relative distance between the linear solenoid and the VTC actuator. Further, according to the second invention, the diameter of the pulsar rotor of the TDC sensor can be increased without causing an increase in the size of the cam cover, and the TDC detection accuracy can be improved. Further, if the teeth of the pulsar rotor are protruded from the outer periphery of the housing, an independent pulsar rotor is unnecessary, and the number of parts can be reduced.

It is a principal part perspective view of the engine which concerns on embodiment. It is a disassembled perspective view of the VTC actuator which concerns on embodiment. It is a disassembled perspective view of the intake camshaft front end side according to the embodiment. It is a longitudinal cross-sectional view of the intake camshaft front end side according to the embodiment. It is a side view which shows the structure around the cam shaft in a conventional apparatus.

  Several embodiments of a cam phase variable internal combustion engine according to the present invention will be described below in detail with reference to the drawings.

[Embodiment]
<< Configuration of Embodiment >>
<Overall configuration>
An engine (cam phase variable internal combustion engine) E shown in FIG. 1 is a DOHC 4-valve four-cycle in-line four-cylinder gasoline engine mounted on an automobile. An intake valve 2 for each cylinder is provided in the cylinder head 1. And an exhaust valve 3, an intake camshaft 4 and an exhaust camshaft 5 that drive the intake and exhaust valves 2 and 3. Both camshafts 4 and 5 are rotationally driven by the crankshaft 10 at a rotational speed of 1/2 through the crank sprocket 6, the cam chain 7, the intake cam sprocket 8, and the exhaust cam sprocket 9. The crankshaft 10 is connected to the piston 12 via a connecting rod 11 and drives an oil pump 14 installed obliquely downward via a chain 13. A VTC actuator 21 is attached to the front end of the intake camshaft 4, and hydraulic oil supply oil for supplying hydraulic oil (engine oil) from the oil pump 14 to the VTC actuator 21 is supplied to the cylinder head 1 and the cylinder block 15. A path 16 is formed.

  A crank angle sensor 17 for detecting the rotation angle of the crankshaft 10 is installed in the vicinity of the crank sprocket 6, and a cam angle sensor 18 for detecting a cam phase is installed at the rear end of the intake camshaft 4. A TDC sensor 19 for detecting the top dead center of each cylinder is installed at the rear. These sensors 17 to 19 are connected to an engine ECU together with many other sensors (such as an intake air temperature sensor, a water temperature sensor, an accelerator sensor, etc.), and the engine ECU operates based on these detection signals (operation information). (Fuel injection amount, ignition timing, intake side cam phase, etc.) are set, and the fuel injection valve, ignition device, VTC actuator 21 and the like are driven and controlled.

<VTC actuator>
As shown in FIG. 2, the VTC actuator 21 includes a housing 22 in which an intake cam sprocket 8 is formed on the outer periphery, a rotor that is rotatably held in the housing 22, and a rear surface that is fastened to the front end of the intake camshaft 4. 23, a front plate 24 covering the front surface of the housing 22, a back plate 25 covering the rear surface of the housing 22, a reed valve 26 disposed on the inner peripheral side of the front plate 24, and a reed valve cover 27 for fixing the reed valve 26 to the rotor 23. , A bias spring 28 that relatively rotates the housing 22 and the rotor 23 in the advance direction, a spool valve 29 installed at the shaft center, a linear solenoid 31 that drives the spool valve 29 by being controlled by the engine ECU, and the rotor 23 Lock pin 33 held by Lock pin spring 34 for urging the Kkupin 33 to the back plate 25 side, and as a component of the bypass valve spring 37 or the like for urging the bypass valve 36 is held in the rotor 23, the bypass valve 36 in the back plate 25 side. The spool valve 29 includes a valve sleeve 38 held at the axis of the intake camshaft 4 and the rotor 23, a spool 39 slidably fitted in the valve sleeve 38, and the spool 39 attached to the linear solenoid 31 side. And a return spring 40 that is energized.

<Intake camshaft and cam holder>
As shown in FIGS. 3 and 4, the intake camshaft 4 includes a VTC mounting flange 41 to which the VTC actuator 21 is fastened, a thrust flange 42 facing the VTC mounting flange 41 at a predetermined interval in the axial direction, and a VTC mounting. A front end side journal 43 formed between the flange 41 and the thrust flange 42 is provided. The front end side journal 43 is provided with a hydraulic oil introduction hole 44 for introducing hydraulic oil to the spool valve 29 of the VTC actuator 21.

  A first cam holder 50 (a first lower cam holder 51 and a first upper cam holder 52) is fastened to the front end side of the cylinder head 1 so as to rotatably support the front end side journal 43 of the intake camshaft 4. A pair of front and rear hydraulic oil supply grooves 63 and 64 are formed in the bearing surfaces 61 and 62 of the first lower cam holder 51 and the first upper cam holder 52, and the hydraulic oil supplied from these hydraulic oil supply grooves 63 and 64 is supplied to the bearing surfaces 61 and 62. It is introduced into the VTC actuator 21 through the hydraulic oil introduction hole 44 of the front end side journal 43.

  The intake camshaft 4 has a front end journal 43 rotatably supported by bearing surfaces 61, 62 of the first cam holder 50, and the rear end surface of the VTC mounting flange 41 and the front end surface of the thrust flange 42 are the first cam holder 50. Is in sliding contact with the axial end surface of the. In the case of this embodiment, the rear end surface of the back plate 25 is also in sliding contact with the front end surface of the first cam holder 50 in the same manner as the rear end surface of the VTC mounting flange 41.

<TDC sensor>
The TDC sensor 19 includes five pulsar teeth (four top dead center discriminating pulsar teeth 71 and one cylinder discriminating pulsar teeth 72) provided on the outer periphery of the back plate 25, and close to these pulsar teeth 71 and 72. It is comprised from the sensor main body 73 arrange | positioned. In this embodiment, the pulsar teeth 71 and 72 are integrally formed on the back plate 25 (that is, the back plate 25 is also used as the pulsar rotor of the TDC sensor 19). The annular pulsar rotor may be fastened or press-fitted into the housing 22 or the back plate 25.

<< Operation of Embodiment >>
When the engine E is started, the engine ECU sets various operation control amounts of the engine E based on various operation information as described above, and drives and controls the fuel injection valve, the ignition device, the VTC actuator 21 and the like. At this time, the engine ECU feedback-controls the fuel injection timing and ignition timing using the detection signals of the crank angle sensor 17 and the TDC sensor 19, while using the detection signals of the crank angle sensor 17 and the cam angle sensor 18. Feedback control of cam phase of shaft 4

  As the warm-up proceeds and the temperature of the engine E rises, the cylinder head 1 expands with a larger linear expansion rate than the intake camshaft 4. However, in the present embodiment, the intake camshaft 4 is in sliding contact with the axial end surface of the first cam holder 50 with the rear end surface of the VTC mounting flange 41 and the front end surface of the thrust flange 42 (that is, the VTC actuator 21). Is held in the thrust direction by the first cam holder 50 closest to the head).

  Therefore, if the distance L3 from the first cam holder 50 to the tip of the VTC actuator 21 is 36 mm and the distance L4 from the first cam holder 50 to the center point of the linear solenoid 31 is 50 mm, the linearity is maintained even if the temperature rises by about 100 ° C. The relative distance between the solenoid 31 and the VTC actuator 21 increases only by about 0.07 mm. As a result, if the operation stroke of the linear solenoid 31 is 3 mm, and the accumulation of machining tolerances and assembly tolerances of each member is 0.5 mm, the operation stroke that can be used for phase control can be secured to 2.43 mm. In comparison, the control resolution is improved by about 20%.

  Further, since the relative displacement in the thrust direction between the intake camshaft 4 and the first cam holder 50 is reduced, the hydraulic oil supply grooves 63 and 64 on the first upper cam holder 52 side and the hydraulic oil introduction hole on the intake camshaft 4 side are reduced. 44 and the controllability due to a decrease in the amount of hydraulic oil supplied to the VTC actuator 21, which has been a problem with conventional devices, is less likely to occur.

  On the other hand, in this embodiment, since the pulsar teeth 71 and 72 of the TDC sensor 19 project from the back plate 25 of the VTC actuator 21, the TDC is not enlarged without increasing the outline of the cylinder head 1 or the cam cover (not shown). The detection accuracy can be improved and the number of parts can be reduced (independent pulsar rotor is not required).

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, although the above embodiment is an application of the present invention to an in-line four-cylinder DOHC gasoline engine, it can naturally be applied to a diesel engine or the like. In the above embodiment, the rear end surface of the VTC mounting flange and the back plate is in sliding contact with the front end surface of the first cam holder. However, the rear end surface of either the VTC mounting flange or the back plate is in contact with the front end surface of the first cam holder. You may make it slidably contact. In the above embodiment, the intake camshaft is provided with the VTC actuator. However, the present invention may be applied to a cam phase variable internal combustion engine having the exhaust camshaft with the VTC actuator. In addition, the specific configuration of the engine, the VTC actuator, and the like can be changed as appropriate without departing from the gist of the present invention.

1 Cylinder Head 4 Intake Cam Shaft 19 TDC Sensor 21 VTC Actuator 25 Back Plate 31 Linear Solenoid 41 VTC Mounting Flange 42 Thrust Flange 43 Front End Side Journal 50 First Cam Holder 71, 72 Pulsatis 73 Sensor Body E Engine

Claims (2)

A camshaft rotatably supported by a plurality of cam holders and having a VTC mounting flange formed at one end thereof;
A cam phase variable internal combustion engine that is fastened to the VTC mounting flange and includes a VTC actuator that is used for variable control of the cam phase,
The camshaft is provided with a thrust flange at a predetermined interval in the axial direction with respect to the VTC mounting flange,
A cam phase characterized in that at least one of the VTC mounting flange and the VTC actuator, and the thrust flange are formed with a thrust surface slidably contacting the axial end surface of the cam holder closest to the VTC actuator. Variable internal combustion engine.   The cam phase variable internal combustion engine according to claim 1, wherein the VTC actuator has a cylindrical housing, and a pulsar rotor of a TDC sensor is formed on an outer periphery of the housing.

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