Control apparatus and method of variable valve event and lift mechanism

Abstract

In a variable valve event and lift mechanism that rotates a control shaft by a motor to successively vary a valve event and a valve lift amount of engine valves, a VEL control unit integrally provided with an angle sensor that detects a rotation angle of the control shaft, is disposed and a signal of a target rotation angle of the control shaft is output to the VEL control unit from an engine control unit, so that the VEL control unit feedback controls the motor.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a control apparatus and a control method a variable valve event and lift (VEL) mechanism for successively varying a valve event and a valve lift amount of an engine valve by rotating a control shaft of the VEL mechanism by a motor.

RELATED ART OF THE INVENTION

[0002] The above VEL mechanism is disclosed in Japanese Unexamined Patent Publication 2000-282901.

[0003] The VEL mechanism is provided with a control shaft disposed substantially in parallel with a camshaft, a control cam eccentrically fixed to a periphery of the control shaft, a rocker arm axially supported by the control cam so as to be enable to swing, a link arm and an eccentric cam that drive to swing one end of the rocker arm in response to rotation of the camshaft, a swing cam which is connected to the other end of the rocker arm and swings to open an engine valve, and a DC servo motor which rotates the control shaft.

[0004] In this VEL mechanism, a valve event and a valve lift amount are successively varied by changing a rotation angle of the control shaft by the DC servo motor.

[0005] In such a conventional VEL mechanism, a detection signal from an angle sensor is input via a harness to an engine control unit which is input with detection signals from sensors that detect engine operating conditions and controls fuel injection and ignition timing of an engine.

[0006] In the engine control unit, a target rotation angle of the control shaft is calculated and at the same time, a feedback control signal is calculated based on deviation between an actual rotation angle and the target rotation angle of the control shaft, so that the calculated feedback control signal is output to the DC servo motor.

[0007] However, according to such a construction, the noise from the harness is likely to interfere with the detection signal from the angle sensor.

[0008] Thus, detection accuracy of the rotation angle is worsened due to the noise and it is hard to accurately control the rotation angle of the control shaft, and also a calculation load of the control unit is also increased.

SUMMARY OF THE INVENTION

[0009] In view of the above problems, the present invention has an object to provide a control apparatus and a control method of a VEL mechanism capable of improving a noise resistance performance of a rotation angle detection signal and also reducing a calculation load of an engine control unit.

[0010] In order to achieve the above object, according to the present invention, there is provided a VEL control unit integrally equipped with an angle sensor and the VEL control unit calculates a control signal of a motor based on a detection signal from the angle sensor.

[0011] Other objects and features of this invention will be understood from the following description with reference to the accompanying drawings.

BRIEF EXPLANATION OF THE DRAWINGS

[0012] FIG. 1 is a cross section view showing a VEL mechanism (A-A cross section view of FIG. 2)

[0013] FIG. 2 is a side elevation view of the VEL mechanism.

[0014] FIG. 3 is a top plan view of the VEL mechanism.

[0015] FIG. 4 is a perspective view showing an eccentric cam for use in the VEL mechanism.

[0016] FIG. 5A and FIG. 5B are cross section views showing an operation of the VEL mechanism at a low speed and low load condition of an engine (B-B cross section view of FIG. 2).

[0017] FIG. 6A and FIG. 6B are cross section views showing an operation of the VEL mechanism at a high speed and high load condition of the engine (B-B cross section view of FIG. 2).

[0018] FIG. 7 is a valve lift characteristic diagram corresponding to a cam surface of a swing cam in the VEL mechanism.

[0019] FIG. 8 is a block view diagram a control apparatus of the VEL mechanism.

[0020] FIG. 9 is a characteristic diagram showing valve timing and valve lift of the VEL mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] FIG. 1 to FIG. 3 show a variable valve event and lift (VEL) mechanism which successively varies a valve lift amount and a valve event of each of two intake valves as engine valves provided for one cylinder.

[0022] The VEL mechanism may be constructed to drive exhaust valves as the engine valves.

[0023] A VEL mechanism 100 shown in FIG. 1 to FIG. 3 includes a pair of intake valves 12, 12, a hollow camshaft 13 rotatably supported by a cam bearing 14 of a cylinder head 11, two eccentric cams 15, 15 as rotation cams axially supported by camshaft 13, a control shaft 16 rotatably supported by the same cam bearing 14 at an upper position of camshaft 13, a pair of rocker arms 18, 18 swingingly supported by control shaft 16 through a control cam 17, and a pair of independent swing cams 20,20 disposed to upper portions of intake valve 12,12 through valve lifters 19,19, respectively.

[0024] Eccentric cams 15, 15 are connected with rocker arms 18, 18 by link arms 25, 25, respectively. Rocker arms 18,18 are connected with swing cams 20, 20 by link members 26, 26.

[0025] Each eccentric cam 15, as shown in FIG. 4, is formed in a substantially ring shape and includes a cam body 15a of small diameter, a flange portion 15b integrally formed on an outer surface of cam body 15a. A camshaft insertion hole 15c is formed through the interior of eccentric cam in an axial direction, and also a center axis X of cam body 15a is biased from a center axis Y of camshaft 13 by a predetermined amount.

[0026] Eccentric cam 15, 15 are pressed and fixed to both outer sides of camshaft 13 via camshaft insertion holes 15c at positions not interfering with valve lifters 19, 19.

[0027] Each rocker arm 18, as shown in FIG. 3, is bent and formed in a substantially crank shape, and a central base portion 18a thereof is rotatably supported by control cam 17.

[0028] A pin hole 18d is formed through one end portion 18b which is formed to protrude from an outer end portion of base portion 18a. A pin 21 to be connected with a tip portion of link arm 25 is pressed into pin hole 18d. A pin hole 18e is formed through the other end portion 18c which is formed to protrude from an inner end portion of base portion 18a. A pin 28 to be connected with one end portion 26a (to be described later) of each link member 26 is pressed into pin hole 18e.

[0029] Control cam 17 is formed in a cylindrical shape and fixed to a periphery of control shaft 16. As shown in FIG. 1, a center axis P1 position of control cam 17 is biased from a center axis P2 position of control shaft 16 by &agr;.

[0030] Swing cam 20 is formed in a substantially lateral U-shape as shown in FIG. 1, FIG. 5 and FIG. 6, and a supporting hole 22a is formed through a substantially ring-shaped base end portion 22. Camshaft 13 is inserted into base end portion 22 to be rotatably supported. Also, a pin hole 23a is formed through an end portion 23 positioned at the other end portion 18c of rocker arm 18.

[0031] A base circular surface 24a of base end portion 22 side and a cam surface 24b extending in an arc shape from base circular surface 24a to an edge of end portion 23, are formed on a bottom surface of swing cam 20. Base circular surface 24a and cam surface 24b are in contact with a predetermined position of an upper surface of each valve lifter 19 corresponding to a swing position of swing cam 20.

[0032] Namely, according to a valve lift characteristic shown in FIG. 7, as shown in FIG. 1, a predetermined angle range &thgr;1 of base circular surface 24a is a base circle interval and a range of from base circle interval &thgr;1 of cam surface 24b to a predetermined angle range &thgr;2 is a so-called ramp interval, and a range of from ramp interval &thgr;2 of cam surface 24b to a predetermined angle range &thgr;3 is a lift interval.

[0033] Link arm 25 includes a ring-shaped base portion 25a and a protrusion end 25b protrudingly formed on a predetermined position of an outer surface of base portion 25a. A fitting hole 25c rotatably to be fitted with an outer surface of cam body 15a of eccentric cam 15 is formed on a central position of base portion 25a. Also, a pin hole 25b into which pin 21 is inserted is formed through protrusion end 25b.

[0034] A swinging-driving member is composed of link arm 25 and eccentric cam 15.

[0035] Link member 26 is formed in a linear shape of predetermined length and pin insertion holes 26c, 26d are formed through both circular end portions 26a, 26b. End portions of pins 28, 29 pressed into pin hole 18d of the other end portion 18c of rocker arm 18 and pin hole 23a of end portion 23 of swing cam 20, respectively, are rotatably inserted into pin insertion holes 26c, 26d.

[0036] Snap rings 30, 31, 32 restricting axial transfer of link arm 25 and link member 26 are disposed on respective end portions of pins 21, 28, 29.

[0037] Control shaft 16 is driven to rotate within a predetermined angle range by a DC servo motor 101 disposed at one end portion thereof.

[0038] DC servo motor 101, as shown in FIG. 8, is controlled by a control signal from a VEL control unit (VEL-C/U) 102.

[0039] Rotation of a rotation shaft of DC servo motor 101 is transmitted via a speed reducing gear mechanism 103 to control shaft 16.

[0040] VEL control unit 102 is integrally provided with an angle sensor 104 that detects a rotation angle of control shaft 16 in a non-contact manner and is disposed in the vicinity of control shaft 16.

[0041] An optical angle sensor or a magnetic angle sensor may be used for non-contact type angle sensor 104.

[0042] VEL control unit 102 receives a target rotation angle signal from an engine control unit (ECU) 105 and feedback controls a control signal to DC servo motor 101 so as to coincide an actual rotation angle detected by angle sensor 104 with a target rotation angle.

[0043] Since angle sensor 104 is disposed integrally to VEL control unit 102, there is a low possibility of noise interference until the detection signal of angle sensor 104 is read at VEL control unit 102.

[0044] Accordingly, it is avoided that detection accuracy of rotation angle is deteriorated due to noise interference with the angle detection signal, thereby enabling to control the rotation angle of control shaft 16 with high accuracy.

[0045] If the feedback control of the control signal is performed at VEL control unit 102, a calculation load of engine control unit 105 is reduced compared with the case where such a calculation is performed at engine control unit 105.

[0046] VEL control unit 102 also performs a failure diagnosis of VEL mechanism 100 and outputs the diagnosis result to engine control unit 105.

[0047] In the failure diagnosis, it is judged that VEL mechanism 100 is failed when the rotation angle of control shaft 16 cannot be made to coincide with the target angle by the feedback control.

[0048] Engine control unit 105 that has received a failure judgment signal, forcibly fixes the target angle to be output to VEL control unit 102, to a predetermined value, and also executes a failsafe processing of switching on a warning lamp 106.

[0049] Engine control unit 105 receives detection signals from an engine operating condition sensor 108 including a crank sensor detecting an angle of a crankshaft of an engine 107, an air flow meter detecting an intake air amount of engine 107 and the like.

[0050] Based on the detection signals from engine operating condition sensor 108, engine control unit 105 calculates the target rotation angle, to output a signal of the target rotation angle to VEL control unit 102 through CAN (Controller Area Network) communication, and also receives a signal of the failure diagnosis result from VEL control unit 102 through the CAN communication.

[0051] Engine control unit 105 calculates a fuel injection pulse signal based on the various detection signals to output this fuel injection pulse signal to an injector of engine 107, and calculates an ignition control signal to output this ignition control signal to a power transistor disposed to an ignition plug of engine 107.

[0052] An operation of VEL mechanism 100 will be described as follows.

[0053] At a time of low speed and low load of the engine, the target angle of control shaft 16 corresponding to a required valve opening characteristic under such a condition is output to VEL control unit 102 from engine control unit 105, and DC serve motor 101 is driven to rotate in one way by the control signal from VEL control unit 102.

[0054] As a result, center axis P1 of control cam 17, as shown in FIG. 5A and FIG. 5B, is held at a rotation position of upper left side from center axis P2 of control shaft 16 and a thick portion 17a of control cam 17 moves away in the upper direction from camshaft 13.

[0055] Accordingly, the entirety of rocker arm 18 moves upward relative to camshaft 13, and as a result, end portion 23 of each swing cam 20 is forcibly raised up a little via link member 26 and the entirety of swing cam 20 rotates in the left direction.

[0056] Therefore, as shown in FIG. 5A and FIG. 5B, when eccentric cam 15 rotates to push up one end portion 18b of rocker arm 18 through link arm 25, a lift amount is transmitted to swing cam 20 and valve lifter 19 via link member 26 but the lift amount L1 becomes relatively smaller as shown in FIG. 5B.

[0057] Thus, under such a low velocity and low load condition, as shown by a dotted line of FIG. 9, the valve lift amount becomes smaller, as well as opening timing of each intake valve is delayed (a valve event becomes smaller). As a result, the valve overlap between the intake valve and the exhaust valve becomes smaller.

[0058] On the other hand, when the condition is shifted to a high velocity and high load condition, the target angle of control shaft 16 corresponding to the required valve opening characteristic under such a condition is output to VEL control unit 102 from engine control unit 105, and DC servo motor 101 is driven to rotate in the opposite direction by the control signal from VEL control unit 102.

[0059] Accordingly, as shown in FIG. 6A and FIG. 6B, control shaft 16 rotates control cam 17 in the clockwise direction from a position shown in FIG. 5 and moves center axis P1 (thick portion 17a) downward.

[0060] Therefore, the entirety of rocker arm 18 moves in the camshaft 13 direction (downward). The other end portion 18c presses end portion 23 of swing cam 20 downward via link member 26 to rotate the entirety of swing cam 20 in the clockwise direction by a predetermined amount.

[0061] Accordingly, contact position of a lower surface of swing cam 20 to the upper surface of valve lifter 19 moves in the left direction position as shown FIG. 6A and FIG. 6B.

[0062] As a result, when eccentric cam 15 rotates to push up one end portion 18b of rocker arm 18 via link arm 25, the lift amount L2 to valve lifter 19 becomes larger as shown in FIG. 6B.

[0063] Thus, under such a high velocity and high load condition, the cam lift characteristic is increased compared with that under the low velocity and low load condition, and as shown by a solid line of FIG. 9, the valve lift amount (valve event) is also increased, as well as opening timing of each intake valve is advanced and closing timing thereof is retarded.

[0064] The entire contents of a Japanese Patent Application No. 2001-211502, filed Jul. 12, 2001 are incorporated herein by reference.

[0065] While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various change and modification can be made herein without departing from the scope of the invention as defined in the appended claims.

[0066] Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Claims

1. A control apparatus of a variable valve event and lift (VEL) mechanism of an engine for rotating a control shaft by a motor to successively vary a valve event and a valve lift amount of engine valves, comprising;

an angle sensor that detects a rotation angle of said control shaft; and

a VEL control unit that receives a detection signal from said angle sensor, and calculates a control signal of said motor based on said detection signal to output said control signal to said motor,

wherein said VEL control unit is integrally provided with said angle sensor.

2. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 1,

wherein said VEL mechanism comprises:

a control cam that is eccentrically fixed to a periphery of said control shaft;

a rocker arm that is axially supported by said control cam so as to be enable to swing;

a swinging-driving member that drives to swing one end portion of said rocker arm in response to rotation of the engine; and

a swing cam that is connected with the other end portion of said rocker arm and swings to open and close the engine valves.

3. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 1,

wherein said angle sensor is a sensor that detects the rotation angle of said control shaft in a non-contact manner.

4. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 1,

wherein said VEL control unit feedback controls said control signal so as to coincide the rotation angle of said control shaft detected by said angle sensor with a target rotation angle of said control shaft.

5. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 4, further comprising:

an operating condition sensor that detects an engine operating condition; and

an engine control unit that receives a detection signal from said operating condition sensor, and calculates a target rotation angle signal of said control shaft based on said detection signal to output said target rotation angle signal to said VEL control unit.

6. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 5,

wherein said VEL control unit performs a failure diagnosis of said VEL mechanism, and outputs a result of the failure diagnosis to said engine control unit.

7. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 6,

wherein said engine control unit fixes the target rotation angle signal of said control shaft to be output to said VEL control unit to a previously set value when said engine control unit receives a failure judgment signal of said variable event and lift mechanism.

8. A control apparatus of a variable valve event and lift (VEL) mechanism according to claim 5,

wherein said VEL control unit outputs a signal indicating the rotation angle of said control shaft detected by said angle sensor, to said engine control unit.

9. A control apparatus of a variable valve event and lift (VEL) mechanism of an engine for rotating a control shaft by a motor to successively vary a valve event and a valve lift amount of engine valves, comprising;

an angle sensor that detects a rotation angle of said control shaft;

an operating condition sensor that detects an engine operation condition;

an engine control unit that receives a detection signal from said operating condition sensor; and

a VEL control unit that receives a detection signal from said angle sensor, and is capable to communicate mutually with said engine control unit,

wherein said engine control unit calculates a target rotation angle signal of said control shaft to output said target rotation angle signal to said VEL control unit, and

said VEL control unit is integrally provided with said angle sensor;

feedback controls said motor so as to coincide the rotation angle detected by said angle sensor with a target rotation angle of said control shaft; and

performs a failure diagnosis of said VEL mechanism, and outputs a signal indicating a result of said failure diagnosis and a signal indicating the rotation angle of said control shaft detected by said angle sensor to said engine control unit.

10. A control method of a variable valve event and lift (VEL) mechanism of an engine for rotating a control shaft by a motor to successively vary a valve event and a valve lift amount of engine valves, comprising:

detecting a rotation angle of said control shaft by an angle sensor;

outputting a detection signal of said rotation angle to a VEL control unit integrally provided with said angle sensor;

calculating a control signal of said motor based on the detection signal of said rotation angle by said VEL control unit; and

outputting said control signal to said motor by said VEL control unit.

11. A control method of a variable valve event and lift (VEL) mechanism according to claim 10,

wherein said VEL mechanism comprises:

a control cam that is eccentrically fixed to a periphery of said control shaft;

a rocker arm that is axially supported by said control cam so as to be enable to swing;

a swinging-driving member that drives to swing one end portion of said rocker arm in response to rotation of the engine; and

a swing cam that is connected with the other end portion of said rocker arm and swings to open and close the engine valves.

12. A control method of a variable valve event and lift (VEL) mechanism according to claim 10,

wherein said angle sensor is a sensor that detects the rotation angle of said control shaft in a non-contact manner.

13. A control method of a variable valve event and lift mechanism according to claim 10,

wherein said VEL control unit feedback controls said control signal so as to coincide the rotation angle of said control shaft detected by said angle sensor with a target rotation angle of said control shaft.

14. A control method of a variable valve event and lift (VEL) mechanism according to claim 13,

wherein a detection signal of an engine operating condition from an operating condition sensor is output to an engine control unit,

a target rotation angle signal of said control shaft is calculated based the detection signal of said engine operating condition by said engine control unit, and

said target rotation angle signal is output by said engine control unit to said VEL control unit.

15. A control method of a variable valve event and lift mechanism according to claim 14,

wherein said VEL control unit performs a failure diagnosis of said VEL mechanism, and

said VEL control unit outputs a result of the failure diagnosis to said engine control unit.

16. A control method of a variable valve event and lift mechanism according to claim 15,

wherein said engine control unit fixes the target rotation angle signal of said control shaft to be output to said VEL control unit to a previously set value when the failure of said VEL mechanism is judged.

17. A control method of a variable valve event and lift mechanism according to claim 14,

wherein said VEL control unit outputs a signal indicating the rotation angle of said control shaft detected by said angle sensor, to said engine control unit.