JP2002054466A - Variable valve system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable valve system capable of varying the operating angle and the central phase of an intake valve 12 according to the operation state of an engine even when a potentiometer (an actual operating angle detecting means) 53 is in abnormality. SOLUTION: The variable valve system comprises an operating angle varying mechanism 10 capable of varying the operating angle of an intake valve 12; and a phase varying mechanism 70 capable of varying the central phase of the operating angle. Based on the rotation angle of a control shaft 16 detected by the potentiometer 53, a real operating angle is calculated and normality and abnormality of the potentiometer 53 are decided. During normality, feedback of the operating angle to a target operating angle is effected based on a real operating angle. During abnormality, open loop control of the operating angle to either a maximum operating angle or a minimum operating angle is effected based on an engine operation state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve capable of changing a valve lift characteristic of an intake valve or an exhaust valve of an internal combustion engine (both are collectively referred to as intake and exhaust valves) in accordance with engine operating conditions. Related to the device.

[0002]

2. Description of the Related Art The operation of intake / exhaust valves to improve fuel efficiency at low engine speed and low load, to ensure stable operability, and to secure sufficient output by improving intake charge efficiency at high engine speed and high load. Various variable valve operating devices capable of changing the angle and the opening / closing timing have been conventionally proposed.

[0003] For example, Japanese Patent Application Laid-Open No. 8-177
No. 434 discloses a valve lift adjusting mechanism (operating angle changing mechanism) that switches an operating angle of an intake valve between two stages by switching a cam driving an intake valve between a low speed cam and a high speed cam, and a crankshaft. A valve timing adjusting mechanism (phase changing mechanism) for adjusting the phase of the opening / closing timing of the intake valve with respect to the crankshaft (the center phase of the operating angle) by rotating the cam pulley and the camshaft, which are synchronized with the crankshaft, relative to each other. A variable valve device is disclosed.
In the high-speed range, the output is secured mainly by using a high-speed cam, and in the low-speed low-load range, the low-speed cam is used and the opening and closing timing of the intake valve is relatively advanced to reduce pumping loss. Is planned.

Further, in order to prevent the intake valves from interfering with each other or the piston, a failure detecting means such as a sensor for detecting a failure of the valve lift adjusting mechanism and the valve timing adjusting mechanism, and the failure detecting means. And means for detecting an abnormality of the detection means, when such a failure or abnormality is detected, when the valve lift adjustment mechanism lowers the lift side,
The valve timing adjustment mechanism is fixed to the retard side.

[0005]

However, in the apparatus disclosed in this publication, when any failure or abnormality is detected, the operating angle of the intake valve is fixed to the minimum operating angle, and the phase of the opening / closing timing is retarded. Is fixed to the side,
The valve lift characteristics cannot be switched according to the engine operating state. Therefore, in the event of an abnormality, even if the engine load or the engine speed increases, it is difficult to obtain a high output because the operating angle of the intake valve is fixed to the minimum operating angle.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and even when the actual operating angle detecting means for detecting the actual operating angle of the intake / exhaust valve is determined to be abnormal, the intake / exhaust valve can be operated. An object of the present invention is to provide a novel variable valve operating device for an internal combustion engine that can appropriately change an operating angle and a center phase of the operating angle according to an engine operating state.

[0007]

According to a first aspect of the present invention, there is provided a variable valve operating apparatus for an internal combustion engine, wherein an operating angle of an intake and exhaust valve can be changed within a range from a minimum operating angle to a maximum operating angle. A phase changing mechanism capable of changing the center phase of the operating angle with respect to the crankshaft, an actual operating angle detecting means for detecting an actual operating angle of the intake and exhaust valves, and determining whether the actual operating angle detecting means is normal or abnormal. It has abnormality determining means and control means for controlling the operating angle changing mechanism and the phase changing mechanism.

When the actual operating angle detecting means is determined to be normal, the control means selects a target operating angle corresponding to the engine operating state from the maximum operating angle, the minimum operating angle and one or more intermediate operating angles. An operating angle is set, and the operating angle of the intake / exhaust valve is feedback-controlled to the target operating angle based on the actual operating angle, and when the actual operating angle detecting means is determined to be abnormal, according to the engine operating state, One of the maximum operating angle and the minimum operating angle is set as a target operating angle, the operating angle of the intake / exhaust valve is controlled to the target operating angle by open-loop control, and the center is set based on the target operating angle at the time of abnormality. It is characterized by controlling the phase.

According to a second aspect of the present invention, both the operating angle changing mechanism and the phase changing mechanism are driven in accordance with the operating oil pressure supplied from a common oil pressure source. Sometimes, when the target operating angle is set to the maximum operating angle, an increase in operating hydraulic pressure supplied from the hydraulic pressure source to the phase changing mechanism is prohibited.

According to a third aspect of the present invention, the maximum engine speed in the operating region where the target operating angle is the minimum operating angle at the time of the abnormality is the maximum engine speed in the operating region where the target operating angle is the minimum operating angle at the time of the normal operation. It is characterized by being set lower than the number.

[0011] The invention according to claim 4 is characterized in that,
The engine speed at which the target operating angle is switched to the minimum operating angle or the maximum operating angle is increased with an increase in the temperature of the hydraulic oil.

[0012]

According to the first aspect of the present invention, the operating angle of the intake valve can be switched to the minimum operating angle or the maximum operating angle according to the engine operating condition even when the actual operating angle detecting means is abnormal. Therefore, for example, when applied to the intake valve side, the minimum operating angle is selected at the time of low engine speed and low load to improve fuel efficiency and stable drivability, and at the time of high engine speed and high load, the maximum operating angle is selected. Is selected, it is possible to secure a sufficient output by improving the charging efficiency of the intake air.

In the event of an abnormality, the center phase is controlled in accordance with the target operating angle set in the event of an abnormality, that is, the phase control is performed in a form different from that in the normal state. be able to.

According to the second aspect of the present invention, since both the operating angle changing mechanism and the phase changing mechanism are driven by the common hydraulic pressure source, the structure can be simplified. Also,
When the target operating angle at the time of abnormality is set to the maximum operating angle,
Since the increase in the operating oil pressure supplied from the hydraulic source to the phase change mechanism is prohibited, fluctuations and decreases in the hydraulic pressure supplied from the hydraulic source to the operation angle changing mechanism are suppressed, and the operating angle of the intake and exhaust valves is stabilized. The maximum operation angle can be maintained, and a desired output can be stably secured.

According to the third aspect of the invention, when the actual operating angle detecting means is abnormal, the maximum operating angle is selected in a wider engine rotation range than in the normal state, and a sufficient output can be ensured. .

According to the fourth aspect of the present invention, it is possible to appropriately set the target operating angle in accordance with a rise in the temperature of the hydraulic oil when an abnormality occurs. That is, when the operating oil temperature is relatively high, the engine speed for switching between the minimum operating angle and the maximum operating angle is increased, so that the engine speed range for selecting the minimum operating angle is substantially expanded. Form, ensuring engine stability. On the other hand, when the hydraulic oil temperature is relatively low, the engine speed at which the target operating angle is switched becomes relatively low, and the engine speed range for selecting the maximum operating angle is substantially expanded, High output can be secured in a wide engine speed range.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a first embodiment of a variable valve apparatus in which an operating angle changing mechanism 10 and a phase changing mechanism 70 are applied only to the intake valve 12 side.

First, the operating angle changing mechanism 10 will be described with reference to FIGS. Each cylinder is provided with a pair of intake valves 12, and a valve lifter 19 is provided above each intake valve 12. Above these valve lifters 19, a hollow drive shaft 13 having a lubricating oil passage formed therein extends in the cylinder row direction. The drive shaft 13 is rotationally driven by transmitting rotational power from a crankshaft via a phase changing mechanism 70 described later. A swing cam 20 is fitted to the drive shaft 13 so as to be swingable for each cylinder. Each oscillating cam 20 has a pair of cams 20A which respectively contact the upper surfaces of a pair of valve lifters 19 of each cylinder. When the oscillating cams 20 oscillate, the cams 20A and the valve lifters 19 are interposed. The intake valve 12 is configured to move up and down (open and close).

An operating angle changing mechanism 10 is provided between the drive shaft 13 and each swing cam 20.
That is, the operating angle changing mechanism 10 is provided eccentrically on the outer periphery of the drive shaft 13, and is fitted to the eccentric cam 15 that rotates integrally with the drive shaft 13, and is fitted around the outer periphery of the eccentric cam 15 so as to be relatively rotatable. A ring-shaped link 25 having a large-diameter portion 25a, a control shaft 16 extending substantially in parallel with the drive shaft 13 in the cylinder row direction, and provided eccentrically on the outer periphery of the control shaft 16 and integrated with the control shaft 16 Control cam 17 that rotates
A rocker arm 18 having a base portion 18a fitted to the outer periphery of the control cam 17 so as to be relatively rotatable, and having one end portion 18b rotatably connected to the small diameter portion 25b of the ring-shaped link 25 via the pin 21. An upper end 26a is connected to the other end 18c of the rocker arm 18 via a pin 28 so as to be relatively rotatable, and a lower end 26b is relatively rotatable via one pin 20A of the swing cam 20 via a pin 29. And a rod-like link 26 connected to the

The axis X of the eccentric cam 15 is eccentric by a predetermined amount β with respect to the axis Y of the drive shaft 13, and the axis P 1 of the control cam 17 is a predetermined amount α with respect to the axis P 2 of the control shaft 16. Only eccentric. The journal portion 20B of the swing cam 20 is
The control shaft 16 is rotatably supported between the cylinder head 11 and the main bearing bracket 14a, and the control shaft 16 is rotatably supported between the main bearing bracket 14a and the sub-bearing bracket 14b. These bearing brackets 14 (14a, 14b) are fastened and fixed to the cylinder head 11 side by the same mounting bolts 14c mainly for the purpose of simplification.

The control shaft 16 is driven to rotate by a motor 51 as a drive source shown in FIG. 1 and is held at a predetermined rotation position. In this embodiment, as shown in FIG.
Worm 52 provided on output shaft 51a of motor 51
Has a simple structure that directly meshes with the worm wheel 50 that is coaxially fixed to one end of the control shaft 16.

With such a configuration, when the drive shaft 13 rotates in conjunction with the crankshaft, the ring-shaped link 26 substantially translates via the eccentric cam 15, and
The rocker arm 18 swings around the axis P1 of the control cam 17, and the swing cam 20 swings via the rod-like link 26 to move the intake valve 12 up and down.

Also, by changing the rotation angle of the control shaft 16, the position of the axis P1 of the control cam 17, which is the center of swing of the rod-like link 26, changes, and the attitude of the swing cam 20 changes. Accordingly, while the center phase of the operating angle of the intake valve 12 with respect to the drive shaft 13 (the phase of the opening / closing timing) remains substantially constant, the operating angle of the intake valve 12 (the opening / closing period of the intake valve) and the valve lift amount are continuously increased. Change.

The operating angle changing mechanism 10 includes a bearing portion 25c of the eccentric cam 15 and a bearing portion 17c of the control cam 17.
In addition to a, since the bearing portions 25d, 26c, 26d of each pin are in surface contact, lubrication is easy, durability and reliability are excellent, and resistance when changing the operating angle is low. Is suppressed. Further, since the swing cam (cam 20A) for driving the intake valve 12 is arranged coaxially with the drive shaft 13, for example, a configuration in which the drive cam is supported by another support shaft different from the drive shaft. As compared with the above, the control accuracy is excellent, the device itself is compact, and the mountability on a vehicle is good. Furthermore, since the rod-shaped links 26 are arranged substantially vertically, the amount of protrusion toward the engine side (the left-right direction in FIG. 1) is suppressed.

Next, the phase changing mechanism 70 will be described with reference to FIG. The cam pulley 71 is transmitted with torque from a crankshaft via a timing belt (not shown). A phase changing mechanism 70 is provided between the cam pulley 71 and the drive shaft 13. This phase changing mechanism 70
By changing the phases of the two 71 and 13 in accordance with the operating conditions, the center phase of the operating angle of the intake valve 12 with respect to the crankshaft (the phase of the opening / closing timing) is changed.

More specifically, a cylindrical inner housing 65 is fixed to an end of the drive shaft 13 via a bolt 64. Further, a cylindrical outer housing 63 rotatably fitted on the outer periphery of the inner housing 65 is provided.
Are integrally formed.

A ring-shaped helical gear 73 is interposed between the inner housing 65 and the outer housing 63. The helical gear 73 has helical splines formed on the inner and outer circumferences, and each helical spline is formed on the outer circumference of the inner housing 65 and the outer housing 6.
3 meshes with the inner circumference. Therefore, the helical gear 73
Is moved in the axial direction, the inner housing 65 relatively rotates with respect to the outer housing 63, and the phase of the drive shaft 13 with respect to the cam pulley 71 changes.

A hydraulic chamber 75 is provided at one end of the helical gear 73.
Is defined. When the operating oil pressure guided to the hydraulic chamber 75 rises above a predetermined value, the helical gear 73 moves from the initial position to one side in the axial direction against the return spring 74 (FIG. 4).
Of the drive shaft 13 with respect to the cam pulley 71.
Are rotated in a direction to advance the opening / closing timing of the intake valve 12.

That is, when the helical gear 73 is at the initial position, the center phase of the operating angle of the intake valve 12 with respect to the crankshaft becomes the most retarded phase, and the helical gear 73
Is set to be the most advanced angle phase when is displaced to the maximum.

The hydraulic chamber 75 is connected to the drive shaft 13 and oil passages 78a and 78b formed in the cylinder head 11 through the oil passages 78a and 78b.
A discharge oil pressure from an oil pump 80 as a drive source is introduced.

A hydraulic control valve 79 is provided in the oil passage 78b of the cylinder head 11 for opening and closing in accordance with engine operating conditions in order to release the operating oil pressure appropriately. The hydraulic control valve 79 closes the oil passage 78b when not energized to reduce the oil pressure guided to the hydraulic chamber 75, and opens the oil passage 78b when energized to increase the oil pressure guided to the hydraulic chamber 75. It can be rephrased as a type switch.

As a control means for controlling the operating angle changing mechanism 10 and the phase changing mechanism 70, a control unit 54 for controlling the motor 51 and the hydraulic control valve 79 is provided.

The control unit 54 includes a memory, a CPU, and the like for storing and processing various engine control processes, and includes an engine rotation signal, an engine load signal, and the like.
A cooling water temperature signal, a working oil temperature signal, and the like are input, and based on these detected values, the valve lift characteristics are smoothly adjusted while suppressing a rapid change in engine torque.

As shown in FIGS. 5 and 6, the operating angle changing mechanism 10 is provided with a potentiometer 53 for detecting the angle of the control shaft 16. The potentiometer 53 is supported by a bracket 55 fixed to the cylinder head 11 and detects the rotation angle of the control shaft 16, more specifically, the rotation of the potentiometer pin 53 a that rotates integrally with the control shaft 16. Is output to the control unit 54.

As shown in FIG. 7A, the rotation angle of the control shaft 16 takes one value with respect to the output value of the potentiometer 53. Also, as shown in FIG.
The operating angle of the intake valve 12 takes one value with respect to the rotation angle. Therefore, the actual operating angle of the intake valve 12 is uniquely determined with respect to the output value of the potentiometer 53. That is, the potentiometer 53 constitutes a part of the actual operating angle detecting means for detecting the actual operating angle (actual operating angle) of the intake valve 12.

As the actual operating angle detecting means, for example, the valve lift of the intake valve 12 is directly detected,
5, the actual operating angle may be indirectly detected based on the output value.

FIG. 8 is a flowchart executed by the control unit 54, showing the flow of the control of the operating angle and the phase of the intake valve 12 by the two mechanisms 10, 70.

First, at S (step) 11, various sensors read the engine speed, the amount of intake air, the angle of the control shaft 16 corresponding to the actual operating angle, and the like. S12 that follows
Then, the potentiometer 53 as the actual operating angle detecting means
Is normal or abnormal (abnormality determining means).

The determination of normal or abnormal in S12 will be described in detail. As shown in FIGS. 5 and 6, a rotation angle regulating pin 56 is fixed to the rear outer periphery of the control shaft 16, and this rotation angle regulating pin 56 is fixed. The pin 56 moves between a pair of stoppers 57 provided on the bracket 55. In other words, the rotation angle regulating pin 56 and the pair of stoppers 57 allow the rotation range of the control shaft 16 to be within the control range Δθ from the minimum operation angle to the maximum operation angle.
It is regulated to 1. Since the rotation range Δθ1 of the control shaft 16 is regulated in this way, as shown in FIG. 7, when the potentiometer 53 is normal, the output value is smaller than the output possible range ΔH2 of the meter itself. Δ
Regulated to H1.

Therefore, in the above S12, when the output value of the potentiometer 53 is within the normal output range ΔH1, it is determined to be normal, and when it is out of this range ΔH1, it is determined to be abnormal.

If it is determined that it is normal (normal), S1
The process proceeds to step S3, and based on the engine speed and the engine load (torque) detected in S11, the target operating angle is set by referring to the normal operating angle map A1. In the operating angle map A1 for normal operation, areas corresponding to a plurality of (seven in this embodiment) intermediate operating angles in addition to the minimum operating angle and the maximum operating angle are indicated by a boundary indicated by a solid line a1 in FIG. Is provided. That is, the target operating angle can be finely switched to a plurality of stages (in this embodiment, nine stages) in accordance with the operating state.

In S14, feedback control is performed based on the detected actual operating angle so that the operating angle of the intake valve 12 becomes the target operating angle set in S13. Specifically, based on the amount of deviation of the actual operating angle from the target operating angle,
The duty ratio of the drive pulse output to the motor 51 is controlled.

Next, in S15, based on the engine speed, the engine load, and the actual operating angle (or the normal operating target angle), a predetermined normal phase map A2 (not shown) is referred to. The target phase of the center phase of the operating angle with respect to the crankshaft is determined. In this embodiment, the target phase is set to either the most advanced phase or the most retarded phase because the center phase is switched to two positions of the most advanced phase and the most retarded phase. On the basis of the target phase set in this way, in S16, the ON / OF of the solenoid of the hydraulic control valve 79 which is a changeover switch for the phase change is performed.
Determine F.

On the other hand, if it is determined in S12 that the potentiometer 53 is abnormal (abnormal), the process proceeds to S17, where an operating angle map B1 different from the normal operation is referred to based on the engine speed and the engine load. Set the target operating angle at the time of abnormality. This operating angle map B1 includes a broken line b in FIG.
1, two regions, a minimum operating angle and a maximum operating angle, are set. Therefore, in the event of an abnormality, either the minimum operating angle or the maximum operating angle is set as the target operating angle.

The operating angle of the intake valve is controlled in an open loop to the target operating angle set in this way. To explain this point in detail, when the potentiometer 53 is abnormal, the actual operating angle is not detected, and the feedback control cannot be performed as in the normal operation. However, since the rotatable angle of the control shaft 16 is regulated by the rotation angle regulating pin 56 and the stopper 57 within a range Δθ1 from the minimum operation angle to the maximum operation angle, the direction in which the control shaft 16 is driven is changed, so that the intake air is changed. It is possible to keep the operating angle of the valve 12 at either the minimum operating angle or the maximum operating angle. That is, the present embodiment is characterized in that, even in the event of an abnormality, the operating angle is switched to the minimum operating angle or the maximum operating angle in accordance with the engine operating state.

In the following S18, an abnormal phase map B2 (not shown), which is different from the normal state, is referred to based on the engine operating speed, the engine load, and the target operating angle in the abnormal state set in S17. Thus, the target phase of the center phase of the operating angle is determined. In S19, according to the target phase,
It is determined whether or not to operate the phase changing mechanism 70, and ON / OFF of the solenoid of the phase changing hydraulic control valve 79 is determined according to the result.

As described above, even when the potentiometer 53 as the actual operating angle detecting means is determined to be abnormal, the operating angle is switched to the maximum operating angle or the minimum operating angle by open loop control. Therefore, even in the event of an abnormality, it is possible to obtain an appropriate operating angle characteristic according to the engine operating state. That is, even in the abnormal state, the minimum operation angle is selected in the low rotation range such as at the time of starting or idling, and the maximum operation angle is selected in the middle and high speed rotation ranges while ensuring the startability and the idle stability. Thereby, the output of the engine can be improved.

In such an abnormal case, the target phase of the center phase by the phase changing mechanism 70 is set based on a phase map for an abnormal case different from the normal state and a target operating angle in the abnormal state, whereby the normal phase is set. Appropriate phase control can be performed independently of time.

FIG. 10 shows the configuration of the drive unit of the operating angle changing mechanism 10 according to the second embodiment. Explaining only the differences from the first embodiment, the control shaft 16 is electrically driven and controlled using the motor 51 in the above-described first embodiment, but the hydraulic actuator 101 is used in the second embodiment.
Drives the control shaft 16 according to the supply oil pressure of the hydraulic oil, and supplies the supply oil pressure to the hydraulic actuator 101 to the hydraulic control valve 1.
07 for duty control.

The hydraulic actuator 101 includes a hydraulic cylinder 103 attached to the cylinder head 11 (FIG. 3).
And a hydraulic piston 104 that is provided in the hydraulic cylinder 103 so as to be able to advance and retreat.

A radially protruding pin 105 is provided at the tip of the hydraulic piston 104, and this pin 105 can slide on a slit 102 a of a control plate 102 coaxially fixed to the rear end of the control shaft 16. Is fitted. Further, a first hydraulic chamber 103a and a second hydraulic chamber 103b are defined in a liquid-tight manner before and after a pressure receiving portion 104a of a hydraulic piston 104 housed inside the hydraulic cylinder 103, respectively. The hydraulic piston 104 moves in accordance with the hydraulic pressure of 103a, 103b, and the rotation angle of the control shaft 16 is adjusted.

The hydraulic pressure in each of the hydraulic chambers 103a and 103b is adjusted by a hydraulic control valve 107. That is, the hydraulic control valve 107 is turned on by the drive pulse signal corresponding to the duty ratio output from the control unit 54.
The hydraulic chambers 103a and 103b are selectively opened and closed by being driven OFF (duty control), whereby the stop position of the piston 104 is switched.

More specifically, the hydraulic control valve 107 includes a spool 109 that reciprocates in a cylindrical sleeve 108,
A solenoid 110 for controlling the drive of the spool 109 in response to a signal from the control unit 54. Each of the hydraulic chambers 103a, 103b
The first hydraulic supply oil passage 106a and the second hydraulic supply oil passage 106b are connected to the oil pump 80, the port of the hydraulic introduction oil passage 106c is connected to the oil pump 80, and the drain oil passage is connected to an oil pan (not shown). Port portions 106 d and 106 e are formed, and these port portions are selectively opened and closed according to the position of the spool 109.

When the spool 109 is held at the leftmost position in FIG. 10, the first hydraulic pressure supply oil passage 106a and the hydraulic pressure introduction passage 106c communicate with each other to supply hydraulic pressure to the first hydraulic chamber 103a. The second oil pressure supply passage 106b and the drain oil passage 106e communicate with each other, and the oil pressure in the second oil pressure chamber 103b decreases. As a result, the hydraulic piston 104 is
0 is pushed rightward.

On the other hand, in the state where the spool 109 is held at the rightmost position in FIG. 10 (the state in FIG. 10), the second hydraulic supply oil passage 106b and the hydraulic introduction passage 106c communicate with each other to the second hydraulic chamber 103b. As the oil pressure is supplied, the first oil pressure supply oil passage 106a and the drain oil passage 106d communicate with each other, and the oil pressure in the first oil pressure chamber 103a decreases. As a result, the hydraulic piston 104 is pressed to the left in FIG.

Further, the duty ratio is set to an intermediate value (for example, 5
By holding the spool 109 at the intermediate position (0%), both ports of the hydraulic supply oil passages 106a and 106b are closed. Thereby, the hydraulic chambers 103a, 103
The hydraulic pressure in 3b is held, and the hydraulic piston 104 is held at that position.

As described above, since the hydraulic piston 104 can be moved and held at an arbitrary position, the operating angle of the intake valve can be controlled to a predetermined value, similarly to the case where the hydraulic piston 104 is electrically controlled as in the first embodiment. It can be set in multiple steps within the range.

Further, since the phase changing mechanism 70 and the operating angle changing mechanism 10 are driven by the oil pump 80 which is a common hydraulic power source, compared with the case of driving by separate driving sources as in the first embodiment. Thus, the configuration can be simplified.

In this embodiment, in the initial state where the solenoid 110 of the hydraulic control valve 107 for changing the operation angle is turned off (duty ratio is 0%), the operation angle of the intake valve becomes the minimum operation angle. It is set as follows.

As in the first embodiment, a potentiometer 53 is used as the actual operating angle detecting means.

Further, in the second embodiment, the hydraulic control valve 79 'for the phase changing mechanism 70 has a configuration using the duty solenoid (110), similarly to the hydraulic control valve 107 for the operating angle changing mechanism 10. And hydraulic chambers 75, 76 before and after a helical gear 73 as a hydraulic actuator.
(FIG. 4), and the hydraulic pressure supplied to these hydraulic chambers 75, 76 is duty-controlled by a hydraulic control valve 79 '. The target phase of the center phase of the operating angle of the intake valve is set so as to be selected from three or more values including the intermediate phase, so that finer phase control can be performed.

Next, a control flow according to the second embodiment will be described with reference to a flowchart of FIG. Note that, for the same processes as those in the flowchart of FIG.

First, at S21, engine operating conditions such as an engine speed, an intake air amount, and an actual operating angle (≒ control shaft angle) are taken. Next, in S22, it is determined whether the potentiometer 53 as the actual operating angle detecting means is normal or abnormal based on the actual operating angle.

If it is determined that the engine is normal, the process proceeds to S23, and the target operating angle is determined by referring to the normal operating angle map A1 '(FIG. 9) according to the engine operating state. In S24,
The operating angle of the intake valve is feedback-controlled to the target operating angle based on the actual operating angle. That is, based on the amount of deviation between the target operating angle and the actual operating angle, the hydraulic control valve 107 for changing the operating angle is used.
The duty ratio of the drive pulse output to the solenoid 110 is determined.

Next, in S25, a normal phase map A2 '(not shown) is referred to based on the engine operating state.
The target phase of the operating angle center phase is determined. In S26, the duty ratio of the drive pulse output to the solenoid of the phase change hydraulic control valve 79 'is determined. The drive of the hydraulic control valve 79 'is controlled in accordance with the duty ratio, and the operating angle center phase by the phase changing mechanism 70 is controlled.

If it is determined in S22 that the potentiometer 53 is abnormal, the process proceeds to S27, and a target operating angle is determined with reference to an abnormal-time operating angle map B1 '(FIG. 9) different from the normal operation. That is, such a potentiometer 5
At the time of abnormality 3, the feedback control cannot be performed based on the actual operating angle, but since the movement range of the hydraulic piston 104 that rotationally drives the control shaft 16 is restricted,
By switching the driving direction of the hydraulic piston 104, it is possible to maintain the operating angle at either the minimum operating angle or the maximum operating angle. That is, it is possible to switch to either the minimum operating angle or the maximum operating angle by the open loop control. Therefore, in S27, the maximum operating angle or the minimum operating angle is selected as the target operating angle according to the engine operating conditions.

In S28, it is determined whether the target operating angle set in S27 is the minimum operating angle. In the case of the minimum operation angle, the process proceeds to S29, and a target phase of the operation angle center phase is determined with reference to a phase map B2 '(not shown) for an abnormal case different from the normal operation. Based on this target phase, S3
At 0, the duty ratio of the drive pulse output to the solenoid of the phase change hydraulic control valve 79 'is determined.

If it is determined in step S28 that the target operating angle is not the minimum operating angle, that is, it is determined that the target operating angle is the maximum operating angle, the process proceeds to step S31, where the hydraulic pressure defined before and after the helical gear 73 of the phase changing mechanism 70 is determined. The oil pressure in the chambers 75 and 76 is maintained to prevent the oil pressure from fluctuating. Specifically, the duty ratio of the drive pulse of the phase changing solenoid of the hydraulic control valve 79 'is held at an intermediate value.

To explain this point in detail, at the maximum operating angle, the valve lift is large and the valve reaction force is large, so that the reaction force acting on the swing cam 20 is large and the fluctuation torque applied to the control shaft 16 is large. Becomes larger. Therefore, a high oil pressure is required to stably hold the control shaft 16. At such a maximum operating angle, to temporarily drive the phase changing mechanism 70, the phase changing hydraulic chambers 75 and 76 are used.
When one of the hydraulic pressures is increased, the hydraulic pressure used on the side of the operating angle changing mechanism 10 from the oil pump 80, which is a common drive source, fluctuates or decreases, and the operating angle is changed to the maximum operating angle by the operating angle changing mechanism 10. May be difficult to stably hold. Therefore, in the present embodiment, if it is determined in S28 that the maximum operating angle has been selected as the target operating angle, the process proceeds to S30, in which the hydraulic pressure in the hydraulic chambers 75 and 76 for driving the phase changing mechanism 70 is held (locked). I do. That is, an increase in the hydraulic pressure on the phase changing mechanism 70 side is prohibited. Thereby, the stability of the state where the maximum operation angle is maintained by the operation angle changing mechanism 10 can be improved.

Next, referring to FIG. 9, the setting of the target operating angle in the normal state and the abnormal state will be described in further detail. In the low load range, the required intake air amount is small and the IVC
I would like to improve fuel efficiency by making the intake valve close timing relatively earlier, reducing intake air near the intake valve close timing, and opening the throttle to reduce pumping loss. For this reason, the operating ranges Amin and Bmin in which the target operating angle is the minimum operating angle are set to be relatively wide on the low load side in both normal and abnormal times. However,
Large output (torque) with such minimum operating angle setting
Not suitable for getting

When the potentiometer 53 is unable to finely control the operating angle as described above,
It is more desirable to ensure engine output than fuel efficiency. Therefore,
As shown in FIG. 9, the maximum engine speed Neb in the operating region Bmin where the target operating angle is set to the minimum operating angle when an abnormality occurs.
Is the operating region A in which the target operating angle is the minimum operating angle in a normal state.
min is set lower than the maximum engine speed Nea. This makes it possible to secure a sufficient output from a lower rotational speed (Neb) than in a normal state in a low load range in an abnormal state.

FIG. 12 shows another example of setting the target operating angle at the time of abnormality. As described above, at the time of abnormality, it is desirable to switch from a relatively low rotational speed to the maximum operating angle to secure output. However, when the engine speed is low as described above, the hydraulic pressure supplied from the oil pump 80 is also low, and therefore, there is a concern that the responsiveness when the operating angle is changed may be reduced. Particularly when the oil temperature of the hydraulic oil is high, it becomes more difficult to secure the hydraulic pressure. Therefore, assuming worst-case conditions in which the oil temperature is high and the oil pressure is low (the engine speed is low), the switching line b2 between the region of the minimum operation angle and the region of the maximum operation angle is set. The engine speed switched to the region becomes relatively high. That is, the engine rotation range using the minimum operation angle is relatively widened, and the operation range using the maximum operation angle at which high output is obtained is reduced.

Therefore, in the example shown in FIG. 12, the switching line between the minimum operation angle and the maximum operation angle is changed between b2 and b3 according to the temperature of the hydraulic oil. Specifically, the engine speed at which the target phase is switched to the minimum operating angle or the maximum operating angle is set to a low rotation side (b3) when the oil temperature is low,
It is shifted to the high rotation side (b2) as the temperature of the hydraulic oil rises. As a result, when the operating oil temperature is relatively high, the engine speed (b2) for switching between the minimum operating angle and the maximum operating angle is increased, so that the engine speed range for selecting the minimum operating angle is substantially. The stability of the engine is ensured. On the other hand, when the operating oil temperature is relatively low, the engine speed at which the target operating angle is switched (b3)
Is relatively low, and the engine speed range for selecting the maximum operation angle is substantially expanded, so that high output can be secured in a wide engine speed range.

[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 a first embodiment of the present invention.

FIG. 2 is a sectional view showing the operation angle changing mechanism of FIG. 1;

FIG. 3 is a partially cutaway side view showing the operation angle changing mechanism of FIG. 1;

FIG. 4 is a sectional view showing the phase changing mechanism of FIG. 1;

FIG. 5 is a potentiometer of FIG. 1 (actual operating angle detecting means);
FIG.

FIG. 6 is a configuration diagram showing a potentiometer.

FIG. 7 is a graph showing the relationship between the output value of the potentiometer and the operating angle of the intake valve.

FIG. 8 is a flowchart showing a control flow according to the first embodiment.

FIG. 9 is an explanatory diagram showing an operating angle map for setting a target operating angle in a normal state and an abnormal state.

FIG. 10 is a configuration diagram showing a configuration of a drive unit of an operating angle changing mechanism according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing a control flow according to the second embodiment.

FIG. 12 is an explanatory diagram showing another example of an operating angle map for setting a target operating angle at the time of abnormality.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Operating angle changing mechanism 12 ... Intake valve 53 ... Potentiometer (actual operating angle detecting means) 54 ... Control unit (abnormality determining means, control means) 70 ... Phase changing mechanism 79 (79 ') ... Hydraulic control valve 80 ... Oil pump (Hydraulic source) 107 ... Hydraulic control valve

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takanobu Sugiyama Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture 72) Inventor Shin Nakamura 1370 Onna, Atsugi-shi, Kanagawa Prefecture F-term in Unisia Gex Co., Ltd. AB02 DA01 DA02 DA05 DG05 DG08 EC04 FA02 FA11 FA24 FB05 GA05 GA17 HA01Z HA13Z HE01Z

Claims (4)

[Claims] An operating angle changing mechanism capable of changing an operating angle of an intake / exhaust valve in a range from a minimum operating angle to a maximum operating angle; a phase changing mechanism capable of changing a center phase of the operating angle with respect to a crankshaft; Actual operating angle detecting means for detecting the actual operating angle of the intake / exhaust valve; abnormality determining means for determining whether the actual operating angle detecting means is normal or abnormal; and control means for controlling the operating angle changing mechanism and the phase changing mechanism. This control means, when the actual operating angle detection means is determined to be normal,
A target operating angle is set from the maximum operating angle, the minimum operating angle, and one or more intermediate operating angles according to the engine operating condition, and the operating angle of the intake / exhaust valve is set to the target operating angle based on the actual operating angle. Feedback control, when the actual operating angle detecting means is determined to be abnormal,
Depending on the operating state of the engine, either the maximum operating angle or the minimum operating angle is set to the target operating angle, and the operating angle of the intake / exhaust valve is controlled to the target operating angle by open-loop control.
A variable valve train for an internal combustion engine, wherein the central phase is controlled based on a target operating angle at the time of this abnormality. 2. The system according to claim 1, wherein both the operating angle changing mechanism and the phase changing mechanism are driven in accordance with operating oil pressure supplied from a common oil pressure source. The variable valve train of an internal combustion engine according to claim 1, wherein when set to, the increase in the operating oil pressure supplied from the oil pressure source to the phase changing mechanism is prohibited. 3. The maximum engine speed in the operating region where the target operating angle is the minimum operating angle in the abnormal state is set lower than the maximum engine speed in the operating region where the target operating angle is the minimum operating angle in the normal state. The variable valve device for an internal combustion engine according to claim 1 or 2, wherein 4. The engine speed at which the target operating angle is switched to the minimum operating angle or the maximum operating angle at the time of the abnormality is increased with an increase in the temperature of the hydraulic oil.
3. The variable valve train for an internal combustion engine according to claim 1.