JP3382491B2 - Engine valve timing control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an engine suitable for variably controlling the opening / closing timing of an intake valve or an exhaust valve in accordance with the operating state of the engine.

[0002]

2. Description of the Related Art Generally, an engine valve timing control device which variably controls the opening / closing timing of an intake valve or an exhaust valve according to the operating state of an automobile engine is disclosed in, for example, Japanese Patent Laid-Open No. 6-2516. Are known.

A valve timing control system for an engine according to this type of prior art will be described with reference to FIGS. 7 to 14.

In the figure, reference numeral 1 denotes an engine crankshaft. The crankshaft 1 is rotatably provided on an engine body (not shown), and a small diameter pulley 1A is integrally attached to one end side thereof. Further, the crankshaft 1 is provided with a crank angle sensor 11, which will be described later, for detecting the rotational phase α thereof.

Reference numeral 2 is a drive shaft for transmitting the rotational driving force of the crankshaft 1 to the side of a camshaft 4 which will be described later.
The drive shaft 2 has an axis O1 -O on the engine body side.
The large-diameter pulley 2A of the drive shaft 2 is rotatably provided about 1 and is connected to the small-diameter pulley 1A of the crankshaft 1 via a timing belt 3, for example.

Reference numeral 4 denotes a camshaft for opening and closing an intake valve (not shown) provided in each cylinder of the engine. The camshaft 4 has an axis O1 on the engine body side.
It is rotatably provided around -O1 and its rotational phase β is detected by a cam position sensor 12 described later. When the camshaft 4 is rotationally driven by the crankshaft 1 via the drive shaft 2 and an eccentric disc 9 described later, etc., when the rotational phase β becomes a predetermined rotational phase determined according to the intake stroke of each cylinder. , Cams 4A, 4
The intake valves are opened and closed by A ,.

Reference numeral 5 designates the drive shaft 2 and the eccentric disc 9
A connecting plate which is provided on the other end side of the drive shaft 2.
Rotates integrally with. An engaging groove 5A extending in the radial direction is formed in the connecting plate 5, and an engaging pin 9A of the eccentric disc 9 is engaged with the engaging groove 5A.

Reference numeral 6 denotes another connecting plate provided on one end side of the camshaft 4, and an engaging groove 6A extending in the radial direction is formed in the connecting plate 6, and an eccentric disc 9 is formed in the engaging groove 6A. The engagement pin 9B is engaged.

Reference numeral 7 denotes an eccentric mechanism as a rotation phase varying means for changing the opening and closing timings of the intake valves. The eccentric mechanism 7 is, as shown in FIG. 8, a disc holder 8, an eccentric disc 9 and a control which will be described later. Shaft 1
0 and driving means such as an electromagnetic actuator (not shown).

The eccentric mechanism 7 decenters the center O2 of the eccentric disc 9 with respect to the center O1 of the camshaft 4 by an eccentric amount ε, whereby the rotational phase β of the camshaft 4 is rotated by the rotational phase α of the crankshaft 1. In contrast, relative changes are made as will be described later, and a phase difference Φ is generated between these rotational phases α and β.

Reference numeral 8 denotes a disk holder in which an eccentric disk 9 is rotatably accommodated. One end side of the disk holder 8 is an annular portion 8B swingably attached to the engine body side via a fixing pin 8A, and the annular portion 8B. It is composed of a pair of engaging claws 8C, 8C integrally formed on the other end side of the portion 8B.

Reference numeral 9 designates the drive shaft 2 and the cam shaft 4
FIG. 7 shows an eccentric disc connected to the eccentric disc. As shown in FIG.
And an engaging pin 9B projectingly formed on the other side surface. The engaging pins 9A and 9B are, as shown in FIG.
Are arranged at positions facing each other in the radial direction with the center O2 therebetween.

The eccentric disc 9 is a disc holder 8
Is accommodated rotatably about the axis O2-O2 in the annular portion 8B, and the engaging pins 9A and 9B are connected plates 5 and 6 respectively.
Are slidably engaged in the engaging grooves 5A and 6A. As a result, the drive shaft 2 and the cam shaft 4 are
The connecting plates 5 and 6 and the eccentric disc 9 are connected to each other, and in this state, the eccentric disc 9 is relatively displaceable between the connecting plates 5 and 6 in the radial direction of the camshaft 4 (drive shaft 2). .

Reference numeral 10 denotes a control shaft for making the eccentric disc 9 eccentric.
Is rotatably provided on the engine body side, and its cam 10
A is slidably disposed between the engaging claws 8C of the disc holder 8. And the control shaft 10
The cam 10 is rotated by the electromagnetic actuator or the like.
Through A, the disc holder 8 is swung together with the eccentric disc 9 around the fixing pin 8A as shown by the chain double-dashed line in FIG.

As a result, the eccentric mechanism 7 gives the eccentric disc 9 an eccentric amount ε according to the turning angle τ of the control shaft 10, and a phase difference Φ corresponding to the eccentric amount ε with respect to the rotation of the crankshaft 1. It is generated between the phase α and the rotation phase β of the camshaft 4.

Reference numeral 11 denotes a crank angle sensor which constitutes a phase difference detecting means together with the cam position sensor 12, and the crank angle sensor 11 when the rotational phase α of the crankshaft 1 reaches a predetermined rotational phase as shown in FIG. To detect this,
As shown in FIG. 13, the reference signal S1 is output as a detection signal.

Reference numeral 12 denotes a cam position sensor provided on the camshaft 4 side. The cam position sensor 12 detects this when the rotation phase β of the camshaft 4 reaches a predetermined rotation phase as shown in FIG. Then, as shown in FIG. 13, the reference signal S
2 is output as a detection signal.

The crank angle sensor 11 and the cam position sensor 12 are so constructed as to output the reference signals S1 and S2, respectively, while the camshaft 4 makes one revolution (360 °). When the eccentric mechanism 7 causes a phase difference Φ between the crankshaft 1 and the camshaft 4,
The reference signal S2 of the cam position sensor 12 is relatively displaced from the position synchronized with the reference signal S1 of the crank angle sensor 11 by a phase difference .PHI., As shown by S2 'in FIG. Based on the time T between and the engine speed N, the phase difference Φ is

[0019]

[Formula 1] Φ = k × T × N Is detected (where k is a constant).

On the other hand, the crank angle sensor 11 and the cam position sensor 12 are connected to a control unit (not shown) as a control means. The control unit measures the time T between the reference signals S1 and S2 'to detect the phase difference .PHI. Based on the equation (1), and based on the detected value, the rotation angle .tau. And the rotation angle τ of the control shaft 10 is feedback-controlled by operating the electromagnetic actuator.

The engine valve timing control device according to the prior art has the above-mentioned structure, and its operation will be described below.

First, the crankshaft 1 is driven by the engine.
When rotationally driven, the rotational driving force is transmitted to the drive shaft 2 via the timing belt 3 and is transmitted to the eccentric disc 9 via the connecting plate 5 and the engaging pin 9A of the eccentric disc 9. As a result, the eccentric disc 9
Rotates in the disc holder 8 in the direction of arrow A in FIG. 8, and this rotational driving force is applied to the engagement pin 9B of the eccentric disc 9.
Is transmitted to the camshaft 4 via the connection plate 6 and the camshaft 4 opens and closes the intake valves when the rotation phase β reaches a predetermined rotation phase.

When the control shaft 10 is rotated by the electromagnetic actuator when the opening / closing timing of the intake valve is changed, the eccentric disc 9 is moved between the connecting plates 5 and 6 in the radial direction of the cam shaft 4 as shown in FIG. Due to relative displacement, the axis O2 -O2 is eccentric from the axis O1-O1 of the camshaft 4 by an eccentric amount ε.

As a result, the rotational phase β of the camshaft 4 is displaced relative to the rotational phase α of the crankshaft 1 by the phase difference Φ, and the opening / closing timing of the intake valve opened / closed by the camshaft 4 depends on the phase difference Φ. Change,
By changing the phase difference Φ to a desired value, the opening / closing timing of the intake valve can be appropriately controlled.

That is, for example, as shown in FIG. 12, when the eccentric disc 9 is eccentric by the eccentric amount ε 1 (ε 1> ε), when the crankshaft 1 (drive shaft 2) reaches the rotational phase α, the eccentric disc 9 is rotated. 9 rotates about the center O2 by an angle .gamma., But at this time, the camshaft 4 is rotated around the center O1 by the engaging pin 9B of the eccentric disc 9, and its rotation phase .beta. Become.

The rotation phase α of the crankshaft 1
And a rotational phase β of the camshaft 4 have a phase difference Φ defined by the following equation.

[0027]

[Formula 2] Φ = α−β

As shown in FIG. 11, the characteristic line of the phase difference Φ has a waveform close to a sine wave having a cycle of one rotation (360 °) of the camshaft 4, and changes periodically according to the rotation phase β. To do. Further, the waveform of the phase difference Φ changes according to the eccentricity amounts ε and ε1 of the eccentric disc 9 as shown by characteristic lines 13 and 14.

Here, the phase difference Φ between the crankshaft 1 and the camshaft 4 corresponds to the eccentricity ε of the eccentric disc 9 (the rotation angle τ of the control shaft 10) as shown by the characteristic lines 13 and 14 in FIG. Therefore, by detecting the phase difference Φ, the rotation angle τ at which the control shaft 10 is actually rotated can be obtained.

On the other hand, a method of directly detecting the rotation angle τ of the control shaft 10 with a contact sensor such as a potentiometer may be considered, but the reliability of the valve timing control device is maintained in consideration of its durability and the like. Becomes difficult.

Therefore, in the prior art, the control unit detects the phase difference Φ based on the reference signals S1 and S2 from the crank angle sensor 11 and the cam position sensor 12, and the control shaft 10 actually rotates based on the detected value. The calculated rotation angle τ is calculated by a non-contact method. Then, the target value τ0 of the rotation angle τ of the control shaft 10 is calculated based on the engine speed, for example, and the control shaft 10 is feedback-controlled so that the calculated value of the rotation angle τ becomes the target value τ0.

[0032]

By the way, in the above-mentioned prior art, since the crankshaft 1 and the camshaft 4 are mechanically connected via the drive shaft 2 and the timing belt 3, etc., these connecting portions are connected. May cause rattling or bending of the timing belt 3.

For example, when the timing belt 3 bends as shown by the chain double-dashed line in FIG. 9, the rotational phase α of the crankshaft 1 is displaced from the rotational phase β of the camshaft 4 by a phase deviation θ. As shown in 13, the reference signal S1 of the crank angle sensor 11 is relatively displaced with respect to the reference signal S2 of the cam position sensor 12 to the position of the reference signal S1 'shown by the chain double-dashed line.

As a result, the time T'between the reference signals S1 'and S2' becomes longer than the time T'between the reference signals S1 and S2 'by the time Ts corresponding to the phase deviation .theta. On the basis of the above, the phase difference Φ detected by the equation 1 becomes a larger value than the phase difference Φ when the phase deviation θ is not generated (hereinafter, referred to as the normal phase difference Φ 0).

That is, as shown in FIG. 14, the characteristic line 15 of the phase difference Φ is a value that is drifted by the phase deviation θ with respect to the characteristic line 16 of the normal phase difference Φ 0 generated by actually rotating the control shaft 10. Therefore, if the rotation angle τ of the control shaft 10 is calculated based on this detected value, a value different from the actual rotation angle τ will be calculated.

Therefore, in the prior art, the actual rotation angle τ
Since the control shaft 10 cannot be accurately feedback-controlled so that becomes the target value τ 0, it is difficult to appropriately change the opening / closing timing of the intake valve.

The present invention has been made in view of the above-mentioned problems of the prior art. Even if the detected value of the phase difference deviates from the normal phase difference, the present invention can accurately detect the normal phase difference from the detected value. It is an object of the present invention to provide a valve timing control device for an engine, which can be obtained by calculation and can perform feedback control while stabilizing the rotational phase difference varying means.

[0038]

In order to solve the above-mentioned problems, the present invention provides a crankshaft, a camshaft which is rotationally driven by the crankshaft and opens and closes a valve for intake or exhaust, and a camshaft for the valve. Rotation phase varying means for varying the rotation phase of the camshaft to produce a phase difference between the rotation phases of the crankshaft and the camshaft in order to change the opening / closing timing, and the crankshaft and the camshaft by the rotation phase varying means. A phase difference detecting means for detecting a phase difference generated between the phase difference detecting means and the phase difference detecting means, and a control means for feedback-controlling the rotation phase varying means based on at least the detection result of the phase difference by the phase difference detecting means. It is applied to the valve timing control device of an engine.

The feature of the configuration adopted by the invention described in claim 1 is that the control means sets the rotation phase of the camshaft to a predetermined first rotation phase or second rotation phase. Reading means for reading the first detection value and the second detection value from the phase difference detecting means, a normal phase difference to be generated between the crankshaft and the camshaft, and the normal phase difference. To the phase difference calculation means for calculating the phase deviation from the first detection value and the second detection value by the reading means, and the operation amount of the rotation phase varying means from the normal phase difference by the phase difference calculation means. An operation amount calculation means, a signal output means for outputting a control signal to the rotation phase varying means so that a calculated value of the operation amount by the operation amount calculation means becomes a value corresponding to a target value; Determination means for determining whether or not the detected value excessively changes by comparing the detected value with the second detected value. When it is determined that the change is excessive, the normal phase difference is corrected and calculated based on the phase deviation calculated in the previous calculation.

According to the above construction, when the camshaft reaches the first rotation phase and the second rotation phase, the first detection value and the second detection value read by the reading means are used as phase difference calculating means. By performing the comparison calculation according to, the phase deviation in which the respective detected values are biased with respect to the normal phase difference can be calculated, and the normal phase difference can be calculated based on the calculated value of the phase deviation and the respective detected values. Since the operation amount calculating means can calculate the operation amount of the rotation phase varying means actually based on the calculated value of the normal phase difference, the signal output means determines that the calculated value of the operation amount corresponds to the target value. The rotation phase varying means can be feedback-controlled so that Further, when the operation amount of the rotation phase varying means is changed by the signal output means, the first detection value and the second detection value suddenly change accordingly, and when the detection values greatly change, the normal position is changed. It becomes difficult to calculate the phase difference accurately. Therefore, the determination means compares the detected values to determine whether or not they have excessively changed, and if they have excessively changed, the regular phase difference is calculated using the previously calculated phase deviation. By performing the correction calculation by the phase difference calculation means, the calculation accuracy of the regular phase difference can be improved.

According to the second aspect of the invention, the first rotational phase is relative to the rotational position of the camshaft at which the regular phase difference becomes substantially zero during one revolution of the camshaft. To a rotational position shifted by a certain angle to the front side of the rotational phase, and the second rotational phase is shifted from the rotational position of the camshaft by the certain angle to the rear side of the rotational phase. The rotational positions are shifted from each other, and the phase difference calculation means reads the first reading value by the reading means during at least two rotations of the camshaft until the determination means determines that the detected value excessively changes.
The latest phase deviation is calculated from the detected value and the second detected value, and the normal phase difference is calculated based on the phase deviation and the detected value, and the judgment means judges that the detected value excessively changes. In this case, the normal phase difference is corrected and calculated based on the first detection value, the second detection value and the phase deviation calculated in the previous calculation.

As a result, the first rotational phase and the second rotational phase are brought into symmetrical rotational positions before and after the rotational position of the camshaft where the normal phase difference becomes substantially zero. Can be set. Further, until the determination unit determines that the detection value has excessively changed, either one of the first detection value and the second detection value is read while the camshaft rotates at least two times, An estimated value corresponding to the other detected value can be estimated and calculated based on the one detected value. Then, by setting the first rotational phase and the second rotational phase at symmetrical rotational positions as described above, when the detected value of the phase difference does not include the phase deviation with respect to the regular phase difference, The absolute value of the estimated value and the detected value of the other becomes substantially equal. Then, by utilizing this, the estimated value and the other detected value are compared and calculated to calculate the phase deviation between the first detected value, the second detected value and the normal phase difference. The normal phase difference can be calculated based on Further, when the determination unit determines that the detected value has excessively changed, the normal phase difference can be corrected and calculated based on the previous phase deviation calculated so far and each detected value from the reading unit.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

1 to 6 show an embodiment of the present invention. In this embodiment, the same components as those of the prior art are designated by the same reference numerals and the description thereof will be omitted.

In the figure, reference numeral 21 denotes a control unit which constitutes the control means of the valve timing control device for an engine according to this embodiment, and the control unit 21 is a storage area 21A comprising, for example, ROM, RAM, etc., as in the prior art. The crank angle sensor 11 and the cam position sensor 12 are connected to the input side thereof, and the electromagnetic actuator 22 described later is connected to the output side thereof.

In the memory area 21A of the control unit 21, a valve timing control processing program (see FIGS. 2 to 4), which will be described later, is rotated together with the control shaft 10 so as to rotate in accordance with the operating state of the engine. The target value τ 0 of the angle τ is stored as a characteristic map according to, for example, the engine speed and the basic injection amount. In the storage area 21A, a calculation map for calculating the rotation angle τ of the control shaft 10 from the phase difference Φ between the crankshaft 1 and the camshaft 4 (more accurately, the normal phase difference Φ 0), and a later-described calculation map. The allowable limit L and the like are stored.

Reference numeral 22 is an electromagnetic actuator for rotating the control shaft 10. The electromagnetic actuator 22 is composed of a linear stepping motor or the like, and responds to a drive signal output from the control unit 21 almost in the same manner as in the prior art. The control shaft 10 is rotated.

The engine valve timing control system according to the present embodiment has the above-described structure, and will be described with reference to FIG.
The operation will be described with reference to FIGS.

First, when the control unit 21 determines that the engine is in the operating state in which the valve timing control should be performed based on the engine speed or the like, it starts the valve timing control process shown in FIGS. 2 to 4. Then, in step 1, initial values θ (1) and θ (2) of the phase deviation θ (n) calculated in step 2 are initialized to zero. Note that the count value n (n = 1, 2, 3, ...) Is the rotational phase β of the camshaft 4 after the start of the valve timing control.
Is incremented by "1" every time the first and second rotational phases β1 and β2 described later are reached.

Next, in step 2, as in steps 11 to 31 described later shown in FIGS. 3 and 4, the phase difference Φ is read and calculated to calculate the rotation angle τ of the control shaft 10. The required normal phase difference Φ 0 is used as the calculated values A (n) and B (n + 1), and the detected value a of the phase difference Φ
It is obtained from (n) and b (n + 1) as described later.

Then, in step 3, the calculated values A (n) and B (n +) of the normal phase difference Φ 0 calculated in step 2 are calculated.
Based on 1), the rotation angle τ of the control shaft 10 is calculated from the calculation map or the like in the storage area 21A. Thereby, the rotation angle τ of the control shaft 10 actually rotated by the electromagnetic actuator 22 is obtained.

Next, at step 4, in order to perform feedback control of the control shaft 10, for example, a storage area 21A based on the engine speed and the basic injection amount, etc.
The target value τ0 for the rotation angle τ of the control shaft 10 is calculated from the characteristic map in the above, and the difference between the target value τ0 and the rotation angle τ of the control shaft 10 obtained in step 3 is set to a predetermined hysteresis value or less. The control amount of the electromagnetic actuator 22 required for this is calculated.

Then, in step 5, a drive signal corresponding to the control amount calculated in step 4 is output to the electromagnetic actuator 22, and the turning angle τ of the control shaft 10 is substantially set to the target value τ by the electromagnetic actuator 22.
Rotate to 0.

As a result, the rotational phase β of the camshaft 4
Is the rotation angle τ of the control shaft 10 (target value τ0
) Corresponding to the phase difference Φ corresponding to the rotational phase α of the crankshaft 1, and the camshaft 4 can open and close the intake valves at appropriate timings corresponding to the engine speed and the like.

Next, in step 6, it is judged whether or not the above-mentioned valve timing control is in an operating state in which it should be continued based on, for example, the engine speed, and when it is judged as "YES", steps 2 to 5 are executed. By repeating the above process, feedback control is performed so that the rotation angle τ of the control shaft 10 always becomes a value corresponding to the target value τ 0.

If "NO" is determined in step 6, it means that the condition for stopping the valve timing control is satisfied, for example, when the engine speed becomes high, so that the process proceeds to step 7. The valve timing control ends.

As a result, when the valve timing control is continued as described above, the phase difference Φ periodically changes according to the rotation phase β of the camshaft 4, as shown by the solid line in FIG. 5, for example. As described in the prior art, the phase difference Φ is larger than the normal phase difference Φ 0 shown by the dotted line by the phase deviation θ (n) due to the bending of the timing belt 3 or the like. Also, the regular phase difference Φ 0 is
The waveform is substantially symmetrical with respect to the rotational phase β of the camshaft 4 about a zero point position P0 described later.

FIG. 5 shows a case where feedback control is performed so that the maximum value (minimum value) of the normal phase difference Φ 0 increases at a constant rate with respect to the rotation of the camshaft 4.
In this case, as shown in FIG. 6, the normal phase difference Φ 0 has its calculated values A (n), B (n−1), etc. located on the characteristic line indicated by the dotted line, and the detected value a ( n), b (n
-1) and the like are positioned on the characteristic lines obtained by moving the characteristic line of the normal phase difference Φ 0 upward and downward by the phase deviation θ (n). However, the detected value b (n-1) in FIG.
b (n-3) and calculated values B (n-1), B (n-3)
Is a value after the absolute value processing described later.

Next, referring to FIGS. 3 and 4, the phase difference Φ
The read calculation processing of will be described. Note that a (n),
b (n + 1) indicates the first and second detection values of the phase difference Φ,
A (n) and B (n + 1) are detected values a (n) and b (n +).
The calculated value of the regular phase difference Φ 0 corresponding to 1) is shown. However, the estimated values a (n-1), b (n), which are not located on the characteristic line of the phase difference Φ (regular phase difference Φ 0) in FIG.
A (n-1) and B (n) are estimated and calculated as described below.

First, in steps 11 and 12 in FIG. 3, the first and second detection values a (n) and b (n +
In order to detect the timing of reading 1), it is determined whether or not the rotation phase β of the camshaft 4 has reached the first and second rotation phases β1 and β2. Here, the first and second rotational phases β1 and β2 are the rotation of the camshaft 4 in which the regular phase difference Φ0 shown by the dotted line in FIG. 5 is substantially zero during one rotation of the camshaft 4. If the zero point position P0 is 180 °, it is determined in advance as a rotational position that is shifted in phase by a certain angle (for example, 90 °) before and after the position (hereinafter referred to as zero point position P0). β1 is 90
The second rotational phase β2 is set to 270 °.

When the determination in step 11 is "YES", the rotational phase β of the camshaft 4 has reached the first rotational phase β 1, so the process proceeds to steps 13 to 21 to detect the detected value a (n). The calculated value A (n) is calculated.

If "NO" is determined in step 11, the process proceeds to step 12 to perform the second rotation phase β2 determination process. Then, in step 12, "YE
When it is determined to be “S”, the rotation phase β of the camshaft 4
Has reached the second rotation phase β2, the process proceeds to steps 22 to 31 in FIG. 4 to calculate the calculated value B (n + 1) from the detected value b (n + 1). In step 12, "N
When it is determined to be “O”, the rotation phase β of the camshaft 4
The determination processing of step 11 and step 12 is repeated until becomes the rotation phase β1 or the rotation phase β2.

Here, the processing performed in steps 13 to 21 will be described by taking the case where the phase difference Φ changes as shown in FIG. 5 as an example.
When the rotational phase β of the first rotational phase β reaches the first rotational phase β 1, the phase difference Φ calculated by the crank angle sensor 11 and the cam position sensor 12 from the above formula 1 is read as the first detected value a (n). Put in.

Next, in step 14, the detected value a (n)
Based on the detected value a (n−2) of the previous two times, the change width Δa (n) of the detected value a (n) changed during one rotation of the camshaft 4 is calculated by the following formula.

[0065]

## EQU3 ## Δa (n) = a (n) -a (n-2)

Then, in step 15, the change width Δb (n-1) calculated by the equation (12), which will be described later, is read when the previous detection value b (n-1) is read in step 24 in FIG. 16, the change widths Δa (n), Δb
The phase change rate ΔΦ is calculated by the following equation based on (n-1).

[0067]

[Equation 4]

Here, the phase change rate ΔΦ is the detected value a
(N), b (n-1) is a calculated value representing the state of change. For example, when the phase difference Φ increases at a constant rate as shown in FIG. 5, the change widths Δa (n), Δb ( n-1)
The phase change rate ΔΦ becomes zero when the two are equal.
When the rate of change of the phase difference Φ changes midway, the change widths Δa (n) and Δb (n−1) before and after the change have different values, and the phase change rate ΔΦ is a value corresponding to these differences. Becomes

Next, in step 17, the phase change rate ΔΦ
Is compared with the allowable limit L, the detected value a (n),
It is determined whether b (n-1) has changed excessively. Here, the allowable limit L is a predetermined value that is predetermined according to the detection accuracy of the crank angle sensor 11 and the cam position sensor 12 (phase difference Φ), the control accuracy of the electromagnetic actuator 22, and the like, and is, for example, 0.5. It is set to a value of about °.

If the phase change rate ΔΦ exceeds the allowable limit L, the detected values a (n) and b (n-1) have excessively changed, so that the phase deviation θ ( n) cannot be calculated accurately. Therefore, when the determination is “YES” in step 17, the phase change rate ΔΦ
Exceeds the allowable limit L, the phase deviation θ
The process proceeds to step 19 without calculating (n).

When it is determined to be "NO" in step 17, it is determined that the phase deviation θ (n) can be accurately calculated because the phase change rate ΔΦ is equal to or less than the allowable limit L, and the process proceeds to step 18 to be described later. The phase deviation θ (n) is calculated by the equations (5) to (9).

That is, in step 18, the detected value b (n-1) is compared with the detected value b (n-1) of the previous time.
The estimated value a (n-1) corresponding to (n-1) is converted into the detected value a
From (n) and the detected value a (n−2) two times before,

[0073]

[Equation 5] Estimate calculation as.

In this case, the estimated value a (n-1) is, as shown in FIG. 5, a straight line connecting the detected values a (n-2) and a (n) to t (n-1): It is a value internally divided by a ratio of t (n) (a value corresponding to the position of the rotation phase β2). Further, the time t (n) is an elapsed time from when the rotational phase β of the camshaft 4 reaches the previous rotational phase β2 (rotational phase β1) to when it reaches the current rotational phase β1 (rotational phase β2). The time t (n) is measured by the soft timer of the control unit 21 or the like.

The detected value a (n-2) is the calculated value A.
Deviate from (n-2) by the phase deviation θ (n-2),
Similarly, since the detected value a (n) is deviated from the calculated value A (n) by the phase deviation θ (n), the estimated value a (n-1) obtained based on these is the calculated value a (n). A (n-2), A
The phase deviation θ with respect to the estimated value A (n−1) obtained from the calculation similar to the equation 5 from (n)
Only (n) has a large value.

[0076]

## EQU6 ## a (n-1) = A (n-1) +. Theta. (N)

In this case, it can be considered that the phase deviation θ (n) due to the bending of the timing belt 3 is almost constant in a minute time such that the camshaft 4 makes two revolutions. Therefore, the phase deviation θ (n ), Θ (n−1), θ (n−
By regarding 2) as an equal value, the above equation 6 can be derived.

In step 18, the estimated value a (n-
In order to perform a comparative calculation with 1), the detection value b (n-1) read in step 22 when the rotation phase β of the camshaft 4 becomes the rotation phase β2 is read out after the processing in step 23.

Here, this detected value b (n-1) is deviated by the phase deviation θ (n) from the calculated value B (n-1) as in the case of the detected value a (n). However, the detected value b (n-
In 1), since the positive / negative is inverted by the absolute value processing in step 21, the calculated value B (n-1) becomes a value smaller by the phase deviation θ (n) as shown in the following equation.

[0080]

## EQU7 ## b (n-1) = B (n-1)-. Theta. (N)

Further, the normal phase difference Φ0 has a substantially symmetrical waveform with the zero point position P0 as the center as described above, and the first and second rotational phases β1 and β2 have the zero point position P0.
Since it is set symmetrically with respect to, the calculated value A (n-
2), the absolute value of the estimated value A (n-1) obtained from A (n) corresponding to the second rotational phase β2 and the calculated value B (n-1) is as follows: Will be equal.

[0082]

## EQU8 ## A (n-1) = B (n-1)

Accordingly, the equation for calculating the phase deviation θ (n) based on the estimated value a (n-1) and the detected value b (n-1) is given by Therefore, in step 18, the phase deviation θ
Calculate (n).

[0084]

[Equation 9]

On the other hand, in step 19, since the phase deviation θ (n) cannot be accurately calculated by the equations 5 to 9 in step 18, the phase deviation θ (n-1) previously calculated in step 18 is calculated this time. Substituting into the phase deviation θ (n) to be calculated, this step 20
The calculated value A (n) is corrected and calculated with.

Next, in step 20, the detected value a (n)
And the phase deviation θ (n), the calculated value A
(N) is calculated, and in step 21, the rotation angle τ of the control shaft 10 is calculated based on the calculated value A (n), and the process returns to step 3.

[0087]

## EQU10 ## A (n) = a (n)-. Theta. (N)

When the rotational phase β of the camshaft 4 reaches the rotational phase β1 for the first time after the start of the valve timing control, the process proceeds from step 13 to step 20 and the phase deviation θ (n ) Is used to initially calculate the calculated value A (n).

On the other hand, when the camshaft 4 further rotates and the rotation phase β reaches the second rotation phase β2,
In order to calculate the latest calculated value B (n + 1), the process moves from step 12 to step 22 shown in FIG. 4 and the same processing as steps 13 to 21 described above is performed.

Then, in step 22, the phase difference Φ is read as the detected value b (n + 1), and in step 23, the sign of this detected value b (n + 1) is inverted to obtain
b (n + 1) is treated as an absolute value.

Next, at step 24, the detected value b (n +
Based on 1) and the detected value b (n-1) two times before, the change width Δb (n + 1) of the detected value b (n) changed during one rotation of the camshaft 4 is calculated by the following formula.

[0092]

[Equation 11] Δb (n + 1) = b (n + 1) -b (n-1)

In this case, the previous change width Δb (n-1) read in step 15 in FIG. 3 is calculated as follows.

[0094]

[Equation 12] Δb (n-1) = b (n-1) -b (n-3)

Then, in step 25, the previous change width Δa (n) calculated in step 14 in FIG. 3 is read out,
In step 26, the change widths Δb (n + 1), Δa (n)
Based on the above, the phase change rate ΔΦ is calculated in the same manner as the equation (4).

Next, at step 27, the phase change rate ΔΦ
Of the current phase deviation θ (n +) in step 28 when it is determined to be “NO”.
1) is calculated in the same manner as in step 18. On the other hand, when it is determined to be “YES” in step 27, the phase deviation θ (n) of this time cannot be accurately calculated in step 28, and therefore the process proceeds to step 29.
After substituting (n) into the phase deviation θ (n + 1) to be calculated this time, the process proceeds to step 30.

Finally, in step 30, the detected value b (n
After calculating the calculation value B (n + 1) by adding the phase deviation θ (n + 1) to +1), the process returns to step 3 in step 31.

By the way, as shown by the solid line (dotted line) in FIGS. 5 and 6, when the control shaft 10 is feedback-controlled so that the phase difference Φ (normal phase difference Φ 0) increases at a constant rate, For example, when the increase rate of the phase difference Φ (normal phase difference Φ 0) increases from the position of the point P shown in FIG. 6 as indicated by the chain double-dashed line, the detected value a to be detected after the point P (N) is the difference d shown in the following formula
It increases only by this to become the detected value a '(n).

[0099]

## EQU13 ## a '(n) = a (n) + d

Now, the phase deviation θ (n) 'due to the detected value a' (n) will be calculated by the equations (5) and (9).

First, based on the detected values a '(n) and a (n-2), the estimated value a' (n-1) in FIG. 6 can be calculated by the equation (5) as follows. In this case, the time t
(N) and t (n-1) are regarded as almost the same time.

[0102]

[Equation 14]

Then, the detected value a ′ shown in the equation 13 is obtained.
Substituting (n) into the equation of the equation (14), t
Compared with the case where (n) = t (n-1),

[0104]

[Equation 15] Becomes Further, the estimated value a '(n-1) and the detected value b
From (n-1) and the equation (9), the phase deviation θ '
The calculation of (n) is as follows.

[0105]

[Equation 16]

On the other hand, as shown in FIG. 6, the change width Δ when the detected value a '(n) excessively changes from the detected value a (n-2).
a '(n) is

[0107]

## EQU17 ## Δa '(n) = a' (n) -a (n-2). Then, the equation of this Equation 17 and the above Equation 3
From the equation of

[0108]

## EQU18 ## d = Δa '(n) -Δa (n). Further, the variation width Δa (n) becomes Δa (n) = Δb (n−1) when the phase difference Φ increases at a constant rate, and becomes equal to the variation width Δb (n−1). Equation 18 is

[0109]

D = Δa '(n) -Δb (n-1) Is replaced by

Accordingly, when the phase deviation θ '(n) obtained by the equation 16 is substituted with the difference d obtained by the equation 19,

[0111]

[Equation 20] Becomes

Here, when the detected value a '(n) shown in FIG. 6 changes excessively, the phase change rate ΔΦ according to the equation (4) is

[0113]

[Equation 21] Therefore, the phase change rate ΔΦ according to the equation (21) and the phase deviation θ ′ (n) according to the equation (20) are

[0114]

[Equation 22] θ ′ (n) = θ (n) + ΔΦ Be introduced as a relationship.

That is, when the change rate of the phase difference Φ changes due to the rotation of the control shaft 10 or the like, even if the phase deviation θ (n) due to the bending of the timing belt 3 is constant, this phase deviation θ (n) is calculated as a phase deviation θ ′ (n) including an error corresponding to the phase change rate ΔΦ.

Then, based on the phase deviation θ '(n) and the detected value a' (n), the calculated value A "(n) calculated by the equation 10 in step 20 is the phase deviation θ (n )
And the calculated value A ′ to be calculated based on the detected value a ′ (n)
As compared with (n), the value is deviated by the phase change rate ΔΦ as shown in FIG. 6, and the rotation angle τ of the control shaft 10 calculated in step 3 based on the calculated value A ″ (n) is actually Will deviate from the rotation angle of.

Therefore, in steps 17 and 27, by comparing the phase change rate ΔΦ calculated in steps 16 and 26 with the allowable limit L, the phase deviation θ (n) when the change rate of the phase difference Φ changes. It is determined whether or not the error that occurs in 1 exceeds the allowable limit L corresponding to the detection accuracy of the phase difference Φ or the control accuracy of the electromagnetic actuator 22.

When the phase change rate ΔΦ exceeds the allowable limit L, a detectable or correction controllable error occurs in the phase deviation θ (n). Since the phase difference Φ 0 cannot be calculated accurately, for example, the phase deviation θ (n−1) previously calculated in step 19 is to be calculated this time.
By substituting into the calculated phase difference Φ, the normal phase difference Φ 0 is calculated as the calculated value A (n) based on the previous phase deviation θ (n−1) calculated before the phase difference Φ excessively changes. Thus, in this embodiment, when the rotational phase β of the camshaft 4 becomes the first and second rotational phases β1 and β2, the phase difference Φ is read and the first and second detection values a (n) are read. ), B
The phase deviations θ (n), θ (n + 1) and the calculated values A (n), B (n + 1) are calculated from (n + 1), and the calculated value A
The rotation angle τ of the control shaft 10 calculated based on (n) and B (n + 1) is feedback-controlled.

Then, for example, for the detected value a (n), the phase change rate Δ calculated from the detected values a (n), b (n-1), etc.
By determining whether Φ exceeds the allowable limit L,
It is determined whether or not these detected values a (n) and b (n-1) have changed excessively, and when these have changed excessively,
The previously calculated phase deviation θ (n−1) is substituted for the phase deviation θ (n) to be calculated this time, and the calculated value A (n) is corrected and calculated by this phase deviation θ (n−1).

Therefore, according to the present embodiment, the control shaft 10 is feedback-controlled to detect the detected value a.
Until (n) and b (n + 1) change excessively, even if the detected values a (n) and b (n + 1) include the phase deviation θ (n) with respect to the regular phase difference Φ 0, these detections are detected. Based on the values a (n) and b (n + 1), the phase deviation θ (n) can be accurately calculated by the equation (9), and the phase deviation θ (n)
The calculated value of the detected value a as shown in steps 20 and 30.
By removing from (n) and b (n + 1), the calculated values A (n) and B (n + 1) can be calculated with high accuracy.

That is, the first and second rotational phases β1 and β2 are set 90 ° before and after the zero point position P0 of the camshaft 4.
Is set as a rotational position whose phase is shifted by only, and detection values a (n) and b (n
Since the calculation values A (n) and B (n + 1) are calculated based on +1), for example, the previous calculation is performed based on the detection value a (n) and the detection value a (n−2) of the previous time. Estimated value a (n-1) and corresponding detected value b (n-1)
The phase deviation θ (n) can be accurately obtained by using the fact that the absolute values of the estimated value A (n-1) and the calculated value B (n-1) are equal by performing a comparison calculation of and.

Further, the detected values a (n) and b (n + 1) are obtained by feedback-controlling the control shaft 10.
Is excessively changed, and when the error (phase change rate ΔΦ) generated in the phase deviation θ (n) due to this change exceeds the allowable limit L, for example, the previous phase calculated before the detected value a (n) changes The calculated value A (n) can be accurately corrected and calculated by the deviation θ (n−1).

As a result, for example, even when a mechanical error occurs due to the bending of the timing belt 3 or the phase difference Φ changes transiently due to the rotation of the control shaft 10, the regular phase difference Φ 0 can be accurately adjusted. The control shaft 10 can be stably feedback-controlled based on the rotation angle τ calculated from the regular phase difference Φ 0.

In the above embodiment, steps 13 and 22 of the program shown in FIGS. 2 to 4 show concrete examples of reading means, and steps 18 to 20 and 28 to 30 show concrete examples of phase difference calculating means. Along with showing steps 14
Reference numerals 17 and 24 to 27 are specific examples of the determination means, step 3 is a specific example of the operation amount calculation means, and steps 4 and 5 are specific examples of the signal output means.

In the above embodiment, steps 17, 2
The judgment value to be compared with the phase change rate ΔΦ in 7 is the phase difference Φ
However, the present invention is not limited to this, and the average value of the detected values a (n) and b (n + 1) of the phase difference Φ detected over the past several times, for example. And the latest detected value a (n) with respect to this average value
Or, determine whether b (n + 1) has changed excessively,
If it changes excessively, the normal phase difference Φ 0 may be calculated from the previous phase deviation θ (n−1).

Further, in the above embodiment, the reference signals S1 and S2 of the crank angle sensor 11 and the cam position sensor 12 are used.
The rotational phase β, the phase difference Φ, etc. of the camshaft 4 calculated temporally by the above are converted into angles based on the engine speed. However, the present invention is not limited to this, and the crank angle sensor 11 or the like controls the angle. For example, an angle signal for each 1 ° may be output to the unit 21, and the rotation phase β, the phase difference Φ, or the like may be directly detected as an angle based on the angle signal.

Furthermore, in the above-described embodiment, the valve timing control device for controlling the opening / closing timing of the intake valve has been illustrated as the prior art, but the present invention is not limited to this, and either one of the intake valve and the exhaust valve may be used. Alternatively, it may be applied to a valve timing control device that controls both opening and closing timings.

[0128]

As described above in detail, according to the first aspect of the present invention, the phase difference calculating means calculates the phase deviation and the normal phase difference based on the first detection value and the second detection value. Then, based on this regular phase difference, the operation amount calculating means calculates the operation amount of the rotational phase varying means, and the determining means determines whether the phase difference excessively changes, and determines that the phase difference excessively changes. Since the normal phase difference is corrected and calculated based on the phase deviation calculated in the previous calculation, the first detected value, the first detected value, and the Even when the detected value of 2 includes the phase deviation with respect to the normal phase difference, this phase deviation can be reliably calculated from the first detected value and the second detected value, and the normal value can be calculated based on the calculated value of the phase deviation. The phase difference can be calculated accurately. When the determination means determines that the detected value has excessively changed, the normal phase difference is corrected and calculated using the previous phase deviation, so that the transition of the phase difference due to the operation of the rotational phase change means or the like occurs. It is possible to reliably prevent the change from being calculated as an error of the phase deviation. Therefore, even if the detected value includes a phase deviation with respect to the regular phase difference, or if it fluctuates transiently,
The phase deviation can be accurately calculated, the normal phase difference can be calculated with high accuracy based on the calculated value of the phase deviation, and the operation amount of the rotary phase varying means calculated based on the calculation result can be stably feedback-controlled. be able to.

According to the second aspect of the invention, the phase difference calculating means reads the camshaft during at least two revolutions until the judging means judges that the detected value has excessively changed. When the normal phase difference is calculated based on the first detection value and the second detection value and it is determined that the detection value has excessively changed, the first detection value, the second detection value and the previous phase deviation are calculated. Since the normal phase difference is corrected and calculated based on the above, until the detection value changes excessively, the second detection is performed based on the first detection value read while the camshaft makes two revolutions, for example. The estimated value corresponding to the value can be estimated and calculated, and the normal phase difference can be accurately calculated by comparing and calculating the estimated value and the second detected value. Further, when it is determined that the detection value has excessively changed by the determination means,
The correct phase difference can be accurately corrected and calculated based on the previous phase deviation calculated by the phase difference calculating means before the detected value excessively changes and the first detected value and the second detected value. It is possible to stably perform feedback control of the operation amount of the rotation phase varying means calculated based on the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing a valve timing control device for an engine according to an embodiment of the present invention.

FIG. 2 is a flow chart showing a control process of valve timing control by a control unit in FIG.

FIG. 3 is a flowchart showing a phase difference reading calculation process in FIG.

FIG. 4 is a flowchart showing a phase difference reading calculation process subsequent to FIG. 3;

FIG. 5 is a characteristic diagram showing a change in phase difference with respect to a rotation phase of a camshaft.

FIG. 6 is an explanatory diagram for obtaining a phase change rate and a normal phase difference from the detected value of the phase difference.

FIG. 7 is a partially cutaway front view showing a valve timing control device for an engine according to a conventional technique.

8 is a cross-sectional view taken along the arrow VIII-VIII in FIG. 7 showing an eccentric disc together with a control shaft and the like.

9 is a right side view in FIG. 7 showing a crankshaft, a camshaft, a crank angle sensor, a cam position sensor and the like.

FIG. 10 is an explanatory view showing a state where the eccentric disc in FIG. 8 is eccentric with respect to the cam shaft.

11 is a characteristic diagram showing a change in phase difference with respect to a rotational phase of a camshaft according to an eccentric amount of an eccentric disc in FIG.

FIG. 12 is an explanatory view similar to FIG. 10, showing a state in which the eccentric disc is rotated by the drive shaft.

13 is a characteristic diagram showing reference signals output from the crank angle sensor and the cam position sensor in FIG. 9.

FIG. 14 is a characteristic diagram showing a state in which a phase deviation has occurred between the normal phase difference and the detected value of the phase difference.

[Explanation of symbols]

1 crankshaft 4 camshaft 7 Eccentric mechanism (rotational phase changing means) 9 Eccentric disc 10 control shaft 11 Crank angle sensor (phase difference detection means) 12 Cam position sensor (phase difference detection means) 21 Control unit (control means) α, β rotation phase β1 1st rotation phase β2 Second rotation phase Φ phase difference Φ 0 Normal phase difference a (n) First detection value b (n) second detection value A (n), B (n) Calculated value of regular phase difference θ (n) Phase deviation τ Rotation angle (working amount) τ0 target value Δa (n), Δb (n) Change width of detected value ΔΦ Phase change rate L allowable limit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 13/02 F01L 13/00 F02D 41/20 F02D 45/00 G05B 11/36

Claims (2)

(57) [Claims] 1. A crankshaft, a camshaft rotatably driven by the crankshaft to open and close an intake or exhaust valve, and a rotational phase of the camshaft to change the opening / closing timing of the valve. Rotation phase varying means for producing a phase difference between the rotation phases of the crankshaft and the camshaft, and a phase difference for detecting a phase difference produced between the crankshaft and the camshaft by the rotation phase varying means as a detection value. A valve timing control device for an engine, comprising: a detection means; and a control means for feedback-controlling the rotational phase varying means based on at least a phase difference detection result by the phase difference detection means, wherein the control means comprises the camshaft. The rotation phase of is the predetermined first rotation phase and the second rotation phase Reading means for reading the first detection value and the second detection value from the phase difference detecting means, a normal phase difference to be generated between the crankshaft and the camshaft, and the normal phase difference. To the phase difference calculation means for calculating the phase deviation from the first detection value and the second detection value by the reading means, and the operation amount of the rotation phase varying means from the normal phase difference by the phase difference calculation means. The operation amount calculating means, a signal output means for outputting a control signal to the rotation phase varying means so that the calculated value of the operation amount by the operation amount calculating means becomes a value corresponding to the target value, and the first reading means for reading. Determination means for determining whether or not the detected value excessively changes by comparing the detected value with the second detected value. too much A valve timing control device for an engine, characterized in that, when it is determined that a change has occurred, the normal phase difference is corrected and calculated based on the phase deviation obtained by the previous calculation. 2. The first rotation phase is a constant angle to the front side of the rotation phase with respect to the rotation position of the camshaft where the regular phase difference becomes substantially zero during one rotation of the camshaft. The rotational position with the phase shifted by an amount
The rotational phase of the camshaft is a rotational position shifted from the rotational position of the camshaft by the fixed angle to the rear side of the rotational phase, and the phase difference calculation means causes the determination value to be excessively detected by the determination means. Until it is determined that the phase has changed, the latest phase deviation is calculated from the first detection value and the second detection value read by the reading means while the camshaft makes at least two revolutions, and the phase deviation is calculated. And a detected value, a normal phase difference is calculated, and when the judging means judges that the detected value has excessively changed, the first detected value, the second detected value and the phase deviation due to the previous calculation. The valve timing control device for an engine according to claim 1, wherein the normal phase difference is corrected and calculated based on