JP3542400B2 - Variable valve mechanism controller - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a variable valve mechanism control device that controls a variable valve mechanism capable of changing a valve timing and a lift amount of an engine.
[0002]
[Prior art]
An engine that has a mushroom-shaped poppet type valve with a valve umbrella and a valve rod as an intake valve and an exhaust valve, and drives these intake and exhaust valves by an intake cam and an exhaust cam of a cam shaft that rotates in synchronization with the crankshaft. , The drive cam or the swing cam interposed between the drive cam and the valve is tapered, and the valve timing and lift amount of the intake / exhaust valve are changed by moving the drive cam or the swing cam in the axial direction. A variable valve operating mechanism is provided, and an electric driving means including a motor, a hydraulic mechanism, an electromagnetic clutch, etc. for electrically directly or indirectly driving the variable valve operating mechanism is provided. The duty control is used to change the operation position of the variable valve mechanism, and to change the valve timing and lift amount. It is known from. Japanese Patent Publication No. 58-38603 and Japanese Patent Application Laid-Open No. 5-18221 are examples of such a variable valve mechanism and its control device.
[0003]
[Problems to be solved by the invention]
In a variable valve mechanism that changes a valve timing and a lift amount of a poppet type valve by moving a driving cam or an oscillating cam (hereinafter, collectively referred to as a cam) in the axial direction, when the cam is moved in the axial direction. The valve reaction force of the valve spring acts as a thrust force on the camshaft, and the thrust force increases as the camshaft is moved in a direction in which the valve lift increases. Therefore, in order to quickly set the cam to the target position, it is necessary to control the drive output in accordance with the change in the thrust force. However, the relationship between the cam position and the thrust force of the variable valve mechanism usually shows a non-linear characteristic as shown in FIG. 12, and the control characteristics differ depending on the cam position. Since the controllability differs depending on the deviation from the position, overshoot and undershoot when the target position changes suddenly may not be able to be suppressed. There is a possibility that a stopper for mechanically controlling the lift position and the lower limit lift position may be damaged. FIG. 13 is a time chart showing, as an example, a characteristic at the time of rising when the target position of the cam suddenly changes to the full advance position where the lift amount is maximum in the conventional variable valve mechanism control device using the electromagnetic clutch. In the figure, (a) shows the temporal change of the target position (thin line) and the actual position (thick line) of the cam indicated by the lift amount (mm), and (b) shows the temporal change of the duty value (%). In the conventional apparatus, the overshoot or undershoot when the target position is rapidly changed may be excessive as shown in the figure. Further, the cam position-thrust force characteristic varies depending on the engine speed, the engine oil temperature, the engine water temperature, the power supply voltage, and the like. Therefore, it has been practically difficult to always ensure good control performance.
[0004]
Further, the duty value-cam position characteristic in the variable valve mechanism control is, for example, as shown in FIG. 14 and exhibits a trapezoidal hiss due to friction. Although the degree varies depending on the specification, the full advance angle (100%) Normally, the control region (duty value region) from to the full retardation (0%) is narrow. For example, in the example of the specification A shown in the drawing, the duty value region during this period is extremely narrow, about 8 to 20%. For this reason, the control system itself is very sensitive and has a rough control resolution, and it is easy to cause a positional shift at a high advance position and a deterioration in settling at a low advance position. The duty value-cam position characteristic changes using the engine oil temperature, the clutch applied voltage, the engine speed, and the like as parameters, and in particular, the control region changes. FIG. 15 shows an example of a characteristic change using the engine oil temperature as a parameter, FIG. 16 shows an example of a characteristic change using the engine speed as a parameter, and FIG. 17 shows an example of a characteristic change using the clutch applied voltage as a parameter. . FIG. 18 is a time chart showing a change in controllability due to a change in engine speed by an output voltage (V) of a potentiometer for cam position detection. 18A shows a case where the engine speed (ne) is 1000 rpm, and FIG. 18B shows a case where the engine speed (ne) is 2000 rpm. Note that the control gain is the same.
[0005]
Further, as can be seen from FIG. 18, if the control gain remains the same, good controllability cannot be maintained when the engine speed changes. Therefore, it is necessary to correct characteristic changes due to parameters such as oil temperature, clutch applied voltage, and engine speed. However, for example, if the control gain of the duty value calculation is changed according to these parameter changes, the data becomes enormous and controllability deteriorates.
[0006]
According to the present invention, the overshoot or undershoot at the time of a sudden change of the target position due to the non-linearity of the cam position-thrust force characteristic of the variable valve mechanism control system is excessive, and the mechanical upper and lower stoppers are damaged. The purpose is to prevent.
[0007]
[Means for Solving the Problems]
The variable valve mechanism control device according to the first aspect of the present invention is provided between a poppet valve that is biased to close by a valve spring and is driven to open by a drive cam, or between the drive cam or the drive cam and the valve. By changing the axial position of the oscillating cam, one of the valve timing and the valve lift of the valve is changed, and a reaction force including a valve reaction force by a valve spring is caused by the change of the axial position. A variable valve mechanism that acts as a thrust force on a cam shaft that drives a drive cam, an electric drive unit that directly or indirectly drives the variable valve mechanism, an operation state detection unit that detects an operation state of the engine, The target position in the axial direction of the drive cam or the swing cam is determined based on the operation state detected by the operation state detection means.Ma Depending onTarget position setting means for setting, a current position detecting means for detecting an actual position of the driving cam or the swing cam in the axial direction, and a target position for setting the actual position detected by the current position detecting means to a target position.Drive the electrical drive meansCalculate the required control amount,With this calculated control amountDrive output of electrical drive meansDrive controlControl means, and a variable valve mechanism control device comprising:Controllability of the control meansParameter value detecting means for detecting a parameter value associated with, according to the parameter value detected by the parameter value detecting means,Calculated control amountAnd a clip value setting unit that sets a clip value that is restricted so that the target value is within a predetermined range. When a setting of the target position is changed, a predetermined clip value invalid time for invalidating the clip value is set. It is characterized by that.
[0008]
[Action]
The variable valve mechanism according to the present invention can change any one of the valve timing and the lift amount of a poppet type valve that is biased to close by a valve spring and driven to open by a drive cam. The change is performed by changing the axial position of the driving cam or the swing cam interposed between the driving cam and the valve. Further, with the change, a reaction force including a valve reaction force by the valve spring acts as a thrust force on a cam shaft for driving the drive cam. This variable valve mechanism is electrically directly or indirectly driven by an electric driving means. At this time, a required control amount for stabilizing the operating position defined by the axial position of the drive cam or the swing cam of the variable valve mechanism to the target position is calculated, and an output value corresponding to the calculated control amount is calculated. The drive output of the electric drive means is controlled by (for example, a duty value).
[0009]
Further, when a clip value for limiting the output value of the drive output control means to a predetermined range is provided, the drive output of the electric drive means is clipped at the upper limit or the lower limit, so that the overshoot or undershoot of the cam position can be prevented. Suppression becomes possible. In this case, when the clip invalid time is set and the clip value is invalidated for a predetermined time when the target position is changed, a step response for rapidly advancing the cam position to the full position is given to the target position. It is possible to reduce wasted time and obtain good controllability.
[0010]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a cross-sectional view showing an upper structure of an engine according to an embodiment of the present invention in a vertical cross section orthogonal to a crankshaft. FIG. 2 is an explanatory view of the structure and operation as viewed from the right side in FIG.
[0012]
In FIG. 1, reference numeral 1 denotes a cylinder head connected to an upper portion of a cylinder (not shown). A combustion chamber recess 2 is formed on the lower surface of the cylinder head 1 at a position facing the cylinder chamber. The engine of this embodiment has two intake valves and two exhaust valves. The cylinder head 1 has two intake ports 3a and 3b for each cylinder in the crankshaft direction on the left side in FIG. 1 (in the plane of FIG. 1). (In the direction perpendicular to) and open to the combustion chamber recess 2, and the two exhaust ports 4a and 4b are also formed to open to the combustion chamber recess 2 on the right side in FIG. Have been. Two poppet-type intake valves 5a and 5b are provided to open and close the respective openings of the intake ports 3a and 3b, and also a poppet-type to open and close the respective openings of the exhaust ports 4a and 4b. These two exhaust valves 6a and 6b are provided. The intake valves 5a, 5b and the exhaust valves 6a, 6b are such that the intake valves 5a, 5b are parallel, the exhaust valves 6a, 6b are parallel, and the intake valves 5a, 5b and the exhaust valves 6a, 6b are V. The arrangement is shaped. Above the cylinder head 1, valve springs 7a, 7b; 8a, 8b are arranged so as to urge the intake valves 5a, 5b and the exhaust valves 6a, 6b to close. The intake valves 5a, 5b and the exhaust valve Tappets 9a, 9b; 10a, 10b are arranged at positions in contact with the respective valve stem heads of 6a, 6b. An intake camshaft 11 is arranged above the intake valves 5a, 5b in the crankshaft direction, and an exhaust camshaft 12 is arranged above the exhaust valves 6a, 6b also in the crankshaft direction. The drive cams 13a and 13b corresponding to the two intake valves 5a and 5b of each cylinder are provided on the shaft 11, and the drive cams 14a and 13b corresponding to the two exhaust valves 6a and 6b of each cylinder are provided on the exhaust camshaft 12. 14b is provided. Among these, the intake side camshaft 11 is driven by an electromagnetic clutch device (not shown) to be movable in the axial direction, and the drive cams 13a and 13b are tapered cams whose cam profiles change depending on the position in the axial direction. I have. This change in the cam profile causes the lift characteristics of the intake valves 5a and 5b as a whole to shift to the high lift side when the intake camshaft 11 moves in one direction (forward in FIG. 1, leftward in FIG. 2). , When it moves in the opposite direction, it is shifted to the low lift side. Also, between the tappets 9a, 9b at the heads of the intake valves 5a, 5b and the drive cams 13a, 13b on the intake side, the springs 15a, 15b bias the springs 15a, 15b toward the drive cams 13a, 13b. Swing cams 16a and 16b are provided. In FIG. 2, a solid line indicates a high lift position, and a broken line indicates a low lift position.
[0013]
The intake valve actuating mechanism is a variable valve actuating mechanism capable of changing the cam position by moving the camshaft 11 in the axial direction to change the lift amount. The output of the electromagnetic clutch for driving the camshaft 11 is shown in FIG. Not controlled by control unit. Therefore, information such as the engine speed and oil temperature is input to the control unit, and the output of a potentiometer for detecting the cam position is input. Then, the target position of the cam is set by a map according to the engine speed and the like, and the current flowing through the electromagnetic clutch is duty-controlled to control the cam position.
[0014]
The duty control is based on the PID control, and the calculation of the duty output value (duty) is based on the following formula.
duty =
Pe • I • ∫edt + D • de / dt + A • dR / dt + B • dT / dt
P: Proportional term gain
I: integral term gain
D: Deviation derivative term gain
A: Current position differential term gain
B: Target position differential term gain
e: deviation (e = TR)
T: Target position
R: Current position
[0015]
In addition, a clip value (limit value) is set at the upper and lower limits of the duty output value. FIG. 3 is a time chart similar to FIG. 13 showing the characteristic at the time of rising when the target position of the cam suddenly changes to the full advance position where the lift amount is the maximum in this embodiment. In the figure, (a) shows the change over time between the target position (thin line) and the actual position (thick line) of the cam expressed by the lift amount (mm), and (b) shows the change over time of the duty value (%). In FIG. 3B, a is the upper limit clip value of the duty value, and b is the lower limit clip value. The duty value when the target position changes abruptly due to the step response is shown by a solid line with the portion shown by the broken line in FIG. 3B being clipped. As a result, the cam position (lift amount) has the characteristic shown by the solid line in FIG. 3A, and the overshoot and undershoot shown by the broken line are prevented.
[0016]
The clip value is tabulated so as to change according to various parameters related to controllability, such as the target position of the cam, the deviation between the target position and the current position (actual position), the engine speed, the engine oil temperature, and the power supply voltage. I have. FIG. 4 is a table for setting the upper limit clip value using these parameters. As for the deviation between the target position and the current position, the clip value is increased as shown in FIG. 4A so as to correspond to a sudden change in the required duty value when the deviation is large. When the target position is close to the upper limit or the lower limit, a clip value is set as shown in FIG. Also, as the engine speed increases, the system becomes more sensitive as the engine speed increases, and overshoot and undershoot easily occur. Therefore, as shown in FIG. 4C, the clip value increases as the engine speed increases. Smaller. Also, as the oil temperature rises, the system becomes more sensitive as the oil temperature rises, and overshoot and undershoot are likely to occur. Therefore, as shown in FIG. 4D, the clip value decreases as the oil temperature increases. (The same applies to the water temperature). Further, with respect to the clutch power supply voltage, since the clutch attraction torque decreases as the power supply voltage decreases, the clip value increases as the power supply voltage decreases, as shown in FIG. As for the target position differential value (dT / dt), the larger the target position differential value (the larger the step width), the more easily overshoot and undershoot occur, so that as shown in FIG. As the target position differential value increases, the clip value decreases.
[0017]
FIG. 5 is a flowchart showing a control flow of the duty value clip based on the clip value. This processing is executed, for example, every 5 ms. In step S11, it is determined whether the duty output value (duty) according to the above formula is larger than the upper limit clip value (a) (duty> a). Next, in step S12, it is determined whether the duty is smaller than the lower limit (b) (duty <b). If b ≦ duty ≦ a, the process proceeds to step S13. In step S13, the calculated value (duty) is directly used as the duty output value (duty). If the determination in step S12 is duty <b, the duty output value (duty) is clipped to the lower limit (b) in step S14 (duty = b). If duty> a in step S11, the duty output value (duty) is clipped to the upper limit (a) in step S15 (duty = a).
[0018]
In the duty control, an invalid time may be set to the upper limit clip value so as to reduce a dead time when a step response for rapidly advancing the cam position to the target position is given. In this case, as shown in FIG. 6, the duty output value indicates the invalid time (t₁), The upper limit clip value (a) is neglected, so that good controllability can be obtained after full advance.
[0019]
FIG. 7 shows such an invalid time (t₁6 is a flowchart showing a control flow of a duty value upper limit clip in which (1) is set. This process is executed, for example, every 1 ms. In step S21, it is determined whether the calculated value (duty) of the duty output is larger than the upper limit clip value (a) (duty> a). If duty> a, the process proceeds to step S22. The counter value is counted up by one, and in step S23, the counter value becomes t.₁To see if the counter value has reached t₁If not, the process proceeds to step S24, and the calculated value (duty) is directly used as the duty output value (duty). Also, the counter value is t₁Is reached, the process proceeds to step S25, and the duty output value (duty) is clipped to the upper limit value (a) (duty = a). Then, in step S26, the counter value is reset to the initial value (0). If duty ≦ a is determined in step S21, the process proceeds to step S27, where the calculated value (duty) is used as it is as a duty output value (duty), and the counter value is reset to an initial value (0) in step S28.
[0020]
In the duty control, instead of setting the clip value to the duty output value (duty) as described above, the proportional term (P term), the integral term (I term), and the deviation derivative term (D term) ), A target position differential term (term B), a clip value is provided for each calculation item, and each clip value is changed according to parameters such as a target position, deviation, engine speed, engine oil temperature, and power supply voltage. A clip invalid time (B term valid time) is set for the target position differential term (B term), and only the target position differential term (B term) responds effectively without a predetermined time when the target position is changed. By doing so, the dead time when a step response having a large deviation is given to the target position can be suppressed, and controllability can be improved.
[0021]
In the control for setting the B term effective time at the time of the step response, as shown in FIG. 8, when the target position changes in the step response and the change ΔT is larger than the threshold value KTD, the B term effective time (KCS ), ΔT is the provisional value ΔT of dT / dt._buf, The B term (B · dT / dt) is calculated.
[0022]
FIG. 9 is a flowchart of the control for setting the B term valid time in this manner. This process is executed, for example, every 5 ms, and in step S31, the current value T of the target position T_nAnd the value T five times before_n-5And the difference is stored in the target position change amount ΔT. Then, in step S32, it is determined whether or not the change amount ΔT of the target position is larger than the threshold value KTD. If the change amount ΔT is larger than the threshold value KTD, the value of ΔT is changed to ΔT in step S33._bufTo be stored. Then, the flag xcb is set to 1 in step S34, and the process proceeds to step S37. On the other hand, if it is determined in step S32 that the change amount ΔT of the target position is equal to or smaller than the threshold value KTD, the process proceeds to step S35, where it is determined whether the counter value is smaller than the time KCS. Sets 1 in the flag xcb in step S34, and proceeds to step S37. On the other hand, when the counter value exceeds the KCS in the determination in step S35, the process proceeds to step S36, where the flag xcb is set to 0, and then proceeds to step S37. Then, in a step S37, it is determined whether or not the flag xcb is 1, and when the flag xcb is 1, the process proceeds to a step S38. Then, the counter value is incremented by one in step S38, and it is checked in step S39 whether the counter value is smaller than the time KCS. If the counter value is smaller than KCS, ΔT is determined in step S40._bufIs stored in ΔT ′. Then, in step S41, B · ΔT ′ is calculated, and this is set as the value of the B term. Then, the process proceeds to step S45.
[0023]
If it is determined in step S39 that the counter value has exceeded KCS, the process proceeds to step S42, where the clip value β is stored in ΔT ′. Then, the term B is calculated in step S41, and the process proceeds to step S45.
[0024]
If the flag xcb is 0 in the determination in step S37, the counter value is reset to the initial value 0 in step S43, and the value of ΔT is stored in ΔT ′ in step S44. Then, the term B is calculated in step S41, and the process proceeds to step S45.
[0025]
In step S45, it is determined whether the counter value is 0. If the counter value is 0, the process is terminated. If the counter value is not 0 in step S45, the processing of steps S37 to S45 is repeated.
[0026]
Further, the duty control is based on a correction gain (gain) VG for a calculation term such as a proportional term (P term), an integral term (I term), a deviation derivative term (D term), and a target position derivative term (B term) in the formula. May be set, and the correction gain VG may be reflected in an output value by tabulating the correction gain VG with parameters such as the target position, deviation, engine speed, engine oil temperature, and power supply voltage. Accordingly, it is possible to improve the control performance of the variable valve mechanism control system, prevent the displacement at the high advance position, and improve the stabilization at the low advance position. FIG. 10 is a time chart showing the change in the cam position when the step response is given to the target position by the output voltage (V) of the potentiometer. FIG. 10A shows the case where the correction gain VG is not set, and FIG. The case where VG is set is (b).
[0027]
The calculation formula in this case is as follows.
duty =
VG (Pe + IΣe + D ・ de / dt + A ・ dR / dt + B ・ dT / dt)
[0028]
The above-mentioned correction gain (VG) is, as shown in FIG._mid, The lower limit position V on the low-advance side_minAnd the high-advance side upper limit position V_maxSet the value for. Then, the desired target position V_targetIs calculated.
VG = 1 + ｛(V_target-V_mid) / (V_max-V_mid)｝
(However, V_mid<V_target<V_max)
VG = 1 + ｛(V_mid-V_target) / (V_mid-V_min)｝
(However, V_min<V_target<V_mid)
[0029]
In addition, the setting may be such that a specific calculation term is strengthened by weighting each calculation term in accordance with the above-described parameter, thereby further improving control performance. In that case, the calculation formula is as follows.
duty =
VG ・ P ・ e + VG ・ I ・ Σe + VG ・ D ・ de / dt + VG ・ A ・ dR / dt + VG ・ B ・ dT / dt
[0030]
In addition, for example, when setting the correction gain in this way, an offset term (pwmoffset) corresponding to these parameters is set in a calculation formula so as to correct a characteristic change due to parameters such as oil temperature, clutch applied voltage, and engine speed. Therefore, good controllability can be maintained while the control gain is fixed. The calculation formula in that case is as follows.
duty = pwmoffset +
VG (Pe + IΣe + D ・ de / dt + A ・ dR / dt + B ・ dT / dt)
[0031]
In the above embodiment, the variable valve mechanism is adopted for the intake valve. However, the present invention is not limited to this. A variable valve mechanism is provided for at least one of the intake valve and the exhaust valve. Widely applicable to adopted engine.
[0032]
In the above embodiment, the variable valve mechanism of the type that moves the drive cam in the axial direction has been described. However, the present invention can be applied to the case of the variable valve mechanism of the type that moves the swing cam.
[0033]
Further, the present invention can be widely applied to various other variable valve mechanism control devices capable of changing either one of the valve timing and the lift amount.
[0034]
【The invention's effect】
Since the present invention is configured as described above, the target position, the deviation between the target position and the current position, the engine speed, the engine oil temperature, the engine water temperature, and the power supply voltage are used for calculating the control amount of the variable valve mechanism control device. A clip value is set in accordance with a predetermined condition relating to controllability or a parameter resulting from an increase or decrease in a reaction force, thereby suppressing overshoot or undershoot of a cam position at the time of changing a target position, and performing a variable valve operation. It is possible to prevent the mechanical upper and lower stoppers from being damaged by overshoot or undershoot at the time of a sudden change in the target position due to the non-linear cam position-thrust force characteristic of the mechanism control system. Further, when the clip value is provided in this manner, by setting the clip invalid time and invalidating the clip value for a predetermined time when the target position is changed, the dead time at the time of the sudden change of the target position is reduced, and good controllability is obtained. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a top sectional view of an engine according to an embodiment of the present invention.
FIG. 2 is an explanatory view of the structure and operation of a variable valve mechanism according to an embodiment of the present invention.
FIG. 3 is a time chart of rising characteristics in one embodiment of the present invention.
FIG. 4 is a table characteristic diagram of an upper limit clip value in one embodiment of the present invention.
FIG. 5 is a flowchart showing a control flow of a duty value clip in one embodiment of the present invention.
FIG. 6 is a time chart of rising characteristics in another embodiment of the present invention.
FIG. 7 is a flowchart illustrating a control flow of a duty value upper limit clip of the embodiment according to FIG. 6;
FIG. 8BIt is a time chart which shows control of a term valid time setting.
FIG. 9BIt is a flowchart of the control which sets a term valid time.
FIG. 10S6 is a time chart showing control characteristics at the time of a step response.
FIG. 11SupplementFIG. 4 is an explanatory diagram of a positive gain setting.
FIG. 12 is a characteristic diagram of cam position-thrust force of a general variable valve mechanism.
FIG. 13 is a time chart showing a rising characteristic in a conventional variable valve mechanism control device.
FIG. 14 is a general duty value-cam position characteristic diagram of variable valve mechanism control.
FIG. 15 is a characteristic diagram in which a general oil temperature of a variable valve mechanism control is used as a parameter.
FIG. 16 is a characteristic diagram in which variable engine speed control generally uses the engine speed as a parameter.
FIG. 17 is a characteristic diagram in which a variable valve mechanism control general clutch applied voltage is used as a parameter.
FIG. 18 is a time chart showing a change in controllability depending on the engine speed in general variable valve mechanism control.
[Explanation of symbols]
5a, 5b Intake valve
11 Camshaft (intake side)
13a, 13b Drive cam
16a, 16b swing cam

Claims (1)

A poppet type valve which is biased to close by a valve spring and is driven to open by a drive cam;
By changing the axial position of the drive cam or the swing cam interposed between the drive cam and the valve, one of the valve timing and the valve lift of the valve is changed, and the axial direction is changed. A variable valve mechanism in which a reaction force including a valve reaction force by the valve spring acts as a thrust force on a cam shaft that drives the drive cam with a change in position;
Electrical drive means for directly or indirectly driving the variable valve mechanism;
Operating state detecting means for detecting an operating state of the engine;
Target position setting means for setting a target position in the axial direction of the drive cam or the swing cam based on a map based on the operation state detected by the operation state detection means,
Current position detecting means for detecting an actual position of the driving cam or the swing cam in the axial direction;
A required control amount for driving the electric drive unit for setting the actual position detected by the current position detection unit to the target position is calculated, and the drive amount of the electric drive unit is calculated based on the calculated control amount. Control means for driving and controlling the output, the variable valve mechanism control device comprising:
Parameter value detection means for detecting a parameter value related to the controllability of the control means,
Clip value setting means for setting a clip value that is limited so that the calculated control amount falls within a predetermined range, according to the parameter value detected by the parameter value detection means,
A variable valve actuation mechanism control device, wherein a predetermined clip value invalid time for invalidating the clip value is set when the setting of the target position is changed.

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