JP2002004897A - Variable valve timing controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize accurate control, without having to use a special circuit, even if an operation characteristic of a solenoid control valve fluctuates by changes in temperature conditions, when operating a hydraulic actuator by the use of the solenoid control valve. SOLUTION: This variable valve timing controller displaces a phase of a camshaft by the hydraulic actuator to control valve timing to a desired timing. In a phase angle control routine, a target phase angle is set, on the basis of a detected operation state (steps S1, S2), and a proportional-integral correction value and a control duty ratio to the solenoid control valve (OCV) are set, on the basis of a phase angle difference between the target phase angle and an actual phase angle (steps S5, S6). When fluctuations in the operation characteristic of the solenoid control valve are estimated from temperature condition parameters, a correction value according to the temperature conditions is set (steps S7, S8), and the temperature correction value is added to correct the control duty ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a variable valve timing control apparatus for an internal combustion engine for variably controlling the operation timing of an intake valve or an exhaust valve of the internal combustion engine.

[0002]

2. Description of the Related Art As a prior art relating to a variable valve timing control apparatus for an internal combustion engine, for example, Japanese Patent Laid-Open No.
The valve timing control device for an internal combustion engine described in Japanese Patent No. 7235 is exemplified. This known valve timing control apparatus operates a hydraulic actuator during operation of an internal combustion engine to apply a phase displacement to a camshaft, and controls valve timing according to a rotation angle phase difference of the camshaft with respect to a crankshaft. . At this time, if the viscosity of the hydraulic oil changes due to the temperature fluctuation, a control error may occur in the operation of the hydraulic actuator. Therefore, a known valve timing control device estimates the temperature of the hydraulic oil, and based on the estimated oil temperature, Thus, the control rotation angle, that is, the operation amount of the hydraulic actuator is corrected.

[0003]

The above-mentioned known valve timing control apparatus focuses on a temperature change of hydraulic oil (fluid) and corrects the control rotation angle in accordance with the change in the physical property. No consideration is given to fluctuations in operating characteristics of electronic devices controlled based on the rotation angle.
That is, the fluctuations in the hydraulic oil temperature not only change the physical properties of the hydraulic oil itself, but also affect the electronic devices handling the hydraulic oil. For example, when the supply of hydraulic oil to a hydraulic actuator is controlled using a linear solenoid valve as in a known valve timing control device, if the temperature of the coil changes due to heat conduction from the hydraulic oil, the temperature condition The coil resistance also varies accordingly. In this case, even if the control rotation angle is corrected, the coil current fluctuates according to the temperature condition at that time.
During the control, the operating characteristics of the linear solenoid valve fluctuate undesirably. In such a situation, accurate operation of the hydraulic actuator according to the control rotation angle cannot be guaranteed, and desired valve timing control becomes difficult. Such a problem can occur not only due to a change in the temperature of the hydraulic oil, but also due to a change in the temperature of the internal combustion engine and the temperature of the cooling water, and also due to the heat generated by the coil itself.

In this respect, it is conceivable to add a current feedback circuit to the control circuit of the solenoid valve as in, for example, a valve timing adjusting device described in JP-A-7-332118. It is not preferable in that the cost of electronic devices is greatly increased. Accordingly, it is an object of the present invention to realize accurate valve timing control in response to a change in operating characteristics of an electronic device due to a change in temperature without increasing the cost.

[0005]

A variable valve timing control apparatus for an internal combustion engine according to the present invention (Claim 1) relates to a control of supply of a working hydraulic pressure to a hydraulic actuator using an electromagnetic control valve. An object of the present invention is to solve the above problem by correcting an operation amount for an electromagnetic control valve based on a change.

That is, the variable valve timing control device of the present invention has a cam whose phase can be displaced relative to the crankshaft, and detects the operating state of the internal combustion engine together with the actual phase angle of the cam. Then, when the target phase angle is set based on the operation state, the variable valve timing control device sets the operation amount for the electromagnetic control valve based on the deviation between the actual phase angle and the target phase angle, and according to the operation amount. To supply working hydraulic pressure to the hydraulic actuator. The hydraulic actuator operates by receiving the supply of the operating hydraulic pressure, and displaces the phase of the cam according to the supply amount. As a result, a phase displacement that matches the target phase angle is obtained, and the desired valve timing advance or retard is obtained. To achieve. At this time, if the temperature condition of the electromagnetic control valve changes due to a change in the temperature of the hydraulic oil or other factors, the operation amount is corrected based on the change in the operating characteristics accompanying the change, so that the hydraulic pressure applied to the hydraulic actuator is Variations in the supply amount can be effectively prevented. Note that the temperature detection means for detecting the temperature condition of the electromagnetic control valve can be appropriately included in the present invention.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be applied to, for example, an internal combustion engine having a variable valve timing mechanism. A preferred embodiment will be described below. FIG. 1 schematically shows the structure of a variable valve timing mechanism provided in an internal combustion engine. This variable valve timing mechanism includes, for example, a hydraulic actuator 1 that changes the phase of a camshaft 2 on the intake valve side. I have. However, the variable valve timing mechanism may be provided on the exhaust valve side.

The hydraulic actuator 1 has a vane rotor 4 attached to one end of a cam shaft 2 on the intake side. The vane rotor 4 is rotatably combined with a timing pulley 6. . In particular,
The vane rotor 4 extends radially from the axis of the camshaft 2.
The pulley hub of the timing pulley 6, which is hatched in the drawing, is formed with a notch that crosses the center of rotation and crosses in a substantially cross shape. In a state where the vane rotor 4 and the timing pulley 6 are combined, the individual vanes 8 are fitted into the notched portions of the timing pulley 6, and the advance hydraulic chamber 10 and the retard hydraulic chamber are located on both sides when viewed in the circumferential direction. 12 can be formed in an oil-tight manner. Then, with the relative rotational displacement of the vane rotor 4 with respect to the timing pulley 6, the individual vanes 8 are advanced and retarded hydraulic chambers 10,
12 is enlarged or reduced, and the vane rotor 4 is positioned at a position where the vane 8 contacts the inner wall of any of the hydraulic chambers 10 and 12.
Is restricted.

As is well known, a timing belt 16 is wound around the timing pulley 6 together with the exhaust-side timing pulley 14, and the timing belt 16 is driven by a crank pulley (not shown). Usually, these timing pulleys 6 and 14 are rotated at a half cycle thereof in synchronization with the phase of the crankshaft. However, in this embodiment, the relative rotation displacement of the vane rotor 4 causes the rotation of the crankshaft. On the other hand, the phase of the camshaft 2 can be relatively displaced.

An advanced oil passage and a retard oil passage (not shown) are formed in the vane rotor 4. The advance oil passage and the retard oil passage are not shown, respectively. Are communicated with the outside of the timing pulley 6. The hydraulic actuator 1 is supplied with a working oil pressure from a hydraulic source (oil pump) (not shown), and can introduce the working oil pressure into the advance and retard oil chambers 10 and 12 through these advance and retard oil passages, respectively.

An oil control valve (OC) comprising an electromagnetic control valve is provided in the supply path of the operating oil pressure.
V) 20 are provided, and the advance and retard oil passages of the vane rotor 4 are connected to the advance supply port 22 and the retard supply port 24 of the OCV 20, respectively. OCV2
Numeral 0 can introduce hydraulic oil through the input port 26 and discharge hydraulic oil through a pair of drain ports 28 to an oil recovery path (not shown).

The above-described OCV 20, for example, can switch the position of the spool 32 by energizing the solenoid 30, and the switching operation is performed by an electronic control unit (ECU) 34.
Is electronically controlled by As is well known, the ECU 34
Has a function of outputting a time ratio for energizing the solenoid 30, that is, a duty ratio as an operation amount for the OCV 20, and switching the position of the spool 32 as desired according to the value.

That is, when the position of the spool 32 switches due to a change in the duty ratio output from the ECU 34, the flow direction of the hydraulic oil switches between the advance supply port 22 and the retard supply port 24, and the hydraulic actuator 1
In the advanced and retarded hydraulic chambers 1 according to the integrated flow rate of hydraulic oil,
The volume of 0,12 is enlarged or reduced. On the other hand, when the duty ratio (neutral duty ratio) at which both the advance and retard supply ports 22 and 24 are closed by the spool 32 is output from the ECU 34, the supply ports 22 and 24 are supplied.
And the hydraulic system between the hydraulic chambers 10 and 12 is closed,
In this state, the volumes of the advance and retard hydraulic chambers 10 and 12 are kept constant.

The hydraulic actuator 1 shown in FIG. 1 can control the phase angle of the camshaft 2 using the switching control (duty control) of the OCV 20 by the ECU 34 described above.
Specifically, the total supply and discharge amount of hydraulic oil to and from each of the hydraulic chambers 10 and 12 is converted into a relative rotational displacement amount of the vane rotor 4,
A phase displacement is given to the camshaft 2 according to the rotational displacement.

Here, the variable valve timing control device of the present invention includes a crank angle sensor 36 for outputting a crank angle pulse synchronized with the phase of the crank shaft, and a phase for detecting the actual phase angle of the cam shaft 2. The phase angle sensor 38 outputs a rotation angle pulse synchronized with the rotation of the camshaft 2 to the ECU 34 as a detection signal. EC
In U34, based on the output phase difference between the crank angle pulse and the rotation angle pulse of the camshaft 2, the actual phase angle indicating the advance or retard of the camshaft 2 with respect to the crankshaft can be detected (actual phase angle). Phase angle detecting means).

Further, the variable valve timing control device comprises:
An operating state sensor 40 (operating state detecting means) is provided, and the operating state sensor 40 collects information for detecting a value (such as an average effective pressure Pe) correlated to the load of the internal combustion engine in the ECU 34. . The information on the crank angle pulse obtained from the above-described crank angle sensor 36 can also be used for detecting the rotational speed indicating the operating state of the internal combustion engine (operating state detecting means).

The ECU 34 has a function of setting a target phase angle to be given to the camshaft 2 based on the detected operating state of the internal combustion engine (setting means). The ECU 34 has, for example, a rotational speed Ne of the internal combustion engine. And the size of the load (P
A phase control map that gives an optimum cam phase angle based on e) is stored. The ECU 34 controls the amount of rotational displacement of the vane rotor 4 so that the actual phase angle of the camshaft 2 matches the target phase angle. Therefore, the ECU 34 controls the OCV 20 based on the deviation between the actual phase angle and the target phase angle. A duty ratio to be output to the solenoid 30 is set.

Here, in the present embodiment, regarding the duty control of the OCV 20, an oil temperature sensor 42 is used as a sensor for detecting a parameter representing a temperature condition of the solenoid 30.
And a cooling water temperature sensor 44.
Reference numeral 4 has a function of correcting the above-described duty ratio based on sensor signals collected from these sensors.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the phase angle control by the variable valve timing control device of the present invention will be described below with reference to specific embodiments. The following description also clarifies the details of the duty ratio correction function of the ECU 34. FIG.
As one embodiment, a flowchart of a phase angle control routine executed by the ECU 34 is shown. The ECU 34 first
In step S1, the operating state of the internal combustion engine is detected, and then in step S2, a target phase angle is set. In the processes of steps S1 and S2, as described above, the rotational speed, the average effective pressure, and the like are detected from the information collected by the ECU 34, and the detected values are referred to a phase control map to set a target phase angle. can do. Note that such a method of setting the target phase angle is an example, and the target phase angle may be set by another calculation method.

The ECU 34 determines in step S3 that the camshaft 2
Is detected, a deviation between the target phase angle and the actual phase angle (= target phase angle−actual phase angle) is calculated in step S4. In the present embodiment, the operation of the OCV 20 is feedback-controlled, and more specifically, the duty ratio set in step S2 is proportionally integrated corrected according to the phase angle deviation. Therefore, the ECU 34 sets the proportional correction value of the duty ratio in the procedures of steps S5 and S6, and updates the integral correction value by increasing or decreasing. Note that these correction values can be reflected in the correction of the control duty ratio Du described later.

In the next step S7, the ECU 34
Various parameters representing the temperature condition of the solenoid 30 are detected. Examples of these parameters include hydraulic oil temperature, cooling water temperature, coil energization time, and the like.
In any case, there is a close correlation with the coil average temperature of the solenoid 30. For example, hydraulic oil temperature and cooling water temperature affect the change in coil average temperature due to hydraulic oil and heat conduction from the internal combustion engine.
On the other hand, the coil energization time correlates with the average coil temperature due to its own heat generation. Note that the coil energizing time may be replaced by the elapsed time from the start of the internal combustion engine.

FIG. 3 shows an OCV 20 used in this embodiment.
Between the average coil temperature and the coil resistance
Is shown. As is clear from FIG.
The coil resistance changes as the temperature changes,
The resistance value increases at a constant rate according to the rise. The book
In Examples, the lowest temperature that can be assumed under normal use conditions
When Tmin and allowable upper limit temperature Tmax are defined,
Corresponding minimum resistance R ₁The maximum resistance R_TwoIs about
Doubled.

FIG. 4 shows a change in the operating characteristics of the OCV 20 with respect to a change in temperature based on the temperature dependency of the coil resistance. Specifically, OCV20
Is representative of, for example, a neutral duty ratio, in a region where the average coil temperature is low, the neutral duty ratio of the OCV 20 is low, and the neutral duty ratio increases at a constant rate as the average coil temperature increases. In addition, if the above-mentioned temperatures Tmin and Tmax are defined in FIG. 4, it is understood that the neutral duty ratio fluctuates in these temperature ranges within a range of, for example, about 25% to about 50%. Such an OCV20
The change in the operating characteristics causes a change in the supply amount of the working oil pressure to the hydraulic actuator 1 depending on the temperature condition used, and causes an error in the actual phase angle control.

FIG. 5 shows the relationship between the actual current value supplied to the solenoid 30 of the OCV 20 and the flow rate of hydraulic oil. In FIG. 5, for example, when the current value is A ₀ , the supply of the working oil pressure is stopped (flow rate = 0), and at this time, the OCV 20 is in the neutral position. Therefore, according to the control program of the ECU 34, when the neutral duty ratio is set, the solenoid 30
It becomes to select the duty ratio to be energized current A ₀ with respect to the change in coil resistance value due to a change in temperature conditions, vary undesirably the actual current value for the set neutral duty rate Will be. This result will vary neutral duty ratio for energizing the constant current A ₀ to the solenoid 30 by the temperature conditions as shown in Figure 4.

In order to eliminate the control error of the OCV 20 represented by the fluctuation of the neutral duty ratio, the ECU 3
In step S8, a neutral duty ratio correction value corresponding to the temperature condition is set in step S8. This correction value can be obtained based on a change in operating characteristics due to a temperature change of the OCV 20. For example, when the reference temperature Ts under the standard use condition is defined in FIG. 4, a reference value D ₀ of the neutral duty ratio corresponding to the reference temperature Ts can be obtained. At this time, when the actual temperature is deviated from the reference temperature Ts, it becomes possible to deviate from the reference value D ₀ value of the amount corresponding neutral duty ratio. Therefore, when the ECU 34 estimates the coil average temperature using the parameters detected in step S7, the ECU 34 can obtain the correction value ΔD of the neutral duty ratio from the amount of deviation of the estimated temperature Te from the reference temperature Ts, for example.

After the above processing, the ECU 34 corrects the control duty ratio Du as an operation amount for the OCV 20 in the last step S9. This correction can be performed by using the above-described reference value D ₀ of the neutral duty ratio as an initial value, and adding a correction value ΔD based on the temperature condition to the initial value. Further, in this embodiment, the correction can be performed by adding the above-described proportional correction value and integral correction value in addition to the correction value ΔD.

When the above steps S1 to S9 are executed,
The ECU 34 outputs the control duty ratio Du, and
Activate CV20. The OCV 20 outputs a hydraulic oil flow rate according to the control duty ratio Du, operates the hydraulic actuator 1 on the advance or retard side, and holds the phase of the camshaft 2 at the position of the target phase angle. As a result of the correction of the control duty ratio as described above, even if the temperature condition of the OCV 20 changes, the supply amount of the hydraulic oil does not change, so that the operation of the OCV 20 is always stable. FIG.
According to the operating characteristics of the above, if the coil resistance value increases or decreases due to the temperature change of the hydraulic oil, the actual coil current value decreases or increases for the same control duty ratio. Since the control duty ratio is corrected correspondingly, the value of the current supplied to the solenoid 30 always matches the required hydraulic oil flow rate. In contrast, if not corrected according to this embodiment, since the current value includes a variation range for the same control duty ratio, for example also be output neutral duty ratio, the current value A ₀ by a temperature change It is easily understood that the hydraulic oil flow is actually output from the OCV 20 to the advance side or the retard side from the OCV 20.

The control of the variable valve timing mechanism according to the present invention can be implemented by variously rewriting the program without being restricted only by the phase angle control routine of the above-described embodiment. In one embodiment, the temperature condition parameter is detected in step S7, but the coil temperature may be directly detected here. Step S
In the description of 8, the method of setting the correction value ΔD by setting the reference temperature Ts is given, but the correction value may be directly set from the coil temperature condition. In one embodiment, the correction value is added to the initial value to perform the correction. However, the correction may be performed by, for example, multiplying the control duty ratio by a correction coefficient.

Further, in the embodiment shown in FIG. 1, a vane rotor type hydraulic actuator is taken as an example, but a helical type hydraulic actuator may be used as a type capable of continuously changing the phase. In addition, the embodiment of the present invention is not limited to the configuration shown in FIG. 1, and the specific configuration can be replaced by various equivalent means. It goes without saying that the type of the internal combustion engine to which the present invention is applied and its use are not particularly limited.

[0030]

The variable valve timing control apparatus for an internal combustion engine according to the present invention (claim 1) can realize accurate valve timing control without adding a special electronic circuit.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a variable valve timing control device.

FIG. 2 is a flowchart of a cam phase angle control routine executed as one embodiment.

FIG. 3 is a diagram illustrating a relationship between an average coil temperature and a coil resistance value in an oil control valve.

FIG. 4 is a diagram showing a relationship between a coil average temperature and a neutral duty ratio based on the relationship of FIG. 3;

FIG. 5 is a diagram showing operating characteristics of an oil control.

[Explanation of symbols]

 Reference Signs List 1 hydraulic actuator 2 camshaft 20 oil control valve (electromagnetic control valve) 34 ECU (setting means, control means) 36 crank angle sensor (operating state detecting means) 38 phase angle sensor (actual phase angle detecting means) 40 operating state sensor ( Operating state detection means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norihiko Watanabe 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Keiichi Akagi 5-33-8 Shiba, Minato-ku, Tokyo No. Mitsubishi Motors Corporation (72) Inventor Daisuke Kanno 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3G018 AB04 AB05 AB16 BA29 BA33 CA12 DA45 DA57 DA70 EA02 EA11 EA17 EA20 FA01 FA07 GA02 3G092 AA01 AA11 AB02 DA09 DF09 DG09 EB02 EB03 EC08 FA06 FA42 HA13Z HE01Z HE03Z HE08Z

Claims (1)

[Claims] 1. A cam provided to vary valve timing of at least one of an intake valve and an exhaust valve of an internal combustion engine and capable of displacing a phase relative to a crankshaft, and detecting an actual phase angle of the cam. Actual phase angle detecting means, operating state detecting means for detecting an operating state of the internal combustion engine, setting means for setting a target phase angle of the cam based on the detected operating state, and supply of operating hydraulic pressure from a hydraulic pressure source A hydraulic actuator that is actuated upon receiving and displaces the phase of the cam; an electromagnetic control valve that is provided in a supply path of the operating oil pressure and controls the supply of the operating oil pressure to the hydraulic actuator; An operation amount for the electromagnetic control valve is set based on a deviation from a target phase angle, and a change in operating characteristics due to a temperature change of the electromagnetic control valve. A variable valve timing control device for an internal combustion engine, comprising: a control unit that corrects the operation amount based on the control value.