JP2011064164A - Cam phase variable type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cam phase variable type internal combustion engine for achieving improvement of control accuracy of a VTC (Variable Timing Control) actuator and the like. <P>SOLUTION: When a first cam angle signal Scm1 is input (namely, just at the moment that a control cam angle is formed), as a current value Pc<SB>n</SB>of a first cam phase is used as a cam phase Pcc<SB>n</SB>for control as it is, a detection error of a conventional device is not generated and a high-precision feedback control is achieved. When a second cam angle signal Scm2 is input, as the cam phase Pcc<SB>n</SB>for control is updated by adding the value calculated by dividing the difference between the current value Pc<SB>n</SB>and a previous value Pc<SB>n-2</SB>of a second cam phase by two (namely, a cam phase intermediate change quantity) to a previous value Pcc<SB>n-1</SB>, accuracy (followability) of the feedback control on sudden change of the cam phase is improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cam phase variable internal combustion engine in which a cam phase is continuously variably controlled, and more particularly to a technique for improving control accuracy of a VTC actuator.

  Many 4-cycle engines (hereinafter simply referred to as engines) are equipped with various variable valve mechanisms in order to improve output and fuel consumption and reduce harmful exhaust gas components. As a variable valve mechanism, a cam phase (shift between the crank angle and the cam angle) and a valve lift are recently used in place of switching a plurality of existing cams (for example, a low speed cam and a high speed cam). Individually variable control is becoming mainstream. A valve timing control device (Variable Timing Control device: hereinafter referred to as VTC) used for variable control of a cam phase is disposed on the shaft center of a vane type VTC actuator, VTC actuator comprising a housing and a rotor, and is hydraulically operated. A spool valve that switches circuits, a linear solenoid that drives the spool of the spool valve in the axial direction, and the like (see Patent Document 1).

  In an engine equipped with a VTC, it is necessary to detect the actual angle (cam angle) of the camshaft in real time by a cam angle sensor in order to perform feedback control of the cam phase. A cam angle sensor generally has a pulsar rotor having a plurality of teeth (pulsar teeth) on the outer periphery and a sensor body (pickup coil, etc.), but various techniques for improving cam angle detection accuracy are proposed. Has been. For example, in Patent Document 1, in a cam phase detection system using two pulsar rotors, two or more pulse signals that cannot be used at a high rotation speed (they are skipped because the phase update period by the pulse and the control period of the ECU are different) are used. A method for preventing aliasing of the pulse signal (appearing to be a value different from the actual value) by averaging is disclosed. Further, in Patent Document 2, the camshaft at the time of opening and closing the valve measures the elapsed time from the reference timing to the timing at which each portion contacts the valve lifter for a predetermined portion in the circumferential direction of the camshaft, and the fluctuation is not remarkable. The theoretical rotation phase is obtained from the elapsed time for each part, and thereby the elapsed time (theoretical value) of the elapsed time for the part with significant fluctuation is estimated, and then at the part with remarkable fluctuation. A method for detecting the difference between the measured value of the elapsed time and the theoretical value as a fluctuation is disclosed.

JP 2005-137320 A JP 2005-61223 A

  In a VTC-equipped engine, the cam phase at a desired timing (for example, when the internal EGR amount is controlled by the exhaust valve) needs to be controlled with high accuracy. However, in the method of Patent Document 1 described above, it is inevitable that a detection error occurs due to oscillation of the VTC actuator (vibration toward the advance side and retard side due to the cam torque). For this reason, when oscillation occurs in the VTC actuator, a plurality of pulse signals may be simultaneously shifted to the advance side (or the retard side). In this case, the averaged pulse signal also has a magnitude of oscillation. Correspondingly, it shifts to the advance side (or the retard side). In the method of Patent Document 2, although the magnitude of oscillation when the cam phase change is relatively small can be detected, the oscillation speed is calculated from the average rotation speed and the elapsed time until the oscillation becomes minimum. In order to estimate the magnitude of the oscillation, it is difficult to accurately detect the magnitude of the oscillation in a situation where the cam phase changes suddenly.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a variable cam phase internal combustion engine that realizes improvement in control accuracy of a VTC actuator.

  According to a first aspect of the present invention, there is provided a VTC actuator used for variable control of a cam phase, crank angle detecting means for detecting a rotation angle of a crankshaft and outputting a crank angle signal, and detecting a rotation angle of a camshaft to detect a plurality of camshaft rotation angles. A cam phase variable internal combustion engine comprising: a cam angle detecting unit that outputs a cam angle signal; and a cam phase setting unit that sets a control cam phase based on the crank angle signal and the cam angle signal. The cam angle detecting means outputs a first cam angle signal when the rotation angle of the cam shaft reaches a control cam angle provided at a predetermined angular interval.

  According to a second aspect of the present invention, in the cam phase variable internal combustion engine according to the first aspect of the invention, the cam angle detecting means has a non-control cam angle in which the cam shaft rotation angle is different from the control cam angle. And further outputting a second cam angle signal, and when the first cam angle signal is inputted, the cam phase setting means calculates a first cam phase from the first cam angle signal and the crank angle signal. When the first cam phase is set as a control cam phase and the second cam angle signal is input, the second cam phase is calculated from the second cam angle signal and the crank angle signal, and the second cam phase signal is calculated. A control cam angle signal is set based on the cam phase and the first cam phase.

  According to a third aspect of the present invention, in the cam phase variable internal combustion engine according to the second aspect of the invention, the non-control cam angle is set at the center of each control cam angle, and the cam phase setting means includes the second cam When an angle signal is input, the cam phase intermediate change amount is calculated by dividing the difference between the current value and the previous value of the second cam phase by 2, and the cam phase intermediate change amount is calculated as the first cam phase change amount. The control cam phase is set by adding to the previous value.

  According to a fourth aspect of the present invention, in the cam phase variable internal combustion engine according to the first to third aspects of the invention, the control cam angle is 0 to 0 when the lift of the valve driven by the camshaft is open or closed. It is set within a range of 2 mm.

  According to the first invention, since the first cam angle signal output when the camshaft rotation angle becomes the control cam angle is used for setting the control cam phase, the oscillation of the VTC actuator is the cam phase. It becomes difficult to influence the feedback control. Further, according to the second and third inventions, the control cam phase is reset (updated) even when the camshaft rotation angle becomes the non-control cam angle. The control followability with respect to the sudden fluctuation of the is improved. According to the fourth aspect of the invention, the control accuracy in the low valve lift region where the change in the internal EGR amount is large is improved.

It is a principal part perspective view of the engine which concerns on embodiment. It is a disassembled perspective view of the VTC actuator which concerns on embodiment. It is an expansion perspective view of the cam angle sensor which concerns on embodiment. It is a flowchart which shows the procedure of the control cam phase setting control which concerns on embodiment. It is a graph which shows the time-dependent change of the actual cam phase and control cam phase which concern on embodiment. It is a graph which shows the setting error of the cam phase for control concerning an embodiment. It is a graph which shows the relationship between the valve lift which concerns on embodiment, and the amount of internal EGR.

Embodiments of a cam phase variable internal combustion engine according to the present invention will be described below in detail with reference to the drawings.
<< Configuration of Embodiment >>
<Overall configuration>
An engine (cam phase variable internal combustion engine) E shown in FIG. 1 is a DOHC 4-valve four-cycle in-line four-cylinder gasoline engine mounted on an automobile. An intake valve 2 for each cylinder is provided in the cylinder head 1. And an exhaust valve 3, an intake camshaft 4 and an exhaust camshaft 5 that drive the intake and exhaust valves 2 and 3. Both camshafts 4 and 5 are rotationally driven by the crankshaft 10 at a rotational speed of 1/2 through the crank sprocket 6, the cam chain 7, the intake cam sprocket 8, and the exhaust cam sprocket 9. The crankshaft 10 is connected to the piston 12 via a connecting rod 11 and drives an oil pump 14 installed obliquely downward via a chain 13. A VTC actuator 21 is attached to the front end of the exhaust camshaft 5, and hydraulic oil supply oil for supplying hydraulic oil (engine oil) from the oil pump 14 to the cylinder head 1 and the cylinder block 15 to the VTC actuator 21. A path 16 is formed.

  A crank angle sensor 17 that detects the rotation angle of the crankshaft 10 is installed in the vicinity of the crank sprocket 6, and a cam angle sensor 18 that detects the cam phase is installed at the rear end of the exhaust camshaft 5. These sensors 17 to 18 are connected to the engine ECU 20 together with many other sensors (intake air temperature sensor, water temperature sensor, accelerator sensor, etc.), and the engine ECU 20 operates based on these detection signals (operation information). (Fuel injection amount, ignition timing, exhaust side cam phase, etc.) are set, and the VTC actuator 21 and the like are driven and controlled in addition to a fuel injection valve and an ignition device (not shown).

<VTC actuator>
As shown in FIG. 2, the VTC actuator 21 includes a housing 22 having an exhaust cam sprocket 9 formed on the outer periphery, a rotor 22 rotatably held in the housing 22, and a rear surface fastened to the front end of the exhaust camshaft 5. 23, a front plate 24 covering the front surface of the housing 22, a back plate 25 covering the rear surface of the housing 22, a reed valve 26 disposed on the inner peripheral side of the front plate 24, and a reed valve cover 27 for fixing the reed valve 26 to the rotor 23. , A bias spring 28 that relatively rotates the housing 22 and the rotor 23 in the advance direction, a spool valve 29 installed at the shaft center, a linear solenoid 31 that drives the spool valve 29 by being controlled by the engine ECU 20, and the rotor 23 Lock pin 3 held on The lock pin spring 34 biases the lock pin 33 toward the back plate 25, the bypass valve 36 held by the rotor 23, the bypass valve spring 37 biases the bypass valve 36 toward the back plate 25, and the like. . The spool valve 29 includes a valve sleeve 38 held at the center of the exhaust camshaft 5 and the rotor 23, a spool 39 slidably fitted in the valve sleeve 38, and the spool 39 attached to the linear solenoid 31 side. And a return spring 40 that is energized.

<Cam angle sensor>
As shown in FIG. 3, the cam angle sensor 18 includes a pulsar rotor 51 fixed to the rear end of the exhaust camshaft 5 and a sensor main body 52 fixed to the cylinder head 1. On the outer periphery of the pulsar rotor 51, the first to fourth main pulsar teeth 61 to 64 disposed at an angular interval of 90 °, and the main pulsar teeth 61 to 64 are also disposed at an angular interval of 90 °. First to fourth sub pulsar teeth 71 to 74 (the third sub pulsar teeth 73 are not shown in FIG. 3) are projected. In the case of this embodiment, the sensor main body 52 has the first to fourth main pulsar teeth 61 to 64 at the moment when the valve lift becomes 1 mm on the closing side of each cylinder (that is, the moment when the control cam angle is reached). The first cam angle signal Scm1 is approached and the first cam angle signal Scm1 is output, while the second cam angle signal Scm2 is approximated to the first to fourth subpulsates 71 to 74 at the center position of the output timing of the first cam angle signal Scm1. Output

<< Operation of Embodiment >>
As described above, the engine ECU 20 sets various operation control amounts of the engine E based on various operation information, and drives and controls the fuel injection valve, the ignition device, the VTC actuator 21 and the like. In the drive control of the VTC actuator 21, Uses the detection signals of the crank angle sensor 17 and the cam angle sensor 18 to set the control cam phase, and feedback-controls the cam phase of the exhaust camshaft 5 using the control cam phase.

When the engine E is started, the engine ECU 20 repeatedly executes control cam phase setting control whose procedure is shown in the flowchart of FIG. 4 with a predetermined control cycle (for example, 10 ms). When the control cam phase setting control is started, the engine ECU 20 determines whether or not a cam angle signal (first cam angle signal Scm1 or second cam angle signal Scm2) is input from the crank angle sensor 17 in step S1 of FIG. If this determination is No, the control cam phase Pcc _n is kept at the previous value Pcc _n−1 in step S2.

When the cam angle signal is input from the crank angle sensor 17 and the determination in step S1 is Yes, the engine ECU 20 determines the crank angle signal Scr output from the crank angle sensor 17 and the first cam angle input from the cam angle sensor 18. signal SCM1 (or second cam angle signal SCM2) based on the calculated cam phase current value Pc _n at step S3.

Then, the engine ECU20, the cam angle signal inputted this time is equal to or a first cam angle signal Scm1 in step S4, the control cam phase current value Pc _n in step S5 if the decision is Yes and use cam phase Pcc _n.

On the other hand, when the cam angle signal input this time is the second cam angle signal Scm2 and the determination in step S4 is No, the engine ECU 20 sets the control cam phase in step S6 using the following equation.
_{Pcc n = Pcc n-1 +} (Pc n -Pc n-2) / 2
Here, Pcc _n−1 is the previous value of the control cam phase as described above, that is, the first cam phase obtained from the crank angle signal Scr and the first cam angle signal Scm1. _Also, Pc n, _{Pc n-2} is the present value and the immediately preceding value of the second cam phase obtained from the crank angle signal Scr and a second cam angle signal Scm2 _{Prefecture, (Pc n -Pc n-2} ) / 2 is a cam phase intermediate change amount.

As shown in FIG. 5, when it entered the first cam angle signal SCM1 (i.e., the moment when a control cam angle), the current value Pc _n is intact control cam phase Pcc _n of the first cam phase Therefore, the detection error unlike the conventional device described above does not occur, and highly accurate feedback control is realized. When the second cam angle signal Scm2-entered, the difference divided by the two of the current value Pc _n the previous value Pc _n-2 of the second cam phase (i.e., the cam phase intermediate variation) Since the control cam phase Pcc _n is updated by adding to the previous value Pcc _n−1 , the accuracy (follow-up performance) of feedback control at the time of sudden change of the cam phase is improved.

  As shown in FIG. 6, when only the first cam phase is used, the control cam phase is not updated while the first cam angle signal Scm1 is input, so that the setting error of the control cam phase becomes large. However, when the second cam phase is also used, the control cam phase is updated even when the second cam angle signal Scm2 is input, so that the control cam phase setting error can be kept small even when the cam phase suddenly changes. It is done.

  As shown in FIG. 7, when the valve timing is shifted due to oscillation, when the valve lift at the start of the shift is 3 mm or more on the closed side, the amount of change in the internal EGR (EGR sensitivity) is not so large. In the range of 0 to 2 mm on the closed side, the EGR sensitivity becomes very large. In the present embodiment, since the first cam angle signal Scm1 is output at the moment when the valve lift becomes 1 mm on the closing side of each cylinder, the internal EGR amount can be controlled with high accuracy. Note that this is related to the effect of valve lift on the gas amount in the gas amount control by the front-rear pressure difference and opening / closing of the valve, so the same applies to the exhaust valve opening side and the intake valve opening side and closing side. I can say that.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, although the above embodiment is an application of the present invention to an in-line four-cylinder DOHC gasoline engine, it is naturally applicable to a diesel engine or the like, and includes a VTC actuator other than a hydraulic type (such as an electric type). It can also be applied to other engines. In the above embodiment, the first pulse generation unit and the second pulse generation unit are formed in the pulsar rotor. However, only the first pulse generation unit may be used, and in this case, the feedback control accuracy is higher than that of the conventional device. Can be improved. In the above embodiment, one second pulse generator is provided at the center of each first pulse generator. However, a plurality of the second pulse generators are provided at each center to further improve the control accuracy when the cam phase suddenly changes. You may make it plan. In addition, the specific configuration of the engine, the VTC actuator, and the like can be changed as appropriate without departing from the gist of the present invention.

5 Exhaust camshaft 10 Crankshaft 17 Crank angle sensor (Crank angle detection means)
18 Cam angle sensor (cam angle detection means)
20 Engine ECU (cam phase setting means)
21 VTC actuator 51 Pulsar rotor 52 Sensor body 61-64 Main pulsar teeth 71-74 Sub pulsar teeth E Engine

Claims (4)

VTC actuator for variable control of cam phase, crank angle detection means for detecting crankshaft rotation angle and outputting crank angle signal, and detecting camshaft rotation angle and outputting multiple cam angle signals A cam phase variable internal combustion engine comprising: a cam angle detecting means for performing control; and a cam phase setting means for setting a control cam phase based on the crank angle signal and the cam angle signal,
The variable cam phase internal combustion engine, wherein the cam angle detecting means outputs a first cam angle signal when a rotation angle of the cam shaft becomes a control cam angle provided at a predetermined angular interval. The cam angle detection means further outputs a second cam angle signal when the rotation angle of the cam shaft becomes a non-control cam angle different from the control cam angle,
The cam phase setting means includes
When the first cam angle signal is input, after calculating the first cam phase from the first cam angle signal and the crank angle signal, the first cam phase is set as a control cam phase,
When the second cam angle signal is input, a second cam phase is calculated from the second cam angle signal and the crank angle signal, and the control cam is based on the second cam phase and the first cam phase. The cam phase variable internal combustion engine according to claim 1, wherein an angular signal is set. The non-control cam angle is set at the center of each control cam angle,
The cam phase setting means calculates the cam phase intermediate change amount by dividing the difference between the current value and the previous value of the second cam phase by 2, when the second cam angle signal is input, The variable cam phase internal combustion engine according to claim 2, wherein the control cam phase is set by adding an intermediate phase change amount to the previous value of the first cam phase.   The control cam angle is set in a range in which a lift of a valve driven by the camshaft is 0 to 2 mm on an opening side or a closing side. The cam phase variable internal combustion engine described in the paragraph.

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