KR20030046689A - Engine having a continuously variable valve timing apparatus and method for the same - Google Patents

Abstract

PURPOSE: An engine equipped with a continuously variable valve time apparatus and a method for controlling the same are provided to simplify a structure of the engine and to reduce a non-operation area of the continuously variable valve time apparatus by removing an automatic tensioner. CONSTITUTION: An engine includes a cam shaft pulley(33) connected to a crank shaft pulley(31) through a belt(32). One end of an exhaust cam shaft(34) is supported by the cam shaft pulley. A continuously variable valve time apparatus(35) is installed at the other end of the exhaust cam shaft. An intake cam shaft(36) is provided corresponding to the exhaust cam shaft. A power transmission is provided to drive the intake cam shaft by connecting the intake cam shaft to the exhaust cam shaft. The power transmission includes a first sprocket, a second sprocket, and a chain connected to the first and second sprockets.

Description

ENGINE HAVING A CONTINUOUSLY VARIABLE VALVE TIMING APPARATUS AND METHOD FOR THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine employing a continuous variable valve timing device and a control method thereof. More specifically, the variable variable timing device includes a continuously variable valve timing device, which simplifies a structure and improves engine performance. And a control method thereof are employed.

In recent years, variable intake and exhaust valves have been proposed that can vary the timing of opening and closing the valve according to the operating conditions of the engine to achieve the optimum output and fuel economy, and are also applied to actual vehicles.

One example is shown in FIG. As shown, a VVT unit (Variable Valve Timing Unit) 6 is disposed inside the sprocket 4 formed at the front end of the intake camshaft 2, and the VVT unit 6 includes an oil flow control valve (OCV); An oil flow control valve 8 is included, and the oil flow control valve 8 changes the flow path of the hydraulic pressure supplied from the oil pump 10 to the VVT unit 6.

Although not shown in the drawing, the VVT unit 6 is composed of a housing integrally formed with the sprocket 4 and a rotor vane formed integrally with the camshaft 2 and positioned inside the housing.

However, the conventional CVVT system made as described above requires an increase in the capacity of the oil pump 10 for driving an automatic tensioner for adjusting the tension of the timing belt, and increases the capacity of the oil pump 10. Engine friction increases due to the deterioration of the engine performance.

In addition, a timing belt guide must be fitted to prevent the bite angle from falling over the teeth of the belt. Engines without CVVT are designed so that the valve and piston do not collide when the timing belt is pulled over two teeth.

However, in the case of the CVVT engine, the valve timing is advanced by 30 ° or more as compared to the engine without the CVVT and the upper portion of the piston is penetrated when the valve pocket is formed in the piston accordingly.

Therefore, in the case of the CVVT engine, if the timing belt is over one tooth, the valve and the piston collide, and the entire engine is destroyed. That is, there is a possibility that the belt teeth fall structurally, if the belt teeth fall, there is a possibility that the valve and the piston collides, the entire engine is damaged in series.

As shown in FIGS. 2 and 3, in the case of a cam to cam type, the chain 11, by an interference fit, in which the distance between the camshafts is longer than the length of the chains 11 and 21, is used. Maintain the tension of 21). In such a structure, the tension variation of the chains 11 and 21 is very large due to the length tolerance between the chains 11 and 21 and the camshaft axis distance.

And the required tension of the chains 11 and 21 for operating the CVVT should be kept below 500N. Therefore, all engines equipped with CVVT are equipped with auto tensioners 12 and 22 to maintain the required tension of the drive chains 11 and 21 at 500 N or less. In addition, in order to mount the auto-tensioner (12, 22), the distance between the shaft head of the cylinder head must be changed, and when the distance between the cylinder head shaft is changed, a significant modification of the current processing line equipment is inevitable, and a huge investment cost must be added.

4 shows a graph for the CVVT non-operation area. As shown, when the camshaft chain tension is very high (more than 500N), CVVT does not operate in the whole operating range, but CVVT does not operate in the low RPM section where the oil pressure drops and in the high temperature condition where the oil viscosity decreases. .

In this low RPM, high temperature range, the CVVT does not work even if the ECU commands the CVVT. Engine conditions in the CVVT non-operational section result in engine NVH deterioration and performance deterioration due to valve timing instability. In addition, the emission deterioration occurs due to the elimination of valve overlap, and the engine warning lamp is turned on to indicate that the CVVT is inactive according to North American OBD-II regulations.

The present invention was created to solve the above problems, and the engine and its control employing a continuous variable valve timing device to simplify the structure, reduce the investment cost, and reduce the non-operating area of the CVVT by not installing an auto tensioner. The purpose is to provide a method.

1 is a view schematically showing the configuration of an engine employing a continuous variable valve timing apparatus according to the prior art.

2 and 3 are views showing a state in which the auto tensioner is employed in a typical cam-to-cam type.

4 is a graph showing a typical CVVT non-operation area.

5 is a view schematically showing a configuration of an engine employing a continuous variable valve timing apparatus according to the present invention.

6 is a schematic flowchart showing an engine control method employing a continuous variable valve timing apparatus according to the present invention.

FIG. 7 is a graph showing the CVVT non-operation area compared to FIG. 4. FIG.

<Description of the symbols for the main parts of the drawings>

31. Crankshaft Pulley

32. Belt

33. Camshaft Pulley

34. Exhaust Cam Shaft

35.CVVT

36.Intake Cam Shaft

The engine employing the continuous variable valve timing apparatus of the present invention for achieving the above object, the crankshaft pulley and the cam shaft pulley connected to enable power transmission by the belt; An exhaust cam shaft having one end supported by the cam shaft pulley; A CVVT provided at the other end of the exhaust cam shaft; An intake cam shaft installed corresponding to the exhaust cam shaft; And a power transmission device for connecting the intake cam shaft and the exhaust cam shaft to drive the intake cam shaft.

An engine control method employing a continuous variable valve timing apparatus of the present invention for achieving the above object comprises the steps of: (a) the ECU of the vehicle recognizes the non-operation area of the CVVT; (b) if the ECU recognizes the non-operation area of the CVVT in step (a), performing OBD-II control.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a schematic diagram showing an engine employing a continuous variable valve timing apparatus according to the present invention.

Referring to the drawings, an engine employing a continuous variable valve timing apparatus according to the present invention includes a camshaft pulley 33 connected to a crankshaft pulley 31 and a belt 32 so as to enable power transmission, and the camshaft pulley. An exhaust cam shaft 34 having one end supported by the 33, a CVVT 35 provided at the other end of the exhaust cam shaft 34, and an intake cam shaft 36 provided corresponding to the exhaust cam shaft 34. And a power transmission device for connecting the intake cam shaft 36 and the exhaust cam shaft 34 to drive the intake cam shaft 36.

The power transmission device includes a first sprocket 41 installed at the exhaust cam shaft 34 to the rear of the CVVT 35, a second sprocket 42 provided at an end of the intake cam shaft 36, and the first sprocket 41. It is configured to include a chain 43 installed connected to the two sprockets (41, 42).

As described above, in the engine employing the continuous variable valve timing apparatus according to the present invention, the CVVT 35 installed at the end of the exhaust cam shaft 34 is configured to move the intake cam shaft 36 to the power transmission device, that is, the chain 43 and the first. It is driven by 1,2 sprockets 41 and 42. In addition, since the auto tensioner is not installed in the chain 43, the investment cost of mounting the auto tensioner is reduced.

In addition, since the auto tensioner is not installed, the oil pump capacity is reduced by removing the auto tensioner, thereby reducing engine friction loss, thereby improving engine performance. In addition, the timing belt has a sufficient bite angle, which eliminates the need for a timing belt guide.

Referring to the control method of the engine employing the continuous variable valve timing apparatus according to the present invention having the configuration as described above is as follows.

6 is a flowchart sequentially showing an engine control method employing a continuously variable valve timing apparatus according to the present invention.

Referring to the drawings, firstly, the ECU of the vehicle recognizes the non-operation area of the CVVT. (Step 10)

When the ECU recognizes the non-operation area of the CVVT in step 10, OBD-II control is performed (step 20). Accordingly, the lighting of the MIL is prevented.

When the ECU recognizes the non-operating area of the CVVT in step 10, the fuel injector is operated (step 30). Then, the fuel amount (or air-fuel ratio) is controlled (step 40). To prevent deterioration.

In addition, when the ECU recognizes the non-operation area of the CVVT in step 10, the oil control valve (OCV) is operated (step 50).

The CVVT is reset and the valve timing is retarded (step 60). This improves idle stability.

If the ECU does not recognize the non-operation area of the CVVT in step 10, it determines whether the vehicle engine is low, medium, or high speed (steps 110, 120, and 130).

In steps 110, 120 and 130, the CVVT is operated according to the low, medium and high speeds of the engine. For example, when the engine speed is low as in step 110, the CVVT is operated and the intake valve closing time is advanced (step 111). This will improve your emissions.

If the engine speed is medium, as in step 120, the CVVT is operated and the intake valve opening time is advanced (step 121). Accordingly, the engine performance is improved and fuel economy is improved.

In addition, when the engine speed is high, as in step 130, the CVVT is operated and the intake valve closing time is perceived (step 131). Accordingly, the performance of the engine can be increased.

6 and 7, in the ECU control logic for eliminating the problem caused by the CVVT non-operation area generation, the CVVT non-operation area map is an oil temperature of 120 ° C. at 1200 rpm or less, and an oil at 1000 rpm or less. The temperature is 100 ° C.

In addition, in the CVVT non-operation region, the valve timing is perceived as an initial state, and emission control is performed to secure combustion stability by controlling the fuel amount in the CVVT non-operation region.

In addition, by managing the distance between the chain and the cylinder head shaft, the intake cam driving torque is reduced, and the CVVT non-operating section is reduced.

As described above, the engine control method employing the continuous variable valve timing apparatus according to the present invention is to improve the problem of the conventional CVVT non-operation section, and when the engine enters the CVVT non-operation condition in the ECU, the CVVT is idled. By injecting the optimum amount of fuel that meets these conditions, combustion stability is ensured, emission deterioration is prevented, and power degradation is controlled to a level that the driver cannot feel.

In addition, the chain and cylinder head shaft distance can be managed to reduce the CVVT non-operation area by reducing the chain tension without increasing the defective rate.

As described above, the engine employing the continuous variable valve timing apparatus and the control method thereof according to the present invention have the following effects.

The absence of an auto tensioner simplifies the structure, reduces the investment, and improves engine performance with the CVVT.

In addition, it is possible to improve the performance of the engine by reducing the engine friction by reducing the capacity of the oil pump.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (8)

A camshaft pulley connected to the crankshaft pulley and the belt to enable power transmission; An exhaust cam shaft having one end supported by the cam shaft pulley; A CVVT provided at the other end of the exhaust cam shaft; An intake cam shaft installed corresponding to the exhaust cam shaft; And a power transmission device connecting the intake cam shaft and the exhaust cam shaft to drive the intake cam shaft. The method of claim 1, The power transmission device, A first sprocket installed on the exhaust cam shaft behind the CVVT; A second sprocket installed at an end of the intake cam shaft; And a chain installed to be connected to the first and second sprockets. (a) the ECU of the vehicle recognizing the non-operation area of the CVVT; and (b) performing OBD-II control when the ECU recognizes the non-operation area of the CVVT in step (a). The method of claim 3, (c) operating the fuel injector when the ECU recognizes the non-operation area of the CVVT in step (a); (d) controlling the amount of fuel; the engine control method employing the continuous variable valve timing device further comprising. The method of claim 3, (e) operating the oil control valve when the ECU recognizes the non-operation area of the CVVT in step (a); (f) resetting the CVVT and recognizing the valve timing. The engine control method according to claim 1, further comprising the step of resetting the CVVT. The method of claim 3, (g) if the ECU does not recognize the non-operation area of the CVVT in step (a), determining whether the vehicle engine is low, medium, or high speed, respectively; (h) operating the CVVT according to the low, medium and high speeds of the engine in step (g); (i) advancing a closing time of the intake valve when the engine speed is low in the step (g); and the continuous variable valve timing device is adopted. The method of claim 6, (j) advancing the intake valve opening time when the engine speed is medium speed in the step (g); further comprising a continuous variable valve timing apparatus. The method of claim 6, and (k) retarding the intake valve closing time if the engine speed is high in step (g).