JP2015175260A - Valve actuating mechanism - Google Patents

Abstract

The structure of a variable valve mechanism of an internal combustion engine can be simplified and simplified, can be easily incorporated into a valve mechanism of an internal combustion engine of a prior art, and does not require a large design change. Provide a valve mechanism.
In a variable valve mechanism of an internal combustion engine, a piezoelectric element 17a is provided in a part of a displacement conversion mechanism that converts a displacement from a cam 15 into an axial displacement of a valve shaft 12a, and a low valve lift. When opening and closing the valve 12 by an amount, the piezoelectric element 17a is not volume-expanded, and when opening and closing the valve 12 by a high valve lift, a voltage is applied to the piezoelectric element 17a to cause volume expansion.
[Selection] Figure 1

Description

  The present invention relates to a variable valve mechanism for an internal combustion engine that lifts a valve of an intake valve or an exhaust valve by a cam provided on a cam shaft.

  A variable valve mechanism for an internal combustion engine that lifts an intake valve or an exhaust valve through a rocker arm by a cam provided on a cam shaft opens and closes the intake valve and the exhaust valve in accordance with the combustion cycle of the engine. The engine output is optimized by changing the valve lift amount according to the operating state of the engine. For example, when the engine is rotating at a high speed, the amount of air introduced into the cylinder due to an increase in the engine output is increased by changing the valve lift amount of the intake valve and the exhaust valve to be larger than when the engine is rotating at a low speed. This corresponds to an increase in the amount of exhaust gas discharged from the cylinder.

  An example of the prior art of this variable valve mechanism for an internal combustion engine is shown in FIGS. FIG. 5 shows a case where the valve lift amount of the intake or exhaust valve is low (low lift), and FIG. 6 shows a case where the valve lift amount is high (high lift). As shown in FIGS. 5 and 6, the variable valve mechanism 10X of the internal combustion engine includes a cam shaft 14, a cam 15, a center rocker arm 18X, a rocker arm 16, and a motor for driving a control shaft 16a of the rocker arm 16 ( (Not shown), a structure including a swing cam 19X, a valve 12, and the like.

  At the time of low lift, when the cam shaft 14 rotates, the cam crest movement of the cam 15 is transmitted to the center rocker arm 18X, the rocker arm 16, and the valve 12, and the valve 12 is lifted. On the other hand, at the time of high lift, the control shaft 16a is rotated by a motor to move the position of the fulcrum 18Xa of the center rocker arm 18X from point A (FIG. 5) to point B (FIG. 6). Thereby, the rotation amount of the center rocker arm 18X is increased, and the valve lift amount of the valve 12 is increased. The swing cam 19X restricts the movement of the center rocker arm 18X.

  However, in such a variable valve mechanism 10X for an internal combustion engine, parts such as a swing cam 19X and a center rocker arm 18X are additionally required for a valve mechanism having a constant valve lift amount. Since it is necessary to arrange the cam shaft 14 above, there is a problem of taking a space.

  On the other hand, in a hydrogen engine in which the amount of hydrogen supplied to the engine is controlled by a pressure control valve provided in the hydrogen supply pipe and a hydrogen supply valve that can control lift and opening time, There has been proposed a fuel control method in a hydrogen engine in which piezoelectric elements are stacked and controlled by an electrostrictive actuator that increases the thickness in accordance with an applied voltage (see, for example, Patent Document 1).

  However, in this fuel control method for a hydrogen engine, a method for controlling a hydrogen supply valve using a piezo element has been proposed, but there is no description or suggestion that a piezo element is used for a valve operating mechanism of an internal combustion engine.

JP-A-4-318264

  The present invention has been made in view of the above, and an object of the present invention is to simplify and simplify the structure of a variable valve mechanism of an internal combustion engine. It is an object of the present invention to provide a variable valve mechanism for an internal combustion engine that is easy to incorporate into the engine and does not require a large design change.

  In order to achieve the above object, a variable valve mechanism for an internal combustion engine according to the present invention includes a valve from an intake valve or an exhaust valve of an internal combustion engine that is closed by a biasing force of a valve spring, A variable valve operating mechanism for an internal combustion engine that converts the displacement directly or indirectly into the axial displacement of the valve shaft, opens the valve against the urging force of the valve spring, and varies the valve lift amount. In this embodiment, a piezoelectric element is provided in a part of a displacement conversion mechanism that converts displacement from the cam into axial displacement of the valve shaft, and when the valve is opened and closed with a low valve lift amount, When the valve is opened and closed with a high valve lift amount without volume expansion of the element, a voltage is applied to the piezoelectric element to expand the volume.

  According to this configuration, a voltage control device that realizes a low valve lift amount with only a cam, provides a piezoelectric element (piezo element) in a part of the displacement conversion mechanism, and applies a voltage for volume expansion of the piezoelectric element. The valve mechanism of the internal combustion engine can be changed to a variable valve mechanism of the internal combustion engine, so that the structure of the variable valve mechanism of the internal combustion engine is not required without requiring parts such as a center rocker arm and a swing cam. It can be simplified and simplified.

  In addition, since only a piezoelectric element is incorporated into a part of the displacement conversion mechanism of the valve mechanism of the internal combustion engine or a part of the displacement conversion mechanism is formed of a piezoelectric element, the valve mechanism of the conventional internal combustion engine is also used. Easy to integrate and does not require major design changes.

  Further, since the high valve lift amount is realized by adding the displacement amount due to the volume expansion of the piezoelectric element to the lift amount of the cam, the expansion amount of the piezoelectric element is the difference between the high valve lift amount and the low valve lift amount. Therefore, the volume expansion amount of the piezoelectric element required for high valve lift can be significantly reduced as compared with the case where the valve is lifted only by the volume expansion amount of the piezoelectric element without using a cam.

  In the variable valve mechanism of the internal combustion engine, when the valve is opened and closed with a high valve lift amount, the valve lift amount based only on the cam is applied during the volume expansion period by applying a voltage to the piezoelectric element. The valve lift amount set in the range of 30% to 100%, preferably 50% to 100%, more preferably 80% to 100% of the maximum valve lift amount by the cam alone is exceeded. When configured to be only during the period, the following effects can be achieved.

  In other words, if the volume expansion of the piezoelectric element is continued even when the valve is seated or at the cam angle in the vicinity of the valve, the valve may not be seated on the valve seat, and a gap may be created and the valve cannot be completely closed. In order to prevent this, the voltage application period to the piezoelectric element is limited to a period exceeding the set valve lift amount, and the piezoelectric element is only in a region where the valve lift amount is relatively high by the cam. The valve lift amount is increased by adding an increase in displacement due to the volume expansion. Accordingly, when the valve is seated, the valve lift amount of which is relatively low due to the cam, the valve lift amount is obtained only by the cam, so that the seat can be seated reliably and the valve can be completely closed.

  The larger the set valve lift amount, that is, the closer to 100%, the shorter the voltage application period, which is preferable in terms of energy saving, but the valve lift curve does not become smooth. It is set according to the target valve lift curve.

  In the variable valve mechanism of the internal combustion engine described above, when a part of the displacement conversion mechanism includes a bridge, if part or all of the bridge is formed of the piezoelectric element, an increase in displacement due to volume expansion of the piezoelectric element. Since the amount remains the same as the increased displacement amount of the high valve lift added to the displacement amount of the cam, the calculation of the displacement increase amount is simplified and the design of the piezoelectric element is remarkably simplified.

  According to the variable valve mechanism for an internal combustion engine of the present invention, a low valve lift amount is realized only by a cam, a piezoelectric element (piezo element) is provided in a part of the displacement conversion mechanism, and the piezoelectric element is volume-expanded. Since the valve operating mechanism of the internal combustion engine can be changed to a variable valve operating mechanism simply by providing a voltage control device that applies the above voltage, components such as a swing cam and a center rocker arm are not required. The structure can be simplified and simplified. In addition, since a piezoelectric element is incorporated into a part of the displacement conversion mechanism of the valve mechanism or a part of the displacement conversion mechanism is formed of a piezoelectric element, it is easy to incorporate into a valve mechanism of an internal combustion engine of the prior art. Also, no major design changes are required.

It is a figure which shows typically the structure of the variable valve mechanism of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the high valve lift and low valve lift of an intake valve at the time of using the variable valve mechanism of the internal combustion engine of embodiment which concerns on this invention. It is a figure which shows the application condition of the voltage to the piezoelectric element in a high valve lift. It is a figure which shows an example of the valve mechanism of the internal combustion engine which concerns on a prior art. It is a figure which shows the state of the low valve lift of the valve | bulb of an intake valve or an exhaust valve by the variable valve mechanism of the internal combustion engine which concerns on a prior art. It is a figure which shows the state of the high valve lift of the valve | bulb of an intake valve or an exhaust valve by the variable valve mechanism of the internal combustion engine which concerns on a prior art.

  Hereinafter, a variable valve mechanism for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. Here, the description will be made based on an OHC type valve mechanism, but the present invention is not limited to this, and can be applied to an OHV type valve mechanism or the like.

  First, in order to clarify the difference between the present invention and the prior art, a valve mechanism 10Y for an internal combustion engine according to the prior art as shown in FIG. 4 will be described. The valve mechanism 10Y is not a variable valve mechanism as in the present invention, and the valve lift amount is constant, and the intake valve or exhaust valve 12 disposed inside the cylinder head cover 11 and the cylinder head 20 is used as a valve. The valve is closed by the urging force of the spring 13, and the displacement from the cam 15 fixed to the cam shaft 14 is transmitted to the bridge 17Y through the rocker arm 16 against the urging force, and the valve is displaced by the displacement of the bridge 17Y. This is a valve operating mechanism that opens the valve 12 by displacing the shaft 12a in the axial direction.

  That is, the valve 12 of the intake valve or the exhaust valve of the internal combustion engine is closed by the urging force of the valve spring 13, and the displacement from the cam 15 fixed to the cam shaft 14 is indirectly changed via the rocker arm 16 of the valve shaft 12a. Converting to an axial displacement, the valve 12 is opened against the urging force of the valve spring 13.

  Since the valve lift of the valve 12 is not changed in the valve mechanism 10Y, the center rocker arm 18X and the swing cam 19X of the variable valve mechanism 1X shown in FIGS. 5 and 6 are not provided.

  As shown in FIG. 1, the variable valve mechanism 10 according to the embodiment of the present invention is a part of a displacement conversion mechanism that converts the displacement of the cam 15 into the axial displacement of the valve shaft 12a. The bridge 17 that transmits the displacement of the rocker arm 16 to the two valve shafts 12a is provided with a piezoelectric element (piezo element) 17a.

  In other words, the piezoelectric element 17a is incorporated in the bridge 17Y of the valve mechanism 10Y of the internal combustion engine shown in FIG. 4, or a part or all of the bridge 17Y is replaced with the bridge 17 formed of the piezoelectric element 17a. In FIG. 1, the valve spring 13 is omitted for the sake of clarity.

  If a part or all of the bridge 17 is formed by the piezoelectric element 17a, the displacement increase amount due to the volume expansion of the piezoelectric element 17a becomes the increase displacement amount of the high valve lift added to the displacement amount of the cam 15, so the displacement increase amount This simplifies the calculation and makes it easy to control the applied voltage, and the design of the piezoelectric element 17a is greatly simplified.

  In the case where the bridge 17 is not provided, the piezoelectric element 17a is disposed at a portion where the valve shaft 12a and the rocker arm 16 are in contact with each other, or a part of the upper end side (the side opposite to the valve body) of the valve shaft 12a. Is formed by the piezoelectric element 17a.

  Further, when the voltage control device 21 for controlling the voltage applied to the piezoelectric element 17a is provided and the valve 12 is opened and closed with a low valve lift amount, the piezoelectric element 17a is not volume-expanded without applying a voltage to the piezoelectric element 17a. On the other hand, when the valve 12 is opened and closed with a high valve lift, a voltage is applied to the piezoelectric element 17a from the voltage control device 21 to expand the volume of the piezoelectric element 17a.

  For example, when the operating state of the internal combustion engine is low load or low rotation and the valve is opened and closed with a low valve lift, the valve 12 is lifted only by the displacement of the cam 15 without applying a voltage to the piezoelectric element 17a. When the operating state of the internal combustion engine is high load or high rotation and the valve is opened and closed with a high valve lift, a voltage is applied to the piezoelectric element 17a to expand the volume, and in addition to the displacement amount of the cam 15, the piezoelectric element 17a The displacement due to the volume expansion is added to increase the valve lift amount of the valve 12. That is, the valve lift amount of the valve 12 is changed by changing the volume expansion by changing the magnitude of the voltage applied to the piezoelectric element 17a according to the operating state of the internal combustion engine.

  According to this configuration, the piezoelectric element 17a is incorporated into a part of the displacement conversion mechanism, that is, the bridge 17 interposed between the rocker arm 16 and the valve shaft 12a, or a part or all of the bridge 17 is incorporated. Can be changed to the variable valve mechanism 10 of the internal combustion engine, so that the variable valve mechanism of the internal combustion engine as shown in FIG. 5 and FIG. 6 is formed. Parts such as the 10X swing cam 19X and the center rocker arm 18X are not required, and the structure of the variable valve mechanism 10 of the internal combustion engine can be simplified and simplified.

  In addition, since the piezoelectric element 17a is incorporated into a part of the bridge 17 of the displacement conversion mechanism or only a part of the displacement conversion mechanism is formed of the piezoelectric element 17a, it can be easily incorporated into the valve mechanism of the internal combustion engine of the prior art. Does not require major design changes.

  Further, since the high valve lift amount is realized by adding the displacement amount resulting from the volume expansion of the piezoelectric element 17a to the lift amount of the cam 15, the displacement amount due to the volume expansion required for the piezoelectric element 17a is high. Since there is a difference between the lift amount and the low valve lift amount, the volume expansion amount of the piezoelectric element 17a required for high valve lift is lifted by using only the volume expansion amount of the piezoelectric element without using the cam 15. Compared to the case, it can be remarkably reduced.

  Further, in the variable valve mechanism 10 of the internal combustion engine, when the valve 12 is opened and closed with a high valve lift amount, as shown in FIGS. 2 and 3, a period T1 in which a voltage is applied to the piezoelectric element 17a to expand the volume. The valve lift amount by the cam 15 alone is set within the range of 30% to 100%, preferably 50% to 100%, more preferably 80% to 100% of the maximum valve lift amount by the cam 15 alone. It is configured so that it is only during a period in which the set valve lift amount is exceeded.

  That is, even when the valve 12 is seated or at a cam angle in the vicinity thereof, if the volume expansion of the piezoelectric element 17a is continued, the valve 12 does not seat on the valve seat (not shown), and the valve 12 and the valve seat There is a case where a gap is generated between the two and the valve cannot be completely closed. In order to prevent this, a region where the valve lift amount (thin line) is relatively high by the cam 15 by limiting the voltage application period T1 to the piezoelectric element 17a to a period exceeding the set valve lift amount L1. The valve lift amount (thick line in FIG. 2) is increased by adding an increase ΔL in displacement due to volume expansion of the piezoelectric element 17a. Therefore, when the valve 12 is seated, the valve lift amount (thin line in FIG. 2) is obtained only by the cam 15, so that the seat can be seated reliably and the valve 12 can be completely closed.

  The larger the set valve lift amount L1, that is, the closer to 100%, the shorter the voltage application period T1, so it is preferable to increase the set valve lift amount L1 from the viewpoint of energy saving. Since the valve lift curve that is the relationship between the rotation angle and the valve lift amount is difficult to be smooth, the value of the set valve lift amount L1 is set according to the target valve lift curve.

  Further, by gradually increasing or decreasing the magnitude of the voltage applied to the piezoelectric element 17a, the valve lift curve (thin line and thick line) can be made smooth as shown by the dotted line in FIG. When it is necessary to smooth the valve lift curve, the magnitude of the voltage applied to the piezoelectric element 17a is changed gradually or stepwise as indicated by the dotted line shown in FIG.

  In the variable valve mechanism 10 of the internal combustion engine of this embodiment, the bridge 17 is provided with the piezoelectric element 17a. However, the increase in displacement due to the volume expansion of the piezoelectric element 17a is replaced with an increase in the axial displacement of the valve shaft 12a. In the case of the OHC (overhead camshaft) type, the location where the piezoelectric element 17a is provided is not limited to the bridge 17, and for example, the rocker arm 16 and the cam 15 may be provided with a piezoelectric element. Further, a part of the cam nose, a part of the rocker arm 16 that contacts the cam 15, a part of the rocker arm 16 that contacts the bridge 17, and the like can be considered.

  Further, in the case of an OHV (overhead valve system) type valve operating mechanism, the piezoelectric element is provided at a location such as a cam nose, tappet, push rod, rocker arm, a contact portion between these members, a cam And between the rocker arm and the valve shaft.

  In the case of a lifter system in which the cam is in contact with a lifter provided on one end side of the valve shaft, a cam nose, a lifter or the like can be considered as a place where the piezoelectric element is provided.

  Therefore, according to the variable valve mechanism 10 of the internal combustion engine of the embodiment according to the present invention, a low valve lift amount is realized only by the cam 15, the piezoelectric element 17a is provided in a part of the displacement conversion mechanism, and this piezoelectric Since the valve mechanism of the internal combustion engine can be changed to the variable valve mechanism 10 simply by providing the voltage control device 21 for applying a voltage for volume expansion of the element 17a, the center as shown in FIGS. Parts such as the rocker arm 18X and the swing cam 19X are not required, and the structure of the variable valve mechanism 10 of the internal combustion engine can be simplified and simplified.

  In addition, since the piezoelectric element 17a is incorporated into a part of the displacement conversion mechanism of the valve mechanism or a part of the displacement conversion mechanism is formed of the piezoelectric element 17a, it is also incorporated into the valve mechanism of the conventional internal combustion engine. It is easy and does not require major design changes.

10, 10X Variable valve mechanism 10Y of internal combustion engine Valve mechanism 11 of internal combustion engine Cylinder head cover 12 Valve 12a Valve shaft 13 Valve spring 14 Cam shaft 15 Cam 16 Rocker arm 17, 17Y Bridge 18X Center rocker arm 18Xa Center rocker arm fulcrum 19X Swing cam 20 Cylinder head

Claims (3)

The valve of the intake valve or the exhaust valve of the internal combustion engine is closed by the urging force of the valve spring, and the displacement from the cam fixed to the camshaft is directly or indirectly converted into the displacement in the axial direction of the valve shaft. In the variable valve mechanism of the internal combustion engine that opens the valve against the biasing force of the spring and varies the valve lift amount,
While providing a piezoelectric element in a part of a displacement conversion mechanism that converts the displacement from the cam into the axial displacement of the valve shaft,
When opening and closing the valve with a low valve lift amount, the piezoelectric element is not volume-expanded, and when opening and closing the valve with a high valve lift amount, a voltage is applied to the piezoelectric element to expand the volume. A variable valve mechanism for an internal combustion engine.   When opening and closing the valve with a high valve lift amount, the valve lift amount by the cam alone is 30% or more of the maximum valve lift amount by the cam alone during the volume expansion period by applying a voltage to the piezoelectric element. 2. The variable valve mechanism for an internal combustion engine according to claim 1, wherein the variable valve mechanism is set only during a period exceeding a set valve lift set within a range of 100% or less.   The variable valve mechanism for an internal combustion engine according to claim 1 or 2, wherein a part or all of the bridge is formed by the piezoelectric element when a part of the displacement conversion mechanism includes a bridge.

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