Patent Grant
10107145
This is a national phase application based on the PCT International Patent Application No. PCT/JP2015/051697 filed Jan. 22, 2015, claiming priority to Japanese Patent Application No. 2014-009802 filed Jan. 22, 2014, the entire contents of both of which are incorporated herein by reference.
The present invention relates to an adjustable valve device of an internal combustion engine.
In a device disclosed in Patent Document 1, a camshaft penetrates through an elongated hole formed in a movable cam. This allows the movable cam to eccentrically rotate in relation to the camshaft, and to reciprocate in a radial direction by a reactive force received from a valve in response to the rotation of the camshaft. A plunger that is biased by a spring and extends by the effect of hydraulic pressure is located between the camshaft and the movable cam. When the hydraulic pressure is not exerted, the plunger extends and contracts, and the movable cam is allowed to reciprocate in the radial direction with respect to the camshaft. When the hydraulic pressure is exerted, the plunger is maintained at the extended state, and the position of the movable cam relative to the camshaft is fixed.
[Patent Document 1] Japanese Patent Application Publication No. 2001-329819
In the device of Patent Document 1, since the camshaft penetrates through the elongated hole of the movable cam, it may be considered to employ a thin camshaft to secure the movable range of the movable cam. However, the thin camshaft may reduce the rigidity.
Therefore, the present invention aims to provide an adjustable valve device of an internal combustion engine that prevents reduction of the rigidity of a camshaft.
The aforementioned objective is achieved by an adjustable valve device of an internal combustion engine including: a first cam portion that is penetrated by a camshaft, rotates together with the camshaft, and includes an elongated hole formed therein; a second cam portion that is formed into approximately U-shape or approximately L-shape, and is supported by the first cam portion so as to swing to move between a first state where the second cam portion is located at a position where the second cam portion protrudes from an outer peripheral surface of the first cam portion and a second state where the second cam portion is located at a position lower than a position in the first state; a stopper pin that is fixed to the second cam portion and penetrates through the elongated hole; a biasing member that intervenes between the first cam portion and the second cam portion, and biases the stopper pin so that the second cam portion is in the first state; a lock mechanism that locks the second cam portion only when the second cam portion is in the first state; and a cam follower that exerts a reactive force on the second cam portion so that the second cam portion is in the second state in a state where a lock of the second cam portion is released, wherein the reactive force is greater than a biasing force of the biasing member.
The lock mechanism may be configured to include: a first engagement hole that is formed in the first cam portion; a second engagement hole that is formed in the second cam portion, and faces the first engagement hole in the first state; a pressing member that is accommodated in the first engagement hole; a lock member that is accommodated in the second engagement hole; a lock member biasing member that biases the lock member so that the lock member engages with the first and second engagement holes in the first state; and a passage that communicates with the first engagement hole, and exerts hydraulic pressure on the pressing member so that the lock member is disconnected from the first engagement hole against a biasing force of the lock member biasing member in the first state.
The first and second engagement holes may be configured to extend in an axial direction of the camshaft.
The second cam portion may be configured to include: a first inclined surface that protrudes from an outer peripheral surface of the first cam portion in the first state; and a second inclined surface that partially coincides with the outer peripheral surface of the first cam portion as viewed from an axial direction of the camshaft in both the first and second states.
The second cam portion may be configured to move from the second state to the first state while the first and second cam portions contact with the cam follower in accordance with rotation of the camshaft in the state where the lock of the second cam portion is released.
The second cam portion may be configured to include: an inclined surface located at a valve opening side of the second cam portion; and an inclined surface located at a valve closing side of the second cam portion, and a fulcrum point of swing of the second cam portion may be located at a side of the inclined surface located at the valve closing side of the second cam portion.
An adjustable valve device of an internal combustion engine that prevents reduction of the rigidity of a camshaft can be provided.
Hereinafter, a description will be given of details of an embodiment with reference to drawings.
The cam unit CU includes a cam base portion 10 that has a diameter larger than that of the camshaft S and is penetrated by the camshaft S, and two cam lobe portions 20 supported by the cam base portion 10. The cam base portion 10 has a substantially cylindrical shape, and has base circular portions 11 each having a semi-cylindrical shape when viewed from the axial direction of the camshaft S (hereinafter, referred to as the axial direction), and nose portions 11n each protruding outward from the base circular portion 11 in the radial direction. The base circular portion 11 and the nose portion 11n correspond to the outer peripheral surface of the cam base portion 10. The cam base portion 10 includes a cam piece portion 10a, and two cam piece portions 10b and 10c that are coupled so as to sandwich the cam piece portion 10a. The cam piece portions 10a through 10c are coupled by two coupling pins CP each penetrating through the cam piece portions 10a through 10c. The cam piece portions 10a through 10c have the same outer peripheral shape when viewed from the axial direction. That is to say, each of the cam piece portions includes the base circular portion and the nose portion formed therein. The cam piece portions 10a through 10c are aligned in the axial direction.
The cam piece portions 10a and 10b are coupled across a space 12, and the cam lobe portion 20 is arranged in the space 12. In the same manner, the other cam lobe portion 20 is arranged in the space 12 between the cam piece portions 10a and 10c. The two cam lobe portions 20 are aligned at a predetermined interval in the axial direction, and each of them can presses the corresponding one of two rocker arms R to lift the corresponding one of two valves V. The entire thickness of the cam base portion 10 in the axial direction is thicker than the thickness of the cam lobe portion 20 in the axial direction.
As illustrated in
In the recess portion 10H, a part of the support shaft 33 is exposed, and two springs 34s are wound around the exposed part. A first spring 34s is arranged at the cam piece portion 10b side, and a second spring 34s is arranged at the cam piece portion 10c side. A first end of the first spring 34s presses the inner surface of the recess portion 10H, and a second end thereof presses the stopper pin 34P of the cam lobe portion 20 arranged at the cam piece portion 10b side. More specifically, the spring 34s biases the stopper pin 34P so that the stopper pin 34P separates from the recess portion 10H. Accordingly, the cam lobe portion 20 at the cam piece portion 10b side is biased so as to protrude from the cam base portion 10. The same applies to the cam lobe portion 20 at the cam piece portion 10c side. As described above, the spring 34s intervenes between the cam base portion 10 and the cam lobe portion 20, and biases the cam lobe portion 20 toward the high position. The spring 34s is an example of a biasing member.
In the case of the present embodiment, when the cam lobe portion 20 is locked at the high position, the cam lobe portion 20 drives the rocker arm R to lift the valve V. When the lock is released, the valve V is lifted by the cam base portion 10 practically while the cam lobe portion 20 receives a reactive force from the rocker arm R and swings in relation to the cam base portion 10. The details will be described later. The cam base portion 10 is an example of a first cam portion, and the cam lobe portion 20 is an example of a second cam portion. In
The cam lobe portion 20 is substantially U-shaped or substantially L shaped so as to bypass the camshaft S. The support shaft 33 penetrates through a first end of the cam lobe portion 20. In
The outer peripheral surface of the cam lobe portion 20 that makes contact with the roller of the rocker arm R includes an inclined surface 21, a top surface 22, and an inclined surface 23 continuously formed in this order in a direction opposite to the rotation direction of the camshaft S. The inclined surfaces 21 and 23 are examples of first and second inclined surfaces facing each other across the top surface 22, respectively. The inclined surface 21, the top surface 22, and the inclined surface 23 come in contact with the roller of the rocker arm R in this order. When the cam lobe portion 20 is at the high position, the top surface 22 is at a position farthest from the rotational center of the cam unit CU, and the inclined surface 21 and the top surface 22 are located further out than the nose portion 11n of the cam base portion 10, protruding from the outer peripheral surface of the cam base portion 10. The support shaft 33 is located on the leading side of the cam lobe portion 20 relative to the rotational direction of the camshaft S, and is located at the inclined surface 21 side. The support shaft 33 is located at a position located away from the rotational center of the cam base portion 10, that is, the rotational center of the camshaft S. A pin 26P is located on the trailing side of the cam lobe portion 20 relative to the rotational direction of the camshaft S, and is located at the inclined surface 23 side. The details will be described later.
An oil control valve OCV is a flow rate control valve of an electromagnetic drive type, and is controlled by an ECU 5. The ECU 5 is an example of a control unit. Oil reserved in an oil pan is supplied into the passage T by an oil pump P. The oil pump P is a mechanical pump coupled to the crankshaft of the internal combustion engine. The oil control valve OCV can linearly adjust the hydraulic pressure supplied into the passage T by the oil pump P based on a value of electric current applied to the oil control valve OCV. The oil control valve OCV is an example of a hydraulic pressure control valve. The hydraulic pressure control valve may be a valve capable of adjusting the hydraulic pressure supplied into the passage T in a step-by-step manner. The ECU 5 includes a CPU, a ROM, a RAM, and the like, and controls the entire operation of the internal combustion engine. The ROM stores programs for executing the control described later.
The cam piece portion 10b holds a pin 16P, and the cam piece portion 10a holds a pin 17P. The cam lobe portion 20 holds the pin 26P. The pin 26P is an example of a lock member. The pin 17P is an example of a pressing member.
A hole 16 communicating with the space 12 is formed in the cam piece portion 10b of the cam base portion 10. The hole 16 extends in the axial direction, and has a bottom surface. The pin 16P is accommodated in the hole 16. A spring 16S coupled to the pin 16P is arranged between the bottom surface of the hole 16 and the pin 16P. The spring 16S biases the pin 16P toward the cam lobe portion 20. The spring 16S is an example of a lock member biasing member.
The hole 17 facing the hole 16 across the space 12 is formed in the cam piece portion 10a of the cam base portion 10. The pin 17P is accommodated in the hole 17. The hole 17 communicates with the passage T6. When the cam lobe portion 20 is at the high position, the hole 17 is positioned coaxially with the hole 16, and faces the hole 16. The hole 17 extends in the axial direction.
When the cam lobe portion 20 is at the high position, the holes 16, 17, and 26 are aligned in the axial direction, and the pins 16P, 17P, and 26P are aligned in the axial direction. In other words, the swing range of the cam lobe portion 20 is defined by the stopper pin 34P and the elongated hole 14 so that the cam lobe portion 20 is positioned at the aforementioned position at one end of the swing range. The biasing force of the spring 16S inserts the pin 16P commonly into the holes 16 and 26, and inserts the pin 26P commonly into the holes 26 and 17. This allows the cam lobe portion 20 to be locked at the high position by the cam base portion 10.
The description will next be given of the lock of the cam lobe portion 20.
When the camshaft S rotates in the released state, the cam lobe portion 20 receives a reactive force from the rocker arm R, and the cam lobe portion 20 moves against the biasing force of the spring 34s and toward the low position as illustrated in
Although the details will be described later, the cam lobe portion 20 recovers from the low position to the high position while making contact with the rocker arm R in accordance with the rotation of the camshaft S, and separates from the rocker arm R. Thus, the cam lobe portion 20 contacts with and separates from the rocker arm R repeatedly in accordance with the rotation of the camshaft S, and swings between the low position and the high position by the reactive force from the rocker arm R and the biasing force of the spring 34s. As described above, in the released state, while the cam lobe portion 20 swings so as to follow the rocker arm R, the nose portion 11n of the cam base portion 10 presses the rocker arm R to lift the valve V.
When the oil control valve OCV stops supplying oil to the passage T, the pin 16P is commonly inserted into the holes 16 and 26 by the biasing force of the spring 16S, and the pin 26P is commonly inserted into the holes 26 and 17 in the same manner as illustrated in
As illustrated in
For example, in a structure where an elongated hole is formed in a cam lobe portion, and a camshaft penetrates through the elongated hole, it may be considered to employ a thin camshaft to secure the swing range of the cam lobe portion. The thin camshaft may reduce the rigidity. The present embodiment can secure the swing range of the cam lobe portion 20 without employing a thin camshaft, and can prevent the reduction of the rigidity of the camshaft.
In a structure where an elongated hole is formed in a cam lobe portion, and a camshaft penetrates through the elongated hole, it may be considered to employ a cam lobe portion in which the elongated hole is expanded to secure the swing range of the cam lobe portion. When the cam lobe portion has the large elongated hole, the rigidity may be reduced because the thickness decreases and the cross-sectional area in the axial direction becomes insufficient. The present embodiment secures the thickness of the cam lobe portion 20, i.e., the cross-sectional area in the axial direction while securing the swing range of the cam lobe portion 20 because the camshaft S does not penetrate through the cam lobe portion 20, thereby preventing the reduction of the rigidity.
As illustrated in
All the holes 16 and 17 formed in the cam base portion 10 and accommodating the pins 16P and 17P, and the hole 26 formed in the cam lobe portion 20 extend in the axial direction. Thus, the cross-sectional area of the cam base portion 10 in the axial direction can be secured, compared to, for example, a case where a hole extending in a direction intersecting the axial direction is formed, and a pin sliding in the hole is arranged. Accordingly, the reduction of the rigidity of the cam unit CU is prevented.
As illustrated in
Additionally, as described above, the recess portion 10H in which the spring 34s is arranged is located in a portion that makes no contact with the rocker arm R, and thus this portion is effectively used. Since the spring 34s is arranged in a position distant from a portion of the cam base portion 10 contacting with the rocker arm R, the cross-sectional area of the portion of the cam base portion 10 contacting with the rocker arm R in the axial direction is also secured. Accordingly, the reduction of the rigidity of the cam base portion 10 is prevented.
In addition, the lock mechanism of the present embodiment locks the cam lobe portion 20 only at the high position. For example, if a mechanism that locks the cam lobe portion 20 both at the high position and at the low position is provided in the cam base portion 10, the structure of the cam base portion 10 becomes complicated, and the rigidity may be reduced. The present embodiment locks the cam lobe portion 20 only at the high position, and thus simplifies the structure of the cam base portion 10 and prevents the reduction of the rigidity. In addition, the production cost is also reduced because the structure is simplified.
If the swing range of the cam lobe portion 20 is desired to be small when a mechanism that locks the cam lobe portion 20 at the high position and a mechanism that locks the cam lobe portion 20 at the low position are provided in the cam base portion 10, the two lock mechanisms need to be located close to each other. However, to secure the strength of the cam base portion 10 or the like, the two lock mechanism needs to be located away from each other to some extent, and there is a limitation in setting the swing range small. The present embodiment locks the cam lobe portion 20 only at the high position, and thus is not subject to the limitation and can set the swing range small.
A description will next be given of a lift state of the valve V.
As illustrated in
The crank angles are approximately the same when the lift amount returns to zero in both the lift curves HC and LC. This is because the boundary part on the outer peripheral surface between the nose portion 11n of the cam base portion 10 located at the inclined surface 23 side and the base circular portion 11 substantially coincides with the part where the inclined surface 23 of the cam lobe portion 20 intersects the outer peripheral surface of the base circular portion 11 as viewed from the axial direction when the cam lobe portion 20 is either at the high position or at the low position. The inclined surface 21 is an example of a first inclined surface that protrudes from the outer peripheral surface of the first cam portion in the first state. The inclined surface 23 is an example of a second inclined surface that partially coincides with the outer peripheral surface of the first cam portion both in the first and second states as viewed from the axial direction of the camshaft.
In the released state, the inclined surface 21 of the cam lobe portion 20 is first pressed by the rocker arm R, and the cam lobe portion 20 swings from the high position to the low position. Then, while the inclined surface 23 beyond the top surface 22 of the cam lobe portion 20 is pressed by the rocker arm R, the cam lobe portion 20 swings from the low position to the high position while rotating so as to separate from the rocker arm R. At this time, the nose portion 11n of the cam base portion 10 also contacts with the rocker arm R. That is to say, both the cam base portion 10 and the cam lobe portion 20 rotate while contacting with the rocker arm R, and the cam lobe portion 20 swings from the low position to the high position. This is because the inclined surface 23 of the cam lobe portion 20 partially coincides with the outer peripheral surface of the nose portion 11n of the cam base portion 10 as viewed from the axial direction while the cam lobe portion 20 swings between the high position and the low position, as described previously.
Therefore, in the released state, while the cam lobe portion 20 recovers from the low position to the high position, the cam lobe portion 20 swings while contacting with the rocker arm R and receiving the reactive force. Thus, the time for the cam lobe portion 20 to recover from the low position to the high position can be secured, and the speed of the swing of the cam lobe portion 20 during the time for the cam lobe portion 20 to recover from the low position to the high position can be reduced. Accordingly, a hitting sound generated by the contact between the stopper pin 34P and the end portion of the elongated hole 14 at the time when the cam lobe portion 20 recovers to the high position can be reduced. In addition, the impact applied to the stopper pin 34P contacting the end portion of the elongated hole 14 at the time when the cam lobe portion 20 recovers to the high position can be reduced. Accordingly, the stopper pin 34P is not required to be thick beyond necessity to secure its rigidity.
Accordingly, in the released state, the cam lobe portion 20A swings from the low position to the high position while the cam base portion 10A and the cam lobe portion 20A contact with the rocker arm R in accordance with the rotation of the camshaft S. Thus, as with the graph illustrated in
As illustrated in
In addition, each of the cam lobe portions 20B and 20Bx separates from the rocker arm R and recovers to the high position after the swing angle reaches a maximum. Thus, the swing amount of the cam lobe portion 20B when the swing angle recovers from the maximum position to the high position is less than that of the cam lobe portion 20Bx. In addition, the rotation angle of the camshaft S of the cam lobe portion 20B required for the swing angle to recover from the maximum position to the high position is greater than that of the cam lobe portion 20Bx. Thus, the swing angle of the cam lobe portion 20B gently recovers from the maximum position to the high position whereas the swing angle of the cam lobe portion 20Bx rapidly recovers from the maximum position to the high position. Accordingly, the cam lobe portion 20B reduces the hitting sound at the time of recovery to the high position compared to the cam lobe portion 20Bx.
Also in this case, the swing amount of the cam lobe portion 20C is less than that of a cam lobe portion 20Cx. The rotation angle of the camshaft S of the cam lobe portion 20C required for the swing angle to recover from the maximum position to the high position is greater than that of the cam lobe portion 20Cx. Thus, the cam lobe portion 20C gently swings to the high position, whereas the cam lobe portion 20Cx rapidly swings to the high position. Accordingly, the cam lobe portion 20C reduces the hitting sound at the time of recovery to the high position compared to the cam lobe portion 20Cx.
While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments and various variations may be made without departing from the scope of the present invention.
In the present embodiment, the cam base portion 10 is composed of the cam piece portions 10a through 10c, but the cam piece portions 10a through 10c may be integrally formed. For example, a slit capable of accommodating the cam lobe portion may be formed in a single cam base portion. Moreover, in the present embodiment, the cam base portion 10 is formed separately from the camshaft S, but may be integrally formed. A hole penetrated by the camshaft S may not be formed in the cam base portion 10, and a shaft member may be coupled to both end portions of the cam base portion 10 in the axial direction to use the shaft member as a camshaft.
In the present embodiment, two cam lobe portions 20 are swingably supported in relation to the cam base portion 10, but at least one of the cam lobe portions 20 is required to be swingable. Alternatively, a swingable single cam lobe portion may be coupled to the cam base portion, and one of two rocker arms may be driven by the cam base portion and the cam lobe portion, and the other rocker arm may be driven by a normal cam.
In the cam unit CU of
When the internal combustion engine equipped with the adjustable valve device 1 of the present embodiment operates at the minimum rotation speed, the cam lobe portion 20 is required to recover from the low position to the high position while contacting with the rocker arm R in the released state and receiving the reactive force from the rocker arm R.
In the cam unit CUB of
The cam lobe portion 20 is swingably supported by the support shaft 33 that penetrates through the cam lobe portion 20 and the cam base portion 10, but this structure does not intend to suggest any limitation. For example, the cam lobe portion 20 may be swingably coupled around a shaft portion integrally formed in the cam base portion 10. Alternatively, a shaft portion may be integrally formed in the cam lobe portion 20, and a recess portion that rotatably accommodates the shaft portion may be formed in the cam base portion 10.
The first end of the spring 34s may be fixed to the cam base portion 10, and the second end may be fixed to the cam lobe portion 20.
1 variable valve device
5 ECU
S camshaft
R rocker arm
V valve
OCV oil control valve
10 cam base portion (first cam portion)
11 base circular portion
11
n nose portion
12 space
16S spring (lock member biasing member)
17 hole (first engagement hole)
17P pin (pressing member)
20 cam lobe portion (second cam portion)
21 inclined surface (first inclined surface)
22 top surface
23 inclined surface (second inclined surface)
26 hole (second engagement hole)
26P pin (lock member)
27 engagement recess portion (engagement portion)
33 support shaft
34
s spring (biasing member)
T, T6 passage
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-009802 | Jan 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/051697 | 1/22/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/111661 | 7/30/2015 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6427653 | Hara et al. | Aug 2002 | B1 |
| 7069889 | Lechner et al. | Jul 2006 | B2 |
| 9745875 | Yano | Aug 2017 | B2 |
| 20060011161 | Lechner et al. | Jan 2006 | A1 |
| 20150184560 | Yano et al. | Jul 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 10038916 | Feb 2002 | DE |
| 2427897 | Jan 2007 | GB |
| S60-8402 | Jan 1985 | JP |
| S62-195608 | Dec 1987 | JP |
| 2001-329819 | Nov 2001 | JP |
| 2006-526727 | Nov 2006 | JP |
| 2004109068 | Dec 2004 | WO |
| Entry |
|---|
| English translation of the Written Opinion of the International Searching Authority dated Oct. 23, 2012, in International Application No. PCT/JP2012/071186. |
| US Patent and Trademark Office, Notice of Allowability in U.S. Appl. No. 14/422,501, dated Apr. 18, 2017, 1 page. |
| US Patent and Trademark Office, Office Action in U.S. Appl. No. 14/422,501, dated Nov. 16, 2016 2 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20160319705 A1 | Nov 2016 | US |
