The present invention relates to a variable valve mechanism that drives valves of an internal combustion engine and changes a drive state of the valves in accordance with an operating condition of the internal combustion engine.
As shown in
The variable valve mechanism, described in Patent Documents 1 to 4, can merely change a lift curve C such that a ratio dL/dθ of a maximum lift amount variation dL to an operation angle variation dθ is substantially constant, and thus the lift curve C is changed with its substantially similar shape, as shown in
However, such control will be required to further improve performance of the internal combustion engine. An object of the present invention is thus to provide a variable valve mechanism that can freely change the maximum lift amount and the operation angle.
To achieve the above-described object, a variable valve mechanism of the present invention is configured as below. That is, the variable valve mechanism includes: a cam that rotates with rotation of the internal combustion engine; a transmission mechanism that transmits a profile of the cam to a valve to drive the valve; a first variable device that controls the transmission mechanism to continuously change at least a maximum lift amount of a lift curve indicating a lift amount of the valve that corresponds to a rotation angle of the internal combustion engine; and a second variable device that controls the transmission mechanism to continuously change at least an operation angle of the lift curve. Furthermore, the variable valve mechanism satisfies any one of the following requirements 1) to 3).
1) When the lift curve lies in any condition within a predetermined range that covers all or part of a variable range of the lift curve, an absolute value of a ratio (dL/dθ) of a maximum lift amount variation to an operation angle variation for a slight change from the condition caused by the first variable device is larger than that for a slight change from the condition caused by the second variable device.
More preferably, the absolute value of the ratio (dL/dθ) for the slight change caused by the first variable device is equal to or larger than ten times that for the slight change caused by the second variable device. Most preferably, the absolute value of the ratio (dL/dθ) for the slight change caused by the first variable device is substantially ∞ mm/degree, and the absolute value of the ratio (dL/dθ) for the slight change caused by the second variable device is substantially 0 mm/degree.
The predetermined range is not limited to a particular range, and the maximum lift amount and the operation angle may be in any numerical range. Preferably, the predetermined range covers all or most part of the variable range. It is also preferable that the predetermined range include a point at which the product of the maximum lift amount and the operation angle is maximum. Most preferably, in the case where the maximum lift amount and the operation angle both cannot be changed into zero, the predetermined range covers all the variable range; in the case where the maximum lift amount or the operation angle can be changed into zero, the predetermined range covers all the variable range except for a point of zero and a vicinity of the point.
2) The variable width (ΔL) of the maximum lift amount for the first variable device is larger than that for the second variable device, and the variable width (Δθ) of the operation angle for the first variable device is smaller than that for the second variable device.
More preferably, the variable width of the maximum lift amount for the first variable device is equal to or larger than ten times that for the second variable device, and the variable width of the operation angle for the first variable device is equal to or smaller than one-tenth that for the second variable device. Most preferably, the variable width of the operation angle for the first variable device is substantially zero, and the variable width of the maximum lift amount for the second variable device is substantially zero.
3) An absolute value of a ratio (ΔL/Δθ) of the variable width of the maximum lift amount to the variable width of the operation angle for the first variable device is larger than that for the second variable device.
More preferably, the absolute value of the ratio (ΔL/Δθ) for the first variable device is equal to or larger than ten times that for the second variable device. Most preferably, the absolute value of the ratio (ΔL/Δθ) for the first variable device is substantially ∞ mm/degree, and the absolute value of the ratio (ΔL/Δθ) for the second variable device is substantially 0 mm/degree.
According to the present invention, the maximum lift amount and the operation angle can be freely changed by changing the lift curve by using the first variable device and the second variable device. Accordingly, the maximum lift amount can be increased with the decrease in the operation angle, and can be decreased with the increase in the operation angle.
The specific configuration of the variable valve mechanism of the present invention is not limited to a particular configuration. For example, the configuration of the variable valve mechanism may include, between any one of variable valve mechanisms of Patent Documents 1 to 4 (JP 3799944, JP 4143012, JP 4771874, and JP 2007-077940 A) and a valve, a part provided between a cam of another one of the above variable valve mechanisms and a valve. However, the variable valve mechanism of the present invention is preferably configured as below so as to have a shorter valve system (transmission mechanism).
The transmission mechanism has four links coupled to one another via joints. A first variable device is configured to shift at least a reciprocating motion direction of a predetermined joint when the valve is driven. A second variable device is configured to shift at least a position of the predetermined joint during a base-circle time in which a base circle of a cam acts.
A specific aspect of the first variable device is not limited to a particular aspect, but an example thereof is as follows. That is, the first variable device includes a first control shaft provided so as to be rotatably controlled, a rotary lever that extends from the first control shaft in a radial direction of the first control shaft and rotates with the first control shaft, and a guide member rotatably attached to the leading end of the rotary lever so as to guide the reciprocating motion direction of the predetermined joint. Preferably, two of the four links are swingably supported on the first control shaft. This is because the first control shaft can also serve as a support shaft of the two links and thus the number of parts of the variable valve mechanism can be reduced to allow making the variable valve mechanism compact.
A specific aspect of the second variable device is not limited to a particular aspect, but an example thereof is as follows. That is, the second variable device includes a second control shaft provided so as to be rotatably controlled, and a control cam provided on the second control shaft so as to protrude therefrom. The control cam pushes the predetermined joint with the rotation of the second control shaft to shift the position of the predetermined joint during the base-circle time.
The cam may be a commonly used cam having only a main nose, but preferably may be structured as below for more effectively implementing the present invention. That is, the cam may include the main nose and a sub-nose. The sub-nose opens and closes the valve again after the main nose opens and closes the valve. The opening and closing of the valve by the sub-nose can be disabled by changing the lift curve by using the first variable device or the second variable device. In such an aspect, the maximum lift amount refers to a maximum lift amount caused by the main nose and the operation angle refers to an operation angle caused by the main nose.
Now, embodiments of the present invention will be described. Note that the present invention is not limited to those embodiments, and can be implemented by freely changing the structure or the form of each part of those embodiments without departing from the spirit of the present invention.
A variable valve mechanism 1 of Embodiment 1 shown in
[Cam 10]
As shown in
The sub-nose 13 is a nose used to open the valve 6 twice (that is, open and close the valve 6 again after the main nose 12 opens and closes the valve 6) for the purpose of exhaust gas recirculation (EGR) or the like. As shown in
[Transmission Mechanism 20]
The transmission mechanism 20 is a mechanism that transmits the profile of the cam 10 to the valve 6 so as to drive the valve 6. As shown in
The first link 21 is rotatably supported, at an end portion of the first link 21 remote from the second link 22, by a first control shaft 51 of the first variable device 50 so as to swing. The first joint 31 that serves as a joint between the first link 21 and the second link 22 is provided with a roller-like cam follower 36, which contacts the cam 10 and can rotate. When the cam follower 36 is pushed by the cam 10, the first link 21 swings about the first control shaft 51.
The second and the third links 22, 23 are links that transmit the swinging force of the first link 21 to the fourth link 24. The second joint 32 that serves as a joint between the second link 22 and the third link 23 is provided with a roller-like rotatable slider 37.
The fourth link 24 is rotatably supported, at an end portion of the fourth link 24 remote from the third link 23, by the first control shaft 51 so as to swing. The fourth link 24 is provided, in its bottom surface, with a driving surface 24a that drives the valve 6 via the rocker arm 41 when swinging.
The rocker arm 41 is swingably supported at its base end by a lash adjuster 48, and is provided with a roller 42 at a middle portion of the rocker arm 41 in the longitudinal direction thereof. The roller 42 contacts the driving surface 24a of the fourth link 24 and can rotate. When swinging, the rocker arm 41 drives the valve 6 at the leading end of the rocker arm 41.
The four links 21 to 24 (four-joint linkage) are provided with return springs (not shown) used to bias the links 21 to 24 toward a return direction that is opposite to a lift direction (in which the valve 6 is lifted).
[First Variable Device 50]
The first variable device 50 is a device that mainly changes the maximum lift amount L of a lift curve C. The lift curve C indicates a lift amount of the valve 6 corresponding to a rotation angle of the internal combustion engine. Note that the first variable device 50 does not change the maximum lift amount L to zero. As shown in
Accordingly, in the first variable device 50, a variable width Δθ of the operation angle θ is substantially zero. Therefore, an absolute value of a ratio ΔL/Δθ of a variable width ΔL of the maximum lift amount L to the variable width Δθ of the operation angle θ is substantially ∞ mm/degree. Furthermore, in any condition where the lift curve C lies within its variable range, for a slight change caused by the first variable device 50, an absolute value of a ratio dL/dθ of a maximum lift amount variation dL to an operation angle variation dθ is substantially ∞ mm/degree.
The first variable device 50 is configured as below. That is, as shown in
As shown in
As shown in
[Second Variable Device 60]
The second variable device 60 is a device that mainly changes the operation angle θ of the lift curve C. Note that the second variable device 60 does not change the operation angle θ to zero. As shown in
Accordingly, in the second variable device 60, the variable width ΔL of the maximum lift amount L is substantially zero. Therefore, an absolute value of a ratio ΔL/Δθ of the variable width ΔL of the maximum lift amount L to the variable width Δθ of the operation angle θ is substantially 0 mm/degree. Furthermore, in any condition where the lift curve C lies within its variable range, for a slight change caused by the second variable device 60, an absolute value of a ratio dL/dθ of the maximum lift amount variation dL to the operation angle variation dθ is substantially 0 mm/degree.
The second variable device 60 is configured as below. That is, as shown in
As shown in
As shown in
[Effect]
According to Embodiment 1, the following effects can be produced. That is, since the maximum lift amount L can be continuously changed without changing the operation angle θ by the first variable device 50, and since the operation angle θ can be continuously changed without changing the maximum lift amount L by the second variable device 60, the maximum lift amount L and the operation angle θ can be freely changed.
Moreover, since the operation angles θ and θs can be decreased by the second variable device 60 to disable the opening and closing of the valve 6 performed by the sub-nose 13, and since the maximum lift amount L caused by the main nose 12 can be increased by the first variable device 50, the valve 6 can be opened one time instead of two times, with a necessary valve-driving amount kept by the main nose 12.
Embodiment 2 shown in
To be specific, the variable width ΔL of the maximum lift amount L for the first variable device is larger than that for the second variable device; the variable width Δθ of the operation angle θ for the first variable device is smaller than that for the second variable device. Accordingly, the absolute value of the ratio ΔL/Δθ of the variable width ΔL of the maximum lift amount L to the variable width Δθ of the operation angle θ for the first variable device is larger than that for the second variable device. Furthermore, in any condition where the lift curve C lies within its variable range, an absolute value of the ratio dL/dθ of the maximum lift amount variation dL to the operation angle variation dθ for a slight change from the above any condition caused by the first variable device is larger than that for a slight change from the condition caused by the second variable device.
Embodiment 2 as well, the maximum lift amount L and the operation angle θ can be freely changed by controlling the maximum lift amount L and the operation angle θ by using the first variable device and the second variable device.
Number | Date | Country | Kind |
---|---|---|---|
2016-015158 | Jan 2016 | JP | national |
Number | Date | Country |
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2 025 905 | Feb 2009 | EP |
2 569 226 | Feb 1986 | FR |
2006-046111 | Feb 2006 | JP |
3799944 | Jul 2006 | JP |
2007-077940 | Mar 2007 | JP |
4143012 | Sep 2008 | JP |
4771874 | Sep 2011 | JP |
Entry |
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Extended European Search Report dated Sep. 27, 2017 in European Application No. 16197491.0. |
Number | Date | Country | |
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20170218795 A1 | Aug 2017 | US |