JP2014218905A - High-speed cam mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a cam mechanism for improving more performance over a prior patent application of "Cam mechanism with steep rise" (Japanese Patent Application No.2013-28576) as a cam mechanism that can be used in "Ignition mechanism of Internal Combustion Engine" (Japanese Patent Application No.2012-276596) filed by the present inventor.SOLUTION: If a rotational speed of a cam is increased in respect to the same cam lift, its rotational angle is increased, resulting in that a pressure angle can be relatively set to a low value. Under application of a method in which a high speed cam rotating at integral multiplication of a basic cam is used to decrease the pressure angle and further it is combined with a symmetrical cam described in "Cam mechanism with steep rise", the high speed cam mechanism enables a steeper rise.

Description

The present invention relates to a high-speed cam mechanism capable of steep rising.

The present inventor has researched a cam mechanism having a steep rise and has applied for a patent based on the result (Japanese Patent Application No. 2013-28576). However, depending on the situation, a case where a steep rise is required may occur. Can be considered. The present invention has been developed in consideration of dealing with such a case. Although the term “rise” is used here, the terms “rise” and “rise” are not necessarily limited to the upward direction so that the term “cam lift” is used even when the valve is pushed down by the engine overhead cam. Note that it may be pushed down rather than down.

This cam mechanism uses a cam that rotates at an integral multiple of a cam that rotates at a specific speed. For this reason, although it is not applicable to an arbitrary cam curve and is accompanied by some limiting conditions, these conditions are not so severe and can be used without any problem for the ignition mechanism of the HCCI engine.
A cam that rotates at a high speed at an integer multiple is called a high-speed cam or a high-speed basic cam. A high-speed symmetrical cam is a symmetrical (inverted shape) cam with respect to the high-speed basic cam. Further, the high-speed basic cam and the high-speed symmetric cam may be simply referred to as a high-speed cam without being distinguished from each other.

This limited condition means that the cam follower rises twice and 3 degrees depending on the speed multiple of the high-speed cam during one rotation of the basic cam, so that the influence of this can be prevented from becoming a problem. Whether or not. Depending on the shape of the cam curve, there are cases where it is very difficult to take measures against this. On the other hand, depending on use conditions, this condition may not be a problem. In the ignition mechanism of the HCCI engine, when the rotational speed is twice, the latter can be used without any problem, but the details will be described later. It is considered that there are many cases other than the ignition mechanism of the engine, and this cam mechanism can be widely used for cases where a solution can be applied and cases where there is no problem.

Japanese Patent Application No. 2012-276596 Japanese Patent Application 2013-28576

As a cam mechanism that can be used for the "ignition mechanism of an internal combustion engine" (Japanese Patent Application No. 2012-276596) filed by the present inventor, a "cam mechanism having a steep rise" (Japanese Patent Application No. 2013-28576) has been filed. The task was to develop a product with further improved performance.

If the pressure angle of the cam increases, the normal force increases with the same load and causes cam wear and deflection. Therefore, the pressure angle of the direct acting cam follower is preferably 30 degrees or less. In order to improve this problem as much as possible, the present invention has previously filed a patent application of “Cam Mechanism with Steep Rise” (Japanese Patent Application No. 2013-28576). In this case, the cam follower is pushed up as if it is squeezed between the basic cam and the symmetrical cam, and the side pressure is canceled so that no excessive force is applied to the cam follower even for a large pressure angle. is there. However, since the pressure angle itself is the same as the conventional mechanism, its effect is limited.

It should be noted that the term symmetric cam is generally used when the cam itself has a symmetric shape, but here the term symmetric cam or basic symmetric cam is the above-mentioned unless otherwise specified. Similar to the meaning used in the “cam mechanism with a steep rise” (Japanese Patent Application No. 2013-28576), it is used to mean a cam symmetrical to the basic cam, in other words, a cam with the basic cam turned upside down. I want. The term "basic rotational speed" (basic speed) is a rotational speed that is considered to be 4 revolutions of the engine (intake stroke, compression stroke, combustion stroke, exhaust stroke) based on the rotational speed of the engine, and is fixed. It is not a thing. When the engine is rotating at 3000 rpm, 1500 rpm is the basic rotation speed, and when the engine is rotating at 2000 rpm, the basic rotation speed is 1000 rpm. Regarding the rotation angle of the basic cam, here, the four strokes are considered as one rotation, and this is described as 360 degrees.

In the present invention, the problem of the pressure angle is improved, and the pressure angle itself when the cam and the cam follower come into contact with each other is reduced.
As a method of reducing the pressure angle, the application of the fact that if the cam rotation speed is increased, the rotation angle becomes larger with respect to the same cam lift, and the pressure angle can be made relatively smaller. It is intended to be used as a means for solving the problem. The relationship between the basic cam and the high speed cam will be specifically described below.

Now, a cam having a cam curve as shown in FIG. Assume the main part of the cam and the cam curve. The main part of the cam is a part rising from 160 degrees to 180 degrees, and is a part that needs to correspond faithfully to the high-speed cam.
FIG. 2B shows a cam curve in which only the angle is doubled without changing the displacement. This is a cam curve of a cam that rotates at twice the speed of the basic cam. The basic cam shown in FIG. 2A has a 90-degree position at a high-speed cam shown in FIG. 2B, and the basic cam has a 180-degree position at a 360-degree high speed cam. The cam corresponds to a position at an angle twice that of the basic cam. However, the first part is slightly different from the basic cam. The reason is that there is no problem because the main part (rising part) between 160 degrees and 180 degrees of the basic cam is doubled by the angle in the high-speed cam and comes to the position of 320 degrees to 360 degrees. The falling portion between 180 degrees and 220 degrees comes to a position of 360 degrees to 440 degrees with the high-speed cam. This portion exceeding 360 degrees corresponds to the beginning of the second rotation of the high-speed cam, and is provided at a position of 0 degrees to 80 degrees obtained by subtracting 360 degrees from this value.

The high-speed cam is such that the displacement of the basic cam with respect to the angle within the range including the main portion becomes equal to the displacement at an angle obtained by multiplying the angle within the range by a multiple of the rotational speed. If the angle obtained by multiplying the angle within this range by an integer exceeds the range of 0 degrees to 360 degrees, the angle obtained by multiplying the angle by 360 degrees is set so that the angle falls within the range of 0 degrees to 360 degrees. An angle obtained by subtracting an integer multiple is used.
When combining a high-speed cam and a basic cam, it is set so that the starting points of the main parts of both are aligned. In this way, this high-speed cam is considered to be a part mainly composed of the rising part, and this is reflected faithfully. However, the trailing edge does not necessarily correspond to twice the angle of the basic cam. There is no problem even if it is slightly deviated as long as it does not prevent the falling of the basic cam when used together with the basic cam.
Even in the case of a high-speed cam that rotates at an integral multiple of the basic cam, such as triple speed or quadruple speed, the same concept can be used in which the displacement of the rising portion is aligned and the angle is triple or quadruple.

When a high-speed cam with such a cam curve is rotated at twice the speed of the basic cam, the rotation angle is twice that of the same displacement, so the pressure angle is approximately half that of the basic cam and the pressure angle Restrictions can be relaxed. However, even if the pressure angle is reduced, the speed and acceleration acting on the cam follower are the same as in the case of the basic cam.
However this method is part of the movement corresponding to half the basic cam if double speed, be used in any case for only be realized movement thirds portion corresponding to one of the long if the basic cam 3 speed This is not possible and can be used only when the condition that there is no problem even if the movement of the other part is omitted, or when the movement of this part can be supplemented by the basic cam.

Since the pressure angle can be made relatively small by increasing the rotational speed of the cam in this way, it has become possible to realize a high-speed cam mechanism with a steep rise that could not be realized by the conventional methods.
Although this method has a great effect even when a high-speed cam is used alone, this method is combined with a basic cam and a symmetric cam described in “Cam Mechanism with Steep Rise” (Japanese Patent Application No. 2013-28576). It becomes possible to make it more effective by using together. In other words, a cam that rotates in the forward direction with an integer multiple of the rotational speed is considered as a basic high-speed cam. This high-speed basic cam and a symmetrical cam are used as a high-speed symmetrical cam. The basic cam and the symmetrical cam in the “steep cam mechanism” (Japanese Patent Application No. 2013-28576) are considered. Various methods can be considered for this application method. One example is shown in [Embodiment 1].

Further, basically, the same idea is intended to reduce the pressure angle with a high-speed cam, but there is a method in which a cam that rotates at a high speed and a cam that rotates at a basic speed are combined. An example of this configuration is shown in [Embodiment 2]. The case where the rotational speed of the high-speed cam is increased to three times or more is shown in [Embodiment 3].

The application of the cam mechanism is not limited to the PCCI ignition stroke, but can be widely used when a steep rise or fall is required, although there are some restrictions.
Although not described here, the optimal ignition timing of HCCI varies depending on the engine speed and other conditions, and the cam curve angle shown here is not necessarily optimal. For this reason, when applied to an actual machine, it is ideal if a mechanism capable of finely adjusting the phase difference can be provided between the crankshaft of the engine and the camshaft of the cam mechanism.

It is a schematic diagram which shows an example of a high-speed cam mechanism. The figure which shows the relationship between a basic cam curve, a high-speed cam curve, a stroke, and a cam curve. The figure which shows the relationship between another basic cam curve, a high-speed cam curve, a stroke, and a cam curve. The figure which shows the relationship between a basic cam curve, a 3 times high-speed cam curve, and a stroke and a cam curve.

In the following, a case where the present invention is used for ignition of HCCI will be described as an embodiment of the high-speed cam mechanism, and its structure and operation will be described with reference to the drawings and reference numerals attached thereto. It should be noted that the cam curve exemplified here does not indicate the optimum condition, and changes depending on the progress or delay of the ignition timing.

[Embodiment 1]
FIG. 1 is a schematic diagram showing the structure. However, it should be noted that the shape of the cam does not accurately represent a contour curve based on the cam curve described later.
As shown in this figure, the high-speed basic cam 131 and the symmetrical high-speed symmetric cam 132 are placed on the same straight line so that the center lines of the rotation axes of the cam shaft 133 of the high-speed basic cam and the cam shaft 134 of the high-speed symmetric cam are on the same straight line. Are arranged so as to face each other and rotate in opposite directions at a speed twice the basic rotation speed. The cam follower 135 is a roller cam follower having three divided rollers 136.

2A is a cam curve of a cam that rotates at a basic speed as described in [Means for Solving the Problems], and FIG. 2B is a high speed that rotates at twice the basic speed. The cam curve of a basic cam is shown.
This is the basis of the high-speed basic cam 131 and the high-speed symmetric cam 132 used in the cam mechanism shown in FIG. 1. The high-speed basic cam 131 is made based on this cam curve, and the high-speed symmetric cam 132 is the high-speed symmetric cam 132. It is symmetrical with the basic cam 131 (the high-speed basic cam is turned over). Note that the method for obtaining the contour curve of the cam from the cam curve is the same as that of a normal cam mechanism and will not be described.

As described above, in the high-speed basic cam 131 of the double speed, only the 0 to 180 degree portion of the cam rotating at the basic speed can be cammed, so that the cam rotating at the basic speed is between 180 and 270 degrees. The down part must be provided in the first part.
FIG. 2C shows each stroke of the engine and the displacement of the high-speed cam. In this configuration, the basic cam is not used, but the displacement is also shown for reference.

Here, since the cam follower holding mechanism by the basic cam is not provided, the cam follower 135 is lowered as it is by the first falling of the high-speed basic cam 131. This movement is a movement that is not found in the basic cam, but as shown in FIG. 2 (C), this part is the intake stroke, and the return of the ignition piston during the intake stroke is not particularly problematic in the stroke, so it is used as it is. I can do it.

When the rotation of the high speed basic cam 131 reaches 180 degrees, the suction stroke ends, and then the compression stroke starts. Near the end of this compression stroke, compression by the high-speed basic cam 131 is performed, and the air-fuel mixture is compression-ignited. The high-speed basic cam 131 enters the second rotation, the high-speed basic cam 131 falls during the combustion stroke, and rises rapidly in the exhaust stroke in the same manner as the compression stroke. After completing the four strokes of suction, compression, combustion, and exhaust, the initial state is reached. Will return. In the exhaust stroke, not only is a rapid rise not necessary, but pressure loss increases, which is not desirable, but the volume of the secondary cylinder used for HCCI ignition is small, so there is no significant loss and the relationship with the compression stroke It is unavoidable.
By using the high-speed basic cam 131 and the high-speed symmetric cam 132 that rotate at twice the speed of the basic cam in this way, the above-mentioned [Patent Document 2] ("Cam mechanism with a sharp rise" (Japanese Patent Application No. 2013-2003)). 28576)), it is possible to configure a cam mechanism that moves more steeply.
In the drawings in this application document, only the high-speed basic cam and the high-speed symmetric cam rotating shaft are shown as being coaxial, but it is also possible to use a parallel-shaft system as exemplified in [Patent Document 2]. is there.

[Embodiment 2]
As described above, when the HCCI is used for ignition at twice the rotational speed, there is no problem even if the first rotation is performed twice, that is, the compression stroke is performed in the second rotation and the exhaust stroke is performed in the second rotation. If you don't want to rotate, you can avoid this by holding the cam follower with the basic cam. The method will be described below.

FIG. 3A shows a cam curve of a basic cam that rotates at the basic rotation speed in this case. Unlike [Embodiment 1], in this case, the motor slowly falls at the beginning of rotation, rapidly rises in the middle, and then is held in that position (the ignition piston is pushed in). ing. The air-fuel mixture is compressed and ignited by this rapid rise.
FIG. 3B shows a cam curve of a high-speed basic cam that rotates at twice the speed of this basic cam.
As is clear from comparison with the cam curve of the basic cam, the holding portion of the latter half of the basic cam after 180 degrees is cut. As described above, the high-speed cam is designed mainly for the rising portion. The high-speed symmetric cam has a shape in which the high-speed basic cam made based on this cam curve is turned upside down.

There are two methods for holding the cam follower in the raised position. As a first method, a high-speed cam mechanism combining the above-described high-speed basic cam and a high-speed symmetric cam and a cam mechanism using a basic cam having the cam curve shown in FIG. This is a method in which the basic cam holds the state. Although this method is reliable in operation, a cam mechanism using a basic cam (this cam mechanism is preferably a combination of a basic cam and a symmetric cam, but a symmetric cam may not be used), and a high-speed basic cam and a high-speed symmetric It is necessary to combine two types of cam mechanisms, that is, a high-speed cam mechanism using a cam, and there is a disagreement that the structure is complicated. On the other hand, the method described below has an advantage that the structure becomes simple. The method will be described below.

Its basic structure is the same as that shown in FIG. However, in FIG. 1, the high-speed basic cam and the high-speed symmetric cam are combined, but in this case, the basic cam having the cam curve shown in FIG. As a cam corresponding to the high-speed symmetrical cam 132 used in combination with this, a high-speed basic cam having the cam curve shown in FIG. The basic cam is rotated at the basic speed, and the high-speed symmetric cam is rotated in the reverse direction at a high speed (twice the speed of the basic cam).
FIG. 3C shows the engine strokes and the movements of the basic cam and the high-speed cam in comparison. Although the two cams rotate at different speeds, the cam lifts are aligned at the same height during the suction / compression stroke, and the roller of the cam follower does not come off the cam. As shown in FIG. 3C, it is important that the basic cam and the high-speed symmetric cam are set so that both of them rise when they rise in the compression stroke. When the high-speed symmetrical cam rises for the second time, the cam follower is held at the raised position by the basic cam, and the cam follower does not operate.

Even if the relationship between the basic cam and the symmetrical cam is reversed from the above method and the high-speed basic cam is rotated at a high speed and the symmetrical cam is rotated in the reverse direction at the basic speed, the same result can be obtained. Is also possible.

[Embodiment 3]
In the above two examples, the rotational speed of the high-speed cam is twice that of the basic cam, but the speed can be further increased.
In the first [Embodiment 1], since the speed was doubled, there was no problem if the extra rising occurred only once in the exhaust stroke. However, the extra rising occurred twice at the triple speed, meaning that unnecessary movement is suppressed. Therefore, it is desirable to hold the basic cam.

When the speed is tripled, the operating range of the high-speed cam is one third of the basic cam and 120 degrees in terms of angle. An attempt to align the end point of the rise with the end point of the compression stroke is a narrow range from 60 degrees to 180 degrees. The rise and fall must fall within this range.
Furthermore, if it is attempted to end the falling stroke in the suction stroke so as not to be applied to the compression stroke, the range is limited to 90 degrees. The start point of the fall can be set in the range of 60 degrees to 90 degrees, but it becomes 60 degrees when trying to be as gentle as possible.
The falling is determined in the range of 60 to 90 degrees under the above conditions. FIG. 4A is a cam curve of a basic cam for triple speed, which is made so as to satisfy such a limiting condition.

Based on this, the cam curve of the high-speed cam is created. In the case of double speed, the range of 0 to 180 degrees of the basic cam is doubled, but in the case of triple speed, the cam curve changes slightly.
First, pay attention to the rising end point (180 degrees) of the cam curve so that the main cam part is always included, and set the same position (180 degrees) for the high-speed cam. When this position is determined, the range that can be accommodated in the high-speed cam is the range from 60 degrees to 180 degrees of the basic cam. The position of 60 degrees of the basic cam is 0 degrees of the high-speed cam and the position of 180 degrees of the basic cam is high-speed. Corresponds to the 360 degree position of the cam.
Next, let us consider the basic cam rising section (for 20 degrees from 160 degrees to 180 degrees). If the range from 160 degrees to 180 degrees is tripled, it becomes 480 degrees to 540 degrees, but if it exceeds 360 degrees, it is considered as the next rotation and subtracting 360 degrees from each will be 120 degrees to 180 degrees. This is the rising part of the high-speed cam. Although it may be possible to exceed 720 degrees at 4 times speed and 5 times speed, in such a case, an integer multiple of 360 degrees is subtracted so that the result falls within the range of 0 degrees to 360 degrees.
The falling portion in the range of 60 degrees to 90 degrees in FIG. 4A becomes a range of 180 degrees to 270 degrees when tripled. The result created in this way is shown in FIG.

The high-speed symmetrical cam has a shape in which the high-speed basic cam having the cam curve shown in FIG. Combining the basic cam and the high-speed symmetric cam produced based on these cam curves, the cam mechanism is configured so that the basic cam and the high-speed symmetric cam rise together in the same way as [Embodiment 2]. A high-speed cam mechanism of 3 times speed can be configured by reversely rotating at 3 times the speed of the cam.

FIG. 4 (C) shows each stroke of the engine in comparison with the movements of the basic cam and the high-speed cam, and the triple speed movement will be described using this.
In the case of triple speed, the first rising of the high-speed cam exists when the basic cam corresponding to the suction stroke is 40 degrees to 60 degrees. However, here, the cam follower is held in a raised position by the basic cam and does not move. After that, the cam follower descends because both the basic cam and the high-speed symmetric cam fall. When the basic cam is 160 degrees, both the basic cam and the high-speed symmetrical cam rise rapidly and the cam follower rises. The basic cam is highest at 180 degrees. The high-speed symmetric cam falls, but the basic cam holds the cam follower in that position. The high-speed symmetric cam then rises for the third time, but the cam follower does not move while being held by the basic cam. When the basic cam makes one revolution, the cycle ends and the next cycle starts.
Here, as in [Embodiment 2], the same effect can be obtained when the relationship between the basic cam and the high-speed symmetric cam is reversed from that of the above method and the high-speed basic cam and the symmetric cam.

If conditions such as durability against high-speed rotation can be cleared, it is possible to achieve higher speeds such as 4 × speed, 5 × speed, and the like based on the same concept. However, in that case, if considered for HCCI ignition, it stands between the rotation angle of 1/4 of 360 degrees at 90 ° and the rotation angle of 72 times of 1/5 of 360 degrees at 5 times speed. It is necessary to complete the falling and rising. These are 90 degrees or less corresponding to one stroke angle of the engine, and the rising and falling must be performed during the compression stroke.
In normal HCCI ignition, it is not necessary to increase the speed so far, but it is worth considering if there is a necessity to increase the speed.
If a groove cam is used, pressure can be applied at the time of falling, but in the case of a groove cam, it is necessary to cut grooves on both sides of the high-speed basic cam in the center of FIG. Therefore, it is necessary to devise a structure for the cam follower.

131 High Speed Basic Cam 132 High Speed Symmetric Cam 133 High Speed Basic Cam Cam Shaft 134 High Speed Symmetric Cam Cam Shaft 135 Cam Follower 136 Roller

Claims (1)

The basic cam is a basic cam, and the displacement with respect to the angle within the range including the main part of the cam curve of the basic cam is an angle obtained by multiplying the angle within the range by an integer or this angle is 0 to 360 degrees. Based on a cam curve that is equal to the displacement for an angle obtained by subtracting an integral multiple of 360 degrees from an angle that is an integral multiple of the angle so that the angle falls within the range of 0 to 360 degrees if the range is exceeded. At least one of a high-speed basic cam that rotates at a rotational speed that is an integral multiple of the basic cam that is made, or a high-speed symmetrical cam that rotates reversely at a rotational speed that is an integral multiple of the high-speed basic cam A cam mechanism comprising:

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