WO2005088102A1

WO2005088102A1 - Track determining method for cam of cam-type engine and hump track part, and cam whose track is determined by said method and cam-type engine having hump track part

Info

Publication number: WO2005088102A1
Application number: PCT/KR2005/000262
Authority: WO
Inventors: Yong Suk Kim
Original assignee: Mission Foundation Of The Family Federation For World Peace And Unification
Priority date: 2004-03-17
Filing date: 2005-01-28
Publication date: 2005-09-22
Also published as: KR100600581B1; KR20050092830A

Abstract

A track determining method for a cam and a hump track part of a cam-type engine, the cam-type engine on where a roller rolls along a cam track surface (CT) having a plurality of crests and valleys, are provided by using a radius (R1) of a circumscribed circle externally contacting a crest of the cam track surface, a radius (R2) of an inscribed circle internally contacting a valley of the cam track surface, a radius (Ra) of a crest circle internally contacting the circumscribed circle, a radius (Rb) of a valley circle externally contacting the crest circle and the inscribed circle, a radius (R) of the main circle of which is the same as the radius of the main roller rolling along the cam track surface, and a radius (r) of a cell circle tangent to the main circle and having a same center as that of the auxiliary roller.

Description

TRACK DETERMINING METHOD FOR CAM OF CAM-TYPE ENGINE AND

HUMP TRACK PART, AND CAM WHOSE TRACK IS DETERMINED BY

SAID METHOD AND CAM-TYPE ENGINE HAVING HUMP TRACK PART

FIELD OF THE INVENTION

The present invention relates to a cam type engine and, more particularly, to a

track determining method for a cam and a hump track part of the cam-type engine, and

a cam-type engine having a cam and a hump track part whose tracks are determined by

the method.

BACKGROUND OF THE INVENTION

Gasoline and diesel engines according to the prior arts have a piston-

crankshaft mechanism. The piston-crankshaft mechanism converts the linear motion

of the piston into a rotational motion through the connecting rod. A four-stroke-cycle

engine makes one explosion while a four-stroke-cycle of intake, compression,

expansion and exhaust is carried out during a crankshaft effecting two times of rotation

while a piston moves back and forth two times.

There is a disadvantage in obtaining a large output in the engine thus described because one time of explosion is effected while a piston is reciprocated two times. There is another disadvantage in that the inertia force of a connecting rod is effected on the piston as lateral pressure in addition to the reaction force of an output

torque, to enhance a maximum value of the lateral pressure and, thus, to increase

friction and impact to a cylinder wall.

There is still another disadvantage in that forces of respectively different

directions are continuously applied to a connecting portion between the connecting rod,

piston and crankshaft, such that a material of high strength, rigidity and yielding point

is required and the manufacturing costs are high.

There is still a further disadvantage in that since the connecting rod and

crankshaft are used, the engine cannot be miniaturized in size and lightened in weight. As a way of overcoming the disadvantages of the reciprocating engine thus

described, there is disclosed a conventional cam type engine in Japanese Patent

Publication No Hei-08-004550. In the cam having a curved surface in the

conventional cam type engine disclosed in Japanese Patent Publication No. Hei-08-

004550, the main roller and the auxiliary rollers each radially located in a different

distance from the center of the cam form dissimilar tracking curvature lines of the

centers of the rollers whereas two tracking curvatures may overlap in some regions.

Accordingly, there is a drawback in that the main roller and the auxiliary rollers being

mounted on a central axial line of the piston and the rim of the cam being interposed

between the rollers cause the cam to be jammed and the output shaft inoperable for

rotation, thereby rendering the engine inoperable. To solve the afore-mentioned disadvantages, Korean Patent Application No.

2004-0003761, filed in South Korea by the present applicant (on January 19, 2004),

discloses a cam type engine where a main roller rolls along a track surface of a cam

while auxiliary rollers rolls along a track groove of a hump track part. As shown in FIGS. 1 and 2, Korean Patent Application No. 2004-0003761

includes a casing (30) radially disposed with four cylinders (34) at every 90 degrees

about a cam case (32), and pistons (36) reciprocating within the cylinders (34). A

cam (40) is fixed by a key (42) on an output shaft (38) disposed at a center of the cam

case (32). A main roller (44) externally contacting a track surface (peripheral surface:

40a) of the cam (40) is rotatably mounted at the piston (36). Auxiliary rollers (46,

48) are disposed at the piston (36) for lowering the piston (36) and for preventing the

main roller (44) from being derailed from the track surface (peripheral surface) of the

cam (40).

Furthermore, hump track parts (50, 52) having track grooves (50a, 52a) along

where the auxiliary roller (46) rides and rolls, are fixed at both axial sides of the cam (40) by the key (42) on the output shaft (38), and are fixed to a lateral surface of the cam (40) by a bolt (not shown).

Each cylinder (34) is mounted with suction/exhaust means having suction/exhaust valves (56, 58) and ignition means having an ignition plug (60). The cylinder (34) in a diesel engine is disposed with suction/exhaust means and fuel injection means.

The output shaft (38) is rotatably supported at the cam case (32) by a bearing

(62).

The piston (36) is centrally concaved at its lower portion, and flanges (36a,

36b) are formed at both sides of the lower portion of the piston. The main roller (44)

is rotatably mounted between the flanges (36a, 36b) by a first pin (64). Both the

flanges (36a, 36b) are disposed at their lower portion with the auxiliary rollers (46, 48)

rotatably mounted by second pins (66, 68).

The auxiliary rollers (46, 48) are disposed at an external surface of the flanges

(36a, 36b), and the track grooves (50a, 52a) are formed at an inner surface of the hump

track parts (50, 52).

In the cam-type engine thus described, when the piston (36) at an upper side is

referred to as a first piston, other pistons are, in the counterclockwise direction,

referred to as a second, a third and a fourth piston, respectively. All pistons are

operated in the same manner.

When the output shaft (38) is rotated, and the cam (40) and the hump track

parts (50, 52) are rotated counterclockwise, the piston (36) is lowered, from the state of

Fig. 1, along the cam crest by the main roller (44) rolling on the track surface (40a) of

the cam (40) and the auxiliary rollers (46, 48) riding along the track grooves (50a, 52a) of the hump track parts (50, 52) to open the suction valve (56), thereby allowing air- fuel mixture to be sucked into the cylinder (34) and reach the bottom dead center.

The cam (40) and the hump track parts (50, 52) are further rotated to raise the piston

(36) and to compress the air- fuel mixture in the cylinder (34), and the mixture is

ignited by the ignition plug (60) at an upper dead center to explode and expand. The piston (36) is again lowered to arrive at the bottom dead center, and rises

again to allow the exhaust gas in the cylinder (34) to be exhausted via the exhaust

valve (58) as depicted in FIG. 1. While the cam (40) and the hump track parts (50,

52) are rotated one time as mentioned above, four pistons (36) make two

reciprocations to effect a four-stroke-cycle of suction, compression, expansion and

exhaust.

SUMMARY OF THE INVENTION

There is a drawback in the conventional cam-type engine in that it is very

difficult to design and manufacture the engine since track surfaces of a cam and track

grooves of a hump track are dissimilar according to cam curvatures, size of main and

auxiliary rollers, and distances from the center of an output shaft to the bottom dead

center of the piston and from the center of an output shaft to the upper dead center of

the piston.

Particularly, in order for the main roller to roll smoothly along the track surfaces of the cam, it is necessary for the track surfaces and track grooves to be of optimum shape; however, designing and manufacturing such track surfaces and track

grooves is not an easy task.

The present invention is disclosed to solve these drawbacks, and it is an object

of the present invention to provide a track determining method for a cam and hump

track part of a cam-type engine, and a cam-type engine having the cam and the hump

track part whose tracks are determined by the method, so that the tracks of the cam and

hump tracks can be easily determined and a relation between cam and hump track

having an optimum track can be provided, thereby making it easy to design and

manufacture the cam-type engine and making the shape of the cam and hump track

most suitable as well.

According to the present invention, a track determining method of a cam in a

cam-type engine where a roller rolls along a cam track surface (CT) having a plurality

of crests and valleys is provided, where the cam track surface (CT) satisfies the

following relational expressions,

wherein a radius of a circumscribed circle externally contacting a crest of the cam track surface is (Ri), a radius of an inscribed circle internally contracting a valley

of the cam track surface is (R₂), a radius of a crest circle internally contacting the

circumscribed circle and matching a curvature of a crest surface of the cam is (R_a), a

radius of a valley circle externally contacting the crest circle and the inscribed circle

and matching a curvature of the valley surface of the cam is (R_b), a coordinate of a

point of contact between the crest circle and the valley circle is (a, b), a coordinate of a

point of contact between the inscribed circle and the valley circle is (y , Y ), and a

coordinate for a center of the valley circle is (c, c).

Preferably, the radius (Ra) of the crest circle satisfies the following relational

Further, according to the present invention, a track determining method of a

hump track part in a cam-type engine where a main roller rolls along a cam track surface having a plurality of crests and valleys and an auxiliary roller rolls along a hump track groove having a plurality of crests and valleys is provided, where the hump track satisfies the following relational expression,

ε=Xtanθ-(R+Y) wherein a coordinate of a cam track surface (CT) is (X, Y), a coordinate of a track line (ST) which is a center line of the hump track grooves is (x, y), an angle between the X-axis and straight line connecting a center (O) of the cam and a center of

a main circle (MR) is (θ ), a distance between the main circle and the track line on Y-

the axis passing the center of the main circle is (ε ), a radius of the main circle which

is the same as the main roller rolling along the cam track surface is (R ), and a radius

of a cell circle tangent to the main circle and having a same center as that of the

auxiliary roller is (r ).

The cam-type engine according to the present invention is mounted with a cam

or a hump track part whose tracks are determined by the methods.

According to the track determining method for a cam and hump track part of a

cam-type engine of the present invention, the tracks of the cam and hump tracks can be

easily determined and a relation between cam and hump track having an optimum

track can be provided, thereby making it easy to design and manufacture the cam-type engine and making the shape of the cam and hump track most suitable as well.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which:

FIG. 1 is a front sectional view of a cam-type engine according to the present invention; FIG. 2 is a lateral sectional view of a cam-type engine according to the present

invention;

FIG. 3 is a schematic explanatory diagram for obtaining an expression for

determining a track in relation to a cam track surface having four crests and valleys; FIG. 4 is a schematic explanatory diagram for obtaining an expression for

determining an optical radius of a crest circle in FIG. 3;

FIG. 5 is a schematic explanatory diagram for determining a coordinate of FIG.

4;

FIGS. 6 to FIGS. 8 are schematic drawings for explaining a method of

drawing hump track grooves based on a cam track surface according to the present

invention;

FIG. 9 is a schematic explanatory diagram for obtaining a relation of a track

line between a cam track surface and a hump track groove; and

FIG. 10 is a schematic explanatory diagram for obtaining an expression for

determining a track in relation to a cam track surface having six crests and valleys.

DETAH ED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention will now be described in detail with reference to the annexed drawings, where the present embodiment is not limiting the scope of the present invention but is given only as an illustrative purpose. FIG. 3 is a schematic explanatory diagram for obtaining an expression for

determining a track in relation to a cam track surface (CT) having four crests and

valleys each spaced 90 degrees apart.

In FIG. 3, a vertical axis crossing a center of a cam crest past a center (O) of a

cam is referred to as a Y-axis. A horizontal axis passing the center (O) of the cam is

referred to as an X-axis. A circle externally contacting the cam track surface (CT)

having a distance from the center (O) of the cam to the crest of the cam referred to as a

radius (Ri) is referred to as 'circumscribed circle'. A circle internally contacting the

cam track surface (CT) having a distance from the center (O) of the cam to the valley

of the cam referred to as a radius (R₂) is referred to as 'inscribed circle'. A circle

internally contacting the circumscribed circle and matching a curvature of a crest

surface of the cam and having a radius (R_a) with a center (Oi, O₂) is referred to as

'crest circle' A circle externally contacting two crest circles and the inscribed circle

between the two crest circles and matching a curvature of a valley surface and having a

radius (R_b) with a center (O₃) is referred to as 'valley circle'.

FIG 3 shows a cam track surface (CT) having four crests and valleys, each spaced 90 degrees apart, such that the center of the crest circle having a center (Oi) is positioned on the Y-axis while the center of the crest circle having a center (O₂) is positioned on the X-axis. The valley circle is tangent to the crest circle having the center (Oi) at a point of contact (Pi) and is tangent to the crest circle having the center (O₂) at a point of

contact (P₂), while the valley circle is tangent to the inscribed circle at a point of

contact (P₃ ), respectively.

Related equations of the crest circle (R_a), the circumscribed circle (Ri), and the

inscribed circle (R₂) can be defined by the following Expressions 1, 2 and 3.

[Expression 1 ]

[Expression 2]

[Expression 3 ) Rl=x^*+

If the coordinate of the center (O₃) is given as (c, c), the equation of the valley

circle (R_b) can be defined as the following expression 4.

[Expression 4]

The valley circle (Rb) passes the points of contact (Pi, P₂ and P₃) respectively,

and if the coordinates of the points of contact are respectively given as (a, b), (Y , Y ),

(b, a), and if the coordinates of the points of contact are respectively substituted for

Expression 4, the result can be expressed in the following Expressions 5, 6 and 7. [Expression 5]

[Expression 6]

[Expression 7]

The Y coordinate of the point of contact (P₂) can be expressed as follows. R -,

Expression 5 and Expression 7 are identical. If Expression 5 and Expression

6 are equal and solved, the following Expression 8 can be obtained.

[Expression 8]

As the crest circle and the valley circle contact at the point of contact (Pi), and

Expressions 4 and 1 are respectively differentiated, the following Expressions 9 and 10

can be obtained.

[Expression 9] γ 0 = 2( -c) + 2(7-c)— aX

[Expression 10] , 0 = Z + 2{Y-(R _l-R_a)} ^- aX The slopes of Expressions 9 and 10 are the same at the point of contact (Pi) having a coordinate (a, b), such that the following Expressions 11 and 12 can be

derived from Expressions 9 and 10. [Expression 11 ] dX . _ α- c ^^~dΫ^)a>b~ b-c

[Expression 12]

If Expressions 11 and 12 are equal, the following Expression 13 can be

obtained

[Expression 13] l-≤- a a-c 1 a or b-(_R_rR b-c b .Ri- b c a a a a

Meanwhile, the point of contact (Pi) having a coordinate (a, b) is a point on

Expression 1, such that when the coordinate (a, b) is substituted for Expression 1, the

following expression can be obtained.

R^a'+ib-iR R }²

If the above expression is solved, the following Expression 14 can be obtained. [Expression 14]

If Expression 14 is substituted for Expression 13, the following expression can

The above expression can be arranged in the following manner.

or

In the above-mentioned expressions, the value c can be expressed by the following Expression 15. [Expression 15 ]

Furthermore, the valley circle (R_b) is tangent to the inscribed circle (R₂) at the

point of contact (P₃) having a coordinate (Y , Y ) to be expressed by Expression 6.

From Expression 6, (R_b) is defined as per the following Expression 16. [Expression 16]

Furthermore, since the crest circle having a radius (R_a) with a center (Oi)

passes the point of contact (Pi) having a coordinate (a, b), the following equation can

be obtained from Expression 1.

R_a ² = a² + {b - (R, - R_a)}2

From the above equation, b can be defined by the following Expression 17. [Expression 17]

R R_a+ \lR²„-a²

Accordingly, if a radius of a circumscribed circle externally contacting a crest of a cam track surface is (Ri), if a radius of an inscribed circle internally contacting a

valley of the cam track surface is (R₂), a radius of a crest circle matching a curvature of a crest surface of a cam and internally contacting the circumscribed circle is (Ra), a radius of a valley circle matching a curvature of a valley surface of the cam and externally contacting the crest circle and the inscribed circle is (R_b)_, a coordinate of a

point of contact between the valley circle and the inscribed circle is (y , y ), and a

coordinate of a center of the valley circle is (c, c), then the cam track surface meets the

following related expressions.

R ι-R_a

where, (a) can vary up to (R_a) In other words, a≤ R_a Until (Rb) becomes zero, R_a is

R -. c — γ ^ _{ι 0r} R _mzκ =R j2R ^■ 2_l

Therefore, the range of (R_a)is given as follows.

Hereinafter, a radius of a most appropriate crest circle based on a critical condition is obtained when a radius (Ri) of a circumscribed circle and a radius (R₂) of an inscribed circle are given.

Referring to FIG. 3, a point (Pi) satisfying a = R_ais a point of contact between

the crest circle satisfying Expression 1 and the valley circle satisfying Expression 4.

Since the point of contact is parallel with the Y axis and a roller is perpendicular to the

movement of the piston, the point of contact becomes a dead spot where an engine

cannot be started due to a lack of generation of a perpendicular component force when

the engine is rotated by a starter. Therefore, a point satisfying a = R_a is the critical

point, such that a critical condition should be satisfied where "a" is smaller than R_a (a <

R_a), and "b" is larger than Ri - Ra (b > Ri - R_a) when a cam is designed. As a result, the relationship between (R₂ and R_a) is determined based on the

critical condition In other words, when a radius (Ri) of the circumscribed circle and

a radius (Ri) of the inscribed circle are determined,

b -R _] -R<_⁺ \j a-R ^~R l-R _and

where the critical values a = K_ and b = c = Ri - R_a> , the condition of a < R_a and b > Ri - R.. must be satisfied.

There are two "b" values (bi, b₂) for a given "a" value as shown in FIG 5, and b value of (b > Ri - R_a ) must be taken Referring to FIG 4, the critical point, i.e., when the crest circle (R_a) and the valley circle (Rb) contact with a degree of 90°, the following relationship is established.

If further defined, the following Expression 18 can be obtained.

[Expression 18]

R_b=^zR -2R_a

In FIG. 4, when the Pythagorean theorem is applied to a triangle formed by the

centers O, Oi, O₃,

(Ra + Rb)² + (R, + Rb)² = (R₂ + Rb)² , and taking the square root of both sides of the above equation yields

thereby obtaining Expression 19. [Expression 19]

Expression 18 and Expression 19 are equal to obtain the following Expression

20^. R₂-s[2R_a R_r 2R_a = — = v ^v 2 - 1

2-V 2 _ 1 ^~ ^ ^{Ra ~ ~}7ϊ^R2'R

[Expression 20]

_Ra _ ^ - (y 2 - l ).??,

Hereinafter, a method will be explained about determining the hump track

groove of a cam-type engine where the main roller rolls along a cam track surface

having a plurality of crests and valleys, and the auxiliary roller rolls along a hum track

groove having a plurality of crests and valleys.

When a cam track surface is determined as illustrated in FIGS. 3 or 4, the

hump track groove is determined based on the cam track surface, and a drawing

method thereof will be explained to begin with.

A main circle (MR) is drawn on the drawing of the cam track surface as shown

in FIG.6 such that the size of the main circle (MR) of the same as that of the mail roller

is made to be tangent to the cam track surface. A straight line (L) connecting the

center of the main circle (MR) to the center (O) of the cam is drawn A cell circle (SP) for containing an auxiliary roller is drawn to be tangent to the main circle (MR)

on the straight line (L) Then, an auxiliary circle (SR) of the same size as that of the

auxiliary roller is concentrically drawn with the cell circle (SP).

The size of the cell circle (SP) is determined by the size of a gap between the

mail roller and the auxiliary roller

In this condition, as shown in FIG. 7, while the main circle (MR) is made to be

tangent to the cam track surface (CT), the straight line (L) is rotated to draw the cell

circle (SP) or the auxiliary circle (SR) Then, a track circle as shown in FIG. 8 can be

obtained When the center of the track circle is connected, a track line (ST) of the

hump track groove can be obtained

Next, a relation between the cam track surface (CT) and track line (ST) of the

hump track groove is obtained

When a coordinate of the cam track surface (CT) is given as (X, Y), and a

coordinate of the track line (ST) is given as (x, y), and when an angle between X axis

and a straight line (L) connecting the center of the cam (O) and the center of the main

circle (MR) is given as (θ ), and when a distance between the main circle and the track

line on the Y axis passing the center of the main circle (MR) is given as (ε ), and when

a radius of a main circle having the same radius as that of the main roller riding and rolling along the cam track surface (CT) is given as (R), and when a radius of a cell circle tangent to the main circle and having the same center as that of the auxiliary roller is given as (r), the main circle (MR) and the cell circle (SP) satisfy the following

Expression 21.

[Expression 21 ]

If a coordinate of a center of the main circle (MR) is (ζ , ri ), tanθ = ^ I = X, and , such that η = ^'tanθ Subsequently, because ε=η-i?-T^' }_Π ΠG 7, ... ε =Λ:tanθ - C + y)

Meanwhile, FIG. 10 is a schematic explanatory diagram for obtaining an

expression for determining a track in relation to a cam track surface (CT) having six

crests and valleys each spaced 90 degrees apart. In the figure drawing, the symbol is

the same as that of FIG. 3, and the expression for determining the track may be

similarly obtained as in the case having four crests and valleys. Consequently, the

expression of the present invention can be applied to a cam track surface having a

plurality of crests and valleys by a coordinate converting the X axis to X' axis.

The foregoing description of the preferred embodiment of the present invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and

modifications and variations are possible in light of the above teachings or may be

acquired from practice of the invention. It is intended that the scope of the invention

be defined by the claims appended hereto, and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A track determining method of a cam in a cam-type engine where a roller rolls

along a cam track surface (CT) having a plurality of crests and valleys, wherein the

cam track surface (CT) satisfies the following relational expressions,

where, a radius of a circumscribed circle externally contacting a crest of the

cam track surface is (Ri), a radius of an inscribed circle internally contacting a valley

circumscribed circle and matching a curvature of a crest surface of the cam is (Ra), a

and matching a curvature of the valley surface of the cam is (Rb), a coordinate of a

point of contact between the inscribed circle and the valley circle is (y , Y ), and a coordinate for a center of the valley circle is (c, c).

2. The method as defined in claim 1, wherein the radius (Ra) of the crest circle

satisfies the following relational expression.

3. A track determining method of a hump track part in a cam-type engine where a

main roller rolls along a cam track surface having a plurality of crests and valleys and

an auxiliary roller rolls along a hump track groove having a plurality of crests and

valleys, wherein the hump track satisfies the following relational expressions,

(R + rf ^: = X-xf + ( +R + ε-yf ε=Xtanθ- R+Y) where, a coordinate of a cam track surface (CT) is (X, Y), a coordinate of a track line (ST) which is a center line of the hump track grooves is (x, y), an angle between X-axis and a straight line connecting a center (O) of the cam and a center of a main circle (MR) is (θ ), a distance between the main circle and the track line on the Y-axis passing the center of the main circle is (ε ), a radius (R) of the main circle of which is the same as the radius of the main roller rolling along the cam track surface, and a radius of a cell circle tangent to the main circle and having a same center as that of the auxiliary roller is (r ).

4. A cam-type engine having a cam whose track is determined by the method of

claim 1.

5. A cam-type engine having a cam whose track is determined by the method of

claim 2.

6. A cam-type engine having a hump track part whose track is determined by the

method of claim 3.