Patent Grant
8261703
This application is a 35 U.S.C. 371 national stage filing of International Application No. PCT/JP2007/000972, filed on Sep. 7, 2007, which claims priority to Japanese Patent Application No. 2006-250946 filed on Sep. 15, 2006, Japanese Patent Application No. 2006-250937 filed on Sep. 15, 2006, Japanese Patent Application No. 2006-259576 filed on Sep. 25, 2006, and Japanese Patent Application No. 2006-303125 filed on Nov. 8, 2006 in Japan. The contents of the aforementioned applications are hereby incorporated by reference.
The present invention relates to a variable stroke internal combustion engine, and in particular to a variable stroke engine that can simplify the power actuator for changing the stroke property.
Known is a variable stroke engine that comprises a plurality of links connecting a piston with a crankshaft, and a control link connecting one of the plurality of links with an control shaft supported by an engine main body so that the piston stroke may be varied by turning the control shaft. As actuating devices for turning the control shaft, those using servo motors and worm reduction gear devices are known (see Japanese patent laid open (kokai) publication no. 2004-150353).
According to the structure disclosed in Patent Document #1, a resilient force of a torsion spring or a downward force of a piston during an expansion stroke is used as a rotational torque for displacing the control shaft from a high compression ratio position to a low compression ratio position so that the speed of displacing the control shaft from the high compression ratio position to the low compression ratio position may be increased. As can be readily appreciated, when displacing the control shaft from the low compression ratio position to the high compression ratio position, because the resilient force of the torsion spring and the downward force of the piston oppose the force for this displacement, the servo motor must produce an adequate torque to overcome this resistance. Therefore, this prior art prevents the use of a servomotor which is compact and consumes little power.
It is known in a variable stroke engine to provide a spring biasing means in the actuator so as to assist the transition of the compression ratio from the high compression ratio to the low compression ratio so that the occurrence of a high load, high compression ratio condition owing to a delay in the speed of changing the compression ratio can be avoided, and also the frequency of the occurrence of abnormal combustion (engine knocking) owing to the self ignition of the fuel can be reduced (see Japanese patent laid open (kokai) publication no. 2004-150353).
In such a variable stroke engine, because the spring biasing means associated with the actuator is provided separately from the actuator, the actuator attached with the spring biasing means requires a large mounting space. This, combined with the need to avoid the interference of the spring biasing means with the surrounding component parts, caused the size of the engine to be come undesirably large.
It is desirable to operate a reciprocating internal combustion engine always at an optimum compression ratio by changing the compression ratio depending on the operating condition of the engine. To accomplish this goal, various variable compression ratio engines have been proposed, and such engines typically comprise an upper link pivotally connected to a piston of the engine, a lower link connecting the upper link to the crankpin of a crankshaft, an control shaft extending along a row of cylinders, a control cam provided on the control shaft in an eccentric relationship, a control link connecting the control cam to the upper link or lower link, and a rotary actuator for angularly actuating the control shaft.
In such a variable compression ratio engine, a large force pushes down the piston during the expansion stroke, and a component of this force is transmitted to the control shaft via the link mechanism so that the control shaft is thereby continually subjected to a force in a certain direction. Therefore, a relatively small actuating force can angularly actuate the control shaft in this direction, but a relatively large actuating force is required to angularly actuate the control shaft in the opposite direction because the link mechanism is required to be actuated against the component of the force transmitted from the piston.
It was proposed to provide a hydraulic piston that acts on the control shaft via a slider mechanism in such a variable compression ratio engine to reduce the load transmitted from the control shaft to the rotary actuator and control an undesired rotation of the control shaft (see Japanese patent laid open (kokai) publication No. 2003-322036).
Also, in Japanese patent laid open (kokai) publication no. 2004-150353, to speed up the transition from a high compression ratio condition of an engine to a low compression condition, it is proposed to interpose a spiral spring between an end of the control shaft and the cylinder block so that the control shaft may be angularly biased toward the low compression ratio position.
However, according to the conventional variable compression ratio engines disclosed in Japanese patent laid open (kokai) publication no. 2004-150353 and Japanese patent laid open (kokai) publication No. 2003-322036, because of the need for a hydraulic circuit including a hydraulic pump, a hydraulic actuator and a control valve, the increased complexity of the system complicates the manufacturing process and causes an increase in the size and weight of the system.
Also, according to the conventional variable compression ratio engine disclosed in Japanese patent laid open (kokai) publication no. 2004-150353, because a spiral spring is attached to an end of the control shaft, the size of the engine in the axial direction of the control shaft has to be increased. In particular, when a relatively large torque is required, the wire diameter of the spiral spring has to be increased, and the diameter of the spiral spring may become so great that there may be some difficulty in installing the spiral spring in the engine. If the spiral spring is closely wound so as to reduce the overall diameter of the spiral spring, the friction between adjacent turns of the coil wire causes a hysteresis that prevents the generation of an appropriate torque.
Even when a torsion coil spring is used in a similar arrangement, the tilting of the coil spring may cause a hysteresis. Again, when the diameter of the coil wire is increased to ensure a required torque to be produced and the number of turns is increased to ensure a required range of rotational angle, the size of the coil spring in the axial direction of the control shaft inevitably increases, and this causes a problem when installing the coil spring in the engine. Be it a spiral spring or a torsion coil spring, the spring constant is fixed, and the torque property that can be obtained is limited to a linear one.
In view of such problems of the prior art, a primary object of the present invention is to provide a novel variable stroke engine free from such problems of the prior art.
A second object of the present invention is to provide an improved variable stroke engine that can simplify the power actuator means for angularly actuating an control shaft.
A third object of the present invention is to provide a variable stroke engine that can apply a biasing torque to the control shaft at an appropriate level for driving the control shaft in either direction without increasing the size of the engine in the direction of the control shaft, and that can offer a high level of freedom in designing the biasing torque.
A fourth object of the present invention is to provide a variable stroke engine that can apply a biasing torque to the control shaft at an appropriate level for driving the control shaft in either direction without increasing the weight of the engine, and that can offer a high level of freedom in designing the biasing torque.
According to the present invention, at least part of such objects can be accomplished by providing a variable stroke engine, comprising; a plurality of links connecting a piston with a crankshaft; a control member disposed on an engine main body so as to be moveable in two directions over a prescribed range relative to the engine main body; a control link connecting one of the plurality of links with the control member; and an actuator for displacing the control member; wherein the actuator comprises a ratchet mechanism that utilizes a force transmitted from the piston to the control member as an actuating force for the control member.
According to this arrangement, because the reciprocating movement of the piston is utilized for moving the connecting point between the control link and engine main body in either direction, the external actuator may consist of a highly compact one or may be totally done away with, and this provides a significant improvement in simplifying the displacing means for the control link. Although the “ratchet mechanism” in a narrow meaning may mean a combination of a toothed wheel and a pawl allow effective motion in one direction only, this term as used herein means not only the vane-type actuator combined with a suitable hydraulic circuit shown in the illustrated embodiments but also other devices such as a linear piston/cylinder device.
According to a preferred embodiment of the present invention, the ratchet mechanism comprises a hydraulic chamber separated into a first and second hydraulic chamber by a piston, a check valve having a first and second end, and a switching valve having three positions for selectively connecting the first and second chambers to the check valve, the three positions including a first position connecting the first and second chambers with the first and second ends of the check valve, respectively, a second position connecting the first and second chambers with the second and first ends of the check valve, respectively, and a third position closing the first and second chambers.
If the engine further comprises a spring member that biases the control member in one of the two directions, the shortfall in the actuating force provided by the inertia force of the piston undergoing a reciprocating movement can be filled by the spring force, and by suitably adjusting the supplementary input, the displacing speed of the connecting point may be accelerated when moving from the high compression ratio side to the low compression ratio side, and the compression ratio can be quickly changed so that engine knocking can be avoided when rapidly accelerating the engine. Such a spring member may consist of a torsion coil spring, but may also consist of a compression coil spring interposed between an arm of the control shaft and an engine main body.
If the spring member is at least partly received in a housing wall of the actuator or is otherwise at least partly received in a part of the actuator, the size of the actuator fitted with the spring biasing means can be minimized, and the spring biasing means is prevented from interfering with the other component parts so that the reliability of the actuator can be enhanced. In particular, if the spring member is received at least partly received in drive shaft of the actuator, the internal space of the drive shaft is effectively utilized, and the size of the actuator can be both reduced.
If the spring member extends at least partly along a bearing journal of the drive shaft, the weight of the drive shaft can be reduced, and the size of the actuator can be even further reduced.
If the one end the spring member is engaged by an engagement opening formed in an end wall of the drive shaft, and the other end thereof is engagement by an engagement opening formed in the housing of the actuator, the engagement openings both opening out outwardly, states of engagement can be confirmed from outside.
Now the present invention is described in the following in more detail in terms of concrete embodiments with reference to the appended drawings. In various embodiments of the present invention, like parts are denoted with like numerals without repeating description of such parts. Also, as can be readily appreciated by a person skilled in the art, various variations of one embodiment are applicable to any other embodiments although the description may not cover every such possibility.
The crankshaft 30 is essentially identical to that of a conventional fixed compression ratio engine, and comprises a crank journal 30J (rotational center of the crankshaft) supported in a crankcase 4 and a crankpin 30P which is radially offset from the crank journal. An intermediate point of the lower link 60 is supported by the crankpin 30P so as to be able to tilt like a seesaw. An end 60a of the lower link 60 is connected to a big end 61b of the upper link 61, and a small end 61a of the upper link 61 is connected to a piston pin 13. A counterweight is provided in association with the crankshaft 30 so as to cancel a primary rotary oscillation component of the piston movement, but is not shown in the drawings as it is not different from that of a conventional engine.
The other end 60b of the lower link 60 is connected to a small end 63a of a control link 63 which is similar in structure to a connecting rod that connects a piston with a crankshaft in a normal engine. A big end 63b of the control link 63 is connected to an eccentric portion 65P of a control shaft 65, which is rotatably supported by the crankcase 4 and extends in parallel with the crankshaft 30, via a bearing bore formed by using a bearing cap 63c.
The control shaft 65 includes a journal portion 65J (rotational center of the control shaft) which is provided in a suitable part of the engine main body, and the eccentric portion 65J supports the big end 63b of the control link 63 so as to be movable in the crankcase 4 within a prescribed range (about 90 degrees in the illustrated embodiment). The rotational angle of the control shaft 65 can be continually varied and retained at a desired angle by a hydraulic ratchet mechanism (which will be described hereinafter) provided in a suitable part of the crankcase 4. This forms the displacing means for changing the position of the connecting point of the control link 63 on the engine main body.
In this engine, by rotatively actuating the control shaft 65, the position of the big end 63b of the control link 63 can be moved between the position (horizontally inward position/low compression ratio) illustrated in
In other words, a piston stroke varying mechanism is formed by the upper link 61, lower link 60, control link 63 and control shaft 65. Thereby, the stroke of the piston 11 within the cylinder 5 or the positions of the top dead center and bottom dead center can be varied continuously between the one extreme state indicated by letter A in
In this variable stroke engine, as the crankshaft 30 turns owing to the downward force of the piston caused by the combustion of fuel during the expansion stroke, a tensile force is applied to the control link 63 via the lower link 60 supported by the crankpin 30P. This is transmitted to the eccentric portion 65P of the control shaft 65, and this creates a torque that tends to turn the control shaft 65 from the high compression ratio position to the low compression ratio position (in clockwise direction in the drawings).
The downward force acting on the piston starts increasing at a time point immediately before the top dead center, reaches a maximum value during the combustion, and virtually disappears in the latter part of the expansion stroke. The inertia force of the piston as it moves upward causes a downward force on the control link 63, and this cause a torque that tends to turn the control shaft from the low compression ratio position to the high compression ratio position (counter clockwise direction in the drawings). Therefore, the control shaft 65 is subjected to an alternating torque as illustrated in
Between the control shaft 65 and the crankcase 4 is provided a hydraulic ratchet mechanism AC consisting of a closed-circuit hydraulic system as shown in
When the vane shaft 66 fitted with the vanes 87 is to be turned only in clockwise direction in
Conversely, when the vane shaft 66 is to be turned only in counter clockwise direction, the solenoid valve V is put to the right position VR. Then, the rotation of the vane shaft 66 is permitted only when a counter clockwise torque is applied thereto, and is prevented by the action of the check valve C0 when a clockwise torque is applied thereto.
By thus extracting only the part of the alternating torque acting upon the control shaft 65 in one sense, the vane shaft 66 can be angularly actuated in an incremental manner. Once the control shaft 65 has turned to a desired angular position, the solenoid valve V is put to the neutral position VC and the hydraulic pressure in each of the oil chambers 86a and 86b is sealed off so that the vane shaft 66 is held stationary in this position. Thus, without using any special actuating device, the rotation of the control shaft 65 in either direction and holding of the control shaft 65 at a desired position can be accomplished.
By connecting the outlet passage an oil pump P to the two oil passages 88 and 89 communicating with the oil chambers 86a and 86b, respectively, via check valves C1 and C2, respectively, in such a direction as to permit flow of oil to the passages 88 and 89, even when an oil leakage develops in the hydraulic ratchet mechanism AC, oil can be quickly replenished.
The hydraulic ratchet mechanism AC is not necessarily required to be of a rotary type but may also be of a linear piston type. In such a case, the actuator may consist of a linear movement/rotary movement conversion mechanism in which an arm is fixed to the control shaft 65, and a piston rod is connected to the free end of the arm. When a linear piston type hydraulic ratchet mechanism AC is used, the mechanism for displacing the connecting point between the control link 63 and engine main body may consist of a slide mechanism for linearly displacing the big end 63b of the control link 63 instead of the control shaft 65 which is configured to undergo an angular movement as discussed above.
The durability of the hydraulic ratchet mechanism AC can be improved by controlling the range of the angular movement of the vane shaft 66 so that the vane shaft 66 may stop short of the circumferential end surface of each oil chamber 86a and 86b of the fixed housing 84 as it undergoes an angular movement, and thereby preventing each vane 87 from striking the circumferential end surfaces of the corresponding oil chambers 86a and 86b.
As shown in
As can be appreciated from the foregoing description, when angularly actuating the control shaft 65, the transition from the high compression ratio position to the low compression ratio position is effected by using the torque represented by area a in
When the supplementary torque produced by the torsion coil spring 141 is selected so that the rotational speed of the control shaft may differ from one direction to another, and the reversing position of the alternating torque is lowered as indicated by the double-dot chain-dot line in
In the embodiment illustrated in
The hydraulic circuit for a vane-type hydraulic actuator AC for controlling the variable stroke link mechanism CR, instead of the hydraulic ratchet mechanism AC discussed above, is now described in the following with reference to
Similarly as the embodiment illustrated in
Therefore, in
When angularly actuating the drive shaft 66 of the actuator AC and hence the control shaft 65 from the low compression ratio side to the high compression ratio side (counter clockwise in
According to the illustrated embodiment, because the spring biasing means such as the torsion coil spring 141 is internally provided in the actuator AC, the sized of the actuator fitted with the spring biasing means can be minimized, and the spring biasing means is prevented from interfering with the other component parts so that the reliability of the actuator can be enhanced. A spring member that can store energy is desirable for use as the supplementary input applying means for its simplicity, but other actuators such as pneumatic motors and electric motors may also be used. Also, by suitably modifying the link geometry, the torque that is applied to the control shaft may be made to differ from one rotational direction to another.
As shown in
This variable compression ratio engine E consists of an in-line, four-cylinder, four-stroke OHC engine, and an engine main body 1 thereof comprises a cylinder block 2 formed with four cylinders 5 arranged laterally one next another, a cylinder head 3 integrally attached to a deck surface of the cylinder block 2 via a gasket 6, an upper block 40 (upper crankcase) integrally formed in a lower part of the cylinder block 2, and a lower block 41 (lower crankcase) integrally attached to the lower surface of the upper block 40. A crankcase 4 is jointly formed by the upper block 40 and the lower block 41. The upper surface of the cylinder head 3 is closed by a head cover 9 integrally attached thereby via a seal member 8, and an oil pan 10 is integrally attached to the lower surface of the lower block 41 (lower crankcase).
A piston 11 is slidably received in each of the four cylinders 5 of the cylinder block 2, and the part of the lower surface of the cylinder head 3 opposing the piston 11 is formed with a combustion chamber 12 and an intake port 14 and an exhaust port 15 communicating with the combustion chamber 12. An intake valve 16 is provided in the intake port 14, and an exhaust valve 17 is provided in the exhaust port 15, each configured to be selectively opened and closed as required. A valve actuating mechanism 18 is provided on the cylinder head 3 so as to open and close the intake valves 16 and exhaust valves 17. The valve actuating mechanism 18 comprises an intake camshaft 20 and exhaust camshaft 21 rotatably supported by the cylinder head 3, and an intake rocker arm 24 and exhaust rocker arm 25 that are rotatably supported by an intake rocker shaft 22 and exhaust rocker shaft 23, respectively, for each cylinder and functionally intervene between the intake camshaft 20 and intake valve 16 and between the exhaust camshaft 21 and exhaust valve 17, respectively. Thereby, the rotation of the intake and exhaust camshafts 20 and 21 causes the intake and exhaust valves 16 and 17 to be opened and closed at a prescribed timing via the rocking movements of the intake and exhaust rocker arms 24 and 25 against the valve closing forces of valve springs 26 and 27.
As illustrated in
The synchronized transmission mechanism 28 is covered by a chain case 29 which is attached to an end of the engine main body 1 corresponding to an axial end of the crankshaft 30. The four intake ports 14 formed so as to correspond to the four cylinders 5 open out from the rear surface of the engine main body 1 or rearward with respect to the vehicle body, and are connected to an intake manifold 34 of an intake system IN. The intake system IN has a per se known structure, and detailed description of this part is omitted from this description.
The four exhaust ports 15 formed so as to correspond to the four cylinders 5 open out from the front surface of the engine main body 1 or forward with respect to the vehicle body, and are connected to an exhaust manifold 35 of an exhaust system EX. The exhaust system EX has a per se known structure, and detailed description of this part is omitted from this description.
As shown in
As can be appreciated from
As shown in
Now referring to
Thus, an angular displacement of the control shaft 65 around its axial center causes an angular displacement of the control link 63 which in turn causes a change in the constraint on the movement of the lower link 60 so that the stroke property of the piston 11 including the top dead center position is varied, and this enables the compression ratio of the Engine E to be changed at will.
In the illustrated embodiment, as will be discussed hereinafter, a spring biasing means SP provided in association with the vane type hydraulic actuator AC accelerates the actuation of the control shaft 65 in one direction from the high compression ratio to the low compression ratio, and ensures an efficient and stable combustion in the engine by avoiding a high load, high compression ratio situation by compensating for a shortage in the actuating torque for the control shaft 65.
Thus, the variable compression ratio mechanism CR is formed by the upper link 61, first connecting pin 62, lower link 60, second connecting pin 64 and control link 63.
As shown in
As shown in
The structure of the hydraulic actuator AC equipped with the spring biasing means SP for driving the control shaft 65 is now described in the following.
As shown in
An open outer face of the outer housing HUo is sealed off in a liquid tight manner by a cover member 102 fixedly attached thereto by using a plurality of fastening bolts 101. Inside the vane shaft 66 is defined a cylindrical hole 103 having an open outer end and a closed bottom end, and a coil spring SP forming the spring biasing means is received in this cylindrical hole 103. The inner end of the coil spring SP is engaged by an engagement hole 105 formed in a bottom wall 104 of the receiving hole 103, and the outer end thereof is engaged by an engagement hole 106 formed in the cover member 102. The engagement holes 105 and 106 open out toward the exterior of the housing so that the state of engagement of the coil spring SP can be confirmed from the exterior. The engagement hole 106 formed in the cover member 102 is closed by a seal bolt 107 so as to avoid leakage of oil from the receiving hole 103.
The spring force of the coil spring SP urges the control shaft 65 in one direction or in a direction to cause a transition from the high compression side to the low compression side.
As shown in
As shown in
Because the spring biasing means SP is internally provided in a drive shaft 66 of the actuator AC, the internal space of the drive shaft is effectively utilized, and the size of the actuator can be both reduced.
Because the spring biasing means SP extends to a bearing portion of a vane shaft (drive shaft) 66 of the actuator AC, the internal space of the drive shaft is effectively utilized, and the weight of the drive shaft and the size of the actuator can be both reduced.
Because a drive shaft 66 of the actuator AC is internally provided with a receiving hole 103 having a closed bottom, and receiving the spring biasing means SP therein; and the spring biasing means SP has one end engaged by an engagement hole 105 provided in a bottom wall 104 of the receiving hole 103 and another end engaged by an engagement hole 106 provided in a cover member 102 covering the receiving hole 103; the engagement holes 105, 106 opening outwardly from the receiving hole 103, the engagement state of the spring biasing means can be readily confirmed from outside.
For instance, the actuator of the present invention is not limited to hydraulic actuators such as the one used in the illustrated embodiments, but may also consist of various electric actuators. Also, the spline coupling between the drive shaft of the actuator and the control shaft may be replaced with outer coupling means including pressure fitted couplings. The hydraulic circuits described in connection with
The engine E given as a third embodiment of the present invention and illustrated in
The crankshaft 30 is essentially no different from that of a conventional fixed compression ratio engine, and comprises a crank journal 30J (rotational center of the crankshaft) supported by a crankcase (engine main body) 4 and a crankpin 30P radially offset from the crank journal 30J. An intermediate point of the lower link 60 is supported by the crankpin 30P so as to be able to tilt like a seesaw. An end 60a of the lower link 60 is connected to a big end 61b of the upper link 61, and a small end 61a of the upper link 61 is connected to a piston pin 13.
The other end 60b of the lower link 60 is connected to a small end 63a of a control link 63 which is similar in structure to a connecting rod that connects a piston with a crankshaft in a normal engine. A big end 63b of the control link 63 is connected to an eccentric portion 113 of an control shaft 65, which is rotatably supported by the crankcase 4 and extends in parallel with the crankshaft 30, via a bearing bore formed by using a bearing cap 63c.
In a middle part of the control shaft 65 is formed a driven gear 116, and a vane-type hydraulic actuator AC for angularly actuating the control shaft 65 is formed with a drive gear 141 that meshes with the driven gear 116 (see
In this engine E, by rotatively actuating the control shaft 65, the position of the big end 63b of the control link 63 can be moved from the position illustrated in
The control shaft 65 is provided with webs 117, and a web connecting portion 118 (first connecting portion) is formed on an end of each of the webs 117 opposite to the corresponding eccentric pin 13 with respect to the neutral axial line of the control shaft 65. A plurality of main body connecting members 119 each formed with a pair of main body connecting portions 120 (second connecting portion) are attached to the inner surface of the crankcase 4. A compression coil spring device (biasing means) 121 is interposed between each main body connecting portion 120 and the corresponding web connecting portion 118.
Each compression coil spring device 121 is provided with an upper connecting piece (first connecting piece) 122 at an upper then thereof and a lower connecting piece (second connecting piece) 123 at a lower end thereof, each of these connecting pieces are pivotally connected to the corresponding web connecting portion 118 and main body connecting portion 120 via pins (first and second pins) 124 and 125, respectively. Between the upper connecting piece 122 and the lower connecting piece 123 are interposed a pair compression coil springs 126 and 127 that are coaxially nested with each other. The pins 124 and 125 are disposed on the axial line of the compression coil springs 126 and 127.
As shown in
Each journal 115 is connected to the adjacent eccentric pins 113 via the corresponding webs 117. For instance, the web 117a is interposed between the first journal 115a and the first eccentric pin 113a. Similarly, eight webs 117a to 117h are arranged so as to correspond to the first to fifth journals 115a to 115e.
Each journal 115a to 115e is rotatably supported by a bearing (not shown in the drawings) formed in the crankcase 4, and the third journal 115c which is centrally located in the control shaft 65 is provided with a driven gear 116 configured to be actuated by the hydraulic actuator AC.
The webs 117a and 117b interposing the first eccentric pin 113a and the webs 117g and 117h interposing the fourth eccentric pin 113d are formed in such a manner that the web connecting portions 118a, 118b, 118c and 118d extend in an opposite direction to the eccentric pins 113 with respect to the neutral central axial line of the control shaft 65. The inner surface of the crankcase 4 (not shown in the drawings) is provided with a pair of main body connecting members 119a and 119g which are each provided with a pair of connecting portions 120a and 120b or 120g and 120h.
Between each web connecting portion 118a, 118b, 118g, 118h and the corresponding main body connecting portion 120a, 120b, 120g, 120h is interposed a compression coil spring device 121a, 121b, 121g, 121h. Thus, four compression coil spring devices 121 are arranged symmetrically with respect to the central part of the control shaft 65, two of them on one axial side of the central part of the control shaft and the other two of then on the other axial side thereof. The web connecting portions 118a, 118b, 118g, 118h are configured that the pins 124a, 124b, 124g, 124h pivotally supporting the upper connecting pieces 122a, 122b, 122g, 122h are disposed coaxially with one another. Similarly, the main body connecting members 119a and 119g are disposed in such a manner that the pins 125a, 125b, 125g, 125h pivotally supporting the lower connecting pieces 123a, 123b, 123g, 123h are disposed coaxially with one another.
As shown in
Each compression coil spring 127, 128 consists of a constant-pitch cylindrical coil spring, and the wire diameter and pitch of the compression coil spring 127 having a smaller coil diameter are both smaller than those of the compression coil spring 128 having a larger coil diameter. The coil ends of each compression coil spring consist of closed ends so that the ends coils may be supported evenly over their entire circumferences. Also, because the end turns are substantially perpendicular to the axial line, each compression coil spring 127, 128 sits in a stable manner, and does not readily buckle. So that the two mutually nested compression coil springs may not interfere with each other, the turns of the two compression coil springs 126 and 127 are reversed relative to each other.
The spring seat 138, 139 of each of the upper and lower connecting pieces 122 and 123 is provided with a pair of stepped seat surfaces which correspond to the different inner diameters of the two compression coil springs 127 and 128. The upper connecting piece 122 is U-shaped, and is provided with a pair of bifurcated ends 122A and 122B that interpose the web connecting portion 118 therebetween (see
As shown in
By passing the pin 124 through a pin receiving hole 134 formed in the web connecting portion 118 and pin receiving holes 130a and 130b of the upper connecting piece 122, the upper connecting piece 122 is connected to the web connecting portion 118. The inner circumferential surface of each of the pin receiving holes 120a and 120b are formed with grooves, and the pin 124 is held in position by fitting C-clips 136a and 136b in these grooves. Similarly, by passing the pin 125 through pin receiving holes 135a and 135b formed in the main body connecting portion 120 and a pin receiving hole 131 of the lower connecting piece 123, the lower connecting piece 123 is connected to the main body connecting portion 120, and C-clips 137a and 137b are fitted in grooves formed in the pin receiving holes 135a and 135b on either outer axial side of the pin 125.
The oil holes 132a and 132b formed in the upper ends of the U-shaped bifurcated portions 122A and 122B of the upper connecting piece 122 as discussed earlier extend to the pin receiving holes 130a and 130b so that the engine oil splashed in the crankcase can be introduced to the sliding surface of the pin 124. The upper ends of the oil holes 132a and 132b are each countersunk so that the oil splashes may be effectively caught thereby. The positions of the oil holes 133a and 133b are determined so as not to overlap with the lower connecting piece 123 in plan view or are determined such as to avoid any obstacle to the capturing of the oil splashes to be located above the oil holes 132a and 132b. The upper end of the oil hole 142 is also countersunk.
The force acting on the control shaft 65 is described in the following with reference to
When the control shaft 65 is actuated under this condition, whereas a relatively small force is required to turn the control shaft 65 in clockwise direction and to thereby move the eccentric pin 113 upward, it requires a significant amount of force to turn the control shaft in counter clockwise direction and to thereby move the eccentric pin 113 downward because the force that pulls the control link 63 upward must be overcome.
However, because the compression coil spring device 121 is interposed between each web connecting portion 118 extending from the control shaft 65 and the corresponding main body connecting portion 120, the control shaft 65 is subjected to a bias torque that tends to turn the control shaft 65 in counter clockwise direction. Therefore, the maximum output that is required to angularly actuate the control shaft 65 can be minimized, and it becomes possible to use a relatively small actuator.
Because the compression coil spring device 121 can be installed on one side or below the control shaft 65 in the crankcase 4, the dimension of the engine E in the axial direction of the neutral axial line of the control shaft 65 is prevented from increasing. As it is possible to install a plurality of such devices, the size of each individual device can be minimized. Because the main body connecting members 119 are provided within the crankcase 4, the structure of the various connecting portions are prevented from becoming excessively complex.
Because the compression coil spring device 121 is connected to the web connecting portion 118 and main body connecting portion 120 via a link mechanism using pins 124 and 125, the line of action on the compression coil spring 121 can be kept fixed without causing the tilting and buckling of the compression coil springs 126 and 127 so that the required spring property can be obtained at all times. Through the use of the compression coil spring incorporated with a link mechanism as a biasing means for producing a biasing torque, hysteresis owing to tilting of the spring and frictions can be favorably controlled. Also, the freedom of design is enhanced so that the spring load and stroke can be changed at will, and a non-linear spring can be used. Therefore, the device can be easily configured to suit various types of engines.
As can be appreciated from
When a large torque is required to be produced by each compression coil spring device 121, it can be accomplished by extending the arm length of the web 117 measured from the center of the control shaft 65 to the web connecting portion 118, but as it requires the length of the spring to be increased so as to correspond to the increased stroke, it may impair the space efficiency due to a need to increase the size of the compression coil spring device 121. However, by coaxially nesting one of the compression coil springs 127 in the other compression coil spring 126, a greater torque can be applied to the control shaft 65. By combining a larger number of compression coil springs, more sophisticated torque properties may be given to the compression coil spring device 121. Such possibilities enhance the freedom in the design of the compression coil spring device 121.
As shown in
Owing to the provision of the oil holes 132 and 133 for conducting engine oil to the sliding parts of the pins 124 and 125 as shown in
The oil hole 142 formed in each upper connecting piece 122 in communication with the interior of the sleeve 128 supplies lubricating oil to the sliding part between the sleeve 128 and the rod 129 received therein so that the control shaft 65 can be actuated in an even more favorable manner and the weight of the upper connecting piece 122 can be reduced. The oil hole 142 also functions as an air hole for venting and admitting air out of and into the interior of the sleeve 128 when the rod 129 moves out of and into the interior of the sleeve 128, respectively, and this also contributes to a smooth sliding movement between the sleeve 128 and rod 129.
The hydraulic actuator AC is connected to the central part of the control shaft 65, but may also be connected one end or each end of the control shaft 65 or any other intermediate part of the control shaft 65. The biasing means of the illustrated embodiment consisted of compression coil springs, but may also consist of tension springs, air springs or hydraulic cylinders. The illustrated embodiment used four compression coil spring devices 121, but may also use one or two of such compression coil spring devices 121. The number of the compression coil spring devices may be even numbers such as six and eight but may also be odd numbers such as five and seven. The layout of the compression coil spring devices may not be necessarily symmetric with respect to the center of the control shaft, and the main body connecting members 19 may not be necessarily mounted on the inner surface of the crankcase 4 but may also be mounted in any other part of the engine main body.
Each device serving as the biasing means used a pair of compression coil springs in the foregoing embodiment, but may also use one, three or more compression coil springs. Each compression coil spring may not be a constant-pitch cylindrical coil spring but may consist of an uneven-pitch coil spring, a conical spring, an hourglass-shaped coil spring or a barrel-shaped spring. A taper coil spring using a tapering coil wire or other coil springs using coil wires of various cross sections such as rectangular, elliptic or oval shapes or combinations of such springs may also be used. For instance, by using an uneven-pitch coil spring, a nonlinear loading property may be realized.
The pins 124 and 125 are not necessarily required to be on the common axial line of the compression coil springs 126 and 127, by may also be offset from the common axial line of the compression coil springs 126 and 127. By using such an arrangement, an extension of the rod 129 may be allowed to pass entirely through the upper connecting piece 122 so that the rod 129 may extend beyond the part received in the sleeve 128.
In the foregoing embodiment, because the connecting portions are formed in the outer wall of the engine block, and the biasing means connected therefore constantly applies a large force to the outer wall of the engine block, the rigidity of the connecting portions must be increased in a corresponding manner, and this may require the thickness of the engine block outer wall may have to be increased. This may necessitate an increase in the weight of the engine main body. The embodiments illustrated in
The engine E given as a fourth embodiment of the present invention and illustrated in
The crankshaft 30 is essentially no different from that of a conventional fixed compression ratio engine, and comprises a crank journal 30J (rotational center of the crankshaft) supported by a crankcase (engine main body) 4 and a crankpin 30P radially offset from the crank journal 30J. An intermediate point of the lower link 60 is supported by the crankpin 30P so as to be able to tilt like a seesaw. An end 60a of the lower link 60 is connected to a big end 61b of the upper link 61, and a small end 61a of the upper link 61 is connected to a piston pin 13.
The other end 60b of the lower link 60 is connected to a small end 63a of a control link 63 which is similar in structure to a connecting rod that connects a piston with a crankshaft in a normal engine. A big end 63b of the control link 63 is connected to an eccentric portion 113 of an control shaft 65, which is rotatably supported by the bearing block 4b and a shaft holder 151 attached to the bearing block 4b, via a bearing bore formed by using a bearing cap 63c.
As shown in
In a middle part of the control shaft 65 is formed a driven gear 116, and a vane-type hydraulic actuator AC for angularly actuating the control shaft 65 is formed with a drive gear 141 that meshes with the driven gear 116 (see
In this engine E, by rotatively actuating the control shaft 65, the position of the big end 63b of the control link 63 can be moved from the position illustrated in
The control shaft 65 is provided with webs 117, and a web connecting portion 118 (first connecting portion) is formed on an end of each of the webs 117 opposite to the corresponding eccentric pin 13 with respect to the neutral axial line of the control shaft 65. A plurality of main body connecting members 119 each formed with a pair of main body connecting portions 120 (second connecting portion) are attached to the inner surface of the crankcase 4. A compression coil spring device (biasing means) 121 is interposed between each main body connecting portion 120 and the corresponding web connecting portion 118.
Each compression coil spring device 121 is provided with an upper connecting piece (first connecting piece) 122 at an upper then thereof and a lower connecting piece (second connecting piece) 123 at a lower end thereof, each of these connecting pieces are pivotally connected to the corresponding web connecting portion 118 and main body connecting portion 120 via pins (first and second pins) 124 and 125, respectively. Between the upper connecting piece 122 and the lower connecting piece 123 are interposed a pair compression coil springs 126 and 127 that are coaxially nested with each other. The pins 124 and 125 are disposed on the axial line of the compression coil springs 126 and 127.
As shown in
Each journal 115 is connected to the adjacent eccentric pins 113 via the corresponding webs 117. For instance, the web 117a is interposed between the first journal 115a and the first eccentric pin 113a. Similarly, eight webs 117a to 117h are arranged so as to correspond to the first to fifth journals 115a to 115e.
Each journal 115a to 115e is rotatably supported by a bearing (not shown in the drawings) formed in the crankcase 4, and the third journal 115c which is centrally located in the control shaft 65 is provided with a driven gear 116 configured to be actuated by the hydraulic actuator AC.
The webs 117a and 117b interposing the first eccentric pin 113a and the webs 117g and 117h interposing the fourth eccentric pin 113d are formed in such a manner that the web connecting portions 118a, 118b, 118c and 118d extend in an opposite direction to the eccentric pins 113 with respect to the neutral central axial line of the control shaft 65. A pair of main body connecting members 119a and 119g are attached to the lower surface of the shaft holder 151, and each main body connecting member is provided with a pair of main body connecting portions 120a, 120b, 120g, 120h.
Between each web connecting portion 118a, 118b, 118g, 118h and the corresponding main body connecting portion 120a, 120b, 120g, 120h is interposed a compression coil spring device 121a, 121b, 121g, 121h. Thus, four compression coil spring devices 121 are arranged symmetrically with respect to the central part of the control shaft 65, two of them on one axial side of the central part of the control shaft and the other two of then on the other axial side thereof. The web connecting portions 118a, 118b, 118g, 118h are configured that the pins 124a, 124b, 124g, 124h pivotally supporting the upper connecting pieces 122a, 122b, 122g, 122h are disposed coaxially with one another. Similarly, the main body connecting members 119a and 119g are disposed in such a manner that the pins 125a, 125b, 125g, 125h pivotally supporting the lower connecting pieces 123a, 123b, 123g, 123h are disposed coaxially with one another. The compression coil spring devices 121 are not different from that illustrated in
The force acting on the control shaft 65 is described in the following with reference to
When the control shaft 65 is actuated under this condition, whereas a relatively small force is required to turn the control shaft 65 in clockwise direction and to thereby move the eccentric pin 113 upward, it requires a significant amount of force to turn the control shaft in counter clockwise direction and to thereby move the eccentric pin 113 downward because the force that pulls the control link 63 upward must be overcome.
However, because the compression coil spring device 121 is interposed between each web connecting portion 118 extending from the control shaft 65 and the corresponding main body connecting portion 120, the control shaft 65 is subjected to a bias torque that tends to turn the control shaft 65 in counter clockwise direction. Therefore, the maximum output that is required to angularly actuate the control shaft 65 can be minimized, and it becomes possible to use a relatively small actuator.
Because the compression coil spring device 121 can be installed on one side or below the control shaft 65 in the crankcase 4, the dimension of the engine E in the axial direction of the neutral axial line of the control shaft 65 is prevented from increasing. As it is possible to install a plurality of such devices, the size of each individual device can be minimized. Because the main body connecting members 119 are provided within the crankcase 4, the structure of the various connecting portions are prevented from becoming excessively complex.
Because the compression coil spring device 121 is connected to the web connecting portion 118 and main body connecting portion 120 via a link mechanism using pins 124 and 125, the line of action on the compression coil spring 121 can be kept fixed without causing the tilting and buckling of the compression coil springs 126 and 127 so that the required spring property can be obtained at all times. Through the use of the compression coil spring incorporated with a link mechanism as a biasing means for producing a biasing torque, hysteresis owing to tilting of the spring and frictions can be favorably controlled. Also, the freedom of design is enhanced so that the spring load and stroke can be changed at will, and a non-linear spring can be used. Therefore, the device can be easily configured to suit various types of engines.
The main body connecting portions 119 are attached to the shaft holder 151 which has a high rigidity for supporting the control shaft 65 by using threaded bolts 156 so that the increase in the weight of the engine E can be avoided as opposed to the case where the oil pan 10 is reinforced by increasing the thickness thereof and the main body connecting portions 119 are attached to the oil pan 10 although the oil pan 10 is otherwise not required to have any significant rigidity. Dedicated threaded bolts 156 are used for securing the main body connecting members 119 to the shaft holder 151 in the illustrated embodiment, but it is also possible to commonly use the threaded bolts 155 for securing the shaft holder 151 also for securing the main body connecting members 119 to the shaft holder 151. More specifically, each mounting hole for securing the main body connecting members 119 may be aligned with one of the mounting holes 154 of the shaft holder 151 so that both the main body connecting members 119 and the shaft holder 151 may be secured by using common threaded bolts 155. Thereby, the number of component parts can be reduced, the assembly work can be simplified, and the increase in the weight of the engine E can be minimized. Also, the pins 124 and 125 are not necessarily required to be disposed on the common axial line of the compression coil springs 126 and 127, and may be offset from this common axial line.
One of the compression coil springs 165 has a greater coil wire diameter and a greater coil pitch than the other compression coil spring 166, and hence have a fewer effective turns and a higher spring constant than the other. The spring support surfaces of the upper connecting piece 162, lower connecting piece 163 and retainer 164 are each provided with a stepped spring seat 176-179 that corresponds to the inner diameter of the corresponding compression coil spring. The compression coil springs 165 are 166 are thus disposed in a coaxial relationship with the spring ends retained by these stepped spring seats 176-179.
The upper connecting piece 162 is formed with an oil hole 182 communicating with the interior of the sleeve 167, and an axial center of the rod 171 of the retainer 164 is formed with an oil hole 175 communicating with the interior of the sleeve 170 via the interior of the flange 169. The length of the rod 171 is greater than the depth of the sleeve 167 so that the tip of the rod 171 abuts the bottom of the sleeve 167 before the compression coil spring 166 deflects more than the tolerable stress of the spring 166 permits.
By thus combining a plurality of compression coil springs 165 and 166 having different spring constants in a serial connection, spring properties that can change over a wide range can be achieved, and it becomes easier to ensure an adequate stroke and load that are required to turn the control shaft by a prescribed angle. More specifically, when a single uneven-pitch spring is used for the purpose of obtaining a non-linear spring constant, the use of a coil wire having an increased diameter to ensure the maximum load prevents a desired stroke to be obtained. If the number of turns of the coil increased to ensure a required stroke, the size of the compression coil spring increases. If the wire diameter is reduced, a required stroke may be ensured without increasing the size of the device, but an adequate large spring load cannot be obtained. However, by combining a plurality of compression coil springs 165 and 166 having different spring constants in a serial connection, it becomes possible to obtain a required stroke and an adequate spring load at the same time.
Owing to the oil holes 175 and 182, the engine oil introduced into the sleeve 167 via the oil hole 182 of the upper connecting piece 122 lubricates the sliding engagement between the sleeve 167 and rod 171, and further reaches the interior of the sleeve 170 via the oil hole 175 to lubricate the sliding engagement between the sleeve 170 and rod 168 as well. Thereby, the control shaft 65 can be actuated in a smooth manner. Furthermore, because the oil hole 182 functions as an air hole for the interior of the sleeve 167 and the oil hole 175 functions as an air hole for the interior of the sleeve 170, the control shaft 65 can be actuated in an even more smooth manner.
Another modified embodiment of the fourth embodiment of the present invention is described in the following with reference to
The compression coil spring device 121 is provided with an upper connecting piece 122 in an upper end thereof and a lower connecting piece 123 in a lower end thereof, and these connecting pieces 122 and 123 are connected to the web connecting portion 118 and main body connecting portion 185, respectively, by using pins 124 and 125. Between the upper connecting piece 122 and lower connecting piece 123 are interposed a pair of compression coil springs 126 and 127 which are nested with each other in a coaxial relationship. The pins 124 and 125 are disposed on the common axial line of the compression coil springs 126 and 127.
By thus forming the main body connecting portion 185 integrally with the shaft holder 151, the number of component parts is reduced, the assembly work is simplified, and the weight of the engine can be minimized.
This concludes the description of the preferred embodiment, but the present invention is not limited by the foregoing embodiment. For instance, although the illustrated embodiment was directed to an in-line four-cylinder engine, the present invention is equally applicable to parallel engines, V-engines, six-cylinder engines and eight-cylinder engines. The control shafts of the illustrated embodiment consisted of control shafts but may also consist of other control members such as those linearly actuated by hydraulic cylinders or the like as long as they can displace the pivot points of the control links 63.
The contents of the original Japanese patent application on which the Paris Convention priority claim is made for the present application as well as the contents of the prior art references mentioned in this application are incorporated in this application by reference.
Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.
a is a hydraulic circuit diagram showing the structure of the hydraulic ratchet mechanism;
b is a hydraulic circuit diagram showing the structure of the vane-type hydraulic actuator;
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-250937 | Sep 2006 | JP | national |
| 2006-250946 | Sep 2006 | JP | national |
| 2006-259576 | Sep 2006 | JP | national |
| 2006-303125 | Nov 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/000972 | 9/7/2007 | WO | 00 | 3/13/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/032439 | 3/20/2008 | WO | A |
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| 10-131916 | May 1998 | JP |
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| Number | Date | Country | |
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| 20100006069 A1 | Jan 2010 | US |
