JP3676488B2 - Offset piston engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an offset piston engine in which a cylinder axis is offset to the side of a crankshaft axis.
[0002]
[Prior art]
In an engine that repeats the exhaust stroke → intake stroke → compression stroke → expansion stroke, the compression force applied to the connecting rod increases in the compression stroke and the expansion stroke in which both the intake valve and the exhaust valve are closed. At this time, if the connecting rod is parallel to the cylinder axis, a thrust force that presses the piston side wall against the cylinder side wall is not generated, but if the connecting rod is inclined with respect to the cylinder axis, the inclination angle is As the pressure increases, the thrust force, which is a lateral component of the compression force, increases, and there is a problem that the sliding resistance increases because the piston side wall is strongly pressed against the cylinder side wall.
[0003]
Therefore, in the expansion stroke in which the maximum compressive force is applied to the connecting rod, the cylinder axis is advanced with respect to the crankshaft axis with respect to the crankshaft axis so that the angle formed by the connecting rod with respect to the cylinder axis is as small as possible. An offset is disclosed in Japanese Patent Laid-Open No. 56-98531. According to this, when the piston descends due to the pressure of the combustion gas in the expansion stroke, the connecting rod becomes substantially parallel to the cylinder axis due to the offset, so the thrust force which is a lateral component of the compressive force of the connecting rod Can reduce the sliding resistance between the piston and the cylinder.
[0004]
[Problems to be solved by the invention]
By the way, when the cylinder axis is offset to the crankshaft rotation direction advance side with respect to the crankshaft axis as described above, the inclination angle of the connecting rod is further increased by the offset in the compression stroke in which the compressive force of the connecting rod is large after the expansion stroke. On the contrary, the thrust force increases and the thrust force increases, and the decrease in the thrust force in the expansion stroke is offset by the increase in the thrust force in the compression stroke.
[0005]
Therefore, in the publication described above, the offset amount with respect to the piston stroke is set to a predetermined value to reduce the sliding resistance between the piston and the cylinder. It is extremely difficult to sufficiently reduce the dynamic resistance.
[0006]
The present invention has been made in view of the above circumstances, and an object thereof is to further reduce sliding resistance between a piston and a cylinder in an offset piston engine in which a cylinder axis is offset with respect to a crankshaft axis. To do.
[0008]
[Means for Solving the Problems]
  To achieve the above purpose,Claim1Invention described inTheA first cylinder having a rank shaft, an axis offset to the crankshaft rotation direction advance side with respect to the crankshaft axis, and a second cylinder having an axis offset to the crankshaft rotation direction delay side with respect to the crankshaft axis A first piston slidably fitted to the first cylinder, a second piston slidably fitted to the second cylinder, a first connecting rod connecting the first piston to the crankshaft, In an offset piston engine having a second connecting rod for connecting two pistons to a crankshaft, a first piston pin pivotally supporting the first piston on a small end of the first connecting rod is disposed with respect to the center of the first piston. Offset to the crankshaft rotation direction advance side , The second piston pin pivotally supporting the second piston to the small end of the second connecting rod, offset to the crankshaft rotation direction delayed side with respect to the center of the second pistonIn addition, the closing timing of the intake valve of the first cylinder is delayed from the closing timing of the intake valve of the second cylinder, and the opening timing of the exhaust valve of the first cylinder is set to the opening timing of the exhaust valve of the second cylinder. Also delayedIt is characterized by that.
[0010]
  And claims2The invention described in claim 11In addition to the configuration ofNo.Set the valve lift of the intake valve of one cylinder smaller than the valve lift of the intake valve of the second cylinderIn addition, the valve lift of the exhaust valve of the first cylinder is set larger than the valve lift of the exhaust valve of the second cylinder, and the invention described in claim 3 is the structure of claim 1 or 2 In addition, a plurality of first and second cylinders are arranged in parallel in a staggered manner as viewed from the cylinder head in the same cylinder block.It is characterized by that.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0012]
1 to 21 show a first embodiment of the present invention. FIG. 1 is a front view of the engine (viewed in the direction of arrow 1 in FIG. 2), and FIG. 3 is a sectional view taken along line 3-3 in FIG. 2, FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, FIG. 5 is a sectional view taken along line 5-5 in FIG. 7 is a sectional view taken along line 7-7 in FIG. 2, FIG. 8 is an enlarged sectional view taken along line 8-8 in FIG. 2, FIG. 9 is a sectional view taken along line 9-9 in FIG. 11 is a sectional view taken along the line 11-11 of FIG. 8, FIG. 12 is a perspective view of the cylinder block, FIG. 13 is a view showing a modification of the breather chamber, and FIG. 14 is an explanatory view of the operation of the first cylinder. 15 is a diagram illustrating the operation of the second cylinder, FIG. 16 is a graph showing the thrust force of the piston, FIG. 17 is a diagram illustrating the crank angle of each stroke of the engine, and FIG. 18 is a diagram of the crank pin corresponding to each cylinder. Shows a phase, FIG. 19 is a graph showing the valve timing, FIG. 20 is an explanatory view of a time area calculation method of the valve lift, FIG. 21 is a diagram showing the relationship between the valve lift and the valve effective opening area.
[0013]
As shown in FIGS. 1 to 4, the four-cylinder engine E is coupled to the cylinder block 2 that rotatably supports the crankshaft 1, the cylinder head 3 that is coupled to the upper surface of the cylinder block 2, and the upper surface of the cylinder head 3. And the oil pan 5 coupled to the lower surface of the cylinder block 2. The crankshaft 1 having the crankshaft axis Ls extending in the left-right direction of the vehicle body rotates in the direction indicated by the arrow A in FIGS.
[0014]
The cylinder block 2 is formed with # 1 to # 4 cylinders having axes parallel to each other, of which the # 1 cylinder and the # 3 cylinder are the first cylinder 6.₁, 6₁The remaining # 2 cylinder and # 4 cylinder are the second cylinder 6₂, 6₂Configure. 1st cylinder 6₁, 6₁(# 1 cylinder and # 3 cylinder) are the first cylinder axis Lc₁The first cylinder axis Lc₁Is offset by a distance D from the crankshaft axis Ls in the direction of rotation of the crankshaft 1, that is, in front of the vehicle body.₂, 6₂(# 2 cylinder and # 4 cylinder) are the second cylinder axis Lc₂The second cylinder axis Lc₂Is offset from the crankshaft axis Ls by a distance D on the delay side of the crankshaft 1 in the rotational direction (see FIG. 4).
[0015]
As a result, the four cylinders 6₁, 6₁; 6₂, 6₂Are arranged in a zigzag shape in a plan view (see FIG. 3), the dimension of the engine E in the direction of the crankshaft axis Ls can be shortened compared to that of the series arrangement, and the crankshaft axis of the engine E can be shortened. The dimension in the direction perpendicular to Ls can be shortened compared to the V-type arrangement.
[0016]
Each first cylinder 6₁First piston 7 slidably fitted to₁The first connecting rod 8₁Are connected to the crankshaft 1 through the second cylinders 6.₂Second piston 7 slidably fitted to₂The second connecting rod 8₂Is connected to the crankshaft 1 via 1st piston 7₁The first connecting rod 8₁The first piston pin 9 pivotally supported on the small end₁Is the first cylinder axis Lc₁Is offset from the crankshaft 1 in the rotational direction by a distance d, and the second piston 7₂The second connecting rod 8₂Second piston pin 9 pivotally supported on the small end₂Is the second cylinder axis Lc₂On the other hand, the crankshaft 1 is offset by a distance d toward the rotation direction delay side (see FIG. 4).
[0017]
As shown in FIGS. 3, 5, and 6, a drive sprocket 12 of the valve gear is integrally formed on the inner side (left side in FIG. 3) of the flywheel 11 provided on the outer end (right end in FIG. 3) of the crankshaft 1. The drive sprocket 12 is connected to a driven sprocket 14 provided at the outer end (right end in FIG. 3) of the camshaft 13 supported by the head cover 4 via a cam chain 15. Inside the cam chain chamber 16 formed at the ends of the cylinder block 2 and the cylinder head 3 to accommodate the cam chain 15, an idle sprocket 17 for guiding the tension side of the cam chain 15 and two upper and lower chain guides 18 are provided. , 19 and a chain tensioner 20 that contacts the slack side of the cam chain 15 and applies a predetermined tension.
[0018]
As best shown in FIG. 3, the cam chain chamber 16 that houses the cam chain 15 is offset to the front side of the vehicle body with respect to the crankshaft axis Ls. This is because the cam cylinder chamber 16 is offset from the crankshaft axis Ls toward the rear of the vehicle body 6.₂(# 4 cylinder) and the first cylinder 6 offset to the front of the vehicle body₁This is because it is formed using the space between (# 3 cylinder). In the lower part of the cam chain 15, that is, in the vicinity of the drive sprocket 12 provided on the crankshaft 1, the inner end of the cam chain 15 (the left end in FIG. 3) is the outer end of the water jacket 21 that surrounds the outer periphery of the # 4 cylinder (see FIG. 3 (right end in 3), the distance P enters the inside (left side in FIG. 3).
[0019]
Thus, the four cylinders 6 arranged in a staggered manner₁, 6₁; 6₂, 6₂The cam chain 15 is disposed at the end of the cam chain 15 using a dead space formed so as to be biased to one side from the crankshaft axis Ls, and the lower inner end of the cam chain 15 is connected to the outer end of the water jacket 10 of the # 4 cylinder. Since the cam chain 15 and the flywheel 11 are arranged as close to the inside of the crankshaft 1 as possible, the dimension of the engine E in the direction of the crankshaft axis Ls can be shortened. Moreover, since the drive sprocket 12 and the driven sprocket 14 can be connected by a single cam chain 15 according to the above layout, the number and weight of the cam chain and the sprockets accompanying it can be reduced.
[0020]
As shown in FIGS. 1, 2, and 7, the # 1 cylinder to the # 4 cylinder include two intake valves 21 and 21, and two exhaust valves 22 and 22, respectively. The intake manifold 23 coupled to the rear surface of the cylinder head 3 is connected to the intake valves 21..., 21... Of the # 1 cylinder to # 4 cylinder via four intake ports 24. . A fuel injection valve 25 is provided at the tip of each intake port 24 so as to face the intake valves 21 and 21. An exhaust manifold 26 is coupled to the front surface of the cylinder head 3, and an exhaust pipe 27 is coupled to the front end gathering portion of the exhaust manifold 26. Four exhaust ports 28 formed in a bifurcated shape in the cylinder head 3 to connect the base end of the exhaust manifold 26 branched into four branches and the exhaust valves 22 ... 22 of the # 1 cylinder to # 4 cylinder. Is formed. The EGR passage 30 is connected to the exhaust port 28 of the # 4 cylinder.
[0021]
As is apparent from FIG. 7, the cylinder head 3 is coupled to the cylinder block 2 by eleven head bolts 29a to 29k. Among them, five head bolts 29a, 29b, 29c, 29d, 29e are arranged so as to sandwich the left and right sides of the four intake ports 24, and the other four head bolts 29f, 29g, 29h, 29i are four. It arrange | positions between the branch parts of the individual exhaust port 28 .... The remaining two head bolts 29j and 29k are arranged on the right end side and the left end side of the cylinder head 3.
[0022]
In this way, by arranging the head bolts 29f, 29g, 29h, 29i between the branch portions of the bifurcated exhaust ports 28, the outer circumferences of the # 1 cylinder to the # 4 cylinder are each tightened with three head bolts, That is, the outer periphery of the # 4 cylinder is head bolts 29a, 29b, 29f, the outer periphery of the # 3 cylinder is head bolts 29b, 29c, 29g, the outer periphery of the # 2 cylinder is the head bolts 29c, 29d, 29h, and the # 1 cylinder The outer periphery can be tightened with the head bolts 29d, 29e, 29i to obtain a uniform fastening force. Particularly, in the engine E in which the # 1 cylinder to the # 4 cylinder are arranged in a staggered manner as in the embodiment, the space between the cylinders is narrow, so that the space for arranging the head bolts is insufficient, but the branch portion of the exhaust port 28. The problem is solved by using the space between them.
[0023]
Although the space between the branch portions of the intake ports 24 can be used for the arrangement of the head bolts, the shape of the intake ports 24 is restricted by the head bolts. It is necessary to consider so that the atomization characteristics of the fuel injected from ... are not affected.
[0024]
As shown in FIGS. 8 to 10, the first cylinder 6₁The camshaft 13 and the first rocker shaft 31 are located above the (# 1 cylinder).₁Are installed in parallel. In FIG. 8, the first rocker shaft 31₁Shows only the center line by a chain line. First rocker shaft 31₁In the first swing arm 32₁Is pivotally supported so that the first swing arm 32 can swing.₁A roller 33 provided in the intermediate portion of the cam contacts an intake cam 34 provided on the camshaft 13 and a first swing arm 32.₁The bifurcated front end of each of the two abuts against the stems 36 and 36 of the pair of intake valves 21 and 21 urged by the valve springs 35 and 35 in the valve closing direction.
[0025]
The first rocker shaft 31₁In addition, the first swing arm 32₁A pair of first rocker arms 37 so as to sandwich₁, 37₁The middle part of the frame is pivotably supported. Each first rocker arm 37₁A roller 38 provided at one end of the cam contacts an exhaust cam 39 provided on the camshaft 13 and each first rocker arm 37.₁The other end of the exhaust valve 22 abuts on the stem 41 of each exhaust valve 22 urged by the valve spring 40 in the valve closing direction. A pair of first rocker arms 37₁, 37₁The first cylinder 6 is disposed at the bottom of the guide cylinder 42 disposed therebetween.₁A spark plug 43 facing the combustion chamber is attached.
[0026]
Thus, the first cylinder 6 corresponding to the # 1 cylinder₁The structure of the valve gear is described, but the first cylinder 6 corresponding to the # 3 cylinder₁The structure of the valve gear is substantially the same.
[0027]
As shown in FIGS. 8 and 11, the second cylinder 6₂The camshaft 13 and the second rocker shaft 31 are located above the (# 2 cylinder).₂Are installed in parallel. In FIG. 8, the second rocker shaft 31₂Shows only the center line by a chain line. Second rocker shaft 31₂In the second swing arm 32₂Is pivotably supported by the second swing arm 32.₂The roller 33 provided in the intermediate portion of the cam contacts the exhaust cam 39 provided on the camshaft 13 and the second swing arm 32.₂The bifurcated front end of each of the two abuts against the stems 41 and 41 of the pair of exhaust valves 22 and 22 urged in the valve closing direction by the valve springs 40 and 40.
[0028]
Second rocker shaft 31₂In addition, the second swing arm 32₂A pair of second rocker arms 37 so as to sandwich₂, 37₂The middle part of the frame is pivotably supported. Each second rocker arm 37₂A roller 38 provided at one end of the cam abuts against an intake cam 34 provided on the camshaft 13 and each second rocker arm 37.₂The other end of the valve abuts on the stem 36 of each intake valve 21 urged by the valve spring 35 in the valve closing direction. A pair of second rocker arms 37₂, 37₂The second cylinder 6 is disposed at the bottom of the guide cylinder 42 disposed between them.₂A spark plug 43 facing the combustion chamber is attached.
[0029]
Thus, the second cylinder 6 corresponding to the # 2 cylinder₂The structure of the valve operating apparatus of the second cylinder 6 has been described.₂The structure of the valve gear is substantially the same.
[0030]
As is clear from a comparison of FIGS. 8, 9 and 11, the first cylinder 6₁Valve gear and second cylinder 6₂The valve operating apparatus has a structure in which the inclination angles of the intake valves 21 and 21 and the inclination angles of the exhaust valves 22 and 22 are the same with respect to the camshaft 13 and are symmetrical in the front-rear direction. That is, the first cylinder 6₁1st rocker shaft 31₁, First swing arm 32₁, Roller 33, first rocker arm 37₁, 37₁And rollers 38, 38 are respectively connected to the second cylinder 6₂The second rocker shaft 31₂, Second swing arm 32₂, Roller 33, second rocker arm 37₂, 37₂The rollers 38 and 38 are the same member and are interchangeable. The difference is that the first cylinder 6₁Is the first swing arm 32₁To drive the intake valves 21 and 21, and the first rocker arm 37₁, 37₁The exhaust cylinders 22 and 22 are driven by the second cylinder 6₂Is the second swing arm 32₂The exhaust valves 22 and 22 are driven by the second rocker arm 37.₂, 37₂Thus, the intake valves 21 and 21 are driven.
[0031]
As described above, the first cylinder 6₁Valve gear and second cylinder 6₂The first valve 6 has the same valve inclination angle and a longitudinally symmetrical structure.₁And the second cylinder 6₂This makes it possible not only to prevent variations in the intake / exhaust characteristics of the cylinders and cause each cylinder to perform uniform combustion, but also to greatly reduce the number of parts and contribute to cost reduction.
[0032]
As shown in FIGS. 3 and 12, the outer wall 44 and the intermediate portion in the left-right direction of the side wall of the cylinder block 2 on the vehicle body rear side, that is, the recess surrounded by the # 2 cylinder, the # 3 cylinder, and the # 4 cylinder are provided. A pair of breather chambers 47 and 48 defined by a partition wall 46 having a communication hole 45 at the upper end and extending in the vertical direction are formed so as to open on the deck surface of the cylinder block 2. One breather chamber 47 communicates with the crank chamber through an inlet opening 49 and communicates with the other breather chamber 48 through the communication hole 45. The other breather chamber 48 has an outlet opening 50 and a tube (not shown). To the intake system of the engine E. Note that the upper surface openings of the breather chambers 47 and 48 are closed by the lower surface of the cylinder head 3 coupled to the cylinder block 2.
[0033]
Thus, by forming the breather chambers 47 and 48 in the recess surrounded by the # 2 cylinder, the # 3 cylinder and the # 4 cylinder on the three sides, the outer wall 44 and the partition wall 46 function as reinforcing ribs, and the cylinder block 2 can contribute to the improvement of rigidity. As a result, the rigidity can be increased without increasing the front-rear width of the cylinder block 2, and the transmitted sound is reduced by the breather chambers 47 and 48, so that the noise of the engine E is reduced as compared with the case where a simple reinforcing rib is provided. can do.
[0034]
FIG. 13 shows a modified example of the breather chambers 47 and 48. The outer walls 44a to 44d and the outer walls 44a to 44d are formed in a recess surrounded by the # 2 cylinder, # 3 cylinder and # 4 cylinder formed in the cylinder block 2. A pair of breather chambers 47 and 48 having a communication hole 45 at the end and defined by a partition wall 46 extending in the horizontal direction are formed so as to open to the side surface of the cylinder block 2. The lower breather chamber 47 communicates with the crank chamber through the inlet opening 49 and also communicates with the upper breather chamber 48 through the communication hole 45. The opening portions of the breather chambers 47 and 48 are closed by a cover 52 connected through a gasket 51, and the upper breather chamber 48 is connected to an intake system of the engine E through an outlet opening 50 formed in the cover 52 and a tube (not shown). Connected to.
[0035]
Also by this modification, the same effect as the embodiment shown in FIG. 12 can be obtained.
[0036]
Next, the operation of the embodiment of the present invention having the above-described configuration will be described.
[0037]
FIG. 14 shows the first cylinder 6 positioned on the advancing direction of the crankshaft 1 (the front side of the vehicle body relative to the crankshaft 1).₁This is to explain the operation of. As is clear from (B) showing the expansion stroke, the first cylinder axis Lc₁Is offset from the crankshaft axis Ls by a distance D toward the advancing direction of the crankshaft 1, so that the connecting rod is moved to the first cylinder axis Lc.₁It is substantially parallel to. Therefore, even if a strong compressive force acts on the connecting rod, the first cylinder axis Lc₁The thrust force in the direction perpendicular to the angle, that is, the thrust force that presses the piston side wall against the cylinder side wall is extremely small.
[0038]
On the other hand, as is clear from (A) showing the compression stroke, the first cylinder axis Lc₁Is offset from the crankshaft axis Ls by a distance D toward the advancing direction of the crankshaft 1, so that the connecting rod is moved to the first cylinder axis Lc.₁As a result, the thrust force Fx, which is a component of the compressive force F of the connecting rod, is increased. However, the piston pin that pivotally supports the small end of the connecting rod on the piston is connected to the first cylinder axis Lc.₁As a result, the moment in the direction of the arrow B acts on the piston and the skirt portion of the piston is pressed against the cylinder side wall (see a part).
[0039]
Thus, even if the piston side wall is pressed against the cylinder side wall by the thrust force Fx, the piston skirt portion having low rigidity is pressed against the cylinder side wall by the moment B and deforms, so that the load applied to the piston side wall is dispersed. Can do. In particular, the piston skirt is located at a distance from the combustion chamber, is relatively low temperature, and the supply of lubricating oil is sufficient and the amount of frictional heat generated is small. In addition to preventing seizure resistance, the fuel consumption can be reduced by reducing the frictional force.
[0040]
FIG. 15 shows the second cylinder 6 located on the side of the crankshaft 1 that is behind the rotation direction (the rear side of the vehicle body relative to the crankshaft 1).₂This is to explain the operation of. As is clear from the compression stroke (A), the second cylinder axis Lc₂Is offset from the crankshaft axis Ls by a distance D to the rotation direction delay side of the crankshaft 1, so that the connecting rod is moved to the second cylinder axis Lc.₂It is substantially parallel to. Therefore, even if a strong compressive force acts on the connecting rod, the second cylinder axis Lc₂The thrust force in the direction perpendicular to the angle, that is, the thrust force that presses the piston side wall against the cylinder side wall is extremely small.
[0041]
On the other hand, as is apparent from (B) showing the expansion stroke, the second cylinder axis Lc₂Is offset from the crankshaft axis Ls by a distance D to the rotation direction delay side of the crankshaft 1, so that the connecting rod is moved to the second cylinder axis Lc.₂As a result, the thrust force Fx, which is a component of the compressive force F of the connecting rod, is increased. However, the piston pin that pivotally supports the small end of the connecting rod on the piston is connected to the second cylinder axis Lc.₂On the other hand, by offsetting the crankshaft 1 by a distance d toward the rotation direction delay side, a moment in the direction of arrow B acts on the piston, and the skirt portion of the piston is pressed against the cylinder side wall (see portion b).
[0042]
Thus, the first cylinder 6 described with reference to FIG.₁As in the case of, the deformation of the skirt portion of the low-rigidity piston can reliably prevent seizure between the piston and the cylinder, improve seizure resistance, and reduce fuel consumption by reducing frictional force. .
[0043]
FIG. 16 shows how the thrust force Fx at the height of the piston pin that pivotally supports the small end of the connecting rod on the piston changes according to the crank angle. Cylinder 6₁In addition, (B) corresponds to the second cylinder, respectively. As is apparent from the figure, the thrust force Fx is reduced in the present example (solid line shown) in which the piston pin is offset by the distance d compared to the conventional example (shown by the broken line) in which the offset is not applied. You can see that This is because the piston tilts due to the moment B based on the offset of the piston pin, so that the skirt portion is pressed against the cylinder side wall to receive the thrust force, and the thrust force at the height of the piston pin above the skirt portion is correspondingly increased. By decreasing.
[0044]
Now, the first cylinder 6₁And the second cylinder 6₂Are offset by a distance D to the crankshaft rotation direction advance side and delay side, respectively.₁And the second cylinder 6₂The crank angle of the intake / expansion stroke and the crank angle of the compression / exhaust stroke become non-uniform. This will be described with reference to FIG. 17. The offset amount of each cylinder is D, the crank radius is r, the connecting rod length is R, the inclination angle of the connecting rod at the top dead center is α, and the bottom dead center is If the inclination angle of the connecting rod is β,
Intake / expansion stroke crank angle of the first cylinder; 180 ° −α + β> 180 °
Intake / expansion stroke crank angle of the second cylinder; 180 ° + α−β <180 °
First cylinder compression / exhaust stroke crank angle: 180 ° + α−β <180 °
Crank angle of compression / exhaust stroke of the second cylinder; 180 ° −α + β> 180 °
α = sin α^-1{D / (R + r)}
β = sinα^-1{D / (R−r)}
α <β
Is established.
[0045]
Accordingly, the first cylinder 6₁And the second cylinder 6₂If the valve timings are set to be the same, the piston position at the opening and closing timing of each valve is the first cylinder 6₁And the second cylinder 6₂Therefore, there is a problem in that the output imbalance occurs and the full load performance also decreases. Therefore, in this embodiment, the following means are taken.
[0046]
In order to make the # 1 cylinder to the # 4 cylinder explode at equal intervals, the phases of the four crank pins in the crankshaft are set as shown in FIG. Here, α is the inclination angle α of the connecting rod at the top dead center described above.
[0047]
In a normal engine that is not an offset piston engine, the intake valve opening timing at the time of 1 mm valve lift is 15 ° ATDC, the intake valve closing timing is 25 ° ABDC, the exhaust valve opening timing is 25 ° BBDC, and the exhaust valve closing timing is 15 ° BTDC. In order to apply the same setting to the engine of this embodiment, it is necessary to adopt the following valve timing. That is, as shown in FIG.₁And the second cylinder 6₂In either case, the intake valve opening timing (15 ° ATDC) and the exhaust valve closing timing (15 ° BTDC) do not need to be substantially changed, but the first cylinder 6 is offset by the offset.₁Since bottom dead center shifts to about 5 ° ABDC side, the intake valve closing timing is set to 30 ° ABDC, which is 5 ° behind the normal engine intake valve closing timing (25 ° ABDC), and the exhaust valve opening timing is set. Needs to be set to 20 ° BBDC which is delayed by 5 ° from the exhaust valve opening timing (25 ° BBDC) of the normal engine. Also, the second cylinder 6 is offset by₂Since the bottom dead center shifts to about 5 ° BBDC side, the intake valve closing timing is set to 20 ° ABDC, which is 5 ° earlier than the normal engine intake valve closing timing (25 ° ABDC), and the exhaust valve opening timing is set. Needs to be set to 30 ° BBDC, which is 5 ° earlier than the normal engine exhaust valve opening timing (25 ° BBDC).
[0048]
Accordingly, the first cylinder 6₁The exhaust valve opening period of the second cylinder 6 decreases by 5 °,₂Since the exhaust valve opening period of the cylinder increases by 5 °, the first cylinder 6₁Increase the maximum valve lift of the exhaust valve of the second cylinder 6₂Reduce the maximum valve lift of the exhaust valve. Similarly, the first cylinder 6₁The intake valve opening period of the cylinder increases by 5 °, and the second cylinder 6₂Since the intake valve opening period of the cylinder is reduced by 5 °, the first cylinder 6₁Reducing the maximum valve lift of the intake valve of the second cylinder 6₂Increase the maximum valve lift of the intake valve. The setting of the valve lift is, for example, the first cylinder 6₁And the second cylinder 6₂The valve lift time areas can be equalized. The time area is an area of a hatched portion below the valve lift line shown in FIG. 20, and can be calculated by ∫Y (t) dt obtained by integrating the valve lift Y (t) over the valve opening time.
[0049]
As a result, in the embodiment, the first cylinder 6₁The maximum valve lift of the exhaust valve increases to 7.8 mm and the second cylinder 6₂The maximum valve lift of the exhaust valve is reduced to 7.2 mm and the first cylinder 6₁The maximum valve lift of the intake valve is reduced to 7.7 mm and the second cylinder 6₂The maximum valve lift of the intake valve increases to 8.3 mm. Thus, the first cylinder 6₁And the second cylinder 6₂Variation in output between the two is eliminated, and undesirable torque fluctuations are prevented.
[0050]
In the above embodiment, the simple time area method is adopted when determining the valve lift of the intake valve and the exhaust valve. However, by using the total valve effective opening area, the occurrence of torque fluctuation can be more reliably prevented. Can do. The total valve effective opening area can be calculated as follows. That is, the valve effective opening area Z (t) is obtained from the valve lift Y (t) based on the graph shown in FIG. 21, and this valve effective opening area Z (t) is integrated over the valve opening time ∫Z (t ) Dt can be calculated.
[0051]
Next, a second embodiment of the present invention in which a variable valve lift / timing mechanism is employed in the valve operating device will be described with reference to FIGS.
[0052]
22 to 24 show the first cylinder 6.₁1 shows a valve operating apparatus. The camshaft 13 is provided with two exhaust cams 39, 39, two low-speed intake cams 34L, 34L located inside them, and one high-speed intake cam 34H located inside them. It is done. First rocker shaft 31₁There are two first rocker arms 37₁, 37₁And two low-speed first swing arms 32L located inside them₁, 32L₁And one high-speed first swing arm 32H located inside thereof₁Are pivotably supported.
[0053]
Each first rocker arm 37₁The roller 38 provided at one end abuts on the exhaust cam 39 and swings, thereby pressing the stem 41 of the exhaust valve 22 at the other end to drive the exhaust valve 22 to open and close. First low speed swing arm 32L₁Swings by causing the slipper 60 provided on the upper surface of the intermediate portion to abut against the low-speed intake cam 34L, and its tip abuts against the stem 36 of the intake valve 21. First swing arm 32H for high speed₁, The slipper 61 provided on the upper surface of one end thereof is brought into contact with the high-speed intake cam 34H, and the lower surface of one end thereof is brought into contact with the lost motion spring 62. Two low speed first swing arms 32L₁, 32L₁And one high-speed first swing arm 32H₁Can be coupled / separated from each other by two pistons 63 and 64 that can move in the axial direction by hydraulic pressure.
[0054]
Thus, when the engine E is operating at low speed, the two first swing arms 32L for low speed are moved by moving the two pistons 63, 64 to the inoperative position.₁, 32L₁And one high-speed first swing arm 32H₁And disconnect. As a result, each intake valve 21 is driven by a low-speed intake cam 34L with a small lift amount, and the valve lift is reduced and the valve opening time is also shortened. At this time, the first high-speed swing arm 32H contacting the high-speed intake cam 34H₁Moves idly while expanding and contracting the lost motion spring 62.
[0055]
On the other hand, when the engine E is operating at high speed, the two first swing arms 32L for low speed are moved by moving the two pistons 63, 64 to the operating position.₁, 32L₁And one high-speed first swing arm 32H₁Are combined together. As a result, each intake valve 21 is driven by a high-speed intake cam 34H having a large lift amount, the valve lift becomes large, and the valve opening time becomes long. At this time, each low speed intake cam 34L is connected to the low speed first swing arm 32L.₁It moves away from the air.
[0056]
25 to 27 show the second cylinder 6₂1 shows a valve operating apparatus. The camshaft 13 is provided with two exhaust cams 39, 39, two low-speed intake cams 34L, 34L located inside them, and one high-speed intake cam 34H located inside them. It is done. Second rocker shaft 31₂There are two second swing arms 32₂, 32₂And two low-speed second rocker arms 37L located inside them₂And one second high-speed rocker arm 37H located inside₂Are pivotably supported.
[0057]
Each second swing arm 32₂The slipper 65 provided in the intermediate portion abuts on the exhaust cam 39 and swings, thereby pressing the stem 41 of the exhaust valve 22 at the other end to drive the exhaust valve 22 to open and close. Second rocker arm 37L for each low speed₂Swings by causing the slipper 66 provided at one end thereof to abut against the low-speed intake cam 34L, and its tip abuts against the stem 36 of the intake valve 21. High speed second rocker arm 37H₂, The slipper 67 provided at one end thereof is brought into contact with the high-speed intake cam 34 </ b> H, and the other end is brought into contact with the lost motion spring 68. Two low-speed second rocker arms 37L₂, 37L₂And one high-speed second rocker arm 37H₂Can be coupled / separated from each other by two pistons 69 and 70 that can move in the axial direction hydraulically.
[0058]
Thus, when the engine E is operating at a low speed, the two low-speed second rocker arms 37L are moved by moving the two pistons 69 and 70 to the inoperative position.₂, 37L₂And one high-speed second rocker arm 37H₂And disconnect. As a result, each intake valve 21 is driven by a low-speed intake cam 34L with a small lift amount, and the valve lift is reduced and the valve opening time is also shortened. At this time, the second high-speed rocker arm 37H contacting the high-speed intake cam 34H₂Moves idly while expanding and contracting the lost motion spring 68.
[0059]
On the other hand, when the engine E operates at high speed, the two low-speed second rocker arms 37L are moved by moving the two pistons 69 and 70 to the operating positions.₂, 37L₂And one high-speed second rocker arm 37H₂Are combined together. As a result, each intake valve 21 is driven by a high-speed intake cam 34H having a large lift amount, the valve lift becomes large, and the valve opening time becomes long. At this time, each low speed intake cam 34L is connected to the low speed second rocker arm 37L.₂It moves away from the air.
[0060]
Next, a third embodiment of the present invention in which another variable valve lift / timing mechanism is employed in the valve operating device will be described with reference to FIGS.
[0061]
28 to 30 show the first cylinder 6.₁1 shows a valve operating apparatus. The camshaft 13 is provided with one exhaust cam 39, and a low-speed intake cam 34L and a high-speed intake cam 34H located on both sides thereof. First rocker shaft 31₁The first rocker arm 37 having a bifurcated tip₁And the first low-speed swing arm 32L located on both sides thereof₁And high-speed first swing arm 32H₁Are pivotably supported.
[0062]
First rocker arm 37₁When the roller 38 provided at one end abuts on the exhaust cam 39 and swings, the stem 41 of each exhaust valve 22 is pressed at the other end of the fork to open and close the exhaust valve 22. First swing arm 32L for low speed₁Swings by causing a slipper 71 provided on the upper surface of the intermediate portion to abut against the low-speed intake cam 34L, and its tip abuts against the stem 36 of one intake valve 21. First swing arm 32H for high speed₁The slipper 72 provided on the upper surface of the intermediate portion contacts the high-speed intake cam 34H, and the tip thereof contacts the stem 36 of the other intake valve 21. First swing arm 32L for low speed₁And high-speed first swing arm 32H₁Can be coupled / separated from each other by a piston 73 that is movable in the axial direction by hydraulic pressure.
[0063]
Thus, when the engine E is operating at low speed, the first swing arm 32L for low speed is moved by moving the piston 73 to the inoperative position.₁And high-speed first swing arm 32H₁And disconnect. As a result, one of the intake valves 21 is driven by the low-speed intake cam 34L with a small lift amount, and the valve lift is reduced and the valve opening time is also shortened. The other intake valve 21 is driven by a high-speed intake cam 34H having a large lift amount, and the valve lift becomes large and the valve opening time becomes long.
[0064]
On the other hand, when the engine E is operating at high speed, the low-speed first swing arm 32L is moved by moving the piston 73 to the operating position.₁And high-speed first swing arm 32H₁Are combined together. As a result, both the intake valves 21 and 21 are driven by the high-speed intake cam 34H having a large lift amount, the valve lift becomes large, and the valve opening time becomes long. At this time, the low speed intake cam 34L is connected to the low speed first swing arm 32L.₁It moves away from the air.
[0065]
31 to 33 show the second cylinder 6₂1 shows a valve operating apparatus. The camshaft 13 is provided with two exhaust cams 39, 39, and a low-speed intake cam 34L and a high-speed intake cam 34H located inside thereof. Second rocker shaft 31₂Two second swing arms 32₂, 32₂And the second low-speed rocker arm 37L located inside them₂And high-speed second rocker arm 37H₂Are pivotably supported.
[0066]
Each second swing arm 32₂When the roller 74 provided on the upper surface of the intermediate portion abuts on the exhaust cam 39 and swings, the stem 41 of the exhaust valve 22 is pressed at its tip to drive the exhaust valve 22 to open and close. Low speed second rocker arm 37L₂Swings by causing the slipper 75 provided at one end thereof to abut against the low-speed intake cam 34L and the other end contacts the stem 36 of one intake valve 21. High speed second rocker arm 37H₂The roller 38 provided at one end contacts the high-speed intake cam 34H, and the other end contacts the stem 36 of the other intake valve 21. First swing arm 32L for low speed₁And high-speed first swing arm 32H₁Can be coupled / separated from each other by a piston 76 that can move in the axial direction hydraulically.
[0067]
Thus, when the engine E is operating at a low speed, the second rocker arm 37L for low speed is moved by moving the piston 76 to the inoperative position.₂And second high-speed rocker arm 37H₂And disconnect. As a result, one of the intake valves 21 is driven by the low-speed intake cam 34L with a small lift amount, and the valve lift is reduced and the valve opening time is also shortened. The other intake valve 21 is driven by a high-speed intake cam 34H having a large lift amount, and the valve lift becomes large and the valve opening time becomes long.
[0068]
On the other hand, when the engine E is operating at high speed, the low speed second rocker arm 37L is moved by moving the piston 76 to the operating position.₂And second high-speed rocker arm 37H₁Are combined together. As a result, both the intake valves 21 and 21 are driven by the high-speed intake cam 34H having a large lift amount, the valve lift becomes large, and the valve opening time becomes long. At this time, the low speed intake cam 34L is connected to the low speed second rocker arm 37L.₁It moves away from the air.
[0069]
As mentioned above, although the Example of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.
[0072]
【The invention's effect】
  As aboveClaim1According to the invention described inA first cylinder having an axis that is offset to the crankshaft rotation direction advance side with respect to the crankshaft axis; a second cylinder having an axis that is offset to the crankshaft rotation direction delay side with respect to the crankshaft axis; A first piston slidably fitted to the cylinder, a second piston slidably fitted to the second cylinder, a first connecting rod for connecting the first piston to the crankshaft, and a crank for the second piston With a second connecting rod connected to the shaftIn the offset piston engine, the first piston pin that pivotally supports the first piston on the small end of the first connecting rod is offset from the center of the first piston toward the crankshaft rotation direction, and the second piston is Since the second piston pin pivotally supported on the small end of the connecting rod is offset toward the crankshaft rotation direction delay side with respect to the center of the second piston, the connecting rod is used in the compression stroke or the expansion stroke in which a large compressive force acts on the connecting rod. When the piston is greatly inclined, a moment around the piston pin is applied to the first and second pistons by the compressive force so that the skirt portion of the piston side wall is further pressed against the cylinder side wall, and the skirt portion having low rigidity is deformed. Dispersing the thrust force It can be. In this way, the thrust force is distributed and received at the skirt portion of the piston side wall, which is sufficiently supplied with lubricating oil at a relatively low temperature, thereby reliably preventing seizure between the piston and the cylinder and improving seizure resistance. At the same time, fuel consumption can be reduced by reducing the frictional force.
[0073]
  Moreover,The closing timing of the intake valve of the first cylinder is delayed from the closing timing of the intake valve of the second cylinder.In addition, the opening timing of the exhaust valve of the first cylinder is delayed from the opening timing of the exhaust valve of the second cylinder.BecauseOf the structureDifference in intake stroke length between the first and second cylinders in an offset piston engineAnd exhaust stroke length differenceThe,Intake valveClosing timing and exhaust valveCompensation is performed by setting the valve opening timing, and the output difference between the first and second cylinders can be reduced to avoid the occurrence of torque fluctuation.
[0074]
  And claims2According to the invention described in the above, the valve lift of the intake valve of the first cylinder is set smaller than the valve lift of the intake valve of the second cylinder.In addition, the valve lift of the exhaust valve of the first cylinder is set larger than the valve lift of the exhaust valve of the second cylinder.As a result, the intake valves of the first and second cylindersAnd each of the exhaust valveThe difference in the valve lift time area or the total valve effective opening area can be reduced to further reduce the output difference between the first and second cylinders, and the occurrence of torque fluctuation can be avoided more effectively.
  According to the invention described in claim 3, since the plurality of first and second cylinders are arranged in a staggered manner in the same cylinder block as viewed from the cylinder head, they are arranged in the axial direction of the engine crankshaft. The dimension can be shortened compared to a plurality of cylinders arranged in series, and the dimension in the direction orthogonal to the crankshaft axis of the engine can be reduced compared to a cylinder arranged in a V shape. it can.
[Brief description of the drawings]
FIG. 1 is a front view of an engine (viewed in one direction arrow in FIG. 2).
2 is a sectional view taken along line 2-2 of FIG.
3 is a sectional view taken along line 3-3 in FIG.
4 is a sectional view taken along line 4-4 of FIG.
5 is a cross-sectional view taken along line 5-5 of FIG.
6 is a sectional view taken along line 6-6 in FIG.
7 is a cross-sectional view taken along line 7-7 in FIG.
8 is an enlarged sectional view taken along line 8-8 in FIG.
9 is a cross-sectional view taken along line 9-9 of FIG.
10 is a sectional view taken along line 10-10 in FIG.
11 is a perspective view of a cylinder block taken along line 11-11 in FIG.
FIG. 12 is a perspective view of a cylinder block.
FIG. 13 is a view showing a modification of the breather chamber
FIG. 14 is a diagram illustrating the operation of the first cylinder
FIG. 15 is an explanatory diagram of the operation of the second cylinder.
FIG. 16 is a graph showing the thrust force of a piston
FIG. 17 is a diagram for explaining the crank angle of each stroke of the engine
FIG. 18 is a diagram showing a phase of a crankpin corresponding to each cylinder.
FIG. 19 is a graph showing valve timing.
FIG. 20 is an explanatory diagram of a valve lift time area calculation method.
FIG. 21 is a diagram showing a relationship between a valve lift and a valve effective opening area.
FIG. 22 is a plan view of the valve operating apparatus for the first cylinder according to the second embodiment.
23 is a cross-sectional view taken along line 23-23 in FIG.
24 is a cross-sectional view taken along line 24-24 in FIG.
FIG. 25 is a plan view of the valve operating device for the second cylinder according to the second embodiment.
26 is a cross-sectional view taken along the line 26-26 in FIG.
27 is a sectional view taken along line 27-27 in FIG.
FIG. 28 is a plan view of the valve operating apparatus for the first cylinder according to the third embodiment.
29 is a cross-sectional view taken along line 29-29 in FIG. 28.
30 is a cross-sectional view taken along line 30-30 in FIG.
FIG. 31 is a plan view of a valve operating apparatus for a second cylinder according to a third embodiment.
32 is a sectional view taken along line 32-32 in FIG. 31;
33 is a cross-sectional view taken along line 33-33 of FIG.
[Explanation of symbols]
1 Crankshaft
6₁        First cylinder (cylinder)
6₂        Second cylinder (cylinder)
7₁        1st piston (piston)
7₂        Second piston (piston)
8₁        First connecting rod (connecting rod)
8₂        Second connecting rod (connecting rod)
9₁        1st piston pin (piston pin)
9₂        Second piston pin (piston pin)
21 Intake valve
Lc₁      1st cylinder axis (axis)
Lc₂      Second cylinder axis (axis)
Ls Crankshaft axis (axis)

Claims (3)

Click the crankshafts (1), the axis of the crankshaft (1) and the axis that is offset to the crankshaft rotation direction leading side with respect to (Ls) (Lc ₁₎ the first cylinder having a (6 _1), a crankshaft (1 ) Is slidably fitted to the second cylinder (6 ₂ ) having an axis (Lc ₂ ) offset to the crankshaft rotation direction delay side with respect to the axis (Ls) of the first cylinder (6 ₁ ). A first piston (7 ₁ ), a second piston (7 ₂ ) slidably fitted to a second cylinder (6 ₂ ), and a first piston (7 ₁ ) connected to the crankshaft (1) In an offset piston engine comprising a connecting rod (8 ₁ ) and a second connecting rod (8 ₂ ) connecting the second piston (7) to the crankshaft (1),
The first piston pin (9 ₁ ) pivotally supporting the first piston (7 ₁ ) on the small end of the first connecting rod (8 ₁ ) is rotated in the crankshaft rotation direction with respect to the center of the first piston (7 ₁ ). with offsetting leading side, a second piston (6 ₂₎ a second piston pin (9 ₂₎ pivotally supporting the small end of the second connecting rod _(82), the center of the second piston (7 ₂₎ On the other hand, the crankshaft rotation direction is offset to the delay side ,
With delayed than the valve closing timing of the intake valve (21) of the first cylinder (6 ₁₎ closing timing of the second cylinder of the intake valve (21) (6 _2), the first exhaust valve of the cylinder ₍₆₁₎ An offset piston engine characterized in that the opening timing of (22) is delayed from the opening timing of the exhaust valve (22) of the second cylinder (6 ₂ ) . While smaller than the valve lift of the first cylinder (6 ₁₎ second cylinder valve lift of the intake valve (21) of the intake valve (21) (6 _2), the first exhaust valve of the cylinder ₍₆₁₎ characterized by being larger than the valve lift of the exhaust valve of the valve lift (22) the second cylinder (6 ₂₎ (22), the offset piston engine according to claim 1, wherein. In the same cylinder block (2), a plurality of first and second cylinders (6 ₁ , 6 ₂ The offset piston engine according to claim 1 or 2, characterized in that they are arranged in a staggered manner as viewed from the cylinder head (3).

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