JPH11324602A - Reciprocating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a reciprocating machine by forming a notch to a cylinder for reducing the closest distance between the external wall surface of the boss part of a piston pin hole and that of a crankshaft, and for preventing a connecting rod from interfering with a large end part, and by providing a counterweight to a crankshaft in the outside of a crankcase for reducing unbalance inertia force caused by the motion of the piston crank system. SOLUTION: A notch 13 having the width of a half of the internal diameter of a cylinder or less is formed in the cylinder, which makes the closest distance between the exterior wall surface of a boss part 5 of a piston pin hole and that of a crankshaft 10 to be 40 percent of the internal diameter of the cylinder or less, and prevents a connecting rod 7 from interfering with a large end part. A crank arm 9 is formed in a size so as not to interfere with the part of the cylinder which is to move slidably on the edge part of a piston skirt. A counterweight is provided to a crankshaft in the outside of a crankcase 2 for reducing the unbalance inertia force caused by the motion of the piston-crank system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating machine having a piston-crank mechanism and having a suction valve and a discharge valve, and the closest approach between a boss outer wall surface of a piston pin hole and a crank shaft outer wall surface. It is related to miniaturization with a much smaller distance than before.

[0002]

2. Description of the Related Art Generally, a reciprocating machine such as a four-cycle engine and a gas compressor is provided with a counterweight in a crank chamber to reduce unbalanced inertial force due to movement of a piston-crank mechanism. In order to achieve such miniaturization of the reciprocating machine, it is desirable to reduce the center-to-center distance between the piston pin and the crankshaft at the bottom dead center of the piston, but first, the piston and the counterweight interfere with each other. Second, there were problems such as interference between the large end of the connecting rod and the cylinder, and the miniaturization was limited.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the closest approach distance between the outer wall surface of the boss portion of the piston pin hole and the outer wall surface of the crankshaft, and to prevent interference with the large end of the connecting rod. By forming a notch in the cylinder and providing a counterweight on the crankshaft outside the crankcase to reduce the unbalanced inertial force generated by the movement of the piston-crank mechanism, the reciprocating machine can be downsized. is there.

[0004]

According to the present invention, the closest approach distance between the outer wall surface of the boss portion of the piston pin hole and the outer wall surface of the crankshaft is set to 0.4 times or less of the cylinder inner diameter, and interference with the large end of the connecting rod is made. A notch having a width of not more than 0.5 times the inner diameter of the cylinder is formed in the cylinder, and the crank arm is shaped so as not to interfere with the piston skirt end of the cylinder and the part to be slid; A counterweight is provided on the crankshaft outside the crankcase to reduce the unbalanced inertial force generated by the movement of the piston-crank mechanism.

[0005]

FIG. 1 shows an embodiment of a reciprocating machine according to the present invention. First, FIG. 1A shows a four-stroke engine which is a kind of reciprocating machine (the figure shows an Otto engine, but a diesel engine). A crankshaft 10 having a crank arm 9 for firmly supporting the crankpin 8, and a connecting rod 7 for connecting the crankpin 8 to the piston pin 4, and sucking a fluid (air-fuel mixture) into the cylinder 1. And a discharge valve 12 for discharging fluid (burned gas) in the cylinder. As shown in FIG. 2A, the intake valve 11 is opened and closed by a cam 17 which rotates at a speed reduced to half the rotation of the crankshaft 10 by a gear, a lifter 18 driven by the cam 17, a push rod 19, and a rocker arm 20. (The discharge valve 12 is also driven). In the suction stroke in which the suction valve 11 is opened, the air-fuel mixture generated by the carburetor or the like is sucked into the cylinder 1. This air-fuel mixture is compressed in a compression stroke in which the suction valve 11 and the discharge valve 12 are closed.
It is ignited near top dead center and burns, generating explosive power. The burned gas that has finished its work after the expansion stroke is discharged by the piston 3 when the discharge valve 12 is opened (discharge stroke), thus generating power. The reciprocating machine is divided along the line AA 'and fastened by bolts. In the present invention, FIG.
As shown in (b), the closest approach distance l (the distance at the bottom dead center) between the outer wall surface of the boss portion of the piston pin hole and the outer wall surface of the crankshaft is made extremely small to pursue miniaturization. In other words, generally, assuming that the cylinder inner diameter is D, the piston skirt height L ≒ 0.5 · D, and the boss diameter of the piston pin hole = 0.38 ·
D (internal combustion engine, Vol16, No19
3, extra edition, p30), therefore, allowance S = D = 4 to prevent interference between the end of the piston skirt and the outer wall of the crankshaft.
If S = 0.05 · D when 2 mm in the 0 mm class, 1 = L−0.38 · D / 2 + S = 0.36 ·
D. Actually, since there is a width of L = (0.5 ± 0.1) · D, l = 0.4 · D. In the present invention, the value of l is set to 0.1 in the sense of a general limit within a range where there is no interference between the end of the piston skirt and the outer wall surface of the crankshaft.
The feature is that it is set to 4 · D or less. Fig. 1 (a)
In the embodiment of the present invention, the present invention is pursued to the utmost, and a notch 6 is formed at the skirt end of the piston 3 to allow the crankshaft 10 to bite (there is no interference between the two by the notch 6). The closest approach distance 1 between the outer wall surface of the boss portion of the pin hole and the outer wall surface of the crankshaft is extremely small (for example, 2 mm) (see FIG. 2A showing a cross-sectional view taken along the line BB '). Dead center position). A notch 13 for preventing interference with the large end of the connecting rod 7 is formed in the cylinder 1.
As shown in FIG. 2 (c) showing a cross section taken along the line -A ', both ends of the connecting rod large end require a gap of about 2 mm in the notch 13, while the width W of the notch 13 is excessive. The contact area between the piston skirt and the cylinder is reduced,
There is a risk of hammering. In view of such circumstances, in the present invention, the width W of the notch 13 is set to 0.5 times or less of the inner diameter of the cylinder (more preferably 0.4 times or less). The crank arm 9 is shaped so as not to interfere with the piston skirt end of the cylinder 1 and the part to be slid (if the structure allows the interference between the piston skirt and the cylinder, the piston skirt and the cylinder may be connected at the bottom dead center position). The contact area is reduced, causing vibration and tapping noise). In the present invention, since the crankshaft 10 and the piston 3 are very close to each other and the counterweight cannot be mounted on the opposite side of the crank arm as in the conventional case (although it can be mounted if the counterweight is extremely small), FIG. 2 (a), counterweights 22 and 24 for reducing unbalanced inertial force generated by the movement of the piston-crank mechanism are provided on the crankshaft outside the crankcase 2. Generally, crankshaft 10
Cooling fan 21 and recoil pulley 23
Therefore, the counterweights 22 and 24 are directly fixed to each other or built in. Returning to FIG. 1A again, the connecting rod 7 is divided into two parts at the large end in terms of assembly to the crankpin 8, and each is firmly fastened by bolts. In the present invention, the connecting rod length (large end Since the ratio between the center radius of the portion and the small end portion) and the crank radius is small, a connecting rod made of a light alloy such as an Al alloy is desirable because it is necessary to reduce the reciprocating inertial weight and suppress the secondary vibration. Each bearing part can also use a rolling bearing. As for the method of supporting the crankshaft, it is conceivable to use a cantilever as shown in FIG. 2B. In this case, the connecting rod 7 is extremely easy to assemble because there is no crank arm on one side, and the large end Need not be divided into two, and may be integrated. Fig. 2 shows a cross section taken along the line CC '.
As shown in (d), as described above, the notch 13 having a width of 0.5 times or less the inner diameter of the cylinder for preventing interference with the large end of the connecting rod 7 is formed. Reference numeral 25 denotes a counterweight for reducing the unbalanced inertial force generated by the movement of the piston-crank mechanism. However, since the generation of a couple moment due to the center distance h between the piston 3 and the counterweight 25 is inevitable, as shown in FIG.
One of the counterweight (f ₂ the inertia force this occurs
It is desirable to have f ₁ is the piston - inertia force crank mechanism occurs, f ₃ is the inertia force of the counterweight 25, since these counterbalancing way is well known, will be omitted. Next, in FIG. 2C, if there is some reason, a configuration in which the portion of the crank arm 9 near the crankpin is fitted into the notch 13 according to the rotation as shown in FIG. The part is used for positioning the connecting rod 7). Also, in FIG. 2 (c), a part of the crankpin 8 extends beyond the portion corresponding to the cylinder inner peripheral surface as shown in FIG. 3 (b) while keeping the shortest distance r from the crankshaft center to the crankpin outer peripheral surface constant. If it is configured to rotate around the crankshaft (increase the diameter of the crankpin), the center-to-center distance (crank radius) between the crankpin 8 and the crankshaft 10 increases. Can be done. The above is similarly applied to FIG. In the present invention, if the notch 26 for preventing interference with the crankshaft is formed in the boss portion 5 of the piston pin hole as shown in FIG. Since the distance can be further reduced, the size will be further reduced. FIG. 4 shows the axial center of the crankshaft 10 eccentric from the axial center of the cylinder (illustrated schematically). By eccentrically moving to the thrust side as shown in the figure, the thrust acting on the side of the piston is reduced, resulting in wear and friction. Power can be reduced. This is particularly effective when the length of the connecting rod is short as in the present invention. As described above, the reciprocating machine has been described as a four-cycle engine in the present invention. However, it is also conceivable that the reciprocating machine is a compressor (for example, an air compressor) that pressurizes a fluid.
Shown in In the descending stroke of the piston 3, the suction valve 14 (reed valve type) is opened to suck the fluid into the cylinder 1, and in the rising stroke of the piston 3, the discharge valve 15 (reed valve type) is opened to discharge the pressurized fluid. . In FIG. 1 (c), the present invention is applied in exactly the same manner as in FIG. 1 (a), and therefore the description is omitted, but it goes without saying that the embodiments described in FIGS. No. It should be noted that the present invention is also applied to a multi-cylinder reciprocating machine, and a series type, a V type, and a horizontally opposed type can be considered.

[0006]

According to the present invention, the closest distance l between the outer wall surface of the boss portion of the piston pin hole and the outer wall surface of the crankshaft is set to 0.4 times or less the inner diameter of the cylinder. Conventionally, with such a configuration, the first problem is that the large end of the connecting rod interferes with the cylinder, and the second is that the counterweight for reducing the unbalanced inertial force interferes with the piston. The construction of the invention was considered impossible. No, it is better to consider that this configuration of the invention was in the blind spot from the beginning. On the other hand, in the present invention, a drastic idea was solved, and the first point was solved by forming a notch 13 in the cylinder to prevent interference with the large end of the connecting rod 7 (in this case, the notch 13 To prevent interference between them with a simple idea that does not form, the crank radius must be made very small, which is far from practical use.) That is, the notch 13 is formed to increase the crank radius. Moreover, the notch 1
Since the width of No. 3 is designed to be 0.5 times or less of the inner diameter of the cylinder, the piston skirt portion comes into contact with the cylinder over a wide area, and the generation of vibration and noise is low. Regarding the second point, a counterweight for reducing the unbalanced inertia force is provided on the crankshaft outside the crankcase 2 without being bound by the conventional concept. 1 (a) has a piston diameter of 40 mm, a crank radius of 24 mm, and a displacement of 30 cc.
The piston diameter is 5 mm larger while the overall height is reduced by 35 mm as compared with the conventional one having the same displacement. As described above, according to the present invention, the reciprocating machine can be significantly reduced in size.

[Brief description of the drawings]

FIG. 1 is a sectional view of a reciprocating machine according to the present invention.

FIG. 2 is a diagram of a reciprocating machine according to the invention, in particular a four-stroke engine.

FIG. 3 is a schematic view of each embodiment of the present invention.

FIG. 4 is a schematic diagram of a reciprocating machine in which a crankshaft is eccentric.

[Explanation of symbols]

1 is a cylinder, 2 is a crank chamber, 3 is a piston, 4 is a piston pin, 5 is a boss of a piston pin hole, 6 is a cutout, 7 is a connecting rod, 8 is a crank pin, 9 is a crank arm, and 10 is a crank. Shaft, 11 is a suction valve, 12 is a discharge valve,
13 is a notch, 14 is a suction valve, 15 is a discharge valve, 16 is a main bearing, 17 is a cam, 18 is a lifter, 19 is a push rod, 20 is a rocker arm, 21 is a cooling fan, 2
2, 24 and 25 are counterweights, 23 is a recoil pulley, and 26 is a notch.

Claims (7)

[Claims] 1. A crankshaft having a crank arm for firmly supporting a crankpin, a connecting rod connecting the crankpin and a piston pin, and a suction valve for sucking fluid into the cylinder and discharging fluid from the cylinder. In a reciprocating machine having a discharge valve, the closest distance between the outer wall surface of the boss portion of the piston pin hole and the outer wall surface of the crankshaft is set to 0.4 times or less the inner diameter of the cylinder, and interference with the large end of the connecting rod is made. A notch having a width of not more than 0.5 times the cylinder inner diameter is formed in the cylinder, and the crank arm is shaped so as not to interfere with the piston skirt end of the cylinder and the part to be slid;
Further, a reciprocating machine characterized in that a counterweight for reducing unbalanced inertial force generated by movement of a piston-crank mechanism is provided on a crankshaft outside a crankcase. 2. The reciprocating machine according to claim 1, wherein the reciprocating machine is a compressor that pressurizes and discharges fluid in a cylinder from a discharge valve. 3. The reciprocating machine according to claim 1, wherein the reciprocating machine is a four-cycle engine that performs each of suction, compression, expansion, and discharge strokes. 4. The reciprocating machine according to claim 1, wherein a notch is formed at an end of the skirt of the piston to allow the crankshaft to bite. 5. The reciprocating machine according to claim 4, wherein a notch for preventing interference with the crankshaft is formed in the boss portion of the piston pin hole. 6. The crank radius is increased by configuring a part of a crank pin to rotate around a crank shaft beyond a part corresponding to an inner peripheral surface of a cylinder.
The reciprocating machine according to any one of the above. 7. The reciprocating machine according to claim 1, wherein the axis of the crankshaft is decentered from the axis of the cylinder.