GB2058223A

GB2058223A - Balancing device for reciprocating machine

Info

Publication number: GB2058223A
Application number: GB8027679A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1979-08-27
Filing date: 1980-08-27
Publication date: 1981-04-08
Also published as: GB2058223B; DE3031744A1; JPS5635935U; FR2464409B1; FR2464409A1

Abstract

The balancing device includes a crankshaft (9), counterweights (11) for balancing the rotation movements of the crankshaft, and connecting rods (2) connecting the crankshaft with respective reciprocating members (1). A stem-like extension (7) is fixed to and extends from one end of each connecting rod in a direction opposite to the connecting rod. A journal (4) is rotatably mounted on the outer end of each stem-like extension and each journal is linked to another journal by a link (8). A balance weight (6) is fixed to each link for balancing any unbalanced force due to the reciprocating masses of the machine. <IMAGE>

Description

SPECIFICATION Balancing device for reciprocating machine BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a balancing device for a reciprocating machine such as an engine, pump, or compressor.

2. Description of the Prior Art In a prior art four-cylinder in-line, four-cycle engine for an automative vehicle, the unbalanced force Fm of the reciprocating masses in the vertical direction, or the axial direction 10 of each cylinder, can be theoretically indicated by the following equation:

where: C2 = 1/# + 1/4#3 + ....; 1 3 C4=- 4A3 16.

m = reciprocating mass per cylinder; r = crank radius; w = crankshaft angular velocity; 0 = crank angle from the top dead center of a second or third crank; I = effective length of each connecting rod, that is, the distance between the center lines of the piston wrist pins and crankshaft rod iournals; and A =I/r, that is, the connecting rod ratio which is normally 2 to 4.

The majority of the unbalanced forces causing engine vibration are considered to be the secondary components thereof hereinafter called F2m where n is 1 in the above-stated equation (1).

For example, in engines of 2,000 c.c.

displacement, the unbalanced force F2,,, is approximately 1,200 to 1,500 Kg at an engine speed of 6,000 r.p.m. Thus, engine vibration and noise results.

In order to balance the unbalanced force F2,,,, a prior art balancing device (shown in Fig. 1) for a reciprocating engine has a pair of balancers 12, 12' which are symmetric with respect to the axis 10 of each engine cylinder, as shown in Fig. 1.

These balancers 12, 12' are designed to rotate in opposite directions at twice the rotation velocity of the crankshaft.

In such a prior art balancing device, a pair of shafts 13, 13' are also necessary for supporting the balancers 12, 12'. Also, a power transmitting means such as a wheel, sprocket or chain mechanism must be arranged between the crankshaft and each balancer shaft so that the balancers 12, 12' can move to balance the unbalanced force. A further defect of the prior art balancing device is that only the secondary components of the unbalanced force can.be balanced in the vertical direction so that it cannot be perfectly balanced.

SUMMARY OF THE INVENTION In one aspect, the invention provides a balancing device for a reciprocating machine, comprising: a crankshaft; a plurality of counter weights for balancing the rotation movement of the crankshaft; first, second, third and fourth connecting rods joined at their big ends to the predetermined portions of the crankshaft; the improvement comprising: first, second, third and fourth stem-like extensions fixedly extending from the big ends of the first, second, third and fpurth connecting rods in the opposite direction thereto, respectively; first, second, third and fourth journals rotatably mounted to the outer ends of said first, second, third and fourth stem-like extensions, respectively; a first link for linking the first and second journals; a second link for linking the third and fourth journals; and first and second balance weights fixed to said first and second links, respectively, for balancing any unbalanced force of the reciprocating masses of the engine.

In another aspect, the invention provides a device for balancing the reciprocating movements of a reciprocating machine, comprising: a crankshaft rotatably provided relative to the reciprocating machine; a plurality of reciprocating members; a plurality of connecting rods for connecting the crankshaft with the respective reciprocating members; a plurality of extensions each extending from one end of a respective connecting rod in the opposite direction thereof; a plurality of journals each rotatably connected to an outer end of a respective extension; mean for linking one of the journals to an adjacent journal; and means fixed to the linking means for balancing any unbalanced force of the reciprocating machine due to the reciprocating masses thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be more particularly described with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic view showing a prior art balancing device for a four-cylinder in-line, four-cycle engine; Fig. 2A is a perspective diagrammatic view showing a balancing device for a four-cylinder inline, four-cycle engine according to a preferred embodiment of the present invention; and Fig. 2B is a diagrammatic view of the balancing device shown in Fig. 2A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Figs. 2A and 2B, there is shown a device for balancing a four-cylinder inline, four-cycle engine according to a preferred embodiment of the present invention. First, second, third and fourth pistons 1 to 1"' are connected to the small ends of first, second, third and fourth connecting rods 2 to 2"', respectively.

The other ends or big ends 3 to 3"' of those connecting rods are connected to respective predetermined journals of a crankshaft 9 in a wellknown manner.

First, second, third and fourth extensions 7 to 7"', which are preferably formed in a stem shape, extend fixedly or integrally from the big ends 3 to 3"' of the connecting rods 2 to 2'a, respectively, in the opposite direction thereto as shown in Fig. 2A in alignment with the axis of each connecting rod.

The outer ends of the extensions 7 to 7"' are fixed to respective bearings 4 to 4"' which rotatably support first, second, third and fourth journals 5 to 5"'. A first link 8 connects the first journal 5 with the second journal 5'. A second link 8' connects the third journal 5" with the fourth journal 51". It is preferable that a pair of adjacent journals and the link therefor are arranged in a Z-shape.

First and second balance weights 6, 6' are fixed at intermediate portions of the first and second links 8, 8', respectively. It is preferable that each balance weight is positioned at the center of each link. Those balance weights 6, 6' and links 8, 8' should be so arranged and formed that they do not interfere with the crankshaft 9 when it rotates.

In addition, first, second, third and fourth counter weights 11 to 11"' are provided on predetermined portions of the crankshaft 9 for balancing the rotational movement of the crankshaft.

In operation, when the crankshaft 9 rotates once, the balance weights 6, 6' reciprocate twice substantially in the vertical direction. If the masses of the balance weights 6, 6' are properly set, the unbalanced force due to the reciprocating balance weights can be used to balance the unbalanced force due to the reciprocating masses of the engine.

Referring to Fig. 2S, how to set the mass of the balance weights 6, 6' will be explained: The unbalanced force Fm of the engine assembly due to the reciprocating masses thereof can be indicated by the above-stated equation (1), that is:

where: 1 1 C2= + A 4A3 1 3 C4=- . .; 4A3 16;15 m = reciprocating mass per cylinder; r = crank radius; w = crankshaft angular velocity; 8 = crank angle from the top dead center of a second or third crank; I = effective length of each connecting rod, that is, the distance between the center lines of the piston wrist pins and crankshaft rod journals; and A =i/r, that is, the connecting rod ratio which is normally 2 to 4.

Because the balance weights 6, 6' reciprocate twice in the vertical direction when the crankshaft 9 rotates once, the unbalanced force FM due to the reciprocating balance weights can be indicated by the following equation:

L = effective length of the stem-like extension, that is, the distance between the center lines of each connecting rod crankshaft journal and each bearing connected thereto; and M = mass of the balance weights 6, 6'.

Accordingly, the balanced condition of the engine assembly and the balance weights can be shown as follows: F, + FM=O (3) The equation (3) can be changed to:

Consequently, the total balanced condition of the engine assembly and the balance weights can be obtained if the mass M of the balance weights 6, 6' is set as follows: M=2-m... (5) L In such a case, the unbalanced force F, due to the reciprocating masses of the engine assembly can be perfectly balanced with respect to not only the secondary components thereof but also all of the other components thereof.

According to the present invention, any unbalanced force of the engine assembly due to the reciprocating masses thereof can be perfectly balanced in the vertical direction although the engine body itself is not modified. It is unnecessary to provide a special mechanism for balancing the secondary components of the unbalanced force such as the balancers and power transmitting means used in the prior art balancing device. The balancing device according to the present invention can be designed to be simple in construction, while effectively eliminating the cause of engine vibration and engine noise.

Although a specific embodiment of the present invention has been shown and described in detail, the present invention may be practiced in other ways without departing from the scope thereof.

For instance, while in the illustrated embodiment a balancing device is applied only to a four-cylinder in-line, four-cycle automotive vehicle engine, it can be also applied to a two-cylinder, two-cycle engine as will as a general pump, compressor and other reciprocating machine.

Claims

1. A balancing device for a reciprocating machine, comprising: a crankshaft; a plurality of counter weights for balancing the rotation movement of the crankshaft; first, second, third and fourth connecting rods joined at their big ends to the predetermined portions of the crankshaft; the improvement comprising: first, second, third and fourth stem-like extensions fixedly extending from the big ends of the first, second, third and fourth connecting rods in the opposite direction thereto, respectively; first, second, third and fourth journals rotatably mounted to the outer ends of said first, second, third and fourth stem-like extensions, respectively; a first link for linking the first and second journals; a second link for linking the third and fourth journals; and first and second balance weights fixed to said first and second links, respectively, for balancing any unbalanced force of the reciprocating masses of the engine.

2. The balancing device of claim 1, wherein the mass of said balance weights is twice the product of the reciprocating mass multiplied by the ratio of connecting rod effective length to the effective length of respective said stem-like extensions,

3. The balancing device of claim 1 or claim 2, wherein the journals and the links are so arranged to form substantially a Z-shape.

4. The balancing device of any one of claims 1-3, wherein each stem-like extension is joined through a bearing to the link.

5. The balancing device of any one of claims 1-4 wherein each balance weight is fixed at an intermediate portion of the link so that when the crankshaft rotates once the balance weight reciprocates twice.

6. The balancing device of claim 5, wherein the balance weights reciprocate substantially in the vertical direction.

7. The balancing device of claim 5, or claim 6, wherein each balance weight is positioned at the center of each link.

8. The balancing device of any one of claims 1-7 wherein the balance weights and the links are formed in such a manner that they do not interfere with the crankshaft when it rotates.

9. A device for balancing the reciprocating movements of a reciprocating machine, comprising: a crankshaft rotatably provided relative to the reciprocating machine; a plurality of reciprocating members; a plurality of connecting rods for connecting the crankshaft with the respective reciprocating members; a plurality of extensions each extending from one end of a respective connecting rod in the opposite direction thereof; a plurality of journals each rotatably connected to an outer end of a respective extension; means for linking one of the journals to an adjacent journal; and means fixed to the linking means for balancing any unbalanced force of the reciprocating machine due to the reciprocating masses thereof.

10. The device of claim 9, wherein the mass of said balance weights is twice the product of the reciprocating mass multiplied by the ratio of connecting rod effective length to the effective length of respective said stem-like extensions.

11. A device for balancing the reciprocating movements of a reciprocating machine, substantially as hereinbefore described with reference to, and as shown in, Figures 2A and 2B of the accompanying drawings.

12. A reciprocating machine having a device as claimed in any one of the preceding claims.