CN101418721B - Multi-link engine - Google Patents

Abstract

The invention provides a multi-link engine, which can reliably prevent the positional displacement of the swing central shaft support cover relative to the engine body. The multi-link engine has: an upper connecting rod connected to a piston; a lower connecting rod freely rotatably mounted on a crank pin of a crankshaft and connected to the upper connecting rod; and a control connecting rod connected to the lower connecting rod. The rods are connected to swing around the swing center axis. The swing center shaft is located below the crankshaft journal, and is located on the opposite side of the cylinder center axis with the crankshaft journal as the center, and is rotatably supported between the engine body and the swing center shaft support cover. Timing located near the upper and lower dead centers, the central axis of the control connecting rod is roughly parallel to the central axis of the cylinder, the abutment surface between the swing central axis support cover and the engine body is orthogonal to the cylinder central axis, and the swing central axis support cover The central axis of the bolt to be tightened is parallel to the central axis of the cylinder.

Description

multi-link engine

technical field

The present invention relates to a multi-link engine, and more particularly to the connecting rod geometry of a multi-link engine.

Background technique

For example, as shown in Patent Document 1, an engine in which a piston pin and a crank pin are connected by a plurality of connecting rods (hereinafter referred to as a "multi-link engine") is being developed. The above-mentioned multi-link engine has: an upper connecting rod, which is connected to the reciprocating piston in the cylinder via a piston pin; a rod connection; and a control link that is connected to the lower link via a control pin and swings around the swing center pin. The swing center shaft is rotatably supported between the main bearing cover and the swing center shaft support cover, and the swing center shaft support cover is fastened to the main bearing cover by bolts. In addition, Patent Document 2 is included as another related patent document.

Patent Document 1: JP-A-2002-61501

Patent Document 2: JP-A-2001-227367

Contents of the invention

The inventors of the present invention have found that in the above-mentioned multi-link engine, if the load generated by the combustion pressure and inertial force acting on the piston is transmitted to the swing center shaft via each connecting rod, it will act on the force that pushes down the swing center shaft. In the direction, the so-called opening phenomenon may occur, that is, the position of the swing center shaft support cover relative to the main bearing cover is shifted.

The present invention is proposed in view of the existing above-mentioned problems, and its purpose is to provide a connecting rod geometry of a multi-link engine, which can reliably prevent the positional displacement of the swing center shaft support cover relative to the engine body .

The present invention solves the above-mentioned problems by means of the solutions described below. In addition, for ease of understanding, reference numerals corresponding to the embodiments of the present invention are attached, but the present invention is not limited thereto.

The invention relates to a connecting rod geometry of a multi-link engine, comprising: an upper connecting rod (11), which is connected via a piston pin (21) to a piston (32) reciprocating in a cylinder; a lower connecting rod (12 ), which is rotatably installed on the crank pin (33b) of the crankshaft (33), and is connected with the above-mentioned upper connecting rod (11) via the upper pin (22); and the control connecting rod (13), which is connected via the control pin ( 23) It is connected with the above-mentioned lower connecting rod (12) and oscillates around the oscillating center shaft (24), which is characterized in that the above-mentioned oscillating center shaft (24) is configured to be connected to the crankshaft bearing journal (33a) of the crankshaft (33) ) is located below, and is located on the opposite side of the central axis of the cylinder centered on the crankshaft bearing journal (33a), and is freely rotatably supported between the engine body (41, 42, 43) and the swinging central shaft support cover (44). During this period, the swing center shaft support cover (44) is fastened to the engine body (41, 42, 43) by bolts (45), when the above-mentioned piston (32) is located near the top dead center, and is located near the bottom dead center Timing, the central axis of the above-mentioned control connecting rod (13) is approximately parallel to the central axis of the cylinder, the abutment surface between the above-mentioned swing central axis support cover and the above-mentioned engine body is orthogonal to the cylinder central axis, and supports the swing central axis. The central axis of the bolt for fastening the cover is parallel to the central axis of the cylinder.

The effect of the invention

According to the present invention, the oscillating center shaft is disposed below the crank journal of the crankshaft and on the opposite side of the cylinder central axis with the crank journal as the center, is rotatably supported on the engine body, and is connected to the crank journal by bolts. Between the oscillating center shaft support covers fastened by the engine body, when the piston is positioned near the top dead center and at the timing near the bottom dead center, the central axis of the control connecting rod is approximately parallel to the central axis of the cylinder. With the above structure, when the magnitude of the load applied to the control link is the largest, no lateral load acts on the front end (swing center axis) of the control link, thereby preventing the swing center shaft support cover from shifting relative to the engine body. .

Description of drawings

FIG. 1 is a diagram illustrating a multi-link engine.

Fig. 2 is a diagram showing a state where the piston is located at the top dead center.

Fig. 3 is a diagram showing a state where the piston is located at the bottom dead center.

Fig. 4 is a longitudinal sectional view of the engine body.

FIG. 5 is a diagram illustrating an arrangement position of a swing central axis.

Fig. 6 is a diagram illustrating piston acceleration characteristics of a multi-link engine.

FIG. 7 is a diagram illustrating an arrangement position of a swing center axis that can reduce secondary vibrations.

FIG. 8 is a graph showing piston displacement and piston acceleration with respect to crankshaft angle.

Figure 9 shows a multi-link engine using the connecting rod geometry of this embodiment

A diagram of the change in load acting on the tip (swing center axis) of the control link.

Detailed ways

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings and the like.

First, a multi-link engine will be described with reference to FIG. 1 . In addition, FIG. 1 is a figure seen from the axial direction of a crankshaft. For ordinary technicians of the engine, outside the direction of gravity, it is customary to use the expression of top dead center/bottom dead center. In horizontally opposed engines, etc., the top dead center is not necessarily the top and bottom in the direction of gravity. In addition, if the engine is turned upside down, the top dead center is the bottom and bottom in the direction of gravity. The dead center is up in the direction of gravity, but in this specification, the top dead center side is described as up, and the bottom dead center side is described as down, as is customary.

In the multi-link engine 10, a piston 32 and a crankshaft 33 are connected by two connecting rods (upper connecting rod 11 and lower connecting rod 12). In addition, the control link 13 is connected to the lower link 12 .

The upper end of the upper link 11 is connected to the piston 32 via the piston pin 21 , and the lower end is connected to one end of the lower link 12 via the upper pin 22 . The piston 32 reciprocates in a cylinder liner 41 a provided on the cylinder block 41 under combustion pressure.

The lower link 12 has one end connected to the upper link 11 via the upper pin 22 and the other end connected to the control link 13 via the control pin 23 . In addition, the lower link 12 is inserted into a crank pin 33b of the crankshaft 33 into a substantially central connecting hole, and rotates around the crank pin 33b as a central axis. The lower link 12 can be divided into upper and lower parts. The center of the upper pin 22, the center of the control pin 23 and the center of the crank pin 33b are aligned on a straight line. The reason for employing the above positional relationship will be described later. The crankshaft 33 has a plurality of crank journals 33a and crank pins 33b. The crank journal 33 a is rotatably supported by the cylinder block 41 and the trapezoidal frame 42 . The crank pin 33b is eccentric from the crank journal 33a by a predetermined amount, and the lower link 12 is rotatably connected thereto.

The control link 13 is inserted into the control pin 23 at the front end, and is rotatably connected to the lower link 12 . In addition, the other end of the control link 13 can swing around the swing central axis 24 . The swing center shaft 24 is rotatably supported by a swing center shaft support bracket 43 and a swing center shaft support cover 44 . The swing center shaft support bracket 43 and the swing center shaft support cover 44 are fastened together on the trapezoidal frame 42 by bolts 45 . In addition, in this embodiment, the cylinder block 41, the trapezoidal frame 42, and the swing center shaft support bracket 43 correspond to the engine block in the claims. And, the swing center shaft 24 becomes an eccentric shaft as shown in the figure (that is, the other end of the control link 13 is connected to the eccentric part), and by moving the eccentric position of the swing center shaft 24, the swing center of the control link 13 is changed, and the piston is changed. 32 top dead center position. The compression ratio of the engine can thus be adjusted mechanically.

The swing center shaft 24 is positioned below the center of the crank journal 33a. In addition, the swing central axis 24 is located on the opposite side of the cylinder central axis with the crank journal 33a as the center. That is, when viewed from the axial direction of the crankshaft, when a straight line passing through the center of the crankshaft 33 (crankshaft bearing journal 33a) and parallel to the cylinder shaft is drawn, the swing central axis 24 is located at the center axis of the cylinder with respect to the straight line. The opposite side of that side. In FIG. 1 , the cylinder central axis is located on the right side with respect to the crank journal 33 a, and the swing central axis 24 is located on the left side with respect to the crank journal 33 a. The reason for disposing the swing center shaft 24 at the above position will be described later.

Fig. 2 is a diagram showing the state of the piston at the top dead center, Fig. 2(A) shows a longitudinal section, and Fig. 2(B) shows the geometric shape of the connecting rod. Fig. 3 is a view showing the state of the piston at the bottom dead center, Fig. 3(A) shows a longitudinal section, and Fig. 3(B) shows the geometric shape of the connecting rod. In FIG. 2(B) and FIG. 3(B), a solid line indicates a state of a low compression ratio, and a dotted line indicates a state of a high compression ratio.

The position of the swing central axis 24 is such that when the piston 32 is at the top dead center, the central axis of the control link 13 is substantially upright, preferably upright ( FIG. 2 ), and at the same time, when the piston 32 is at the bottom dead center, , make the central axis of the control link 13 approximately upright, preferably upright ( FIG. 3 ). In addition, the center axis of the control link 13 can be defined as a straight line connecting the center of the eccentric position of the swing center shaft 24 and the center of the control pin 23 when viewed from the axial direction of the crankshaft.

Fig. 4 is a longitudinal sectional view of the engine body.

The trapezoidal frame 42 is fastened on the cylinder block 41 by bolts. A crank journal 33 a of the crankshaft 33 is freely rotatably supported in a hole 40 a formed by the trapezoidal frame 42 and the cylinder block 41 . The abutting surface of the trapezoidal frame 42 and the cylinder block 41 is perpendicular to the central axis of the cylinder. In addition, the central axis of the bolt fastening the trapezoidal frame 42 and the cylinder block 41 is perpendicular to the contact surface. That is, the central axis of the bolt is parallel to the central axis of the cylinder.

The swing center shaft supporting bracket 43 and the swing center shaft support cover 44 are fastened together on the trapezoidal frame 42 by bolts 45 . In addition, in FIG. 4 , the center line of the bolt 45 is indicated by a dashed-dotted line. The swing center shaft 24 is rotatably supported in the hole 40 b formed by the swing center shaft support bracket 43 and the swing center shaft support cover 44 . The abutting surface of the pivot support bracket 43 and the trapezoidal frame 42 is perpendicular to the central axis of the cylinder. The contact surfaces of the swing center support cover 44 and the swing center shaft support bracket 43 are also perpendicular to the cylinder center axis. The central axis of the bolt 45 is perpendicular to these contact surfaces. That is, the center axis of the bolt 45 is parallel to the cylinder center axis.

FIG. 5 is a diagram illustrating an arrangement position of a swing central axis. FIG. 5(A) shows a comparative embodiment in which the swing center shaft is arranged above the crank journal, and FIG. 5(B) shows the present embodiment in which the swing center shaft is arranged below the crank journal.

As described above, in the present embodiment, the swing center shaft 24 is located below the crank journal 33 a and is located on the opposite side of the cylinder center axis around the crank journal 33 a. The reason for the above configuration will be described below.

First, for easy understanding, a comparative embodiment illustrated in FIG. 5 will be described.

As an arrangement position of the swing center shaft 24 , as shown in FIG. 5(A) , it is also conceivable to arrange it above the crank journal 33 a. However, with the above structure, there is a problem with the strength of the control link 13 .

That is, the maximum load among the loads acting on the control link is the load generated by the combustion pressure. The load F1 generated by the combustion pressure acts on the upper link 11 downward. Due to this downward load F1, a downward load F2 acts on the bearing portion of the crank journal 33a, and a clockwise turning moment M1 acts around the crankpin 33b. Then, an upward load F3 acts on the control link 13 by this moment M1. That is, a compressive load acts on the control link 13 . Here, considering that a compressive load acts on the connecting rod 13, the connecting rod 13 may buckle when the load is large. In addition, according to the Euler buckling equation shown in the following formula (1), the buckling load is inversely proportional to the square of the connecting rod length 1.

[Equation 1]

Euler buckling equation

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; cr</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; n\&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; EI</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

in,

P _cr : Buckling load

n: terminal condition coefficient

E: longitudinal elastic coefficient

I: Secondary moment of section

l: connecting rod length

As mentioned above, buckling may occur due to increasing the length 1 of the connecting rod, so it should not be too long. In order to increase the length of the connecting rod, it is necessary to increase the width and thickness of the connecting rod to increase the secondary moment of the section, but this is not practical due to problems such as increased weight.

Therefore, the length of the control link 13 has to be shortened, so the movement length of the front end (that is, the control pin 23 ) cannot be increased. Therefore, it is impossible to increase the size of the engine, and it is difficult to obtain a desired engine output.

To solve the above problems, in the present embodiment shown in FIG. 5(B), the swing center shaft 24 is arranged below the crank journal 33a. Thus, the load F1 generated by the combustion pressure is transmitted from the upper link 11 to the lower link 12 and acts on the control link 13 as a tensile load. When the tensile load acts on the connecting rod 13, the elastic damage of the connecting rod 13 should be considered, but it is generally believed that whether elastic damage occurs depends on the stress or strain of the connecting rod section, and the length of the connecting rod has little effect on it. Conversely, when considered in terms of the maximum principal strain, when the tensile load is the same, the strain becomes smaller by increasing the length of the connecting rod, making elastic damage less likely to occur.

As described above, since the control link 13 preferably receives the load due to the combustion pressure as a tensile load, in the present embodiment, the pivot center shaft 24 is arranged below the crank journal 33a.

In addition, in this embodiment, as described above, the center of the upper pin 22, the center of the control pin 23, and the center of the crank pin 33b are arranged on a straight line. Explain the reason.

According to the inventor's analysis, the multi-link engine, by properly adjusting the position of the swing central axis, is connected with a common conventional type engine (this is a common engine, but Compared with a multi-link engine (hereinafter referred to as a "single-link engine"), this engine can reduce vibration. Fig. 6 shows the analysis results. In addition, FIG. 6 is a diagram illustrating the piston acceleration characteristics of a multi-link engine, FIG. 6(A) is a diagram showing the piston acceleration characteristics of a multi-link engine, and FIG. 6(B) shows a single-link engine as a comparative example. A diagram of the piston acceleration characteristics of a rod engine.

As shown in Fig. 6(B), in a single-link engine, the magnitude (absolute value) of the overall piston acceleration after combining the primary component and the secondary component is higher than that near the top dead center compared with the bottom dead center. The value near the point is large. However, as shown in FIG. 6(A), in the multi-link engine, the magnitude (absolute value) of the overall piston acceleration is substantially the same near the bottom dead center and near the top dead center.

In addition, when comparing the magnitude of the secondary component of the single-link engine and the multi-link engine, the value of the multi-link engine is smaller than that of the single-link engine, and has the characteristic of reducing secondary vibration. .

As shown above, the multi-link engine can improve vibration characteristics (especially reduce secondary vibration) by properly adjusting the position of the swing center axis. Fig. 7 is a view explaining the arrangement position of the swing central axis which can reduce the secondary vibration, and the piston is located at the top dead center. Fig. 7 (A) shows the case where the crank pin is located below the line connecting the upper pin and the control pin, and Fig. 7 (B) shows the case where the crank pin is located above the line connecting the upper pin and the control pin, FIG. 7(C) shows a state where the crank pin is located on a line connecting the upper pin and the control pin.

As shown in FIG. 7(A), when the crank pin 33b is located below the line connecting the upper pin 22 and the control pin 23, the area where the swing central axis 24 can reduce the secondary vibration is indicated by the arrow. The range indicated by A. In order to use the control link 13 having a length set based on the performance requirements of the engine, the swing center shaft 24 is located on the left side (the side away from the crank journal 33 a ) compared to the control pin 23 .

As shown in FIG. 7(B), when the crank pin 33b is located above the line connecting the upper pin 22 and the control pin 23, the area where the swing central axis 24 can reduce the secondary vibration is The range indicated by arrow B. In order to use the control link 13 having a length set based on the performance requirements of the engine, the swing center shaft 24 is located on the right side (the side closer to the crank journal 33 a ) than the control pin 23 .

As shown in FIG. 7(C), when the crank pin 33b is located on the line connecting the upper pin 22 and the control pin 23, the area where the swing central axis 24 can reduce the secondary vibration is indicated by the arrow C represents the range. In order to use the control link 13 having a length set based on the performance requirements of the engine, the swing central axis 24 is positioned substantially directly below the control pin 23 . In the present embodiment, as described above, the swing central axis 24 is disposed at a position where the central axis of the control link 13 is substantially upright when the piston 32 is located at the top dead center and when the piston 32 is located at the bottom dead center. However, in order to reduce secondary vibration while realizing the above-mentioned geometric shape, it is necessary to arrange the crank pin 33b on a line connecting the upper pin 22 and the control pin 23 .

FIG. 8 is a graph showing piston displacement and piston acceleration with respect to crankshaft angle.

For the multi-link engine shown above, even if the connecting rod ratio λ (=upper connecting rod length l/crankshaft radius r) is not too large but is a general value (about 2.5 to 4), as shown in Fig. 8(A) As shown, compared with the single-link engine, it also has the characteristic that the amount of piston movement is small when the piston is located near the top dead center, and the amount of piston movement is large when the piston is located near the bottom dead center, with respect to a predetermined crankshaft angle change. And, the movement acceleration of the piston is as shown in FIG. 8(B). That is, in a multi-link engine, compared with a single-link engine, the moving acceleration of the piston becomes smaller near the top dead center, and the moving acceleration of the piston becomes larger near the bottom dead center, and has characteristics close to single vibration.

And, the inertial force produced by the above-mentioned piston acceleration characteristics acts on the front end (swing central axis 24) of the control link 13 of the multi-link engine 10 adopting the above-mentioned link geometry, as shown in FIG. 9(A). A force that changes in a period of 360 degrees. In addition, due to the combustion pressure, a force fluctuating at a period of 720 degrees acts on the tip (swing center axis 24) of the control link 13 as shown in FIG. 9(B). These forces are synthesized, and a force fluctuating at a period of 720 degrees acts on the tip (swing center axis 24) of the control link 13 as shown in FIG. 9(C).

The above-mentioned downward load acts to separate the swing center shaft support cover 44 from the swing center shaft support bracket 43, but if the load in the left and right direction also acts while the downward load is applied, it may cause the swing The center shaft support cover 44 is offset relative to the swing center shaft support bracket 43 . Therefore, as a countermeasure, it is necessary to increase the number of bolts 45 or use large-sized bolts 45 so that the bolts 45 fastening the swing center shaft support bracket 43 and the swing center shaft support cover 44 have sufficient axial force.

However, the present inventors noticed that the magnitude of the load acting on the control link 13 due to the inertial force and the combustion pressure is greatest near the top dead center or the bottom dead center. Therefore, in the multi-link engine, the connecting rod geometry is adopted in which the connecting rod 13 is substantially upright (preferably upright) near the top dead center or the bottom dead center. With the above structure, when the magnitude of the load acting on the control link 13 is the largest, no left-right load acts on the tip of the control link 13 (the swing center shaft 24), thereby preventing the swing center support cover 44 from swinging relative to the swing center shaft. The central shaft support bracket 43 is offset.

In addition, as described above, it is preferable to make the swing center shaft 24 an eccentric axis, and by moving the eccentric position of the swing center shaft 24, the swing center of the control link 13 is changed, and the top dead center position of the piston 32 is changed. In this way, the compression ratio of the engine can be adjusted mechanically, and the compression ratio can be reduced under high load operation. This is because by lowering the mechanical compression ratio under high load while setting the intake valve closing timing near the bottom dead center, it is possible to achieve the coexistence of ensuring output and preventing knocking. In addition, it is preferable to increase the compression ratio under low-load operation. This is because by increasing the mechanical compression ratio at low load and setting the timing of opening the exhaust valve near the bottom dead center while setting the timing of closing the intake valve farther from the bottom dead center, the expansion ratio can be increased and the exhaust loss. And, since the load acting on the control connecting rod 13 becomes larger under the above-mentioned high-load operation, the angle formed by the central axis of the control connecting rod 13 and the central axis of the cylinder is as shown in Fig. 2(B) or Fig. 3(B) As shown by the dotted line in , the angle on the low compression ratio side is smaller than that on the high compression ratio side, so that the swing center shaft support cover 44 can be more effectively prevented from shifting relative to the swing center shaft support bracket 43 .

The present invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the technical idea of the present invention. Obviously, the above-mentioned various modifications and changes are also included in the claims of the present invention.

For example, in the above-mentioned embodiment, the swing center shaft 24 is supported by the swing center shaft support bracket 43 and the swing center shaft support cover 44, and the swing center shaft support bracket 43 and the swing center shaft support cover 44 are connected to each other by the bolt 45. The trapezoidal frame 42 is fastened together, but a structure in which the swing central axis support bracket 43 and the trapezoidal frame 42 are integrally formed may also be used. In this case, the cylinder block 41 and the trapezoidal frame 42 correspond to the engine block in the claims.

Claims (5)

1. A multi-link reciprocating engine comprising:

a crankshaft;

a piston that reciprocates in a cylinder of the engine;

an upper connecting rod rotatably connected to the piston via a piston pin;

a lower link rotatably mounted on a crank pin of the crankshaft and rotatably coupled to the upper link via an upper pin; and

a control link, one end of which is rotatably connected with the lower link via a control pin, and the other end of which is rotatably connected with the engine body via a swing central shaft,

wherein the swing center shaft is disposed below a crank bearing journal of the crankshaft and on the opposite side of the cylinder center shaft with the crank bearing journal as a center, and the swing center shaft is rotatably supported between an engine body and a swing center shaft support cover fastened to the engine body by a bolt,

at a timing when the piston is located near the top dead center and a timing when the piston is located near the bottom dead center, the central axis of the control link is parallel to the central axis of the cylinder,

a contact surface between the swing center shaft support cover and the engine body is orthogonal to the cylinder center shaft,

the center axis of a bolt for fastening the swing center shaft support cover is parallel to the cylinder center axis.

2. The multi-link reciprocating engine according to claim 1,

the timing near the top dead center is near the timing at which the upward load acting on the pivot center axis due to the combustion pressure becomes maximum, or near the timing at which the downward load acting on the pivot center axis due to the inertial force becomes maximum,

the timing near the bottom dead center is a timing near a timing at which an upward load acting on the swing center axis due to an inertial force becomes maximum.

3. The multi-link reciprocating engine according to claim 1,

the crank pin of the crankshaft is disposed on a line connecting the upper pin and the control pin.

4. The multi-link reciprocating engine according to claim 1,

the reciprocating acceleration of the piston is equal to or greater than the maximum value at a timing near the top dead center.

5. The multi-link reciprocating engine according to claim 1,

the multi-link engine is a variable compression ratio engine capable of changing a compression ratio by adjusting the position of the swing center shaft in accordance with an operating condition,

the angle formed by the control rod center axis and the cylinder center axis is smaller on the low compression ratio side than on the high compression ratio side.

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