WO2008037852A1

WO2008037852A1 - Crankshaft

Info

Publication number: WO2008037852A1
Application number: PCT/FI2007/050519
Authority: WO
Inventors: Tapio VIITAMÄKI
Original assignee: Greittek Oy
Priority date: 2006-09-27
Filing date: 2007-09-26
Publication date: 2008-04-03
Also published as: FI20065600A0

Abstract

The invention relates to a crankshaft (1), which comprises a bearing part (2) eccentric to the central axis (A) of the crankshaft and intended for supporting a connecting rod, a rotary piston or a corresponding member in reciprocating or eccentric circular or rotational motion, and means (3, 4, 6) for adjusting eccentricity of the bearing part. The means for adjusting eccentricity of the bearing part comprise a longitudinally movable piston (4) mounted in a longitudinal channel (5) inside the crankshaft (1) and comprising a key arrangement (6), and a counter key arrangement (3) connected to the bearing part (2) and extending through the wall of the crankshaft into said channel and co-operating with the key arrangement of the piston.

Description

CRANKSHAFT

BACKGROUND OF THE INVENTION

[0001] The invention relates to a crankshaft, which comprises a bearing part eccentric to the central axis of the crankshaft and intended for supporting a connecting rod, a rotary piston or a corresponding member in reciprocating or eccentric circular or rotational motion, and means for adjusting eccentricity of the bearing part.

[0002] The eccentricity adjustment of a crankshaft may be applied in all motors, pumps, compressors and apparatuses that use a crank mechanism.

[0003] In combustion engines, the volume and compression ratio of the motor may be adjusted simultaneously, which allows the use of different types of fuels in the same motor. Suitable motor characteristics required by the fuel may be achieved by changing the compression ratio, and the efficiency may be optimized for each range of stress. This is particularly important in supercharged engines.

[0004] In hydraulics, this adjustment may make a hydraulic pump or motor volume-adjustable. The efficiency of the hydraulic system may be optimized because there is no need to transfer the full volume flow produced by the hydraulic apparatus, if not required. This also helps to reduce the stress on the equipment. The same operational principle may also be applied to compressors to improve the efficiency of the system.

[0005] Prior art means for adjusting eccentricity of a crankshaft are mainly based on rotatable bushings on the crankshaft, the outer and inner circumferences of which have different centre points. When an eccentric bushing is mounted on a usually eccentric crankshaft, the total eccentricity of the cran kshaft may be affected by rotating the bushing. It is also possible to mount a plurality of bushings on top of one another, whereby the actual zero line of the system can be kept constant (i.e. the adjustment takes place along a linear line) when the bushings are rotated. Rotation mechanisms for the bushings are complicated and unreliable, and the rotation and thus the adjustment of the eccentricity are difficult to implement. Thus, to rotate the bushings, only the oil pressure is preferably used without any auxiliary mechanisms. However, this solution has been proven to be inefficient and as unreliable as the solutions using auxiliary mechanisms. SUMMARY OF THE INVENTION

[0006] It is an object of the invention to eliminate the above disadvantages and to provide a new type of eccentricity adjustment. This object is achieved by a solution of the invention, which is characterized in that the means for adjusting eccentricity of the bearing part comprise a longitudinally movable piston mounted in a longitudinal channel inside the crankshaft and comprising a key arrangement, and a counter key arrangement connected to the bearing part and extending through the wall of the crankshaft into said channel and co-operating with the key arrangement of the piston.

[0007] By means of the solution of the invention, the eccentricity of the crankshaft may be adjusted steplessly to a desired value easily and very reliably. It is also possible to carry out the adjustment while the application in question is used and also when forces and rotation speeds of the crankshaft are great. In spite of this, the adjustment means of the invention are simple and their manufacture is cost-efficient.

LIST OF FIGURES

[0008] The invention will now be described in greater detail by means of two preferred example embodiments and with reference to the attached drawings, in which

Figure 1 shows a first embodiment of a crankshaft of the invention in cross section from the side;

Figure 2 shows the crankshaft of Figure 1 from its end;

Figure 3 shows the crankshaft according to the previous figures without a bearing part and eccentricity adjustment means;

Figure 4 shows the bearing part of the previous figures from an end;

Figure 5 shows the bearing part according to the previous figures from the side;

Figure 6 shows a piston of Figure 1 , which is a part of the eccentricity adjustment means and comprises a wedge-shaped end;

Figure 7 shows a counter key of Figure 1 , which is a part of the eccentricity adjustment means and co-operates with the piston provided with a wedge-shaped end;

Figure 8 shows a second embodiment of a crankshaft of the invention in cross section from the side;

Figure 9 shows the crankshaft of Figure 8 from its end; and Figure 10 shows a piston of Figure 8, which is a part of the eccentricity adjustment means, and a key arrangement.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Referring now to the first embodiment example shown in Figures 1 to 7, and at first especially to Figures 1 and 2, there is shown a crankshaft 1 , which is particularly suitable for use in hydraulic pumps, for instance. The crankshaft 1 comprises a bearing part 2 eccentric to its central axis A for supporting a member in eccentric circular or rotational motion, e.g. a pump member or a rotary piston. In addition, members 3 and 4 are arranged to adjust the eccentricity of the bearing part 2. In accordance with the invention, these members comprise a longitudinally movable piston 4 mounted in a longitudinal channel 5 inside the crankshaft 1 and comprising a wedge-shaped end 6, and a counter key 3 connected to the bearing part 2 and extending through the wall of the crankshaft 1 into said channel 5 and co-operating with the wedge-shaped end 6 of the piston 4.

[0010] As Figure 4 shows, the bearing part 2 comprises a mounting opening 7 for mounting it on the crankshaft 1 , and the mounting opening 7 is provided with parallel, linear, opposite side walls 8, and as Figure 3 best shows, the crankshaft 1 is provided with parallel, linear, opposite side walls 9 co-operating with the side walls 8 of the mounting opening 7, whereby the movement for adjusting the eccentricity of the bearing part is realized as linear motion in the direction of the relative motion of the counter side walls 8 and 9, when the wedge-shaped end 6 of the piston 4 and the counter key 3 are moving with respect to one another.

[0011] The piston 4 is most preferably driven hydraulically, in which case the required hydraulic fluid, here most suitably oil, is supplied to the channel 5 behind the piston 4 via suitable oil channels (not shown). In this first embodiment example, the piston 4 is a single-acting piston, which means that it is pushed forwards with the oil pressure, whereas the piston 4 is reversed under the influence of counterforces applied on the bearing part 2, which are caused by the operation of the apparatus or machine on which the crankshaft 1 is mounted. By supplying pressurized oil behind the piston 4, its wedge- shaped end 6 lifts up the counter key 3, whereupon the eccentricity of the bearing part 2 in the crankshaft 1 increases, whereas, by letting the oil flow away from behind the piston 4, its wedge-shaped end 6, during its backward movement, allows the counter key 3 to move down, which reduces the eccentricity of the bearing part 2.

[0012] If required, the piston 4 described above may naturally also be used in a double-acting reciprocating manner, i.e. by guiding the pressurized hydraulic fluid to both sides of the piston 4.

[0013] According to the embodiment of Figures 8 to 10, the keying may also be double-acting and possibly combined with a double-acting hydraulic control of the piston. The embodiment according to Figures 8 to 10 differs in this case from the implementation of Figures 1 to 7 in that a piston 40 now comprises two keyways 41 , 42 on the opposite sides of its circumference and slanting in opposite directions, and two counter keys 31 , 32 extend through the wall from the opposite sides of the wall of the crankshaft 1 , each counter key being in co-operation with the corresponding keyway 41 , 42. This arrangement is suitable when the above-mentioned counterforces applied on the bearing part 2 are not sufficient to move the piston 40 backwards in order to reduce the eccentricity. When this bidirectional keying is boosted by the double-acting hydraulic drive of the piston 40, the eccentricity is adjusted reliably and rapidly in all situations and load conditions.

[0014] In both above examples, the piston 4, 40 may be driven not only by a hydraulic drive but also by mechanical or electrical machinery or suitable combinations of these drives, even though the hydraulic drive is most likely the simplest implementation.

[0015] The above description is only intended to illustrate the invention. A person skilled in the art may, however, use it in several different appl ications and implement its details in various ways within the scope of the appended claims. Thus, although a reference is made above particularly to a hydraulic pump, the invention may quite as well be applied to compressors, combustion engines and all machines in which the work and capacity achieved with the machine are based on an eccentric or reciprocating motion. Consequently, a connecting rod of a conventional percussion-piston combustion engine, for example, may be connected to a suitable crankshaft and a bearing part.

Claims

1. A crankshaft (1), which comprises a bearing part (2) eccentric to the central axis (A) of the crankshaft and intended for supporting a connecting rod, a rotary piston or a corresponding member in reciprocating or eccentric circular or rotational motion, and means (3, 4, 6; 31, 32, 40, 41, 42) for adjusting eccentricity of the bearing part, characterized in that the means for adjusting eccentricity of the bearing part comprise a longitudinally movable piston (4; 40) mounted in a longitudinal channel (5) inside the crankshaft (1) and comprising a key arrangement (6; 41, 42), and a counter key arrangement (3; 31, 32) connected to the bearing part (2) and extending through the wall of the crankshaft into said channel and co-operating with the key arrangement of the piston.

2. A crankshaft as claimed in claim ^ characterized in that the bearing part (2) comprises a mounting opening (7) for mounting it on the crankshaft (1), the mounting opening (7) is provided with parallel, linear, opposite side walls (8), and the crankshaft (1) is provided with parallel, linear, opposite side walls (9) co-operating with the side walls (8) of the mounting opening (7), and that the movement for adjusting the eccentricity of the bearing part (2) is linear motion in the direction of the relative motion of the counter side walls (8, 9).

3. A crankshaft as claimed in claim 1 or 2, characterized in that the key arrangement of the piston (4) comprises its wedge-shaped end (6) and the counter key arrangement comprises a counter key (3) extending through the wall of the crankshaft (1).

4. A crankshaft as claimed in claim 1 or 2, characterized in that the key arrangement of the piston (40) comprises two keyways (41 , 42) on the opposite sides of the circumference of the piston and slanting in opposite directions and the counter key arrangement comprises two counter keys (31, 32) extending through the wall of the crankshaft (1) from its opposite sides, each counter key being in co-operation with the corresponding keyway.

5. A crankshaft as claimed in any one of the preceding claims, characterized in that the piston (4; 40) is driven hydraulically.