FR2669676A1 - Bearings making it possible to vary the compression ratio of an internal combustion engine - Google Patents

Abstract

The subject of the present invention is a modified crankshaft bearing of an internal combustion engine. The bearing (4) according to the invention is off-centred with respect to the axis of the crankshaft and includes an intermediate cylindrical bearing (6) which supports the crankshaft journal. When this intermediate bearing is pivoted, the crankshaft changes its position with respect to the engine block and, consequently, the compression ratio also changes. In order to control the movement of the intermediate bearings, these are connected to a shaft (11) located in the crankcase away from the path of the connecting rod big ends and which, owing to its torsional rigidity, ensures perfect alignment of these bearings.

Description

 The object of the present invention is a modified bearing of the crankshaft of an internal combustion engine. The bearing according to the invention is eccentric with respect to the axis of the crankshaft and comprises an intermediate bearing which supports the journal of the crankshaft. When this intermediate bearing is pivoted, the crankshaft changes its position relative to the block and, consequently, the compression ratio also changes.

 The crankshaft of an engine being supported by several - at least two - bearings, it is necessary to connect the intermediate bearings to each other to ensure the simultaneity of their movement. According to the invention, the intermediate bearings are connected to a shaft whose role is to ensure this synchronization.

 NOTE: To avoid confusion in the interpretation of terms like top, bottom, vertical, horizontal etc, we specify that in the description as well as in the claims we will consider an engine whose axis of the crankshaft is horizontal, the axes of the vertical cylinders and the cylinders are positioned above the crankshaft. Of course, this does not prevent the application of the device according to the invention to engines whose configuration is different, which are iflcflnés ,; inverted etc. For the sake of brevity, we will subsequently (except in the claims) call the intermediate bearings interPaliers and the tree connecting them server.

 The object of the invention is to allow the adaptation of the compression ratio of the engine to the instantaneous conditions of its operation.

 The thermal efficiency of an engine directly depends on its compression ratio. Like most engines, especially those used in vehicles, is only rarely used to the maximum of their possibilities. The modulation of the power is generally carried out by suffocation of the suction, therefore by a reduction in the quantity of the combustible mixture admitted into the cylinders. This has the consequence of reducing the pressures both at compression and at explosion. The engine works in reality with a compression ratio lower than its nominal rate. Its thermal efficiency decreases and its specific consumption increases. It is therefore advantageous to maintain the volume compression rate at its optimal value, which can be obtained by varying the geometric compression rate.

 This phenomenon is particularly accentuated on turbocharged engines. These must have a lower compression ratio to counteract the increase in pressure due to the compressor.

 The e ++ icacity of the latter at low speeds decreases and the characteristics of the engine deteriorate.

 The problem is well known and several possibilities have already been proposed for producing motors with variable compression ratio.

Some consider either the linkage linkage or the use of double pistons, which increases the weight of moving parts and considerably complicates the mechanism. Others create in the cylinder head a small cylinder fitted with an auxiliary piston, the displacement of which varies the volume of the combustion chamber, but to the detriment of the compactness and simplicity of its shape. The small diameter of this auxiliary piston in relation to the diameter of the main piston requires a large stroke to obtain significant variations in compression ratio and in addition it becomes difficult to house the valves there.

 Finally, there are proposals with the position of the adjustable crankshaft relative to the cylinder block. However, these generally have a major drawback: the crankshaft bearings are supported by a frame articulated along an axis with an adjustment element on the opposite side. Of course, the articulation axis of the frame as well as its longitudinal bar connecting the transverse arms which support the bearings must necessarily be outside the path of the connecting rod heads, which determines the size of the casing. This results in an increase in the width of the motor and, what is more serious, the frame being stressed especially in bending can be a generator of serious vibrations.

 The object of the present invention is to eliminate these drawbacks. The bearings of the crankshaft according to the invention are double: the main bearings remain an integral part of the engine block, but are completed by the cylindrical interpaliers, the axis of which is eccentric with respect to the axis of the cylinders. In these interpaliers are housed the crankshaft housings, the axis of which is situated substantially in the plane of the axes of the cylinders. Thanks to the eccentricity of the bearings relative to the axis of the crankshaft, the rotation of the intermediate bearings along their axis causes the displacement of the crankshaft relative to the engine block according to an arc of circle. of the crankshaft relative to the axis of the cylinder (s) (horizontal component), on the other hand a variation in compression ratio as a consequence of bringing the crankshaft closer or further away from the cylinder block (vertical component.

The eccentricity (E) of the bearing is a function of this vertical movement and of the angle of rotation As. It is preferable to distribute the angle of rotation symmetrically with respect to the horizontal, which gives
A '= A / 2
dY '= dY / 2
E = dY'Xsin A '
The offset of the crankshaft relative to the plane of the cylinder axes can also be distributed symmetrically and therefore
dx '= E (1-cos A') / 2
The judicious choice of eccentricity and angle of rotation minimizes the shift to a negligible value.

 Even for the extreme value of rotation between + and -90 with respect to the horizontal, dY = Ymax - Ymin = 2 E, while d, \ 'max = E, but given the possibility of distributing this value symmetrically by relative to the axis of the cylinders, the offset d, K 'would not exceed E,' S, i.e. 1/4 vertical displacement.

 If we consider varying the compression ratio between 8 and 30, we can see that this extent requires the displacement of the crankshaft by about 11% of the piston stroke. By taking for the eccentricity 2W / of the stroke, this results in an angular amplitude of about 25 '@ distributed symmetrically with respect to the horizontal. The offset of the crankshaft relative to the cylinder axis is in this case only about 0.3% of the stroke, which is negligible. What is important is that these values make it possible to produce the interpaliers of a diameter small enough to be housed inside a casing without increasing the width. The drawings which accompany the present invention are moreover based on existing motors whose proportions and shape of the block have been respected.

 Of course, the loads that each bearing must support are variable according to the working cycles of the respective cylinders, it is therefore necessary to ensure the alignment of the bearings to avoid deformations of the crankshaft. For this purpose the interpaliers are connected by the links to the arms of a server shaft, whose torsional rigidity guarantees their alignment. The server shaft is preferably located below the crankshaft, outside the trajectory of the rod ends and it is supported by the bearings integrated in the caps of the main bearings.

 Thanks to the unevenness of the arms, the forces supported by this shaft are clearly lower than the forces produced by the pressures on the pistons and by the inertial forces, transmitted by the crankshaft to the bearing.

 In fact, the value of eccentricity is mainly determined by the need to keep the arms of the server shaft outside the trajectory of the heads of the connecting rods and by the concern to minimize the impact of the play in the connection between interpaliers and the shaft waiter, who believes with the angle of rotation of these elements.

 On a four-stroke multi-cylinder engine with the crankshaft not removable, to facilitate assembly, the interpaliers will be divided into two parts according to a plane which passes through the axis of the crankshaft and by the axis of connecting rod which connects the crankset the server tree.

 The server shaft can advantageously assume the transmission of the movement between the control device and the interalizer.

The control device can be a hydraulic or pneumatic cylinder, an electric motor, various mechanical connections whether or not etc. The means of control of this device can be various: the electronic shoemaker governing injection and ignition, the mechanical control directly connected to the accelerator, they can be controlled by knock detector etc. All of this is not the subject of this
invention, which is limited only to eccentric intermediate bearings and their server tree
The accompanying drawings fig. I to 4 present, by way of example, a possibility of producing an engine according to the invention. For the sake of clarity of the drawings, the mobile assembly (crankshaft, connecting rods, pistons) and the cylinder head are not shown. Moreover, compared to the conventional engine, these elements do not undergo modifications.

Figure I shows in cross section the motor equipped with
intermediate bearings according to the invention.

Figure 2 shows the location of the hydraulic cylinder
control in the cylinder block.

Figure 3 is a longitudinal section of this engine, illustrating
the link between the interpalier and the server tree, as well as the
method of fixing these elements in the casing.

Figure 4 illustrates in horizontal section the connection of
links with the server tree as well as the horizontal section of
interpal iers and anchoring rods.

 The figures show the engine block with the upper half-casing (1), the liners (2) and the lower sheet metal half-casing (3). The upper half-casing incorporates the fixed half-bearings <4), which are completed by their caps' N5). The bearings support the interpaliers, consisting of two parts (6a, 6b) due to mounting possibilities.

In each crankshaft is created the housing for the crankshaft journal provided with the bearings (7a, 75), as well as the housing for the axis (8) of the rods (9). The rods (9) connect the crossbar by the axes (12) with the arms 110) of the server shaft (11). The server tree is housed in the extension of the caps (5) supplemented by the small caps (14). On the server shaft are fixed, preferably towards the middle of its length, the force arms (15) (in this case the extensions of the arms 10), connected by a connecting rod (16) with a double action hydraulic cylinder ( 17).

 The server arbor <11) by its rigidity ensures perfect alignment of the interpaliers. The action of the actuator causes the rotation of the server shaft (11) and, consequently, of the spindle <6). This results in a variation of the position of the crankshaft <not shown} relative to the engine block (1), since the housings of the pins (7a, 7b) are eccentric relative to the axis of the interpaliers (6). The movement of the crankshaft axis takes place in a segment of the circle, but if the amplitude is kept between +15 'and -15, the horizontal component of this movement is negligible. This variation in the position of the crankshaft varies le: engine compression ratio.

 In order not to increase the longitudinal dimensions of the engine, the bearings (4) with their caps (5) are narrower than on the normal engine. By cons interpaliers es, have the necessary width, determined by the surface of the bearings (7) depending on the load.

This difference in thickness makes it possible to accommodate the connecting rods (9) on each side of the baleen cap not to exceed the width of the bearings. For their lateral support, the interpaliers are provided with a groove (13). To allow rotation of the spacer, relative to the links (9), which remain during the movement in the vertical position, a recess (18) is made on the sides of the spacers.

 This description relates to a possibility of implementing the present invention. Other variants are obviously possible without calling into question the principle of the interpalier and its relationship with the server tree. These variants therefore essentially concern the mode of coupling of these two elements and different types of control of their movement. The coupling modes can be different systems of links, rocker arms, gears or their segments, etc.

 The device for transmitting the rotation of the crankshaft, whose position of the axis is variable, to an output shaft to the fixed axis is not part of the present invention.

 The present invention is particularly intended for internal combustion engines without distinction of operating mode, which can be the Potto or Diesel cycle, two or four times. It can however be applied to any other mechanism which requires the use of a cranked crankshaft (crankshaft) coupled to the connecting rods, the operation of which can be improved by varying the position of the dead centers of movement of the latter.

Claims (2)

 1) Crankshaft bearings of an internal combustion engine characterized by the following facts:  -Their axis is offset from the axis of the crankshaft in  the direction perpendicular to the axis of the cylinder (s).  engine block they comprise intermediate bearings (6).  -In addition to the main bearings (4,5) firmly linked to  claimed below.  rotary movement is limited and controlled by means  can pivot inside the main bearings. Their  -The intermediate bearings (6) are cylindrical in shape and  engine and crankshaft construction.  bearings (7) or crankshaft bearings, depending on the type  -In the intermediate bearings (6) are incorporated the  Thanks to the eccentricity of the bearings relative to the axis of the crankshaft, the rotation of the intermediate bearings (6) along their axis generates the displacement of the crankshaft (not shown, relative to the engine block <1). This displacement is predominantly vertical and results in the variation of the geometric compression ratio of the engine.  2) A complementary device of the intermediate bearings es, according to claim 1, in the form of a shaft (11), parallel to the crankshaft, characterized in that it is provided with arms (10) connected by the rods (?) To said intermediate bearings (6), in order to synchronize the rotary movement of the latter. It can possibly transmit to these intermediate bearings <6) the force of a control device causing this movement.