JP2006189004A - Variable compression ratio mechanism for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a lock state of a reciprocating piece, when a control shaft operates at a maximum-minimum operating angle or more, without using a special member, by regulating a screw lead angle of the reciprocating piece by an operating angle of the control shaft. <P>SOLUTION: This variable compression ration mechanism has the control shaft 9 arranged in parallel to a crankshaft and provided with an eccentric cam 10, a control plate 14 integrally arranged on this control shaft 9, the reciprocating piece 20 for slidably connecting a pin of a tip part to a slit of this control plate, and a rotatingly driving source for changing the internal combustion engine compression ratio by moving the reciprocating piece in the shaft direction by fixed position rotation by meshing with a base end part screw part of this reciprocating piece. The control plate 14 abuts on a stopper arranged in a position of a turning angle θ or more of the control shaft 9 determined by an expression of tan<SP>-1</SP>(p/πd)+tan<SP>-1</SP>μ≤θ(in the expression, μ: a friction coefficient, p: a screw pitch, d: a screw diameter, and θ: an angle formed of a fork of the control shaft and a vertical shaft), when the control shaft 9 is at the maximum-minimum operating angle or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine variable compression ratio mechanism that continuously changes the compression ratio of an internal combustion engine such as an automobile engine.

  In an automobile engine, generally, when the load applied to the engine is low, the amount of fuel sucked into the cylinder is small, so the temperature and pressure in the cylinder when the piston is located near the top dead center are low. , Combustion stability decreases. Therefore, the compression ratio is increased to improve the stability of combustion, and the expansion ratio is increased to improve the thermal efficiency, thereby reducing the fuel consumption. On the other hand, when the load applied to the engine increases, the amount of fuel sucked into the cylinder increases, the temperature in the cylinder rises, and knocking occurs. In order to prevent this knocking, a variable compression ratio mechanism has been developed that increases the compression ratio when the engine load is small and controls the compression ratio low when the engine load is large (see, for example, Patent Document 1). ).

  In this variable compression ratio mechanism, a lower link is rotatably attached to the crank pin of the crankshaft, one end of the upper link linked to the piston pin is linked to a part of the lower link, and a control shaft having an eccentric cam is provided. The other end of the control link, which is arranged in parallel with the crankshaft and one end of which is linked to the other part of the lower link, is linked to the eccentric cam of the control shaft. I can control it. The reciprocator used here is rotationally driven by a rotational drive source that meshes with a screw at the base end portion thereof, thereby converting the rotational motion into a linear motion in the axial direction. This is converted into a rotational motion to change the compression ratio of the internal combustion engine.

  In order to save the fuel consumption of the internal combustion engine, not only the power consumption of the reciprocator drive system as a whole is reduced, but also in the holding mode where the operation of the reciprocator is not required (compression ratio is fixed) It is very effective to hold it. In the holding mode, the compression ratio of the internal combustion engine is fixed, so no operation is required for the movement of the reciprocator. However, the holding force is required to hold the compression ratio because it receives the reaction force due to the explosion force in the cylinder of the internal combustion engine. It is. At this time, the reciprocator sets the screw lead of the reciprocator so that it can be held by itself, and an irreversible change makes it possible to achieve a power saving state in the holding mode.

  However, if the screw lead is set so that the motor is not driven reversely by an external force such as reaction force from the control shaft, and if there is a stopper for fixing the operating range on the control shaft, the operating range of the reciprocator When it comes into contact with the stopper, the reciprocator is locked by the screw action and becomes inoperable. For this reason, as a lock state avoidance measure, it does not operate beyond the maximum operating angle and does not contact the stopper.

  Alternatively, a thrust rolling bearing is interposed between the female screw member and the movement restricting member, and this thrust rolling bearing accepts the pressure of the female screw member and the movement restricting member while allowing relative rotation, and does not lock even when abutting. A structure is considered (see, for example, Patent Document 2).

JP 2002-138867 A (FIG. 1) Japanese Patent Laid-Open No. 8-268691 (FIGS. 1 to 3, [0006], [0018])

  Since the conventional variable compression ratio mechanism of the internal combustion engine is configured as described above, the reciprocator may be screw-locked. In order to avoid this screw lock, the operating range is limited and the stopper is not brought into contact with the stopper. In the structure, if it makes contact, it will become defective immediately, so there are problems such as the guarantee method and the method of bringing out the initial position of the internal combustion engine and the reciprocator without joining the stopper as the reference position This is a difficult situation as a real solution. Further, in the structure in which the thrust rolling bearing is interposed between the female screw member and the movement restricting member, there is a problem that the configuration is complicated and it is difficult to have a configuration that can withstand a large external force applied from the internal combustion engine.

  The present invention has been made to solve the above-described problems. By defining the screw lead angle of the reciprocator by the operating angle of the control shaft for varying the compression ratio, the control can be performed without using a special member. It is an object of the present invention to obtain a variable compression ratio mechanism of an internal combustion engine that can avoid a locked state of a reciprocator when a shaft is operated at a maximum or minimum operating angle.

A variable compression ratio mechanism for an internal combustion engine according to the present invention includes a plurality of links connecting a piston pin of a piston and a crank pin of a crankshaft, a control shaft provided with an eccentric cam and disposed in parallel with the crankshaft, A control link having one end connected to one of the plurality of links and the other end connected to the eccentric cam, a control plate integrally provided on the control shaft, and a slit at the tip of the control plate. A reciprocator to which a pin is slidably connected, a rotor meshing with a base end screw portion of the reciprocator, and the rotation of the rotor moves the reciprocator in the axial direction to rotate the control shaft. And a rotational drive source that changes the compression ratio of the internal combustion engine by changing the piston position by the rotation of the control shaft, and is obtained by the equation of tan ⁻¹ (p / πd) + tan ⁻¹ μ ≦ θ. A stopper provided at a position equal to or greater than the rotation angle θ of the control shaft is in contact with the control plate when the control shaft is at a maximum or minimum operating angle.

  According to the present invention, the control plate integrated with the control shaft is in contact with the stopper when the control shaft is at the maximum or minimum operating angle. The operating angle θ of the control plate is added to the screw lead angle. As a result, even if the screw lead angle of the reciprocator is set so as to be capable of self-holding, the operating angle θ of the control plate is added when the control plate comes into contact with the stopper, so that the screw lead angle can be self-held. Thus, there is an effect that the screw lock can be surely avoided without using a special member or the like.

Embodiment 1 FIG.
FIG. 1 is a longitudinal explanatory view showing a compression ratio variable mechanism of an internal combustion engine. A cylindrical cylinder 2 is formed in the cylinder block 1, and a piston 3 is disposed inside the cylinder block 1 so as to be movable up and down. The piston pin 4 of the piston 3 and the crankpin 6 of the crankshaft 5 are mechanically linked via a multi-link type compression ratio variable mechanism. The variable compression ratio mechanism includes a lower link 7 that is externally fitted to the crankpin 6 so as to be relatively rotatable, an upper link 8 that links the lower link 7 and the piston pin 4, and a cylinder that is provided in parallel with the crankshaft 5. A control shaft 9 extending in the row direction, an eccentric cam 10 provided eccentric to the control shaft 9, a control link 11 that links the eccentric cam 10 and the lower link 7, and a control shaft 9 are driven to rotate within a predetermined control range. And a reciprocator 20 (shown in FIG. 2) that is held at a predetermined rotational position.

  An upper end portion of the upper link 8 is connected to the piston pin 4 so as to be relatively rotatable, and a lower end portion is connected to the lower link 7 via the connecting pin 12 so as to be relatively rotatable. One end of the control link 11 is connected to the lower link 7 via a connecting pin 13 so as to be relatively rotatable, and the other end is externally fitted to the eccentric cam 10 so as to be relatively rotatable. A pin 20a of a reciprocator 20 is slidably engaged with a slit 15 of a control plate 14 provided on the control shaft 9. The position of the pin 20a adjusted by the reciprocator 20 determines the attitude of the linkage mechanism, and operates so that the compression ratio of the combustion chamber formed above the piston 3 is controlled. In FIG. 1, arrows A <b> 1 to A <b> 7 represent the direction and flow of the force applied to each part due to the fluctuating load during the combustion operation of the internal combustion engine.

  FIG. 2 is a front view showing an external configuration of the drive mechanism of the reciprocator 20. In the figure, a case 22 connected to an end face of a housing 21 incorporating a reciprocator 20 with a bolt 24, a cover 23 connected to an end face of the case 22 with a bolt 25, and a drive source attached to one end of the case. The electric motor 30 is comprised. The reciprocator 20 has a pin 20 a attached to the other end exposed from the housing 21, and its slide head is slidably engaged with the slit 15 of the control plate 14. The control plate 14 is rotated about the control shaft 9 when the pin 20a moves in the axial direction, and its movement is transmitted to the piston 3 via the linkage mechanism as shown in FIG. The compression ratio of the combustion chamber is controlled. Structurally, the reciprocator 20 is easily subjected to an alternating load generated by the original movement of the internal combustion engine via the linkage mechanism.

  FIG. 3 is a longitudinal explanatory view showing the internal structure of the drive mechanism of the reciprocator 20. Three gears 34, 35, and 36 serving as rotational driving force transmitting means for transmitting rotational driving force from a gear 33 provided on a motor pinion shaft 32 of an electric motor 30 serving as a driving source, and an inner surface of the gear 36 are formed. A drive mechanism for the reciprocator 20 is constituted by a female screw (rotational force transmitting means) 38 that is screwed into the male screw 37 of the reciprocator 20.

  The reciprocator 20 is slidably disposed in a substantially cylindrical housing 21. A case 22 coupled to the end surface of the housing 21 with a bolt 24 and a cover 23 coupled to the end surface of the case with a bolt 25. In the space 26 formed between the two, a gear 33 provided on the motor pinion shaft 32 of the electric motor 30 and three gears 34, 35 and 36 as rotational driving force transmitting means are accommodated. In addition, the cover 23 is formed with an inner space 27 in which the other end side of the reciprocator 20 can be stored. Further, an opening 28 for receiving the penetration of the motor pinion shaft 32 of the electric motor 30 is formed in a part of the cover 23, and the electric motor 30 is attached to the outer surface of the cover 23 around the opening such as a bolt. It is fixed by a fastening member (not shown).

A stopper 39 is provided on the internal combustion engine side so that the control plate 14 comes into contact with the vertical axis 0-0 passing through the center of the control shaft 9 at the left and right maximum and minimum operating angles θ. This stopper 39 is provided at a position equal to or greater than the operating angle of the control plate 14 integrated with the control shaft 9 obtained from the following equation.

Record

tan ⁻¹ (p / πd) + tan ⁻¹ μ ≦ θ

μ: Friction coefficient
p: Screw pitch
d: Screw diameter
θ: Angle between the control shaft fork and the vertical shaft

  In the illustrated example, stoppers 39 are provided at the maximum operating angle position and the minimum operating angle position of 45 ° left and right, that is, 90 ° operating angle of the control shaft 9 with respect to the vertical axis 0-0 passing through the center of the control shaft 9. According to the experimental results, the screw lock can be reliably avoided by providing the stopper 39 at an arbitrary position of 45 ° to 52.8 ° with respect to the vertical axis 0-0.

Next, the operation will be described.
When the electric motor 30 is rotationally driven, the rotational force is reduced by the intermediate gears 34 and 35 meshed with the gear 33 of the motor pinion shaft 32 and the rotational force is transmitted to the gear 36. In this case, since the gear 36 is rotatably supported by a bearing (not shown) at a fixed position in the case 22 or the cover 23, the rotation of the gear 36 causes the reciprocator 20 screwed to the inner periphery thereof to move in the axial direction. It is moved linearly to the housing 21 so as to protrude as shown in FIG. 4 or to be retracted as shown in FIG. This linear motion is converted into a rotational motion of the control plate, that is, the control shaft 9 when the pin 20 a at the tip of the reciprocator 20 slides in the slit 15 of the control plate 14. As a result, the height position of the piston 3 in the cylinder 2 is changed via a plurality of links and connecting pins, and the compression ratio of the internal combustion engine can be continuously changed.

In order to obtain an initial position, the reciprocator 20 is operated until the control plate 14 integrated with the control shaft 9 is brought into contact with the stopper 39. The stopper position is greater than the maximum / minimum operating angle θ of the control shaft 9. Yes, the control plate 14 contacts the stopper 39 in an inclined state. At the time of this contact, the control plate 14 is inclined, and the rotation angle θ of the control plate is added to the screw lead angle β of the reciprocator 20 shown in FIGS. As a result, by defining the screw lead angle β of the reciprocator 20 by the operating angle θ of the control shaft 9, even if the screw lead angle β of the reciprocator 20 is set so as to be capable of self-holding, the control plate 14 is stopped by the stopper 39. , The operating angle θ of the control plate is added, and the screw lead angle becomes equal to or larger than the self-holding angle, so that the screw lock can be surely avoided.
FIG. 5 is an auxiliary explanatory view of FIG. 4. FIG. 5 (1) shows that when the control plate 14 is operated at a minimum operating angle θ or more, FIG. 5 (2) shows the control plate 14 at a maximum operating angle θ or more. 5 (3) is a state diagram of screw lead angles when the control plate 14 is operated in a vertical state (θ = 0) from the axis.

  As described above, according to the first embodiment, even if the screw lead angle of the reciprocator 20 is an angle capable of self-holding that receives a reaction force from the internal combustion engine, a special component configuration is not required. Screw locking can be avoided reliably. In addition, since the stopper 39 for contacting the control plate 14 is provided on the internal combustion engine side, there is no risk of damage even if a large force is applied from the internal combustion engine side. If a stopper is provided on the reciprocator side, a large force is applied from the internal combustion engine side, so that the strength on the reciprocator side needs to be increased. An error is likely to occur in the operation amount of the piston of the internal combustion engine. Processing accuracy is required for the reciprocator. Further, since the control plate 14 is in contact with the stopper in an inclined state in which the control shaft 9 is rotated more than the maximum / minimum operating angle θ, the force from the internal combustion engine side is not directly applied to the reciprocator, and the reciprocator is damaged. Can be prevented.

1 is a longitudinal explanatory view showing a compression ratio variable mechanism of an internal combustion engine of the present invention. It is a front view which shows the external appearance structure of the drive mechanism of a reciprocator. It is a vertical explanatory view which shows the internal structure of the drive mechanism of a reciprocator. It is explanatory drawing of a screw lead angle when a control plate contact | abuts to a stopper in the inclination state. It is a state figure of the screw lead angle in the state (θ = 0) where the control plate is perpendicular to the minimum / maximum / axis.

Explanation of symbols

  1 Cylinder block, 2 cylinder, 3 piston, 4 piston pin, 5 crankshaft, 6 crankpin, 7 lower link, 8 upper link, 9 control shaft, 10 eccentric cam, 11 control link, 12, 13 connecting pin, 14 control Plate, 15 slit, 20 reciprocator, 20a pin.

Claims (2)

A plurality of links for connecting the piston pin of the piston and a crank pin of the crankshaft, a control shaft provided with an eccentric cam and disposed in parallel with the crankshaft, and one end connected to one of the plurality of links; A control link having the other end connected to the eccentric cam, a control plate integrally provided on the control shaft, a reciprocator having a tip pin slidably connected to a slit of the control plate, and A rotor meshing with a base end screw portion of the reciprocator, and the rotation of the rotor causes the reciprocator to move in the axial direction to rotate the control shaft, and the rotation of the control shaft allows the piston position to be adjusted. Rotation drive source that changes the compression ratio of the internal combustion engine by changing it, and the rotation angle of the control shaft that is obtained from the following formula where the control plate abuts when the control shaft is above the maximum / minimum operating angle Internal combustion engine variable compression ratio mechanism and a stopper provided at more positions.

Record

tan ⁻¹ (p / πd) + tan ⁻¹ μ ≦ θ

μ: Friction coefficient
p: Screw pitch
d: Screw diameter
θ: Angle between the control shaft fork and the vertical shaft   2. The internal combustion engine compression ratio variable mechanism according to claim 1, wherein the stopper is provided on the internal combustion engine side.

Images