JP4645038B2 - Belt type continuously variable transmission - Google Patents

Description

  The present invention relates to a belt-type continuously variable transmission, and more particularly to a technique for reducing belt noise during power transmission.

  One type of continuously variable transmission (CVT) is a belt-type continuously variable transmission that transmits torque by winding an endless belt between two pulleys arranged in parallel shafts. In a continuously variable transmission using an endless belt, the position where the endless belt winds around the conical wall of the pulley from the center of the rotating shaft by changing the distance between the conical wall of a pair of pulleys (primary pulley and secondary pulley) on the parallel rotating shaft Speed change (change in the rotation ratio between the primary pulley and the secondary pulley) is realized by changing the distance up to (that is, the radius of rotation when the endless belt is wound around the pulley, referred to as pitch circle radius in this specification). For example, if the pitch circle radius on the primary pulley side is reduced and the pitch circle radius on the secondary pulley side is increased, the gear ratio (ratio of output rotation speed to input rotation speed, pulley ratio in the case of a belt-type continuously variable transmission) is a pulley. If the pitch circle radius on the primary pulley side is increased, and the pitch circle radius on the secondary pulley side is decreased, the gear ratio becomes the speed reduction (overdrive) side with a small pulley ratio. It becomes. As a result, torque is transmitted from the primary pulley to the endless belt on the driving side and from the endless belt to the secondary pulley on the driven side at a position where the endless belt wraps around the pulley wall surface.

  As an endless belt for transmission of this type of belt-type continuously variable transmission, a belt or a chain in which metal link parts are usually combined in consideration of durability is used. On the other hand, since the pulley is also made of a metal material for the same reason, when the belt is wound around the pulley, the link parts constituting the belt repeatedly collide with the pulley cone wall surface. Pulley vibration is radiated from the pulley as noise. Hereinafter, this noise is referred to as belt noise in this specification.

By the way, the pulley is composed of a member having a conical surface fixed in the axial direction with respect to the pulley shaft (referred to as a fixed sheave in this specification) and a member having a conical surface movable in the axial direction (also referred to as a movable sheave). In a belt-type continuously variable transmission in which the fixed sheave and the movable sheave are arranged opposite to the belt on the primary pulley side and the secondary pulley side, between the conical surfaces on the primary pulley side at a specific pulley ratio. Even if the center position matches the center position between the conical surfaces on the secondary pulley side, the pulley ratio is changed (in order to match the distance between the conical surfaces on the pitch circle around which the belt is wound to the belt width, By changing the distance between the conical surfaces of the secondary pulley), it is inevitable that axial misalignment occurs at the center positions of each other. The reason is that when the center position between each conical surface moves in the direction away from the fixed sheave on the primary pulley side, it moves in the direction approaching the fixed sheave on the secondary sheave side, and conversely on the primary pulley side to the fixed sheave. This is because when moving in the approaching direction, the secondary sheave side moves away from the fixed sheave, and the amount of movement differs between the primary pulley side and the secondary pulley side with respect to the change in pulley ratio. That is, as long as one sheave constituting the pulley is fixed to the pulley shaft, misalignment due to the change in the pulley ratio is inevitable. This misalignment amount C is a value obtained by doubling the pitch circle radius when the pulley ratio is 1, D, a pulley angle (an angle formed between a pulley conical surface and a line perpendicular to the pulley axis), β, a pulley shaft The distance is a and the pulley ratio is i. C = (D ² / πa) · {(i−1) ² / (i + 1) ² } · tan β
It becomes. When this relationship is graphed with the horizontal axis representing the pulley ratio (i) and the vertical axis representing the misalignment amount (C), as shown in FIG. 2, it is expressed as a downwardly convex curve with respect to the change in the pulley ratio (i). It becomes a characteristic to be. Based on this characteristic, from the standpoint of ensuring durability and maintaining efficiency, the misalignment (C) is 0 at the pulley ratio at the maximum speed as shown by the curve connected with the ● mark in FIG. The setting to be made is the best. Non-patent document 1 is a document that discusses the setting of such misalignment.
"SAE Paper 881734", (USA), Society of Automotive Engineers, Inc., 1988, Vol. 97 (Vol. 97), Vol. 97 4 (No. 4), p. 4.1311-14.121

  Here, the maximum speed pulley ratio will be described with reference to FIG. Generally, in a vehicle equipped with a transmission, the output of the engine is converted into the output of the axle via the transmission, but the output of the axle is the axle torque x the rotational speed, and the rotational speed increases as the vehicle speed increases. Assuming that the output is constant (operating at the maximum output point), the axle torque decreases in inverse proportion. Therefore, the maximum driving force (the force that moves the vehicle forward) decreases as the vehicle speed increases, resulting in a downward-sloping curve as shown in the figure. In contrast, in a vehicle equipped with a belt-type continuously variable transmission, the engine is always operated at the maximum output point (constant rotation) above a certain speed, and the transmission gear ratio (pulley ratio) is underdrive in proportion to the vehicle speed. The speed is increased from (U / D) to overdrive (O / D). Further, the vehicle running resistance (shown in the figure shows the running resistance when running on a flat road) increases as the vehicle speed increases, and rises to the right as shown in the figure. From this relationship, the speed at which maximum driving force = running resistance is the maximum speed at which this vehicle cannot be accelerated any more, and the pulley ratio at that time is the maximum speed pulley ratio.

  By the way, as described above, in the pulley ratio at the maximum speed, the conventional setting in which the misalignment (C) is 0 is exclusively for pursuing the durability and efficiency of the belt-type continuously variable transmission. There is no consideration, and it is difficult to say that this setting is always suitable for applications that do not like the generation of noise, such as on-board belt-type continuously variable transmissions.

  In view of the above problems, the present invention pays attention to the relationship between belt noise and a structure peculiar to a belt-type continuously variable transmission that has been overlooked, and reduces belt noise by setting misalignment with respect to a pulley ratio. Main purpose.

The present invention includes two pulley shafts (1, 2) parallel to each other, a primary pulley (3) and a secondary pulley (4) disposed on each pulley shaft, and an endless coil wound around the primary pulley and the secondary pulley. The primary pulley has conical surfaces facing each other, and is fixed to the pulley shaft (1) so as to be fixed in the axial direction so as to sandwich an endless belt between the conical surfaces. A sheave (31) and a movable sheave (32) supported so as to be movable in the axial direction. The secondary pulleys have conical surfaces opposed to each other, and a pulley for sandwiching an endless belt between the conical surfaces. A fixed sheave (41) fixed to the shaft (2) so as not to move in the axial direction; and a movable sheave (42) supported so as to be movable in the axial direction; In the belt-type continuously variable transmission arranged so that the fixed sheave is positioned on the opposite side in the axial direction with respect to the endless belt, the center line position between the fixed sheave of the primary pulley and the conical surface of the movable sheave and the secondary sheave The axial distance between the fixed sheave of the pulley and the centerline position between the conical surfaces of the movable sheave is misaligned (C), and the axial distance is from the centerline position of the primary pulley to the fixed sheave side of the primary pulley. The main feature is that the pulley ratio region where the misalignment in the negative direction is defined as the total pulley ratio region that can be achieved by defining the case of distance as positive .

  The said structure WHEREIN: The said primary pulley and the secondary pulley shall be provided with the hydraulic chamber (33, 43) of the actuator which moves each movable sheave to an axial direction. Further, the misalignment is set to a predetermined value in a pulley ratio 1 where the pitch circle radii of the endless belts wound around the primary pulley and the secondary pulley are equal. The predetermined value in this case is set as the maximum value (−α) in the negative direction of misalignment that can occur with respect to the change in pulley ratio, based on the characteristics of the change in misalignment with respect to the change in pulley ratio (i). The

According to the belt type continuously variable transmission of the present invention, the misalignment in the negative direction is set over the entire range of pulley ratios that can be achieved , so that vibration is easily buffered by being movable with respect to the pulley shaft. Since the power transmission state in which the endless belt is strongly pressed against the movable sheave side is achieved at all pulley ratios, the belt noise of the belt type continuously variable transmission is comprehensively reduced.

  The present invention is preferably applied to a hydraulically operated belt-type continuously variable transmission in which a primary pulley and a secondary pulley have a hydraulic chamber of an actuator for moving the movable sheave in the pulley axial direction behind each movable sheave. . As a result, the hydraulic chamber can function as an oil damper against pulley vibration, so that the pulley vibration is more effectively buffered and the belt noise reduction effect is further improved.

  FIG. 1 schematically shows a configuration of a belt type continuously variable transmission according to an embodiment of the present invention. This transmission includes two pulley shafts 1 and 2 parallel to each other, a primary pulley 3 and a secondary pulley 4 disposed on each pulley shaft, and an endless belt 5 wound around the primary pulley and the secondary pulley. It becomes. The primary pulley 3 has conical surfaces facing each other, a fixed sheave 31 fixed to the pulley shaft 1 so as to be axially immovable so as to sandwich the endless belt 5 between the conical surfaces, and the conical surface movable in the axial direction. Similarly, the secondary pulleys 4 have conical surfaces facing each other, and are fixed to the pulley shaft 2 so as to be axially immovable so as to sandwich the endless belt 5 between the conical surfaces. The fixed sheave 41 and the movable sheave 42 whose conical surface is supported so as to be movable in the axial direction. The fixed sheave 31 of the primary pulley 3 and the fixed sheave 41 of the secondary pulley 4 are opposite to the endless belt 5 in the axial direction. It is arranged to be located on the side.

  In this embodiment, the movable sheaves 32 and 42 in the primary pulley 3 and the secondary pulley 4 are arranged behind the sheaves so that the conical surfaces of the sheaves 32 and 42 are moved in the axial direction by supplying and discharging hydraulic pressure. Hydraulic chambers 33 and 43 are provided. In addition, a shim 6 as a spacer for correcting the tolerance of the axial position of the secondary pulley 4 on the pulley shaft 2 side with respect to the primary pulley 3 on the pulley shaft 1 side and keeping the misalignment at the design value is provided on one pulley shaft 1. Arranged on the side.

  The belt-type continuously variable transmission having such a configuration reduces the amount of oil in the hydraulic chamber 33 on the primary pulley 3 side and moves the conical surface of the movable sheave 32 backward to reduce the distance between the conical surfaces of the sheaves 31 and 32. By increasing the amount of oil in the hydraulic chamber 43 on the secondary pulley 4 side and advancing the conical surface of the movable sheave 42, the distance between the conical surfaces of both sheaves 41, 42 is decreased, so that the distance between the conical surfaces is reduced. The width of the belt clamping space defined in the above is adjusted, the pitch circle radius on the primary pulley 3 side is reduced, and the pitch circle radius on the secondary pulley 4 side is increased, so that the power transmission in an underdrive state where the pulley ratio is greater than 1 I do. Conversely, the oil amount in the hydraulic chamber 33 is increased, the oil amount in the hydraulic chamber 43 is decreased, the distance between the conical surfaces is reduced on the primary pulley 3 side, and the distance between the conical surfaces on the secondary pulley 4 side is decreased. By increasing the distance, the width of the belt clamping space defined between the conical surfaces is adjusted, the pitch circle radius on the primary pulley 3 side is increased, and the pitch circle radius on the secondary pulley 4 side is decreased to reduce the pulley. Power transmission is performed in an overdrive state in which the ratio is smaller than 1.

  Along with such a speed change operation, the axial position (center position between the conical surfaces) of the belt clamping space defined between the conical surfaces of the primary pulley 3 and the secondary pulley 4 is aligned at a specific pulley ratio. Even if the misalignment is set to 0, as described at the beginning, misalignment (C) occurs inevitable at other pulley ratio positions. This relationship will be described again with reference to FIG. In the figure, the positive misalignment (C) means the center line position between the conical surfaces of the fixed sheave 31 and the movable sheave 32 of the primary pulley 3 and the center between the conical surfaces of the fixed sheave 41 and the movable sheave 42 of the secondary pulley 4. The axial distance from the line position is defined as misalignment (C), and this axial distance is defined as the distance from the center line position of the primary pulley 3 to the fixed sheave 31 side of the primary pulley 3. This definition is defined by the positional relationship when misalignment is viewed exclusively from the primary pulley side, but this positional relationship is completely the same when viewed from the secondary pulley 4 side. In this case, the misalignment is defined as positive when the axial distance is a distance from the center line position of the secondary pulley 4 to the fixed sheave 41 side of the pulley 4. Therefore, on the contrary, the axial distance is the distance from the center line position of the primary pulley 3 (or secondary pulley 4) to the movable sheave 32 (or movable sheave 42) side of the primary pulley 3 (or secondary pulley 4). In some cases, misalignment (C) is negative. The characteristic indicated by the mark ● in the figure shows the case where the misalignment is set to 0 at the maximum speed pulley ratio according to the conventional method. In this case, in the region where the pulley ratio (i) is larger than that at the pulley ratio of about 1.5, the positive misalignment increases approximately linearly as the pulley ratio increases, and in the region where the pulley ratio is small. As the pulley ratio decreases, the misalignment in the negative direction increases and reaches the maximum value at the pulley ratio of 1. After that, the misalignment in the negative direction changes to the decreasing direction and is finally set as the highest speed pulley ratio. It can be seen that the pulley ratio is 0 when the pulley ratio is about 0.7. The shape of the curve representing this characteristic is constant regardless of the pulley ratio at which the misalignment is set to 0. As the misalignment amount for a specific pulley ratio is changed, the mark ■ is added to the figure. It only moves in the direction of the vertical axis as shown.

  The present invention utilizes the above-described characteristics. The misalignment of the axial position of the belt clamping space defined between the conical surfaces of the primary pulley and the secondary pulley is defined as described above, and is summarized. Specifically, the pulley ratio region in which the negative misalignment occurs in the entire pulley ratio region that can be achieved is set wider than at least the pulley ratio region in which the positive misalignment occurs. In this case, the pulley ratio region in which the misalignment in the negative direction occurs can be set as the entire pulley ratio region, although it depends on the width. If these settings are viewed from other viewpoints, the maximum negative misalignment in the entire pulley ratio region is set to be larger than the maximum misalignment in the positive direction, or the negative misalignment in the entire pulley ratio region. It can also be said that the maximum alignment value is a value that does not cause misalignment in the positive direction.

  In the transmission of the present embodiment, based on the concept of the present invention, a negative misalignment is assumed in the pulley ratio at the maximum rotation of the output pulley shaft corresponding to the maximum speed in the vehicle-mounted state. More specifically, the misalignment is set to a predetermined value in the pulley ratio 1 where the pitch circle radii of the endless belt 5 wound around the primary pulley 3 and the secondary pulley 4 are equal. The predetermined value in this case is set as the maximum value (−α) in the negative direction of misalignment that can occur with respect to the change in the pulley ratio. Specifically, this setting is made by selecting a shim 6 having a different thickness as shown in FIG.

  By adopting such misalignment settings, most pulley ratios excluding the extremely high pulley ratio region (corresponding to the vehicle starting acceleration, etc.), as can be seen by referring to the characteristics of the curve connecting the ■ marks in FIG. In the region, power transmission is always performed in a state where a negative misalignment has occurred.

  FIG. 3 shows how the misalignment amount changes in each pulley ratio between the conventional misalignment setting and the misalignment setting according to the present invention. First, in the conventional setting shown in (A) of the figure, since the misalignment is set to 0 in the pulley ratio at the maximum speed as shown on the right side of the figure, when the pulley ratio is 1 shown in the center of the figure, In the upper primary pulley side in the figure, misalignment occurs as the distance from the center position between the conical surfaces to the movable sheave direction, so the misalignment is a negative value and the pulley ratio shown on the left side of the figure is large Then, similarly on the primary pulley side, misalignment occurs as a distance from the center position between the conical surfaces to the fixed sheave direction, and the misalignment changes to a positive value. On the other hand, in the setting shown in (B) of the diagram according to the present embodiment, the misalignment when the pulley ratio is 1 is set as the negative maximum value (−α) as shown in the center of the diagram. The misalignment remains negative even when the pulley ratio shown on the right side is the maximum speed pulley ratio, and the misalignment becomes 0 in the state where the pulley ratio shown on the left side of the figure is quite large. The left side of FIG. 3B is a case where the pulley ratio is about 1.9 in the curve connected with the ■ mark in FIG. If the pulley ratio is larger than this, the misalignment turns positive. 3 indicates the direction of deviation of the center position between the conical surfaces from the misalignment 0 state.

  Next, the reason why the pulley ratio region in which the negative misalignment as described above occurs in the present invention is set wider than the pulley ratio region or set as the total pulley ratio region will be described with reference to FIG. 1 shows a state in which the misalignment (C) is negative, that is, a center line position P3 between the conical surfaces of the fixed sheave 31 and the movable sheave 32 of the primary pulley 3, and the conical surfaces of the fixed sheave 41 and the movable sheave 42 of the secondary pulley 4. An axial distance (misalignment) C between the centerline position P4 and the centerline position P4 between them appears as a distance opposite to the distance from the centerline position P3 of the primary pulley 3 to the fixed sheave 42 side of the primary pulley 3 Is shown. In this state, the belt 5 is inclined not along the direction perpendicular to the pulley shafts 1 and 2 but along the displacement between the pulleys. When this misalignment is negative, the belt 5 is inclined toward the fixed sheaves 31 and 41 of the primary pulley 3 and the secondary pulley 4 with respect to the direction perpendicular to the pulley axis. FIG. 1 shows this state, and the belt 5 is inclined to the right side on the primary pulley 3 side and to the left side on the secondary pulley 4 side with respect to the state perpendicular to the pulley axis. Although the tension of the belt 5 works in the longitudinal direction of the belt 5, the belt 5 is inclined as described above, so that a component force in the pulley axis direction is generated in the tension of the belt 5. 2, the belt 5 is pushed to the left (movable sheave 32 side) on the primary pulley 3 side, and the belt 5 is pushed to the right (movable sheave 42 side) on the secondary pulley 4 side. When the alignment (C) has a negative value as shown in Fig. 2, this component force acts in a direction in which the belt 5 is pressed against the movable sheave side on either the primary pulley side or the secondary pulley side. Therefore, a relatively greater drag force is generated on the movable sheave (32, 42) side than on the fixed sheave (31, 41) side, whereas the component force in the direction perpendicular to the pulley axis of the tension of the belt 5 is movable. The sheave and the fixed sheave against the belt are balanced with the resultant force of the vertical component of the pulley shaft (due to the contact pressure between the sheave and the belt). -The vertical force of the movable sheave increases as the axial force increases, and the vertical force on the fixed sheave decreases accordingly, that is, if misalignment (C) occurs in the negative direction The vertical drag (contact pressure) on the sheave side increases and the vertical drag (contact pressure) on the fixed sheave side relatively decreases.

  In the hydraulically operated belt type continuously variable transmission, the movable sheaves 32 and 42 are provided with the hydraulic chambers 33 and 43 behind them as described above. The hydraulic pressure in the hydraulic chamber acts as an oil damper that buffers the vibration of the movable sheaves 32 and 42. Therefore, when the belt 5 sandwiched between the fixed sheaves 31 and 41 and the movable sheaves 32 and 42 is pressed more strongly against the conical surface side of the movable sheaves 32 and 42 as described above, the belt 5 on the fixed sheaves 32 and 42 side is provided. By reducing the contact pressure between the belt and the conical surface, vibration caused by repeated collisions of the belt constituting link members is reduced. On the movable sheave 32 and 42 side where the contact pressure is large, even if the movable sheave tries to vibrate strongly due to the collision of the belt-constituting link member, the vibration is buffered by the damper effect of the hydraulic chambers 33 and 43, and the vibration is attenuated. As a result, the overall vibration of the primary pulley 3 and the secondary pulley 4 is also reduced. The state in which the endless belt 5 is pressed more strongly on the movable sheaves 32 and 42 side in this manner occurs in a region where the misalignment is a negative value. Therefore, by expanding the negative misalignment region as compared with the pulley ratio region as in the embodiment, the belt noise is reduced over a wide pulley ratio region.

  Moreover, while the pulley ratio near the maximum speed pulley ratio is frequently used in normal vehicle travel, the misalignment in the conventional maximum speed pulley ratio is set to 0, and from the vicinity of the maximum speed pulley ratio. The pressing force of the belt to the fixed pulley side is reduced, and the belt noise is increased. On the other hand, according to the setting of the present embodiment, negative misalignment is always maintained in the vicinity including the maximum speed pulley ratio frequently used in normal vehicle travel. The belt noise at the time of steady running experienced by the passenger of the vehicle is effectively reduced.

1 is a schematic side view of a belt type continuously variable transmission according to an embodiment of the present invention. FIG. 6 is a misalignment characteristic diagram showing a misalignment setting in the transmission of the embodiment in comparison with a conventional setting. It is operation | movement explanatory drawing which shows the change of the misalignment with respect to the change of the pulley ratio of the transmission of an Example with contrast with what is based on the conventional setting. It is a graph which shows the driving | running | working characteristic of the vehicle carrying a belt type continuously variable transmission.

Explanation of symbols

1, 2 Pulley shaft 3 Primary pulley 4 Secondary pulley 5 Endless belt 31, 41 Fixed sheave 32, 42 Movable sheave 33, 43 Hydraulic chamber

Claims (4)

Two pulley shafts (1, 2) parallel to each other, a primary pulley (3) and a secondary pulley (4) disposed on each pulley shaft, and an endless belt (5) wound around the primary pulley and the secondary pulley The primary pulley has a conical surface facing each other, and a fixed sheave (31) fixed to the pulley shaft (1) so as to hold the endless belt between the conical surfaces. And a movable sheave (32) supported so as to be movable in the axial direction, the secondary pulleys having conical surfaces facing each other, and a pulley shaft (2) for sandwiching an endless belt between the conical surfaces A fixed sheave (41) fixed in the axial direction and a movable sheave (42) supported so as to be movable in the axial direction, the fixed sheave of the primary pulley and the fixed sheave of the secondary pulley. Bed is in arranged belt-type continuously variable transmission so as to be positioned axially opposite to the endless belt,
Misalignment (C) is the axial distance between the centerline position between the fixed sheave of the primary pulley and the conical surface of the movable sheave and the centerline position between the fixed sheave of the secondary pulley and the conical surface of the movable sheave. All pulley ratio regions that can achieve a pulley ratio region in which a misalignment in the negative direction occurs when the axial distance is defined as positive when the distance from the center line position of the primary pulley to the fixed sheave side of the primary pulley belt type continuously variable transmission, characterized in that the the. The primary pulley and secondary pulley, each provided in the hydraulic chamber of the actuator to the movable sheave is axially moved (33, 43), a belt type continuously variable transmission according to claim 1. The belt type continuously variable transmission according to claim 1 or 2 , wherein the misalignment is set to a predetermined value in a pulley ratio 1 in which pitch circle radii of the endless belts wound around the primary pulley and the secondary pulley are equal. The predetermined value is set as a maximum value (−α) in the negative direction of misalignment that can occur with respect to a change in pulley ratio, based on a characteristic of a change in misalignment with respect to a change in pulley ratio (i). Item 4. The belt type continuously variable transmission according to item 3 .

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