Toroidal-type continuously variable transmission

A toroidal-type continuously variable transmission has: an input shaft; an input disk and an output disk; a displacement shaft having a support shaft portion and a pivotal shaft portion; a trunnion having a support hole for supporting the support shaft portion; a first radial bearing supporting the support shaft portion within the support hole; a power roller having an insertion hole for receiving the pivot shaft portion; a second radial bearing supporting the pivot shaft portion within the insertion hole; and a thrust bearing including an outer ring and rolling elements, wherein a first bottom plate portion is provided at the support hole so as to close an opening of the support hole, a second bottom plate portion is provided at the insertion hole so as to close an opening of the insertion hole; and the displacement shaft and the outer ring are formed integrally with each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a toroidal-type continuously variable transmission.

2. Prior Art

FIGS. 3 and 4show one example of known toroidal-type continuously variable transmissions. An input disk2and an output disk4are rotatably supported on an input shaft15of a round tubular shape through respective needle roller bearings16. A cam plate10is engaged with an outer peripheral surface of an end portion (left end portion inFIG. 3) of the input shaft15through splines, and is prevented by a flange portion17from moving away from the input disk2. The cam plate10and rollers12jointly form a pressing device9of the loading cam-type which rotates the input disk2in accordance with the rotation of the input shaft15, while pressing the input disk2toward the output disk4. An output gear18is coupled to the output disk4by a key19so that the output disk4and the output gear18can synchronously rotate.

Power rollers8are held between the input disk2and the output disk4, and the power rollers8are supported by a pair of trunnions6each swingable about pivot shafts5located in a twisted position relative to the input shaft15. Opposite ends of each of the two trunnions6are supported respectively by a pair of support plates20in such a manner that the trunnion can be swung, and can be displaced in an axial direction (direction perpendicular to the sheet ofFIG. 3; left-right direction inFIG. 4) A displacement-shaft7is supported in a support hole23of a circular shape formed in each trunnion6. Each of the displacement shafts7has a support shaft portion21and a pivot shaft portion22which are parallel to each other, and are eccentric with respect to each other.

The support shaft portion21is rotatably supported in the support hole23through a radial needle roller bearing (first radial bearing)24. The pivot shaft portion22projects from an inner surface6aof the trunnion6, and is inserted in an insertion hole8bformed in the power roller8. The power roller8is rotatably supported on the pivot shaft portion22through a radial needle roller bearing (second radial bearing)25.

The pair of displacement shafts7are disposed respectively at diametrically-opposite (180 degrees spaced) positions with respect to the input shaft15. The pivot shafts portions22of the displacement shafts7are eccentric with respect to their respective support shaft portions21in the same direction (opposite (right and left) directions inFIG. 4) with respect to the direction of rotation of the input and output disks2and4. This direction of eccentricity is substantially perpendicular to the direction of extending of the input shaft15. Therefore, each power roller8is supported in such a manner that it can be displaced slightly along the direction of extending of the input shaft15. Therefore, even when each power roller8tends to be displaced in the axial direction of the input shaft15(that is, the left-right direction inFIG. 4; a direction perpendicular to the sheet ofFIG. 5) due to variations in dimensional accuracy of the component parts, resilient deformation thereof and so on, this displacement can be absorbed without exerting an undue force on the component parts.

Provided between an outer surface of each power roller8and the inner surface6aof the trunnion6are a thrust bearing26and a thrust needle roller bearing27(which supports a thrust load acting on an outer ring30) which are arranged in this order from the outer surface of the power roller8. The thrust bearing26, while bearing a thrust load acting on the power roller8, allows the rotation of the power roller8.

The thrust bearing26comprises a plurality of balls (rolling elements)29, and an annular retainer28, holding the balls29in a manner to allow the rotation of these balls29, and the annular outer ring30. An inner ring raceway of the thrust bearing26is formed at the outer surface of the power roller8, and an outer ring raceway thereof is formed at an inner surface of the outer ring30.

Each thrust needle roller bearing27comprises a race31, a retainer32, and needle rollers33. The race31and the retainer32are combined together in such a manner that they can be displaced slightly along the rotating direction. The thrust needle roller bearing27is held between the inner surface of the trunnion6and the outer surface of the outer ring30, with the race31held in contact with the inner surface of the trunnion6. The thrust needle roller bearing27, while bearing a thrust load applied from the power roller8to the outer ring30, allows the pivot shaft portion22and the outer ring30to swing about the support shaft portion21.

A drive rod36is connected to one end portion (left end portion inFIG. 4) of each trunnion6, and a drive piston37is fixedly mounted on an outer peripheral surface of this drive rod36intermediate opposite ends thereof. The drive piston37is fitted in a drive cylinder38in an oil-tight manner.

In the toroidal-type continuously variable transmission of the above construction, the rotation of the input shaft15is transmitted to the input disk2via the pressing device9. Then, the rotation of this input disk2is transmitted to the output disk4via the pair of power rollers8, and further the rotation of this output disk4is taken out from the output gear18.

For changing the rotational speed ratio between the input shaft15and the output gear18, the pair of drive pistons37are displaced in opposite directions, respectively. In accordance with the displacement of the pair of drive pistons37, the pair of trunnions6are displaced in opposite directions, respectively, and for example the lower power roller8(FIG. 4) is displaced right (FIG. 4) while the upper power roller8is displaced left. As a result, the direction of a tangential force, acting on an area of contact between a traction surface8aof each power roller8and an inner surface2aof the input disk2, as well as the direction of a tangential force acting on an area of contact between the traction surface8aand an inner surface4aof the output disk4, is changed. As a result of this change of the direction of the force, the trunnions6are swung respectively in opposite directions about their pivot shafts5pivotally supported by the support plates20. As a result, the position of contact between the traction surface8aof each power roller8and the inner surface2a(4a) is changed, so that the rotational speed ratio between the input shaft15and the output gear18is changed.

When the rotational force is thus transmitted from the input shaft15to the output gear18, each power roller18is displaced in the axial direction of the input shaft15in accordance with the resilient deformation of the component parts, and each displacement shaft7, pivotally supporting the power roller8, is angularly moved slightly about the support shaft portion21. As a result of this angular movement, the outer surface of the outer ring30of each thrust ball bearing26and the inner surface of the trunnion6are displaced relative to each other. Since the thrust needle roller bearing27is provided between this outer surface and this inner surface, a force, required for this relative displacement, is small. The force, required for changing the angle of inclination of each displacement shaft7as described above, is small.

In the toroidal-type continuously variable transmission, the transmission of the power between the input disk2(the output disk4) and the power rollers8is thus effected by the traction drive. Therefore, it is necessary to apply a large pressing force to the point of contact (abutment) between the input disk2(the output disk4) and each power roller8. In order to produce this pressing force, there is, in many cases, used the above-mentioned pressing device9of the loading cam-type for producing the pressing force proportional to the input torque, a hydraulic pressing device (for producing an optimum pressing force) or the like.

When the input disk2is pressed toward the output disk4by the pressing device9upon driving of the toroidal-type continuously variable transmission, the pressing force and the traction force (tangential force) act on the point of contact of each power roller8with the input disk2and also on the point of contact of the power roller8with the output disk4, so that a load acts on each power roller8. Because of this load, the power roller8is deformed as indicated in broken lines inFIG. 5, so that the insertion hole8bin the power roller8is also deformed.

Therefore, the inner peripheral surface of the insertion hole8bin the power roller8is inclined with respect to the radial needle roller bearing25, that is, the radial needle roller25is locally contacted with the inner peripheral surface of the insertion hole8b. As a result, the resistance of the radial needle roller bearing25to the insertion hole8b(that is, the rolling resistance of the radial needle roller bearing25) increases, so that a power transmission loss at the radial needle roller bearing25increases.

And besides, as a result of deformation of the power roller8, the inner ring raceway of the thrust bearing26, formed at the outer peripheral portion of the power roller8, is deformed. Therefore, a load, acting on the balls29of the thrust bearing26, becomes uneven, so that the power transmission loss at the thrust bearing26increases.

In addition, when each displacement shaft7is inclined by the above traction force, a radial load acts on the balls29of the thrust bearing26. Therefore, the smooth rotation of the balls29is prevented, so that the power transmission loss at the thrust bearing26increases.

Furthermore, a component of the above pressing force in the thrust direction acts on each trunnion6, so that the trunnion6is resiliently deformed by this component. Therefore, the outer ring30, supported on the trunnion6through the thrust needle roller bearing27, is inclined, so that the load, acting on the balls29of the thrust bearing26, becomes uneven, thus preventing the smooth rotation of the balls29. And besides, the support hole23in the trunnion6is also deformed in accordance with the resilient deformation of the trunnion6, and therefore the contact of the radial needle roller bearing24(provided in the support hole23in the trunnion6) with the support shaft portion21of the displacement shaft7becomes uneven, so that the resistance of the radial needle roller bearing24to the support shaft portion21increases. Therefore, the power transmission loss at the radial needle roller bearing24provided in the support hole23in the trunnion6, as well as the power transmission loss at the thrust bearing26, increases.

Thus, in the conventional toroidal-type continuously variable transmission, the deformation of the power rollers8, the inclination of the displacement shafts7and the deformation of the trunnions6occur at the time of driving this transmission, and therefore the smooth rotation of the bearings24,25and26is prevented. As a result, the power transmission loss at each of the bearings24,25and26increases, so that the power transmission efficiency is lowered.

SUMMARY OF THE INVENTION

This invention has been made under the above circumstances, and an object of the present invention is to provide a toroidal-type continuously variable transmission which can enhance the power transmission efficiency.

The above object has been achieved by a toroidal-type continuously variable transmission of the present invention of a first aspect which has: an input shaft; an input disk and an output disk each having inner surface and concentrically mounted on the input shaft so as to rotate relative to each other, inner surfaces thereof being opposed to each other; a displacement shaft having a support shaft portion and a pivotal shaft portion, the support shaft-portion and the pivotal: shaft portion are eccentric each other; a trunnion having a support hole for rotatably supporting the support shaft portion of the displacement shaft, and swinging about a pivot shaft disposed in a twisted position with respect to the input shaft; a first radial bearing rotatably supporting the support shaft portion of the displacement shaft within the support hole of the trunnion; a power roller having an insertion hole for receiving the pivot shaft portion of the displacement shaft, and disposed between the input disk and the output disk; a second radial bearing rotatably supporting the pivot shaft portion within the insertion hole of the power roller; and a thrust bearing including an outer ring disposed between the power roller and the trunnion, and rolling elements held between the outer ring and the power roller, and bearing a thrust load acting on the power roller, wherein a first bottom plate portion is provided at the support hole of the trunnion so as to close an opening of the support hole; wherein a second bottom plate portion is provided at the insertion hole of the-power roller so as to close an opening of the insertion hole; and wherein the displacement shaft and the outer ring are formed integrally with each other.

In the present invention of the first aspect, there is provided the first bottom plate portion which closes the opening in the support hole in the trunnion, and therefore as compared with the case where the support hole is in the form of a through hole, the deformation of the trunnion is suppressed at the time of driving the transmission, and therefore the outer ring is less liable to be inclined. Therefore, a load, acting on the rolling elements of the thrust bearing, is substantially uniform, and the rolling elements of the thrust bearing rotate smoothly, so that a power transmission loss at the thrust bearing decreases. As a result, the transmission of the power by the thrust bearing is effected smoothly.

And besides, the deformation of the support hole is also suppressed as a result of suppression of the deformation of the trunnion, and therefore the first radial bearing, provided in this support hole, and the support shaft portion of the displacement shaft, supported by this first radial bearing, are kept substantially parallel to each other, so that the first radial bearing uniformly contacts the support shaft portion of the displacement shaft. Therefore, a resistance of the first radial bearing to the support shaft portion is reduced, so that the power transmission loss at the first radial bearing decreases. As a result, the transmission of the power by the first radial bearing is effected smoothly.

In the present invention, there is provided the second bottom plate portion which closes the opening in the insertion hole in the power roller, and therefore as compared with the conventional power roller having the insertion hole in the form of a through hole, the deformation of the power roller is suppressed at the time of driving the transmission. Therefore, the load, acting on the rolling elements (which are supported by the power roller and the outer ring) is substantially uniform, so that the power transmission loss at the thrust bearing decreases.

And besides, the deformation of the power roller is thus suppressed, and therefore at the time of driving the transmission, a point of contact between the input disk and the power roller, as well as a point of contact between the output disk and the power roller, is less liable to be displaced, and therefore the loss of transmission of the power from the input disk to the output disk decreases, so that the transmission of the power from the input disk to the output disk is effected smoothly.

Furthermore, the deformation of the insertion hole is also suppressed as a result of suppression of the deformation of the power roller, and therefore the second radial bearing and the inner peripheral surface of the insertion hole in the power roller are kept substantially parallel to each other, so that a resistance of the second radial bearing to the inner peripheral surface of the insertion hole is reduced. Therefore, the power transmission loss at the second radial bearing decreases, and the transmission of the power by the second radial bearing is effected smoothly.

In the present invention, the outer ring and the displacement shaft are formed integrally with each other, and therefore as the outer ring is pressed in the direction of the axis of the displacement shaft upon application of a thrust force thereto at the time of driving the transmission, the displacement shaft is also pressed in this axial direction, and therefore the displacement shaft is less liable to be inclined. Therefore, the radial load is less liable to act on the rolling elements of the thrust bearing, so that the power transmission loss at the thrust bearing decreases, and the transmission of the power by the thrust bearing is effected smoothly.

In the present invention, the power transmission loss of the thrust bearing and the power transmission loss of the first radial bearing, which are caused by the deformation of the trunnion, are decreased, and the power transmission loss of the thrust bearing, the power transmission loss of the second radial bearing and the loss of transmission of the power from the input disk to the output disk, which are caused by the deformation of the power roller, are decreased, and furthermore the power transmission loss of the thrust bearing due to the inclination of the displacement shaft is reduced. Therefore, the power transmission can be smoothly effected at each of these portions, and therefore the power transmission efficiency of the toroidal-type continuously variable transmission can be enhanced.

And besides, the support hole and the insertion hole are closed by the first and second bottom plate portions, respectively, and therefore it is not necessary to provide retainer rings or the like which prevent the support shaft portion and pivot shaft portion of the displacement shaft from being withdrawn respectively from these holes. Therefore, the number of the component parts can be reduced, and besides assembling errors can be reduced. Furthermore, since the displacement shaft and the outer ring are formed integrally with each other, the processing of fitting portions of the displacement shaft and outer ring does not need to be effected.

Furthermore, it is not necessary to increase the size of the trunnion and power roller in order to suppress the deformation of the trunnion and power roller, and therefore the compact design of the toroidal-type continuously variable transmission can be achieved.

In the present invention of a second aspect, the trunnion further has a pair of wall portions formed on an inner surface side thereof, the wall portions being extending substantially perpendicularly to the inner surface of the trunnion so as to form a pocket portion for receiving the power roller, and the wall portions are interconnected by an interconnecting member.

In the present invention, the wall portions of the trunnion are interconnected by the interconnecting member, and therefore the inner surface of the trunnion is less liable to be deformed into a concave shape. Therefore, the power transmission loss of the thrust bearing and the power transmission loss of the first radial bearing, which are caused by the deformation of the trunnion, are further decreased.

In the present invention of a third aspect, the displacement shaft further has a stopper portion on the pivot shaft portion for preventing the second radial bearing from moving in a axial direction of the pivot shaft portion, the stopper portion being formed integrally with the pivot shaft portion.

In the present invention, the stopper portion for preventing the movement of the second radial bearing is formed integrally on the displacement shaft, and therefore it is not necessary to provide a separate stopper member for preventing the movement of the second radial bearing, and therefore the number of the component parts is further reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. Those constituent elements, similar to those ofFIGS. 3 and 4, will be designated by identical reference numerals, respectively, and explanation thereof will be simplified.

FIG. 1shows the first embodiment of the present invention. As shown in this Figure, a support hole23with a closed bottom is formed in a trunnion6, and serves to rotatably support a support shaft portion21of a displacement shaft7. Namely, a first bottom plate portion40is provided at that end of the support hole23, disposed close to an outer surface6bof the trunnion6, and is formed integrally with the trunnion6, and an opening in the support hole23in the trunnion6is closed by this first bottom plate portion40.

An insertion hole8bwith a closed bottom is formed in a power roller8, and serves to receive a pivot shaft portion22of the displacement shaft7. Namely, a second bottom plate portion41is provided at that end of the insertion hole8bremote from an outer ring30, and is formed integrally with the power roller8, and an opening in the insertion hole8bin the power roller8is closed-by this second bottom plate portion41.

The outer ring30, cooperating with the power roller8to hold balls29therebetween, is disposed between an inner surface6aof the trunnion6and the power roller8, and is formed integrally with the displacement shaft7.

A step portion (stopper portion)22ais formed integrally on the pivot shaft portion22of the displacement shaft7, and this step portion22aand the second bottom plate portion41, closing the insertion hole8bin the power roller8, prevent a second radial bearing25from moving in a direction of the axis of the pivot shaft portion22.

In a toroidal-type continuously variable transmission of the above construction, there is provided the first bottom plate portion40which closes the opening in the support hole23in the trunnion6, and therefore as compared with the case where the support hole23is in the form of a through hole, the deformation of the trunnion6is suppressed at the time of driving the transmission, and therefore the outer ring30is less liable to be inclined relative to the trunnion6, so that a load, acting on the balls29of a thrust bearing26, is substantially uniform. As a result, the balls29rotate smoothly, so that a power transmission loss at the thrust bearing26decreases, and therefore the transmission of the power by the thrust bearing26is effected smoothly.

And besides, the deformation of the support hole23is also suppressed as a result of suppression of the deformation of the trunnion6, and therefore a first radial bearing24, provided in the support hole23, and the support shaft portion21, supported by this radial bearing24, are kept substantially parallel to each other, so that the first radial bearing24uniformly contacts the support shaft portion21. Therefore, a resistance of the first radial bearing24to the support shaft portion21is reduced, so that the a power transmission loss at the first radial bearing24decreases, and the transmission of the power by the first radial bearing24is effected smoothly.

In this embodiment, there is provided the second bottom plate portion41which closes the opening in the insertion hole8bin the power roller8, and therefore as compared with the case where the insertion hole8bin the form of a through hole, the deformation of the power roller8is suppressed. Therefore, the load, acting on the balls29of the thrust bearing26, is substantially uniform, so that the power transmission loss at the thrust bearing26decreases, and the transmission of the power by the thrust bearing26is effected smoothly.

And besides, the deformation of the power roller8is suppressed, and therefore at the time of driving the transmission, a point of contact between an input disk2and the power roller8, as well as a point of contact between an output disk4and the power roller8, is less liable to be displaced, and therefore the loss of transmission of the power from the input disk2to the output disk4decreases, so that the transmission of the power from the input disk2to the output disk4is effected smoothly.

Furthermore, the deformation of the insertion hole8bis also suppressed as a result of suppression of the deformation of the power roller8, and therefore the inner peripheral surface of the insertion hole8band the second radial bearing25are kept substantially parallel to each other, so that the inner peripheral surface of the insertion hole8buniformly contacts the second radial bearing25. Therefore, a resistance of the second radial bearing25to the insertion hole8bis reduced, so that the power transmission loss at the second radial bearing25decreases, and the transmission of the power by the second radial bearing25is effected smoothly.

In this embodiment, the outer ring30and the displacement shaft7are formed integrally with each other, and therefore there is not encountered a situation in which the outer ring30and the displacement shaft7shake relative to each other at their fitting portions. And besides, as the outer ring30is pressed in the direction of the axis of the displacement shaft7upon application of a thrust force thereto at the time of driving the transmission, the displacement shaft7is also pressed in this axial direction, and therefore the displacement shaft7is less liable to be inclined. Therefore, the radial load is less liable to act on the balls29of the thrust bearing26, so that the power transmission loss decreases, and the transmission of the power by the thrust bearing26is effected smoothly.

In this embodiment, thus, the power transmission loss of the thrust bearing26and the power transmission loss of the first radial bearing24, which are caused by the deformation of the trunnion6, can be decreased. And besides, the power transmission loss of the thrust bearing26, the power transmission loss of the second radial bearing25and the loss of transmission of the power from the input disk2to the output disk4, which are caused by the deformation of the power roller8, can be decreased. Furthermore, the power transmission loss of the thrust bearing26due to the inclination of the displacement shaft7can be reduced.

Therefore, the power transmission can be smoothly effected at each of these portions, and therefore the power transmission efficiency of the toroidal-type continuously variable transmission can be enhanced. And besides, the deformation of the trunnion6and power roller8can be suppressed without the need for increasing the size of the trunnion6and power roller8, and therefore the compact design of the toroidal-type continuously variable transmission can be achieved.

Since the support hole23and the insertion hole8bare closed by the first and second bottom plate portions40and41, respectively, it is not necessary to provide retainer rings or the like which prevent the support shaft portion21and the pivot shaft portion22from being withdrawn respectively from the holes23and8b. Therefore, the number of the component parts can be reduced, and besides assembling errors can be reduced.

Furthermore, by forming the displacement shaft7and the outer ring30integrally with each other, the processing of the fitting portions of the displacement shaft7and outer ring30can be omitted.

In this embodiment, the step portion22for preventing the movement of the second radial bearing25is formed integrally on the pivot shaft portion22of the displacement shaft7, and therefore it is not necessary to provide a separate stopper member for preventing the movement of the second radial bearing25, and therefore the number of the component parts can be further reduced.

FIG. 2shows a second embodiment of the present invention. In this embodiment, those constituent portions, identical to those of the first embodiment, will be designated by identical reference numerals, respectively, and explanation thereof will be simplified.

In this embodiment, as shown inFIG. 2, a pair of wall portions43and45are formed on that side of a trunnion6having an inner surface6athereof, and-extend perpendicularly to the inner surface6ato form a pocket portion for receiving a power roller8. These wall portions43and45are interconnected by an interconnecting member47, and prevent the inner surface6aof the trunnion6from being deformed into a concave shape.

In this embodiment of the above construction, the deformation of the trunnion6is further suppressed, and therefore a power transmission loss of a thrust bearing26and a power transmission loss of a first radial bearing24, which are caused by the deformation of the trunnion6, can be further decreased, so that the power transmission efficiency of this toroidal-type continuously variable transmission can be further enhanced.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the above embodiments, although the first bottom plate portion40of the trunnion6is formed by an integral portion of the trunnion6, this bottom plate portion may be replaced by a separate member which closes the opening in the support hole23in the trunnion6. This can be applied similarly to the second bottom plate portion41of the power roller8.

In the above embodiments, the displacement shaft7and the outer ring30are formed integrally with each other, using one member, the displacement shaft7and the outer ring30may be separate from each other, in-which case the outer ring30is fixedly secured to the displacement shaft7to provide a unitary construction.

As described above, in the present invention, the power transmission loss of the thrust bearing and the power transmission loss of the first radial bearing, which are caused by the deformation of the trunnion, can be decreased. And besides, the power transmission loss of the thrust bearing, the power transmission loss of the second radial bearing and the loss of transmission of the power from the input disk to the output disk, which are caused by the deformation of the power roller, can be decreased. Furthermore, the power transmission loss of the thrust bearing due to the inclination of the displacement shaft can be reduced. Therefore, the power transmission can be smoothly effected at each of these portions, and therefore the power transmission efficiency of the toroidal-type continuously variable transmission can be enhanced. And besides, it is not necessary to increase the size of the trunnion and power roller in order to suppress the deformation of the trunnion and power roller, and therefore the compact design of the toroidal-type continuously variable transmission can be achieved.

The support hole and the insertion hole are closed by the first and second bottom plate portions, respectively, and therefore it is not necessary to provide retainer rings or the like which prevent the support shaft portion and pivot shaft portion of the displacement shaft from being withdrawn respectively from these holes. Therefore, the number of the component parts can be reduced, and besides assembling errors can be reduced. Furthermore, since the displacement shaft and the outer ring are formed integrally with each other, the processing of the fitting portions of the displacement shaft and outer ring does not need to be effected.

In the present invention, the wall portions of the trunnion are interconnected by the interconnecting member, and therefore the deformation of the trunnion can be further suppressed. Therefore, the power transmission loss of the thrust bearing and the power transmission loss of the first radial bearing, which are caused by the deformation of the trunnion, can be further decreased, and the power transmission efficiency of the toroidal-type continuously variable transmission can be further enhanced.

In the present invention, the stopper portion for preventing the movement of the second radial bearing is formed integrally on the displacement shaft, and therefore it is not necessary to provide a separate stopper member for preventing the movement of the second radial bearing, and therefore the number of the component parts can be further reduced.