Headrest adjusting arrangement, particularly in a motor vehicle

A rear headrest adjusting arrangement in a motor vehicle has a headrest pivot bearing unit that is fixed at the seat and at which two head pad holding devices are disposed that are spaced away from one another in the direction of the pivotal axis. A pivot bearing shaft is provided that has two connecting parts for the holding devices, the connecting parts being spaced away from one another and being connected with the pivot bearing shaft in a torsionally fixed way. A driving motor is provided adjacent to the pivot bearing shaft, the driving motor having a motor shaft that with respect to its axis is parallel to the pivot bearing shaft and having a gearbox that connects the motor shaft with the pivot bearing shaft. This provides the possibility of a motor-driven headrest adjusting arrangement with little installation space for the pivot bearing unit.

BACKGROUND AND SUMMARY OF INVENTION 
The invention relates to a headrest adjusting arrangement, particularly of 
a rear headrest in a motor vehicle, having a headrest pivot bearing unit 
that is fixed at the seat. At this headrest pivot bearing unit, two head 
pad holding devices are disposed that are spaced away from one another in 
the direction of the pivotal axis. 
Rear headrests represent an important accident protection for the 
passengers in the rear seats. However, when the rear seats are unoccupied, 
the rear headrests represent an impairment of the driver's view toward the 
rear that in principle can be avoided. Both aspects are taken into account 
by the rear headrest adjusting arrangement of this type. Up to now, this 
headrest adjusting arrangement was operated manually. The disadvantage in 
this case is that for reasons of convenience, the headrest is often not 
swivelled into the correct position. 
It is an objective of the invention to provide a motor-operable rear 
headrest arrangement of a simple construction in which the driving unit 
requires only little installation space. 
This objective is achieved according to preferred embodiments of the 
invention by the fact that a pivot bearing shaft is provided having two 
connecting parts for the holding devices spaced away from another and 
connected with the pivot bearing shaft in a torsionally fixed way, that 
adjacent to the pivot bearing shaft, a driving motor is provided having a 
motor shaft that is parallel with respect to its axis to the pivot bearing 
shaft, and that a gearbox is provided that connects the motor shaft with 
the pivot bearing shaft. 
According to the invention, the driving motor, together with the gearbox, 
finds space between the two connecting parts for the holding hoops. The 
driving motor that is oblong in the direction of its motor shaft extends 
in parallel with respect to the axis next to the pivot bearing shaft so 
that the cross-sectional dimensions of the required installation space in 
a plane that is vertical or perpendicular with respect to the pivot 
bearing shaft axis are comparatively small. The whole pivot bearing unit 
with the pivot bearing shaft, the driving motor and the gearbox therefore 
easily find room in the possibly toroidally elevated area of the rear 
window shelf between its front edge and the head pad receiving trough that 
at least partially receives the head pad in its inoperative position. 
Without any special measures, the motor-driven rear headrest adjustment 
arrangement can therefore be installed instead of the manual rear headrest 
adjusting arrangement, or, if necessary, may be exchanged subsequently for 
the latter. The preferably one-piece gear shaft drives both holding hoops 
simultaneously. The mechanical construction is therefore reliable with 
respect to its operation. 
In a preferred further development of the invention, it is provided that 
the gearbox comprises a gear shaft having a worm segment into which a 
motor worm engages that, in a torsionally fixed way, is connected with the 
motor shaft, and having a worm segment which engages in a worm wheel 
element that, in a torsionally fixed way, is connected with the pivot 
bearing shaft. Thus, the driving motor is connected with the pivot bearing 
shaft via two individual worm wheel gears with the advantage of a 
correspondingly high step-down ratio which permits the use of a 
cost-effective fast-running driving motor of small dimensions and low 
weight. 
In a particularly preferred manner, the worm wheel element is developed in 
a sector shape. The required pivoting angle for the headrest adjustment 
that in general is below 180.degree. permits the reduction of the worm 
wheel element to a sector-shaped worm wheel element. Particularly 
advantageous is the resulting further reduction of the required 
installation space. 
It is also suggested according to certain preferred embodiments that the 
pivot bearing shaft have a non-circular cross-section, preferably without 
rotational symmetry. This facilitates the assembly and, if necessary, the 
disassembly of the pivot bearing unit for purposes of repair because the 
connecting parts as well as the worm wheel element that are provided with 
a passage opening corresponding to the cross-section of the pivot bearing 
shaft, must only be pushed onto the pivot bearing shaft. When a square 
shaft with a rotational symmetry of 90.degree. is used, for example, the 
possibility exists in principle that the elements to be pushed on may be 
pushed onto the shaft in correspondingly four different rotating 
positions. In order to exclude this during the mounting, it is suggested 
in certain preferred embodiments that the pivot bearing shaft have a 
cross-section without rotational symmetry. Particularly preferred is a 
pivot bearing shaft in the shape of a star shaped cross-section. A 
one-sided flattening of this star shaped cross-section will eliminate the 
rotational symmetry. 
In a further development of certain preferred embodiments of the invention, 
it is suggested that the pivot bearing shaft, at least at one end, is 
pivotally disposed in a bearing bush which, in turn, is inserted into a 
bearing opening of a bearing plate, in which case the bearing plate has a 
bearing bush insertion opening that leads into the bearing opening in a 
direction that is essentially perpendicular with respect to the pivot 
shaft axis. These measures permit an easy assembly, and, if necessary, 
disassembly of the pivot bearing shaft. In this case, it is preferably 
provided that the bearing bush has a circular section that is adapted to 
the circular bearing opening and has flattened areas that are opposite one 
another, in which case, the distance of the flattened areas from one 
another corresponds essentially to the width of the insertion opening. The 
mounting therefore takes place by rotating the bearing bush by about 
90.degree. after the insertion through the insertion opening into the 
bearing opening. 
It is suggested in certain preferred embodiments that a pivot bearing 
housing be provided, essentially in the shape of a hoop that is oblong in 
the direction of the pivot bearing shaft. The ends of this hoop are bent 
in the same direction for forming the bearing plates. In this case, it may 
be provided that the hoop is equipped with at least one laterally 
projecting fastening tab for the gear carrying the driving motor. The 
pivot bearing housing that is formed in this way may be formed by a 
corresponding sheet metal stamping which has compact dimensions, 
mechanically is sufficiently stable and requires low manufacturing costs. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
The diagrammatic representation of FIGS. 1 and 2 shows a head pad 10 
(outlined by a dash-dotted line) which is connected via a U-shaped hoop 12 
with a headrest pivot bearing unit that as a whole has the reference 
number 14, for a motor-driven movement between an inoperative position 16 
shown in FIG. 1 on the right and a head-supporting position 18. In the 
inoperative position 16, the head pad is essentially outside the rear view 
mirror viewing range of the vehicle driver. For this purpose, it is at 
least partially received by a head pad receiving trough 20 in a rear 
window shelf plate 22. The pivoting shaft 24 of the pivot bearing unit 14 
extends in the horizontal direction transversely to the driving direction 
in a trapezoidal-roof-like arching-out section 26 of a body panel 28 on 
which the plate 22 rests. The shaft 24, according to FIG. 1, is arranged 
in the area of the front edge of the rear window shelf plate 22 and is 
located higher than the bottom 30 of the trough 20. The two lateral legs 
of the hoop 12, in each case, form a holding device 32 for the head pad 
10. According to FIG. 1, each holding device, originating from the shaft 
24, extends first radially (section 32a), then along a graduated-circle 
arc at about 240.degree. (section 32b) and finally along a once-buckled 
section 32c into the inside of the pad 10 to the center leg 34 of the 
U-shape of the loop 12 according to FIG. 2. Because of this loop shape, 
only a relatively small passage opening 36 has to be provided in the plate 
22 and in the body panel 28. 
The construction of the pivot bearing unit 14 is shown in the figures. A 
continuous pivot bearing shaft 40, is disposed at a bearing plate 44 in 
the form of a bending-away of a pivot bearing housing 46 in the form of a 
sheet-metal stamping with the ends borne in respective bearing sleeves. 
Each bearing bush 42 is provided with a circumferential groove 47, the 
width of which corresponds to the sheet thickness of the bearing plate 44. 
The cross-section of the bearing bush in the area of this groove 47 is 
shown in FIG. 4. It is recognizable that the cross-section is circular 
with flattened areas 48 that are opposite one another. The diameter is 
adapted to the corresponding diameter of a bearing opening 50 of the 
bearing plate 44. Correspondingly, the distance between both flattened 
areas 48 is fixed corresponding to the width a of an insertion opening 52 
leading into the bearing opening 50. For the mounting of the shaft 40 at 
the housing 46, therefore, both bearing bushings 42 are first pushed onto 
the corresponding shaft ends and then the shaft in FIG. 4 is moved toward 
the housing 46 from below with bearing bushes that are rotated by 
90.degree. with respect to FIG. 4. In this position, both bearing bushes 
42, through the insertion openings 52, can be pushed into the circular 
bearing openings 50. Subsequently, both bearing bushes 42 are rotated by 
90.degree. into the position shown in FIG. 4 and in this way are fixed in 
the respective bearing opening. The bearing bush 42 that preferably 
consists of plastic, in this case, may be disposed in the bearing opening 
in such a way that special measures for a fixing of the rotating position 
of the bearing bush in the bearing opening are not necessary. 
As shown in detail in FIG. 5, each of the straight sections 32a of the two 
holding devices 32 is inserted into an insertion opening 56 of a 
connecting part 58 which, in turn, in a torsionally fixed way, is 
connected with the shaft 40. For this purpose, the shaft 40, at least in 
the area of its respective connecting part 58, is developed with a 
non-circular rotationally asymmetrical cross-section, in the shown case, 
in the shape of a star with a flattened area 60 on one side. This 
flattened area 60 provides that the two connecting pieces 58 as well as a 
worm element 62, that will be explained in detail below in conjunction 
with FIG. 6, can be pushed onto the shaft 40 only in a predetermined 
mutual orientation. A stop pin 64, shown in FIGS. 3 and 5, engages in a 
corresponding stop notch 66 of the section 32a in order to secure it in 
the respective connecting part 58. One respective pretensioning spring 
clip 68, shown in FIGS. 3 and 5, prestresses the stop pin 64 that can be 
shifted in the connecting part 58, into its engaging position. A release 
lever 70, shown in FIGS. 3 and 5, permits a release of the locking. For 
this purpose, it is applied to a section 72 of the spring 68 that 
transversely penetrates the pin 64. 
FIG. 5 also shows a damping stop 74 that is fastened at the housing 46 and 
against which the connecting part 58 strikes in the head-supporting 
position 18 of the head pad 10. With respect to the two bearing bushes 42, 
it should be pointed out that these, at their end located outside the 
housing 46, are again provided with two flattened areas 76 that are 
opposite one another for the application of a corresponding tool, such as 
a wrench. 
The pivot bearing unit 14 is driven by a driving motor 80, particularly an 
electric motor. This electric motor, via a connecting piece 82, is 
connected with a gearbox 86 by means of screws 84 depicted in FIG. 3. This 
gearbox 86, in turn, by means of cap screws 88, is fastened at fastening 
tabs 90 of the housing 46. The fastening tabs 90 project at sides of the 
longitudinal loop-shaped section 92 of the housing 26 that are opposite 
one another, the two ends of said housing being bent away for forming the 
bearing plates 44 according to FIG. 2. 
The construction of the gearbox 86 is shown in FIGS. 6 to 8. It has a gear 
housing 94 with a housing cover 96 and cap screws 98 that connect both 
parts. In the gear housing 94, a gear shaft 100 is rotationally disposed, 
in which case the axis 102 is located in a plane that is perpendicular 
with respect to the axis 24. The axis 104 of a motor shaft 106 of the 
driving motor 80 extends in parallel to the axis 24. 
The gear shaft 100 connects the motor shaft 106 directly with the pivot 
bearing shaft 40. For this purpose, the gear shaft 100 is provided with a 
worm wheel segment 108, that mates with a motor worm 110 developed at the 
motor shaft 106. The gear shaft 100 is also developed with a worm segment 
112 which mates with the above-mentioned sector-shaped worm wheel element 
62. The gear 86 therefore represents a two-step worm gear with a step-down 
ratio of, for example, i=110. 
The gear shaft 100 is rotationally supported between the worm wheel segment 
108 at one of its two ends and the worm segment 112 in a first pivot 
bearing 114, and on the other side of the worm segment 112, in a second 
pivot bearing 116. Both pivot bearings 114 and 116, as plastic parts, may 
be developed in one piece with the cover 96 of the gear 86. 
Corresponding to the required pivot angle of the head pad 10 between its 
two positions 16 and 18 in FIG. 1 (pivot angle about 120.degree.), the 
sector angle of the worm wheel element 62 is fixed at about 130.degree., 
which results in a sector angle of about 250.degree. for a corresponding 
sector-shaped recess 120 inside the housing 94. The recess 120 is oriented 
in such a way that the sector of the worm wheel element 62 moves mainly in 
an area below the axis 24 so that the top side 122 of the housing can be 
disposed correspondingly close to the axis 24. As shown particularly in 
FIGS. 4 and 6, an extremely compact structural shape is obtained in which 
the axes 104 and 24 of the motor shaft 106 and of the pivot bearing shaft 
40 are located close to one another. 
In the area between the gearbox 94 and the farther connection piece 58 (in 
FIG. 3, on the bottom), the pivot bearing shaft 40 is guided in a 
protective sleeve 130. 
The above-described rear headrest adjusting arrangement distinguishes 
itself mainly because of the fact that the adjustment of the headrest 
takes places by means of a motor. In this case, only little installation 
space is required for the pivot bearing unit 14, so that the installation 
of the motor-driven rear headrest adjusting arrangement according to the 
invention is possible without changing the body in vehicles that are 
prepared for a manual rear headrest adjusting arrangement. A subsequent 
converting from a manual rear headrest adjusting arrangement to the 
structural shape according to the invention is also possible. 
Advantageously, the manufacturing and mounting costs are low. The high 
step-down ratio permits the use of a compact, light, fast-running electric 
motor. 
The control of the electric motor 80 may take place manually or 
automatically. As outlined in FIG. 2, for this purpose, a control unit 140 
by means of a control line 142 is connected with the driving motor 80. The 
control unit 140, via a line 144, is connected with a manual switch that 
is not shown. Additional lines 146 connect the control unit 140 with the 
seat contacts that are not shown. As soon as one of the two rear seats is 
occupied, a signal, via the corresponding line 146, is supplied to the 
control unit 140 which then, via the line 142, causes the driving motor 80 
to swivel the pad 10 into the head supporting position 18 according to 
FIG. 1. As soon as the seat becomes vacant again, the control unit 140 
causes a swivelling-back of the head pad 10 into the inoperative position 
16. By means of corresponding end contacts that are not shown, it can be 
ensured that the driving motor 80 will not be switched off before the 
respecitve position 16 or 18 of the head rest 10 is reached. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, and is not to be taken by way of 
limitation. The spirit and scope of the present invention are to be 
limited only by the terms of the appended claims.