Patent Application
20090076687
1. Field of the Invention
This invention relates to a position detection arrangement for a functional element which can be positioned motor-driven in a motor vehicle, a drive arrangement being coupled via a drive train to the functional element and the functional element thus being positionable by a motor, there being a measuring unit which is assigned to the drive train for detecting the position of the functional element, wherein the measuring unit comprises a sensor unit and a gearing with a drive side and a driven side, the drive side being assigned to the drive train and the driven side being assigned to the sensor unit. Furthermore the invention relates to a drive unit in a motor vehicle for a positionable functional element with a drive arrangement for motorized positioning of the functional element and a position detection arrangement for detecting the position of the functional element of the type indicated above. The invention also relates to a functional unit with above noted positionable functional element.
2. Description of Related Art
The expression “functional element which can be positioned” should be understood comprehensively here. Accordingly, it includes in general positioning elements in a motor vehicle as well as closure elements like a tailgate, a rear cover, a hood, a cargo space flap, a side door—also a sliding door—and a lifting roof of a motor vehicle. Furthermore windows, mirrors or vehicle seats which can be positioned by a motor are included.
In the course of increasing the comfort of modern motor vehicles, motorized positioning of functional elements, for example the tailgate of a motor vehicle, is acquiring increasing importance. For this purpose, there is a drive arrangement which is coupled via a drive train to the respective functional element.
A known drive arrangement for a tailgate (German utility model DE 20 2005 000 559 U1) has two spindle drives which are coupled, on the one hand, to the body of the motor vehicle, and on the other hand, to the tailgate. The two spindle drives are located on opposite sides of the tailgate.
Another known drive arrangement for a tailgate (German utility model DE 20 2004 016 543 U1 and corresponding US application 2006/0108959) is equipped with a push rod drive, the push rod being coupled to a deflection lever which is connected to the tailgate.
In these drive arrangements, the control of the motorized positioning of the functional element acquires special importance. For this purpose, there is a control means which, based on the absolute position of the functional element, sends suitable control signals to the drive arrangement. Here “absolute position” means an indication which provides information about the actual position of the functional element without further computation. In a tailgate this is, for example, an angle indication which is referenced to the part of the body which can not be positioned. In a broad sense an information about reaching one of the end of travel positions of the tailgate is also included in the expression “absolute position”.
It is apparent that the control of motorized positioning can only be as good as the position data present in the control means about the current absolute position of the functional element. The position detection arrangement under consideration is used to determine this position data.
The known position detecting arrangement (German patent application DE 101 45 711 B4 and corresponding U.S. Pat. No. 6,590,357) underlying the invention is equipped with two incremental rotary transducers. In this connection, one rotary transducer is used for detecting the position of the positionable functional element. This detecting takes place by counting the pulses produced by the incremental rotary transducer.
The second rotary transducer generates pulses which are offset in phase to the pulses of the first rotary transducer. The rotary transducer signals of the second rotary transducer are used solely for determining the current position direction of the functional element.
The problem of the known position detection arrangement is, first of all, the fact that the accuracy which can be achieved with pulse counting is comparatively low. In addition, the control engineering effort to implement it is comparatively high. Finally, in these systems problems often occur in an emergency, for example, when the voltage supply fails. If the absolute position of the functional element is specifically not stored, when the functional element is restarted, there is no longer any information about its absolute position. Then, complex referencing is necessary.
Furthermore, it is pointed out, that, for detection of the absolute position of the functional element, rotary transducers which are made as angle encoders are used. These angle encoders produce rotary transducer signals which are coded depending on the angular position and which, for themselves, provide information about the absolute position. These angle encoders are used as single-turn angle encoders and as multi-term angle encoders. In a single-term angle encoder, the rotary transducer signals periodically repeat after one complete revolution. In a multi-term angle encoder, there is coding of the absolute position over several turns.
The use of angle encoders is also known from the field of tailgates and rear covers of motor vehicles (German patent application DE 199 44 554 A1). The disadvantage in angle encoders is always the high costs. One example of this is shown by German patent DE 33 42 940 C2 and corresponding U.S. Pat. No. 4,712,088.
A primary object of the invention is to embody and develop the known position detection arrangement such that detection of the absolute position of the functional element can be achieved with high operating reliability and compact construction.
The aforementioned object is achieved in a position detection arrangement of the initially mentioned type in which the gearing of the measuring unit is constructed as a tumble gearing. Such tumble gearing can be constructed in a considerable compact design without leading to high costs. Also the gear ratio may easily extend the value of 1:50, which in the present case means, that 50 revolutions on the drive side of the tumble gearing lead to one revolution on the driven side of the tumble gearing. This again means that the sensor unit assigned to the driven side has only to be designed with a sensor range of one revolution while the range of movement of the respective element of the drive train may arbitrarily chosen.
The gear ratio of the proposed tumble gearing is provided by a special engagement between a tumbler gear with a ring gear, wherein the tumbler gear is realized as a spur gear being arranged within the ring gear and having an addendum circle diameter smaller than the addendum circle diameter of the ring gear. During movement of the functional element the tumbler gear is meshing with the ring gear while the tumbler gear is revolving around its geometrical axis and the geometrical axis of the tumbler gear is revolving around the geometrical axis of the ring gear. The advantage of this arrangement in view of installation space is the fact that all components are basically arranged around the geometrical axis of the ring gear.
The above noted constructional design is of special advantage when at least one drive of the drive arrangement is a spindle drive with a spindle-spindle-nut gear train and wherein the drive side of the tumble gearing is assigned to the spindle. This is especially true when the geometrical axis of the ring gear is aligned to the geometrical axis of the spindle such that the tumble gearing and the spindle-spindle-nut gear train may be arranged in series which leads to extraordinary advantages in view of installation space.
According to a second teaching which acquires independent importance, a drive unit for a positionable functional element is provided with the described drive arrangement for motorized positioning of the functional element and the described position detection arrangement for detecting the position of the functional element.
According to a third teaching which likewise acquires independent importance, a functional unit in a motor vehicle is provided with the described functional element, the described drive arrangement and the described position detection arrangement for detecting the position of the functional element.
The invention is explained in detail below with respect to the embodiments shown in the accompanying.
The position detection arrangement in accordance with the invention can be used for all possible functional elements 1, especially closure elements in a motor vehicle. For this purpose reference is made to the listing of applications in the introductory part of the description, the application to tailgates and side doors being emphasized. The drawings relate to the use of the position detection arrangement for a functional element 1 which is made as a tailgate. This should not be interpreted as limiting. All aspects pointed out in the following description concerning the tailgate 1 completely apply for all other functional elements 1 noted above.
The tailgate 1 shown in the drawings can be positioned motor-driven. For this a drive arrangement 2 is coupled via a drive train 3 to the tailgate 1 for enabling the tailgate 1 to be positioned by a motor 4.
In order to detect the absolute position of the tailgate 1 a position detection arrangement is proposed. Concerning the broad understanding of the expression “absolute position” reference is made to the general part of the description. For describing the proposed position detection arrangement only the left part of the drive arrangement 2 shown in
The position detection arrangement comprises a measuring unit 5 which is assigned to the drive train 3 for detecting the absolute position of the tailgate 1. The measuring unit 5 comprises a sensor unit 6 and a tumble gearing 7 with a drive side 7a and a driven side 7b. The drive side 7a is assigned to the drive train 3 and the driven side 7b is assigned to the sensor unit 6. The preferred coupling of the measuring unit 5 to the drive train 3 will be described at a later point.
The tumble gearing 7 provides a very compact arrangement. This is mainly because the gear ratio of the tumble gearing 7 is provided by a tumbler gear 8 realized as a spur gear being arranged within a ring gear 9, wherein the tumbler gear 8 has an addendum circle diameter smaller than the addendum circle diameter of the ring gear 9. This may be taken from
A movement of the tailgate 1 produces a movement of the tumbler gear 8 via the coupling between the drive train 3 and the measuring unit 5 to be discussed. During such movement of the tailgate 1 the tumbler gear 8 is meshing with the ring gear 9 while the tumbler gear 8 is turning around its geometrical axis 8a and while the geometrical axis 8a of the tumbler gear 8 is revolving around the geometrical axis 9a of the ring gear 9. How this tumbler movement of the tumbler gear 8 is realized will be discussed later on.
It has been pointed out already that the functional element 1 here is a closure element of a motor vehicle, preferably a tailgate 1 of a motor vehicle.
According to
According to the illustration in
The overall goal of integrating the tumble gearing 7 into the measuring unit 5 is to have a speed reduction concerning the angular speed on the drive side 7a and the angular speed on the driven side 7b of the tumble gearing 7. With an appropriate design of the tumbler gear 8 and the ring gear 9 it is then possible to use a sensor unit 6 which has a sensor range of less than 360°, which leads to low sensor costs.
There are a number of possible ways to realize the tumbler movement of the tumbler gear 8. According to a preferred embodiment the tumble gearing 7 comprises an eccentric 13 with a circular eccentric body 13a arranged eccentrically relative to a geometrical axis 13b of the eccentric 13, the geometrical axis 13b of the eccentric 13 being aligned to the geometrical axis 9a of the ring gear 9. The tumbler gear 8 now has a bore 14 rotatably receiving the eccentric body 13a. Simply spoken, the eccentric 13 holds the tumbler gear 8 in meshing engagement with the ring gear 9.
Various ways of operation of the tumble gearing 7 are possible. Preferably one of the eccentric 13, tumbler gear 8 and ring gear 9 is assigned to the drive train 3 of the tailgate 1, wherein another of the eccentric 13, tumbler gear 8 and ring gear 9 is assigned to the sensor unit 6. In the preferred embodiments shown in the drawings the eccentric 13 is assigned to the drive train 3 of the tailgate 1 and the tumbler gear 8 is assigned to the sensor unit 6.
Further it is preferred that one of the ring gear 9 and the eccentric 13 is fixedly arranged. In the preferred embodiments shown in the drawings the ring gear 9 is fixedly arranged. A robust and low cost solution for this fixedly arrangement is integrating the ring gear 9 into the housing 15 of the measuring unit 5.
It is apparent from
When the spindle is driven by the motor 4 to make a rotating movement the eccentric 13 follows this movement around its geometrical axis 13b. This forces the tumbler gear 8 to mesh with the ring gear 9 while rotating on the eccentric body 13a of the eccentric. This again causes the above noted revolving of the tumbler gear 8 around its geometrical axis 8a and also the revolving of the geometrical axis 8a of the tumbler gear 8 around the geometrical axis 9a of the ring gear 9.
When tracking one specific point at the circumference of the tumbler gear 8 it comes apparent that this point follows a path that is a superposition of a circle with a cycloid.
The above noted, quite complicated path in most cases leads to special requirements on the sensor unit. In one preferred embodiment, however, it leads to a rather simple structure of the sensor unit. This preferred embodiment is shown in
In
In the preferred embodiment shown in
It becomes clear from the above that the follower 8b is driven by the tumbler gear 8 but, in the end, makes a circular movement that is “easy to handle”.
According to
The preferred embodiment shown in
It is to be emphasized that realizing the sensor unit 6 as a simple switching unit may be applied to the construction shown in
The further preferred embodiments shown in
It is to be noted that the expression “sliding device” is to be understood in a broad sense. It does not only include an arrangement in which the sliding device actually contacts the sensor track 19. It also includes arrangements where the sliding device 20 is assigned to the sensor track 19 in a contact-free manner.
In the preferred embodiments shown in
One could also say that the design of the sensor track 19 in the embodiments shown in
It has been noted above that the realization of a follower 8b shown in
In those embodiments the resistive track 19 comprises an inner resistive track 19a and an outer resistive track 19b with respect to the geometrical axis 8a, 9a of one of the tumbler gear 8 and the ring gear 9. Which axis 8a, 9b is applicable here depends on whether the resistive track 19 is arranged on the tumbler gear 8 or is fixedly arranged. According to the existence of an inner resistive track 19a and an outer resistive track 19b in the preferred embodiments shown in
According to the preferred embodiments shown in
In order to allow a simple realization of the sliding device 20 it is preferred that the inner resistive track 19a and the outer resistive track 19b are arranged basically in parallel. This is shown in
In the preferred embodiments according to
Various alternatives for realizing the resistive track 19 are possible. For example it can be advantageous that one of the inner resistive track 19a and the outer resistive track 19b provides an open circuit and wherein the other one of the inner resistive track 19a and the outer resistive track 19b provides a closed circuit. This is shown in
It can also be advantageous that the inner resistive track 19a and the outer resistive track 19b as such provide open circuits. This is shown in
In the embodiments shown in
It may be pointed out that in the embodiments shown in
A different situation is shown in
It may be pointed out that the embodiment shown in
Another preferred realization of the above noted concept with sensor track 19 and sliding device 20 is shown in
First it is to be understood that the sensor signal produced by the hall sensor 20 differs with the hall sensor 20 coming out of perfect alignment with the magnetic track 19. Therefore the design of the magnetic track 19 preferably is a superposition of a spiral design with a cycloid-like design, such that the tumbler movement of the tumbler gear 8 is compensated and at the same time during movement of the tailgate 1 the hall sensor 20 continuously comes out of perfect alignment with the magnetic track 19. With this it is possible to detect the sliding device 20 on the magnetic track 19 based on the signals produced by the hall sensor 20. Accordingly the hall sensor 20 is again connected to the control unit 21.
In the preferred embodiment shown in
As a matter of clarification it may finally be pointed out that in all preferred embodiments shown in the drawings the drive side 7a of the tumble gearing 7 is provided by the eccentric 13 and the driven side 7b of the tumble gearing 7 is provided by the tumbler gear 8. It has been noted above that variations concerning the way of operation of the tumble gearing 7 are possible.
According to a second teaching which acquires independent importance, a drive unit for a positionable functional element 1 in a motor vehicle, comprising a drive arrangement 2 and a position detection arrangement is encompassed by the invention.
According to a third teaching which likewise acquires independent importance, moreover a functional unit in a motor vehicle with the described functional element 1, the described drive arrangement 2 and the described position detection arrangement is also encompassed by the invention.
All aforementioned statements on advantages and versions apply accordingly to the two other teachings. This applies especially to possible versions of the functional element 1 which were explained in the introductory part of the description.
