System for obtaining position of linear unit of linear system

Abstract

A system (1) for obtaining a position of a linear unit (10) of a linear system (6), where the linear system (6) has an engine (2), where the engine (2) is designed to drive the linear unit (10) to achieve a linear motion, where the system (1) has an absolute rotary encoder (20, 22) connected to the engine (2), where the absolute rotary encoder (20, 22) is designed to determine a position of the linear unit (10). Wherein the absolute rotary encoder (20, 22) is designed to obtain the position of the linear unit (10) on the basis of the movement of the engine (2).

Description

[0001] This application is a divisional application of an application with a filing date of August 12, 2019, application number 201910741567.7, and invention name “System for Obtaining the Position of a Linear Unit of a Linear System”. Technical Field

[0002] The invention relates to a system for determining the position of a linear unit of a linear system or a linear actuator, wherein the linear system has a motor and wherein the motor is designed to drive the linear unit in order to achieve a linear movement. Background Art

[0003] In many technical systems, linear actuators or telescopic rods are used to achieve linear movements. Electric linear actuators usually consist of a motor and a transmission driven by the motor, which applies a rotational movement to a conversion element, wherein the conversion element converts the rotational movement into a linear movement. The conversion element is, for example, a shaft, a chain, a belt or a rack.

[0004] For example, feedback related to the position of a linear actuator may be required in order to electrically limit the mechanical travel of the linear actuator, thereby enabling precise positioning or providing other systems with information about the current position of the linear actuator. Up to now, such position feedback has generally been obtained by means of incremental encoders, so-called incremental encoders. However, such systems are cost-intensive and require a large number of components, which are therefore very expensive. For example, incremental encoders usually require two sensors, a computing unit and a backup unit. During the movement of the linear unit, the two sensors emit two electrical signals with a 90° phase shift, from which the path distance and path direction of the linear unit can be obtained. Based on the path distance and path direction, the computing unit can determine the position of the linear unit. During the shutdown period or during a power failure, the current position information can be lost. To avoid this, the backup unit can store the current position information. However, the incremental encoder may have to be referenced again after switching on, because the change in position cannot be obtained in the switched-off state. Summary of the invention

[0005] It is therefore an object of the present invention to be able to determine the position of a linear unit of a linear system in a simple and safe manner.

[0006] This object is achieved by a system according to the invention for determining the position of a linear unit of a linear system. A linear actuator has a motor, wherein the motor is designed to drive the linear unit directly or indirectly in order to achieve a linear movement.

[0007] In contrast to known systems, the proposed system uses an absolute rotary encoder which is directly or indirectly connected to the motor and is designed to determine the position of the linear unit based on the movement of the motor. An absolute rotary encoder, which is also called an absolute value encoder, provides position information in the form of a digital value. This digital value is unique over the entire resolution range of the absolute rotary encoder, which is why an initial reference is not required (as was required with the incremental encoders used until now).

[0008] By using an absolute rotary encoder, it is also possible to retain the position of the linear unit in the event of a power failure or a switch-off. After switching on again, the absolute rotary encoder does not need to be referenced again. In addition, a memory unit (as required by the incremental rotary encoders used until now) can be omitted. Furthermore, since the absolute rotary encoder does not have to be referenced again and again all the time, the time for setting up and maintenance can be reduced. Furthermore, the reliability of the position of the linear unit can be significantly improved thereby.

[0009] A rotary encoder (or rotary angle encoder or encoder) is understood to be a sensor of the angle of rotation which delivers an output signal to be decoded in an evaluation device. An absolute rotary encoder or absolute value encoder (as used here) delivers position information in the form of a digital value. This position information can be related to position information of the engine or to position information of a transmission connected to the engine and thus indirectly to the position of the linear unit. Since this digital value is unique over the entire resolution range of the absolute rotary encoder, an initial referencing process is not required, for example, for incremental encoders. Depending on the implementation, an absolute rotary encoder may only be able to resolve one revolution and then restart from 0, or it may be able to resolve multiple revolutions.

[0010] The linear system may be a nut-spindle system, which can be used, for example, in an actuator of a lifting column or in a linear module. In addition, the linear system can be any type of linear actuator, by means of which the movement of the motor can be converted into the movement of the linear unit.

[0011] According to one embodiment, the linear system has a transmission driven by a motor, wherein the motor is designed to drive the linear unit via the transmission. In this case, the absolute rotary encoder is connected to the motor via the transmission.

[0012] According to one embodiment, the absolute rotary encoder is a multi-turn absolute rotary encoder, which is able to resolve multiple rotations. In this case, the absolute rotation within one rotation and the number of rotations can also be determined. This means that a coded position value can be assigned to each angular value and each complete rotation of the transmission by means of a multi-turn absolute rotary encoder. Thus, the zero position (Nullstellung) or reference can be omitted. In this case, the absolute rotary encoder generates information about the position, angle and number of rotations of the transmission.

[0013] In another embodiment, the absolute rotary encoder may include a first and a second single-turn absolute rotary encoder. In a single-turn implementation, the absolute rotary encoder measures the absolute rotation within one rotation. By using two single-turn absolute rotary encoders, a multi-turn absolute rotary encoder can be realized in a simple manner.

[0014] The positions of the two single-turn absolute rotary encoders are driven by means of a transmission via a slight reduction difference. This difference results in an increase in the difference between the two angles of the two single-turn absolute rotary encoders with each rotation. The difference between the two angles, after calculation, yields the number of revolutions and, from this, the total angle of multiple revolutions (multiple turns).

[0015] Furthermore, a multi-turn encoder can also be implemented, for example, by using: a potentiometer; a single-turn absolute rotary encoder combined with a rotation counter and a memory; a single-turn absolute rotary encoder combined with a rotation counter and a battery; an incremental encoder combined with a pedometer and a memory; or an incremental encoder combined with a pedometer and a battery.

[0016] The absolute rotary encoder can be connected to the engine or the transmission via at least a first and a second gear. In one embodiment, these gears can also be directly integrated into the transmission. In particular, the first single-turn absolute rotary encoder is connected to the first gear and the second single-turn absolute rotary encoder is connected to the second gear. Via the two gears, the movement of the engine or the transmission is transmitted to the two single-turn absolute rotary encoders respectively. The movement of the gears is thus directly linked to the movement of the linear unit.

[0017] The first gear can have a first toothing and the second gear can have a second toothing. Preferably, the difference between the number of teeth of the first toothing (N1) and the number of teeth of the second toothing (N2) is between 1 and 5, in particular between 1 and 2. The difference between N1 and N2 is preferably only one tooth, but can also be larger if the number of teeth of N1 is very large. With such a small difference in the number of teeth, very small transmission ratios can be achieved. The difference between the angles of the first and second gear wheels obtained is calculated, wherein the difference changes very slowly due to small differences in the number of teeth.

[0018] Compared to the need for high mechanical transmission ratio The use of two single-turn absolute rotary encoders with two gears with a low transmission ratio can reduce the space requirement compared to other implementations of a multi-turn absolute rotary encoder. In addition, such an implementation can also reduce costs compared to other implementations of a multi-turn absolute rotary encoder due to the smaller space requirement and the smaller number of teeth.

[0019] According to one embodiment, the engine or transmission with the first and second gears is coupled to the third toothing (N3) via a third gear. The coupling device of the engine or transmission and the absolute rotary encoder is realized by three gears. In one embodiment, the coupling device can also be integrated in the transmission. The transmission ratio between the first and third gears is R1=N3 / N1, and the transmission ratio between the second and third gears is R2=N3 / N2.

[0020] The transmission ratio of the coupling device is then R=R1-R2=N3 / N1-N3 / N2.

[0021] Taking the difference in the number of teeth as 1, that is, N2 = N1 + 1, the above equation is: R = N3 / (N1 2 +N1).

[0022] As an example, it is assumed below that the teeth are: N1=30, N2=31 and N3=10.

[0023] Therefore, the transmission ratio relationship R1=10 / 30=1 / 3 and R2=10 / 31. Therefore, the transmission ratio relationship of the coupling device is R=10 / (30 2 +30)=1 / 93.

[0024] In this example, a coupling device with a transmission ratio of 1 / 93 is realized by a simple method with two simple gears with a transmission ratio relationship of 1 / 3. Thus, using the system proposed by the invention, it is possible to resolve multiple rotations of the transmission (and thus a larger range of motion of the linear unit) without requiring a high transmission ratio of the coupling device between the transmission and the absolute rotary encoder. This also results in a smaller space requirement and thus the above-mentioned advantages.

[0025] According to one embodiment, the absolute rotary encoder can be designed to detect the movement of the motor or the transmission by means of a capacitive, magnetic, inductive and / or optical coupling device.

[0026] For an optical coupling device, a gear with a plurality of code tracks can be provided, which can be scanned in parallel by means of an optical element. For a magnetic coupling device, a magnet can be provided on the gear, which can be obtained by means of an absolute rotary encoder during the rotation of the gear by means of a magnetic coupling device. In order to obtain a capacitive coupling device, electrodes can be provided on the gear and on the absolute rotary encoder, wherein the capacitance changes when the electrodes rotate relative to each other. The angular position can be determined based on this capacitance change. In a similar manner, an inductive coupling device can be realized and the inductance can be changed thereby.

[0027] Preferably, the absolute rotary encoder is connected to the gears (eg first and second gears) via a capacitive or inductive coupling, which results in the movement of the transmission. Compared to optical or magnetic measurements, the use of capacitive or inductive measurements is particularly cost-effective.

[0028] As described above, the absolute rotary encoder can be used to obtain the rotation of the transmission by means of the angular position of the gear. In order to convert the obtained movement of the transmission into the position of the linear unit, according to another embodiment, the system has a calculation unit. The calculation unit can, for example, realize the conversion of the movement of the transmission into the position of the linear unit based on stored values.

[0029] In particular, the absolute rotary encoder can determine the angular positions of the first and second gears, and the calculation unit can convert these angular positions into the position of the linear unit. In this case, for each angular position or each angular position combination of the two gears, a linear unit position can be stored. In one embodiment, the calculation unit can also determine and store the corresponding angular positions of the two gears for the zero point of the linear unit, that is to say in the fully retracted or fully extended state of the linear unit. Subsequently, the angular position change caused by the movement of the linear unit can be recognized and calculated in the calculation unit as a position change of the linear unit accordingly.

[0030] Other advantages and advantageous embodiments are given in the present specification, drawings and claims. In particular, the combinations of technical features given in the specification and drawings are purely exemplary, and therefore, these technical features may also exist alone or in combination in other ways. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In the following, the present invention is described in detail according to the embodiments shown in the accompanying drawings. Here, the embodiments and the combinations shown in the embodiments are purely exemplary and should not limit the scope of protection of the present invention. The scope of protection is defined only by the attached claims.

[0033] Shown in the accompanying drawings are:

[0034] Figure 1 : A linear actuator with a system for obtaining the position of a linear unit;

[0035] Figure 2 : Figure 1 A first embodiment of a system for obtaining a position of a linear unit;

[0036] Figure 3 : Figure 1 A second embodiment of the system for obtaining the position of a linear unit;

[0037] Figure 4 : Figure 1 A third embodiment of a system for obtaining a position of a linear unit.

[0038] In the following, identical or functionally identical elements are denoted by the same reference numerals.

[0039] Reference numerals list

[0040] 1 System

[0041] 2 Engine

[0042] 4 Transmission

[0043] 6 Actuator

[0044] 8 Axis

[0045] 10 Linear Units

[0046] 12 Position determination unit

[0047] 14 First Gear

[0048] 16 Second gear

[0049] 18 Third gear

[0050] 20 Absolute rotary encoder

[0051] 22 Absolute rotary encoder

[0052] 24 Computational Units DETAILED DESCRIPTION

[0053] Figure 1A system 1 for obtaining the position of a linear unit 10 of a linear system, here a linear actuator 6, is shown. A motor 2 is coupled to a transmission 4, which drives the linear actuator 6. Alternatively, the motor 2 can also be coupled directly to the linear actuator 6. In this case, the linear actuator 6 consists of a shaft 8 and a linear unit 10. The transmission 4 causes the shaft 8 to perform a rotational movement, which the shaft 8 converts into a linear movement of the linear unit 10. Instead of the shaft 8, any other form of conversion element, such as a belt or a gear, can also be used.

[0054] Furthermore, the transmission 4 is connected to absolute rotary encoders 20, 22 via a position determination unit 12. The position determination unit 12 can be formed integrally with the transmission 4 as a transmission train or as a coupling device between the transmission and the absolute rotary encoders 20, 22.

[0055] The absolute rotary encoders 20, 22 in this case can be two single-turn absolute rotary encoders 20, 22. The position of the linear unit 10 can be determined by coupling the transmission 4 to the absolute rotary encoders 20, 22. This position can be used to electrically define the mechanical travel of the linear actuator 6, thereby enabling precise positioning or providing information about the current position of the linear actuator 6 to other systems.

[0056] In the embodiment shown here, the position determination unit 12 for coupling the transmission 4 with the absolute rotary encoders 20, 22 consists of three gears 14, 16, 18, wherein the first gear 14 is coupled to the first single-turn absolute rotary encoder 20 and the second gear 16 is coupled to the second single-turn absolute rotary encoder 22. The transmission 4 itself drives the third gear 18, which rotates the other two gears 14, 16. The third gear 18 can be moved directly in relation to the shaft 8. The two single-turn absolute rotary encoders 20, 22 detect the angular positions of the two gears 14, 16 (for example, via a capacitive coupling). These angular positions correspond to the positions of the linear unit 10, respectively, so that they can be accurately determined by the absolute rotary encoders 20, 22.

[0057] exist Figures 2 to 4 Three exemplary implementations of the position determination unit 12 are shown in FIG. 1 , wherein other implementations are also possible.

[0058] Figure 2 Shows Figure 1Schematic diagram of an embodiment of a position determination unit 12. Therein, the position determination unit 12 is also composed of three gears 14, 16, 18, wherein the first gear 14 is coupled to a first single-turn absolute rotary encoder 20 and the second gear 16 is coupled to a second single-turn absolute rotary encoder 22. The transmission 4 itself drives a third gear 18, which is arranged between the other two gears 14, 16 and causes these two gears to rotate respectively.

[0059] Two single-turn absolute rotary encoders 20, 22 detect the angular position of the first or second gear wheel 14, 16 respectively and transmit it to a calculation unit 24. The calculation unit 24 can then convert these angular positions into the position of the linear unit 10.

[0060] Apart from Figure 2 In addition to the arrangement in FIG. 1 , the third gear 18 may also be coupled to only one of the gears 14 and 16, such as Figure 3 In this case, the transmission 4 is coupled to the third gear 18, and the rotation of the third gear 18 causes the first gear 14 to rotate. Since these gears are meshed with each other, the rotation of the first gear 14 is transmitted to the rotation of the second gear 16.

[0061] like Figure 4 As shown, it is also possible to use only two gears 14, 16 for the position determination unit 12. In this figure, the transmission 4 is directly coupled to the first gear 14, which transmits its rotation to the second gear 16. In this case, two single-turn absolute rotary encoders 20, 22 are also coupled to the gears 14, 16 and detect their angular position.

[0062] In the embodiment shown above, the absolute rotary encoder is formed by two single-turn absolute rotary encoders 20, 22. In addition, other implementations of absolute rotary encoders can also be used, such as a multi-turn absolute rotary encoder or more than two single-turn absolute rotary encoders.

[0063] The above-described system makes it possible to maintain the position of the linear unit even in the event of a power failure or switch-off, since an absolute rotary encoder is used which does not require any new references when switching back on.

Claims

1. A system (1) for obtaining the position of a linear unit (10) of a linear system (6), wherein: The linear system (6) has: - a motor (2) designed to drive the linear unit (10) to achieve a linear movement, a multi-turn absolute rotary encoder having a first single-turn absolute rotary encoder and a second single-turn absolute rotary encoder (20, 22) and connected to the motor (2), wherein the multi-turn absolute rotary encoder is designed to obtain the position of the linear unit (10) based on the movement of the motor (2), a transmission (4) driven by the motor (2), wherein the motor (2) is designed to drive the linear unit (10) via the transmission (4), and wherein the multi-turn absolute rotary encoder is connected to the motor (2) via the transmission (4), - a position confirmation unit (12), the multi-turn absolute rotary encoder being connected to the transmission (4) by means of the position confirmation unit (12), wherein the position confirmation unit (12) comprises a first gear (14) connected to the first single-turn absolute rotary encoder (20) and a second gear (16) connected to the second single-turn absolute rotary encoder (22), and is integrally formed with the transmission (4) to form a transmission circuit.

2. The system (1) of claim 1, wherein the first gear (14) comprises a first toothing (N1), and the second gear (16) comprises a second toothing (N2), wherein: The difference between the number of teeth of the first tooth portion (N1) and the number of teeth of the second tooth portion (N2) is equal to 1.

3. The system (1) as claimed in claim 1 or 2, wherein the multi-turn absolute rotary encoder is designed to obtain the movement of the motor (2) by means of a capacitive coupling device or an inductive coupling device.

4. The system (1) according to claim 3, wherein: The first single-turn absolute rotary encoder (20) is capacitively or inductively connected to the first gear (14), and the second single-turn absolute rotary encoder (22) is capacitively or inductively connected to the second gear (16).

5. The system (1) according to claim 4, wherein: In order to realize a capacitive or inductive coupling device at the first gear wheel (14) and the second gear wheel (16) and at the first single-turn absolute rotary encoder (20) and the second single-turn absolute rotary encoder (22), electrodes are provided, wherein the capacitance or inductance changes when the electrodes are rotated relative to each other.

6. A system (1) as claimed in any one of the preceding claims, comprising a calculation unit (24) designed to convert the movement of the motor (2) obtained by the multi-turn absolute rotary encoder into a position of the linear unit (10) based on stored values.

7. A system (1) as claimed in any one of the preceding claims, wherein: The absolute rotary encoder outputs position information of the linear unit (10) in the form of a digital value which is unique over the entire resolution range of the absolute rotary encoder.

8. The system (1) as claimed in any one of the preceding claims, wherein: The multi-turn absolute rotary encoder generates information about the position, angle and number of revolutions of the transmission (4).

9. The system (1) as claimed in any one of the preceding claims, wherein: The positions of the first single-turn absolute rotary encoder (20) and the second single-turn absolute rotary encoder (22) are driven by means of the transmission (4) through a small reduction difference, so that the difference between the two angles of the two single-turn absolute rotary encoders (20, 22) changes with each rotation.

10. The system (1) as claimed in any one of the preceding claims, wherein: The engine (2) having the first gear (14) and / or the second gear (16) is coupled to the third gear portion (N3) via a third gear (18).

11. The system (1) as claimed in claim 10, wherein: The difference between the number of teeth of the first tooth portion (N1) of the first gear (14) and the number of teeth of the second tooth portion (N2) of the second gear (16) is equal to 20 or 21.

12. The system (1) according to claim 10 or 11, wherein: The transmission ratio between the engine (2) and the first gear (14) and / or the second gear (16) is equal to 1:

93.

13. The system (1) according to any one of claims 10 to 12, wherein: The third gear (18) is integrated into the transmission (4) and drives the first gear (14) and the second gear (16).

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