ELECTRIC MOTOR WITH ROTARY ENCODER

Abstract

An electric motor with a motor shaft, a motor pinion and a sensor element for an optical rotary encoder which has at least one recess for the transmission of a light beam from the optical rotary encoder. The motor shaft, the motor pinion and the sensing element being integrally formed with one another and being coupled with the motor shaft in a rotationally fixed manner. Further, the sensor element has a drum-shaped design and is aligned coaxially with the motor pinion. The recess is formed in the sensor element in such a way that the light beam of the rotary encoder can pass radially relative to a rotational axis of the sensor element. The invention also relates to a medical device with such an electric motor.

Claims

1. An electric motor comprising: a motor shaft; a motor pinion attached to the motor shaft; an optical rotary encoder having a light beam; a sensor element for use with the optical rotary encoder, the sensor element secured to the motor shaft and having at least one recess for the transmission of the light beam from the optical rotary encoder; and means for integrally forming the motor pinion and the sensing element with one another and being coupled with the motor shaft in a rotationally fixed manner, wherein the sensor element is drum-shaped and is aligned coaxially with the motor pinion and the at least one recess is formed in the sensor element in such a way that the light beam of the rotary encoder can pass radially relative to a rotational axis of the sensor element.

2. The electric motor according to claim 1, wherein the motor pinion is arranged between the sensor element and a motor housing.

3. The electric motor according to claim 1, wherein the sensor element extends longitudinally beyond the motor shaft.

4. The electric motor according to claim 1, wherein the recess is defined by two material segments for shadowing the light beam of the rotary encoder.

5. The electric motor according to claim 4, wherein the two material segments extend parallel to a rotational axis of the sensor element and define two recesses which are formed by a groove that extends radially and completely through the sensor element.

6. The electric motor according to claim 5, wherein each of the two material segments has a cylindrical segment-shaped outer surface and a flat inner surface, the inner surfaces of the material segments being arranged parallel to each other and delimiting the groove.

7. The electric motor according to claim 4, wherein the sensor element is a hollow cylindrical shape, and wherein the material segments have a uniform wall thickness and define at least two recesses.

8. The electric motor according to claim 7, wherein the number of recesses is three.

9. The electric motor according to claim 1, wherein the motor pinion and the sensor element are designed as a one-piece, injection-molded part.

10. The electric motor according to claim 4, wherein the rotary encoder with the light source also includes a light receiver, and wherein the sensor element is arranged between the light source and the light receiver in such a way that a direct light beam can be projected between the light source and the light receiver via the at least one recess and be shaded by the material segments.

11. The electric motor according to claim 10, wherein the light beam is aligned radially with respect to the longitudinal axis of the sensor element.

12. The electric motor according to claim 10, wherein the light source and the light receiver are arranged radially opposite the sensor element.

13. The electric motor according to claim 10, wherein the light source is radially arranged inside the sensor element, and the light receiver is radially arranged outside the sensor element.

14. The electric motor according to claim 10, wherein the light receiver is radially arranged inside the sensor element, and the light source is radially arranged outside the sensor element.

15. The electric motor according to claim 10 further comprising a sensor circuit board axially spaced from the sensor element and wherein the light source and the light receiver are mounted on the sensor circuit board.

16. The electric motor according to claim 1, further comprising at least two rotary encoders, each forming a light barrier; the light barriers being offset by an angle off the longitudinal axis of the sensor element which is not equal to 180 degrees.

17. The electric motor according to claim 10, further comprising at least two rotary encoders, each forming a light barrier; the light barriers being offset by an angle off the longitudinal axis of the sensor element which is not equal to 180 degrees.

18. A syringe pump or infusion pump with an electric motor according to claim 1.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0021] The invention is better understood by reading the following Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals refer to like elements throughout, and in which:

[0022] FIG. 1 shows a perspective view of an electric motor according to the invention and to a first preferred embodiment;

[0023] FIG. 2 is a perspective view of the electric motor according to FIG. 1 with a rotary encoder;

[0024] FIG. 3 is a side view of the electric motor according to FIG. 2;

[0025] FIG. 4 shows a perspective view of an electric motor with a rotary encoder according to a second preferred exemplary embodiment with an alternative configuration of the sensor element;

[0026] FIG. 5 is a side view of the electric motor according to FIG. 4;

[0027] FIG. 6 is a cross-sectional view through a part of a syringe pump with the electric motor according to FIG. 4;

[0028] FIG. 7 shows a cross-sectional view through a part of an electric motor according to a third preferred embodiment, the sensor element completely projecting into a rotary encoder; and

[0029] FIG. 8 shows a cross-sectional view of a part of an electric motor according to a further preferred embodiment with an alternative design of the motor pinion and sensor element.

[0030] The attached drawings show a total of four different embodiments of the invention. The symbols referring to the individual exemplary embodiments have a different number of prime marks in them. FIGS. 1 to 3 show a first exemplary embodiment, FIGS. 4 to 6 show a second exemplary embodiment, FIG. 7 shows a third exemplary embodiment, and FIG. 8 shows a fourth exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0031] In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

[0032] An electric motor 1, which has a motor housing 13, is common to all exemplary embodiments. A motor shaft 4, on which a motor pinion 2 is seated, projects axially from the motor housing. The motor pinion 2 is integrally connected to a sensor element 3, the sensor element 3 being of a drum-shaped design. In particular, the sensor element 3 has a cylindrical outer peripheral surface. In all exemplary embodiments, the sensor element 3 is aligned coaxially with the motor pinion 2. In particular, the motor pinion and the sensing element are integrally formed with one another, preferably as a single injection-molded part.

[0033] The sensor element has at least one recess 5, which forms a passage for a light beam 11 of a rotary encoder 7 (See FIGS. 7 and 8 for schematic representations of a light beam arrangement found in all embodiments of a rotary encoder). In the first exemplary embodiment, it can be clearly seen in FIG. 1 that the sensor element 3 is essentially hollow-cylindrical. In particular, the sensor element 3 has material segments 12, which in each case delimit recesses 5. The material segments 12 are curved. Specifically, the material segments 12 follow the hollow cylinder shape of the sensor element 3. The material segments 12 have a uniform wall thickness.

[0034] The motor pinion 2, which is connected in a rotationally fixed manner to the motor shaft 4, integrally adjoins the sensor element 3. The motor shaft 4 preferably terminates in the region of a bottom surface of the sensor element 3. In particular, the sensor element 3 extends longitudinally beyond the motor shaft 4. In this respect, the motor pinion 2 is arranged between the sensor element 3 and the motor housing 13.

[0035] In the case of the first exemplary embodiment, the sensor element 3 has four recesses, which are each offset at an angle of 90 degrees to each other. The recesses 5 have a uniform width. Furthermore, the recesses 5 are uniformly spaced from each other. In other words, the material segments 2 also have a uniform width. In this way, the recesses 5 are arranged such that in each case two recesses 5 are arranged radially opposite one another. Radiality refers to the longitudinal axis of the motor shaft 4, i.e., the rotational axis of the electric motor 1.

[0036] As can be clearly seen in FIG. 2, the electric motor 1 also has an encoder with a sensor circuit board 6, two rotary encoders 7 being arranged on the sensor circuit board 6. The rotary encoders 7 each form a light barrier. For this purpose, each rotary encoder 7 has a light source 9 and a light receiver 10 (See FIGS. 7 and 8 for a schematic representation of light source 9 and light receiver 10 found in all examples of the rotary encoders 7). A light beam 11 can be activated between the light source 9 and the light receiver 10 and be temporarily interrupted by the sensor element 3 when the electric motor 1 is rotated. In particular, the material segments 12 provide for an interruption of the light beam 11, whereas the recesses 5 allow the light beam 11 to pass.

[0037] In the first exemplary embodiment, it is provided that the rotary encoders 7 are arranged such that in each case a light-barrier element, respectively the light source 9 or the light receiver 10, engages with the sensor element 3. In particular, a light-emitting element is arranged radially inside the sensor element 3, whereas a different light-receiving element is arranged radially outside the sensor element 3. Both rotary encoders 7 are arranged on the common sensor circuit board 6, which is positioned axially spaced from the sensor element 3. The sensor circuit board 6 is essentially coaxial with the motor housing 3.

[0038] The arrangement of the rotary encoders 7 with respect to the sensor element 3 is clearly shown in FIG. 3. It can also be seen that, in the first exemplary embodiment, the sensor element 3 has a cross-sectional diameter that is smaller than the cross-sectional diameter of the motor pinion 2. Thus, a particularly compact construction is achieved, in particular with regard to the radial structural space.

[0039] FIG. 2 also clearly shows that the two light barriers, which are formed by the two rotary encoders 7, are aligned at an angle to one another. The light barriers are thus positioned in such a way that their light beams 11 assume an angle which is not equal to 180 degrees or to 90 degrees. In this respect, the light barriers are arranged at an acute angle to one another. Thereby, rotational direction detection can be implemented.

[0040] FIGS. 4 to 6 show a second exemplary embodiment of the invention, which differs from the first exemplary embodiment in the design of the sensor element 3′. The remaining components are essentially identical. Thus, in the second exemplary embodiment, the electric motor 1′ also has a motor housing 13′, through which a motor shaft 4′ extends. The motor shaft 4′ is connected in a way that precludes rotation to a motor pinion 2′. On the end face, the sensor element 3′ adjoins the motor pinion 2′.

[0041] The sensor element 3′ has a hollow-cylindrical design and has two material segments 12′, which delimit two recesses 5′. The material segments 12′ have a uniform wall thickness. Preferably, the material segments 12′ have a uniform width so that the recesses 5′ also have a uniform width. The recesses 5′ are arranged radially opposite one another.

[0042] In contrast to the first exemplary embodiment, the second exemplary embodiment provides that the sensor element 3′ has only two recesses 5′. These recesses 5′ pass light beams from two rotary encoders 7′, which are arranged on a common sensor circuit board 6′. The common sensor circuit board 6′ is arranged axially spaced from the sensor element 3′.

[0043] The rotary encoders 7′ each have a light-barrier element which is arranged radially inside the sensor element 3′. Each of the rotary encoders 7′ also has a further light-emitting element which is arranged radially outside the sensor element 3′. The light beams 11 of the rotary encoders 7′ are aligned at an acute angle to one another.

[0044] FIG. 6 shows, by means of the second exemplary embodiment, an arrangement of the electric motor 1 within a syringe pump. Such an arrangement can also be implemented in all further exemplary embodiments and is not restricted to the second exemplary embodiment.

[0045] In general, the injection pump has a drive housing 16′, which accommodates the electric motor 1′, in particular the motor housing 13′. A spur gear 14′, which is coupled with the motor pinion 2′ of the electric motor 1′ via a spur gear 8′, is also mounted in the drive housing 16′. The spur gear 14′ acts on a threaded spindle 15′. The threaded spindle 15′ is connected to a syringe piston receptacle. Thus, a movement of the threaded spindle 15′ can be transmitted to a syringe plunger.

[0046] The syringe pump basically operates as follows. The motor shaft 4′ is rotated by the electric motor 1′. The motor shaft 4′ is connected in a way that precludes rotation to the motor pinion 2′. Thus the rotation of the motor shaft 4′ is transmitted directly to the motor pinion 2′, which consequently rotates at the same speed as the motor shaft 4′. The rotational speed and the direction of rotation are thereby determined by means of the rotary encoders 7′ of the encoder and, if necessary, adjusted by means of preset values.

[0047] The motor pinion 2′ meshes with the spur gear 8′, the rotational movement of which is transmitted to the spur gear transmission 14′. The spur gear 14′ transmits the rotary motion to the threaded spindle 15′, which converts the rotary movement into a linear movement. By means of the transmission ratio of the spur gear 14′, the thread spindle 15′ performs a longitudinal-axial movement with a constant, specifically very slow, speed. For example, medications from a syringe can be dispensed continuously with constant fluid flow.

[0048] FIG. 7 shows a third exemplary embodiment of the invention. In essence, an electric motor 1″ is shown including a motor shaft 4″. A motor pinion 2″ is connected in a way that precludes rotation to the motor shaft 4″. A sensor element 3″ protrudes beyond the motor shaft 4″, which is designed in one piece with the motor pinion 2″. The sensor element 3″ comprises multiple recesses 5″ which pass a light beam 11″ of a rotary encoder 7″. For this purpose, the rotary encoder 7″ comprises a light source 9″ and a light receiver 10″ which are arranged radially opposite one another in relation to the motor shaft 4″.

[0049] In the third exemplary embodiment according to FIG. 7, it is provided that the rotary encoder 7″ is arranged completely radially outside the sensor element 3″. In particular, the rotary encoder 7″ has two light-emitting elements, in particular the light source 9″ and the light receiver 10″, which are each positioned radially outside the sensor element 2″. The light beam 11″ thus completely passes through the sensor element 3″. For this purpose, it is provided that the sensor element 3″ has at least two recesses 5″ which are arranged radially opposite one another.

[0050] A fourth embodiment of the invention is shown in FIG. 8. An electric motor 1′″ is shown, which has a motor housing 13′″. A motor shaft 4″′ protrudes coaxially from the motor housing 13′″, which is connected in a way that precludes rotation to a motor pinion 2″. The motor pinion 2′″ interlocks with a spur gear 8′″.

[0051] A sensor element 3′″ adjoins the motor pinion 2′″ longitudinally and integrally. The sensor element 3′″ is essentially hollow-cylindrical in shape. In particular, the sensor element 3′″ has one or more material segments 12′″ which delimit at least one recess 5′″.

[0052] Arranged in the axial direction spaced from the motor housing 13′″ is an encoder with a sensor circuit board 6′″ and at least one rotary encoder 7′″ which is firmly connected to the sensor circuit board 6′″. The rotary encoder 7′″ includes a light source 9′″ and a light receiver 10′″. The light source 9′″ and the light receiver 10′″ are arranged radially opposite each other. A light beam 11′″ can be activated between the light source 9′″ and the light receiver 10′″.

[0053] As it can be clearly seen in FIG. 8, the sensor element 3′″ has a cross-sectional diameter that is markedly larger than the cross-sectional diameter of the motor pinion 2′″. Thus, even in the case of a small motor pinion 2′″, a rotary encoder 7′″ can be arranged in such a way that the light receiver 10′″ is located radially inside the sensor element 3′″, whereas the light source 9′″ is located radially outside the sensor element 3′″. In particular, more than one rotary encoder 7′″ may be provided in order to improve the accuracy of the measurement.

[0054] The above-described invention is generally suitable for particularly compact electric motors. Specifically, the invention is particularly suitable for electric motors with an outer diameter, specifically an outer diameter of the housing, of 8 mm.

[0055] It is to be understood that the present invention is not limited to the illustrated embodiments described herein. Various types and styles of user interfaces may be used in accordance with the present invention without limitation. Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.

LIST OF REFERENCE SYMBOLS

[0056] 1, 1′, 1″, 1′″ Electric motor

[0057] 2, 2′, 2″, 2′″ Motor pinion

[0058] 3, 3′, 3″, 3′″ Sensor element

[0059] 4, 4′, 4″, 4′″ Motor shaft

[0060] 5, 5′, 5″, 5′″ Recess

[0061] 6, 6′, 6″, 6′″ Sensor circuit board

[0062] 7, 7′, 7″, 7′″ Rotary encoder

[0063] 8, 8′, 8″, 8′″ Spur gear

[0064] 9″, 9′″ Light source

[0065] 10″, 10′″ Light receiver

[0066] 11″, 11′″ Light beam

[0067] 12, 12′, 12″, 12′″ Material segment

[0068] 13, 13′, 13″,13′″ Motor housing

[0069] 14′ Spur gear motor

[0070] 15′ Threaded spindle

[0071] 16′ Drive housing