Patent Application
20080309179
This application is the US National Stage of International Application No. PCT/EP2005/054602, filed Sep. 16, 2005 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2004 045 493.0 DE filed Sep. 20, 2004, both of the applications are incorporated by reference herein in their entirety.
The invention relates to an electric machine, which is provided in particular as a drive for an injection molding machine. The electric machine is designed such that it is capable of implementing both an excursion movement and a rotary movement. For this purpose, the electric machine has at least two electric motors. The electric motors are arranged coaxially with respect to one another.
Such an electric machine is known, for example, from DE 43 44 335 A1. It is used, for example, in an injection molding machine, such an injection molding machine being known, for example, from EP 0 204 002 B1.
Various demands can be placed on an electric machine. One demand is, for example, a compact design, which is also of particular significance in the case of injection molding machines, since these also always have a compact design. Another demand placed on electric machines is, for example, a simple design. This makes it possible to reduce manufacturing costs, for example.
An object of the invention is to develop an electric machine such that a compact and/or simple design of this electric machine is possible.
In accordance with the invention, this object is achieved by an apparatus as claimed in the independent claims. Dependent claims show further configurations of the the invention.
The electric machine according to the invention, which is provided in particular as a drive for an injection molding machine (for example for plastic), is designed to implement a rotary movement and to implement a linear movement. A first electric motor is provided for implementing the linear movement, and a second electric motor is provided for implementing the rotary movement. By means of the two electric motors, a moveable means can be moved both in rotary and linear fashion. The moveable means is, for example, a shaft. The electric motors have axes. The first electric motor has a first axis, and the second electric motor has a second axis. The first and the second axes essentially correspond to one another. This means that the electric motors are arranged coaxially. The linear movement can be carried out by means of a threaded mechanism. The threaded mechanism is, for example, a threaded spindle on which a threaded nut is arranged. The threaded nut is capable of moving linearly by means of a rotation of the threaded spindle. The electric machine according to the invention is characterized by the fact that a first rotor of the first electric motor is connected directly to the threaded mechanism, and a second rotor of the second electric motor is connected to a threaded mechanism means of the threaded mechanism. The threaded mechanism means is, for example when using a threaded spindle, a threaded nut.
In addition to a first rotor, the first electric motor also has a first stator. In addition to a second rotor, the second electric motor also has a second stator. The designation of first and second stator or first and second rotor is intended in this context to serve the purpose of differentiating between the rotor or the stator of the first and the second motor. The difference between a first rotor and a second rotor is therefore used for the assignment of the rotor either to the first electric motor or to the second electric motor. The same applies to the stator.
By means of the direct connection between the first rotor and the threaded mechanism, it is possible to realize a simple design of the electric machine. For example, it is not necessary to design the threaded mechanism with a drilled hole for the purpose of inserting a shaft for rotary movements.
In one advantageous configuration, at least one of the electric motors is a hollow shaft electric motor. The use of a hollow shaft electric motor makes it possible to achieve a more compact design of the electric machine. The two motors can therefore be interconnected.
In a further advantageous configuration, the first electric motor and the second electric motor have a region having the same axial position. The first electric motor and the second electric motor are therefore arranged such that they overlap one another entirely or at least partially. However, an onion like positioning of the electric motors in relation to one another results. This has the advantage that, as a result, a particularly compact design can be achieved. In particular, the axial length of the electric machine can be substantially shortened thereby.
The abovementioned object is further achieved by means of an electric machine, which is provided in particular as a drive for an injection molding machine, the electric machine having a first electric motor for the purpose of implementing a linear movement and a second electric motor for the purpose of implementing a rotary movement, a moveable means being capable of moving in rotary and linear fashion by means of the rotary movement and the linear movement, a first axis of the first electric motor essentially corresponding to a second axis of the second electric motor, and it being possible for the linear movement to be carried out by means of a threaded mechanism. It is characteristic of such an electric machine that the first electric motor and the second electric motor have a region having the same axial position. This means that the first electric motor has, entirely or at least partially, the same axial position as the second electric motor.
In a further advantageous configuration of the electric machines according to the invention, the stator of the first electric motor, which is also referred to as the first stator, can be cooled by means of a cooling device. The second stator of the second electric motor can also be cooled by means of a cooling device. Advantageously, the first stator and the second stator have a common cooling device, the common cooling device being arranged in particular between the first stator and the second stator. The common cooling device is, for example, helical, for example cooling coils, which can have cooling air or a cooling liquid applied to them, extending on a cylindrical outer side of the first stator and at the same time extending on an inner cylindrical side of the second stator, the second electric stator being, for example, the stator of an external rotor motor. The use of a cooling device for cooling two electric motors makes it possible to achieve improved compactness of the electric machine.
In a further advantageous configuration, the second electric motor is connected to the threaded mechanism means by means of a linear bearing. In this way, the threaded mechanism means is capable of moving both in linear and rotary fashion.
It is furthermore advantageous if the linear bearing has at least three linear guides, which are arranged in angle symmetrical fashion. Each of the linear guides has, for example, a rail and a carriage, the carriage having a ball chain (or a circulating ball chain). Linear bearings can also be designed such that they have a sliding bearing, a rolling bearing or else a ball bearing.
Advantageously, the first rotor is mounted by means of an axial bearing and by means of a radial bearing. In one further configuration, both bearings can also be replaced by a single bearing, this bearing having to absorb both radial forces and axial forces. A bearing is referred to as an axial bearing and/or a radial bearing depending on the loading direction envisaged for this bearing.
The electric machine can furthermore be designed such that the second rotor is mounted by means of a radial bearing.
The bearing of the first rotor and the bearing of the second rotor advantageously have a fixed connection to a common element. The common element is, for example, a housing part of the electric machine.
In a further configuration of the invention, the threaded mechanism is a threaded spindle, the threaded mechanism means being a threaded nut, the threaded spindle in particular being in the form of a ball-screw spindle.
In order to be able to regulate the electric machine, both the first electric motor and the second electric motor have at least one position sensor. The position sensors are used for regulating the position of the two electric motors, the position sensors in particular being positioned between the stator and the rotor.
In order to regulate the electric machine, a regulating system is provided. The regulating system is designed such that the first electric motor is regulated in terms of an angular difference between a required rotary angle of a drive shaft and/or in terms of an excursion, it being possible for the excursion to be calculated by means of the spindle gradient and the rotary angle. The second electric motor can be regulated by means of the regulating system, for example in terms of the rotary angle of the drive shaft.
The regulation of the rotary angle is to be understood, for example, as meaning a speed regulation and/or a position regulation of a rotary movement.
The invention further relates to an injection device for an injection molding machine, which has an advancing screw and the electric machine, in one of the above-described configurations, is provided for driving the advancing screw.
An exemplary embodiment of the invention is illustrated in the drawing and will be explained in more detail below. In the drawing:
The illustration in
By means of the electric machine 1, rotary and also linear movements can be carried out. In order to carry out linear movements, a threaded spindle 17 is provided. A threaded nut 19 rests on the threaded spindle 17. Mounting takes place, for example, via balls such that a threaded roller spindle is provided. The balls are not illustrated in
In order to realize a compact design of the electric machine 1, the electric motors 3, 9 are arranged such that they are interconnected. The stator 5 of the first electric motor 3 and the stator 11 of the second electric motor 9 are fixed to a machine housing 15. The rotor 7 of the first electric motor 3 and the rotor 13 of the second electric motor 9 are mounted on the machine housing 15, the mounting also taking place, for example, by means of an element fitted to the machine housing 15, such as a stator 5, 11, for example. The rotor 7 of the first electric motor and the rotor 13 of the second electric motor 9 are connected to a ball-screw mechanism. The ball-screw mechanism has at least the threaded spindle 17 and the threaded nut 19. The rotor 7 of the first electric motor 3 is fixedly connected to the threaded spindle 17. The rotor 13 of the second electric motor 9 is connected to the threaded nut 19 of the ball-screw mechanism via a linear bearing 21. The linear bearing 21 has, for example, linear guides having a ball chain. The threaded nut 19 is fixedly connected to the drive shaft 23.
The illustration in
The rotor 7 of the first electric motor 3 is mounted on the machine housing 15 by means of an axial bearing 31 and a radial bearing 33. The rotor 13 of the second electric motor 9 is mounted on the machine housing 15 by means of a radial bearing 35.
As shown in
A cooling device 25 is positioned between the stator 5 and the stator 11. The cooling device 25 has a shaped part 24 and a shaped part 28, the cooling channels 26 being formed by means of the shaped parts. The cooling channels 26 are provided, for example, for guiding a cooling air flow or a cooling liquid.
Both the first electric motor 3 and the second electric motor 9 can be implemented, for example, as permanently excited three phase synchronous motors with windings in the stators 5 and 11. The rotors 7 and 13 have permanent magnets 8. The three phase synchronous motors 3, 9 are characterized by a high torque density. Owing to the use of a hollow shaft, a compact design of the electric machine can be ensured.
In order to regulate the electric machine 1, position sensors are provided for the electric motors 3, 5. A position sensor 37 is provided for determining the position of the first electric motor 3, and a position sensor 39 is provided for determining the position of the second electric motor 9. The electric motors 3, 9 can be regulated in terms of their position and speed by means of the position sensors. The first electric motor 3 is regulated, for example, in terms of an angular difference φ1 between the required rotary angle φ of the drive shaft 11 and the required excursion X converted from the spindle gradient h in relation to the rotary angle.
The second motor 2 is regulated in terms of the required rotary angle φ of the drive shaft 11.
The desired angle values φ1 for the first motor 1 and φ2 for the second motor 2 are calculated as follows:
φ1=φ360*Xh
φ2=φ
The torques M1 for the first motor 1 and M2 for the second motor 2 are calculated as follows:
M1=F*h/(2π)
M2=M M1
As a result of the fixed connection between the drive shaft and the threaded nut, and not the threaded spindle, as is the case in the known solution, the threaded spindle is simplified since it no longer requires any internal linear bearing and can be designed with a standard spindle. As a result of the two motors being installed inside one another, and not next to one another, a very compact design is achieved, it thus being possible to reduce the total length of the drive. Thanks to the embodiment of the first motor 3 as an internal rotor motor and of the second motor 9 as an external rotor motor and thanks to the installation of a water cooler 25 between the stators 5, 11 of the two motors, installation space for water coolers 25 is also saved, since one cooler cools both motors 3, 9.
The illustration in
The illustration in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 045 493.0 | Sep 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/54602 | 9/16/2005 | WO | 00 | 8/5/2008 |
