DRIVE UNIT FOR AN ACTUATOR, AND ACTUATOR INCLUDING A DRIVE UNIT AND A TRANSMISSION UNIT

A drive unit is described for driving a transmission unit of an actuator, as well as an actuator that includes a drive unit and a transmission unit. The drive unit includes an alignment element, which is engageable with a mating element of the transmission unit to be driven. The mating element is part of a transmission pin of the transmission unit.

BACKGROUND INFORMATION

The unexamined patent application DE 102012222949 A1 describes a transmission device including a worm shaft, which may be set in rotation by an electric motor, as well as a first worm gear connected to a first pinion and a second worm gear connected to a second pinion, which contact the worm shaft in such a way that the first worm gear and the first pinion are rotatable about a shared first rotation axis and the second worm gear and the second pinion are rotatable about a shared second rotation axis. The transmission device also has an adjustable piston, which is adjustable along an adjustment axis with the aid of the first pinion rotated about the first rotation axis and with the aid of the second pinion rotated about the second rotation axis. The invention also relates to an electromotive brake booster.

SUMMARY

The drive unit according to the present invention for driving a transmission unit of an actuator includes an alignment element, which is engageable with a mating element of the transmission unit to be driven. The mating element is part of a transmission pin of the transmission unit. This has the advantage that a mechanical interaction exists between the transmission pin and the drive element, which is suitable for stabilizing the transmission pin.

If the transmission pin were mounted on both sides in a thin transmission housing, the bearing forces transferred to the transmission housing may be too great and may result in the transmission housing being elastically deformed under load. This could have the disadvantage that the transmission pin tilts under load. A tooth engagement of a gear wheel present in the transmission with a drive gear wheel may likewise deviate increasingly from the setpoint state. This may result in greater noise generation and in greater tooth stress.

The housing of the drive unit may be more stably designed than the housing of the transmission unit, as a result of which the housing of the drive unit is better suited for supporting the transmission pin.

The housing of the drive unit is able to withstand stronger forces. Thus, a tilting of the transmission pin may be effectively prevented, which improves the functionality of the transmission unit.

The drive unit in this case may be an electric motor, in particular, an electric motor with a control unit attached, for example, a so-called power pack. The transmission unit may be part of an actuator, which is a brake booster that is to be driven with the drive unit. Alignment element and mating element may be present as a plug/socket or socket/plug.

An embodiment of the drive unit includes a drive axle connected to a drive element. The alignment element as well as the drive axle are aligned in parallel in their respective longitudinal direction and offset relative to one another, the alignment in the longitudinal direction of the drive axle and of the alignment element corresponding, in particular, to an assembly direction of the drive unit with respect to the transmission unit. This has the advantage that during an assembly, the unit alignment element and mating element may be easily engaged. With the predefined offset of alignment element and drive axle, it is possible to also easily obtain a space to be obtained between the drive axle and the transmission pin during an assembly, which ensures a better functioning of the drive and the transmission.

In one embodiment of the drive unit, the alignment element is part of a housing of the drive unit. As a result, forces of the transmission pin may be readily withstood. A simple manufacture of the drive unit with the alignment element is equally possible, for example, in one piece as a pressed part or as a stamped part or as a casting.

In an embodiment of the drive unit, the alignment element is directly or indirectly attached to a housing of the drive unit. In contrast to an alignment element as part of the housing, the alignment element in this case is present as a separate component, which is directly or indirectly connected to the housing of the drive unit. Different techniques for connecting are possible, for example, directly adhered, screwed on, welded on or also indirectly connected via a support, in particular, a motor flange. This ensures a greater modularity when selecting or designing the alignment element if it is not directly part of the housing.

The actuator according to the present invention includes such a drive unit, as well as a transmission unit. The transmission unit includes the described mating element, which may be engaged with the alignment element of the drive unit. The drive unit is mechanically connected to the transmission unit in such a way that the mating element of the transmission unit is engaged with the alignment element of the drive unit. The mating element in this case is part of a transmission pin of the transmission unit. The actuator, i.e., for example, the brake booster including the drive unit thus installed, has the advantage that an optimal alignment of the transmission pin of the transmission unit is achieved by supporting the transmission pin on the drive unit. It is also advantageous that a degree of freedom is established for a correct alignment of the drive unit relative to the transmission unit by the engagement of the alignment element and the mating element. This allows for a simpler assembly.

In an embodiment of the actuator, the alignment element and the mating element are complementary to one another.

In another embodiment, it is provided that the alignment element and the mating element are complementary in such a way that the alignment element is plug-like and the mating element is socket-like. In this case, the alignment element is accommodated at least partly in the mating element. Alternatively, the alignment element may also be provided as socket-like and the mating element as plug-like, the mating element then being accommodated in the alignment element. The alternatives for providing complementary alignment and mating elements facilitate the engagement of the elements and the simple assembly of the drive unit with the transmission unit.

In an advantageous embodiment, a space is established by the parallel offset of the alignment element of the drive unit relative to the drive axle of the drive unit. As a result of the established space and as a result of the engagement of the alignment element with the mating element of the transmission pin, it is possible to establish a separation between a drive element and a transmission element. The transmission element in this case is situated on the transmission pin and is drivable with the aid of the drive element. The transmission element may be a transmission gear wheel; the drive element may be a motor pinion of the drive unit. As previously stated, a space established in such a way improves the functionality of the interaction between the drive and the transmission.

In an embodiment of the actuator, an area between the drive unit and the transmission unit, in which the mating element is engaged with the alignment element, is sealed off in a media-tight manner with the aid of a sealing element. This prevents water or dirt from being able to enter into the interior of the transmission.

It is further advantageous that the sealing element is situated around the mating element. This allows for a space-saving installation of a seal.

It may be further advantageous that the sealing element is also situated around the alignment element when the alignment element engages with the mating element. A surrounding seal capable of surrounding both parts may render another additional seal expendable.

In an embodiment, the sealing element may be situated between a housing wall of the drive unit and a housing wall of the transmission unit. This arrangement enables a simple fixing of the seal, since the drive unit and the transmission unit, during assembly, are fixed with respect to one another anyway.

In an embodiment of the present invention, the mating element, as well as the sealing element, is covered by a cap. It is therefore sufficient to provide one single seal and no additional separate seal. A covering of the mating element is accompanied by a corresponding covering of the corresponding alignment element. A covering may be present independently thereof, which element from the alignment element and mating element is provided as a pin and which element is provided as a cavity or hole. The cap is then to be adapted according to the alignment.

The cap advantageously has a step-like design and includes an annular surface and a circular surface. The circular surface covers the mating element and the annular surface covers at least partly the sealing element. Thus, the cap is optimally adapted to the existing geometry of the mating element and the alignment element, in order to ensure the seal with only one sealing element.

In another embodiment, the sealing element is situated between a housing wall of the drive unit or a motor flange of the drive unit on the one hand, as well as a housing wall of the transmission unit on the other hand. This allows for a sealing of the respectively present opposing components of the drive unit and the transmission unit.

DETAILED DESCRIPTION

FIG. 1shows a detail of an actuator, which includes at least one drive unit1as well as a transmission unit2. Such an actuator may, for example, be a brake booster, which generates hydraulic brake pressure in a hydraulic braking system by displacing motor-driven pressure pistons and, in the process, generating a braking action either automatically, i.e., driver-independent, or also in the form of a force assist of a driver during pressure build-up. A use in other actuators that are not brake boosters is also possible.

Drive unit1may be an electric motor1that includes a drive axle3. Drive axle3is rotatably mounted on a motor housing10and is mechanically connected to a motor pinion5. Motor pinion5is attached or is formed, in particular, formed in one piece, on one end of drive axle3.

Transmission unit2includes a transmission gear wheel6to be driven. Transmission gear wheel6is mounted on a transmission pin9. Transmission gear wheel6is mounted on transmission pin9in such a way that transmission gear wheel6is rotatable about transmission pin9. Transmission unit2is able to produce a movement in an actuator, for example, in a brake booster. A spindle drive of a brake booster may, for example, be driven as an actuator via transmission gear wheel6.

Transmission gear wheel6of transmission unit2is driven by drive unit1. For this purpose, the motor of drive unit1sets motor pinion5in rotation via drive axle3. Motor pinion5engages with transmission gear wheel6. Motor pinion5may be engaged with transmission gear wheel6via corresponding toothings of motor pinion5and transmission gear wheel6.

In order for motor pinion5to mechanically contact transmission gear wheel6, motor pinion5is introduced into an interior space11of transmission unit2. This may take place by inserting motor pinion5into interior space11through an opening of a housing part12of transmission unit2. Motor pinion5in this case may already be mounted on, formed on or connected to drive axle3.

Motor pinion5may be introduced into interior space11of the transmission unit by installing drive unit1together with transmission unit2. For this purpose, drive unit1, with motor pinion5, may be moved toward transmission unit2, for example, in assembly direction x. Transmission unit2may alternatively also be moved toward drive unit1.

When motor pinion5interacts with transmission gear wheel6, motor pinion5and transmission gear wheel6should be situated precisely relative to one another so that a sufficient mechanical engagement takes place between the driving component (motor pinion5) and the driven component (transmission gear wheel6). Forces are also transmitted during an interaction of motor pinion5and of the transmission gear wheel, which may result in a deviation from a previous exact arrangement of the components as a result of their load.

Drive unit1includes an alignment element7, which ensures the exact arrangement of motor pinion5relative to transmission gear wheel6. Transmission unit2also includes a mating element4, which also ensures the exact arrangement of the motor pinion relative to transmission gear wheel6.

An alignment element7may be a pin7or also a journal7. Such a pin7or journal7may be formed on housing10of drive unit1. Formed may be understood to mean, on the one hand, that alignment element7and housing10are one piece. Alternatively, alignment element7may be formed on housing10by being fastened thereto, for example, bonded, welded or screwed. Other fastening methods are also conceivable

It is equally possible for alignment element7to be formed as a recess7or as a cavity7or as a hole7in or on housing10of drive unit1. In this embodiment of alignment element7as well, alignment element7may be attached to the housing, or also formed in the housing. Fastening techniques also include known fastening methods, in particular, the fastening techniques cited as pin or journal in the embodiment.

Mating element4of transmission unit2is formed complementary to alignment unit7. Complementary is understood to mean that mating element4and alignment element7in their geometric dimensioning are provided in such a way that they are able to engage one another. In the case of a pin as alignment element7, corresponding mating element4, for example, is provided as a cavity or hole. The diameter and depth of cavity4or hole4are designed in such a way that pin7may be at least partly accommodated in cavity4. Furthermore, pin7may be force-fittingly accommodated in cavity4. Once introduced—if necessary using a press-in force, pin7may thus be retained in cavity4. A transfer of forces from one component to another is also possible as a result of a force-fit.

For the alternative case of one specific embodiment, in which an alignment element7is provided as a cavity on drive unit1, complementary mating element4is provided as pin4.

As previously described, transmission unit2includes a transmission pin9, which is mounted on housing12of transmission unit2. One end of transmission pin9in this case protrudes through an opening in transmission housing12in the direction of drive unit1. Mating element4is formed at the end of transmission pin9, which protrudes through the opening of transmission housing12.

Mating element4of transmission unit2is formed on transmission unit2at a point opposite alignment element7when transmission unit2and drive unit1are assembled. In other words, the positionings of alignment element7on drive unit1and of mating element4on transmission unit2match one another in such a way that mating element4and alignment element7are able to engage during a correspondingly oriented assembly.

As described above, motor pinion5extends into interior space11of transmission unit2through an opening in transmission housing2. As a result of the opening in transmission housing2for motor pinion5and as a result of the respective positioning of alignment element7on drive unit1and of mating element4on transmission unit2, an alignment is defined, in which drive unit1is to be assembled with transmission unit2. Only in such a corresponding alignment of transmission unit2relative to drive unit1is a precisely fitting assembly of the parts able to take place.

A motor flange13may also be provided between drive unit1and transmission unit2, which facilitates an attachment and/or a connection of the two units. Mentioned alignment element7may also be fastened to or also be formed in one piece with motor flange13. It is equally possible for alignment element7to be indirectly formed on drive unit1in the shape of a recess or cavity, for example, via motor flange13. An indirect formation on drive unit1via motor flange13may be present in the form of a bore/of a hole in motor flange13, motor flange13being fastened to drive unit1.

FIG. 2shows drive unit1in the uninstalled state, i.e., separate from transmission unit2. Highlighted once again inFIG. 2are drive axle3, motor pinion5, space d between pin7and drive axle3. This space d also defines the parallel offset at which pin7is situated relative to drive axle3. In the assembled state of drive unit1on transmission unit2, this space also corresponds to the relative parallel offset of drive axle3relative to transmission pin9. The specific embodiment shown inFIG. 2includes alignment element7as a pin. The associated transmission unit (not shown) must then include a cavity4as mating element4in transmission pin9.

In the example of a drive unit1shown here, alignment element7is not formed on, but is indirectly fastened to, housing10of the drive unit. Pin7is fastened via motor flange13, which is attached to housing10of the drive unit. Thus, pin7is formed on drive unit1by being indirectly fastened thereto. Pin7may be pressed into motor flange13. Pin7may also be pressed in and crimped. The connection between pin7and motor flange13is a rigid connection. The connection between pin7and motor flange13is media-tight, i.e., formed tight relative to air and/or water.

FIG. 3shows the engagement between an alignment element7in the form of a pin7with a mating element4in the form of a cavity4. Pin7in this embodiment is fastened, in particular, pressed and crimped in motor flange13.

It may be necessary to prevent water from entering into the actuator. It is apparent inFIG. 3that water could enter between drive unit1and transmission unit2at point15. Water penetrating there may enter into transmission unit2, in particular, in the area of the opening in housing wall12of transmission unit2, which accommodates transmission pin9. A seal14is attached in the area of the opening of transmission wall12for the purpose of sealing. In the exemplary embodiment depicted inFIG. 3, seal14is attached around one end of transmission pin9, which also includes mating element4. Seal14may be a sealing ring, for example. Sealing ring14is situated around transmission pin9and also includes in this case in the installed state of drive unit1with transmission unit2alignment element7, i.e., the pin in this case. Sealing ring14is situated in assembly direction x (seeFIG. 1) between housing wall10of drive unit1as well as housing wall12of transmission unit2. If, as shown in this example, pin7and housing10of the drive unit are not one piece, but the pin is fastened to drive unit1with the aid of a motor flange13, then sealing ring14is situated between drive unit1and transmission unit2, but is at least partly in contact with motor flange13and housing12of transmission unit2. A direct contact to housing10of drive unit1is not present in this specific embodiment.

FIG. 4shows an alternative embodiment of a seal between drive unit1and transmission unit2. In this embodiment, alignment element7is a cavity or recess7, in which transmission pin9with a tapered section4is supported at its end. In this embodiment, seal14is also situated around transmission pin9. Seal14includes a part of tapered section4of the transmission pin. Tapered section4of transmission pin9protrudes through the opening of housing wall12of transmission unit2. The axial sealing ring is situated directly, in particular, compressed in the assembled state, between housing wall10of drive unit1and housing wall12of transmission unit2. Axial sealing ring14in this specific embodiment is encompassed along its circumference at least partly by motor flange13.

FIG. 5shows an embodiment ofFIG. 4, in which mating element4of transmission pin9corresponds to the end of transmission pin9that protrudes through wall12of the housing of transmission unit2. Alignment element7in this case is a recess/cavity7, which is formed on drive unit1. The cavity in this case is formed in such a way that the cavity is a recess in motor flange13, which is permanently connected to drive unit1. The transmission pin then engages with motor flange13of drive unit1and is supported there.

The specific embodiment ofFIG. 6is based on the same principle, here however, a tapered part of transmission pin9engages with a corresponding cavity7in motor flange13through the opening of housing wall12of transmission unit2. The design of the opening of transmission housing12and of cavity7in this case is to be adapted to tapered section4of transmission pin9, in particular, to the length and to the diameter of tapered section4.

Common to both specific embodiments ofFIGS. 5 and 6is that when supporting end section4(or tapered section4inFIG. 6) of transmission pin9, a cap, which covers end section4, is used as mating element4in motor flange13, which is attached to drive unit1. End section4(or tapered section4inFIG. 6) covered by cap16engages with cavity7of the motor flange and is supported there. The cap in this case is shaped like a hat with a step. An annular surface16acovers sealing ring14. A circular surface16bof cap16covers transmission pin9. The cap may be made from sheet metal, other materials also being conceivable.

Sealing ring14in both specific embodiments ofFIGS. 5 and 6is pressed in only between lateral extensions16aof cap16and of housing wall12of transmission unit2. In this case, a stacking in the installed state of motor housing10, motor flange13, lateral extensions16aof cap16, seal14as well as transmission housing wall12takes place, if a cut is made in assembly direction x, which also corresponds to the longitudinal direction of transmission pin9, but somewhat beyond the center of transmission pin9. This is clearly apparent inFIGS. 5 and 6and is plotted as section line s.

With regard to cap16, it may be said that in the case of the embodiment of mating element4as a cavity, socket or hole4and of an embodiment of alignment element7as pin7or plug7, a covering may also be achieved with the aid of a cap16. In this case the bulge of the cap would be provided inversely and would protrude into mating element4. The diameters of the components involved would have to be adapted accordingly, since mating element4would then have to also accommodate the cap.

FIG. 7shows another embodiment of a seal, here pin7, which engages with mating element4, being formed directly on motor flange13.

Pin7in this case is in one piece with, for example, formed on motor flange13. Motor flange13, in turn, is permanently connected to housing10of drive unit1, so that pin7is formed on drive unit1via motor flange13. The formation in this case is not direct, but indirect via motor flange13.

Seal14, in turn, is an axial seal, which surrounds end section4of transmission pin9, i.e. mating element4along the circumference thereof and is installed, in particular, compressed between drive unit1and transmission unit2. Because mating element4and pin7are in engagement, the sealing ring also partly encompasses pin7, which is situated inside mating element4. More precisely, sealing ring14in this case is in direct contact with motor flange13and housing12of transmission unit2.

A sequence results radially from the outside inwardly to the center of the axle, beginning with sealing ring14, followed by an outer wall of mating element4of transmission pin9and by pin7.

A sequence housing wall12of transmission unit2, sealing ring14, motor flange13and housing10of drive unit1results along transmission pin9away from the axle center, in an analogous section s as inFIGS. 5 and 6.

A method for manufacturing an actuator is schematically shown inFIG. 8.

In a first step81, drive unit1and the transmission unit are aligned relative to one another. In the process, the alignment takes place in such a way that when joining the two units, drive axle3with motor pinion5may be guided through the opening in housing wall12of transmission unit2. The alignment also takes place under the condition that alignment element7and mating element4are positioned opposite one another and may be brought into engagement with one another when joining drive unit1and transmission unit2.

In a subsequent step82, drive unit1and the transmission unit are guided toward one another, so that motor pinion5is introduced into interior space11of transmission unit2, and alignment element7is also brought into engagement with mating element4. In this step of guiding drive unit and transmission unit1,2toward one another, motor pinion5is positioned in interior space11of transmission unit2exactly in relation to transmission gear wheel6. The positioning takes place in such a way that a force transfer may be achieved in a known manner when motor pinion5rotates. The guiding toward one another takes place in assembly direction x shown inFIG. 1.

In a step83, drive unit1and transmission unit2are then fixed to one another. A fixing may take place, for example, by screwing those two units together. Additional connection techniques are possible.

Sealing ring14is situated at an appropriate point prior to the guiding toward one another depending on the specific embodiment of mating element4and alignment element7. Cap16—if present in the specific embodiment—is positioned accordingly before drive unit1and transmission unit2are guided toward one another.