EP4314597A1

EP4314597A1 - Electric parking brake and method for production thereof

Info

Publication number: EP4314597A1
Application number: EP22709236.8A
Authority: EP
Inventors: Michael Schaefer; Michael WEINS
Original assignee: ZF Active Safety GmbH
Current assignee: ZF Active Safety GmbH
Priority date: 2021-03-30
Filing date: 2022-02-10
Publication date: 2024-02-07
Also published as: CN117098934A; WO2022207171A1; DE102021108111A1; US20240183411A1

Abstract

An electric parking brake (100) has a spindle drive (28) which can be actuated electrically and is self-locking. The spindle drive (28) comprises a spindle (34) having an external thread and a spindle nut (30) having an internal thread which engages with the external thread. The external thread and the internal thread have a symmetrical thread profile. Furthermore, the profile flanks of adjacent profile peaks of the external thread transition directly into one another via a rounding in the profile valley lying between them. The invention further relates to a method for producing a parking brake (100) of this type.

Description

Electric parking brake and manufacturing method

The invention relates to an electric parking brake with a spindle drive that can be actuated electrically and is self-locking. The invention also relates to a method for producing such a parking brake.

Electric parking brakes in general and with a spindle drive in particular are known from the prior art. These parking brakes are used in motor vehicles and are intended to prevent the motor vehicle from rolling when the parking brake is engaged. The electric parking brake is adjusted and preloaded into an engaged position via an electric motor using the spindle drive.

In the prior art, spindle drives with a sawtooth-shaped thread are usually used for electric parking brakes. Sawtooth profiles are very well suited as a spindle drive in an electric parking brake, as they absorb the loads acting on one side very well and have a high degree of efficiency due to the steep load-bearing thread flanks.

In cost-driven mass production, the sawtooth profiles of spindles and spindle nuts are primarily produced using forming processes. A sawtooth profile is unfavorable here, since the asymmetrical design of the thread profile, i. H. the combination of steep and flat thread flanks, is very difficult to produce using forming processes. The material rises only reluctantly in the steep thread flanks. This results in large closed creases and low degrees of closure of the thread profiles, which leads to insufficient overlap. Ensuring the required degrees of closure leads to low tool life and long cycle times, which has a negative impact on production costs.

Against this background, the object of the invention is to provide an improved electric parking brake and an improved method for producing it. To solve the problem, an electric parking brake is provided with a spindle drive that can be actuated electrically and is self-locking. The spindle drive comprises a spindle with an external thread or bolt thread and a spindle nut with an internal thread or nut thread which engages with the external thread. The external thread and the internal thread have a symmetrical thread profile. Furthermore, the profile flanks of adjacent profile peaks of the external thread merge directly into one another via a rounding in the intermediate profile valley.

For the purposes of the invention, a symmetrical thread profile is understood to mean, in particular, a thread profile whose profile halves are mirror-symmetrical with respect to a central axis that extends radially through the profile tip in cross section.

According to the invention, it was recognized that a spindle drive with a symmetrical thread profile instead of an asymmetrical thread profile has properties that meet the high demands placed on the spindle drive or the parking brake. The decisive factor here is that the profile valleys are rounded in order to be able to absorb the stresses introduced into the thread under load and thus to avoid thread breakage.

The symmetrical thread profile with a completely rounded profile valley also has the advantage that, compared to an asymmetrical thread profile, it can be produced with little effort and more reliably with high quality by forming, in particular by rolling.

Here, the rounding of the profile valleys of the external thread can have a radius of between 0.18 mm and 0.22 mm, in particular 0.2 mm.

Additionally or alternatively, the profile flanks of adjacent profile peaks of the internal thread can merge directly into one another via a rounding in the intervening Profi Ital. The rounding of the profile valleys of the internal thread has a radius of between 0.23 mm and 0.27 mm, in particular 0.25 mm.

These radii of the rounding of the profile valleys of the external thread and the internal thread ensure a particularly high strength of the corresponding thread. The values mentioned above and below are values that are far removed from the geometries of spindles according to DIN standards. However, the significantly cheaper spindles according to DIN standards do not come close to providing the required properties for spindle drives of parking brakes, which sometimes contradict each other (e.g. high clamping force, easy to manufacture and quick adjustability, ie quick stroke).

In one embodiment, the external thread and the internal thread have a flank angle of between 26.5° and 29.5°, preferably between 27° and 29°, in particular 28°. This comparatively small flank angle ensures that the spindle drive can provide a high preload force. Furthermore, the thread with such a flank angle can be produced efficiently by means of forming processes.

In a further embodiment, the external thread and the internal thread have a pitch of between 1.2 mm and 1.3 mm, in particular 1.25 mm. As a result of this comparatively small gradient, a higher clamping force can be achieved in comparison to the prior art with the same input torque by appropriate dimensioning of the thread while meeting the strength requirements. Furthermore, this slope offers a good compromise between a flat slope, which favors the self-locking of the spindle drive, and a steep slope, which increases the speed at which the spindle drive can be adjusted.

Provision can be made for the external thread to have a nominal diameter of between 8.3 mm and 8.4 mm, in particular 8.35 mm, as a result of which the spindle has a low mass with sufficiently high strength.

According to one embodiment, the external thread has a

Core diameter between 6.35 mm and 6.55 mm, preferably between 6.4 mm and 6.5 mm, in particular 6.45 mm. Additionally or alternatively, the internal thread has a core diameter of between 6.75 mm and 6.95 mm, in particular 6.85 mm. As a result, the spindle is particularly compact and can be manufactured in a material-efficient manner.

According to one embodiment, the external thread has a

Flank diameter between 7.5 mm and 7.7 mm, preferably between 7.55 mm and 7.65 mm, particularly 7.6 mm. Additionally or alternatively, the internal thread has a flank diameter of between 7.7 mm and 7.9 mm, preferably between 7.75 mm and 7.85 mm, in particular 7.8 mm. A particularly high overlap can be ensured in this way.

Furthermore, the profile valleys and profile peaks of the external thread and/or the internal thread can each have a width of between 0.62 mm and 0.63 mm, in particular 0.625 mm, at the level of the flank diameter. Such a width ensures high strength and thus reduces the risk of thread breakage under load.

Additionally or alternatively, the external thread and/or the internal thread can have rounded profile tips. In this way, the threads can be produced cost-effectively, since rounded profile tips can be formed more easily during forming, in particular during rolling, and post-processing of the profile tips can therefore be dispensed with.

According to the invention, a method for producing a parking brake according to the invention with the following step is also provided to solve the above-mentioned object:

rolling the spindle after a final heat treatment of the spindle and/or heat treating the spindle nut after a final rolling of the spindle nut.

This process has the advantage that the thread diameter can be reduced by the end-rolled spindle and the high-strength spindle nut.

Surprisingly, spindle drives with differently manufactured spindles and spindle nuts showed particularly good functional properties. H. the spindle was rolled after a final heat treatment, the nut was heat treated after a final rolling.

Further advantages and features emerge from the following description and from the accompanying drawings. In these show:

- Figure 1 in a partially sectioned representation of a caliper with a brake piston and an electric parking brake according to the invention, the has a spindle drive with a spindle and a spindle nut, with a section of a brake disc also being shown,

- Figure 2 in a sectional view of the spindle and the spindle nut of the spindle drive from Figure 1 together with components of the brake piston,

- Figure 3 in a detailed view of the external thread of the spindle of Figure 2, and

- Figure 4 in a detailed view of the internal thread of the spindle nut from Figure 2.

FIG. 1 shows a brake caliper 10 of a disc brake of a vehicle, which interacts with a brake disc 12 .

The caliper 10 includes a caliper body 14 to which a first brake pad 16 is attached. The first brake pad 16 is thus held immovably on the brake caliper body 14 .

In addition, a second brake pad 18 is provided, which is slidably mounted on the brake caliper body 14 so that it can be selectively pressed against the brake disc 12 by means of a brake piston 20 in order to achieve a braking effect.

For this purpose, the brake piston 20 is displaceable in a cylindrical opening, here z. B. a fluid cylinder 22 which is formed on the caliper body 14 is mounted.

In this case, a pressure chamber 24 that can be acted upon by pressure fluid is delimited by an end of the fluid cylinder 22 that faces away from the brake disk 12 and by the brake piston 20 .

The pressure chamber 24 is fluidically connected to a pressure fluid connection 26 via which a pressure fluid can be optionally introduced into the pressure chamber 24 and discharged from it.

For example, the pressure fluid is a hydraulic fluid. Thus, the fluid cylinder 22 is a hydraulic cylinder. The brake piston 20 can be moved hydraulically towards the brake pad 18 and the brake disc 12 so that the brake pad 18 is applied to the brake disc 12 and brakes it. Since the brake caliper 10 can be displaced in the direction of the longitudinal axis 32 of the piston according to the “floating caliper” principle, the brake lining 16 is also applied to the brake disc 12 in parallel.

In addition, the brake piston 20 is coupled to an electric parking brake 100 which has a spindle drive 28 .

However, it should be emphasized that the brake piston 20 with the functions described above and below can also be used in a purely electromechanical brake and is accommodated here in a cylindrical opening which can be designed as a bore or as the opening of a tubular cylinder.

In this context, a spindle nut 30 of the spindle drive 28 is non-rotatably due to its non-circular outer contour, but is mounted on the brake piston 20 in an axially displaceable manner along a piston longitudinal axis 32 . The spindle nut 30 interacts with a spindle 34 of the spindle drive 28 , which is rotatable about the piston longitudinal axis 32 but is otherwise stationary on the brake caliper body 14 . The spindle 34 can be selectively set in rotation by means of an electric drive motor 36 .

Thus, the brake piston 20 can also be moved towards the brake pad 18 and the brake disc 12 by means of the spindle drive 28, so that the brake pads 16 and 18 are pressed against the brake disc 12 and brake it.

The brake piston 20 is shown in detail in FIG. 2 together with the spindle nut 30 and the spindle 34 .

In this context, the brake piston 20 is essentially composed of a first tubular piston body section 38 and a second tubular piston body section 40 .

Both piston body sections 38, 40 extend along the

Longitudinal axis of the piston 32.

The second piston body section 40 is slightly conical with respect to the longitudinal axis 32 of the piston. Its cross-section decreases starting from from that end which is arranged adjacent to the spindle drive 28 in the direction of the end on the brake pad side.

Furthermore, the second piston body section 40 is arranged radially completely inside the first piston body section 38 to form an annular cavity 42 in an axial view. In other words, the second piston body section 40 lies completely within the first piston body section 38 when the brake piston 20 is viewed along the longitudinal axis 32 of the piston. However, this embodiment is not to be understood as limiting.

In the illustrated embodiment, the second piston body section 40 optionally also lies axially completely within the first piston body section 38 . This means that the second piston body section 40 does not protrude axially beyond the first piston body section 38 . This applies to both axial ends of the second piston body section 40.

The first piston body section 38 and the second piston body section 40 are connected to one another via an annular end wall section 44 . The annular end wall section 44 thus also delimits the cavity 42 in the axial direction.

In addition, the second piston body section 40 is axially closed by a base section 46 at its end opposite the end wall section 44 along the piston longitudinal axis 32 .

In the illustrated embodiment, the bottom portion 46 is frusto-conical. However, it goes without saying that this can also be shaped differently, e.g. B. flat or conical.

The second piston body section 40 and the bottom section 46 together form a cavity in which the spindle nut 30 is accommodated.

An inner peripheral surface 48 of the second piston body section 40 has an anti-twist contour 50 .

For example, the anti-twist contour 50 is formed in that the second piston body section has an octagonal cross section. The spindle nut 30, which represents a region of the spindle drive 28 that protrudes into the anti-twist contour 50, has a complementary cross-sectional geometry, ie it is also octagonal, for example. This means that the spindle nut 30 cannot be twisted relative to the brake piston 20 .

However, the spindle nut 30 can be displaced along the piston longitudinal axis 32 within the second piston body section 40 .

The inner peripheral surface 48 thus also forms an axial guide contour 52 for the spindle drive 28, more precisely for the spindle nut 30.

The already mentioned taper of the second piston body section 40 is so small that the spindle nut 30 can be guided over the entire axial length by means of the guide contour 52 .

In addition, a pressure surface 54 is positioned on an axial end of the first piston body section 38, which serves to be applied to the brake lining 18, ie to apply a force to it.

The pressure surface 54 extends over the axial end face of the first piston body section 38 on the one hand and over an annular pressure surface extension 56 extending radially inwards from the end face.

In order to prevent twisting of the brake piston 20 relative to the caliper body 14, this is non-rotatably mechanical coupling means z. B. with the brake pad 18, usually with the so-called back plate of the brake pad 18 connected. For example, a projection is provided on the brake piston 20 or on the back plate, which engages in a component made up of the brake piston 20 and the back plate on the other in order to effect a non-rotatable coupling.

The brake piston 20 is also designed in such a way that the pressure surface 54 and an axially outer end surface 60 of the base section 46 lie essentially in a plane E (see FIG. 2).

When the brake piston 20 is in operation, not only the pressure surface 54 but also the end surface 60 is in contact with the brake pad 18 . Furthermore, the brake piston 20 is frictionally connected to the brake caliper body 14 via a seal 62 .

The spindle nut 30 has an internal thread 70 and the spindle 34 has an external thread 72 which engages with the internal thread 70 .

The internal thread 70 and the external thread 72 are self-locking threads and each have a symmetrical thread profile 74, 76 (see FIGS. 3 and 4), the geometry of which is explained below with reference to FIGS.

Here, the internal thread 70 and the external thread 72 have a pitch of 1.25 mm.

In an alternative embodiment, the pitch of the internal thread 70 and the external thread 72 is between 1.2 mm and 1.3 mm.

FIG. 3 shows the external thread 72 of the spindle 34 with a nominal diameter DNA, a core diameter DKA, a flank diameter DFA and a diameter DA, from which the rounding of the thread crest begins.

The nominal diameter DNA of the external thread 72 is 8.35 mm.

In an alternative embodiment, the nominal diameter D _N A of the external thread 72 is between 8.3 mm and 8.4 mm.

The core diameter DKA of the external thread 72 is 6.45 mm.

In an alternative embodiment, the core diameter D _KA of the external thread 72 is between 6.35 mm and 6.55 mm, preferably between 6.4 mm and 6.5 mm.

The flank diameter DFA of the external thread 72 is 7.6 mm.

In an alternative embodiment, the flank diameter DFA of the external thread 72 is between 7.5 mm and 7.7 mm, preferably between 7.55 mm and 7.65 mm.

The diameter D _A of the external thread 72 is at least 8 mm. The external thread 72 has a flank angle W _A which is made up of the two partial angles W _A and W _2A .

In the illustrated embodiment, the two partial angles Wi _A and W _2A are equal, ie each of the partial angles Wi _A and W _2A is half as large as the flank angle W _A .

The flank angle W _A of the external thread 72 is 28°.

In an alternative embodiment, the flank angle W _A of the external thread 72 is between 26.5° and 29.5°, preferably between 21 and 29°.

The profile valleys 78 and profile peaks 80 of the external thread 72 each have a width B _A of 0.625 mm at the level of the flank diameter D _FA .

In an alternative embodiment, the width B _A is between 0.62 mm and 0.63 mm.

The profile valleys 78 of the external thread 72 each have a rounding 82 which connects the profile flanks 84 of the profile peaks 80 adjacent to the profile italic 78 directly to one another. In other words, the profile valleys 78 are formed without straight profile sections.

Furthermore, the profile valleys 78 are designed without corners.

The roundings 82 of the profile valleys 78 of the external thread 72 have a first radius R _IA at the transition to one profile flank 84 and a second radius R _2A at the transition to the opposite profile flank 84.

In the present exemplary embodiment, the radius R is _IA and the radius is

R _2A each 0.2mm.

The profile italic 78 is preferably only formed by a radius, ie the opposite flanks transition into a valley which is formed exclusively by a radius, with which the radii R _1A and R _2A coincide.

In an alternative embodiment, the radius R _IA and/or the radius R _2A is between 0.18 mm and 0.22 mm, both radii being the same and can coincide as explained above. The crest of the thread 80 is rounded complementarily to the valley of the thread 78, ie the rounding has the same radius as the valley of the thread 78, although only one radius can be provided here, which merges directly into the flanks.

FIG. 4 shows the internal thread 70 of the spindle nut 30 with a nominal diameter DNI, a core diameter DKI, a pitch diameter DFI and an inside diameter Di.

The nominal diameter D _N I of the internal thread 70 is 8.75 mm.

In an alternative embodiment, the nominal diameter D _N I of the internal thread 70 is between 8.7 mm and 8.8 mm.

The core diameter DKI of the internal thread 70 is 6.85 mm.

In an alternative embodiment, the core diameter DKI of the internal thread 70 is between 6.75 mm and 6.95 mm.

The flank diameter DFI of the internal thread 70 is 7.8 mm.

In an alternative embodiment, the flank diameter DFI of the internal thread 70 is between 7.7 mm and 7.9 mm, preferably between 7.75 mm and 7.85 mm.

The diameter Di of the internal thread 70, from which the rounding of the thread crest 88 begins, is at most 7.12 mm.

The internal thread 70 has a flank angle Wi, which is made up of the two partial angles Wn and W21.

In the illustrated embodiment, the two partial angles Wn and W ₂₁ are of equal size, ie each of the partial angles Wn and W ₂₁ is half the size of the flank angle Wi.

The flank angle Wi of the internal thread 70 is 28°.

In an alternative embodiment, the flank angle Wi of the internal thread 70 is between 26.5° and 29.5°, preferably between 27° and 29°.

The profile peaks 86 and profile peaks 88 of the internal thread 70 each have a width Bi of 0.625 mm at the level of the flank diameter D _FI . In an alternative embodiment, the width Bi is between 0.62 mm and 0.63 mm.

The profile valleys 86 of the internal thread 70 each have a rounding 90 which connects the profile flanks 92 of the profile peaks 88 adjacent to the profile italic 86 directly to one another. In other words, the profile valleys 86 are formed without straight profile sections.

Furthermore, the profile valleys 86 are designed without corners.

The roundings 90 of the profile valleys 86 of the internal thread 70 have a first radius Rn at the transition to one profile flank 92 and a second radius R21 at the transition to the opposite profile flank 92.

In the present exemplary embodiment, the radius Rn and the radius R21 are each 0.25 mm, with both radii being able to coincide here, as with the external thread, so that the flanks merge directly into the same radius, so that the profile valley 86 is formed only by this singular radius.

In an alternative embodiment, the radius Rn and/or the radius R ₂ I is between 0.23 mm and 0.27 mm, both radii being the same here as well.

The profile crests 80, 88 of the internal thread 70 and the external thread 72 are thus rounded, preferably with the same singular radius or the two radii Rn and R21 previously indicated.

Due to the rounded profile valleys 78, 86 and the rounded profile peaks 80, 88, the internal thread 70 and the external thread 72 each form a round thread, which, however, does not fall under DIN standards.

To produce the spindle drive 28, the spindle 34 is manufactured as follows.

In one step, the mandrel 34 is heat treated to harden the mandrel

34

In a subsequent step, the spindle 34 is rolled. After rolling, the spindle 34 is no longer heat treated, ie the last heat treatment before rolling was a final heat treatment.

Additionally or alternatively, to produce the spindle drive 28, the spindle nut 30 can be manufactured as follows.

In one step, the spindle nut 30 is rolled.

In a subsequent step, the spindle nut 30 is heat-treated to harden the spindle nut 30.

After the heat treatment, the spindle nut 30 is no longer rolled, i. H. the last rolling before the heat treatment was a final rolling, giving it particularly high strength.

In this way, a spindle drive 28 is provided, which has a particularly small thread diameter due to its finish-rolled spindle 34 and high-strength spindle nut 30 .

Furthermore, the special geometry of the internal thread 70 of the spindle nut 30 and the external thread 72 of the spindle 34 ensures that the spindle drive 28 can be produced reliably by forming such as rolling and thus with particularly little effort.

Furthermore, the special geometry of the internal thread 70 of the spindle nut 30 and the external thread 72 of the spindle 34 ensures that the spindle drive 28 and thus the electric parking brake 100 meets particularly high requirements.

Table 1 below shows several parameters for a thread type "thread A" and a thread type "thread B". The thread type "thread A" corresponds to an exemplary embodiment of the previously explained spindle drive 28 with the special geometry of the internal thread 70 of the spindle nut 30 and the external thread 72 of the spindle 34, while the thread type "thread B" describes a different spindle drive, which is a trapezoidal thread with a geometry based on DIN 103. DIN 103 provides for a pitch of at least 1.5 for a corresponding flank diameter, so that in the example the pitch was reduced by the to improve self-locking. Despite this optimization, the clamping force on thread A is significantly greater, which is the goal.

Table 1

Thread Type S T U V W X Y

Thread A 1.25 7.700 77.98 14.00 0.148 25.11% 18.929

Thread B 1.25 8.375 91.11 15.00 0.148 23.50% 17.715 with S = "pitch", T = "flank diameter [mm]" of the thread pairing, U = "surface pressure at 17kN [Mpa]", V = " Flank angle [°]", W = "Thread friction coefficient", X = "Efficiency" and Y = "Clamping force at 15 Nm [kN]".

As can be seen from Table 1, a reduction in the flank diameter and the flank angle of thread A compared to thread B leads to an increase in efficiency and to a higher clamping force or load capacity of the spindle drive 28.

The brake caliper 10 can be operated as follows.

Starting from the position of the brake piston 20 shown in FIG. 1, it can be displaced to the left, for example by pressurizing the pressure chamber 24 , so that it is applied to the brake lining 18 and presses it against the brake disc 12 . This creates a braking effect.

In this context, the spindle drive 28 is not actuated, i. H. the spindle nut 30 does not move.

When it is displaced in the direction of the brake pad 18, there is a relative movement between the brake piston 20 and the spindle nut 30. This enables the axial guide contour 52.

Alternatively, it is possible for the brake piston 20 to be displaced to the left, starting from the position shown in FIG. 1, by means of the spindle drive 28 of the electric parking brake 100. For this purpose, the electric drive motor 36 is activated and the spindle 34 is rotated. After the spindle nut 30 has been mounted non-rotatably on the brake piston 20 via the anti-twist contour 50, this shifts the spindle nut 30 to the left. In doing so, it is guided by the guide contour 52 .

As soon as the spindle nut 30 hits the bottom section 46 of the brake piston 20, it takes the brake piston 20 with it as it moves to the left.

In this way, the brake piston 20 is applied to the brake pad 18 which in turn is pressed against the brake disc 12 to provide braking as previously discussed.

In this regard, in addition to the aforementioned rotational coupling to the backing plate, the brake piston 20 is frictionally held to the caliper body 14 by virtue of its frictional contact with the seal 62 such that it does not rotate.

As soon as the brake piston 20 is in contact with the brake pad 18, this contact also causes the brake piston to be secured against rotation within the brake caliper body 14.

In this way, the electric parking brake 100 can be adjusted to an engaged state in which it presses the brake pad 18 via the spindle drive 28 with a clamping force of at least 16.5 kN onto the brake disc 12 and thus reliably places the vehicle in a parking or holding position holds.

The invention is not limited to the embodiment shown. In particular, individual features of an embodiment can be combined as desired with features of other embodiments, in particular independently of the other features of the corresponding embodiments.

Furthermore, the electric parking brake 100 can be provided separately from or in combination with any brake of a vehicle, in particular with any brake caliper 10.

Claims

patent claims

1. Electric parking brake (100) with a spindle drive (28) which can be actuated electrically and is self-locking, comprising a spindle (34) with an external thread (72) and a spindle nut (30) with an internal thread (70) which is connected to the External thread (72) is engaged, characterized in that the external thread (72) and the internal thread

(70) have a symmetrical thread profile (74, 76), the profile flanks

(84) of adjacent profile peaks (80) of the external thread (72) via a

Rounding (82) in the intermediate Profi Ital (78) merge directly into one another.

2. Parking brake (100) according to claim 1, characterized in that the rounding (82) of the profile valleys (78) of the external thread (72) has a radius (RI _A , R2 _A ) between 0.18 mm and 0.22 mm, in particular of 0.2 mm, and/or that the profile flanks (92) of adjacent profile tips (88) of the internal thread (70) merge directly into one another via a rounding (90) in the intermediate Profi Ital (86), the rounding (90) of the Profi Itäl he (86) of the internal thread (70) has a radius (Rn, R ₂ I) between 0.23 mm and 0.27 mm, in particular 0.25 mm.

3. Parking brake (100) according to claim 1 or 2, characterized in that the external thread (72) and the internal thread (70) have a flank angle (WA, WI) between 26.5 ° and 29.5 °, preferably between 27 ° and 29°, in particular 28°.

4. Parking brake (100) according to one of the preceding claims, characterized in that the external thread (72) and the internal thread (70) have a pitch between 1.2 mm and 1.3 mm, in particular 1.25 mm.

5. Parking brake (100) according to one of the preceding claims, characterized in that the external thread (72) has a nominal diameter (DNA) between 8.3 mm and 8.4 mm, in particular 8.35 mm.

6. Parking brake (100) according to one of the preceding claims, characterized in that the external thread (72) has a core diameter (DKA) between 6.35 mm and 6.55 mm, preferably between 6.4 mm and 6.5 mm, in particular of 6.45 mm and/or the internal thread (70) has a core diameter (D _Ki ) of between 6.75 mm and 6.95 mm, in particular 6.85 mm.

7. Parking brake (100) according to one of the preceding claims, characterized in that the external thread (72) has a flank diameter (DF _A ) between 7.5 mm and 7.7 mm, preferably between 7.55 mm and 7.65 mm, in particular of 7.6 mm and/or the internal thread (70) has a flank diameter (DFI) of between 7.7 mm and 7.9 mm, preferably between 7.75 mm and 7.85 mm, in particular of 7.8 mm . 8. Parking brake (100) according to one of the preceding claims, characterized in that the profile valleys (78, 86) and profile peaks (80, 88) of the external thread (72) and/or the internal thread (70) are level with the flank diameter (DFA, DFI) each have a width (BA, BI) between 0.62 mm and 0.63 mm, in particular 0.625 mm. 9. Parking brake (100) according to one of the preceding claims, characterized in that the external thread (72) and/or the internal thread (70) has rounded profile tips (80, 88).

10. A method for producing a parking brake (100) according to any one of the preceding claims with the following step: rolling the spindle (34) after a final heat treatment of the spindle (34) and / or heat treatment of the spindle nut (30) after a final rolling of the spindle nut (30).