Cable control unit for a parking brake of a vehicle

Abstract

Electrical control unit for a parking brake with a mounting head to which the parking brake actuating cable is attached, which is subject to a return spring and is driven by a drive and locking mechanism actuated by an electric motor, the unit comprising the following: a drive and locking mechanism consisting of a housing (121) which accommodates a central worm (130) which is connected to the output of the motor (110), - wherein the worm (130) engages with a tubular nut (140) which is connected to the fastening head (123), characterized by the fact that - the tubular nut is provided with an external thread (142) which interacts with the internal thread (152) of a fixed sleeve (150) which is integrally formed with the housing (121), - the internal thread (152) of the sleeve has a pitch that is opposite to that of the thread (131) of the worm (130), and - the thread of the worm (130) is self-locking.

Description

Field of invention

[0001] The present invention relates to an electrical control unit for a parking brake with a mounting head to which the actuating cable of the parking brake is attached, which is subject to a return spring and is driven by a drive and locking mechanism which is actuated by an electric motor. State of the art

[0002] Control devices for a parking brake with an electric motor are known, which are activated, for example, by pressing a button, which can be in conjunction with the gearshift lever for the gear ratios, in order to automatically apply the parking brake or “handbrake” when the vehicle is stopped in the park position.

[0003] Such an automatically applied brake is released by the parking brake control button or, in certain cases, by slight acceleration, in order to send a signal that is interpreted as a command to release the brake.

[0004] Automatic parking brakes with a cable require a special control unit and a motor powerful enough to engage and lock the handbrake. This motor works by means of a reduction gear that tightens or releases the cable to release the brake.

[0005] Certain types of automatic parking brake systems incorporated into motor vehicles use mechanical transmissions to apply the force required to engage the brakes of the rear or front axle of the vehicle. These mechanical transmissions are usually driven by an electric motor that incorporates a reduction gear to convert the angular motion and torque of the motor into a linear offset and a force applied to one or more cables or other transmission means connected to the brakes.

[0006] One of the compromises that has to be made is between the power of the engine (or its torque) and the duration of the pull-in, i.e., the time required to pull the brake.

[0007] Because the lifting force characteristic of vehicle braking systems is not linear, a variable mechanism would be required to optimize the effectiveness of the system while simultaneously having a sufficiently short pull-in time and a sufficiently high pull-in force, which are obtained with the lowest possible motor power.

[0008] From German patent application DE 698 29 083 T2, an electrically actuated brake is known in which the rotary motion of a DC motor is converted into the linear motion of a brake cable by means of a ball recirculation mechanism. The ball recirculation mechanism comprises a threaded part as the input part and a nut that is rotationally fixed relative to the housing as the output part, so that the linear motion of the external threaded part is converted into the linear motion of the nut. A similar design is known from German patent application DE 102 02 729 A1. Object of the invention

[0009] The object of the present invention is to improve the control mechanism of a parking brake with an electric motor by making it possible to optimize the effectiveness of the system and reduce the time required for application, generating sufficient pulling force to lock the vehicle in the park position, and using a low-power motor. Disclosure and advantages of the invention

[0010] In this respect, the object of the invention is a control unit for a parking brake of the type defined above, characterized in that it has a drive and locking mechanism consisting of a housing that accommodates a central worm gear which is connected to the

[0011] The motor output is connected, the worm engaging with a tubular nut connected to the mounting head, the tubular nut having an external thread that interacts with the internal thread of a fixed sleeve integral with the housing, and the internal thread of the sleeve having a pitch opposite to that of the self-locking thread of the worm.

[0012] In this way, the invention enables the realization of a simple and cost-effective mechanism for improving the mechanical properties of the parking brake system by enhancing the utilization of available power. An optimized stroke-force characteristic can thus be achieved simultaneously with a reduced engagement time and an appropriate engagement force using a non-oversized motor whose power output corresponds to the required average value.

[0013] In this way, the invention makes it possible to transmit stronger loads than with known systems or, more generally, to optimize the combination of the following parameters: power or torque of the motor, tensile load in the cable and locking time.

[0014] According to another advantageous feature, the thread of the cuff consists of two parallel threads. Preferably, the same webs adjoin each of these threads.

[0015] Another feature is that the sleeve thread is a variable-pitch thread, and the external thread of the tubular nut is a threaded section. This allows the external thread to be matched to the variable pitch of the sleeve thread, providing a relatively large contact area for transmitting significant loads. This is even more advantageous in the case of a sleeve thread consisting of two or more parallel threads, each accommodating a section of a respective external thread.

[0016] According to one advantageous feature, the tubular nut is integrally formed with the fastening head. However, according to one variant, the tubular nut is slidably connected to the fastening head, while a bearing decouples it from rotation. This facilitates implementation by combining a transmission device and the portion of the fastening head mounted on the transmission device, thus enabling adaptation to various installation scenarios.

[0017] According to another advantageous feature, the internal thread of the sleeve consists of a straight initial segment parallel or substantially parallel to the axis of the worm and a helical segment. In this way, at the beginning of the movement, the offset of the fastening head is equal to the offset produced by the worm, and only then is the offset of the fastening head slowed down and the movement geared to transmit significant loads for tightening.

[0018] According to another advantageous feature, the body of the servo brake consists of a part that accommodates the transmission device and a part that accommodates and guides the mounting head. As explained above, this separate design facilitates the production of a very large variety of servo brakes suitable for numerous applications.

[0019] In summary, it should be noted that the servo brake according to the invention has a simple and cost-effective design and is easy to manufacture and install. drawing

[0020] The present invention is described in more detail below with reference to embodiments of control units for parking brakes with an electric motor, which are illustrated in the accompanying drawings. These show: - Fig. 1 a schematic sectional view of a control unit for parking brakes, - Fig. 2 a sectional view of a variant of the control unit for a parking brake made of Fig. 1, - Fig. 3 A partially sectioned side view of the motion transmission of the parking brake control unit. Fig. 1, - Fig. 3A a simplified sectional view without the housing of the cuff for motion transmission and - Fig. 4 a diagram of the threads of the motion transmission from Fig. 3 of the control unit for a parking brake. Description of embodiments of the invention

[0021] According to Fig. The invention relates to a control unit for a parking brake 100 with an electric motor 110, which is connected to the wheel brakes by a pull cable C. Responding to a command to apply or release the parking brake, the control unit 100 pulls on the cable C to apply and lock the parking brake, or it releases it by loosening the cable C, which is retracted by a spring (not shown).

[0022] The control unit 100, which is aligned on an axis xx, consists of the electric motor 110, which is automatically controlled by a control means in the form of a button (not shown), wherein the motor 110 generally drives a drive and locking mechanism 120 in combination with a reduction gear, which is connected to the head 123, which is attached to the outer end C1 of the cable C.

[0023] The drive and locking mechanism 120 at the output of the motor 110 consists of a housing 121 that accommodates a central worm gear 130 with axis xx, which is connected to the output of the motor 110. This central worm gear 130 is mounted in a bearing 122 of the housing, thus ensuring its locking against displacement while allowing its rotational movement as directed by the motor 110. The central worm gear 130 has a thread 131 extending over part of its length beyond the bearing 122, and it accommodates a tubular nut 140, which is provided with an internal thread 141 along its entire length.

[0024] The nut 140 has an external thread 142 of relatively short length. The nut 140 is in turn received in a sleeve 150, which is provided with a bore 151 that serves as a guide for the unthreaded part 143 of the nut. The sleeve 150 is locked against rotation and displacement in the housing 121, which carries the bearing 122 of the worm gear. The sleeve 150 has a hollow thread 152 in its bore 151, which is composed of a straight part 152A parallel to the axis xx and a helical part 152B. The external thread 142 of the nut 140 interacts with the hollow thread 152, specifically with both its straight part 152A and its helical part 152B, as detailed with reference to the Fig. 3, Fig. 3A, Fig. 4 is explained.

[0025] To actuate the parking brake in response to an engagement command (or a disengagement command), the motor 110 is instructed to rotate the central worm gear 130 in the direction of rotation appropriate for engagement or disengagement. The rotation of the central worm gear 130 displaces the tubular nut 140 through the interaction of its thread 131 and the internal thread 141 of the nut 140. The nut 140, which is itself subject to the hollow thread 152 of the sleeve 150, is forced to perform a combined rotational and displacement movement along the axis xx in the direction of tension of the cable C or in the direction of its loosening.

[0026] The front part of the nut 140 is connected or combined with the head 123, to which the outer end C1 of the cable(s) C of the parking brake is / are attached.

[0027] Fig. Figure 2 shows a variant of an embodiment of the control unit 100A with respect to the nut 140A. This variant differs significantly from the first embodiment in the shape of the nut 140A, which has a rear part 144A connected by a bearing 145A to the fastening head 123A of the outer end C1 of the parking brake cable. The head 123A is guided in the extension 124A of the housing 121A.

[0028] The other parts of the 100A control unit are identical to those of the 100 control unit. Fig. 1 identical.

[0029] According to this embodiment, the part comprising the extension 124a of the housing 121a accommodates the drive head 123a and the guide, thus enabling a very high degree of adaptability to special cases because this part (124a, 123a) is designed independently of the housing 121a and the elements it accommodates. Simple assembly allows adaptation to any application without the need to duplicate the special manufacturing processes.

[0030] The construction of the device 120 for transmitting the motion between the motor 110 and the mounting head 123, 123A of the outer end C1 of the cable C is described in the Fig. 3, Fig. 3A is shown in more detail and in the graphic. Fig. 4 shown schematically.

[0031] Fig. Figure 3 shows the fixed cuff 150 with its bore 151 and its hollow thread 152, which consists of the straight part 152A and the helical part 152B. For the sake of clarity, the hollow thread 152 is shown in Fig. 3 not shown in section, and the other parts of the cuff 150 and the housing 121 are combined and shown together in section, in which the thread 131 of the middle worm 130 as well as the part of the tubular nut 140 which is provided with its external thread 142 and the fastening head 123 are visible.

[0032] According to Fig. 3. The hollow thread 152 of the cuff 150 is indeed bounded by two parallel webs 152a, 152b, which, introduced by the straight segment 152A, have branches 152Aa, 152Ab parallel to the axis xx of the control unit 100. The two branches 152Aa, 152Ab then connect helical webs 152Ba, 152Bb, here with a constant pitch.

[0033] The external thread 142 of the nut 140 consists of a threaded section with a length less than half a turn of the nut, as shown here in Fig. Figure 3 is shaded. This section of the thread 142 has two long sides 142a parallel to the pitch of the helical thread 152B and two short curved sides 142b at the ends. These two short sides 142b are spaced apart by the distance between the two webs 152Aa, 152Ba that adjoin the straight segment 152A of the thread 152. In the case of a thread 152 or 152B with a variable pitch, the thread section 142 would have tapered long sides 142a to improve contact with the thread 152. Because the middle worm 130 is driven by the motor 110 in the direction of tightening, the nut 140 is moved in the direction of S, whereby the rotation of the nut is blocked by the contact of the outer ends or the short sides 142a of the threaded section 142 with the two sides formed by the straight branches 152Aa, 152Ab of the two webs 152a, 152b of the sleeve 150.As soon as the threaded section 142 abuts the first web 152Ba, the locking of the rotation disappears, and the rotation of the nut 140 is released. Its threaded section 142 can therefore follow the helical segment 152B, while being supported and guided by its two long sides 142a between the two web parts 152Ba, 152Bb, which delimit the web 152B.

[0034] The nut 140 moves forward in this way as it rotates, and it controls the pulling motion of cable C.

[0035] Although the foregoing description relates to a single threaded section 142 and a single hollow thread 152, for reasons of symmetry and balancing of loads it is preferred to distribute the loads over several parallel threads 152.

[0036] Therefore and as in Fig. As shown in Figure 3, the thread 152 is tripled by parallel unlabeled threads which adjoin the other sides of the webs 152a, 152b, 152c, which in turn adjoin the thread 152, wherein the section 142 is supplemented by two sections 142S, one of which is in Fig. 3 is partially visible and is located behind the plane of the figure.

[0037] As a result of this parallelism, the thread(s) 142 run along the thread(s) 152 under exactly the same conditions.

[0038] Fig. 3A shows, in simplified form, the Fig. 3 structure shown, in which the cut-off screw 130 with the also cut-off tubular nut 140 and the two individual thread sections 142, 142S as well as the webs 152a, 152b, 152c appear.

[0039] Fig.Figure 4 is a schematic diagram of the transmission device 120 in a plane. The axis OX corresponds to the axis of rotation xx of the worm 130 and the tubular nut 140. The axis Y allows the angle of the depicted threads to be determined. The thread of the worm 130 is represented by the line F0, which passes through the origin at an angle β with respect to the Y-axis. The thread 152 is represented by the segment OB, which runs parallel to and overlaps the axis OX. It corresponds to the straight segment 152A of the thread 152. The helical segment 152B corresponds to the straight segment BC. Because the segment 152B is limited, it is represented by the trace of a straight segment BC.

[0040] The running point of the thread 131, which interacts with the tubular nut 140, is point Mi on axis OX. The running point of interaction between the thread 142 and the thread 152 is running point Pi, located at the intersection between segment BC and the running web Fi, which passes through running point Mi.

[0041] When the web 142 is located above the straight segment 152A, its running point runs along segment OB and its offset corresponds to the offset of the running point Mi of the worm 130. However, when the thread or thread section 142 arrives at the helical segment 152, it follows segment BC. The running point Pi is located at the intersection between this segment BC (thread 142) and that of the thread Fi (thread 152).

[0042] The running point of the nut 140 has a position Pi0 with respect to the axis xx, which is the projection of the running point Pi onto the axis OX. If the inclination β of the thread 131 of the worm 130 and the inclination α of the helical segment 152B of the thread 152, which are opposite, are given, the running point Pi has a projection Pi0 that lies behind the running point Mi, and the nut 140 displaces like the projected running point Pi0.

Claims

[1] Electrical control unit for a parking brake with a mounting head to which the parking brake actuating cable is attached, which is subject to a return spring and is driven by a drive and locking mechanism actuated by an electric motor, the unit comprising: a drive and locking mechanism consisting of a housing (121) which accommodates a central worm (130) which is connected to the output of the motor (110), - wherein the worm (130) engages with a tubular nut (140) which is connected to the fastening head (123), characterized by , that - the tubular nut is provided with an external thread (142) which interacts with the internal thread (152) of a fixed sleeve (150) which is integrally formed with the housing (121), - the internal thread (152) of the sleeve has a pitch that is opposite to that of the thread (131) of the worm (130), and - the thread of the worm (130) is self-locking. [2] Control unit for a parking brake according to claim 1, characterized by , that the thread (152) of the cuff (150) consists of three parallel threads. [3] Control unit for a parking brake according to claim 1, characterized by , that the thread (152) of the cuff (150) is a thread with a variable pitch and the external thread (142) is a thread section. [4] Control unit for a parking brake according to claim 1, characterized by , that the tubular nut (140) is integrally formed with the fastening head (123). [5] Control unit for a parking brake according to claim 1, characterized by, that the tubular nut (140) is slidably connected to the fastening head (123A), while it is decoupled from rotation by a bearing (145A). [6] Control unit for a parking brake according to claim 1, characterized by , that the thread (152) of the sleeve (150) consists of a straight initial segment (152A) that is parallel or substantially parallel to the axis (xx) of the worm (130) and a helical segment (152B). [7] Control unit for a parking brake according to claim 1, characterized by , that the body of the parking brake consists of a part (121A) which receives the transmission device (120) and a part (121B) which receives and guides the fastening head (123A).

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