Patent Application
20240132038
This application claims the benefit of the filing date of European Patent Application No. 22203042.1 filed on Oct. 21, 2022, the entire content of which is incorporated herein by reference in its entirety.
The present disclosure is directed to an electromechanical brake actuator, an electromechanical brake arrangement, and a commercial vehicle.
Document US 20200062230 A1 describes an electromechanical brake actuator for a brake, in particular a commercial vehicle disc brake, which has an electric motor for generating a drive torque, a cam disc operatively connected to the electric motor and mounted in a rotationally movable manner, and a brake plunger or rod which can be moved along a plunger axis for the actuation of a brake lever of the brake.
It would be beneficial to increase the functionality of electromechanical brake actuators.
A first aspect of the present disclosure is directed to an electromechanical brake actuator that includes a service-brake unit and a parking-brake unit. The service-brake unit includes a service-brake rod for applying a variable braking force to an external caliper, in particular of a brake arrangement. The service-brake unit also includes a service-actuation unit that is configured to receive a service-brake signal and, in dependence thereof, to move the service-brake rod to a position between a full braking position, at which a maximum braking force is applied to the caliper, and a drive position, at which a minimum braking force, and in particular no braking force, is applied to the caliper.
The parking-brake unit includes a parking-brake rod that is operatively coupled to the service-brake rod and is movable between a first position, in which the parking-brake rod is arranged to lock the service-brake rod in a braking position, preferably the full-braking position, and a second position, in which the service-brake rod is released from the braking position and is free to be moved by the service-actuation unit. The parking-brake unit also includes a parking-actuation unit including a spring element that is operatively coupled to the parking-brake rod and arranged so that, in a fully-compressed state of the spring element the parking-brake rod is in the second position, and in a fully-released state of the spring element the parking-brake rod is in the first position. The parking-actuation unit further includes a hydraulic unit that is operatively coupled to the parking-brake rod and configured to receive a parking-brake signal and, in dependence thereof, to selectively lock the parking brake rod at a given current position or allow a release of the spring element to the released state.
Thus, the electromechanical brake actuator includes a service-brake rod that is configured to apply a variable braking force to a caliper in dependence on a service-brake signal that is received by the service-actuation unit. The service-brake rod has a stroke length delimited by two end positions, namely the full braking position and the drive position, and the braking force applied to the caliper varies in dependence on the position. In particular, the braking force increases monotonically from a minimum braking force, preferably a vanishing force, when the service-brake rod is in the drive position, and a maximum braking force when the service-brake rod is at the full braking position. When the service-actuation unit drives the service-brake rod to an intermediate position, i.e. a position between the full braking position and the drive position, a braking force amount with a value between the maximum braking force and the minimum braking force is applied to the caliper. The electromechanical actuator also includes a parking-brake rod. The parking-brake rod is operatively coupled to the service-brake rod, i.e., that operation of the parking-brake rod has an effect on the operation of the service-brake rod. The parking-brake rod is operatively coupled and actuated by a spring element, such that a change in the state of the spring element is directly coupled to a change in the position of the parking-brake rod. In a fully compressed state, the spring element drives the parking brake rod to be in the second position, which allows the service-brake rod to be moved by the service-actuation unit. When the spring element is in the fully released state, the parking-brake rod is at the first position. In this position, the parking-brake rod is configured to actuate on the service-brake rod and to force and lock the latter in a braking position, preferably the full-braking position, irrespectively of the service-brake signal. The braking position is a position in which a braking force necessary for a parking-brake function is applied to the caliper. This braking position preferably but not necessarily corresponds to the full-braking position. A position of the parking-brake rod between the first and the second position is correlated to the spring element being in a semi-compressed state. The spring element states, e.g. fully compressed or fully-released are understood as the states of the spring element when used in the brake actuator and may differ from the states of the spring when considered alone. There might be mechanical restrictions imposed by other elements of the brake actuator limiting the intrinsic expansion or compression capabilities of the spring element. The state of the spring element, and thus the position of the parking brake rod, is controlled by the hydraulic unit, which is operatively coupled to the parking-brake rod. The hydraulic unit is configured to receive the parking-brake signal and, in dependence thereof, to lock the parking brake rod at any given position along the stroke length of the parking-brake rod. Also in dependence on the parking-brake signal, the hydraulic unit is configured to allow a movement of the parking-brake rod, which is caused by the spring element being free to adopt the fully released state, which causes the parking-brake rod to move to the first position forcing the service-brake rod in the full braking position. The brake actuator of the first aspect of the disclosure is thus a combined electromechanical brake actuator that enables a service-braking function and a parking-braking function which can be implemented without a pneumatic system.
In the following, developments of the electromechanical brake actuator of the first aspect of the disclosure will be described.
In a development, the service-brake rod and the parking-brake rod are arranged longitudinally along a common longitudinal direction. Preferably, a stroke length amount of the service-brake rod, i.e. a distance between the full braking position and the drive position is substantially identical in magnitude to a stroke length amount of the parking-brake rod, i.e. a distance between the first position and the second position.
In a preferred development, the service-actuation unit, when driving the service-brake rod to the drive position, also drives the parking-brake rod to the second position. Upon reaching the second position, the hydraulic unit is configured to lock the position of the parking-brake rod. Thus, the service-actuation unit is further arranged and configured to compress the spring element thereby driving the parking-brake rod to the second position.
In a preferred development, the service-brake signal and the parking brake signal are electrical signals provided to the service-actuation unit and to the parking-actuation unit respectively. In some developments a lack of voltage/current is also interpreted as an electric signal that controls the operation of the service-actuation unit and/or of the parking actuation unit. For example, in a development, when the service-brake signal drops to 0 V or 0 A, the service-actuation unit is configured to control a movement of the service-brake rod to the drive position. In another development, when the parking-brake signal drops to 0 V or 0 A, the parking-actuation unit is configured to allow a release of the spring element to the fully-released state.
In another development, the hydraulic unit includes a hydraulic cylinder including a piston chamber and a piston arranged inside the piston chamber. The piston is operatively coupled to the parking-brake rod. The hydraulic unit further comprises a first chamber and a second chamber in fluid communication with the first chamber via a fluid passage. An electrically controlled valve unit is configured to receive the parking-brake signal and is arranged and configured to selectively block or enable a flow of a hydraulic fluid via the fluid passage between the first chamber and the second chamber. The first chamber, the second chamber, and the fluid passage between them thus form a closed system such that when the fluid passage is closed, the piston is forced to stay at its current position, which also locks the parking-brake rod in its current position, even against the spring forced exerted by the spring element in a semi-compressed state or a fully-compressed state. When the fluid passage is open, the hydraulic fluid may travel between the chambers and the piston is free to move. The spring element adopts the released state moving the parking-brake rod to the first position locking the service brake rod at the braking position, preferably the full-braking position.
Preferably the hydraulic system is a closed system without any oil-line to an exterior of the electromechanical brake actuator or with only a filling port for filling oil into the hydraulic system.
In a development, the hydraulic cylinder is a double acting cylinder. In the double acting cylinder, the first chamber and the second chamber are located inside the double acting cylinder and separated by the piston. A double acting cylinder is a cylinder in which the working fluid, e.g. the hydraulic fluid, acts alternately on both sides of the piston. In order to connect the piston in a double-acting cylinder to the parking-brake rod, acting as a crank shaft, a hole is provided in one end of the cylinder for the parking-brake rod, and this is fitted with a sealing element to prevent escape of the working fluid.
Alternatively, in another development, the hydraulic cylinder is a single-acting cylinder, wherein the first chamber is located inside the hydraulic cylinder and the second chamber is a reservoir arranged outside the hydraulic cylinder. A single acting cylinder is a cylinder in which the working fluid acts on one side of the piston only. A single acting cylinder typically relies on the load, springs, vacuum, other cylinders, the momentum of a flywheel or any other suitable unit, to push the piston back in the other direction.
In a preferred development the electronically controlled valve unit comprises a manifold valve, in particular a solenoid valve, preferably a 2/2-way solenoid valve. The manifold valve is operable in a first state (also referred to as an open first state) in which a first port of the manifold valve, which is in fluid communication with the first chamber, is connected to a second port of the manifold valve, which is in fluid communication with the second chamber. Thus, in the open first state a movement of the piston inside the hydraulic cylinder is enabled. The manifold valve is further operable in a closed second state in which the first port is disconnected from the second port and therefore a movement of the piston inside the hydraulic cylinder is hindered. In particular, in the open first state, the piston is free to move, by action of the spring element adopting the released state, to a position that brings the parking-brake rod to the first position. This activates the parking-brake function of the brake actuator. Also, in the open first state, the piston is free to move in response to the service-actuation unit driving the service-brake rod to the drive position, which in turn causes the parking-brake rod to move to the second position. Once in this position, and upon reception of a suitable parking-brake signal, the manifold valve closes the fluid passage and the piston (und thus the parking-brake rod) is locked in said second position.
In a preferred embodiment, the open first state is an unactuated state of the manifold valve, in particular of the 2/2-way solenoid valve, and the closed second state is an actuated state of the manifold valve, in particular the 2/2-way solenoid valve. Thus, the manifold valve is operated as a NO (normally open) valve. This has the advantage that an electrical signal is needed to lock the spring element in the fully-compressed state, allowing a normal operation of the service-braking function based on the electric service-brake signal. Should be a failure in the electric system, which may affect the service-brake functionality, the parking-brake signal is no longer provided, which automatically triggers the parking-brake functionality. Further, the parking-brake functionality can only be ended if energy supply is present for actuating the manifold valve and, optionally, for operating the service-actuation unit.
In another development, the manifold valve is a bi-stable manifold valve wherein a provision of a short pulse as the parking-brake signal is configured to actuate the manifold valve and change the operation state from the open first to the closed second state and vice versa.
In another development, the hydraulic unit alternatively or additionally comprises a flow-control unit arranged between the electrically controlled valve unit and the hydraulic cylinder for controlling a flow amount between the first chamber and the second chamber. Preferably, the flow-control unit is a throttle valve or a restrictor. Preferably, the flow-control unit is further configured to switch between two flow resistances values. In particular, in a development, the flow-control unit is configured to set a first flow resistance value to a first flow path from the first chamber to the second chamber and a second flow resistance value to a second flow path from the second chamber to the first chamber. This development enables a slow relaxation of the spring element to the released state, which correlates to an engagement of the parking brake, and a faster (compared to the relaxation) tensioning of the spring element, which correlates to a release of the parking brake.
In a preferred development, which may include any of the technical features described above, the hydraulic unit further includes an emergency-release unit that is operatively coupled to the parking-brake rod and configured to drive the parking-brake rod to the second position independently of the service-actuation unit.
In a particular development, the emergency-release unit includes an emergency-release screw, preferably for manual actuation, for moving the parking-brake rod. Preferably, in addition, the emergency-release unit also includes a manual valve actuator for controlling the hydraulic unit independently of the electric parking-brake signal. In a development, the piston is operatively coupled to a threaded screw which is coupled to a cooperating nut that is manually or mechanically or otherwise drivable. Rotating the threaded nut causes the screw to move relative to the nut, which in turn drives the piston and also drives the parking-brake rod to the second position, compressing the spring element. This type of emergency-release unit can be used to bring the piston to virtually any reachable position within the piston chamber. However, the main functionality is to compress the spring element, so that the service-brake rod is no longer locked in the (full) braking position. Optionally, in a development wherein the movement of the piston is blocked by the hydraulic unit in these circumstances, a manual valve actuator for controlling the hydraulic unit is provided, which, independently of the provision of the parking-brake signal, is configured to allow a free movement of the piston, for instance, by enabling a fluid communication between the first and the second chamber.
A second aspect of the present disclosure is formed by an electromechanical brake arrangement. The electromechanical brake arrangement includes an electromechanical brake actuator according to the first aspect of the present disclosure.
The inventive electromechanical brake arrangement also includes a caliper operatively coupled to the service-brake rod and configured to apply the braking force to a brake disc. The amount of the braking force is dependent on a position of the service-brake rod, as explained above. The electromechanical brake arrangement also includes a brake control unit that is in signal communication with the service-actuation unit and with the parking-actuation unit, preferably via a CAN bus or a dedicated wired or wireless connection, and configured to generate and provide the service-brake signal and the parking-brake signal to the service-actuation unit and to the parking-actuation unit, respectively.
The electromechanical brake arrangement of the second aspect of the disclosure thus shares the advantages of the electromechanical brake actuator of the first aspect or of any of its developments.
A third aspect of the present disclosure is formed by a commercial vehicle, in particular an electric commercial vehicle, including an electromechanical brake arrangement according to the second aspect of the disclosure. In the commercial vehicle of the third aspect, a respective brake disc is connected to a corresponding wheel of the vehicle.
The commercial vehicle of the third aspect of the disclosure thus shares the advantages of the electromechanical brake actuator of the first aspect and/or of the electromechanical brake arrangement of the second aspect of any of their developments.
It shall be understood that a preferred embodiment of the present disclosure can also be any combination of the various developments or above embodiments with the various aspects of the disclosure.
These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter.
The embodiments of the present disclosure are described in the following on the basis of the drawings in comparison with the state of the art, which is also partly illustrated. The latter is not necessarily intended to represent the embodiments to scale. Drawings are, where useful for explanation, shown in schematized and/or slightly distorted form. With regards to additions to the lessons immediately recognizable from the drawings, reference is made to the relevant state of the art. It should be borne in mind that numerous modifications and changes can be made to the form and detail of an embodiment without deviating from the general idea of the present disclosure. The features of the present disclosure disclosed in the description, in the drawings, and in the claims may be essential for the further development of the present disclosure, either individually or in any combination.
In addition, all combinations of at least two of the features disclosed in the description, drawings and/or claims fall within the scope of the present disclosure. The general idea of the present disclosure is not limited to the exact form or detail of the preferred embodiment shown and described below or to an object which would be limited in comparison to the invention as claimed in the claims. For specified design ranges, values within the specified limits are also disclosed as limit values and thus arbitrarily applicable and claimable.
Various aspects of the present disclosure are shown in the following drawings, in which:
There are known combined emergency-brake and parking brake actuator for air disc brakes. In addition to a service chamber for service brake actuation, there is an additional parking chamber for the parking brake actuation. A spring is placed in this chamber. For normal usage of a service brake, pressure is applied to the parking chamber. The spring is compressed, hence no spring-force is applied on the pushrod. A clamping or braking force is generated by pressurizing the service chamber. Without pressure applied on the parking chamber, spring expand and generates a clamping force onto the pushrod. This functionality can be used for an emergency brake and park brake functionality: The spring will apply brake forces without any pressuring/energy supply to any of the chambers. In addition to that an emergency release functionality is integrated. In case of failure or service the spring can be compressed manually. A nut can be fastened in order to compress the spring. By this the brake is released manually.
The electromechanical brake actuator of the present disclosure offers an increased functionality similar to that of air-disc brakes, without the need to use a pneumatic system.
The electromechanical brake actuator 100 includes a service-brake unit 102 and a parking-brake unit 110. The service-brake unit 102 includes a service-brake rod 104 arranged and configured to apply a variable braking force F to the caliper. The service-brake rod 104 is actuated by a service-actuation unit 106 that is configured to receive a service-brake signal SS from the brake control unit and in dependence thereof, to move the service-brake rod 104 to a corresponding position P between a full braking position BP and a drive position DP. The full braking position is that position P at which a maximum braking force Fmax is applied to the caliper 502 and the drive position DP, at which a minimum, preferably no braking force F, is applied to the caliper 502. The service-actuation unit 106 may include a pinion-and-rack system for moving the service-brake rod 104. For instance, a rack element 109 is attached to the service-brake rod 104 and a pinion 108, driven for example by an electromotor (see
The electromechanical brake actuator 100 also includes a parking-brake unit 110, which includes a parking-brake rod 112 and a parking-actuation unit 114. The parking-brake rod 112 is operatively coupled to the service-brake rod 104 and is movable between a first position P1, in which the parking-brake rod 112 is arranged to lock the service-brake rod 104 in a braking position, preferably the full braking position BP, and a second position P2 in which the service-brake rod 104 is released from the braking position BP and free to be moved by the service-actuation unit 106. Thus, when the parking-brake rod 112 is in the second position P2, the service-brake rod 104 is free to be moved by the service-actuation unit 106 to any position P between the full-braking position BP and the drive position DP. When the parking-brake rod 112 is in the first position P1, the service-brake rod 104 is forced to be at the braking position, which is preferably the full-braking position BP. In this case, the service-brake rod 104 cannot be moved by the service-actuation unit. In embodiments where the braking position at which the service-brake rod 104 is forced when the parking-braking rod 112 is in the first position P1 is not the full-braking position FB, the service-braking rod may be movable by the service-actuation unit 106 to any position between the full braking position FB and the braking position. The service-actuation unit 106 is optionally further arranged and configured to compress the spring element 116 and to drive the parking-brake rod 112 to the second position P2.
In
The parking-brake unit 110 also includes a parking-actuation unit 114 for actuating the parking-brake rod 112. The parking-actuation unit 114 includes a spring element 116 that is operatively coupled to the parking-brake rod 112. The spring element 116 is arranged so that in a fully-compressed state CS of the spring element 116, the parking-brake rod 112 is in the second position P2, and in a fully-released state RS of the spring element 116, the parking-brake rod 112 is in the first position P1. The parking-actuation unit 114 further comprises a hydraulic unit 118 that is operatively coupled to the parking-brake rod 112 and configured to receive a parking-brake signal PS, for instance, from the brake control unit 504, for example in response to the driver actuating a parking-brake interface (not shown). In dependence on the received parking-brake signal PS, the hydraulic unit 118 is configured to lock the parking-brake rod 112 at a given current position, or to allow a release of the spring element 116 to the released state RS.
In the exemplary electromechanical brake actuator 100, the hydraulic unit 118 includes a hydraulic cylinder 120 including a piston chamber (121, see
The first chamber 124 and the second chamber 126a, 126b are in fluid communication via a fluid passage 128. An electrically controlled valve unit 132 is configured to receive the parking-brake signal PS and it is arranged and configured to control, i.e., to block and enable, a flow f of a hydraulic fluid 130 via the fluid passage 128 between the first chamber 124 and the second chamber 126a, 126b.
Typically the first chamber 124, whose volume depends on the position of the piston 122 is filled with hydraulic fluid, such as oil or any other suitable fluid. When the parking-brake rod 112 is moved from in the direction of the second position P2 (for example actuated by the service-actuation unit 106 via the service-brake rod 104), the volume of the first chamber 124 increases and hydraulic fluid 130 is drawn from the second chamber 216a, 126b for filling the added volume. This is possible only if the hydraulic unit 118 is in a state where a flow f through the fluid passage 128 is enabled. If not, the piston 122 will substantially remain at its position and the parking-brake rod 112 will practically not move in either direction, not even by the force exerted by the spring element 116. The amount of movement possible is given by the compressibility of the hydraulic fluid 130.
If the state of the hydraulic unit 118 changes and a flow f between the first chamber 124 and the second chamber 126a, 126b is enabled, the spring element 116 will be released towards its released state RS, driving the parking-brake rod 112 towards the first position P1 (and therefore the service-brake rod towards the (full) braking position). The volume of the first chamber will be reduced because the piston 122 is indirectly driven (i.e. by means of the parking-brake rod 112) by the spring element 116. The hydraulic fluid f flows out of the first chamber 124 and into the second chamber 126a, 126b.
Optionally, the hydraulic unit 118 includes a flow-control unit 136, for instance a throttle valve or a restrictor, that is arranged between the electrically controlled valve unit 132 and the hydraulic cylinder 120 and configured to control the flow amount f between the first chamber 124 and the second chamber 126a, 126b.
Also optionally, the hydraulic unit 118 further includes an emergency-release unit 140 that is operatively coupled to the parking-brake rod 112 and configured to drive the parking-brake rod 112 to the second position P2 independently of the service-actuation unit 106. In this particular example, the emergency-release unit 140 includes an emergency-release screw 140a for moving the parking-brake rod 112 and, optionally, a manual valve actuator 140b for controlling the hydraulic unit 118 independently of the electric parking-brake signal PS. For example, in the case of power loss, the electrically controlled valve unit 132 switches to an operating state in which a fluid communication between the first chamber 124 and the second chamber 126a, 126b is enabled. The compressed spring element 116 is then free to expand towards the fully-released stated RS, the parking-brake rod is moved towards the first position and the service-brake rod is locked at the (full) braking position BP. Since there is no power, the service-actuator unit 106 cannot operate the service-brake rod 104 towards the drive position DP. Should a user want to liberate the service-brake rod, he or she has the possibility to use emergency-release unit 140, for instance by actuating the emergency-release screw 140a to draw the parking-brake rod 112 from the first position P1 towards the second position P2.
In cases where the electrically controlled valve unit 132 blocks a fluid connection between the first chamber 124 and the second chamber 126a, 126b, the electrically controlled valve unit 132 may include a manual valve actuator 140b for controlling the hydraulic unit 118 independently of the electric parking-brake signal PS. Thus the state of the valve unit 132 can also be manually controlled to allow operation of the emergency-release unit 140.
In the electromechanical brake arrangement 500 of
The brake control unit 504 is in signal communication with the service-actuation unit 106 and the parking-actuation unit 114 and configured to generate and provide the electric service-brake signal SS and the electric parking-brake signal PS to the service-actuation unit 106 and the parking-actuation unit 114 respectively.
Thus,
Further, the manifold valves 134 of
Thus, this particular mechanism can be used as a self-clamping parking brake. i.e. a parking brake designed to apply brake force to the caliper in case of power loss in the braking system.
In another embodiment (not shown), the electrically controlled valve unit comprises a bi-stable valve, wherein a parking-brake signal in the form of a pulse triggers a change in the state of the valve, which remains in said state until another pulse is provided, or, in a particular embodiment, a manual valve actuator is operated.
A parking-brake rod 112 is operatively coupled to the service brake rod 104. It also includes a support element 115 that is arranged and configured to support the spring element 116 and to compress the spring element 116 when the parking-brake rod 112 moves towards the second position P2.
In the electromechanical brake actuator 200 of
Alternatively,
In a particular embodiment (not shown) the elements of the flow control unit, optionally including the electrically controlled valve unit are integrated into a housing of the spring element.
Before the service brake can be applied, the parking brake mechanism, also referred to as emergency brake is to be put in operation. As described above, for the state of no energy supply, the spring element 116 is in its fully-released state RS and thus expanded. The brake is clamped because a braking force F is applied to the caliper via the service-brake rod 104. To release the brake, the valve unit 132 is switched to the “open” state, the service-brake rod 104 is moved to right-hand end position, i.e., towards the drive position by the service-actuation unit 106 which drives the parking-brake rod 112 towards the second position P2. Once end positions DP, P2 are reached, the valve unit 132 is switched to the “close” state.
While the service-actuation unit 106 drives the service-brake rod 104 and the parking-brake rod 112 to their respective final positions DP, P2, i.e. while the spring element 116 is being forced towards the fully-compressed state, no controlled brake force F can be applied to the wheels 1002, which can cause heavy safety issues. To avoid this, it is preferred that the wheels are to be put in operation sequentially. Starting at one wheel-end or two wheel-ends per axle the process explained above is applied. After completed, a brake force shall be applied to that particular wheel or wheel-end via service brake functionality. Now a first axle is in operation. Afterwards the same process can be applied to the next axle until all wheel-ends are in operation.
In summary, the present disclosure is directed to an electromechanical brake actuator configured to move a service-brake rod between a full-braking position and a drive position. A parking-brake rod is coupled to the service-brake rod and movable between a first position for locking the service-brake rod in the full-braking position, and a second position where the service-brake rod is free to be moved. A spring element is coupled to the parking-brake rod and arranged so that in a fully-compressed state the parking-brake rod is in the second position, and in a fully-released state, the parking-brake rod is in the first position. A hydraulic unit is operatively coupled to the parking-brake rod and configured, in dependence on a parking-brake signal, to lock the parking-brake rod, and also to allow a release of the spring element to the fully-released state.
Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.
A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Any reference signs in the claims should not be construed as limiting the scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22203042.1 | Oct 2022 | EP | regional |
