Patent Application
20050104452
The present invention relates to a method and an arrangement for controlling a device that is dependent upon current direction in an electrical circuit, preferably in a safety-critical system, by means of the position of a key.
Mechanical key locks ate being replaced increasingly by electromechanical or electrical key locks that have a key with electronic components and a position function that is dependent upon shape. The electronic components in the key activate the locked functions when the key is in the correct position in a key seat in the lock. Such electrical key locks are found, for example, in cars with ignition locks and steering locks. With an electrical steering lock, the steering of the vehicle is usually locked by a bolt that is moved between a closed and an open position by means of a motor, a solenoid or similar electrically controlled component. The steering lock application is an example of a safety-critical system, in which it must be ensured that the steering of the vehicle is always unlocked when the electrical key lock is in the unlocked position.
The patent publication WO 01/23229 (Marquardt GMBH) shows an example of an electrical steering lock that addresses this safety problem. This publication describes an electrical steering lock that is locked by means of an actuator that can be switched electrically between a locked and an unlocked state. The electrical steering lock has an electrical circuit with constant supply of the current that is required to put the steering lock in an unlocked state, and a separate electrical circuit for supplying the current that is required to put the steering lock in a locked state. In the locking electrical circuit, there are switches that break the locking electrical circuit when a key is in a certain position in a key seat. In this way, a control processor that controls the actuator is prevented from changing the steering lock to a locked position when the key is in a particular position, but can always change the actuator to an unlocked state. This publication is hereby incorporated, by means of this reference, as a description of the known part of the implementation of the invention.
This prior art has limitations in that the correct key position only prevents changing the actuator to one state (locked), while changing the actuator to the other state (unlocked) is allowed constantly in any key position. The safety function in this known technology is thus a switch that opens the locking electrical circuit when the key is in the unlocking position and thereby prevents unintentional locking of the steering. A short circuit can, however, arise in the switches or in some other location, possibly simultaneously with a bit error in the microprocessor, so that the locking electrical circuit can still pass current through the actuator and unintentionally lock the steering. In the technical solution that is described in WO 01/23229, switches are used in the form of relays with two positions, that is each relay is always activated in one or the other position. In order not to have the actuator (the motor 4) permanently activated, after the completion of activation, the microprocessor must make both the relays connect the motor's feeds to the same voltage. A short circuit to voltage in the relay or the feed that operates the motor for the locked position means that the motor immediately moves the bolt to the locked position, even when this is not the intention.
According to the technical solution in WO 01/23229, there is, in addition, no way of detecting whether the safety function has failed due to a fault, without additional information and logic. If, for example, due to a fault, there is a constant voltage at the input to the relay for supplying voltage for locking, it is not possible to detect this by the microprocessor or via function interference. In other words, in the event of such a fault the whole safety function is lost, without the user, in this case the driver of the car, detecting function interference or other warning.
The present invention aims to solve the general problem of ensuring correct control of an electrical or electromechanical actuator that is operated in response to a digitally controlled electronic locking system.
Aspects of the problem that the invention intends to solve are:
According to the invention, the above-mentioned problem and limitations are eliminated and this is achieved by means of a locking device with key-activated switches for a supply voltage that can be disconnected, together with control unit-activated switches that are arranged to be connected to an actuator of some kind, preferably a motor, solenoid or the like. The control unit-activated switches are connected symmetrically to the actuator in order to allow an electrical current through the actuator in different directions alternately. The control unit-activated switches are electrically arranged so that they are mutually exclusive. In the event of an incorrect control signal from the control unit, or in the event of a short circuit to the earth potential or the supply voltage, current is passed to earth while the actuator is without current. The mutually exclusive conducting of current in different directions is found in different embodiments, realized with key-activated switches, with control unit-activated switches, in the control unit's predetermined conditions, and in the conducting of the supply voltage from the key-activated switches.
The invention therefore achieves a fail-safe control of current to an actuator, in which faults in the control or short circuits are prevented from unintentionally activating the actuator. Such faults are also able to be detected by loss of function that can be observed.
Different embodiments of the invention comprise the following aspects:
A locking device for controlling an actuator that is dependent upon current direction, comprising a key-receiving device (4) arranged to receive a key (2), with the key-receiving device (4) comprising a first key-activated switch (6) that is arranged to close a first electrical circuit (7) when the said key is not in a predetermined position in the key-receiving device (4); a control unit (16) that emits a first control signal (L) for activating the supply of current in a first direction to the said actuator (13) and a second control signal (U) for activating the supply of current in a second direction to the said actuator (13) in response to predetermined conditions; with a second key-activated switch (8) that is arranged to close a second electrical circuit (9) when the said key (2) is in a predetermined position in the key-receiving device (4); first control unit-activated switches (14-L) that are arranged to close the said first electrical circuit (7) when the said control unit (16) emits the said first control signal (L) and second control unit-activated switches (14-U) that are arranged to close the said second electrical circuit (9) when the said control unit (16) emits the said second control signal (U). The first (14-L) and the second (14-U) control unit-activated switches are preferably arranged in such a way that they must be mutually exclusively open or closed in order for a current to be able to pass through the actuator (13).
This can be realized in such a way that the actuator (13) is connected by its electrical connections between a pair of first control unit-activated switches (14-L) that are in turn connected to conduct current in the said first electrical circuit (7) in a first direction between the earth potential (GND) and the supply voltage (10); and the actuator (13) is connected by its electrical connections between a pair of second control unit-activated switches (14-U) that are in turn connected to conduct current in the said second electrical circuit (9) in a second direction between the earth potential (GND) and the supply voltage (10). By this means, it can be arranged that one of the first control unit-activated switches (14-L) is connected to the earth potential (GND), to one connection of the actuator (13) and to one of the second control unit-activated switches (14-U) that is connected to a supply voltage (10,6) that can be disconnected; and the second of the first control unit-activated switches (14-L) is connected to a supply voltage (10,8) that can be disconnected, to the second connection of the actuator (13) and to the second of the second control unit-activated switches (14-U) that is connected to the earth potential (GND).
In different embodiments, it is arranged that:
In a general embodiment, the locking device according to the invention comprises a control unit (31): with a first input IN1 which is arranged to be connected to the supply voltage (10) via the first key-activated switch (6) in such a way that it can be disconnected and with a second input IN2 which is arranged to be connected to the supply voltage (10) via the second key-activated switch (8) in such a way that it can be disconnected;
The invention will be described in greater detail below with reference to the attached drawings in which:
The key-receiving device 4 is provided with a first key-activated switch 6 arranged to close a locking electrical circuit 7 when the key 2 is not in a predetermined position in the key-receiving device (“key removed”), which key-receiving device is intended for the key when it is in the lock in a preferably unlocking position, and the lock is thus in a locking state. When the key 2 is placed in the said predetermined position in the lock (“key inserted”), this first key-activated switch 6 is opened and current is thereby prevented from passing through the locking electrical circuit.
The key-receiving device 4 is also provided with a second key-activated switch 8 arranged to close an unlocking electrical circuit 9 when the key 2 is placed and remains in the said predetermined position in the key-receiving device (“key inserted”), which key-receiving device is intended for the key when it is in its preferably unlocked position in the lock, and the lock is thus in an unlocking state. When the key 2 is removed and thus is not in the said predetermined position in the lock, this second key-activated switch 8 is opened and current is thereby prevented from passing through the unlocking electrical circuit.
The locking electrical circuit 7 and the unlocking electrical circuit 9 are connected to a control unit-activated switching device 12 that comprises control unit-activated switches 14 with locking switches L and unlocking switches U. The locking electrical circuit 7 is connected to an actuator 13 that is dependent upon current direction, which actuator is connected to the supply voltage 10 via an earth potential GND and via the said locking switches 6,L, and the actuator 13 is thereby able to be caused to operate in a predetermined locking direction. In the same way, the unlocking electrical circuit 9 is connected to the actuator 13 that is dependent upon current direction, which actuator is connected to the supply voltage 10 via the earth potential GND and the said unlocking switch 8,U, and the actuator 13 is thereby able to be caused to operate in a predetermined unlocking direction.
The actuator 13 that is dependent upon current direction is preferably, for example, in the form of an electromechanical device, for example a motor M as shown in
In the exemplifying embodiment in
The control unit 16 has a number n of inputs I1, I2 . . . In for different input signals that can be used in accordance with predetermined rules for controlling locking or unlocking. In the embodiment of the invention according to
According to the invention, in order to achieve a current in the locking electrical circuit 7, it is necessary for the key 2 not to be in the position for unlocking and hence for the key-activated locking switch 6 to be closed, and it is necessary for the control unit 16 at the same time to send an active locking control signal L to the control unit-activated locking switch L and to have an inactive unlocking control signal U. In a corresponding way, to achieve a current in the unlocking electrical circuit 9, it is necessary for the key 2 to be placed in the position for unlocking and hence for the key-activated unlocking switch 8 to be closed, and it is necessary for the control unit 16 at the same time to send an active unlocking control signal U to the control unit-activated switch U and to have an inactive locking control signal L. The control signals from the control unit 16 at the output F must thus satisfy the Boolean condition (L=Active AND U=Inactive) OR (L=Inactive AND U=Active) in order to activate the actuator. Together with the key-activated switch for voltage supply, the risk of unintentional activation of the actuator due to an individual bit error or short-circuit is considerably reduced.
In a corresponding way, a second key-activated switch 8 in an unlocking electrical circuit is connected to the supply voltage 10 and a first control unit-activated switch 14-U in the unlocking electrical circuit which first switch is in turn connected to the actuator 13 on the same connection as the locking electrical circuit's first switch 14-L. In addition, the actuator 13 is connected, on the same connection as the locking electrical circuit's second switch 14-L, to a second control unit-activated switch 14-U in the unlocking electrical circuit, which second switch is in turn connected to earth.
When the control unit's locking control signal L is active, the locking switches 14-L are caused to close the locking electrical circuit and when the key-activated switch 6 also closes the locking electrical circuit, that is when the key is removed from its unlocking position in the lock, the actuator 13 is activated into a locking state. In order for current to be able to pass to the actuator through the locking electrical circuit, it is also necessary for the control unit's unlocking control signal U to be inactive, so that the unlocking switches 14-U remain in the open position. Otherwise, the current goes directly to the earth potential GND via the unlocking switches 14-U.
In a corresponding way, when the control unit's unlocking control signal U is active, the unlocking switches 14-U are caused to close the unlocking electrical circuit and when the key-activated switch 8 also closes the unlocking electrical circuit, that is when the key is placed in its unlocking position, the actuator 13 is activated into an unlocking state. As in the case for locking, in order for current to be able to pass to the actuator through the unlocking electrical circuit, it is also necessary for the control unit's locking control signal L to be inactive, so that the locking switches 14-L remain in the open position. Otherwise, once again the current goes directly to the earth potential GND via the locking switches 14-L.
In different embodiments, the locking or unlocking control signals from the control unit 16 can be divided into two, three or four separate signals (L,U; L1,L2,U; L,U1,U2; L1,L2,U1,U2) which, together with the key-activated switches 6, 8 in the correct combination in accordance with a predetermined logical condition, close the locking or unlocking electrical circuit through the activator.
Any short-circuit 11 to voltage or earth in any one of the switches or leads cannot by itself give rise to activation of the actuator. In order to operate the actuator in any current direction, an active control is required by means of control signals from the control unit. The result of a fault is either that activation is carried out in accordance with the conditions of the control logic or that activation is not carried out and the fault can be observed by a user.
The control unit 31 is arranged functionally in such a way that the input IN1 is connected galvanically, that is conducting electrical current, to the input/output I/O1, and the input/output I/O2 is connected to the earth potential GND if a number of first predetermined conditions are fulfilled, and thus allows operation of the actuator in a first current direction, provided that the first key-activated switch 6 is also closed. In the steering lock application, this would result in a locking mode. In the same way, the control unit 31 is arranged in such a way that the input IN2 is connected to the input/output I/O2, and the input/output I/O2 is connected to the earth potential GND if a number of second predetermined conditions are fulfilled, and thus allows operation of the actuator in a second current direction, provided that the second key-activated switch 8 is also closed. In the said steering lock application, this would consequently result in an unlocking mode. The different conditions can be varied to suit the application and requirements and are realized by different types of technology, but the first and second predetermined conditions for operation of the actuator in the said first or second current direction must be mutually exclusive. Similarly, the actual physical or galvanic connections for different current direction circuits can be realized in different ways, but these electrical connections must also be mutually exclusive.
The logic that is to handle the control conditions can be designed in various ways, among other things depending upon what type of fault occurrence is to be monitored. A general example of a logical control condition is:
The invention can be utilized in various applications where there is preferably a safety-critical function that depends on the operation of an actuator in a certain current direction. In the exemplifying embodiments, an example has been shown with a key lock, for example a steering lock in a vehicle. The invention is primarily suited for antitheft applications in vehicles, but other applications can be doors, garage doors, pumps, wireless control devices in vehicles, locking of drive shafts, etc, with embodiments of the invention that can be varied within the framework of the attached patent claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0303060-8 | Nov 2003 | SE | national |
