Control device of an electromagnetic actuator for a restraint means

Abstract

A control device of an electromagnetic actuator for a restraint device, including an evaluation and control unit which generates a control signal which predefines a control sequence having control time periods, in which the actuator is activated, and pause time periods, in which the actuator is deactivated. A protective circuit including a counter is provided, the counter monitoring the control sequence and increments its counter content during the at least one control time period and decrements its counter content during the at least one pause time period, the protective circuit effectuating a deactivation of the actuator when the counter content reaches or exceeds a predefined first threshold value, and allows a reactivation of the actuator when the counter content reaches or falls below a predefined second threshold value after reaching or exceeding the first threshold value, the first counter content being greater than the second counter content.

Claims

1. A control device of an electromagnetic actuator for a restraint device, the control device comprising: an evaluation and control unit which is designed to generate at least one control signal as a function of a triggering decision which was reached, the control signal determining a chronological sequence of the control of the actuator and predefines a control sequence having at least one control time period in which the actuator is activated, and at least one pause time period in which the actuator is deactivated; and a protective circuit including a counter, the counter configured to monitor the control sequence, to increment its counter content by a first count value during the at least one control time period, and to decrement its counter content by a second count value during the at least one pause time period, the protective circuit designed to effectuate a deactivation of the actuator when the counter content reaches or exceeds a predefined first threshold value, and allow a reactivation of the actuator when the counter content reaches or falls below a predefined second threshold value after reaching or exceeding the first threshold value, the first threshold value being greater than the second threshold value.

2. The control device as recited in claim 1, wherein the at least one control time period corresponds to a pulse duration or a dwell time duration.

3. The control device as recited in claim 2, wherein the evaluation and control unit is designed to generate, with the aid of a first control signal, a pulse-shaped actuator current, which activates the actuator.

4. The control device as recited in claim 3, wherein the evaluation and control unit is designed to generates, with the aid of a second control signal, a constant actuator current having a predefined value when the pulse-shaped actuator current reaches a predefined first threshold value, the constant actuator current holding the actuator in the activated state.

5. The control device as recited in claim 4, wherein the evaluation and control unit is designed to deactivate the actuator with the aid of a third control signal.

6. The control device as recited in claim 1, wherein the electro-magnetic actuator is a solenoid valve, via which a restraint device, which is an airbag, is fillable with a cold gas, a number of the control time periods and the pause time periods within a predefined time period being predefinable as a function of the desirable filling capacity of the airbag per unit of time.

7. A control device of an electromagnetic actuator for a restraint device, the control device comprising: an evaluation and control unit which is designed to generate at least one control signal as a function of a triggering decision which was reached, the control signal determining a chronological sequence of the control of the actuator and predefines a control sequence having at least one control time period in which the actuator is activated, and at least one pause time period in which the actuator is deactivated; and a protective circuit including a counter which monitors the control sequence and increments its counter content during the at least one control time period and decrements its counter content during the at least one pause time period, the protective circuit designed to effectuate a deactivation of the actuator when the counter content reaches or exceeds a predefined first threshold value, and allow a reactivation of the actuator when the counter content reaches or falls below a predefined second threshold value after reaching or exceeding the first threshold value, the first threshold value being greater than the second threshold value; wherein the at least one control time period corresponds to a pulse duration or a dwell time duration, and wherein the counter increments the counter content during the pulse duration by a predefined first counting stage and, during the dwell time duration, by a predefined second counting stage which is smaller than the first counting stage.

8. The control device as recited in claim 7, wherein the first counting stage is dependent on the predefined first threshold value of the pulse-shaped actuator current, and the second counting stage is dependent on the predefined value of the constant actuator current.

9. The control device as recited in claim 8, wherein the counter decrements the counter content during the pause duration by a third counting stage.

10. The control device as recited in claim 9, wherein the third counting stage is dependent on at least one of: i) a thermal resistance of the control device, and ii) an instantaneous temperature of the control device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic block diagram of one exemplary embodiment of a control device of an electro-magnetic actuator for a restraint device according to the present invention.

(2) FIG. 2 shows the curve of an actuator current generated with the aid of the control device according to the present invention, according to FIG. 1.

(3) FIG. 3 shows the curve of the counter content of a counter for the control device according to the present invention, according to FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(4) As is apparent from FIGS. 1 through 3, the represented exemplary embodiment of a control device 1 according to the present invention of an electromagnetic actuator 9 for a restraint device, which is not represented in greater detail, includes an evaluation and control unit 5 which generates at least one control signal S.sub.R1, S.sub.R2, S.sub.Off as a function of a triggering decision which was reached, the control signal determining the chronological sequence of the control of actuator 9 and predefines a control sequence having at least one control time period t.sub.1, t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4, in which actuator 9 is activated, and at least one pause time period t.sub.P1, t.sub.P2, t.sub.P3, t.sub.P4, in which actuator 9 is deactivated. According to the present invention, a protective circuit 10 including a counter 7 is provided, the counter monitoring the control sequence and increments its counter content Z during the at least one control time period t.sub.1, t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4 and decrements its counter content during the at least one pause time period t.sub.P1, t.sub.P2, t.sub.P3, t.sub.P4. In this case, protective circuit 10 effectuates a deactivation of actuator 9 when counter content Z reaches or exceeds a predefined first threshold value ZS1, and allows a reactivation of actuator 9 when counter content Z reaches or falls below a predefined second threshold value ZS2 after reaching or exceeding first threshold value ZS1, first counter content ZS1 being greater than second counter content ZS2.

(5) As is further apparent from FIGS. 1 through 3, the at least one control time period corresponds to one pulse duration t.sub.1 or one dwell time duration t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4. Evaluation and control unit 5 closes a first switch S1 with the aid of a first control signal S.sub.R1 and generates a pulse-shaped actuator current I.sub.A, via a first resistor R1 in combination with a further resistor R3 and a supply voltage U.sub.B in a first phase, in an output stage 3 which activates electromagnetic actuator 9. Simultaneously, first control signal S.sub.R1 is present at a first input Z1 of counter 7. Due to control signal SR1 present at first input Z1, a first counting stage is set, which counter 7 uses for incrementing counter content Z.

(6) As is further apparent from FIGS. 1 through 3, evaluation and control unit 5 closes a second switch S2 with the aid of a second control signal S.sub.R2 and generates a constant actuator current I.sub.A having a predefined value I.sub.H, via a second resistor R2 in combination with further resistor R3 and supply voltage U.sub.B in a second phase, in output stage 3 when pulse-shaped actuator current I.sub.A has reached a predefined first threshold value I.sub.P. Constant actuator current I.sub.A holds actuator 9 in the activated state. Simultaneously, second control signal S.sub.R2 is present at a second input Z2 of counter 7. Due to control signal S.sub.R2 present at second input Z2, a second counting stage is set, which counter 7 uses for incrementing counter content Z.

(7) As is further apparent from FIGS. 1 through 3, evaluation and control unit 5 opens a third switch S3 with the aid of a third control signal S.sub.Off and deactivates actuator 9 in a third phase. Simultaneously, third control signal S.sub.Off is present at a third input Z3 of counter 7. Due to control signal S.sub.Off present at third input Z3, a third counting stage is set, which counter 7 uses for decrementing counter content Z.

(8) Counter 7 is installed for monitoring the load of the control device. Counter content Z of counter 7 is incremented or decremented by the associated counting stage in a fixed time interval, as a function of the present phase. When a predefined first threshold value ZS1, which represents a switch-off threshold, is reached or exceeded, output stage 3 is then automatically switched off. If counter content Z reaches or falls below second threshold value ZS2, which represents a restart threshold, after output stage 3 and electromagnetic actuator 9 have been switched off, a reactivation of output stage 3 and electromagnetic actuator 9 is again permitted.

(9) As is further apparent from FIGS. 1 through 3, counter 7 increments counter content Z during each of the first phases, each of which corresponds to pulse duration t.sub.1, by a high first counting stage. During each of the second phases, each of which corresponds to a dwell time duration t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4, counter 7 increments counter content Z by a smaller second counting stage. In the exemplary embodiment shown, the ratio of the second counting stage to the first counting stage corresponds to the ratio of constant holding current I.sub.H to amplitude I.sub.P of the pulsed activation current. Therefore, the first counting stage has a value, for example, of 20, and the second counting stage then has a value of 2 when holding current I.sub.H has a value of approximately 10% of amplitude I.sub.P of the pulsed activation current. The third counting stage for decrementing counter content Z is selected in accordance with the possible thermal cooling. In the exemplary embodiment shown, the third counting stage is selected as a function of the thermal resistance of control device 1. According to one possible optimization, the value for the third counting stage for decrementing counter content Z per unit of time is varied as a function of the instantaneous temperature in the control device. Evaluation and control unit 5 outputs the sequence of control signals S.sub.R1, S.sub.R2, S.sub.Off for generating a desirable control sequence having at least one control time period t.sub.1, t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4, in which actuator 9 is activated, and at least one pause time period t.sub.P1, t.sub.P2, t.sub.P3, t.sub.P4 in the exemplary embodiment shown, in response to an external control signal S.sub.ext.

(10) As is further apparent from FIGS. 1 through 3, output stage 3 and, therefore, electromagnetic actuator 9, are switched off when counter content Z reaches or exceeds first threshold value ZS1 acting as the switch-off threshold. In this case, the counter may output, due to an internal comparison, a corresponding switch-off signal to evaluation and control unit 5 which generates and outputs third control signal S.sub.Off in response to the received switch-off signal. If counter content Z reaches or falls below predefined second threshold value ZS2 acting as a restart threshold, an activation of output stage 3 and of electromagnetic actuator 9 is again permitted. In this case, the counter may output, due to an internal comparison, a corresponding restart signal to evaluation and control unit 5 which terminates the output of third control signal S.sub.Off in response to the received restart signal. Alternatively, the counter may only output counter content Z to evaluation and control unit 5. Evaluation and control unit 5 then carries out the corresponding comparisons with threshold values ZS1, ZS2.

(11) In the exemplary embodiment shown, evaluation and control unit 5 generates different actuator currents I.sub.A via switches S1, S2 and deactivates actuator 9 via third switch S3. This advantageously allows for a simple and cost-effective implementation of control device 1, according to the present invention, of an electromagnetic actuator 9 for a restraint means. Of course, those skilled in the art may implement suitable technical approaches other than switches S1, S2, S3 for generating different actuator currents I.sub.A; for example, different current sources may also be used for generating different actuator currents I.sub.A.

(12) Specific embodiments of control device 1 according to the present invention may be used, for example, for controlling an electromagnetic actuator 9 designed as a solenoid valve, via which a restraint means designed as an airbag may be filled with a cold gas. The number of the control time periods t.sub.1, t.sub.H1, t.sub.H2, t.sub.H3, t.sub.H4 and the pause time periods t.sub.P1, t.sub.P2, t.sub.P3, t.sub.P4 within a predefined period of, for example, 50 ms, may then be predefined as a function of the desirable filling capacity of the airbag per unit of time.