DE102005047013B4 - giver - Google Patents

Abstract

Encoder (1) for detecting rotational positions of rotatable or pivotable parts or paths in motor vehicles, eg. B. accelerator pedals or throttle valves, comprising at least one pair of sensors (11a, 11b) with mutually inversely extending characteristics and one of the sensors (11a, 11b) associated terminal (19a, 19b) for tapping a sensor signal, characterized in that
the transmitter (1) has at least one control means (12a, 12b) associated with the sensors (11a, 11b), at least one control means (12a, 12b) being suitable and arranged, in the event of a short circuit between the terminals (19a, 19b) for picking up the sensor signals to apply these terminals (19a, 19b) either with the respective larger sensor signal or with the respective smaller sensor signal.

Description

STATE OF THE ART

The invention relates to an encoder for detecting rotational positions of rotatable or pivotable parts or paths in motor vehicles, for example accelerator pedals or throttle valves, comprising at least a few sensors with mutually inversely extending characteristics and each one of the sensors associated terminal for tapping an analog sensor signal.

Known from the state of the art rotary encoders of the type mentioned in the Robert Bosch AG are known. These encoders have as sensors two potentiometers, which have mechanically coupled grinder taps, and which are supplied with reversed polarity reversal with electric current. Due to the reversed polarity, the characteristic curves of the two potentiometers d. H. the ohmic resistances of the potentiometers depending on the wiper position inverse to each other. While one potentiometer has a rising straight line as a characteristic curve, the other potentiometer has a straight line with the magnitude of the same slope as a characteristic curve. At a resistance of 50% of the maximum resistance, the two characteristics intersect. The advantage of such a rotary encoder with two sensors with inversely running characteristics is on the one hand the redundancy, on the other hand the possible fault detection of defects of the sensors or interruptions in the lines leading from the rotary encoder to an encoder signal processing means for the analog sensor signals. A particular advantage of the mutually inverse curves in contrast to other known ways of constructing a redundant encoder is that the resolution of the sensor signal, which is provided at the terminals for tapping an analog sensor signal is the same size for both sensors. However, the rotary encoder designed in this way has the disadvantage that the fault detection in the case of a short circuit between the sensor signals or the lines or terminals for the two sensor signals fails. In this case, regardless of the angular position whose magnitude is to be detected on both sensor lines, always a sensor signal of 50% of the maximum signal level of the sensor signal is provided. The means processing the sensor signals, which checks for error detection, whether the sum of the two sensor signals always give 100% of the maximum signal level of a sensor signal will always detect a fault-free state in this case, although in fact there is a short circuit between the two sensor signals. Because of this hitherto faulty error control in the case of short circuit between the sensor signal lines or connections, these encoders are not suitable for accelerator pedals or other safety-critical areas. So far, the rotary encoders could only be used, for example, for throttle valves which, on the one hand, are not safety-critical and, on the other hand, can be checked for fault-free function by additional plausibility checks.

From the DE 40 04 085A1 a device for electronic control of an internal combustion engine of a motor vehicle is known, which comprises a detection element with two sensors, wherein the signals of the sensors change in opposite directions.

From the DE 196 42 174 A1 is known circuit arrangement for detecting the position of a movable element in a motor vehicle with two sensors, wherein a function check of the sensors is performed based on the guided on the signal lines sensor signals.

Against the background of the disadvantages of the prior art, the invention has the object, a transmitter of the type mentioned in such a way that even a fault detection in the event of a short circuit between the signal lines or sensor signal terminals is possible.

ADVANTAGES OF THE INVENTION

This object is achieved in that the encoder has at least one control means which is associated with the sensors, wherein the at least one control means is suitable and arranged, in the case of a short circuit between the terminals for tapping the sensor signals, the terminals for tapping the sensor signals either with to apply the respective larger sensor signal or with the respective smaller sensor signal. In the case of a short circuit between the terminals for tapping the sensor signals is at both terminals for tapping the sensor signals the same potential or in other words the same sensor signal. The at least one control means now ensures that the sensor signal applied in the short circuit to both terminals for picking up the sensor signals corresponds either to the sensor signal provided by one sensor or by the other sensor in the error-free case of the sensor. It is either the respective larger sensor signal or the smaller sensor signal depending on how the at least one control means is set up.

Preferably, the encoder has two control means, which are each assigned to one of the sensors. In case of short circuit this behaves Control means of the sensor dominant whose sensor signal is to be tapped at the output. These are either the sensor with the larger sensor signal or the sensor with the smaller sensor signal at the respective position of the movable or pivotable part. The control means of the sensor whose sensor signal can not be tapped off at the terminals is referred to as a recessive behavioral control means.

The control means may be part of the sensors in one embodiment of the sensor or at least partially integrated into the sensors.

The control means may each comprise either a high-side driver or a low-side driver which may be formed, for example, from a combination of a transistor and a pull-up or pull-down resistor assigned to the transistor. At the base of the transistors is preferably applied to the signal generated by a detection means of the sensor, which drives the transistor for generating the sensor signal. The collector is preferably connected to the rest of the control means, whereby a feedback of the sensor signal generated by the transistor to the rest of the control means is possible.

The encoder according to the invention can be combined with a device for processing the sensor signals to an inventive arrangement. The device for processing the sensor signals may, for example, be a control device.

In such an arrangement, the transmitter and the device can be connected to one another via at least two transmission channels for transmitting the sensor signals of the two sensors. The device is preferably set up and suitable for letting the sensor signals in the device drop to a first reference potential via a respective pull-down resistor or pull-up resistor.

The device may also be suitable and configured to compare the sum of the sensor signals with a voltage between the first reference potential and a second reference potential or with a maximum possible signal level of the sensor signals.

DRAWING

An embodiment of an inventive arrangement of a rotary encoder according to the invention and a control device for processing of the encoder provided sensor signals is described in detail with reference to the single figure.

DESCRIPTION OF THE EMBODIMENT

The encoder shown in the figure 1 is redundant and has two detection elements 11a . 11b preferably non-contact detecting the position of a rotatable first part, for example, an accelerator pedal to a fixed second part. The detection means 11a . 11b preferably have mutually inverse characteristics. So can the characteristic of the detection means 11a be configured so that in the one end position of the accelerator pedal, an electrical signal of the size 0 is generated, while in the second end position, a signal is output, which has a maximum signal level. Between the end positions becomes a proportional to the position of the accelerator pedal level between the signal level 0 and the maximum signal level.

The characteristic of the other detection means 11b goes to the characteristic of the detection means 11a vice versa. Ie. in the first position of the accelerator pedal, the sensor generates 11b a signal with a maximum level and in the second end position a signal with a level 0 , Between the two end positions, the signal level decreases inversely proportional to the position of the accelerator pedal.

The characteristic curve of the detection means 11a and the second detection means 11b however, it does not necessarily have to be linear. For an inverse characteristic curve of the two characteristic curves, it is sufficient if the sum of the signal levels at each time point yields a value of 100% of the maximum signal level.

That of the detection means 11a . 11b signal generated is a first control means 12a or a second control means 12b made available. This rule means 12a . 12b give the signal over a connection, possibly under interim processing 13a respectively 13b to a respective PNP transistor 14a . 14b , The wires 13a . 13b are linked to the base of the PNP transistor.

To the emitter of these transistors 14a . 14b a positive reference potential V _{ref + is} applied across one terminal 15 the encoder 1 is supplied.

The collector of transistors 14a . 14b is each with a connection 19a . 19b connected to the encoder. The collector is additionally via a line 18a respectively 18b with the respective control means 12a . 12b connected. About the line 18a . 18b will that be at the connections 16a respectively 16b applied potential to the control means 12a . 12b given.

The connection 15 the encoder is over a wire 17 connected to a connector on the encoder 1 the positive reference potential V _{ref +} can be tapped.

The control unit 2 , of which only the necessary for the function of the arrangement of the encoder and the control unit parts are shown in the drawing, has connections 21a . 21b on that with the connections 19a respectively 19b the encoder are connected. A connection 22 is connected to the terminal for picking up the positive reference potential V _{ref + of} the rotary encoder 1 connected. A connection 24 of the controller is connected to the negative reference _potential V _ref- . The connections 21a respectively 21b are each connected by an ohmic resistor 23a respectively 23b with this connection 24 for the negative reference _potential V _ref- connected. So unless the transistors 14a . 14b are driven via their base, is a current flow from the positive reference potential V _{ref +} across the terminal 15 of the encoder, via the emitter collector path of the transistors 14a respectively 14b , the wires 16a respectively 16b , the connections 19a respectively 19b , the connections 21a respectively 21b and the resistors 23a respectively 23b to the connection 24 and thus to the negative reference _potential V _ref- possible. It falls to the ohmic resistances 23a respectively 23b a voltage which is determined by the current through these resistors. The current through these resistors 23a respectively 23b is doing through the transistors 14a . 14b set. Between the collector of the transistors 14a respectively 14b and the negative reference _potential V _ref- dropping voltage corresponds to the voltage across the resistors 23a . 23b ,

The rule means 12a . 12b are now according to the invention set up so that in case of a short circuit between the lines 16a . 16b or the connections 19a . 19b or the connections 21a . 21b always the rule means 12a . 12b dominant, that of the detection means 11a respectively 11b gets the higher signal level available. The other rule means 11a . 11b On the other hand, it behaves recessively. Specifically, this means that passing through the transistor 14a . 14b flowing current due to the short circuit both by the one resistor 23a as well as through the other resistance 23b of the control unit 2 to the reference _potential V _ref- flows. However, since the current is over the two resistors 23a . 23b This results in too low a voltage at the collector of the dominant transistor 14a . 14b , The voltage is the control means over the line 18a . 18b communicated, whereupon the rule means 12a . 12b the transistor via the line 13a . 13b controls so that the current flow through the transistor is increased. The current flow is increased until the control means 12a . 12b over the line 18a . 18b a voltage at the collector of the transistors 14a . 14b detects that corresponds to the voltage of the dominant control means 12a . 12b is set in error-free case.

The recessive control agent 12b behaves the other way around. This recognizes over the line 18a respectively 18b a voltage that is too high for the error-free case. The recessive control agent 12a . 12b is then over the line 13a . 13b the corresponding transistor 14a . 14b so drive that the current flow through the transistor 14a . 14b is completely prevented. A current flow through the transistor 14a respectively 14b that of the recessive rule means 12a . 12b is controlled, is therefore not possible. In the event of a short circuit, the current flow through the resistors is thus 23a . 23b completely determined by the dominant rule means. The dominant control means is depending on the rotational position to be detected, the one control means and that in the range 0% to 50% of the maximum position or the other control means and indeed in the range 50% to 100% of the maximum position.

For error monitoring and in particular for detecting a short circuit between the two sensor signals, the controller has an error detection means 25 on. This is both with the positive reference potential V _{ref +} (terminal 22 ) as well as with the negative reference _potential V _ref- (terminal 24 ) connected. In addition, the error detection means 25 with the potentials at the terminals 21a respectively 21b and thus connected to the sensor signals. The error detection means now sums the two sensor signals and compares the sum with the potential difference to the positive reference potential V _{ref +} and the negative reference _potential V _ref- , ie the reference _voltage . If the sum of the sensor signals equals the reference voltage, there is no error case. If, on the other hand, the sum in the case of the illustrated arrangement is greater than the reference voltage, there must be a short circuit between the two sensor signals. Only in this case is both the connection 21a as well as at the terminal 21b the same sensor signal, always from the dominant control means 12a . 12b is determined. The short circuit between the two sensor signals can thus be detected by the error detection means 25 be recognized. The control unit can be set up so that the error is communicated to the driver.

Claims (5)

Encoder (1) for detecting rotational positions of rotatable or pivotable parts or paths in motor vehicles, eg. As accelerators or throttle valves, comprising at least one pair of sensors (11 a, 11 b) with each other inversely extending characteristic lines and in each case one of the sensors (11a, 11b) associated terminal (19a, 19b) for tapping a sensor signal, characterized in that the encoder (1) at least one control means (12a, 12b), the sensors (11a, 11b ), wherein at least one control means (12a, 12b) is suitable and arranged, in the case of a short circuit between the terminals (19a, 19b) for tapping the sensor signals these terminals (19a, 19b) either with the respective larger sensor signal or with the each act on smaller sensor signal. Encoder after Claim 1 , characterized in that the rotary encoder (1) has two control means (12a, 12b) which are each associated with a sensor (11a, 11b). Encoder after Claim 2 , characterized in that the sensors (11a, 11b) comprise the control means (12a, 12b). Donor to one of the Claims 1 to 3 , characterized in that the control means (12a, 12b) each comprise either a high-side driver or a low-side driver. Encoder after Claim 4 , characterized in that the high-side driver or the low-side driver essentially by a transistor (14a, 14b) is formed, the base of which is controlled by the control means (12a, 12b) and whose collector with the control means ( 12a, 12b) is connected.

Images