METHOD AND DEVICE FOR CONTROLLING TILTING ANGLES OF MOTOR-DRIVEN REARVIEW MIRRORS OF AUTOMOBILE

Abstract: Method and device for controlling tilting angles of motor-driven rearview mirrors (1) of an automobile are disclosed. The control method and device let the rearview mirrors (1) be more reliably regulated regardless of noise and precisely control the tilting angles of the rearview mirrors (1) within a given tilting range, thus to provide convenience in use of the rearview mirrors (1) and to secure a high level of reliability in mirror tilting operation and to provide good rearview angles for a driver. The control device incluces digital detecting means (3) and senses the angles of the rearview mirrors (1) through a digital sensing process, thus to provide a stable circuit scarcely deteriorated by noise.

Description: METHOD AND DEVICE FOR CONTROLLING TILTING ANGLES OF MOTOR-DRIVEN REARVIEW MIRRORS OF AUTOMOBILE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates in general to method and device for controlling the tilting angles of motor-driven rearview mirrors of an automobile and, more particularly, to an improvement in such tilting angle control method and control device for letting the rearview mirrors be more reliably tilted regardless of noise and for more precisely controlling the tilting angles of the rearview mirrors within a given tilting range. Description of the Prior Art In prior art, there have been proposed and used several types of devices for controlling the tilting angles of automobile rearview mirrors as disclosed in Korean Patent Laid-open Publication No. 93-8565. Japanese U.M. Laid-open Publication Nos. Sho. 60-130155 and 60-134037 disclose devices for detecting and controlling, using positional sensors, the tilting angles of automobile rearview mirrors respectively. Japanese Patent Publication No. Heisei. 3-32496 discloses a device for detecting and controlling, using a piezo-electric element, the tilting angles of automobile rearview mirrors. Furthermore, U.S. Patent No. 4,915,493 and Japanese U.M. Laid-open Publication No. 63-101248 disclose devices for detecting and controlling, using potentiometers, the tilting angles of automobile rearview mirrors respectively. In each of the above tilting angle control devices, an electronic controller installed in an automobile detects, using a typical positional sensor, a positional displacement of a rearview mirror in accordance with mirror tilting operation and controls a mirror drive motor so as to let the rearview mirror be tilted at a desired tilting angle set by a driver. However, neither of the above tilting angle control devices is designed, considering the effect of a noise infiltrating into a signal transmission line of the device. Therefore, the above devices have a problem that they can not achieve good operational reliability in control of the tilting angles of automobile rearview mirrors. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide method and device for controlling tilting angles of motor-driven rearview mirrors of an automobile in which the above problem can be overcome and which let the rearview mirrors be more reliably regulated regardless of noise and precisely control the tilting angles of the rearview mirrors within a given tilting range, thus to provide convenience in use of the rearview mirrors and to secure a high level of reliability in mirror tilting operation and to provide good rearview angles for a driver. In an aspect, the present invention provides a method for controlling tilting angles of motor-driven rearview mirrors of an automobile comprising the steps of: checking an input key signal in order for determining whether the key signal is a combined key signal of a plurality of key switches of a key pad, and letting the angles of the rearview mirrors be controlled by a key operation of a driver when the key signal is not the combined key signal; when the key signal is the combined key signal, checking whether a memory input signal or a memory output signal has been inputted, and orderly storing top, bottom, left and right angles of the rearview mirrors in a memory unit when the memory input signal has been inputted, the top, bottom, left and right angles of the rearview mirrors being detected by digital detecting means; and when the memory output signal has been inputted, reading positional data out of the memory unit, comparing the positional data with current angles of the rearview mirrors, and outputting motor drive control signals until the positional data and the current angles of the rearview mirrors are of even values, thus to automatically control the rearview angles. In another aspect, the present invention provides a device for controlling tilting angles of motor-driven rearview mirrors of an automobile comprising: digital detecting means connected to a mirror panel by means of a two joint link and outputting a predetermined resistance value in accordance with positional displacement of the mirror panel; a pulse generator connected to the digital detecting means and converting the resistance value of the detecting means into pulses having a frequency corresponding to the resistance value; a processor counting the pulses of the pulse generator and calculating how much pulses have been inputted from the pulse generator within a predetermined time, comparing the current angle represented by the pulses with positional data read out of a memory unit, and outputting a digital control signal; the memory unit electrically connected to the processor and storing therein rearview angle data relative to conditions, such as driver's figure, entry into an express highway and parking of automobile, sensed by the digital detecting means; a motor drive circuit converting the digital control signal of the processor into an electric signal; a mirror drive motor tilting the mirror panel upward, downward, leftward and rightward in accordance with the electric signal of the motor drive circuit; and a key pad electrically connected to an input port of the processor and provided with a plurality of key switches, whereby the tilting angle of the mirror panel is automatically controlled by key operation of the key pad. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of a foldable, motor- driven rearview mirror assembly equipped with a mirror tilting angle control device of the invention, showing a construction of the mirror assembly; Fig. 2 is a block diagram showing a construction of a mirror tilting angle control device in accordance with an embodiment of the invention; Figs. 3 and 4 are sectional views of the rearview mirror assembly, showing mirror panel tilting operations carried out by the tilting angle control device of the invention; Fig. 5 is a schematic view of digital detecting means of the variable resistor type of the tilting angle control device of the invention, showing a tilting angle detecting operation of the digital detecting means in response to positional displacement of the mirror panel; Fig. 6 is a block diagram showing pulse generation of a pulse generator in accordance with resistance variation of the variable resistors of the digital detecting means of the invention; Fig. 7 is a block diagram comparatively showing noise effect between a typical analog type control device and a digital type control device of the invention; Fig. 8 is a block diagram of the tilting angle control device of the invention; Fig. 9 is a flowchart of a main routine for controlling the tilting angles of rearview mirrors by the control device of the invention; Fig. 10 is a flowchart of a subroutine for controlling the tilting angles of rearview mirrors using preset data stored in a memory unit of the control device of the invention; Fig. 11 is a circuit diagram showing a relation between a processor, a memory unit and a back up circuit of the tilting angle control device of the invention; and Fig. 12 is a circuit diagram showing a relation between the processor, the pulse controller, a motor drive circuit and key pad of the tilting angle control device of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a perspective view of a foldable, motor- driven rearview mirror assembly equipped with a mirror tilting angle control device of the invention. Fig. 2 is a block diagram showing a construction of a mirror tilting angle control device in accordance with an embodiment of the invention. Figs. 3 and 4 are sectional views of the rearview mirror assembly, showing mirror panel tilting operations carried out by the tilting angle control device, and Fig. 5 is a schematic view of digital detecting means of the variable resistor type of the tilting angle control device of the invention, showing a tilting angle detecting operation of the digital detecting means in response to positional displacement of the mirror panel. As shown in Fig. 1, the rearview mirror assembly includes a mirror panel 1 mounted on a mirror housing and a memory actuator 2 received in the mirror housing. As shown in Figs. 2 and 5, the tilting angle control device of the invention includes the digital detecting means 3, which means 3 includes four positional sensors comprising variable resistors and is adapted for outputting a predetermined resistance value in accordance with positional displacement of the mirror panel 1. The digital detecting means 3 is placed in the inside or the outside of a motor-driven mirror control case and electrically connected to the mirror panel 1 through a two joint link 4. The digital detecting means 3 is electrically connected to a pulse generator 5, which generator 5 converts the resistance value of the detecting means 3 into pulses having a frequency corresponding to the resistance value. The pulse generator 5 is electrically connected to an input port of a processor 6. The processor 6 counts the pulses of the pulse generator 5 and calculates how much pulses have been inputted thereto from the pulse generator 5 within a predetermined time, thus to determine a current angle of the mirror panel 1. The processor 6 also compares the current angle, represented by the pulses outputted from the pulse generator 5, with positional data read out of a memory unit 7 and outputs a control signal to a motor drive circuit 9. The memory unit 7 is electrically connected to the processor 6 and stores therein rearview angle data relative to conditions, such as driver's figure, entry into an express highway and parking of automobile, sensed by the digital detecting means 3. The motor drive circuit 9 is electrically connected to an output port of the processor 6 and applied with the control signal of the processor 6 and converts that control signal into an electric signal for driving a mirror drive motor 8. The mirror drive motor 8 is applied with the electric signal from the motor drive circuit 9 and tilts the mirror panel 1 upward, downward, leftward or rightward. The tilting angle control device of the invention also includes a key pad 10, which key pad 10 is electrically connected to an input port of the processor 6 and provided with a plurality of key switches S χ - S 7 sh shown in Fig. 12. The memory unit 7 includes a RAM as well as a ROM and is provided with a memory back up circuit (MBC) for prevention of possible loss of data of the RAM of the memory unit 7. In operation of the above tilting angle control device, the seven key switches S x - S 7 of the key pad 10 are operated so that a combined signal of the key switches S 1 - S 7 is outputted to the processor 6. The processor 6 is applied with the combined signal at a port 1 as shown in Fig. 8. The first to fourth key switches S 1 - S 4 are direction control key switches for directly tilting the mirror panel 1 upward, downward, leftward and rightward respectively. The above key switches S 1 - S 4 are also used as associated user key switches. Upon reception of the combined key signal of the key switches S 1 - S. of the key pad 10, the processor 6 operates the signal and controls the tilting angle of the mirror panel 1 in response to the combined key signal. At this time, the mirror panel tilting operation mode of the processor 6 is generally classified into two modes. That is, the processor 6 may control the mirror panel 1 through a basic operation mode. In the basic operation mode, the processor 6 lets the tilting angle of the mirror panel 1 be directly controlled in the same manner as a typical operation mode for controlling a typical motor- driven rearview mirror. The processor 6 also may control the mirror panel 1 through a memory-related operation mode. In the memory-related operation mode, the processor 6 automatically controls the tilting angle of the mirror panel 1 in accordance with data stored in the memory unit 7. 1. Basic mode: When the processor 6 is applied with the combined signal of the direction control key switches S l - S 4 of the key pad 10, which switches S : - S 4 are operated in the same manner as a typical operation mode for controlling a typical motor-driven rearview mirror, the processor 6 primarily recognizes left and right rearview mirrors without relation to the memory unit 7 and directly outputs a control signal to the motor drive circuit 9 in order for driving the four motors, related to the left and right rearview mirrors, in forward direction and in reverse direction, and directly tilts the rearview mirrors at tilting angles set by a user. 2. Memory-related mode: In order to store data in the memory unit 7, a combined key signal is applied to the processor 6 by operating a memory input key switch S 5 and an associated user key switch or one of the direction control key switches S χ - S 4 of the key pad 10. Upon reception of the combined key signal, the processor 6 directly interrupts input of the signal from the key pad 10 but measures current top, bottom, left and right angles (regulated rearview tilting angles) of the left and right reaRview mirrors and stores the measured tilting angles. At this time, the angles of the rearview mirrors are measured by the digital detecting means 3 including the four positional sensors comprising variable resistors placed in the inside or the outside of the motor-driven mirror control case. The digital detecting means 3 outputs a predetermined resistance value at a predetermined angle due to folding motion of the two joint link 4 connecting the digital detecting means 3 to the mirror panel 1, which folding motion of the link 4 is caused by tilting motion of the mirror panel 1. The resistance value of the digital detecting means 3 is applied to the pulse generator 5, which generator 5 converts the resistance value into pulses having a frequency corresponding to the resistance value and outputs the pulses to the processor 6. A pulse counter of the processor 6 counts the pulses outputted from the pulse generator 5 and calculates how much pulses have been continuously inputted to the processor 6 from the pulse generator 5 within a predetermined time, thus to calculate the time for input of a predetermined number of pulses as shown in Fig. 6. The processor 6 in turn stores the calculated data or the digital data of the detected tilting angles in associated sections of the memory unit 7. At this time, the digital data of the measured tilting angles are stored in the memory unit 7 in order of data of top and bottom tilting angles of the left mirror, data of left and right tilting angles of the left mirror, data of top and bottom tilting angles of the right mirror and data of left and right tilting angles of the right mirror. Otherwise stated, the memory unit 7 stores preset rearview angle data corresponding to varieties of conditions, such as driver's figure, entry into an express highway and parking of automobile. On the other hand, in order for tilting the rearview mirrors using the data of the memory unit 7 and thereby securing rearview angles agreeable to specified conditions, the driver operates a memory output key switch S 6 and an associated user key switch (one of the direction control key switches S χ - S 4 ) of the key pad 10. In this case, the processor 6 reads rearview angle data (positional data) out of the memory unit 7 in the other way of the case of operating the memory output key switch S 5 . Upon reading the rearview angle data, the arithmetic unit of the processor 6 compares the positional data read out of the memory unit 7 with the current mirror angle and repeatedly outputs control signals until the current mirror angle and the positional data are of even value. The control signals of the processor 6 are applied to the motor drive circuit 9, which circuit 9 converts the control signals into electric signals for rotating the mirror drive motors 8. The electric signals of the drive circuit 9 are applied to the motors 8 connected to the mirror panels 1 so that the motors 8 tilt the mirror panels 1 in order for securing desired rearview angles in accordance with conditions. Turning to Figs. 9 and 10, there are shown a flowchart of a main routine for controlling the tilting angles of the rearview mirrors and a flowchart of a subroutine for controlling the tilting angles of the rearview mirrors using preset data stored in the memory unit 7. As shown in the drawings, when the processor 6 is applied with a key signal of the key pad 10, the processor 6 checks the input key signal in order for determining whether the key signal is a combined key signal of the key switches S 1 - S 7 of the key pad 10. When the key signal is not the combined key signal, the processor 6 lets the angles of the rearview mirrors be controlled by the key operation of the driver. When the key signal is the combined key signal, the processor 6 checks whether a memory input signal or a memory output signal has been inputted. When the memory input signal has been inputted, the processor 6 orderly stores top, bottom, left and right angles of the rearview mirrors in the memory unit 7, which top, bottom, left and right angles of the rearview mirrors are detected by the digital detecting means 3. However, when the memory output signal has been inputted, the processor 6 reads positional data out of the memory unit 7 and compares the positional data with current angles of the rearview mirrors, and outputs control signals to the motor drive circuit 9 until the positional data and the current angles of the rearview mirrors are of even values, thus to automatically control the rearview angles. Referring to Figs. 8 and 11, the RAM of the memory unit 7 of the control device is provided with the back up circuit MBC so that the RAM can be supplied with minimum electric power, necessary for keeping the stored data of the RAM, from the back up circuit when the main power is shut off. Therefore, the RAM of the memory unit 7 is free from data loss even when the main power is shut off. That is, the RAM of the memory unit 7 is connected to both the main power source Vcc and the back up battery BAT through two switching diodes D 1 and D. respectively such that the RAM can be supplied with the electric power from either the main power source Vcc or the back up battery BAT. When the RAM is supplied with the power from the main power source Vcc, the back up battery BAT is shut off so that the power of the battery BAT can be saved. On the contrary, when the main power source Vcc is shut off, the RAM is supplied with the minimum power, necessary for prevention of data loss, from the back up battery BAT so that the RAM is free from data loss even when the main power source Vcc is shut off. When the RAM is supplied with minimum power from the back up battery BAT, the CE terminal signal of the RAM is a high signal due to switching action of an additional transistor Q l f so that the data stored in the RAM is prevented from being deformed due to back up noise. As described above, the control device of the invention senses the position of the mirror through a digital sensing process other than the typical analog sensing process, thereby providing a stable circuit scarcely deteriorated by noise. As shown in Fig. 7, the noise generally infiltrates into the signal transmission line of the signal transmission section between the signal output part of the mirror and the signal input part of the controller. In the typical analog type control device, no A/D converter is installed in the signal output part so that the signal in the signal transmission section is an analog signal (voltage). However, in the digital type control device using the variable resistor positional sensors of the invention, the pulse generator has a simple construction and is readily installed in the signal output part. Therefore, the digital type control device of the invention applies the digital pulse signal to the controller. When a noise infiltrates into the signal transmission section of the analog type control device, the noise-laden signal is applied to the A/D converter so that the controller is applied with a value deformed by the noise- laden signal. Since a typical 8-bit A/D converter has a noise reserve of about 0.02 V so that the noise may be a deathblow to that A/D converter. In order to solve this problem, the typical analog type control device should be provided with a buffer and a filter in the signal output part and in the signal input part respectively. The digital type control device transmits pulses having a predetermined frequency differently from the analog type control device so that the pulse counting number of the digital type control device changes when a noise infiltrates into the signal transmission section. Since the digital type control device has a noise reserve of at least 1 V and infiltration of the high frequency noise into the digital type control device is prevented due to limit of input frequency of the counter, the counting number deformed by the noise is reduced. In addition, the digital type control device has a reserve counting value for angle resolving power larger than that of the analog type control device as represented in the Table. Therefore, the digital type control device of the invention has a noise reserve wider than that of the analog type control device. Table type resolving power (angle) signal reserve analog 0.04 about 0.02 V digital 0.04 about 40 pulses In addition, the variable resistance of the digital detecting means 3 is in inverse proportion to the frequency. The characteristic of the above inverse proportion between the variable resistance and the frequency draws a curve in a graph. However, the radius of curvature of the curve may be negligible so that the characteristic of the above inverse proportion between the variable resistance and the frequency is represented by a straight line in the following graph. In the tilting angle control device of the invention, the variable resistance of y-axis and the frequency of x- axis of the following graph may be free changed. fr capacity of variable resistor (kΩ) In the present invention, the positional sensors of the digital detecting means 3 may use four variable condensers instead of the variable resistors, each of which variable condensers outputs electrostatic capacity in accordance with positional displacement of the mirror panel 1. As described above, the rearview mirror tilting angle control device of the present invention is provided with digital detecting means 3 and senses the angles of the rearview mirrors through a digital sensing process. Therefore, the present invention provides a stable circuit scarcely deteriorated by noise. Furthermore, the control device stores, in a memory unit of an electronic control unit installed in an automobile, rearview angle data relative to conditions, such as driver's figure, entry into an express highway and parking of automobile, so that the control device of the invention readily and rapidly provides an appropriate rearview angle for a driver. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims: WHAT IS CLAIMED IS: 1. A method for controlling tilting angles of motor- driven rearview mirrors of an automobile comprising the steps of: checking an input key signal in order for determining whether the key signal is a combined key signal of a plurality of key switches of a key pad, and letting the angles of the rearview mirrors be controlled by a key operation of a driver when the key signal is not the combined key signal; when the key signal is the combined key signal, checking whether a memory input signal or a memory output signal has been inputted, and orderly storing top, bottom, left and right angles of the rearview mirrors in a memory unit when the memory input signal has been inputted, said top, bottom, left and right angles of the rearview mirrors being detected by digital detecting means; and when the memory output signal has been inputted, reading positional data out of the memory unit, comparing the positional data with current angles of the rearview mirrors, and outputting motor drive control signals until the positional data and the current angles of the rearview mirrors are of even values, thus to automatically control the rearview angles. 2. The method according to claim 1, wherein said digital detecting means is connected to mirror panels and senses the current angles of the rearview mirrors through a digital sensing process, thus to have a wider noise reserve. 3. A device for controlling tilting angles of motor- driven rearview mirrors of an automobile comprising: digital detecting means connected to a mirror panel by means of a two joint link and outputting a predetermined resistance value in accordance with positional displacement of the mirror panel; a pulse generator connected to said digital detecting means and converting the resistance value of the detecting means into pulses having a frequency corresponding to the resistance value; a processor counting the pulses of the pulse generator and calculating how much pulses have been inputted from the pulse generator within a predetermined time, comparing the current angle represented by the pulses with positional data read out of a memory unit, and outputting a digital control signal; the memory unit electrically connected to the processor and storing therein rearview angle data relative to conditions, such as driver's figure, entry into an express highway and parking of automobile, sensed by the digital detecting means; a motor drive circuit converting the digital control signal of the processor into an electric signal; a mirror drive motor tilting the mirror panel upward, downward, leftward and rightward in accordance with the electric signal of the motor drive circuit; and a key pad electrically connected to an input port of the processor and provided with a plurality of key switches, whereby the tilting angle of the mirror panel is automatically controlled by key operation of the key pad. 4. The device according to claim 3, wherein a RAM of the memory unit is provided with a back up circuit, said back up circuit comprising a back up battery and a pair of switching diodes and adapted for supplying minimum electric power, necessary for keeping the stored data of the RAM, when a main power is shut off. 5. The device according to claim 3, wherein said digital detecting means comprises four variable resistor positional sensors outputting a predetermined resistance value in accordance with positional displacement of the mirror panel. 6. The device according to claim 3, wherein said digital detecting means comprises four variable condenser positional sensors outputting a predetermined electrostatic value in accordance with positional displacement of the mirror panel.

Inventors: CHOI KUN HO, LEE GUN HWAN, PARK KI HON, CHOI, KUN, HO, LEE, GUN, HWAN, PARK, KI, HON
Applicants: CHOI KUN HO, LEE GUN HWAN, PARK KI HON, POONG JEONG IND CO LTD, CHOI, KUN, HO, LEE, GUN, HWAN, PARK, KI, HON, POONG JEONG IND. CO., LTD.
Application year: 1995
Main classification: B60R1
IPC codes: B60R1, G05B19