Patent Application
20110264332
1. Field of the Invention
The present invention relates to a headrest position adjustment device and a headrest position adjustment method which adjust a position of a headrest provided on a seat of a vehicle such as an automobile. Particularly, the present invention relates to a headrest position adjustment device and a headrest position adjustment method which can highly precisely adjust a position of a headrest automatically and to an appropriate condition with a simple configuration.
2. Description of Related Art
For example, the followings have been conventionally known as techniques for adjusting a position of a headrest provided on a seat of a vehicle such as an automobile. That is, a headrest drive control device disclosed in Patent Document 1 identified below monitors the capacitance between a pair of sensing electrodes which are embedded in a ceiling portion of the vehicle and in the headrest. The device adjusts the vertical position of the headrest by judging the height position of the head of a person sitting on the seat based on an amount of a change of the capacitance that occurs when performing scanning by driving the headrest in the upward direction from a lower end.
A device for adjusting a headrest disclosed in Patent Document 2 identified below includes two or three capacitor plates which are arranged in the headrest. The device adjusts the headrest to an appropriate height by measuring the value of capacitance between a head and each capacitor plate.
A headrest adjustment device disclosed in Patent Document 3 identified below includes one sensing electrode which is arranged in the headrest and monitors the capacitance between the headrest and a head. The device adjusts the headrest by judging the height position of the head of a person sitting on the seat based on an amount of a change of the capacitance that occurs when performing scanning by moving the headrest in the upward and downward direction.
[Patent Document 1] JPS64-11511A
[Patent Document 2] JP2000-309242A
[Patent Document 3] JPH11-180200A
However, the devices disclosed in Patent Documents 1 to 3 identified above perform scanning by moving the headrest. Because of this, when, for example, the head of a person sitting on the seat gets swung in the frontward and rearward direction, the adjustment position of the headrest in the upward and downward direction might become wrong. There is also a problem that the data processing load to be imposed on a control unit (e.g., an ECU (Electronic Control Unit), etc.) which is in charge of adjusting the position of the headrest becomes heavy.
The devices disclosed in Patent Documents 1 to 3 identified above estimate the position of a head based on a change of outputs from the capacitance sensors provided (based on a change of the values of capacitances corresponding to the non-flatness of the occipital region of the head). However, there is a problem that when the head exists at a position far from the sensors, the output changes become small, making it impossible to clearly sense the non-flatness of the occipital region.
Moreover, the device disclosed in Patent Document 1 identified above needs to have a sensing electrode provided in a ceiling portion of the vehicle. Therefore, there is a problem that the whole system cannot be contained within the headrest and becomes complicated and costly.
The present invention was made in view of such problems, and aims for providing a headrest position adjustment device and a headrest position adjustment method which can highly precisely adjust the position of a headrest automatically and to an appropriate condition with a simple configuration.
A headrest position adjustment device according to the present invention comprises: a headrest which is set behind a head of a person sitting on a seat; a plurality of sensing electrodes which are provided side by side along a height direction of the headrest and which sense capacitance between the head of the person and the headrest; a detecting circuit which detects a height position of the head with respect to the headrest based on values of capacitances sensed by the plurality of sensing electrodes respectively; and position adjusting means which adjusts an upward/downward-direction position of the headrest based on a detection result of the detecting circuit, wherein when a distance between the headrest and the head is within a certain range, the detecting circuit calculates an estimated center position of the head based on the values of capacitances sensed by the plurality of sensing electrodes, and based on a calculated value, detects the height position of the head with respect to the headrest, and when the distance between the headrest and the head is not within the certain range, the detecting circuit detects the height position of the head with respect to the headrest based on a ratio between the values of capacitances sensed by at least the sensing electrode located at an uppermost position and the sensing electrode located at a lowermost position among the plurality of sensing electrodes.
A headrest position adjustment method according to the present invention comprises: sensing capacitance between a head of a person sitting on a seat and a headrest by a plurality of sensing electrodes which are arranged side by side along a height direction of the headrest; when a distance between the headrest and the head is within a certain range, calculating an estimated center position of the head based on values of capacitances sensed by the plurality of sensing electrodes respectively, and based on a calculated value, detecting a height position of the head with respect to the headrest; when the distance between the headrest and the head is not within the certain range, detecting the height position of the head with respect to the headrest based on a ratio between the values of capacitances sensed by at least the sensing electrode located at an uppermost position and the sensing electrode located at a lowermost position among the plurality of sensing electrodes; and adjusting an upward/downward-direction position of the headrest based on the detected height position of the head with respect to the headrest.
As described above, the headrest position adjustment device and the headrest position adjustment method according to the present invention select an appropriate scheme for detecting the height position of the head based on the distance between the headrest and the head. Therefore, the device and method can highly precisely adjust the position of the headrest with respect to the head automatically and to an appropriate condition with a simple configuration. Since the position of the headrest with respect to the head can be adjusted in this way, accidents due to, for example, failure to adjust the position of the headrest, such as cervical spine injury of a vehicle occupant in a car crash or the like, can be prevented.
In the present invention, when the smallest value among the values of capacitances sensed by the plurality of sensing electrodes is equal to or greater than a threshold, the detecting circuit may judge that the distance between the headrest and the head is within the certain range, and when the smallest value is smaller than the threshold, the detecting circuit may judge that the distance between the headrest and the head is not within the certain range.
The detecting circuit may calculate an estimated center position of the head based on the values of capacitances sensed by the plurality of sensing electrodes and based on a calculated value, may detect the height position of the head with respect to the headrest, while at the same time detecting the height position of the head with respect to the headrest based on a ratio between the values of capacitances sensed by at least the sensing electrode located at an uppermost position and the sensing electrode located at a lowermost position among the plurality of sensing electrodes. When both detected values are equal or an error between the detected values is within a predetermined range, the detecting circuit may judge that the distance between the headrest and the head is within the certain range. When the error between the detected values is greater than the predetermined range, the detecting circuit may judge that the distance between the headrest and the head is not within the certain range.
The headrest position adjustment device according to the present invention may further comprise distance measuring means which measures the distance between the headrest and the head, and the detecting circuit may judge whether the distance between the headrest and the head is within the certain range or not based on a value measured by the distance measuring means.
In the present invention, when the distance between the headrest and the head is not within the certain range, the detecting circuit may detect the height position of the head with respect to the headrest based on a ratio between the values of capacitances sensed by the sensing electrode located at an uppermost position and a certain number of sensing electrodes counted from this sensing electrode and the values of capacitances sensed by the sensing electrode located at a lowermost position and the certain number of sensing electrodes counted from this sensing electrode.
It is preferred that each of the plurality of sensing electrodes be formed into a rectangular strip shape, and arranged in a front portion of the headrest such that its longer direction is orthogonal to the height direction of the headrest. According to the present invention, it is possible to provide a headrest position adjustment device and a headrest position adjustment method which can highly precisely adjust a position of a headrest automatically and to an appropriate condition with a simple configuration.
A preferred embodiment of a headrest position adjustment device and a headrest position adjustment method according to the present invention will be explained below with reference to the attached drawings.
As shown in
In the present example, the control unit 30 is configured integrally with the capacitance sensor unit 10 and provided on the headrest 43 side. The control unit 30 and the drive motor 44 are electrically connected through a harness 32.
The capacitance sensor unit 10 includes a plurality of sensing electrodes 11 to 15 which are formed on one surface of a substrate 19 for example, and a detecting circuit 20 formed on the other surface of the substrate 19. The capacitance sensor unit 10 senses the capacitance between a head 49a of a person 49 sitting on a sitting portion 42 of the seat 40 and the headrest 43 (more specifically, the sensing electrodes 11 to 15). Thus, the capacitance sensor unit 10 detects the height position of the head 49a with respect to the headrest 43. That is, the capacitance sensor unit 10 senses, at each of the sensing electrodes 11 to 15, the value of capacitance that varies according to the non-flatness of the occipital region, and detects the height position of the head 49a with respect to the headrest 43.
The substrate 19 is made of, for example, a flexible printed board, a rigid substrate, or a rigid flexible substrate. The plurality of sensing electrodes 11 to 15 are made of copper, copper alloy, or aluminum patterned on the substrate 19 which is made of an insulator such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), epoxy resin, or the like.
The plurality of sensing electrodes 11 to 15 are formed into, for example, a rectangular shape. The plurality of sensing electrodes 11 to 15 are arranged in a front portion of the headrest 43 in the state that their longer direction is orthogonal to the height direction of the headrest 43 and that they are arranged side by side along the height direction of the headrest 43. For example, electrode numbers 1 to 5 are assigned to the plurality of sensing electrodes 11 to 15 respectively. In the present example, the plurality of sensing electrodes 11 to 15 include five electrodes. However, the number is not limited to this, but it is only necessary that such a number of electrodes be provided as are needed to detect the height direction of the head 49a of the person 49 sitting on the seat 40 while the headrest 43 is at rest, or more electrodes may be provided.
As shown in
The control circuit 30 includes a motor drive circuit 31 which is connected to the arithmetic processing circuit 28 and controls driving of the drive motor 44 based on a detection result (calculation result) of the arithmetic processing circuit 28.
The drive motor 44 moves the headrest 43 upward or downward based on a control signal output by the motor drive circuit 31.
The capacitance sensing circuits 21 to 25 for outputting information indicative of the capacitance sensed by the sensing electrodes 11 to 15 output a sensing signal by generating and smoothing a pulse signal having a duty ratio which changes according to the capacitance between the sensing electrodes 11 to 15 and the head 49a.
As shown in
The timer circuit 102 includes, for example, two comparators 201 and 202, and an RS flip-flop (hereinafter referred to as “RS-FF”) 203 which receives the outputs from these comparators 201 and 202 at its reset terminal R and its set terminal S respectively. The timer circuit 102 also includes a buffer 204 which outputs an output DES of the
RS-FF 203 to the LPF 103, and a transistor 205 which is controlled between on and off according to the output DIS of the RS-FF 203.
The comparator 202 compares the trigger signal TG shown in
The Q output as a discharge signal DIS turns off the transistor 205. Thus, the sensing electrode 11 (12 to 15) and the ground are electrically charged therebetween at a speed defined by a time constant set by the to-ground capacitance C of the sensing electrode 11 (12 to 15) and a resistor R4 connected between the input terminal and a power supply line. Accordingly, the potential of an input signal Vin rises at a speed defined by the capacitance C.
When the input signal Vin exceeds a threshold Vth1 defined by the resistors R1, R2, and R3, the output of the comparator 201 is inverted, thereby inverting the output of the RS-FF 203. As a result, the transistor 205 is turned on, and the charges accumulated in the sensing electrode 11 (12 to 15) are discharged through the transistor 205.
Hence, the timer circuit 102 outputs a pulse signal Po which, as shown in
The arithmetic processing circuit 28 detects the height position of the head 49a with respect to the headrest 43 based on the sensing signals Vout from the respective capacitance sensing circuits 21 to 25.
The arithmetic processing circuit 28 includes, for example, a CPU, a RAM, a ROM, etc., and compares the sensing signals from the respective capacitance sensing circuits 21 to 25. That is, the arithmetic processing circuit 28 compares the values of capacitances (capacitance values C1 to C5) sensed by the sensing electrodes 11 to 15.
When the smallest value among the capacitance values C1 to C5 is equal to or greater than a threshold, the arithmetic processing circuit 28 compares the capacitance values C1 to C5 and calculates the height position of the sensing electrode having sensed the largest capacitance as an estimated height-direction center position of the head 49a. Then, the arithmetic processing circuit 28 detects the height position of the head 49a based on this calculation result, and outputs the detection result to the motor drive circuit 31.
On the other hand, when the smallest value among the capacitance values C1 to C5 is smaller than the threshold, the arithmetic processing circuit 28 compares the value of capacitance (capacitance value C5) sensed by the sensing electrode 15 located at the uppermost position among the sensing electrodes 11 to 15 arranged side by side along the height direction of the headrest 43 with the value of capacitance (capacitance value C1) sensed by the sensing electrode 11 located at the lowermost position. Then, the arithmetic processing circuit 28 detects the height position of the head 49a based on a ratio between these two capacitance values, and outputs the detection result to the motor drive circuit 31.
The motor drive circuit 31 controls driving of the drive motor 44 based on the detection result (calculation result) of the arithmetic processing circuit 28 to adjust the upward/downward-direction position of the headrest 43 with respect to the backrest 41 of the seat 40. The drive motor 44 can be configured to drive a support shaft 43a of the headrest 43 to move in the upward and downward direction, the leftward and rightward direction, and frontward and rearward direction.
Next, an operation of the headrest position adjustment device 100 according to the present embodiment will be explained with reference to the flowchart shown in
First, the drive motor 44 is driven to move the headrest 43 to an initial position (for example, the highest position that can be reached by the headrest 43 from the backrest 41). After this, at this initial position, the respective sensing electrodes 11 to 15 of the capacitance sensor unit 10 sense the capacitance C between themselves and the head 49a (S100). Then, the arithmetic processing circuit 28 judges whether the smallest value among the values of capacitances (capacitance values C1 to C5) sensed by the sensing electrodes 11 to 15 is equal to or greater than a threshold, or is smaller than the threshold, based on sensing signals from the capacitance sensing circuits 21 to 25 (S102).
When it is judged in step S102 that the smallest value is equal to or greater than the threshold, the arithmetic processing circuit 28 compares the capacitance values C1 to C5. Then, the arithmetic processing circuit 28 calculates an estimated height-direction center position of the head 49a and detects the height position of the head 49a with respect to the headrest 43 (S104). Then, the motor drive circuit 31 controls the drive motor 44 based on this detection result to adjust the upward/downward-direction position of the headrest 43 (S106).
When it is judged in step S102 that the smallest value is smaller than the threshold, the arithmetic processing circuit 28 compares the value of capacitance (capacitance value C5) sensed by the sensing electrode 15 located at the uppermost position among the sensing electrodes 11 to 15 arranged side by side along the height direction of the headrest with the value of capacitance (capacitance value C1) sensed by the sensing electrode 11 located at the lowermost position. Then, the arithmetic processing circuit 28 detects the height position of the head 49a with respect to the headrest 43 based on the ratio between these capacitance values (S108). Then, the motor drive circuit 31 controls the drive motor 44 based on this detection result to adjust the upward/downward-direction position of the headrest 43 (S110).
Here, an example of outputs from the capacitance sensor unit 10 will be explained with reference to the graph of capacitance values shown in
As shown in
That is, when the distance L is about 50 mm. an estimated height-direction center position of the head 49a is calculated based on the values of capacitances sensed by the sensing electrodes 11 to 15. Based on this calculation result, the height position of the head 49a with respect to the headrest 43 can be detected and the position of the headrest 43 can be adjusted.
However, as shown in
Particularly, in the region close to the height position of the center P of the occipital region, it might be impossible to obtain a large/small relationship of the capacitance values that corresponds to the non-flatness of the head due to an influence of disturbance.
In this way, a change of merely about 20 mm in the distance between the head 49a and the front surface of the headrest 43 makes it difficult to detect the height position of the head 49a with respect to the headrest 43. Therefore, it becomes difficult to adjust the position of the headrest.
On the other hand, the ratio (or the difference) between the capacitance value C5 sensed by the sensing electrode 15 located at the uppermost position among the sensing electrodes 11 to 15 arranged side by side in the height direction of the headrest 43 and the capacitance value C1 sensed by the sensing electrode 11 located at the lowermost position is not greatly influenced by the distance L between the headrest 43 and the head 49a. Accordingly, similar ratios are obtained when the distance L is about 50 mm and when the distance L is about 70 mm.
That is, when the distance L between the headrest 43 and the head 49a is large (L=about 70 mm), the values of capacitances (capacitance value C1 and capacitance value C5) sensed by the sensing electrodes 11 and 15 are compared as shown in
The position of the head 49a with respect to the headrest 43 is detected based on the ratio obtained in this way between the values of capacitances sensed by the two sensing electrodes 11 and 15. The adjustment scheme for adjusting the upward/downward-direction position of the headrest based on this detection result can be represented as shown in
That is, assume that the amount of displacement is 0 mm when the height position of the center P of the occipital region of the head 49a is horizontally equal to the height position of the center of the headrest 43. In this case, control signals are output to the drive motor 44 such that the headrest 43 is displaced in the upward direction (+ direction) when the ratio α is close to 0, while the headrest 43 is displaced in the downward direction (− direction) when the ratio α is close to 1.
In the headrest position adjustment device 100 according to the present embodiment, the threshold used as the judgment criterion in step S102 described above is set to, for example, the smallest value among the values of capacitances (capacitance values C1 to C5) that are sensed by the sensing electrodes 11 to 15 when the distance between the headrest 43 and the head 49a is about 60 mm. Thereby, the judgment of whether the distance between the headrest 43 and the head 49a is within the certain range or not can be made based on the values of capacitances sensed by the sensing electrodes 11 to 15.
For example, when the distance between the headrest 43 and the head 49a is equal to or smaller than 60 mm, i.e., when the distance is within the certain range and the smallest value among the capacitance values C1 to C5 is equal to or greater than the threshold, the height position of the head is detected through steps S104 and S106 described above. When the distance between the headrest 43 and the head 49a is greater than 60 mm, i.e., when the distance is not within the certain range and the smallest value among the capacitance values C1 to C5 is smaller than the threshold, the height position of the head is detected through steps S108 and S110 described above. In this way, the height position of the head 49a can be obtained.
This makes it possible to highly precisely adjust the position of the headrest 43 with a simple configuration and prevent accidents due to failure to adjust the position of the headrest 43, such as cervical spine injury of the person 49 in a car crash or the like.
The headrest position adjustment device 100 according to the present embodiment may adjust the height position of the headrest 43 as shown in the flowchart of
Then, the values of capacitances (capacitance values C1 to C5) sensed by the sensing electrodes 11 to 15 are compared. Then, an estimated height-direction center position of the head 49a is calculated, and based on the calculation result, the height position of the head 49a with respect to the headrest 43 is detected (S202). At the same time, the capacitance value C5 sensed by the sensing electrode 15 located at the uppermost position and the capacitance value C1 sensed by the sensing electrode 11 located at the lowermost position arc compared. Based on the ratio between these values, the height position of the head 49a with respect to the headrest 43 is detected (S204).
Next, the value detected in step S202 and the value detected in step S204 are compared. Then, it is judged whether both the values are equal or an error between them is within a predetermined range or not (S206).
When it is judged in step S206 that the values are equal or an error between them is within the predetermined range, the motor drive circuit 31 controls the drive motor 44 based on the value detected in step S202 and adjusts the upward/downward-direction position of the headrest 43 (S208).
When it is judged in step S206 that the error between the values are not within the predetermined range, the motor drive circuit 31 controls the drive motor 44 based on the value detected in step S204 and adjusts the upward/downward-direction position of the headrest 43 (S210).
The headrest position adjustment device 100 according to the present embodiment may be separately provided with a distance sensor (not illustrated) for detecting the distance between the headrest and the head. The distance sensor may be an infrared sensor, a pyroelectric ultraviolet sensor, an optical sensor, an ultrasonic sensor, etc.
When provided with a distance sensor separately, the headrest position adjustment device 100 according to the present embodiment may adjust the height position of the headrest 43 as shown in the flowchart of
When it is judged in step S304 that the distance is within the certain distance, an estimated height-direction center position of the head 49a is calculated based on the capacitance values C1 to C5 sensed by the sensing electrodes 11 to 15. Based on this calculated value, the height position of the head 49a with respect to the headrest 43 is detected (S306). Based on this detection result, the motor drive circuit 31 controls the drive motor 44 and adjusts the upward/downward-direction position of the headrest 43 (S308).
When it is judged in step S304 that the distance is greater than the certain distance, the capacitance value C5 sensed by the sensing electrode 15 located at the uppermost position and the capacitance value C1 sensed by the sensing electrode 11 located at the lowermost position are compared. Based on the ratio between these values, the height position of the head 49a with respect to the headrest 43 is detected (S310). Then, based on this detection result, the motor drive circuit 31 controls the drive motor 44 to adjust the upward/downward-direction position of the headrest 43 (S312).
In the present example, the capacitance sensor unit 10 and drive motor 44 of the headrest position adjustment device 100 are connected through the harness 29. However, they may be configured wirelessly controllable, for example. Alternatively, the drive motor 44 may be configured integrally with the capacitance sensor unit 10 and provided on the headrest 43 side.
In the detection of the height position of the head based on its estimated center position, the detecting circuit 20 controls the headrest 43 to be moved such that its center position comes to the estimated center position mentioned above. Alternatively, the arithmetic processing circuit 28 may profile the occipital shape of the head 49a, calculate the estimated center position mentioned above based on the profiling result, and control the headrest 43 to be moved based on this calculation result. Yet alternatively, the detecting circuit 20 may control the headrest 43 to be moved such that an arbitrary position thereof comes to the estimated center position mentioned above, based on preset profile information about the person 49 (including information about the occipital shape of the head 49a) and information about the shape of the headrest 43.
Further, in the detection of the height position of the head with respect to the headrest 43 based on the comparison between the capacitance value sensed by the sensing electrode 15 located at the uppermost position and the capacitance value sensed by the sensing electrode 11 located at the lowermost position, the detecting circuit 20 may calculate an output ratio a based on the total of the outputs (capacitance values) from the sensing electrode 15 located at the uppermost position and the two sensing electrodes 14 and 13 counted from the sensing electrode 15 and the total of the outputs (capacitance values) from the sensing electrode 11 located at the lowermost position and the two sensing electrodes 12 and 13 counted from the sensing electrode 11. Then, the detecting circuit 20 may likewise detect the height position of the head 49a.
With this configuration of the detecting circuit 20, when detecting the height position of the head with respect to the headrest based on an estimated center position of the head, the detecting circuit 20 scans the capacitances at the respective sensing electrodes 11 to 15 in order through the time division circuit 26. Based on the scanning result, the detecting circuit 20 can obtain an estimated height-direction center position of the head 49a. Meanwhile, when detecting the height position of the head from the values of capacitances sensed by the sensing electrodes 11 and 15 positioned at the lowermost position and the uppermost position, the detecting circuit 20 includes: the time division circuit 26 which is connected to the sensing electrodes 11 and 15; the capacitance sensing circuit 27 which outputs information indicative of the capacitances that are, for example, intertemporally sensed by the sensing electrodes 11 and 15 by means of the time division circuit 26; and the arithmetic processing circuit 28 which calculates the height position of the head 49a by comparing the capacitances that are based on the information output by the capacitance sensing circuit 27. Hence, also with this detecting circuit 20 having such a configuration, it is possible to adjust the position of the headrest 43 highly precisely in a short time.
In the embodiment described above, the explanation has been given by employing as an example a case that the headrest position adjustment device 100 is applied to the headrest 43 of the seat 40 of a vehicle. However, the headrest position adjustment device 100 can also be applied to an attraction vehicle seat, a theater seat, etc. which have a position-adjustable headrest.
The present invention is useful for a device for adjusting the position of a headrest of an automobile, etc., for performing highly precise position adjustment with a particularly simple configuration.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-278086 | Oct 2008 | JP | national |
This application is a continuation-in-part of International Application PCT/JP2009/068616, filed Oct. 29, 2009, the disclosure of which is incorporated herein by reference in its entirety. This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2008-278086, filed on Oct. 29, 2008, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2009/068616 | Oct 2009 | US |
| Child | 13097805 | US |
