Abstract:
Herein disclosed is a control circuit for controlling operation of electrically operated seat back pivoting device, which includes therein a transistor to control the current when the latter is applied to the motor of the device in a direction to pivot the seat back rearward. With this arrangement, the rearward pivoting movement of the seat back is carried out with small torque.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to an electric reclining seat for automobiles, and more particularly to an electric control circuit for controlling operation of such reclining seat. 
     2. Description of the Prior Art 
     Hitherto, various kinds of electrically operated reclining seats have been proposed and put into practical use in the field of automobiles. However, as will be outlined hereinafter, some of the conventional electric reclining seats have drawbacks due to their inherent constructions. That is, the pivoting movement of the seat back relative to the seat cushion is carried out with considerably high torque. Thus, sometimes, the rearward tilting of the seat back induces injury to a passenger who sits behind the seat. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a safety system for such electric reclining seat. 
     It is another object of the present invention to provide an improved control circuit for such electric reclining seat, which never induces injury to a rear seat occupant even when the seat back collides againt the occupant during the rearward pivoting movement thereof. 
     According to the present invention, there is provided a seat which comprises a seat cushion, a seat back, pivoting means arranged between the seat cushion and the seat back so as to achieve a pivoting movement of the seat back relative to the seat cushion, an electric motor incorporated with the pivoting means to pivot through the pivoting means the seat back in a forward or rearward direction when electrically energized, a switch interposed between a battery and the motor and having first and second conditions, the first condition being a condition wherein the current from the battery is applied to the motor to drive the same in one direction to pivot the seat back in one direction, the second condition being a condition wherein the current from the battery is applied to the motor to drive the same in the other direction to pivot the seat back in the other direction, and control means incorporated with the switch in a manner to control the intensity of current applied to the motor when the switch assumes the first condition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a control circuit for controlling operation of an electrically operated reclining seat, which is an embodiment of the present invention; 
     FIG. 2 is a side view showing front and rear seats of an automobile, with a child sitting on the rear seat; and 
     FIG. 3 is a control circuit conventionally used. 
    
    
     DESCRIPTION OF A CONVENTIONAL ELECTRIC RECLINING SEAT 
     Prior to describing in detail the present invention, one conventional control circuit for the electrically operated reclining seat will be described with reference to FIGS. 2 and 3 in order to clarify the task of the present invention. 
     Referring to FIG. 2, there is shown front and rear seats 100 and 200 mounted in an automobile, with a child &#34;C&#34; sitting on the rear seat 200. Each seat 100 or 200 comprises a seat cushion 102 or 202 and a seat back 104 or 204. The front seat 100 is equipped with an electrically operated seat back pivoting device by which the angular position of the seat back 104 relative to the seat cushion 102 is adjustable. The electric seat back pivoting device comprises a known electric motor &#34;M&#34; (see FIG. 3) and a known gear mechanism (not shown) which are incorporated with the seat back 104 in such a manner that under driving of the motor in one direction, the seat back 104 is pivoted rearward, that is, toward the rear seat 200, and under driving of the motor in the other direction, the seat back 104 is pivoted forward, that is, toward the seat cushion 102. 
     In FIG. 3, there is shown a conventional control circuit 300 which is employed in the electric seat back pivoting device for controlling operation of the motor &#34;M&#34;. The control circuit 300 comprises a switch &#34;S&#34; which is intersposed between a battery &#34;B&#34; (12V, for example) and the electric motor &#34;M&#34;. The switch S comprises first and second switch mechanisms S 1  and S 2 , each including three stationary contacts a 1 , b 1  and c 1  (or a 2 , b 2  and c 2 ). and one movable contact d 1  (or d 2 ). As shown, the stationary contacts a 1  and c 2  are connected and then extend to a positive terminal of the battery B, while the stationary contacts c 1  and a 2  are connected and extend through the automotive body to a negative terminal of the battery B. The stationary contacts b 1  and b 2  are of a neutral contact having no connection with any member. The movable contacts d 1  and d 2  are connected through the motor &#34;M&#34; and constructed to move synchronously in a manner to carry out &#34;a 1  -a 2  &#34; connection, &#34;b 1  -b 2  &#34; connection or &#34;c 1  -c 2  &#34; connection. When, with the above-mentioned arrangement, the switch S assumes the illustrated condition wherein the movable contacts d 1  and d 2  contact the stationary contacts a 1  and a 2  respectively, the current from the battery B flows through the stationary contact a 1 , the movable contact d 1 , the motor &#34;M&#34;, the movable contact d 2  and the stationary contact a 2  and returns back to the battery B. During this electric supply to the motor &#34;M&#34;, the seat back 104 is pivoted rearward, that is, toward the rear seat 200. When, thereafter, the movable contacts d 1  and d 2  are switched to the neutral points b 1  and b 2 , the rearward pivoting movement of the seat back 104 stops due to deenergization of the motor &#34;M&#34;. When, then, the movable contacts d 1  and d 2  are shifted to the other stationary contacts c 1  and c 2 , the current from the battery B is applied to the motor &#34;M&#34; from the reversed direction thereby pivoting the seat back 104 forward. Of course, this forward pivoting movement stops when the movable contacts d 1  and d 2  are shifted to the neutral contacts b 1  and b 2 . 
     However, the above-mentioned arrangement has the following drawback due to its inherent construction. That is, due to the nature of the control circuit 300, the torque of the motor &#34;M&#34; is considerably high. Thus, if a passenger, for example, a child &#34;C&#34; occupies the rear seat 200 when the seat back 104 is pivoting rearward, there is a high possibility of injuring the child with a corner portion of the seat back 104, as may be understood from the seat back 104 illustrated by broken line in FIG. 2. One attempt to solve this drawback is to put a resistor between the stationary contact a 2  and the automotive body. However, this atempt induces not only high electric loss but also dangerous matter wherein the sorrounding of the resistor may burn due to heat generated by the same. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is shown an improved control circuit according to the present invention, which is free of the above-mentioned drawbacks. 
     The control circuit 10 of the invention comprises a switch S which includes, similar to the above-mentioned switch of FIG. 3, first and second groups of switch mechanisms S 1  and S 2 . Each mechanism has three stationary contacts a 1 , b 1  and c 1  (or a 2 , b 2  and c 2 ) and one movable contact d 1  (or d 2 ). The stationary contacts a 1  and c 2  are connected and then extend to the positive terminal of the battery B. The movable contacts d 1  and d 2  are connected through the motor &#34;M&#34; and constructed to move synchronously in a manner to carry out &#34;a 1  -a 2  &#34; connection, &#34;b 1  -b 2  &#34; connection or &#34;c 1  -c 2  &#34; connection. The stationary contact c 1  is connected to the automotive body to which the negative terminal of the battery B is connected. The movable contact d 1  is connected to a fixed resistor 12 which is, in turn, connected to a variable resistor 14. The variable resistor 14 is connected to a Zener diode 16 which, in turn, is connected to the automotive body. A N-P-N type transistor 18 is arranged with its base connected to the line extending between the variable resistor 14 and the diode 16. The collector of the transistor 18 is connected to the stationary contact a 2  of the switch S. Arranged between the stationary contact a 2  and the movable contact d 1  is a diode 20 which functions to protect the transistor 18. The emitter of the transistor 18 is connected to the automotive body. 
     When, in operation, the switch S assumes the illustrated first condition wherein the movable contacts d 1  and d 2  contact the stationary contacts a 1  and a 2  respectively, desirable rearward pivoting of the seat back 104 is carried out in a manner as will be described hereinafter. When the movable contacts d 1  and d 2  are shifted to the neutral contacts b 1  and b 2 , the pivoting movement of the seat back 104 stops due to deenergization of the motor &#34;M&#34;. When, thereafter, the movable contacts d 1  and d 2  are shifted to the other stationary contacts c 1  and c 2  respectively due to shifting of the switch 5 to its second condition, the current from the battery B flows through the stationary contact c 2 , the movable contact d 2 , the motor &#34;M&#34;, the movable contact d 1  and the stationary contact c 1  and returns back to the battery B through the automotive body. Under this condition, the seat back 104 is pivoted forward with considerable torque in substantially the same manner as is mentioined hereinafore. 
     The rearward pivoting of the seat back 104 will be described in detail hereinnext. 
     When the switch S assumes the illustrated first condition, a first series circuit including the battery B, the motor &#34;M&#34; , the collector and the emitter of the transistor 18 is established, and at the same time, a second series circuit including the battery B, the movable contact d 1 , the fixed resistor 12 and the variable resistor 14 and the base of the transistor 18 is established. Thus, in this condition, the collector and the emitter of the transistor 18 are electrically connected, so that current from the battery B is applied to the motor &#34;M&#34; to pivot the seat back 104 rearward. It is to be noted that manipulating the variable resistor 14 varies the base current of the transistor 18 and thus varies the current flowing through the above-mentioned first series circuit. Thus, the speed of the motor &#34;M&#34; can be adjusted by manipulating the variable resistor 14. The Zener diode 16 controls the base voltage of the transistor 18 so as to limit the upper value of the current which flows in the first series circuit. Preferably, the Zener voltage of the Zener diode 16 is controlled to about 2 volts when the battery B is of 12 volt type. Thus, the rearward pivoting of the seat back 104 can be carried out with small current applied to the motor &#34;M&#34;. That is, the rearward pivoting of the seat back 104 is carried out with small torque. 
     Thus, even when the seat back 104 collides against a rear seat occupant &#34;C&#34; during its rearward pivoting, injury of the occupant never occurs. That is, upon collision, the pivoting movement of the seat back 104 stops instantly due to small torque of the motor &#34;M&#34;. The forward pivoting of the seat back 104, due to the shifting of the switch 5 to its second condition, is carried out with large torque by the reason as mentionied hereinfore. 
     Due to the nature of the arrangement of the resistors 12 and 14 and the transistor 18, electric consumption of them is small and thus heat generated by them is small. Thus, the dangerous fire of the circuit does not occur.