STRETCHABLE WIPER APPARATUS FOR VEHICLE

Abstract: The apparatus includes first (58) and second (56) arms. One end portion of the first arm (58) is rigidly secured to a wiper arm pivoting shaft. One end portion of the second arm is secured to a wiper blade (54), and the other end portion of the second arm is pivotally supported by the other end portion of the first arm (58). A stretching mechanism is provided between the first and second arms (56,58) for bending and stretching the second arm (56) relative to the first arm (58). An actuator for activating the stretching mechanism is provided on the wiper arm pivoting shaft. Accordingly, when the wiper is not used, the second arm (56) can be bent relative to the first arm (58), so that an occupant of the vehicle is allowed to have an improved view of the outside from the inside of the vehicle.

Description: BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to a wiper apparatus for a vehicle and, more particularly, to a stretchable wiper apparatus having a foldable wiper arm. 2. Description of the Related Art Conventional wiper apparatuses for vehicles suffer from the following problems. Namely, the overall length of a wiper arm and a wiper blade, which constitute a wiper assembly of a typical conventional wiper apparatus for a vehicle, is disadvantageously long, and the wiper assembly is inconveniently positioned at the lower end of the front side of a window glass of the vehicle when it is not used, which inhibits an occupant of the vehicle from having a clear view of the outside from the inside of the vehicle and which involves a fear of the wiper assembly interfering with an external machine or member for the vehicle, such as a car cover, a car washing machine or the like. In order to overcome the above-described problems, there has already been proposed one type of wiper apparatus which is so designed that a wiper assembly, particularly, a wiper arm and a wiper blade, can be accommodated in a portion of the inside of the vehicle which is in the vicinity of the window glass (see, e.g., U.S. Patent Application Serial No. 660,050, Japanese Utility Model Application Nos. l5834l/l983 and l68232/l983). However, this type of wiper apparatus has the problem that the size of a chamber for accommodating the wiper arm and the wiper blade is unfavorably large and cannot be minimized. SUMMARY OF THE INVENTION In view of the above-described circumstances, it is a primary object of the present invention to provide a stretchable wiper apparatus for a vehicle which is so designed that the wiper arm can be folded when the wiper is not used. To this end, the present invention provides a stretchable wiper apparatus for a vehicle, comprising: a first arm secured to a wiper arm pivoting shaft and pivoted within a predetermined angle about the shaft; a second arm secured at one end portion thereof to a wiper blade which is pressed against the surface of a window glass of the vehicle to wipe the window glass surfce, the other end portion of the second arm being pivotally supported by the first arm; and stretching means for expanding and contracting the overall length of the first and second arms. By virtue of the above-described arrangement, when the wiper is not used, the second arm is pivoted so as be laid on the first arm, so that it is possible to reduce the overall length of the first and second arms. Thus, it is possible to reduce the size of a portion of the wiper which projects from the outer surface of the vehicle, and an occupant of the vehicle is allowed to have an improved view of the outside from the inside of the vehicle. In addition, it is possible to minimize the interference between the wiper and an external machine or member for the vehicle. When the wiper is to be used, the second arm is stretched so as to extend in the longitudinal direction of the first arm, and the wiper is then activated to wipe away raindrops and the like attached to the surface of the window glass. When the present invention is applied to a concealable wiper apparatus, it is possible to minimize the space required to provide a chamber for accommodating the wiper apparatus. The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. l is a partially-cutaway perspective view of a first embodiment of the present invention, which shows the wiper assembly which is accommodated in an accommodating chamber defined by a cowl inner member of a vehicle; Fig. 2(A) is a perspective view showing the wiper assembly in a rise-up state; Fig. 2(B) is a perspective view showing the wiper assembly in a state wherein the first arm which is bent in the state shown in Fig. 2(A) is stretched; Fig. 2(C) is a perspective view showing the wiper assembly in a state wherein it is popped up and the second arm is stretched relative to the first arm; Fig. 3(A) is a vertical sectional view showing the wiper assembly accommodated in the accommodating chamber; Fig. 3(B) is a vertical sectional view showing the wiper assembly in a state wherein the louver is opened and the wiper assembly is popped up; Figs. 4(A) to 4(C) are front views showing the arrangement of the louver; Fig. 5 is a perspective view of driving means for stretching and pivoting the wiper arm; Figs. 6(A) to 6(C) are plan views employed to describe the operation of the driving means shown in Fig. 5; Figs. 7(A) and 7(B) are plan views showing the internal structure of the wiper arm; Fig. 8(A) is a plan view of the wiper arm; Fig. 8(B) is a longitudinal sectional view of the wiper arm shown in Fig. 8(A); Fig. 9 shows a wiper control circuit; Figs. l0 to l3 are flowcharts showing the control of the wiper and the washer; Fig. l4 is a longitudinal sectional view corresponding to Fig. 8(B), which shows a second embodiment of the present invention; Fig. l5 is a longitudinal sectional view corresponding to Fig. 8(B), which shows a third embodiment of the present invention; and Fig. l6 is a fragmentary plan view of the synchronizing rubber belt shown in Fig. l5. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described hereinunder with reference to the accompanying drawings. Referring first to Fig. 3, which shows a first embodiment of the present invention, a wiper assembly l0 is accommodated in an accommodating chamber l6 provided between a front glass l2 and a hood l4. The accommodating chamber l6 is defined by a cowl inner member l8 which is horizontally carried by front pillars (not shown). One end of the cowl inner member l8 on the side thereof which is closer to the rear end of the vehicle is bonded to the front glass l2 by means of an adhesive 20. A reinforcement member 22 is provided on the side of the cowl inner member l8 which is closer to the front end of the vehicle in such a manner that the front end portion of the reinforcement member 22 and the front end portion of the cowl inner member l8 are superposed one upon the other and clamped by a weatherstrip retaining member 24. A weatherstrip sealing member 26 is stuck to the reverse surface of the hood l4 in opposing relation to the weatherstrip retaining member 24, thereby ensuring sealing between the hood l4 and the cowl inner member l8. As shown in Fig. 2(A), an opening 29 having a substantially rectangular cross-section is provided between the front glass l2 and the hood l4 by cutting the hood l4. This opening 29 is closed by a louver 28 which is slidably provided so as to selectively close and open the opening 29. When the louver 28 is in the state shown in Fig. 3(A), the surface of the louver 28 and the surfaces of respective portions of the front glass l2 and the hood l4 which are near the louver 28 are flush with each other in order to minimize the air resistance to the vehicle. Referring to Fig. l, the louver 28 is adapted to slide while being guided by a pair of guide rails 30 and 32 which are provided along both edges (in the lateral direction of the vehicle), respectively, of the opening 29. As will be clear from Fig. 4, a slider ll is provided in such a manner as to be movable along the guide rail 30. More specifically, both longitudinal end portions on one side of the slider ll are supported by the guide rail 30 through supporting members llA and llB, respectively. A rack l3 is formed on the other side of th slider ll, and meshed with a pinion l5. The pinion l5 is operatively connected to a louver motor 34 shown in Fig. l, the motor 34 being rigidly secured to the body of the vehicle. The louver 28 has brackets l7 and l9 projecting from the lower surface thereof. The bracket l7 is provided with a slot 2l which receives a pin 23 which projects from the slider ll. The bracket l9 is pivotally supported at one end portion of a link bar 25 which, in turn, is pivotally supported by the slider ll. Both end portions of a torsion spring 27 are respectively retained by the other end portion of the link bar 25 and the slider ll in such a manner that the link bar is biased so as to pivot in the direction of the arrow P. A safety plate 29 is rigidly secured to the vehicle body in order to prevent the link bar 25 from pivoting counter to the direction of the arrow P so as to rise undesirably. A stopper 3l is rigidly secured to the upper end of the guide rail 30 to limit the movement of the bracket l7 toward the front glass l2. When the louver 28 is in the open position shown in Fig. 4(A), if the pinion l5 is rotated counterclockwise, the louver 28 slides along the guide rail 30 toward the front glass l2 until the bracket l7 abuts against the stopper 3l as shown in Fig. 4(B). As the pinion l5 is rotated further in the same direction, i.e., counterclockwise, the pin 23 is guided by the slot 2l, and the distal end of the slider ll abuts against the stopper 3l. At this time, the bracket l9 is moved relative to the slider ll toward the lower end of the guide rail 30 (toward the front end of the vehicle). In consequence, the link bar 25 pivots clockwise to rise against the biasing force from the torsion spring 27, so that the upper end of the louver 28 abuts against the upper surface of the lower end portion of the front glass l2 as shown in Fig. 4(C). The portion of the louver 28 on the side thereof which is closer to the guide rail 32 is driven by the rotational force derived from the louver motor 34 which is transmitted through a cable accommodated in a pipe 36 and through a combination of a rack and a pinion similar to the above. The drive unit for driving the wiper assembly l0 is accommodated in a wiper box 38. This wiper box 38 is supported by a pair of hinges 40 which are rigidly secured to the reinforcement member 22 so that the wiper box 38 is pivotal about a supporting point 42. The driving source for this pivotal motion of the wiper box 38 is a pop-up motor 44. A worm (not shown) is secured to the rotating shaft of the pop-up motor 44, and meshed with a worm wheel (not shown) which is accommodated in a casing 46. The pop-up motor 44 is rigidly secured to the casing 46. The casing 46 is rigidly secured through projecting portions 48 to a reinforcement member (not shown) which extends perpendicularly to the cowl inner member l8, i.e., to one side wall of the accommodating chamber l6. An arm 50 is secured to a rotating shaft 49 of the above-described worm wheel. The distal end of the arm 50 and one side surface of the wiper box 38 are connected by a rod 52 so that the pivotal motion of the arm 50 causes the wiper box 38 to pivot about the supporting point 42. Accordingly, if, in the state shown in Fig. 3(A), the louver motor 34 is rotated forward to slide the louver 28 so as to open the opening 29 and the pop-up motor 44 is rotated forward, the wiper assembly l0 is popped up as shown in Fig. 3(B). As shown in Fig. l, the wiper assembly l0 is provided with a wiper blade 54 for wiping away raindrops or the like attached to the front glass l2. The wiper blade 54 is supported at the central portion thereof by a first arm 58 through a second arm 56. Referring to Figs. 7 and 8, the second arm 56 is pivotally supported by the first arm 58 through an arm stretching shaft 60 rigidly secured to the arm 56. A pinion 62 is rigidly secured to the arm stretching shaft 60 in coaxial relation to each other, and incorporated in the first arm 58. The first arm 58 further incorporates a rod 64 which is provided at one end portion thereof with a rack 66 that is meshed with the pinion 62. The other end portion of the rod 64 is operatively connected to a crank arm 70 through a pin 68. Accordingly, as the crank arm 70 pivots, the rod 64 is linearly moved, and the pinion 62 is consequently rotated, thus causing the second arm 56 to pivot about the arm stretching shaft 60. In other words, it is possible to fold the second arm 56 in such a manner that it is laid on the first arm 58. Accordingly, it is possible to minimize the space required to provide the accommodating chamber l6 and reduce the size of the apparatus as a whole. Referring to Fig. 8, a second arm head 57 of the second arm 56 is pivotally supported by the first arm 58 through the arm stretching shaft 60. The second arm head 57 pivotally supports one end portion of a retainer 6l through a pin 59. One end portion of a second arm piece 63 is rigidly secured to the other end portion of the retainer 6l. The wiper blade 54, shown in Fig. l, is rigidly secured to the other end portion of the second arm piece 63. A hook 65 is formed at the first end of the second arm piece 63 so as to retain one end of a tension coil spring 67. The first arm 58 has a hook 69 projecting from a position thereon which is a distance D apart from the arm stretching shaft 60 to the right of the shaft 60 as viewed in Fig. 8, the hook 69 retaining the other end of the spring 67. Referring to Fig. 8(A), when the second arm 56 is stretched in such a manner as to extend in the longitudinal direction of the first arm 58, the second arm piece 63 is subjected to a counterclockwise moment about the pin 59 by the biasing force from the tension coil spring 67, whereby the wiper blade 54 is pressed against the front glass l2. As illustrated by the two-dot chain line in Fig. 8(A), when the second arm 56 is in a folded state, the length of the tension coil spring 67 is 2D shorter than that in the case where the second arm 56 is stretched, and the pulling force of the spring 67 is reduced corresponingly. Accordingly, the drag which is applied to the wiper blade 54 from the front glass l2 becomes sufficiently small so that no unnecessarily large force is applied to the wiper blade 54 when the wiper is not used. Thus, it is possible to prevent deformation of the rubber member of the wiper blade 54, that is, lowering in the wiping function of the wiper blade 54. It should be noted that a compression coil spring may be employed in place of the tension coil spring 67. In such case, a spring retainer is provided in place of the hook 69 and disposed at a position to the left of and on the upper side of the arm stretching shaft 60 as viewed in Fig. 8(A). The crank arm 70 is rigidly secured to one end portion of an arm stretching driving shaft 72. The shaft 72 is rotatably supported by an inner bearing 74 which also serves as a wiper arm pivoting shaft. The distal end portion of the inner bearing 74 is rigidly secured to the first arm 58 by means of a nut 76. A worm wheel 78 is rigidly secured to the lower end portion of the arm stretching driving shaft 72, and a worm 80 is meshed with the worm wheel 78. The worm wheel 78 and the worm 80 are incorporated in a casing 82 from which the inner bearing 74 projects. The worm 80 is rotated by an arm stretching motor 84 which is rigidly secured to the casing 82. The inner bearing 74 is rotatably supported by an outer bearing 86 in such a manner that the first arm 58, the inner bearing 74, the casing 82 and the arm stretching motor 84 pivot together in one unit. The outer bearing 86 is rigidly secured to an upper plate 88 of the wiper box 38 as shown in Fig. 5. The arm stretching motor 84 is disposed on the side of the arm stretching driving shaft 72 which is remote from the first arm 58, so that the moment about the inner bearing 74 based on the gravity acting on the wiper blade 54, the second arm 56 and the first arm 58 is canceled by the moment about the inner bearing 74 based on the gravity acting on the arm stretching motor 84. Accordingly, it is possible to prevent the inner and outer bearings 74 and 86 from becoming worn locally to a substantial extent, which phenomenon would otherwise occur due to the eccentricity of the inner bearing 74 with respect to the outer bearing 86. Referring to Fig.3(A), a mole ll4 which serves as a closure member is rigidly secured to the inner bearing 74. When the wiper assembly l0 is popped up, mole ll4 closes the opening 29 as shown in Fig. 3(B). Accordingly, even when the wiper assembly l0 is in a rise-up state, there is no fear of dust or the like entering the accommodating chamber l6. Since, in this state, the mole 87 is substantially flush with the front glass l2 and the hood l4, it is possible to reduce the air resistance to the vehicle. In addition, the external appearance of the vehicle is improved. A link arm 90 is rigidly secured to the casing 82, while a link arm 92 is pivotally supported by the upper plate 88 through a pin 94. The link arms 90 and 92 are operatively connected by a link bar 96 through pins 98 and l00. The link arms 90, 92 and the link bar 96 constitute in combination a U-link. One end portion of a rod l02 is pivotally supported by the intermediate portion of the link arm 92 through a pin l04. A wiper motor l06 is rigidly secured to a casing l08. This casing l08 incorporates a worm (not shown) which is secured to the rotating shaft of the wiper motor l06 and a worm wheel (not shown) which is supported on an arm driving shaft ll0. The casing l08 is rigidly secured to a lower plate 89 of the wiper box 38. An arm ll2 is rigidly secured to the arm driving shaft ll0. The distal end portion of the arm ll2 is rotatably connected to the rod l02. Accordingly, as the wiper motor l06 is activated, the arm ll2 is turned, and the link arm 92 is thereby pivoted about the pin 94 through the rod l02. In consequence, the link arm 90 is pivoted through the link bar 96, thus causing the arm motor 84, the inner bearing 74 and the first arm 58 shown in Fig. 8 to pivot together in one unit. Figs. 6(A) to 6(C) show in combination the way in which the above-described wiper arm driving section operates. Fig. 6(A) shows the driving section in a wiper arm accommodating position where the wiper assembly l0 is in the position shown in Fig. l. When, in this state, the arm ll2 is pivoted counterclockwise to reach a position at which it is directed in the direction of the arrow X, the driving section is brought to a wiper arm turning position X where the wiper assembly l0 is in the position shown in Fig. 2(A). In this state, the arm stretching motor 84 is activated to stretch the second arm 56 as shown in Fig. 2(B). As the arm ll2 is rotated further counterclockwise to reach a position at which it is directed in the direction of the arrow Z as shown in Fig. 6(C), the wiper blade 54 is moved from the position AA' to the position BB' shown in Fig. 2(B). A the arm ll2 is pivoted further counterclockwise to reach a position at which it is directed in the direction of the arrow Y as shown by the one-dot chain line in Fig. 6(B), the wiper blade 54 is returned to the position AA' from the position BB' shown in Fig. 2(B). The position where the arm ll2 is directed in the direction of the arrow Y defines the wiper arm turning position Y. Accordingly, as the arm ll2 is pivoted from the position X to the position Y, the wiper blade 54 reciprocates once. The arm ll2 is pivoted back and forth, i.e., both counterclockwise from the position X to the position Y and clockwise from the position Y to the position X. In relation to this, when the wiper assembly l0 is in a pop-up state (see Fig. 3(B)), the first arm 58 is in the position shown in Fig. l. If, in this state, the second arm 56 is pivoted in the direction in which it is unfolded, it is impossible to stretch the first and second arms 58 and 56 in a substantially straight line as shown in Fig. 2(C). In order to obtain a satisfactorily large wiping area, it is therefore necessary to increase the length of each of the first and second arms 58 and 56, which means that the overall length of the wiper arm and the wiper blade when they are folded cannot sufficiently be reduced. Therefore, according to the present invention, the wiper motor l06 is temporarily activated in a state wherein the wiper assembly l0 has been popped up and the second arm 56 is folded in such a manner as to be laid on the first arm 58, so as to pivot the first arm 58 to the wiper arm turning position X (the wiping start position), and then, with the wiper motor l06 suspended, the second arm 56 is unfolded. It should be noted that the above-described operation, in which, after the wiper assembly l0 has been popped up, the wiper motor l06 is temporarily activated to pivot the first arm 58 to the wiper arm turning position X is defined as the rise-up of the first arm 58. Referring next to Fig. 9, which shows a wiper control circuit, the wiper control is effected by a microcomputer l50. The microcomputer l50 has an input port l52 to which are input detection signals from various sensor means: namely, a rain sensor l54, a wiper mode changeover switch l56, a washer switch l58, a louver open limit switch l60, a louver close limit switch l62, a pop-up limit switch l64, a pop-down limit switch l66, an arm expansion limit switch l68, an arm contraction limit switch l70, a wiper arm accommodated position limit switch l72, a wiper arm turning position X limit switch l74, and a wiper arm turning position Y limit switch l76. The rain sensor l54 is constituted by, e.g., an infrared photointerrupter or a voltage element, and adapted to detect whether or not there is rain. The wiper mode changeover switch l56 is adapted to supply the input port l52 with contact signals which respectively represent OFF, the automatic mode (AUTO), the low-speed mode (Lo) and the high-speed mode (Hi). Both the louver open limit switch l60 and the pop-up limit switch l64 are closed slightly before the wiper assembly l0 is brought to the position shown in Fig. 3(B), whereas both the louver close limit switch l62 and the pop-down limit switch l66 are closed slightly before the wiper assembly l0 is brought to the position shown in Fig. 3(A). The arm expansion limit switch l68 is closed slightly before the second arm 56 is brought to the position shown in Fig. 2(B), whereas the arm contraction limit switch l70 is closed slightly before the second arm 56 is brought to the position shown in Fig. 2(A). Further, the wiper arm accommodated position limit switch l72 is closed when the wiper driving section is in the position shown in Fig. 6(A), while the wiper arm turning position X limit switch l74 is closed when the wiper driving section reaches the position shown by the solid line in Fig. 6(B), and the wiper arm turning position Y limit switch l76 is closed when the wiper driving section reaches the position shown by the one-dot chain line in Fig. 6(B). The microcomputer l50 has an output port l78 from which driving signals are supplied to a driver l80 so as to activate the louver motor 34, the arm motor 84, the wiper motor l06 and the washer motor l82. The lock current flowing when the rotation of each of the louver motor 34 and the arm motor 84 is mechanically restrained is detected by each of the lock current detectors l84 and l88 and input to the input port l52 as an interrupt signal which is supplied to a CPU l90. The microcomputer l50 has the CPU l90 for executing a control program, a ROM l92 for storing the control program, a RAM l94 employed as a work area, the input and output ports l52 and l78, and a bus l96 for connecting together these members. The operation of this embodiment, arranged as detailed above, will be explained below with reference the control flowcharts shown in Figs. l0 to l3. Fig. l0 shows a control flowchart showing the operation executed when the wiper mode changeover switch l56 is set to the AUTO, Lo or Hi mode. The operation which is executed when the wiper mode changeover switch l56 is switched over to the Lo mode when the wiper assembly l0 is in the position shown in Fig. 3(A) will first be explained. It should be noted that the reference symbol LS in the flowcharts denotes a limit switch. Since, in this state, the louver open limit switch l60 is OFF, the process proceeds from Step 200 to Step 202, in which the louver motor 34 is rotated in the direction in which the louver 28 is opened. The process then proceeds to Step 204, and when the louver open limit switch l60 turns ON, the pop-up motor 44 is rotated in the direction in which the wiper assembly l0 is popped up in Step 206. The process stays in Step 208 until the pop-up limit switch l64 turns ON. Meantime, the louver 28 reaches the position shown in Fig. 3(B), and a lock current is detected by the lock current detector l84. In consequence, the CPU l90 is interrupted to start the control flowchart shown in Fig. ll. More specifically, the cause of the interrupt is judged in Step 300, and the process proceeds to Step 302, in which the louver motor 34 is turned OFF, and the process returns to Step 208. The employment of the louver open limit switch l60 and the lock current detector l84 enables the wiper assembly l0 to be popped up when the louver 28 is opened substantially completely, and allows the parallel processing of the louver opening operation and the pop-up operation, so that it is possible to reduce the time required to activate the wiper assembly l0. In addition, since the rotation of the louver motor 34 is suspended in response to the detection of the lock current, it becomes unnecessary to adjust the stop position of the louver 28, and the rotation of the louver motor 34 is suspended when the louver 28 is opened substantially completely, thus preventing chattering of the louver 28. When the pop-up limit switch l64 turns ON in Step 208, the pop-up motor 44 is turned OFF in Step 209. In this state, the mole ll4 is brought into close contact with the lower end portion of the front glass l2. Since the wiper assembly l0 is pivoted about the supporting point 42, the distance between the supporting point 42 and the lower end portion of the front glass l2 is sufficiently large so that there is no risk of the mole ll4 applying any excessively large force to the front glass l2. Then, the process proceeds to Step 2l0, in which the wiper motor l06 is rotated forward. When the wiper arm turning position X limit switch l74 turns ON in Step 2l2, the process proceeds to Step 2l4, in which the operation of the wiper motor l06 is suspended. Thus, the rise-up is completed as shown in Fig. 2(A). Then, the process proceeds from Step 2l6 to Step 2l8, in which the arm motor 84 is rotated in the direction in which the second arm 56 is stretched. When the arm expansion limit switch l68 turns ON in Step 220, the process proceeds to Steps 232 and 234, and the wiper motor l06 is rotated forward at low speed in Step 234. The process then proceeds to Step 235 and stays there until the wiper arm turning position Y limit switch l76 turns ON. Meantime, a lock current flows through the arm motor 84 and is detected by the lock current detector l88 to start the interrupt processing shown in Fig. ll. More specifically, the process proceeds to Steps 300 and 306, and the arm motor 84 which has been turned ON in Step 2l8 is turned OFF in Step 306, the process then returning to Step 236. Meantime, the wiper blade 54 is pivoted clockwise as viewed in Fig. 2(B) in such a manner as to move from the position AA' to the position BB', and then returned to the position AA'. In consequence, the wiper arm turning position Y limit switch l76 turns ON, and the process proceeds from Step 236 to Steps 238 and 240, and the wiper motor l06 is temporarily turned OFF and then reversed at low speed immediately thereafter in Step 240. The process then proceeds to Step 242 and stays there until the wiper arm turning position X limit switch l74 turns ON. When the wiper blade 54 further makes one reciprocating motion on the surface of the front glass l2, the wiper arm turning position X limit switch l74 turns ON. The process then proceeds from Step 242 to Steps 244 and 232, and the above-described processing is repeated thereafter. The following is a description of the operation executed when the wiper mode changeover switch l56 is switched over to the Hi mode. In this case, the process proceeds from Step 232 to Step 246 and from Step 238 to Step 248 to rotate the wiper motor l06 at high speed. For the other control steps, the process proceeds in the same manner as that in the case of the above-described Lo mode. When the wiper mode changeover switch l56 is switched over to the AUTO mode, the operation is executed as follows. After Steps 200 to 2l6 have been executed in the same manner as the above, the process proceeds to Step 250, in which a 30-second timer is turned ON. The processing of Steps 252 and 254 is then repeated until a rain signal which represents that there is rain is output from the rain sensor l54. If a rain signal is received within 30 seconds, the process proceeds from Step 252 to Step 256. Since the wiper assembly l0 is in the position shown in Fig. 2(A), the process proceeds from Step 256 to Step 2l8, and the processing of Steps 2l8 to 236 is executed in the same manner as that in the case of the Lo mode, whereby the second arm 56 is stretched and the wiper blade 54 is reciprocated once on the surface of the front glass l2. Then, the process proceeds to Step 237, in which, if the microcomputer l50 receives a rain signal from the rain sensor l54, the processing of Steps 238 to 258 is executed, and the wiper blade 54 is actuated to make one reciprocating motion on the surface of the front glass l2. When the rain has stopped, no rain signal is supplied from the rain sensor l54. In consequence, the process proceeds from either Step 237 or 258 to Step 260, in which the wiper motor l06 is turned OFF when either the wiper arm turning position X limit switch l74 or the wiper arm turning position Y limit switch l76 turns ON. Then, the 30-second timer is turned ON in Step 250, and the processing of Steps 252 and 254 is repeatedly executed until a rain signal is supplied. If there is rain again within 30 seconds, the process proceeds from Step 252 to Steps 256 and 232, and the processing similar to the above is repeated thereafter. Accordingly, if rain is sensed again within 30 seconds, the second arm 56 is allowed to remain stretched. It is therefore possible to avoid conducting the wasteful operation in which the second arm 56 is contracted and expanded again. If no rain signal is supplied from the rain sensor l4 even when 30 seconds has elapsed after the timer has been turned ON in Step 250, the process proceeds from Step 254 to Steps 262 and 264, and the arm motor 84 is rotated in the direction in which the second arm 56 is bent. Then, when the arm contraction limit switch l70 turns ON in Step 266, the process returns to Step 250, in which the timer is turned ON again. Then, the processing of Steps 252 and 254 is repeated. Meantime, a lock current flows through the arm motor 84 and is detected by the lock current detector l88 to interrupt the CPU l90, thus starting the interrupt processing shown in Fig. ll. In other words, the process proceeds from Step 300 to Step 306, in which the arm motor 84 is turned OFF, and the process then returns. When no rain signal is received within 30 seconds, the process proceeds from Step 254 to Steps 262 and 250, and the above-­ described processing is repeated with the wiper assembly l0 maintained in the position shown in Fig. 2(A). When a rain signal is received in Step 252, Steps 256, 2l8 and 220 are executed, and the processing of Steps 232 to 258 is then repeated in the same way as the above. Thus, in the AUTO mode, when there is no rain, the wiper assembly l0 stands by in the position shown in Fig. 2(A), whereas, when it begins to rain, the second arm 56 is stretched, and the wiper blade 54 is reciprocated. When the rain has stopped, the second arm 56 is bent, and the wiper assembly l0 stands by in the position shown in Fig. 2(A) so as to immediately cope with a rainy situation. Accordingly, the AUTO mode is extremely convenient in the case of an intermittent rain. In the case where the wiper assembly l0 is in the position shown in Fi9. 2(A), if the ignition switch is turned OFF and then turned ON and the wiper mode changeover switch l56 is set to the AUTO, Lo or Hi mode, the processing of Steps 200, 268, 270 and 272 is executed, and the process then proceeds to Step 2l6, form which the processing corresponding to each of the above-described modes is executed. In other words, even when the power supply is turned OFF, the operation which is to be conducted subsequently can infallibly be executed when the power supply is turned ON again. Similarly, when the louver open limit switch l60 is ON but the pop-up limit switch l64 is OFF, Steps 200 and 268 are executed, and the process then proceeds to Step 206. When both the louver open limit switch l60 and the pop-up limit switch l64 are ON but the wiper arm turning position X limit switch l74 is OFF, Steps 200, 268 and 270 are executed, and the process then proceeds to Step 2l0. When all the louver open limit switch l60, the pop-up limit switch l64, the arm expansion limit switch l68 and the wiper arm turning position X limit switch l74 are ON, Steps 200, 268, 270, 272 and 274 are executed, and when the present operation mode is the AUTO mode, the process proceeds to Step 250, whereas, when the mode is either the Lo or Hi mode, the process proceeds from Step 274 to Step 232. Thus, the state before the power supply is turned OFF can be known after the power supply has been turned ON again, so that it is possible to exactly execute the operation which is to be conducted subsequently. Fig. l2 is a control flowchart showing the operation which is executed when the wiper mode changeover switch l56 is switched over from AUTO, Lo or Hi mode to the OFF position. When the switch l56 is switched over to the OFF position while the wiper motor l06 is being rotated forward or backward, the process proceeds from Step 400 to Step 408. When either the wiper arm turning position Y limit switch l76 or the wiper arm turning position X limit switch l74 turns ON, the process proceeds from Step 408 to Step 4l0, wherein the wiper motor l06 is turned OFF. In consequence, the wiper assembly l0 is in the position shown in Fig. 2(B). The process then proceeds to Step 4l2, in which the arm motor 84 is rotated in the direction in which the second arm 56 is bent. When the arm contraction limit switch l70 turns ON in Step 4l4, the process proceeds to Step 4l5. When the wiper arm turning position Y limit switch l76 is ON, the wiper motor l06 is rotated forward in Step 4l6, whereas, when the wiper arm turning position X limit switch l74 is ON, the wiper motor l06 is rotated backward in Step 4l8. The process then proceeds to Step 420 and stays there until the wiper arm accommodated position limit switch l72 turns ON. Meantime, a lock current flows through the arm motor 84 and is detected by the lock current detector l88 to interrupt the CPU l90, thus starting the interrupt processing shown in Fig. ll. In other words, the process proceeds to Steps 300 and 306, and the arm motor 84 is turned OFF in Step 306, and the process then returns to Step 420. When the wiper arm accommodated position limit switch l72 turns ON, the process proceeds to Step 422, in which the wiper motor l06 is turned OFF. In consequence, the wiper assembly l0 is brought to the position shown in Fig. l. Then, the pop-up motor 44 is rotated in the direction in which the wiper assembly l0 is moved downward in Step 424. When the pop-down limit switch l66 turns ON in Step 426, the process proceeds to Step 427, in which the pop-up motor 44 is turned OFF. Then, the louver motor 34 is rotated in the direction in which the louver 28 closes the opening 29 in Step 428, thus completing the processing shown in Fig. l2. Thereafter, a lock current flows through the louver motor 34 and is detected by the lock current detector l84 to start the interrupt processing shown in Fig. ll. Namely, the process proceeds to Steps 300 and 302, and the louver motor 34 is turned OFF in Step 302, and the process returns to the main routine. Thus, the wiper assembly l0 is brought to the position shown in Fig. 3(A). Accordingly, the front glass l2, the louver 28 and the hood l4 are flattened so that their respective surfaces are flush with each other, thereby enabling the air resistance to be minimized. In addition, since any part of the wiper assembly l0 projects from the outer suface of the vehicle body, there is no fear of the wiper assembly l0 being subjected to any undesirable external force which may be applied from a car cover, a car washing machine or the like. In the AUTO mode, if the wiper mode changeover switch l56 is turned OFF while the wiper assembly l0 is standing by in the position shown in Fig 2(A), Steps 400, 436 and 438 are executed, and the process then proceeds to Step 4l5, from which the above-described processing is executed. Similarly, when the wiper mode changeover switch l56 is turned OFF while the wiper assembly l0 is in the position shown in Fig. 2(B), Steps 400 and 436 are executed, and the process then proceeds to Step 4l2. When the wiper mode changeover switch l56 is turned OFF while the wiper assembly l0 is in the position shown in Fig. l, Steps 400, 436, 438 and 440 are executed, and the process then proceeds to Step 424. When the switch l56 is turned OFF in the state where the wiper assembly l0 is in the position shown in Fig. 3(A) and the louver 28 is in the position shown by the two-dot chain line, Steps 400, 436, 438, 440 and 442 are executed, and the process then proceeds to Step 428. When the switch l56 is turned OFF in the state wherein the wiper assembly l0 is in the position shown in Fig. 3(A) and the louver 28 is in the solid line position, Steps 400, 436, 438, 440 and 442 are executed, and the processing is ended without activating any motor. Thus, when the wiper mode changeover switch l56 is turned OFF also, the state before the power supply is turned OFF can exactly be known and the processing which is to be executed thereafter can infallibly be carried out without the need to back up the RAM l94 by means of a battery in the same manner as that in the case where the switch l56 is switched over to the AUTO, Lo or Hi mode. Referring next to Fig. l3, there is shown a flowchart which generally shows the operation of controlling the washer. The washer control operation will first be explained which is executed when the washer switch l58 is turned ON in the state wherein the wiper mode changeover switch l56 is set in either the Lo or Hi mode. When Steps 200 to 220 have not yet been executed, the processing of these Steps is executed in Step 500, and the process then proceeds to Steps 502 and 504, and the washer motor l82 is turned ON to apply washing water to the surface of the front glass l2 in Step 504. Then, when the washer switch l58 is turned OFF in Step 506, the washer motor l82 is turned OFF in Step 508, thus completing the processing. The following is a description of the washer control operation which is executed when the washer switch l58 is turned ON in the case where the wiper mode changeover switch l56 is set in the AUTO mode. When Steps 200 to 220 have not yet been executed, the processing of these Steps is completed in Step 500. It should be noted that, in this case, the process proceeds from Step 2l4 to Step 2l8. Then, the process proceeds to Steps 502, 5l0 and 5l2, and the washer motor l82 is activated for two seconds in Step 5l0. At the same time, the processing of Steps 232 to 242 is repeated twice. In other words, the wiper blade 54 is made to reciprocate four times. The time required for the wiper blade 54 to reciprocate four times is about five seconds. The process then proceeds from Step 5l4 to Step 250 to execute the processing in the AUTO mode. When the washer switch l58 is turned ON in the case where the wiper mode changeover switch l56 is OFF, Steps 500, 502, 5l0 and 5l2 are first executed in the same manner as that in the case of the AUTO mode. Then, Steps 5l4, 5l6 are executed, and the process proceeds to Step 4l2 to carry out the processing which is executed in the case where the wiper mode changeover switch l56 is turned OFF. In other words, the second arm 56 is folded, and the wiper assembly l0 is brought to the position shown in Fig. 3(A). When, in the AUTO mode, the washer switch l58 is turned ON and the wiper mode changeover switch l56 is turned OFF before the processing of Step 5l2 is completed, Steps 5l4 and 5l6 are executed, and the process proceeds to Step 4l2. When the washer switch l58 is turned ON while the wiper mode changeover switch l56 is OFF and the wiper mode changeover switch l56 is then switched over to the AUTO mode before the processing of Step 5l2 is completed, the process shifts from Step 5l4 to Step 250 in the same manner as that in the case where the wiper mode changeover switch l56 has been set in the AUTO mode from the first. It should be noted that the rise-up and stretching of the wiper arm may be simultaneously effected. A second embodiment of the present invention will be explained below with reference to Fig. l4. In Fig. l4, the same members and portions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Referring to Fig. l4, which corresponds to Fig. 8(B), a bevel gear l20 is rigidly secured to the upper end of the arm stretching driving shaft 72 by means of a nut l22. Accordingly, the bevel gear l20 is coaxial with the worm wheel 78 and rotates together with it one unit. A shaft l24 is provided in such a manner as to extend in the longitudinal direction of the first arm 58, and both end portions of the shaft l24 are rotatably supported by bearings l26 and l28, respectively. The bearings l26 and l28 are disposed in coaxial relation to each other and are rigidly secured to the first arm 58. A bevel gear l30 is rigidly secured to one end of the shaft l24, and meshed with the bevel gear l20 so that the rotational force from the arm stretching driving shaft 72 is transmitted to the shaft l24. Similarly, a bevel gear l32 is rigidly secured to the other end of the shaft l24, and meshed with a bevel gear l36 which is rigidly secured to the arm stretching shaft 60 so that the rotational force from the shaft l24 is transmitted to the arm stretching shaft 60. One end of the arm stretching shaft 60 is rotatably supported by an angular contact ball bearing l34 which is rigidly secured to the first arm 58. The other end of the arm stretching shaft 60 is rigidly secured to the second arm 56 by means of a nut 6l. Accordingly, as the worm 80 is rotated by the arm stretching motor 84, the rotational force from the worm 80 is sequentially transmitted to the worm wheel 78, the arm stretching driving shaft 72, the bevel gears l20, l30, the shaft l24, the bevel gears l32, l36, the arm stretching shaft 60 and the second arm 56, thus causing the second arm 56 to be bent or stretched relative to the first arm 58 in accordance with the rotational direction of the arm stretching motor 84. In consequence, the overall length of the first and second arms 58 and 56 is selectively expanded and contracted. A third embodiment of the present invention will next be explained with reference to Fig. l5. Referring to Fig. l5, which corresponds to Fig. 8(B), a pulley l38 is rigidly secured to the upper end of the arm stretching driving shaft 72 by means of a nut l40. Accordingly, the pulley l38 is coaxial with the worm wheel 78 and rotates together with it in one unit. One end of the arm stretching shaft 60 is rigidly secured to the second arm 56 by means of a nut 6l, while the other end thereof is rotatably supported by the first arm 58. A pulley l42 is rigidly secured to the intermediate portion of the arm stretching shaft 60. A synchronizing rubber belt l44 is stretched between the pulleys l38 and l42. As shown in Fig. l6, teeth l46 are formed on the inner surface of the belt l44, and meshed with teeth which are formed on each of the pulleys l38 and l42, thereby preventing slippage between the belt l44 and the pulleys l38 and l42. Glass fibers l48 are buried in the rubber belt l44 along the longitudinal direction thereof to reinforce the belt l44. It should be noted that a wire or a chain may be employed in place of the rubber belt l44.

Claims: 1. A stretchable wiper apparatus for a vehicle in which a window glass of the vehicle is wiped by a wiper blade, characterized by comprising: a first arm secured to a wiper arm pivoting shaft and pivoted within a predetermined angle about said shaft; a second arm secured at one end portion thereof to the wiper blade which is pressed against the surface of the window glass to wipe the window glass surface, the other end portion of said second arm being pivotally supported by said first arm; and stretching means for expanding and contracting the overall length of said first and second arms. 2. A stretchable wiper apparatus according to Claim l, wherein said stretching means includes a stretching meachanism for bending and stretching said second arm relative to said first arm, and an actuator for activating said stretching mechanism. 3. A stretchable wiper apparatus according to Claim 2, wherein said stretching mechanism includes a pinion rigidly secured to the second end portion of said second arm, and a rack which is incorporated in said first arm and meshed with said pinion, so that said second arm is bent and stretched relative to said first arm by the linear motion of said rack through said pinion. 4. A stretchable wiper apparatus according to Claim 3, wherein said rack is formed on one end portion of a rod incorporated in said first arm. 5. A stretchable wiper apparatus according to Claim 4, wherein said stretching mechanism further includes a crank arm operatively connected to the other end of said rod so that said rod is linearly moved by the rotation of said crank arm, and an arm stretching driving shaft which is rigidly secured to said crank arm to rotate said crank arm. 6. A stretchable wiper apparatus according to Claim 5, wherein said arm stretching driving shaft axially extends through said wiper arm pivoting shaft, said crank arm being supported by one end portion of said arm stretching driving shaft, and said actuator being supported by said wiper arm pivoting shaft so as to activate said stretching mechanism through the other end portion of said arm stretching driving shaft. 7. A stretchable wiper apparatus according to Claim 6, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 8. A stretchable wiper apparatus according to Claim 2, wherein said stretching mechanism includes: a first bevel gear rigidly secured to the second end portion of said second arm; a shaft incorporated in said first arm and having a second bevel gear which is rigidly secured to one end portion thereof and which is meshed with said first bevel gear, said shaft further having a third bevel gear rigidly secured to the other end portion thereof; a fourth bevel gear meshed with said third bevel gear; and an arm stretching driving shaft having said fourth bevel gear rigidly secured thereto. 9. A stretchable wiper apparatus according to Claim 8, wherein said arm stretching driving shaft is disposed in such a manner as to extend axially through said wiper arm pivoting shaft, said fourth bevel gear being rigidly secured to one end portion of said arm stretching driving shaft, and said actuator being connected to the other end portion of said arm stretching driving shaft so as to rotate said arm stretching driving shaft. l0. A stretchable wiper apparatus according to Claim 9, wherein said actuator is an arm stretching motor, said arm stretching shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 11. A stretchable wiper apparatus according to Claim 2, wherein said stretching mechanism includes a first pulley rigidly secured to said second arm, an arm stretching driving shaft extending through said wiper arm pivoting shaft, a second pulley rigidly secured to one end portion of said arm stretching driving shaft, and a synchronizing belt stretched between said first and second pulleys. 12. A stretchable wiper apparatus according to Claim ll, wherein said second pulley is rigidly secured to one end portion of said arm stretching driving shaft, said actuator being connected to the other end portion of said arm stretching driving shaft. 13. A stretchable wiper apparatus according to Claim l2, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 14. A stretchable wiper apparatus according to Claim l3, wherein each of said first and second pulleys has teeth formed on the outer peripheral portion thereof, said synchronizing belt being provided on the inner periphery thereof with teeth which are meshed with said teeth. 15. A stretchable wiper apparatus according to Claim l4, wherein said synchronizing belt having a glass fiber buried therein along the longitudinal direction thereof. 16. A stretchable wiper apparatus for a vehicle in which a window glass of the vehicle is wiped by a wiper blade, characterized by comprising: a first arm secured to a wiper arm pivoting shaft and pivoted within a predetermined angle about said shaft; a second arm secured at one end portion thereof to the wiper blade which is pressed against the surface of the window glass to wipe the window glass surface, the other end portion of said second arm being supported by said first arm; a stretching mechanism for bending and stretching said second arm relative to said first arm; and an actuator for activating said stretching mechanism, said actuator being rigidly secured to said wiper arm pivoting shaft in such a manner that said actuator is positioned on the side of said wiper arm pivoting shaft which is remote from the center of gravity of the assembly of said first and second arms and said wiper blade. 17. A stretchable wiper apparatus according to Claim l6, wherein said first arm is rigidly secured to one end portion of said wiper arm pivoting shaft, said actuator being disposed at the other end portion of said wiper arm pivoting shaft. 18. A stretchable wiper apparatus according to Claim l7, wherein said stretching mechanism includes a pinion rigidly secured to the second end portion of said second arm, and a rack disposed on said first arm and meshed with said pinion, so that said pinion is rotated by the linear motion of said rack, thereby allowing the overall length of said first and second arms to be selectively expanded and contracted. 19. A stretchable wiper apparatus according to Claim l8, wherein said rack is formed on one end portion of a rod incorporated in said first arm. 20. A stretchable wiper apparatus according to Claim l9, wherein said stretching mechanism further includes a crank arm operatively connected to the other end of said rod so that said rod is linearly moved by the rotation of said crank arm, and an arm stretching driving shaft which is rigidly secured to said crank arm to rotate said crank arm. 2l. A stretchable wiper apparatus according to Claim 20, wherein said crank arm is supported by one end portion of said arm stretching driving shaft, said actuator being adapted to activate said stretching mechanism through the other end portion of said arm stretching driving shaft. 22. A stretchable wiper apparatus according to Claim 2l, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 23. A stretchable wiper apparatus according to Claim l6, wherein said stretching mechanism includes: a first bevel gear rigidly secured to the second end portion of said second arm; a shaft incorporated in said first arm and having a second bevel gear which is rigidly secured to one end portion thereof and which is meshed with said first bevel gear, said shaft further having a third bevel gear rigidly secured to the other end portion thereof; a fourth bevel gear meshed with said third bevel gear; and an arm stretching driving shaft having said fourth bevel gear rigidly secured thereto. 24. A stretchable wiper apparatus according to Claim 23, wherein said fourth bevel gear is supported by one end portion of said arm stretching driving shaft, said actuator being adapted to activate said stretching mechanism through the other end portion of said arm stretching driving shaft. 25. A stretchable wiper apparatus according to Claim 24, wherein said actuator is an arm stretching motor, said arm stretching shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 26. A stretchable wiper apparatus according to Claim l6, wherein said stretching mechanism includes a first pulley rigidly secured to said second arm, an arm stretching driving shaft extending through said wiper arm pivoting shaft, a second pulley rigidly secured to one end portion of said arm stretching driving shaft, and a synchronizing belt stretched between said first and second pulleys. 27. A stretchable wiper apparatus according to Claim 26, wherein said second pulley is rigidly secured to one end portion of said arm stretching driving shaft, said actuator being connected to the other end portion of said arm stretching driving shaft. 28. A stretchable wiper apparatus according to Claim 27, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 29. A stretchable wiper apparatus according to Claim 28, wherein each of said first and second pulleys has teeth formed on the outer peripheral portion thereof, said synchronizing belt being provided on the inner periphery thereof with teeth which are meshed with said teeth. 30. A stretchable wiper apparatus according to Claim 29, wherein said synchronizing belt having a glass fiber buried therein along the longitudinal direction thereof. 3l. A stretchable wiper apparatus for a vehicle in which a window glass of the vehicle is wiped by a wiper blade, characterized by comprising: a first arm supported by a wiper arm pivoting shaft and pivoted within a predetermined angle about said shaft; a second arm secured at one end portion thereof to the wiper blade which is pressed against the surface of the window glass to wipe the window glass surface, the other end portion of said second arm being supported by said first arm; a stretching mechanism for bending and stretching said second arm relative to said first arm; an actuator for activating said stretching mechanism so as to bend and stretch said second arm relative to said first arm; and biasing means for biasing said wiper blade in the direction in which it is pressed against said glass surface, said biasing means having one end portion thereof secured to said second arm and the other end portion thereof secured at a position on said first arm which is in the vicinity of a pivot point of said first arm and at which, when said second arm is stretched relative to said first arm, the biasing force from said biasing means is increased, whereas, when said second arm is bent relative to said first arm, said biasing force is decreased. 32. A stretchable wiper apparatus according to Claim 3l, wherein said biasing means is a resilient member adapted such that, when said second arm is stretched relative to said first arm, the biasing force of said resilient member is increased, whereas, when said second arm is bent relative to said first arm, the resilience of said resilient member is decreased. 33. A stretchable wiper apparatus according to Claim 32, wherein said resilient member is a tension coil spring, one end portion of said spring being retained by said second arm, and the other end portion of said spring being retained at a position on said first arm which is in the vicinity of a pivot point of said first arm and which is closer to said wiper arm pivoting shaft than said pivot point. 34. A stretchable wiper apparatus according to Claim 32, wherein said resilient member is a compression coil spring, one end portion of said spring being supported by said second arm, and the other end portion of said spring being supported at a position on said first arm which is in the vicinity of a pivot point of said first arm and which is closer to said wiper blade than said pivot point when said second arm is stretched. 35. A stretchable wiper apparatus for a vehicle which is employed in a wiper system so designed that, when a wiper assembly is not used, it is accommodated in an accommodating chamber provided inside the body of the vehicle and in the vicinity of a window glass, whereas, when said wiper assembly is to be used, it is raised from said accommodating chamber to wipe the surface of said window glass, characterized in that said wiper assembly comprises: a first arm supported by a wiper arm pivoting shaft and pivoted within a predetermined angle about said shaft; a second arm secured at one end portion thereof to a wiper blade which is pressed against the surface of said window glass to wipe said glass surface, the other end portion of said second arm being pivotally supported by said first arm; and stretching means for expanding and contracting the overall length of said first and second arms. 36. A stretchable wiper apparatus according to Claim 35, wherein said stretching means includes a stretching mechanism for bending and stretching said second arm relative to said first arm, and an actuator for activating said stretching mechanism. 37. A stretchable wiper apparatus according to Claim 36, wherein said stretching mechanism includes a pinion rigidly secured to the second end portion of said second arm, and a rack which is incorporated in said first arm and meshed with said pinion, so that said second arm is bent and stretched relative to said first arm by the linear motion of said rack through said pinion. 38. A stretchable wiper apparatus according to Claim 37, wherein said rack is formed on one end portion of a rod incorporated in said first arm. 39. A stretchable wiper apparatus according to Claim 38, wherein said stretching mechanism further includes a crank arm operatively connected to the other end of said rod so that said rod is linearly moved by the rotation of said crank arm, and an arm stretching driving shaft which is rigidly secured to said crank arm to rotate said crank arm. 40. A stretchable wiper apparatus according to Claim 39, wherein said arm stretching driving shaft axially extends through said wiper arm pivoting shaft, said crank arm being supported by one end portion of said arm stretching driving shaft, and said actuator being supported by said wiper arm pivoting shaft so as to activate said stretching mechanism through the other end portion of said arm stretching driving shaft. 4l. A stretchable wiper apparatus according to Claim 40, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 42. A stretchable wiper apparatus according to Claim 36, wherein said stretching mechanism includes: a first bevel gear rigidly secured to the second end portion of said second arm; a shaft incorporated in said first arm and having a second bevel gear which is rigidly secured to one end portion thereof and which is meshed with said first bevel gear, said shaft further having a third bevel gear rigidly secured to the other end portion thereof; a fourth bevel gear meshed with said third bevel gear; and an arm stretching driving shaft having said fourth bevel gear rigidly secured thereto. 43. A stretchable wiper apparatus according to Claim 42, wherein said arm stretching driving shaft is disposed in such a manner as to extend axially through said wiper arm pivoting shaft, said fourth bevel gear being rigidly secured to one end portion of said arm stretching driving shaft, and said actuator being connected to the other end portion of said arm stretching driving shaft so as to rotate said arm stretching driving shaft. 44. A stretchable wiper apparatus according to Claim 43, wherein said actuator is an arm stretching motor, said arm stretching shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 45. A stretchable wiper apparatus according to Claim 36, wherein said stretching mechanism includes a first pulley rigidly secured to said second arm, an arm stretching driving shaft extending through said wiper arm pivoting shaft, a second pulley rigidly secured to one end portion of said arm stretching driving shaft, and a synchronizing belt stretched between said first and second pulleys. 46. A stretchable wiper apparatus according to Claim 45, wherein said second pulley is rigidly secured to one end portion of said arm stretching driving shaft, said actuator being connected to the other end portion of said arm stretching driving shaft. 47. A stretchable wiper apparatus according to Claim 46, wherein said actuator is an arm stretching motor, said arm stretching driving shaft and said arm stretching motor being connected through a worm wheel rigidly secured to the second end of said arm stretching driving shaft and a worm which is rigidly secured to a rotating shaft of said arm stretching motor and meshed with said worm wheel. 48. A stretchable wiper apparatus according to Claim 36, wherein said actuator is rigidly secured to said wiper arm pivoting shaft in such a manner that said actuator is positioned on the side of said wiper arm pivoting shaft which is remote from the center of gravity of the assembly of said first and second arms and said wiper blade. 49. A stretchable wiper apparatus according to Claim 48, wherein said first arm is rigidly secured to one end portion of said wiper arm pivoting shaft, said actuator being disposed at the other end portion of said wiper arm pivoting shaft. 50. A stretchable wiper apparatus according to Claim 49, wherein said stretching mechanism includes a pinion rigidly secured to the second end portion of said second arm, and a rack disposed on said first arm and meshed with said pinion, so that said pinion is rotated by the linear motion of said rack, thereby allowing the overall length of said first and second arms to be selectively expanded and contracted. 5l. A stretchable wiper apparatus according to Claim 36, further comprising: biasing means for biasing said wiper blade in the direction in which it is pressed against said glass surface, said biasing means having one end portion thereof secured to said second arm and the other end portion thereof secured at a position on said first arm which is in the vicinity of a pivot point of said first arm and at which, when said second arm is stretched relative to said first arm, the biasing force from said biasing means is increased, whereas, when said second arm is bent relative to said first arm, said biasing force is decreased. 52. A stretchable wiper apparatus according to Claim 5l, wherein said biasing means is a resilient member adapted such that, when said second arm is stretched relative to said first arm, the biasing force of said resilient member is increased, whereas, when said second arm is bent relative to said first arm, the resilience of said resilient member is decreased. 53. A stretchable wiper apparatus according to Claim 52, wherein said resilient member is a tension coil spring, one end portion of said spring being retained by said second arm, and the other end portion of said spring being retained at a position on said first arm which is in the vicinity of a pivot point of said first arm and which is closer to said wiper arm pivoting shaft than said pivot point. 54. A stretchable wiper apparatus according to Claim 52, wherein said resilient member is a compression coil spring, one end portion of said spring being supported by said second arm, and the other end portion of said spring being supported at a position on said first arm which is in the vicinity of a pivot point of said first arm and which is closer to said wiper blade than said pivot point when said second arm is stretched. 55. A stretchable wiper apparatus according to Claim 36, further comprising: control means adapted to effect control such that, after said wiper assembly has been raised from said accommodting chamber, said first arm is turned until it reaches a pivoting start position, and said second arm is then stretched relative to said first arm so that said first and second arms extend in a substantially straight line.

Inventors: 1SOUDA, IKUO, HIROSAWA, YASUNORI, HONDA, YUKIO, KONDO, OSAMU, OKUDAIRA, SOUICHIRO
Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1986
Main classification: B60S1
IPC codes: B60S1