Wiping device

Abstract

To provide a wiping device that can reduce the risk of interference between the wiper blade and other components. [Solution] A wiping device that causes a wiper blade to reciprocate by driving a power source with a predetermined drive signal, and corrects the reversal position of the wiper blade by changing the drive signal according to the wind pressure acting on the wiper blade, comprising a power source drive unit that acquires a first wind pressure estimate value based on the drive signal and a second wind pressure estimate value based on the vehicle speed, corrects the reversal position based on the first wind pressure estimate value if the first wind pressure estimate value is greater than the second wind pressure estimate value, and corrects the reversal position based on the second wind pressure estimate value if the first wind pressure estimate value is less than or equal to the second wind pressure estimate value.

Description

Technical Field

[0001] The present invention relates to a wiping device.

Background Art

[0002] As is well known, various vehicles are equipped with a wiping device that wipes rainwater off the surface of a windshield or rear window (the surface to be wiped). This wiping device wipes rainwater on the surface to be wiped by causing a wiper blade to reciprocate via a motor (a power source). As an example of such a wiping device, Patent Document 1 below discloses a window wiping device that uniformly wipes the surface to be wiped by changing a motor control signal in accordance with a wind load obtained from vehicle speed and / or wiping speed.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] By the way, the technology of changing the motor control signal in accordance with vehicle speed cannot address the influence of crosswind (headwind or tailwind acting on the wiper blade). That is, in the technology of changing the control signal in accordance with vehicle speed, for example, when a wiper blade receives a tailwind, the overrun of the wiper blade increases, and as a result, the wiper blade may interfere with other members such as a pillar of a vehicle.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wiping device capable of reducing the risk of interference between a wiper blade and other members.

Means for Solving the Problem

[0006] To achieve the above objective, the present invention provides a first solution relating to a wiping device, which reciprocates a wiper blade by driving a power source with a predetermined drive signal, and corrects the reversal position of the wiper blade by changing the drive signal according to the wind pressure acting on the wiper blade, wherein the device acquires a first wind pressure estimate based on the drive signal and a second wind pressure estimate based on the vehicle speed, and if the first wind pressure estimate is greater than the second wind pressure estimate, it corrects the reversal position based on the first wind pressure estimate, and if the first wind pressure estimate is less than or equal to the second wind pressure estimate, it corrects the reversal position based on the second wind pressure estimate.

[0007] In the present invention, as a second solution relating to the wiping device, in the first solution described above, the drive signal is a PWM (Pulse Wide Modulation) signal, and the power source drive unit acquires the first wind pressure estimate based on the duty cycle of the PWM signal.

[0008] In the present invention, as a third solution relating to the wiping device, the method adopted is that, in the second solution described above, the duty cycle is the average value over a predetermined period of the forward or return stroke of the wiper blade.

[0009] In the present invention, as a fourth solution relating to the wiping device, in any of the first to third solutions described above, one or two power sources are provided, and one power source is used to reciprocate one or two wiper blades, while two power sources are used to individually reciprocate two wiper blades. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a wiping device that can reduce the risk of interference between the wiper blade and other components. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the functional configuration of the wiping device A according to the first embodiment of the present invention. [Figure 2] This is a flowchart showing the operation of the wiping device A according to the first embodiment of the present invention. [Figure 3] This is a characteristic diagram showing the change in the correction criterion for the inversion position in the first embodiment of the present invention. [Figure 4] This is a block diagram showing the functional configuration of the wiping device B according to the second embodiment of the present invention. [Modes for carrying out the invention]

[0012] [First Embodiment] A first embodiment of the present invention will be described with reference to Figures 1 to 3. The wiping device A according to the first embodiment is a device that is mounted on various vehicles such as gasoline automobiles, hybrid automobiles, or electric automobiles, and wipes away rainwater adhering to the surface (surface to be wiped) of a member to be wiped, such as a windshield or rear window.

[0013] As shown in Figure 1, this wiping device A employs a two-motor drive system in which a pair of wiper blades 1a and 1b are individually driven by a pair of motors 7a and 7b, which are power sources. In other words, the wiping device A according to the first embodiment is provided with two power sources, and these two power sources individually reciprocate the pair of wiper blades 1a and 1b.

[0014] As shown in the figure, this wiping device A comprises a pair of wiper blades 1a and 1b and a single drive unit 10. In Figure 1, "a" indicates a component or part located on or related to the driver's side of the vehicle. In Figure 1, "b" indicates a component or part located on or related to the passenger side of the vehicle.

[0015] As shown in the figure, the pair of wiper blades 1a and 1b are rod-shaped members placed on the windshield W (the object to be wiped). The pair of wiper blades 1a and 1b are in contact with the surface of the windshield W (the surface to be wiped) and wipe away rainwater adhering to the surface by reciprocating motion (oscillating motion) over the surface to be wiped. In Figure 1, the symbol Ra represents the wiping range of the wiper blade 1a on the driver's side, and the symbol Rb represents the wiping range of the wiper blade 1b on the passenger side.

[0016] The wiping range Ra on the driver's side extends from the lower inversion position to the upper inversion position of the wiper blade 1a, and is the range of movement of the wiper blade 1a with the driver's side wiper shaft 3a as the pivot point. In contrast, the wiping range Rb on the passenger side extends from the lower inversion position to the upper inversion position of the wiper blade 1b, and is the range of movement of the wiper blade 1b with the passenger side wiper shaft 3b as the pivot point.

[0017] The pair of wiper blades 1a and 1b stop for a predetermined period of time at the lower inversion position and the upper inversion position during their reciprocating motion within the wiping ranges Ra and Rb. Specifically, when the pair of wiper blades 1a and 1b move from the lower inversion position towards the upper inversion position, they stop briefly at the upper inversion position for a predetermined stopping period T, and after this stopping period T has elapsed, they move from the upper inversion position towards the lower inversion position.

[0018] The pair of wiper blades 1a and 1b are driven by the drive unit 10 to perform a reciprocating motion over the wiping ranges Ra and Rb, and the lower and upper reversal positions are set by the drive unit 10. As will be described in detail later, the lower and upper reversal positions are corrected according to the vehicle speed (movement speed) or the drive signals of the pair of motors that drive the pair of wiper blades 1a and 1b, respectively.

[0019] The pair of wiper blades 1a, 1b are mechanically connected to the driving device 10 via a pair of wiper arms 2a, 2b. That is, the driver's seat side wiper blade 1a is connected to the driving device 10 via the wiper arm 2a provided on the driver's seat side. The passenger seat side wiper blade 1b is connected to the driving device 10 via the wiper arm 2b provided on the passenger seat side.

[0020] The pair of wiper arms 2a, 2b are rod-shaped members as illustrated, one end of each is connected to an intermediate portion of the pair of wiper blades 1a, 1b, and the other end is connected to the pair of wiper shafts 3a, 3b. That is, one end of the driver's seat side wiper arm 2a is connected to an intermediate portion of the driver's seat side wiper blade 1a, and the other end is connected to the driver's seat side wiper shaft 3a.

[0021] On the other hand, one end of the passenger seat side wiper arm 2b is connected to an intermediate portion of the passenger seat side wiper blade 1b, and the other end is connected to the passenger seat side wiper shaft 3b. It should be noted that such a pair of wiper arms 2a, 2b are members included in the constituent elements of the pair of wiper blades 1a, 1b.

[0022] The pair of wiper arms 2a, 2b function as power transmission components that mechanically transmit the rotational power of the driving device 10 to the pair of wiper blades 1a, 1b. Furthermore, the pair of wiper arms 2a, 2b function as biasing members that press the pair of wiper blades 1a, 1b against the surface (wiped surface) of the windshield W with a predetermined pressing force.

[0023] The driving device 10 is a power generating device that causes the pair of wiper blades 1a, 1b to perform reciprocating motion via the pair of wiper arms 2a, 2b. This driving device 10 rotates the pair of wiper shafts 3a, 3b within a predetermined angular range, thereby causing the pair of wiper blades 1a, 1b placed on the surface (wiped surface) of the windshield W to perform reciprocating motion.

[0024] The drive unit 10 includes a pair of motors 7a and 7b as power sources corresponding to a pair of wiper shafts 3a and 3b. Each of the motors 7a and 7b includes a motor body 8 and a reduction mechanism 9. The drive unit 10 also includes a pair of wiper control units 10a and 10b corresponding to the pair of motors 7a and 7b (power sources).

[0025] The pair of wiper control units 10a and 10b are drive units that drive the pair of motors 7a and 7b (power sources). The wiper control unit 10a drives the motor 7a on the driver's side to cause the wiper blade 1a on the driver's side to reciprocate on the surface to be wiped. The wiper control unit 10b drives the motor 7b on the passenger's side to cause the wiper blade 1b on the passenger's side to reciprocate on the surface to be wiped.

[0026] The wiper control unit 10a, which corresponds to the driver's side, includes a CPU (Central Processing Unit) 21a, a communication circuit 22a, a ROM (Read Only Memory) 23a, a RAM (Random Access Memory) 24a, an angle detection circuit 31a, a drive circuit 32a, and a lock detection timer 33a. The wiper control unit 10b, which corresponds to the passenger side, includes a CPU 21b, a communication circuit 22b, a ROM 23b, a RAM 24b, an angle detection circuit 31b, a drive circuit 32b, and a lock detection timer 33b.

[0027] These wiper control units 10a and 10b are connected via a pair of communication circuits 22a and 22b, allowing for seamless communication. Furthermore, one of the wiper control units 10a is connected to the vehicle's higher-level control unit, the ECU, via a communication line. The ECU inputs switch signals such as ON / OFF for the wiper switch, ON / OFF for the mist switch, and intermittent operation (Lo, Hi, INT), as well as a vehicle speed signal indicating the vehicle's speed V.

[0028] The drive unit 10 sets the movement position of a pair of wiper blades 1a and 1b by feedback-controlling a pair of motors 7a and 7b based on the elapsed movement time from an absolute position that serves as a control reference. In this position control, for example, the downward inversion position is used as the absolute position. In the drive unit 10, the target rotational speed TR of the pair of motors 7a and 7b at each point in time is preset as an operation map, corresponding to the elapsed movement time t from the downward inversion position (reference position).

[0029] A pair of wiper control units 10a and 10b measure the elapsed time t from the lower inversion position (reference position) in a pair of CPUs 21a and 21b, and determine the current rotational speed of a pair of motors 7a and 7b. They then compare the current rotational speed at elapsed time t with the target rotational speed TR on the operation map. The pair of CPUs 21a and 21b generate a pair of PWM (Pulse Wide Modulation) drive signals to drive the pair of motors 7a and 7b by feedback-controlling a pair of drive circuits 32a and 32b according to the difference between the current rotational speed and the target rotational speed TR.

[0030] In other words, the upward inversion position of the pair of wiper blades 1a and 1b is set based on a pair of control command values ​​output from a pair of CPUs 21a and 21b to a pair of drive circuits 32a and 32b, respectively, based on the difference between the current rotational speed and the target rotational speed TR. The pair of drive circuits 32a and 32b set the upward inversion position to a predetermined position by generating a pair of PWM drive signals that drive a pair of motors 7a and 7b based on the pair of control command values.

[0031] Furthermore, as shown in the figure, a pair of angle detection circuits 31a and 31b are provided between the pair of motors 7a and 7b and the pair of CPUs 21a and 21b to detect the position of the pair of wiper blades 1a and 1b. The pair of angle detection circuits 31a and 31b output relative position signals to the pair of CPUs 21a and 21b that are proportional to the rotation angles of the pair of motors 7a and 7b and indicate the amount of movement of the pair of wiper blades 1a and 1b.

[0032] Specifically, the angle detection circuit 31a corresponding to the driver's side is located between the motor 7a on the driver's side and the CPU 21a corresponding to the driver's side. This angle detection circuit 31a outputs a relative position signal to the CPU 21a that indicates the amount of movement of the wiper blade 1a on the driver's side, in proportion to the rotation angle of the motor 7a on the driver's side. In addition, this angle detection circuit 31a outputs an absolute position signal to the CPU 21a that indicates the position of the wiper blade on the driver's side.

[0033] On the other hand, the angle detection circuit 31b corresponding to the passenger side is installed between the motor 7b on the passenger side and the CPU 21b corresponding to the passenger side. This angle detection circuit 31b outputs a relative position signal to the CPU 21b that indicates the amount of movement of the passenger side wiper blade 1b, in proportion to the rotation angle of the motor 7b on the passenger side. This angle detection circuit 31b also outputs an absolute position signal to the CPU 21b that indicates the position of the passenger side wiper blade.

[0034] The relative position signal described above is a pulse signal (motor pulse) output from a pair of motors 7a and 7b in conjunction with the rotation of the pair of motors 7a and 7b. This relative position signal is a pulse signal with a number of pulses proportional to the rotation angle of the pair of motors 7a and 7b. The absolute position signal is a single pulse signal output from a pair of motors 7a and 7b when the pair of wiper blades 1a and 1b are in the downward inversion position (reference position).

[0035] The rotational speeds of the pair of motors 7a and 7b and the rotational speeds of the pair of wiper shafts 3a and 3b are in a constant relationship based on the reduction ratio of the reduction mechanism 9. The rotational angles of the pair of wiper shafts 3a and 3b are obtained by calculations performed by a pair of CPUs 21a and 2b based on the number of pulses of the relative position signal. Furthermore, the rotational angles of the pair of wiper shafts 3a and 3b and the movement angles of the pair of wiper blades 1a and 1b are in a constant relationship based on the reduction ratio mentioned above.

[0036] Specifically, the pair of CPUs 21a and 2b detect the movement angle of the pair of wiper blades 1a and 1b by integrating the number of pulses of the relative position signal. The pair of CPUs 21a and 21b obtain the current position of the pair of wiper blades 1a and 1b based on the result of integrating the number of pulses of the relative position signal and the absolute position signal. In addition, the pair of CPUs 21a and 21b detect the current rotational speed of the pair of motors 7a and 7b by counting the relative position signal (motor pulses).

[0037] Furthermore, the pair of CPUs 21a and 21b measure the elapsed time t from the time of acquisition of the absolute position signal using a built-in timer. In addition, the pair of CPUs 21a and 21b acquire the target positions of the pair of wiper blades 1a and 1b and the target rotational speed TR of the pair of motors 7a and 7b at the current elapsed time from ROMs 23a and 23b.

[0038] The pair of CPUs 21a and 21b compare the current position of the pair of wiper blades 1a and 1b with the target position to understand the current status of the pair of wiper blades 1a and 1b (the degree of lag or advance relative to the target position). The pair of CPUs 21a and 21b also calculate the rotational speed of the pair of motors 7a and 7b based on the status of the motors' rotational speed (high or low relative to the target rotational speed TR), and control the rotation of the pair of motors 7a and 7b based on that rotational speed.

[0039] In other words, the pair of ROMs 23a and 23b have pre-stored operation maps that use the elapsed time t from the time of acquisition of the absolute position signal as a parameter, with target values ​​for the positions of the pair of wiper blades 1a and 1b and the rotational speed of the pair of motors 7a and 7b. The pair of CPUs 21a and 21b provide feedback control to the pair of motors 7a and 7b by comparing the target rotational speed in these operation maps with the current value.

[0040] Furthermore, each operation map has a pre-set precedence relationship between a pair of wiper blades 1a and 1b. In addition, in each operation map, the target rotational speed TR is determined according to the position of the other wiper blade, based on the elapsed time t from the time of acquisition of the absolute position signal and the current positions of the pair of wiper blades 1a and 1b. For example, even if the elapsed time t and the current positions of the pair of wiper blades 1a and 1b are the same, the target rotational speed TR is set to be larger if the other wiper blade's current position is closer to itself, and smaller if the other wiper blade's current position is farther away.

[0041] The current positions of a pair of wiper blades 1a and 1b are exchanged between a pair of CPUs 21a and 21b via a pair of communication circuits 22a and 22b, and written to a pair of RAMs 24a and 24b, respectively. The pair of CPUs 21a and 21b generate a pair of PWM drive signals to drive a pair of motors 7a and 7b by synchronously controlling a pair of drive circuits 32a and 32b based on the positional relationship of the pair of wiper blades 1a and 1b written to the pair of RAMs 24a and 24b.

[0042] Here, the external force acting on the pair of wiper blades 1a and 1b is the wind pressure acting on the pair of wiper blades 1a and 1b. This wind pressure is a disturbance in the position control of the pair of wiper blades 1a and 1b by the drive unit 10.

[0043] This wind pressure is a physical quantity that has a certain correlation with the vehicle's speed (movement speed) and can be estimated (predicted) based on the vehicle's speed. Furthermore, this wind pressure can be estimated (predicted) based on the drive current of a pair of motors 7a and 7b, which are the power sources for a pair of wiper blades 1a and 1b.

[0044] The drive current of the pair of motors 7a and 7b is based on the duty cycle of the PWM drive signal supplied by the drive unit 10 to the pair of motors 7a and 7b. Therefore, the wind pressure can be estimated (predicted) based on the duty cycle of the PWM drive signal.

[0045] As will be described in more detail later, the pair of CPUs 21a and 21b in the drive unit 10 acquire an estimated wind pressure value E1 (first estimated wind pressure value) based on the vehicle speed and an estimated wind pressure value E2 (second estimated wind pressure value) based on the duty cycle of the PWM drive signal, in order to suppress fluctuations in the upright inversion position caused by the wind pressure. Furthermore, the pair of CPUs 21a and 21b stabilize the fluctuations in the upright inversion position by correcting the target rotational speed TR based on the estimated wind pressure value E1 or the estimated wind pressure value E2.

[0046] Next, the characteristic operation of the wiping device A according to the first embodiment, namely the correction process of the target rotational speed TR based on the vehicle speed and the duty cycle of the PWM drive signal, will be explained in accordance with the flowchart shown in Figure 2.

[0047] In this wiping device A, a pair of CPUs 21a and 21b acquire the vehicle speed by obtaining a switch signal and a vehicle speed signal at predetermined timings through communication with a higher-level control unit (ECU) (step S1). Then, the pair of CPUs 21a and 21b perform predetermined calculation processing on the vehicle speed to obtain an estimated value of the wind pressure acting on the pair of wiper blades 1a and 1b due to the vehicle speed, which is called the wind pressure estimate value E1 (step S2).

[0048] Next, the pair of CPUs 21a and 21b perform predetermined calculations on the duty cycle of the PWM drive signals generated by the pair of drive circuits 32a and 32b to obtain an estimated wind pressure value E2, which is the wind pressure value acting on the pair of wiper blades 1a and 1b due to the duty cycle (step S3).

[0049] Here, the duty cycle of the PWM drive signal is set by a control command output by a pair of CPUs 21a and 21b to a pair of drive circuits 32a and 32b. In other words, this control command specifies the duty cycle of the PWM drive signal to the pair of drive circuits 32a and 32b. Therefore, the pair of CPUs 21a and 21b calculate the wind pressure estimate E2 based on the control command they have acquired, i.e., the duty cycle of the PWM drive signal.

[0050] Furthermore, such wind pressure estimate E2 is calculated, for example, based on the average value of the duty cycle over a predetermined period during the forward or return journey of a pair of wiper blades 1a and 1b. That is, a pair of CPUs 21a and 21b calculate the average value of the duty cycle over a predetermined period by applying an averaging process to multiple time-series duty cycles (control commands) generated at predetermined time intervals, and use this average value to calculate the wind pressure estimate E2.

[0051] When the pair of CPUs 21a and 21b obtain wind pressure estimates E1 and E2, they evaluate the relative magnitudes of wind pressure estimates E1 and E2. That is, in step S4, the pair of CPUs 21a and 21b determine whether wind pressure estimate E1 is greater than wind pressure estimate E2.

[0052] If the decision in step S4 is "No", the pair of CPUs 21a and 21b set the wind pressure estimate E2 to the correction coefficient H (step S5). On the other hand, if the decision in step S4 is "Yes", the pair of CPUs 21a and 21b set the wind pressure estimate E1 to the correction coefficient H (step S6). In other words, the pair of CPUs 21a and 21b set the correction coefficient H based on the relative magnitudes of the wind pressure estimates E1 and E2.

[0053] Then, the pair of CPUs 21a and 21b correct the target rotational speed TR of the operation map obtained from the pair of ROMs 23a and 23b by using the correction coefficient H set by the above processing. In other words, the target rotational speed TR of the pair of wiper blades 1a and 1b is corrected based on the larger of the wind pressure estimates E1 and E2.

[0054] As described above, the wiping device A according to the first embodiment drives a pair of motors 7a and 7b (power sources) with a PWM drive signal (a predetermined drive signal) to cause a pair of wiper blades 1a and 1b to reciprocate, and corrects the inverted position of the pair of wiper blades 1a and 1b by changing the PWM drive signal in accordance with the external force acting on the pair of wiper blades 1a and 1b.

[0055] Furthermore, this wiping device A is equipped with a drive device 10 (power source drive unit) that acquires an estimated wind pressure value E1 (first estimated wind pressure value) based on the vehicle speed (movement speed) and an estimated wind pressure value E2 (second estimated wind pressure value) based on the PWM drive signal, corrects the upward reversal position of the pair of wiper blades 1a and 1b based on the estimated wind pressure value E1 if the estimated wind pressure value E1 is greater than the estimated wind pressure value E2, and corrects the upward reversal position of the pair of wiper blades 1a and 1b based on the estimated wind pressure value E2 if the estimated wind pressure value E1 is less than or equal to the estimated wind pressure value E2.

[0056] In this type of wiping device A, the larger of the two wind pressure estimates E1 and E2 is set as the correction coefficient H to correct the upper inversion position of the pair of wiper blades 1a and 1b. Therefore, according to the first embodiment, it is possible to stabilize fluctuations in the inversion position, thereby providing a wiping device A that can reduce the risk of interference between the pair of wiper blades 1a and 1b and other members (for example, the pillars of the vehicle).

[0057] Figure 3(a) shows the initial settings for the wind pressure estimates E1 and E2, which depend on the vehicle speed. In Figure 3(a), the dotted line represents the wind pressure estimate E1 based on the vehicle speed signal, and the solid line represents the wind pressure estimate E2 based on the duty cycle of the PWM drive signal. As shown in Figure 3(a), the wind pressure estimate E1 (dotted line) is set to a larger value than the wind pressure estimate E2 (solid line).

[0058] In contrast to these initial settings, Figure 3(b) shows the estimated wind pressure values ​​E1 and E2 when a tailwind disturbance acts on a pair of wiper blades 1a and 1b. In this case, the duty cycle-based wind pressure value E2 is greater than the estimated wind pressure value E1 because a tailwind acts on the pair of wiper blades 1a and 1b. In this case, the duty cycle-based wind pressure value E2 is set as the correction coefficient, and the upward inversion position of the pair of wiper blades 1a and 1b is corrected.

[0059] On the other hand, Figure 3(c) shows the estimated wind pressure values ​​E1 and E2 when a headwind disturbance acts on a pair of wiper blades 1a and 1b. In this case, the duty cycle-based wind pressure value E2 is smaller than the initial setting because a headwind acts on the pair of wiper blades 1a and 1b. In this case, the vehicle speed signal-based wind pressure value E1 is set as the correction coefficient, and the upward inversion position of the pair of wiper blades 1a and 1b is corrected.

[0060] [Second Embodiment] Next, a second embodiment of the present invention will be described with reference to Figure 4. In this second embodiment, the same reference numerals are used for components that are the same as those in the first embodiment.

[0061] As shown in Figure 4, the wiping device B according to the second embodiment comprises a pair of wiper blades 1a, 1b, a pair of wiper arms 2a, 2b, a link mechanism 4, a motor 7, an angle detection circuit 31, a drive circuit 32, and a control unit 10A. The control unit 10A also comprises a CPU 50, a ROM 51, and a RAM 52.

[0062] This wiping device B employs a single-motor drive system in which a pair of wiper blades 1a and 1b are driven by a single motor 7 (power source) by mechanically connecting a pair of wiper arms 2a and 2b with a link mechanism 4. In other words, wiping device B is provided with one power source, and this single power source causes the pair of wiper blades 1a and 1b to reciprocate. Similar to wiping device A according to the first embodiment, such wiping device B wipes rainwater from the surface (surface to be wiped) of the vehicle's windshield and rear window.

[0063] The link mechanism 4 is a mechanical component that is mechanically connected to the other ends of a pair of wiper arms 2a and 2b, and also to the output shaft of the motor 7. The link mechanism 4 is also equipped with a support shaft fixed to the vehicle and is rotatable around this support shaft. The motor 7 has its output shaft connected to the link mechanism 4, and by manipulating the rotation angle of the link mechanism 4, it causes the pair of wiper blades 1a and 1b to reciprocate on the surface to be wiped.

[0064] The angle detection circuit 31 has the same functions as the pair of angle detection circuits 31a and 31b in the first embodiment, and outputs a relative position signal that is proportional to the motor rotation angle of the motor 7 and indicates the amount of movement of the driver's side wiper blade 1a or the passenger's side wiper blade 1b. In addition, this angle detection circuit 31 outputs an absolute position signal that indicates the position of a specific wiper blade among the pair of wiper blades 1a and 1b.

[0065] The drive circuit 32 has the same functions as the drive circuits 32a and 32b in the first embodiment, and drives the motor 7 based on the drive command input from the drive control unit 51. That is, the drive circuit 32 drives the motor 7 according to the difference between the current rotational speed of the motor 7 and the target rotational speed TR.

[0066] The control unit 10A has the same functions as the wiper control unit 10a in the first embodiment. In addition, this control unit 10A indirectly provides feedback control of the motor 7 by directly controlling the drive circuit 32 by referring to the switch signal and vehicle speed signal input from the higher-level control device. In this control unit 10A, the CPU 50 has the same functions as the CPU 21a in the first embodiment.

[0067] The CPU 50 controls the drive circuit 32 based on the operation map stored in the ROM 23a, relative position signals and absolute position signals input from the angle detection circuit 31, and switch signals and vehicle speed signals input from the higher-level control system. The ROM 52 has the same functions as the ROM 23a in the first embodiment and stores the operation map, etc. The RAM 53 temporarily holds intermediate generated data from the CPU 50.

[0068] In such a wiping device B, the CPU 50 obtains the vehicle speed by acquiring a switch signal and a vehicle speed signal at predetermined timings through communication with a higher-level control unit (ECU). The CPU 50 then performs predetermined calculations on the vehicle speed to obtain an estimated wind pressure value E1, which is the wind pressure acting on the pair of wiper blades 1a and 1b due to the vehicle speed.

[0069] The CPU 50 then performs a predetermined calculation on the duty cycle of the PWM drive signal generated by the drive circuit 32 to obtain an estimated wind pressure value E2, which is the wind pressure value that acts on the pair of wiper blades 1a and 1b due to the duty cycle.

[0070] Once CPU 50 obtains wind pressure estimates E1 and E2 in this manner, it evaluates the relationship between wind pressure estimates E1 and E2. That is, CPU 50 determines whether wind pressure estimate E1 is greater than wind pressure estimate E2, and if this determination is "No", it sets wind pressure estimate E2 to a correction coefficient H.

[0071] On the other hand, if the above judgment is "Yes", the CPU 50 sets the wind pressure estimate E1 to a correction coefficient H. That is, the CPU 50 sets the correction coefficient H based on the relative magnitudes of the wind pressure estimate E1 and the wind pressure estimate E2. Then, the CPU 50 corrects the target rotational speed TR of the operation map obtained from the ROM 52 by using the correction coefficient H set by the above process. In other words, the target rotational speed TR of the pair of wiper blades 1a and 1b is corrected based on the larger of the wind pressure estimates E1 and E2.

[0072] Thus, the wiping device B according to the second embodiment drives a pair of motors 7a and 7b (power sources) with a PWM drive signal (a predetermined drive signal) to cause a pair of wiper blades 1a and 1b to reciprocate, and corrects the inverted position of the pair of wiper blades 1a and 1b by changing the PWM drive signal in accordance with the external force acting on the pair of wiper blades 1a and 1b.

[0073] Furthermore, this wiping device B includes a control unit 10A (power source drive unit) that acquires an estimated wind pressure value E1 (first estimated wind pressure value) based on the vehicle speed (movement speed) and an estimated wind pressure value E2 (second estimated wind pressure value) based on the PWM drive signal, corrects the upward inversion position of the pair of wiper blades 1a and 1b based on the estimated wind pressure value E1 if the estimated wind pressure value E1 is greater than the estimated wind pressure value E2, and corrects the upward inversion position of the pair of wiper blades 1a and 1b based on the estimated wind pressure value E2 if the estimated wind pressure value E1 is less than or equal to the estimated wind pressure value E2.

[0074] In this type of wiping device B, the larger of the wind pressure estimates E1 and E2 is set as the correction coefficient H to correct the upward inversion position of the pair of wiper blades 1a and 1b. Therefore, according to the second embodiment, it is possible to stabilize fluctuations in the upward inversion position, thereby providing a wiping device A that can reduce the risk of interference between the pair of wiper blades 1a and 1b and other members (for example, the pillars of the vehicle).

[0075] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible. For example, the block diagrams in Figures 1 and 4 are merely examples of control configurations, and various modifications are possible without departing from the spirit of the present invention.

[0076] Furthermore, in the above embodiment, the risk of interference with other members (e.g., the pillars of the vehicle) was reduced by stabilizing the upward inversion position, but the present invention is not limited thereto. For example, when the reference position of a pair of wiper blades 1a and 1b is in the upward inversion position, it is possible to stabilize the fluctuation of the downward inversion position by setting a correction coefficient H based on the wind pressure estimates E1 and E2.

[0077] Furthermore, although the above embodiment described a power source drive unit that drives the power source by adjusting the drive current according to the duty cycle of the PWM drive signal, the present invention is not limited thereto. For example, a power source drive unit that generates a drive signal of the type that drives the power source by adjusting the dynamic current according to the amplitude may be employed. In this case, the wind pressure estimate value E2 is estimated based on the amplitude of the drive signal. [Explanation of Symbols]

[0078] 1a, 1b... Wiper blade, 2a, 2b... Wiper arm, 3a, 3b... Wiper shaft, 7a, 7b... Motor (power source), 10... Drive unit (power source drive unit), 10a, 10b... Wiper control unit, 21a, 21b... CPU, 22a, 22b... Communication circuit, 23a, 23b... ROM, 24a, 24b... RAM, 31a, 31b... Angle detection circuit, 32a, 32b... Drive circuit

Claims

1. A wiping device that causes a wiper blade to reciprocate by driving a power source with a predetermined drive signal, and corrects the reverse position of the wiper blade by changing the drive signal in accordance with the wind pressure acting on the wiper blade, A wiping device characterized by comprising a power source drive unit that acquires a first wind pressure estimate based on the drive signal and a second wind pressure estimate based on the vehicle speed, corrects the reversal position based on the first wind pressure estimate if the first wind pressure estimate is greater than the second wind pressure estimate, and corrects the reversal position based on the second wind pressure estimate if the first wind pressure estimate is less than or equal to the second wind pressure estimate.

2. The aforementioned drive signal is a PWM (Pulse Wide Modulation) signal. The wiping device according to claim 1, characterized in that the power source drive unit acquires the first wind pressure estimate based on the duty cycle of the PWM signal.

3. The wiping device according to claim 2, characterized in that the duty cycle is the average value over a predetermined period during the forward or return journey of the wiper blade.

4. The wiping device according to any one of claims 1 to 3, wherein one or two power sources are provided, and one power source is used to reciprocate one or two wiper blades, and two power sources are used to reciprocate two wiper blades individually.

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