Vehicle power back door system

Abstract

The present invention provides a vehicle power tailgate system that can reduce the axial force of the spindle stay even when the rotation of the tailgate in the opening direction is restrained. [Solution] In the power back door system 1, the voltage rise of the electric motor 42 is suppressed when the drive voltage of the electric motor 42 reaches a predetermined value due to the rotation of the back door 2 in the opening direction being restrained. Therefore, even when the rotation of the back door 2 in the opening direction is restrained, the increase in the axial force of the spindle stay 3 is suppressed, thereby preventing high loads from being placed on each mounting part of the spindle stay 3.

Description

Technical Field

[0001] The present invention relates to a power backdoor system for a vehicle.

Background Art

[0002] As disclosed in Patent Document 1, a power backdoor system mounted on a vehicle is known. This power backdoor system includes a backdoor rotatably supported by a hinge with respect to a vehicle body, and a spindle stay (backdoor opening / closing mechanism) disposed between the backdoor and the vehicle body. The spindle stay includes, for example, an outer tube, an inner tube, an electric motor provided on the outer tube, a spindle nut provided on the inner tube, etc. When the spindle, which is the rotating shaft of the electric motor, rotates, the spindle nut engaged with the spindle moves in the axial direction. As a result, the outer tube and the inner tube move relative to each other in the axial direction, and the entire spindle stay expands and contracts. Then, due to the expansion and contraction of this spindle stay, the backdoor rotates with respect to the vehicle body (opens and closes the luggage room).

[0003] FIG. 3(a) shows an example of the transition of the voltage of the electric motor (hereinafter, also referred to as motor voltage or drive voltage) required to open the backdoor in the power backdoor system. As shown in this figure, the motor voltage increases as the backdoor opening degree increases, and becomes the maximum voltage Vmax (the upper limit value of the in-vehicle battery voltage, for example, 12V) in a range close to full open.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when opening the back door, if there is an obstacle such as a building wall on the side of the back door that is opening, the back door, which is operating in the opening direction, will come into contact with the obstacle, and its rotation in the opening direction will be restrained (hereinafter, this state will be referred to as the open-restrained state). Even when such an open-restrained state occurs, the electric motor continues to operate to open the back door, so the motor voltage may reach the maximum voltage Vmax even when the back door opening is small. Figure 3(b) shows an example of the changes in motor voltage and spindle stay axial force when this open-restrained state occurs. In this figure, the open-restrained state occurs at timing T1, and the rotation of the back door in the opening direction is restrained. As is clear from this figure, the motor voltage rises rapidly from timing T1 when the open-restrained state occurs, and reaches the maximum voltage Vmax in a short time. Along with this, the axial force of the spindle stay also rises rapidly.

[0006] When the axial force on the spindle stay remains high, a high load is placed on each mounting point of the spindle stay. Therefore, considering this, the spindle stay design required high rigidity in each part. This resulted in an increase in the size and weight of the spindle stay (making it difficult to miniaturize or reduce the weight of the spindle stay), and there was room for improvement in this respect.

[0007] These issues are not limited to cases where a spindle stay is used as the back door opening and closing mechanism; they may occur similarly when other back door opening and closing mechanisms are used.

[0008] The present invention has been made in view of the above, and its objective is to provide a vehicle power back door system that can reduce the load on each mounting part of the back door opening and closing mechanism even when the rotation of the back door in the opening direction is restrained. [Means for solving the problem]

[0009] The present invention provides a solution for achieving the above objectives, based on a vehicle power back door system comprising: a back door rotatably supported on the vehicle body; a back door opening and closing mechanism provided between the back door and the vehicle body for opening and closing the back door in accordance with the operation of an electric motor; and a control unit for controlling the electric motor. This vehicle power back door system is characterized in that the control unit implements voltage suppression control to suppress the voltage rise of the electric motor when the voltage of the electric motor reaches a predetermined value due to the rotation of the back door in the opening direction being restrained.

[0010] Due to this specific condition, if the rotation of the back door in the opening direction is restricted (open-restricted state), the electric motor will continue to operate to open the back door, causing the voltage (motor voltage) to rise. When the electric motor voltage reaches a predetermined value (for example, a predetermined value lower than the upper limit of the vehicle battery voltage), a control to suppress the voltage rise (voltage suppression control) is implemented, preventing further voltage increases. This suppresses the increase in stress inside the back door opening and closing mechanism (for example, the axial force of the spindle stay), and prevents high loads from being placed on each mounting part of the back door opening and closing mechanism. [Effects of the Invention]

[0011] In this invention, the power back door system is designed to suppress the voltage rise of the electric motor when the voltage of the electric motor reaches a predetermined value due to the rotation of the back door being restricted in the opening direction. Therefore, even when the rotation of the back door is restricted in the opening direction, the increase in stress inside the back door opening and closing mechanism is suppressed, thereby preventing high loads from being placed on each mounting part of the back door opening and closing mechanism. [Brief explanation of the drawing]

[0012] [Figure 1]Figure 1(a) is a schematic diagram showing the rear of a vehicle including a back door according to an embodiment, and Figure 1(b) is a schematic block diagram of the control system in the power back door system. [Figure 2] Figure 2(a) shows an example of the changes in motor voltage and axial force of the spindle stay when an open-restrained state occurs in the embodiment, and Figure 2(b) shows the relationship between the magnitude of the load acting on the mounting bracket of the spindle stay and the amount of deformation. [Figure 3] Figure 3(a) shows an example of the changes in motor voltage required to open the back door, and Figure 3(b) shows an example of the changes in motor voltage and spindle stay axial force when an open-restrained state occurs in the conventional technology. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0014] Figure 1(a) is a schematic diagram of the rear of the vehicle including the back door 2 according to this embodiment. As shown in Figure 1(a), the power back door system 1 comprises the back door 2, a spindle stay (back door opening and closing mechanism) 3, and a control system 4 (see Figure 1(b)).

[0015] The spindle stay 3 is positioned on both sides of the back door 2 in the vehicle width direction. The spindle stay 3 has joints 31 and 32 at both ends. One end of the spindle stay 3 is rotatably connected to the side 21 of the back door 2 by joint 31, and the other end of the spindle stay 32 is rotatably connected to the body B by joint 32.

[0016] The spindle stay 3 has, for example, a nested tubular body in which an inner tube is inserted into an outer tube, and these outer and inner tubes are connected so as to be able to move relative to each other in the axial direction. The spindle stay 3 houses a coil spring (not shown) and a drive mechanism (not shown). The coil spring extends the tubular body consisting of the outer and inner tubes by elastic force, and applies an opening reaction force that is approximately balanced by the weight of the back door 2, which rotates in the closing direction due to its own weight. The drive mechanism has, for example, an electric motor 42 (see Figure 1(b)) provided on the outer tube and a spindle nut provided on the inner tube, and as the spindle, which is the rotation shaft of the electric motor 42, rotates, the spindle nut, which is screwed onto this spindle, moves in the axial direction. As a result, the outer and inner tubes move relative to each other in the axial direction, and the entire spindle stay 3 expands and contracts. As the spindle stay 3 extends and retracts, the back door 2, which is rotatably supported by the body B by the hinge 22, rotates, and the luggage compartment L of the vehicle S opens and closes.

[0017] -Power back door system control system- Figure 1(b) is a schematic block diagram of the control system 4 in the power back door system 1 according to this embodiment. As shown in Figure 1(b), the control system 4 of the power back door system 1 includes a back door switch 41, an electric motor 42, a voltage sensor 43, a back door opening degree sensor 44, and a back door ECU (control unit) 45.

[0018] The back door switch 41 is located on the back door 2 and consists of, for example, an open switch and a close switch. When pressed, it sends instruction signals to the back door ECU 45 to open, close, or stop the back door 2. In addition to the back door switch 41, other devices that send various instruction signals to the back door ECU 45 include a smart key, an in-cabin switch, and a so-called kick sensor located at the bottom of the rear bumper in vehicles with a hands-free power back door function.

[0019] The electric motor 42 rotates as described above to expand and contract the entire spindle stage 3, thereby causing the back door 2 to rotate. For example, by operating in the forward rotation direction, the back door 2 is rotated in the opening direction, and by operating in the reverse rotation direction, the back door 2 is rotated in the closing direction. The electric motor 42 is connected to the back door ECU 45 by a signal line. Thus, the electric motor 42 receives the control command signal output from the back door ECU 45 and drives according to the control command signal.

[0020] The voltage sensor 43 detects the voltage (drive voltage) of the electric motor 42. Also, this voltage sensor 43 is connected to the back door ECU 45 by a signal line. Thus, the voltage sensor 43 transmits the detected drive voltage information to the back door ECU 45 as a voltage detection signal.

[0021] The back door opening degree sensor 44 detects the opening degree of the back door 2. As means for detecting the opening degree of this back door 2, well-known ones can be applied. Also, this back door opening degree sensor 44 is connected to the back door ECU 45 by a signal line. Thus, the back door opening degree sensor 44 transmits the detected back door 2 opening degree information to the back door ECU 45 as a back door opening degree detection signal.

[0022] The back door ECU 45 includes a processor such as a CPU (Central Processing Unit), a ROM (Read-Only Memory) that stores a control program, a RAM (Random-Access Memory) that temporarily stores data, and input / output ports and the like. As functional units realized by the control program, the back door ECU 45 includes a switch signal receiving unit 45a, a rotation command signal transmitting unit 45b, a motor voltage signal receiving unit 45c, a back door opening degree signal receiving unit 45d, and a motor voltage suppression control unit 45e.

[0023] The switch signal receiving unit 45a receives signals from the back door switch 41. Specifically, it receives open instruction signals, close instruction signals, stop instruction signals, etc., corresponding to the operation of the back door switch 41. The switch signal receiving unit 45a can also receive signals from various switches such as the smart key, interior switches, and kick sensor.

[0024] The rotation command signal transmitting unit 45b transmits a control command signal to the electric motor 42 in accordance with the instruction signal received by the switch signal receiving unit 45a. For example, when an open instruction signal is received from the back door switch 41, a control command signal is transmitted to the electric motor 42 to operate in the forward rotation direction to open the back door 2. When a close instruction signal is received from the back door switch 41, a control command signal is transmitted to the electric motor to operate in the negative rotation direction to close the back door. When a stop instruction signal is received from the back door switch 41, a control command signal is transmitted to the electric motor to stop the rotation of the back door.

[0025] The motor voltage signal receiving unit 45c receives a voltage detection signal, which is information about the drive voltage of the electric motor 42 detected by the voltage sensor 43 and transmitted from the voltage sensor 43.

[0026] The back door opening degree signal receiving unit 45d receives a back door opening degree detection signal, which is information about the opening degree of the back door 2 detected by the back door opening degree sensor 44 and transmitted from the back door opening degree sensor 44.

[0027] The motor voltage suppression control unit 45e receives information on the drive voltage of the electric motor 42 received by the motor voltage signal receiving unit 45c, and information on the opening degree of the back door 2 received by the back door opening degree signal receiving unit 45d. If, during the opening operation of the back door 2, the drive voltage reaches a predetermined value even though the opening degree of the back door 2 is below a predetermined opening degree, the control unit performs voltage suppression control to suppress the voltage rise of the electric motor 42, based on this condition.

[0028] As mentioned above, when the back door 2, which operates in the opening direction, does not come into contact with an obstacle and its rotation in the opening direction is not restrained, the motor voltage (drive voltage) of the electric motor 42 increases as the back door opening degree increases, and in the range close to fully open, it reaches the maximum voltage Vmax (the upper limit of the vehicle battery voltage, for example, 12V) (see Figure 3(a)). However, in the conventional technology, when the back door, which operates in the opening direction, comes into contact with an obstacle and its rotation in the opening direction is restrained, the motor voltage reaches the maximum voltage Vmax even when the back door opening degree is small (see Figure 3(b)), and there was a risk that the axial force of the spindle stay would remain high, placing a high load on each mounting part of the spindle stay.

[0029] Therefore, in this embodiment, if the drive voltage of the electric motor 42 reaches a predetermined value during the opening operation of the back door 2, even though the back door opening degree is small, the motor voltage suppression control unit 45e performs voltage suppression control to suppress the voltage rise of the electric motor 42.

[0030] Specifically, a voltage value lower than the upper limit of the vehicle battery voltage (maximum voltage Vmax) is set in advance as the control start threshold, and the back door opening degree (hereinafter referred to as the reference back door opening degree) that corresponds to the same voltage value as the control start threshold is recognized under normal conditions (when the back door 2, which operates in the opening direction, is not restricted by an obstacle). Then, if the actual back door opening degree when the drive voltage information (motor voltage value) of the electric motor 42 received by the motor voltage signal receiving unit 45c reaches the control start threshold is smaller than the reference back door opening degree, it is determined that the drive voltage of the electric motor 42 has reached the control start threshold due to the rotation of the back door 2 in the opening direction being restricted, and voltage suppression control is implemented to suppress the voltage rise of the electric motor 42. Note that the conditions for implementing voltage suppression control are not limited to these. Specifically, as part of this voltage suppression control, a control command signal is transmitted to the electric motor 42 to rapidly reduce the motor voltage to zero, gradually reduce it, or maintain it at the control start threshold. Furthermore, the voltage suppression control is not limited to this; any method that can suppress the voltage rise of the electric motor 42 is acceptable.

[0031] Figure 2(a) shows an example of the changes in motor voltage and axial force of spindle stay 3 when the motor voltage is rapidly reduced to zero as a voltage suppression control. As shown, by rapidly reducing the motor voltage to zero, the axial force of spindle stay 3 also rapidly decreases to zero.

[0032] -Effects of the embodiment- As described above, in this embodiment, the power back door system 1 is configured to suppress the voltage rise of the electric motor 42 when the drive voltage of the electric motor 42 reaches a predetermined value due to the rotation of the back door 2 in the opening direction being restrained. Therefore, even when the rotation of the back door 2 in the opening direction is restrained, the increase in the axial force of the spindle stay 3 is suppressed, thereby preventing high loads from being placed on each mounting part of the spindle stay 3. As a result, it becomes unnecessary to design the spindle stay 3 with significantly increased rigidity in each part, making it possible to achieve miniaturization and weight reduction compared to conventional spindle stays. Figure 2(b) shows the relationship between the magnitude of the load acting on the mounting bracket of the spindle stay 3 and the amount of deformation. In the conventional technology, the load acting on the mounting bracket increased to N2, reaching the plastic deformation range of the mounting bracket. In contrast, in this embodiment, the load acting on the mounting bracket is suppressed to N1, remaining within the elastic deformation range of the mounting bracket. As a result, plastic deformation of the mounting bracket is suppressed.

[0033] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments described above, and all modifications and applications are possible within the scope of the claims and equivalents thereof.

[0034] For example, the above embodiment described a case in which a spindle stay 3 is used as the back door opening and closing mechanism. The present invention is not limited to this, and can also be applied to cases in which other back door opening and closing mechanisms are used.

[0035] Furthermore, in the above embodiment, the condition for implementing voltage suppression control was that the actual back door opening when the value of the drive voltage of the electric motor 42 reached the control start threshold was smaller than the reference back door opening. The present invention is not limited to this, and voltage suppression control may be implemented on the condition that the value of the drive voltage of the electric motor 42 reaches the control start threshold within a predetermined time after the opening operation of the back door 2 is started (on the condition that the value of the drive voltage of the electric motor 42 reaches the control start threshold within a predetermined time due to the rapid increase in the drive voltage of the electric motor 42 caused by the restriction of the rotation of the back door 2 in the opening direction). In other words, the present invention implements voltage suppression control on the condition that the drive voltage of the electric motor 42 reaches a predetermined value due to the restriction of the rotation of the back door 2 in the opening direction, and the parameters for determining whether or not that condition is met are not particularly limited. [Industrial applicability]

[0036] This invention is applicable to a vehicle's power tailgate system. [Explanation of Symbols]

[0037] 1…Power back door system 2…Back door 3…Spindle stay (back door opening / closing mechanism) 4…Control system 42...Electric motor 45...Back door ECU (control unit) 45e...Motor voltage suppression control unit B...Body (vehicle body)

Claims

[Claim 1] A vehicle power back door system comprising a back door rotatably supported on the vehicle body, a back door opening and closing mechanism provided between the back door and the vehicle body for opening and closing the back door in accordance with the operation of an electric motor, and a control unit for controlling the electric motor, The power back door system is characterized in that the control unit performs voltage suppression control to suppress the voltage rise of the electric motor when the voltage of the electric motor reaches a predetermined value due to the rotation of the back door in the opening direction being restrained.

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