Jamming protection device for moving member

• US 20040104701A1
• Filed: 10/01/2003
• Published: 06/03/2004
• Est. Priority Date: 04/02/2001
• Status: Active Grant

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Ohshima, Shunzou
• Granted Patent: US 6,867,563 B2
• Time in Patent Office: Days
• US Class Current: 318/445
• CPC Class Codes: E05F 15/41 Detection by monitoring transmitted force or torque E05F15/48 takes precedence; Safety couplings with activation dependent upon torque or force, e.g. slip couplings
• CPC Class Codes: E05Y 2400/31 Force or torque control
• CPC Class Codes: E05Y 2400/53 Wing impact prevention or reduction
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities
• CPC Class Codes: H02H 7/0851 for motors actuating a movable member between two end positions, e.g. detecting an end position or obstruction by overload signal
• CPC Class Codes: H02H 7/0858 by reversing, cycling or reducing the power supply to the motor

Abstract

When abnormal current due to jamming is detected through motor current (ID), the motor current (ID) performs an operation in which an ON/OFF operation and a continuous ON operation are repeated, so that increment of the motor current (ID) is restrained. At this time, determination of jamming is performed based on the ON/OFF operation and the continuous ON operation. When the jamming is determined, the motor current (ID) is stopped, and the motor is reversed.

Claims

1. A jamming protection device for a moving member driven by a motor (5) being able to rotate in the reverse direction supplied with a motor current (ID) by a power supply unit (VB), comprising:

a current detection circuit (2) being connectable to one of a plus terminal and a minus terminal of the power supply unit (VB), configured to conduct the motor current (ID) and to detect an increment of the motor current (ID); and

a current limiting circuit (7) configured to conduct the motor current (ID) and to decrease and increase the motor current (ID) within a predetermined region when the increment of the motor current (ID) exceeds a predetermined value.

2. The jamming protection device of claim 1, wherein said current limiting circuit (7) comprises a semiconductor-switching element (T1), the decrement of the motor current (ID) is to turn the semiconductor switching element (T1) to an ON/OFF operation for a period that depends on a reduction of the motor speed due to the jamming, and the increment of the motor current (ID) is to turn the semiconductor switching element (T1) to a continuous ON.

3. The jamming protection device of claim 2, wherein said current detection circuit (2) comprises

a main element (R1, T4) configured to conduct the motor-current (ID) and identified by a main resistance,

a reference element (R20, T5) configured to conduct a reference current (Iref), identified by a reference resistance being n times as much as the main resistance, and

a current following circuit (3) configured to conduct the reference current (Iref), and configured to set the reference current (Iref) at one over the n (1/n) of the motor current (ID) constantly.

4. The jamming protection device of claim 3, wherein the main element (R1, T4) includes a shunt resistor (R1), and the reference element (R20, T5) includes a reference resistor (R20).

5. The jamming protection device of claim 3, wherein the main element (R1, T4) includes a main field effect transistor (T4), and the reference element (R20, T5) includes a reference field effect transistor (T5).

6. The jamming protection device of claim 3, wherein the main element (R1, T4) is connectable in series to the motor (5) and the current limiting circuit (7), one end of the main element (R1, T4) is connectable to one of the plus terminal and the minus terminal of the power supply unit (VB), one end of the reference element (R20, T5) is connectable to a node of the main element (R1, T4), one of the plus terminal and the minus terminal of the power supply unit (VB), the other end of the reference element (R20, T5) connects to the current following circuit (3), and the current following circuit (3) is connectable to the other of the plus terminal and the minus terminal of the power supply unit (VB).

7. The jamming protection device of claim 5, wherein a drain of the main field effect transistor (T4) is connectable to the plus terminal of the power supply unit (VB), a drain of the reference field effect transistor (T5) connects to the drain of the main field effect transistor (T4), a source of the reference field effect transistor (T5) connects to the current following circuit (3), the current following circuit (3) is connectable to the minus terminal of the power supply unit (VB), and gates of the main field effect transistor (T4) and the reference field effect transistor (T5) connect to each other and are able to be driven by a driver (19, 21).

8. The jamming protection device of claim 3, wherein the current following circuit (3) includes

a slow following circuit (41 and 42) configured to conduct a slow following current (Iref-s) of which time constant is several times longer than a period from a jamming start to a start of reverse rotation of the motor (5), and

a fast following circuit (43 and 44) configured to conduct a fast following current (Iref-f) of which time constant is much smaller than that of slow following current, and which can compensate the difference between the reference (Iref) and the slow following current (Iref-s),and

both the slow following circuit (41 and 42) and the fast following circuit (43 and 44) are connected with each other in parallel.

9. The jamming protection device of claim 8, wherein the current following circuit (3) comprises a first comparator (CMP1) configured to detect a difference of voltage drops of the main element (R1, T4) and the reference element (R20, T5),

the slow following circuit (41 and 42) comprises a slow charge discharge circuit (41) connecting to an output of the first comparator (CMP1) and the ground, including a first resistor (R21) connecting to the output of the first comparator (CMP1) and a first capacitor (C1) connecting to the first resistor (R21) in series and to the ground, and configured to link the slow following current (Iref-s) to a potential of the first capacitor (C1),

the fast following circuit (43 and 44) comprises a fast charge discharge circuit (43) connecting to the output of the first comparator (CMP1) and the ground and to the slow charge discharge circuit (41) in parallel, including a second resistor (R22) connecting to the output of the first comparator (CMP1) and a second capacitor (C2) connecting to the second resistor (R22) in series and to the ground, connecting to the first capacitor (C1) through a high resistor (R28) and identified by a fast time constant of the fast charge discharge circuit (43) is smaller than a slow time constant of the slow charge discharge circuit (41), and configured to link the fast following current (Iref-f) to a potential of the second capacitor (C2).

10. The jamming protection device of claim 9, wherein the slow following circuit (41 and 42) comprises a slow source follower circuit (42) including a first field effect transistor (T21) configured to conduct the slow following current (Iref-s) identified by a gate connecting to the first capacitor (C1), and a third resistor (R23) connecting to a source of the first field effect transistor (T21).

the fast following circuit (43 and 44) comprises a fast source follower circuit (44) including a second field effect transistor (T22) identified by a gate connecting to the second capacitor (C2) configured to conduct by the fast following current (Iref-f) and a fourth resistor (R24) configured to conduct the fast following current (Iref-f).

11. The jamming protection device of claim 10, wherein a gate of the second field effect transistor (T22) directly connects to the output of the first comparator (CMP1), and the second resistor (R22), the second capacitor (C2) and the high resistor (R28) are deleted, in order to get rid of any delay of the fast following circuit (44) so that the fast following circuit (44) is identified by having almost zero time constant.

12. The jamming protection device of claim 1, wherein a mean value of the motor current (ID) in the period of the current limiting operation is restrained to be slightly greater than that of the motor current (ID) just before the jamming start by the predetermined value.

13. The jamming protection device of claim 10, wherein said current detection circuit (2) comprises a second comparator (CMP2) configured to compare a first source potential of the first field effect transistor (T21) with an evaluating potential smaller than a second source potential of the second field effect transistor (T22) by a jamming detection voltage,

the semiconductor switching element (T1) performs the ON/OFF operation to decrease the motor current (ID) when the evaluating potential is greater than the first source potential, and performs the continuous ON to increase the motor current when the evaluating potential is smaller than the first source potential.

14. The jamming protection device of claim 13, wherein a period of the ON/OFF operation is identified by depending on an off delay time of the semiconductor switching element (T1) and a decrement rate of the motor current (ID) due to the ON/OFF operation, and a period of the continuous ON is identified by depending on an increment rate of the motor current (ID) due to the continuous ON.

15. The jamming protection device of claim 13, wherein the fast source follower circuit (44) comprises a diode (D21) identified by a forward voltage drop serving as the jamming detection voltage connecting to a source of the second field effect transistor (T22) in serial.

16. The jamming protection device of claim 13, wherein said current limiting circuit (7) comprises

a reference voltage circuit (8) configured to generate an upper reference voltage (VH) and a lower reference voltage (VL), and

a third comparator (CMP3) configured to compare a voltage drop in the semiconductor switching element (T1) with one of the upper reference voltage (VH) and the lower reference voltage (VL),

the ON/OFF operation comprises turning off the semiconductor switching element (T1), increasing the voltage drop in the semiconductor switching element (T1) over the upper reference voltage (VH), turning on the semiconductor switching element (T1), dropping the voltage drop in the semiconductor switching element (T1) under the lower reference voltage (VL), turning off the semiconductor switching element (T1) again.

17. The jamming protection device of claim 16, wherein the semiconductor switching element (T1) is a field effect transistor, and

the lower reference voltage (VL) and the upper reference voltage (VH) are identified by setting in such a way as supply voltage (VB) is larger than the upper reference voltage (VH) that is larger than the lower reference voltage (VL) that is larger than ground level (GND) so that a Miller effect constantly occurs in a gate capacity of the semiconductor switching element (T1) with contribution of an inductance of the motor (M) during the current limiting operation and therewith makes a variation of the motor current and motor torque to be minimized.

18. The jamming protection device of claim 13, wherein the current limiting circuit (7) is identified by making the motor (M) generate a motor output during the ON/OFF operation to keep applying a driving force to the moving member so that the motor (M) maintains the same speed as the moving member, which improves ability of restoring from a short term over load such as caused by driving on a rough road without malfunctions.

19. The jamming protection device of claim 13, wherein jamming determination circuit (6) is identified by detecting a ratio of the ON/OFF operation time to the continuous ON time, or measuring either the ON/OFF operation time or the continuous ON time, utilizing the fact that a reduction of the rotational speed of the motor prolongs the ON/OFF operation time and shortens the continuous ON time when the current limiting circuit (7) makes the rotational speed of the motor (M) hardly change in one cycle of the ON/OFF operation, during current limiting operation.

20. The jamming protection device of claim 19, wherein to measure the ON/OFF operation time is to count a cycle number of the ON/OFF operations.

21. The jamming protection device of claim 20, wherein the semiconductor switching element (T1) is a field effect transistor, the current limiting circuit (7) includes a variable resistor (R32) configured to make a gate series resistor of the semiconductor switching element (T1) adjusted to change a period of the ON/OFF operation.

22. The jamming protection device of claim 19, wherein the reduction of the rotational speed of the motor (M) of the jamming determination criterion is greater than a possible reduction of the rotational speed of the motor (M) at a momentary change without the jamming.

23. The jamming protection device of claim 9, wherein said current detection circuit (2) comprises a start circuit (4) configured to detect the jamming immediately after starting to drive the moving member, the first capacitor (C1) is charged during a rush current masking period, and after the rush current masking period, the first capacitor (C1) is discharged via the output of the first comparator (CMP1) for a period in which the output of the first comparator (CMP1) is low level.

24. The jamming protection device of claim 12, wherein said current detection circuit (2) comprises a start circuit (4) configured to detect the jamming immediately after starting to drive the moving member, the motor (M) does not rotate by the jamming, the ON/OFF operation starts at an end of the rush current masking period.

25. The jamming protection device of claim 10, wherein the motor current (ID) is converted to a motor voltage, a displacement of the motor voltage is amplified to generate a second source potential of the second field effect transistor (T22), a mean value of the second source potential for a long period is generated, as a first source potential, the current detection circuit (2) detects that the second source potential is greater than the first source potential by the predetermined value, and the current limiting circuit (7) limits the motor current (ID) by a ON/OFF operation and a continuous ON.

26. The jamming protection device of claim 25, wherein a gate of the second field effect transistor (T22) directly connects to the output of the fist comparator (CMP1), the second source voltage is a voltage drop generated by the fast following current (Iref-f) flowing in a resistor (R24), and the first source voltage is a voltage drop generated by the slow following current (Iref-s) flowing in a resistor (R23).

27. The jamming protection device of claim 25, wherein

a decrement of the motor current (ID) in the ON/OFF operation is as much as a part (Iref-2) of the reference current (Iref) flowing in the reference resistor (R20) in the continuous ON operation.