JP2005325809A - Valve lift adjusting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve lift adjusting device utilizing a motor with reduced number of signal wires connecting a control circuit with a driving circuit. <P>SOLUTION: Control signals give first-third control signals to the driving circuit. The driving circuit for switching a current carrying condition to the motor in accordance with duty ratio of the first control signal, voltage of the second control signal, and voltage of the third control signal, stops current carrying and driving of the motor and transmits overcurrent detection signals to the control circuit when detecting overcurrent in a current carrying path to the motor. The driving circuit resumes current carrying and driving to the motor after a predetermined period of time elapses after the control circuit receiving the overcurrent detection signals detects that both of voltage of the second control signals and voltage of the third control signals are set to low level. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a valve lift adjusting device.

For example, as disclosed in Patent Document 1, a valve lift adjusting device that adjusts a maximum valve lift amount in an internal combustion engine (hereinafter referred to as an engine) using a rotational torque of a motor is known.
In such a motor-use type valve lift adjusting device, the drive circuit drives the motor to be energized in accordance with a control signal generated by the engine control circuit.

  For example, conventionally, when the control circuit rotates the motor in the forward direction, the duty ratio of the first control signal is set to a value necessary for the forward rotation, and the voltage of the second control signal and the voltage of the third control signal are set to high level and Set to low level. Further, when the control circuit reverses the motor, the duty ratio of the first control signal is set to a value necessary for the reverse rotation, and the voltage of the second control signal and the voltage of the third control signal are set to a low level and a high level, respectively. Set. The drive circuit switches the energization state to the motor according to the duty ratio of the first control signal, the voltage of the second control signal, and the voltage of the third control signal set in this way. Further, in the drive circuit, there is a possibility that an overcurrent flows in the energization path due to a ground fault in the energization path. Therefore, when such an overcurrent is detected, the energization drive of the motor is stopped and an overcurrent detection signal is detected. Is sent to the control circuit. The control circuit that has received the overcurrent detection signal sends a reset signal to the drive circuit after confirming the operating state of the engine, etc., thereby instructing the drive circuit to resume the stopped energization drive.

JP 2002-161864 A

However, in the above-described conventional apparatus, in addition to the first to third control signals for switching the energization state of the motor by the drive circuit, the overcurrent is detected and the drive circuit in the energization drive stop state is restored. Therefore, a reset signal is required. Therefore, the number of signal lines connecting between the control circuit and the drive circuit is increased. In general, a control circuit having an engine control function has a large number of terminals for connecting engine control signal lines, so the number of signal lines is reduced between the control circuit and the drive circuit, and the number of terminals in the control circuit is reduced. It is important to suppress the increase of.
An object of the present invention is to provide a motor-based valve lift adjusting device that reduces the number of signal lines connecting between a control circuit and a drive circuit.

  According to the first aspect of the present invention, when the drive circuit detects an overcurrent in the energization path to the motor, the drive circuit stops the energization drive of the motor and transmits an overcurrent detection signal to the control circuit. Further, the drive circuit detects that the control circuit that has received this overcurrent detection signal has set both the voltage of the second control signal and the voltage of the third control signal to a low level, and then, after a predetermined time has elapsed, Resume energization drive. As a result, the drive circuit that has detected the overcurrent and has stopped the energization drive outputs the second and third control signals among the first to third control signals required when switching the energization state to the motor. It can be restored using it. Therefore, since the reset signal from the control circuit to the drive circuit, which is required in the above-described conventional device, is unnecessary, the number of signal lines connecting the control circuit and the drive circuit can be reduced.

  According to the invention described in claim 2, when the overcurrent is detected in the energization path to the motor, the drive circuit stops the energization drive of the motor and transmits an overcurrent detection signal to the control circuit. Further, the drive circuit resumes energization driving of the motor after a predetermined time has elapsed since the control circuit that has received the overcurrent detection signal detects that the duty ratio of the first control signal is set to 0%. As a result, the drive circuit that has detected the overcurrent and has stopped the energization drive uses the first control signal among the first and second control signals required when switching the energization state to the motor. Be restored. This eliminates the need for a reset signal from the control circuit to the drive circuit, which is required in the above-described conventional apparatus. In addition, the control signal necessary for switching the energization state of the motor is also less than in the case of the above-described conventional device. According to the second aspect of the present invention, the number of signal lines connecting between the control circuit and the drive circuit can be sufficiently reduced.

  In the first and second aspects of the invention, the control circuit may or may not have a function of controlling the engine as in the case of the third aspect of the invention. In the control circuit having the engine control function, the number of signal lines connecting between the control circuit and the drive circuit is reduced by the above-described principle, so that an increase in the number of terminals is suppressed.

Hereinafter, a plurality of embodiments of the present invention will be described based on the drawings.
(First embodiment)
The principal part of the valve lift adjustment apparatus by 1st embodiment of this invention is shown in FIGS. The valve lift adjusting device 2 uses the rotational torque of the motor 20 driven by the motor driving device 70 to adjust the maximum valve lift amount in the engine for the intake valve.

The valve lift adjusting device 2 includes an actuator 10 that linearly drives the control shaft 30 in the axial direction, and a lift amount changing mechanism (not shown) that changes the target maximum valve lift amount based on the axial position of the control shaft 30. Consists of
As shown in FIG. 2, the actuator 10 includes a motor 20, a control shaft 30, a transmission unit 40, a drive cam 50 (see FIG. 4), an angle sensor 60, and a motor drive device 70.

The motor 20 is a DC brush motor, and includes a rotor 22 around which a coil is wound, and a permanent magnet 24 that covers the outer edge of the rotor 22. A motor gear 28 is fixed to the end of a rotating shaft 26 that rotates together with the rotor 22 in the motor 20 so as to be integrally rotatable.
The control shaft 30 is coupled to the support frame 41 of the transmission unit 40 at one end, and is coupled to the lift amount changing mechanism on the other side. The axial direction of the control shaft 30 is set to a direction orthogonal to the rotation shaft 26 of the motor 20. As shown in FIGS. 3 and 4, the coupling portion 32 provided at one end of the control shaft 30 is overlapped with the coupling portion 42 of the support frame 41 in a direction orthogonal to the control shaft 30. The coupling portions 32 and 42 are prevented from being separated from each other by a clip 46.

The transmission unit 40 includes a box-shaped support frame 41 and a roller 44 that is supported by the support frame 41 on the side opposite to the control shaft 30 so as to freely rotate forward and backward.
The cam shaft 52 of the drive cam 50 is inserted in the support frame 41 so as to be able to rotate forward and backward so as to be parallel to the rotation shaft 26 of the motor 20. On the outer peripheral surface of the drive cam 50, a cam surface 53 that is in sliding contact with the roller 44 is formed. As shown in FIG. 2, cam gears 54 and 56 are respectively fixed to both ends of the cam shaft 52 so as to be integrally rotatable. The motor gear 28 and the cam gear 54 mesh with each other to form a speed reduction mechanism. The rotation angle range of the cam gear 54 is limited by locking two protrusions (not shown) provided on the cam gear 54 to the locking members 58 and 59, respectively.

  The angle sensor 60 has a sensor gear 62 that meshes with the cam gear 56. The angle sensor 60 detects the rotation angle of a sensor rotating member (not shown) that rotates together with the sensor gear 62 using a hall element or the like. The angle sensor 60 is connected to the motor drive device 70 and transmits a rotation angle detection signal to the motor drive device 70.

  The motor drive device 70 includes an ECU 72 as a control circuit, an EDU 80 as a drive circuit, and the like. The ECU 72 receives detection signals from the angle sensor 60 and various detection signals such as the engine speed and the accelerator opening, generates a control signal based on the detection signals, and generates an engine ignition device and a fuel injection device. Control etc. The EDU 80 receives the control signal generated by the ECU 72, and energizes the motor 20 in accordance with the control signal.

  In such a valve lift adjusting device 2, when the motor 20 is rotated by energization from the EDU 80, the rotational torque of the motor 20 is transmitted to the drive cam 50 through the motor gear 28 and the cam gear 54. When the drive cam 50 rotates while being in sliding contact with the roller 44, the support frame 41 that supports the roller 44 reciprocates linearly with the control shaft 30 in the axial direction of the control shaft 30. At this time, the lift amount changing mechanism changes the maximum valve lift amount according to the axial position of the control shaft 30 that moves according to the cam profile of the cam surface 53 of the drive cam 50.

Next, the motor drive device 70 will be described in detail. In the following description, regarding the voltages of various digital signals, a high level in an on state is referred to as an H level, and a low level in an off state is referred to as an L level.
In the motor drive device 70, the ECU 72 shown in FIG. 5 is configured by an electric circuit such as a microcomputer, and is connected to the EDU 80 via a plurality of signal lines. The ECU 72 generates first to third control signals to be transmitted to the EDU 80 through the signal lines 74a, 74b, and 74c. Here, the first to third control signals are digital signals. For example, the duty ratio of the first control signal represents the ratio of the time t _{H when} the voltage is at the H level with respect to the period T as shown in FIG.

  Specifically, the ECU 72 determines whether the operating state of the motor 20 is forward rotation, reverse rotation, or stop when the current detection signal received from the EDU 80 through the signal line 74d represents a normal current. When the forward rotation of the motor 20 is determined, the ECU 72 sets the duty ratio of the first control signal to a value corresponding to the target rotational speed necessary for the forward rotation, as shown in the period α of FIG. The voltage of the second control signal and the voltage of the third control signal are set to H level and L level, respectively. When the reverse rotation of the motor 20 is determined, the ECU 72 sets the duty ratio of the first control signal to a value corresponding to the target rotational speed necessary for the reverse rotation as shown in the period β of FIG. The voltage of the signal and the voltage of the third control signal are set to L level and H level, respectively. Furthermore, when the stop of the motor 20 is determined, the ECU 72 sets the duty ratio of the first control signal to 0% and sets the voltages of the second and third control signals to L as shown in the period γ of FIG. Set to level.

  When the ECU 72 receives a current detection signal representing an overcurrent from the EDU 80, the ECU 72 checks the operating state of the engine and the like, and then sets the duty ratio of the first control signal as shown in the period δ of FIG. The voltage is set to 0%, and the voltages of the second and third control signals are both set to the L level.

As shown in FIG. 5, the EDU 80 of the motor drive device 70 includes a bridge unit 81, a reset unit 82, a circuit protection unit 83, and a drive signal generation unit 84.
The bridge portion 81 is configured by an H bridge circuit using the motor 20 as a load, and has two arms 85. In the bridge portion 81, one end of each arm 85 serving as a power supply path to the motor 20 is connected to the power source 86, and the other end of each arm 85 is grounded. In each arm 85, on both sides of the connection point 87 connected to the coil of the motor 20, a set of a switching element 88 and a parasitic diode (not shown) connected in parallel to the switching element 88 is provided. The switching element 88 of each arm 85 is composed of, for example, a MOS type field effect transistor or the like, and each gate is connected to the drive signal generation unit 84 and is switched on and off by the drive signal supplied from the drive signal generation unit 84. The All the switching elements 88 of the present embodiment are turned on when the drive signal, which is a digital signal, is at the H level, and are turned off when the drive signal is at the L level. In the following description, the switching elements 88 provided on the power supply 86 side from the connection point 87 in each arm 85 are provided on the ground side from the connection point 87 in the first and second switching elements 88a and 88b. The switching elements 88 are referred to as third and fourth switching elements 88c and 88d.

In the bridge part 81, the energization state to the motor 20 is switched according to the combination of on / off of the first to fourth switching elements 88a, 88b, 88c, 88d.
Specifically, when all of the first to fourth switching elements 88a, 88b, 88c, 88d are turned off, the motor 20 is not energized. Therefore, the motor 20 stops.

When the first and fourth switching elements 88a and 88d are turned on and the second and third switching elements 88b and 88c are turned off, the motor 20 is energized so as to apply a rotational torque in the normal rotation direction to the rotating shaft 26. The
When the second and third switching elements 88b and 88c are turned on and the first and fourth switching elements 88a and 88d are turned off, the motor 20 is energized so as to apply a rotational torque in the reverse direction to the rotary shaft 26. .
When the first and second switching elements 88a and 88b are turned on and the third and fourth switching elements 88c and 88d are turned off, the circulating current flows so that the residual voltage in the coil of the motor 20 decreases.

The reset unit 82 receives the second and third control signals through the signal lines 74b and 74c. The reset unit 82 is connected to the circuit protection unit 83, and monitors the voltages of the second and third control signals after receiving a current detection signal representing an overcurrent from the circuit protection unit 83. When the reset unit 82 detects that both of the voltages of the second and third control signals are L level during the monitoring, the reset unit 82 starts measuring the elapsed time t from the detection time. The reset unit 82, when the elapsed time t, as shown in the period of Figure 1 [delta] becomes a predetermined reset time t _RS, providing an internal reset signal to the circuit protection unit 83. Here, the reset time t _RS is set to about 1 second as a time necessary for sufficiently lowering the temperatures of the first to fourth switching elements 88a, 88b, 88c, 88d that have risen due to overcurrent, for example. It is remembered.

As shown in FIG. 5, the load resistance element 90 provided between the connection point 89 to the power source 86 and the first and second switching elements 88a and 88b in each arm 85 of the bridge portion 81 has a circuit protection. The part 83 is connected. Continuous addition intermittently circuit protection unit 83 for detecting the flow currents of the load resistance element 90 changes the processing contents in accordance with the magnitude relationship between the distribution current of the load resistance element 90 with a predetermined threshold value I _th. In this case, the threshold value _{I th} is set to, for example, 60A or the like that could lead to failure of the motor 20 are previously stored in EDU80.

Specifically circuit protection unit 83, when the circulation current of the load resistance element 90 is normal currents below the threshold I _th, the period of FIG. 1 alpha, beta, as shown in gamma, command to allow the energization of the motor 20 A signal (hereinafter referred to as a permission command signal) is supplied to the drive signal generator 84. At the same time, the circuit protection unit 83 transmits a current detection signal representing a normal current (hereinafter referred to as a normal current detection signal) to the ECU 72 through the signal line 74d.

When the flowing current of the load resistance element 90 becomes an overcurrent greater than or _equal to the threshold value Ith, the circuit protection unit 83 prohibits the energization of the motor 20 until an internal reset signal is given from the reset unit 82 as shown in the period δ of FIG. A command signal (hereinafter referred to as a prohibition command signal) to be sent is given to the drive signal generation unit 84. In addition, when the flowing current of the load resistance element 90 becomes an overcurrent, the circuit protection unit 83 resets a current detection signal (hereinafter referred to as an overcurrent detection signal) representing the overcurrent as shown in a period δ of FIG. The overcurrent detection signal is transmitted to the ECU 72 through the signal line 74d. In the ECU 72 that has received the overcurrent detection signal, the voltage of the second and third control signals is set to the L level after confirming the engine operating state and the like, so that the internal reset signal is generated by the reset unit 82 that detects the setting. It is given to the circuit protection unit 83 at the timing described above. By receiving this internal reset signal, the circuit protection unit 83 switches the command signal supplied to the drive signal generation unit 84 from the prohibition command signal to the permission command signal, as shown in FIG.

  The drive signal generator 84 receives the first to third control signals from the ECU 72 through the signal lines 74a, 74b, and 74c, and gives the drive signals to be given to the first to fourth switching elements 88a, 88b, 88c, and 88d, for example. Generate as shown in FIG. In the following description, the drive signal given to the first switching element 88a is the first drive signal, the drive signal given to the second switching element 88b is the second drive signal, and the drive signal given to the third switching element 88c is the third drive. The drive signal given to the signal and the fourth switching element 88d is called a fourth drive signal.

  Specifically, the drive signal generation unit 84 is given the permission command signal from the circuit protection unit 83, and when the voltage of the second control signal and the voltage of the third control signal become H level and L level, respectively, the period of FIG. As shown by α, the first to fourth drive signals are subjected to pulse width modulation. At this time, the drive signal generator 84 matches the duty ratio of the fourth drive signal with the duty ratio of the first control signal, the second drive signal rises later than the fall of the fourth drive signal, and the fourth drive signal The duty ratio of the second drive signal is changed so as to fall earlier than the rise. At the same time, the drive signal generator 84 fixes the duty ratio of the first drive signal to 100% and fixes the duty ratio of the third drive signal to 0%. Thus, in the period α in which the duty ratios of the first to fourth drive signals are set, the motor 20 can be energized so as to rotate the rotating shaft 26 in the normal direction.

  When the permission signal is given from the circuit protection unit 83 and the voltage of the second control signal and the voltage of the third control signal become L level and H level, respectively, the drive signal generation unit 84 is shown in the period β in FIG. Thus, the first to fourth drive signals are pulse width modulated. At this time, the drive signal generator 84 matches the duty ratio of the third drive signal with the duty ratio of the first control signal, the first drive signal rises later than the fall of the third drive signal, and the third drive signal The duty ratio of the first drive signal is changed so as to fall earlier than the rise. At the same time, the drive signal generator 84 fixes the duty ratio of the second drive signal to 100% and fixes the duty ratio of the fourth drive signal to 0%. Thus, in the period β in which the duty ratios of the first to fourth drive signals are set, the motor 20 can be energized so as to reverse the rotating shaft 26.

Even when the permission command signal is supplied from the circuit protection unit 83, the drive signal generation unit 84 is configured to output the first to third signals as shown in the period γ in FIG. All the duty ratios of the fourth drive signals are fixed to 0%. Thus, in the period γ during which the duty ratios of the first to fourth drive signals are set, energization to the motor 20 is stopped.
When the prohibition command signal is given from the circuit protection unit 83, the drive signal generation unit 84 fixes all the duty ratios of the first to fourth drive signals to 0% as shown in the period δ of FIG. Stop pulse width modulation of the first to fourth drive signals.

Here, a general overall operation of the motor driving device 70 will be reviewed.
When the flowing current of the load resistance element 90 becomes a normal current, the drive signal generation unit 84 receives a permission command signal from the circuit protection unit 83. Then, according to the duty ratio of the first control signal and the voltages of the second and third control signals, the drive signal generation unit 84 supplies the first to fourth switching elements 88a, 88b, 88c, 88d to the first to fourth switching elements 88a, 88b, 88c, 88d. Since the drive signal is subjected to pulse width modulation, the energization state of the motor 20 is switched.

When the flow current of the load resistance element 90 changes from a normal current to an overcurrent, the drive signal generation unit 84 receives a prohibition command signal from the circuit protection unit 83, and the ECU 72 and the reset unit 82 receive an overcurrent detection signal from the circuit protection unit 83. receive. Then, the drive signal generator 84 forcibly sets all the first to fourth drive signals applied to the first to fourth switching elements 88a, 88b, 88c, 88d to the L level, and the pulse widths of the first to fourth drive signals. In order to stop the modulation, power supply to the motor 20 is stopped. In addition, since the ECU 72 forcibly sets the voltages of the second and third control signals to the L level after confirming the engine operating state or the like, the reset unit 82 detects the internal reset signal after the reset time t _{RS has} elapsed since the detection of the forcible setting. Is supplied to the circuit protection unit 83. The circuit protection unit 83 that has received the internal reset signal provides a permission command signal to the drive signal generation unit 84. Therefore, the drive signal generation unit 84 that has received the permission command signal receives the first to fourth drive signal pulses. Resume width modulation.

  In the first embodiment described above, when overcurrent flows through the load resistance element 90 provided in the energization path to the motor 20, the energization drive of the motor 20 by the EDU 80 is stopped. At the same time, depending on the ECU 72 that has received the overcurrent detection signal from the EDU 80, the voltages of the second and third control signals are both forcibly set to the L level. 20 energization driving is resumed. The EDU 80 that has detected the overcurrent and has stopped the energization drive in this way outputs the second and third control signals among the first to third control signals necessary for switching the energization state to the motor 20. It can be used to return to the energization drive state. Therefore, there is no need to transmit a reset signal for returning the EDU 80 from the ECU 72 to the EDU 80 separately from the first to third control signals, so that the number of necessary signal lines between the EDU 80 and the ECU 72 is reduced. In the ECU 72 that controls the engine, the addition of terminals indicated by circles in FIG. 5 can be suppressed.

(Second embodiment)
The second embodiment of the present invention is a modification of the first embodiment, and the description of the components that are substantially the same as those of the first embodiment is omitted by providing the same reference numerals. FIG. 7 shows a motor drive device 200 according to the second embodiment.
In the motor drive device 200, the ECU 202 generates first and second control signals to be transmitted to the EDU 210 through the signal lines 204a and 204b.

Specifically, the ECU 202 determines whether the operation state of the motor 20 is forward rotation, reverse rotation, or stop when the current detection signal received from the EDU 210 through the signal line 204c represents a normal current. When the normal rotation of the motor 20 is determined, the ECU 202 sets the duty ratio of the first control signal to a value corresponding to the target rotational speed necessary for the normal rotation, as shown in the period α of FIG. The voltage of the two control signals is set to H level. When the reverse rotation of the motor 20 is determined, the ECU 202 sets the duty ratio of the first control signal to a value corresponding to the target rotational speed necessary for the reverse rotation as shown in the period β of FIG. The signal voltage is set to L level. Furthermore, when the stop of the motor 20 is determined, the ECU 72 sets the duty ratio of the first control signal to 0% as shown in the period γ in FIG.
When the ECU 202 receives a current detection signal indicating an overcurrent from the EDU 200, the ECU 202 checks the operating state of the engine and the like, and then sets the duty ratio of the first control signal as shown in a period δ in FIG. 8 until a predetermined time elapses, for example. Set to 0%.

The reset unit 212 of the EDU 210 receives the first control signal through the signal line 204a. The reset unit 212 is connected to the circuit protection unit 213, and monitors the duty ratio of the first control signal after receiving the overcurrent detection signal from the circuit protection unit 213. The reset unit 212 detects that the duty ratio of the first control signal becomes 0% during the monitoring, that is, in the present embodiment, the voltage of the first control signal is L level for the period T or more of the first control signal. When it is detected that it has become, the elapsed time t from the detection time is started to be measured. Then, as shown in FIG. 8, the reset unit 212 gives an internal reset signal to the circuit protection unit 213 when the elapsed time t reaches a predetermined reset time t _RS ′. Here, the reset time t _RS ′ is set to about 1 second as a time necessary for sufficiently lowering the temperatures of the first to fourth switching elements 88a, 88b, 88c, 88d that have been raised due to overcurrent, for example. Stored in advance.

When the flow current of the load resistance element 90 becomes a normal current, the circuit protection unit 213 of the EDU 210 supplies a permission command signal to the drive signal generation unit 214 as shown in periods α, β, and γ in FIG. The detection signal is transmitted to the ECU 202 through the signal line 204c.
When the flowing current of the load resistance element 90 becomes an overcurrent, the circuit protection unit 213 gives a prohibition command signal to the drive signal generation unit 214 until an internal reset signal is given from the reset unit 212 as shown in the period δ of FIG. . In addition, when the flowing current of the load resistance element 90 becomes an overcurrent, the circuit protection unit 213 provides an overcurrent detection signal to the reset unit 212 and outputs the overcurrent detection signal as shown in a period δ of FIG. It transmits to ECU202 through the line 204c. In the ECU 202 that has received the overcurrent detection signal, the duty ratio of the first control signal is set to 0% after confirming the engine operating state or the like. It is given to the circuit protection unit 213 at timing. By receiving this internal reset signal, the circuit protection unit 213 changes the command signal supplied to the drive signal generation unit 214 from the prohibition command signal to the permission command signal, as shown in FIG.

The drive signal generator 214 of the EDU 210 receives the first and second control signals from the ECU 202 through the signal lines 204a and 214b, and generates the first to fourth drive signals as shown in FIG.
Specifically, in the drive signal generation unit 214 to which the permission command signal is given from the circuit protection unit 213, the voltage of the first control signal is switched during the period T as shown in the period α in FIG. When the voltage of the two control signals becomes H level, the duty ratios of the first to fourth drive signals are set as in the case of the period α of the first embodiment. In addition, the drive signal generation unit 214 to which the permission command signal is given from the circuit protection unit 213 changes the voltage of the first control signal during the period T as shown in the period β of FIG. When the voltage becomes the L level, the duty ratios of the first to fourth drive signals are set as in the case of the period β in the first embodiment. As described above, the motor 20 can be energized so as to rotate the rotating shaft 26 forward or backward during the periods α and β of the present embodiment.

Even when the permission command signal is given from the circuit protection unit 83, the drive signal generation unit 214, when the voltage of the first control signal is held at the L level for the period T or more as shown in the period γ of FIG. The duty ratios of the first to fourth drive signals are all fixed at 0%. Therefore, energization of the motor 20 is stopped during the period γ of the present embodiment.
When the prohibition command signal is given from the circuit protection unit 83, the drive signal generation unit 214 fixes the duty ratios of the first to fourth drive signals to 0% as shown in the period δ of FIG. Stop pulse width modulation of the first to fourth drive signals.

Here, the characteristic overall operation of the motor drive device 200 will be reviewed.
When the flowing current of the load resistance element 90 becomes a normal current, the drive signal generation unit 214 receives a permission command signal from the circuit protection unit 213. Then, since the drive signal generation unit 214 performs pulse width modulation on the first to fourth drive signals according to the duty ratio of the first control signal and the voltage of the second control signal, the energization state of the motor 20 is switched.

When the flow current of the load resistance element 90 changes from a normal current to an overcurrent, the drive signal generation unit 214 receives a prohibition command signal from the circuit protection unit 213, and the ECU 202 and the reset unit 212 receive an overcurrent detection signal from the circuit protection unit 213. receive. Then, since the drive signal generation unit 214 forcibly sets all the voltages of the first to fourth drive signals to the L level and stops the pulse width modulation of the first to fourth drive signals, the energization to the motor 20 is stopped. . In addition, since the ECU 202 forcibly sets the duty ratio of the first control signal to 0% after confirming the engine operating state or the like, the reset unit 212 generates an internal reset signal after the reset time t _RS ′ has elapsed since the detection of the forcible setting. The protection unit 213 is given. The circuit protection unit 213 that has received the internal reset signal provides a permission command signal to the drive signal generation unit 214, so that the drive signal generation unit 214 that has received the permission command signal receives the first to fourth drive signal pulses. Resume width modulation.

  In the second embodiment described above, when an overcurrent flows through the load resistance element 90 provided in the energization path to the motor 20, the energization drive of the motor 20 by the EDU 210 is stopped. At the same time, depending on the ECU 202 that has received the overcurrent detection signal from the EDU 210, the duty ratio of the first control signal is forcibly set to 0%. Therefore, the energization of the motor 20 by the EDU 210 is performed after a predetermined time has elapsed since the forcible setting. Driving resumes. The EDU 210 that has detected the overcurrent and has stopped the energization drive in this way uses the first control signal among the first and second control signals necessary for switching the energization state to the motor 20. Then, it is returned to the energization drive state. Therefore, it is not necessary to transmit a reset signal for returning EDU 210 from ECU 202 to EDU 210 separately from the first and second control signals. Moreover, fewer control signals are required to switch the energization state of the motor than in the first embodiment. According to such a second embodiment, the number of signal lines required between the EDU 210 and the ECU 202 can be sufficiently reduced. Therefore, in the ECU 202 that controls the engine, an additional terminal indicated by a circle in FIG. 7 is added. Can be suppressed.

Although a plurality of embodiments of the present invention have been described above, the present invention should not be construed as being limited to those embodiments.
For example, in the above-described embodiments, the ECUs 72 and 202 as control circuits are provided with an engine control function, but the ECUs 72 and 202 may not be provided with an engine control function.

Further, in the above-described plurality of embodiments, the example in which the present invention is applied to the valve lift adjusting device 2 including the EDUs 80 and 210 that energize and drive the DC brush motor 20 as a drive circuit has been described. On the other hand, you may apply this invention to the valve lift adjustment apparatus provided with the drive circuit which energizes and drives a well-known motor, such as a brushless motor. When the present invention is applied to a valve lift adjustment device having a drive circuit for energizing and driving a brushless motor, for example, a bridge portion having arms with the number of columns corresponding to the number of phases of the brushless motor is provided in the drive circuit. The switching element of each arm is turned on / off.
Furthermore, in the above-described embodiments, the example in which the present invention is applied to the valve lift adjusting device 2 that adjusts the maximum valve lift amount for the intake valve has been described. On the other hand, you may apply this invention to the valve lift adjustment apparatus which adjusts the maximum valve lift amount about an exhaust valve.

It is a characteristic view for demonstrating the action | operation of the motor drive device by 1st embodiment. It is a fragmentary sectional perspective view which shows the principal part of the valve lift adjustment apparatus by 1st embodiment. It is a perspective view which shows the principal part of the actuator by 1st embodiment. It is a side view which shows the principal part of the actuator by 1st embodiment. It is a block diagram which shows the motor drive device by 1st embodiment. It is a characteristic view for demonstrating the action | operation of the motor drive device by 1st embodiment. It is a block diagram which shows the motor drive device by 2nd embodiment. It is a characteristic view for demonstrating the action | operation of the motor drive device by 2nd embodiment.

Explanation of symbols

2 Valve lift adjusting device, 10 Actuator, 20 Motor, 26 Rotating shaft, 30 Control shaft, 40 Transmission unit, 50 Driving cam, 60 Angle sensor, 70, 200 Motor driving device, 72, 202 ECU (control circuit), 80, 210 EDU (Drive circuit), 74a, 74b, 74c, 74d, 204a, 204b, 204c Signal line, 81 Bridge unit, 82, 212 Reset unit, 83, 213 Circuit protection unit, 84, 214 Drive signal generation unit

Claims (3)

A valve lift adjustment device that adjusts the maximum valve lift amount in an internal combustion engine using the rotational torque of a motor,
When the motor is rotated forward, the duty ratio of the first control signal is set to a value necessary for the forward rotation, and the voltage of the second control signal and the voltage of the third control signal are respectively set to a high level and a low level. When rotating the motor, the duty ratio of the first control signal is set to a value necessary for the reverse rotation, and the voltage of the second control signal and the voltage of the third control signal are set to a low level and a high level, respectively. A control circuit to be set;
The first control signal, the second control signal, and the third control signal are received from the control circuit, and the duty ratio of the first control signal, the voltage of the second control signal, and the voltage of the third control signal are set. A drive circuit for switching the energization state of the motor in response,
With
When the drive circuit detects an overcurrent in the energization path to the motor, the drive circuit stops the energization drive of the motor and transmits an overcurrent detection signal to the control circuit, and further receives the overcurrent detection signal. The energization driving of the motor is resumed after a predetermined time has elapsed since the control circuit detects that both the voltage of the second control signal and the voltage of the third control signal are set to a low level. Valve lift adjustment device. A valve lift adjustment device that adjusts the maximum valve lift amount in an internal combustion engine using the rotational torque of a motor,
When the motor is rotated forward, the duty ratio of the first control signal is set to a value necessary for the forward rotation and the voltage of the second control signal is set to a high level, and when the motor is rotated reversely, A control circuit for setting the duty ratio of the control signal to a value necessary for the reverse rotation and setting the voltage of the second control signal to a low level;
A drive circuit that receives the first control signal and the second control signal from the control circuit, and switches the energization state of the motor according to the duty ratio of the first control signal and the voltage of the second control signal;
With
When the drive circuit detects an overcurrent in the energization path to the motor, the drive circuit stops the energization drive of the motor and transmits an overcurrent detection signal to the control circuit, and further receives the overcurrent detection signal. A valve lift adjusting device, wherein after a predetermined time has elapsed since the control circuit detected that the duty ratio of the first control signal was set to 0%, the energization drive of the motor is resumed.   The valve lift adjusting device according to claim 1, wherein the control circuit has a function of controlling the internal combustion engine.

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