JP4922661B2 - Air gap estimation device for electromagnetic actuator - Google Patents

Description

  The present invention relates to an air gap estimation device for an electromagnetic actuator used in a torque transmission mechanism or the like of an electronically controlled four-wheel drive vehicle or the like.

  For example, a torque transmission mechanism or the like such as an electronically controlled four-wheel drive vehicle includes a pair of left and right planetary gear sets and a pair of brake mechanisms for variably controlling the torque of a sun gear connected to each planetary gear set. Each brake mechanism includes a wet multi-plate brake and an electromagnetic actuator that operates the multi-plate brake.

  The electromagnetic actuator is provided in a cylindrical inner space, and is arranged such that a core (yoke) made of a magnetic material and a core and a cylindrical inner space are opposed to each other with a predetermined air gap in the axial direction. The armature is made of a material, an exciting coil inserted into an annular space between the core and the armature, a piston connected to the armature, and the like.

  When a current is applied to the exciting coil, a magnetic path is formed in the magnetic circuit composed of the core, the armature, and the air gap, and an electromagnetic force is generated in the air gap between the core and the armature. This electromagnetic force attracts the armature to the core to generate thrust. Due to this thrust, the piston integrally connected to the armature presses the multi-plate brake, and brake torque is generated by the frictional force generated in the multi-plate brake. The torque of the axle connected to the multi-plate brake is controlled by this brake torque.

  The ECU equipped with the microcomputer calculates the target current value to be passed through the left and right electromagnetic solenoids in order to generate the braking torque corresponding to the running state such as the turning direction and steering force or steering angle of the vehicle. Is controlled so that the exciting currents flowing through the respective target current values match each other, and the output torque to the left and right rear axles is variably controlled.

  In order to converge the excitation current value flowing through the excitation coil to the target current value at high speed, a target current value corresponding to the brake torque corresponding to the running state of the vehicle is calculated by the ECU. The ECU performs PWM control according to the difference between the target current value and the actual current flowing through the exciting coil, and supplies the PWM drive signal to the control terminal of the switching element.

  The switching element is provided in series with the exciting coil between the battery power source and the ground, and is turned on / off according to the high / low of the PWM drive signal applied to the control terminal, thereby controlling the current of the exciting coil.

  A current return diode (flywheel diode) is provided in parallel with the excitation coil. When the switching element is turned off, the current return diode is turned on by the counter electromotive force generated in the excitation coil, and a reflux current is passed through the excitation coil. To smooth.

  The actual current flowing through the exciting coil is detected, the actual current is compared with the target current by the PID calculation means, and PWM control is performed so that the actual current matches the target current value.

  In this way, the pulse width of the PWM drive signal applied to the switching element is controlled so that the current value of the exciting coil converges to the target current value at high speed.

  On the other hand, the air gap between the core and the armature fluctuates due to wear due to the frictional force of the multi-plate brake, and the thrust increases when the air gap narrows. As described above, when a current flows through the exciting coil, a magnetic flux is generated in the magnetic circuit. Since the thrust applied to the air gap is determined by the magnetic flux, it is necessary to accurately control the thrust based on the magnetic flux detection.

There is Patent Document 1 as a prior art document for accurately controlling thrust based on magnetic flux detection. In Patent Document 1, a search coil is disposed in a magnetic path through which a magnetic flux passes, an actual current having a pulse waveform is caused to flow through an exciting coil, and an electromotive force generated in the search coil due to a change in the magnetic flux generated in the magnetic path of the magnetic circuit. It is disclosed that measurement is performed, magnetic flux is calculated, and thrust is calculated based on the magnetic flux of the calculation result, the air gap cross-sectional area, and the permeability of the core and the like.
JP 2002-303660 A

  However, in Patent Document 1, since the magnetic flux is detected using the search coil as described above, there is a problem that the cost of parts related to the search coil increases. In addition, since the electromotive force generated in the search coil has a small number of turns with respect to the exciting coil, a large magnetic energy cannot be output.

  As a result, the electromotive force generated in the search coil varies due to the influence of spike noise caused by radio waves from a radio or mobile phone used in the vehicle. When the search coil output electromotive force is integrated, the spike noise value etc. in the electromotive force are also integrated, so that the magnetic flux value calculated from the integrated value changes greatly, resulting in a large error in the estimated thrust value. there were.

  In addition, the formation of magnetic flux in the exciting coil has variations due to variations in the shapes of the yoke and the armature constituting the magnetic flux circuit. Furthermore, when the air gap length changes, the magnetic resistance related to the air gap of the magnetic circuit changes and the magnetic flux formation of the magnetic circuit also changes greatly, and the search coil cannot be made the optimal layout for magnetic flux detection. There was a point.

  As described above, the method of estimating the thrust by calculating the magnetic flux of the magnetic circuit has a problem that the estimation error becomes large.

  On the other hand, in the electromagnetic actuator as described above, there is a relationship that the thrust increases as the air gap decreases if the excitation currents flowing through the excitation coils are the same. Therefore, if the air gap between the core and the armature can be estimated, a desired thrust can be obtained by controlling the excitation current according to the size of the air gap.

  Therefore, an object of the present invention is to provide an air gap estimation device for an electromagnetic actuator capable of estimating an air gap between a core and an armature with a simple configuration.

According to the first aspect of the present invention, there is provided an air gap estimation device for an electromagnetic actuator having a core having an exciting coil and an armature disposed so as to face the core via an air gap. Vehicle stop state detecting means for detecting the vehicle, a constant voltage applying means for applying a predetermined DC constant voltage to the exciting coil when the vehicle stop state is detected by the vehicle stop state detecting means, and the constant voltage applying means When measuring the time constant of the exciting coil based on the rising time or the falling time until the rising current or falling current of the exciting coil reaches a specified value when the DC constant voltage is applied to the exciting coil in Constant measuring means, and inductance calculating means for calculating the inductance of the exciting coil from the time constant and the resistance of the exciting coil , Based on the inductance calculated by the inductance calculation means, an air gap estimation apparatus of the electromagnetic actuator, characterized by comprising an air gap estimation means for estimating an air gap, is provided.

According to the second aspect of the present invention, the electromagnetic brake is fastened by energizing the excitation coil, and having the core having the excitation coil and the armature arranged to face the core through the air gap. An air gap estimation device for an electromagnetic actuator, wherein the excitation is detected when the non-engagement detection means for detecting the non-engagement of the electromagnetic brake and the non-engagement detection means detects the non-engagement time of the electromagnetic brake. a constant voltage applying means for applying a predetermined DC constant voltage to the coil, the upon applying the direct current constant voltage to the exciting coil at a constant voltage applying means, the rising current or falling current in the exciting coil specified value a constant measuring means when measuring a time constant of the exciting coil based on the rise time or the fall time until, with the time constant of the exciting coil Inductance calculation means for calculating the inductance of the exciting coil from the resistance, and air gap estimation means for estimating an air gap based on the inductance calculated by the inductance calculation means A gap estimation device is provided.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the electromagnetic detection apparatus further comprises temperature detecting means for detecting the temperature of the exciting coil, and inductance correcting means for correcting the inductance based on the temperature of the exciting coil. An air gap estimation device for an actuator is provided.

  According to the first aspect of the present invention, since it is not necessary to estimate the air gap based on the magnetic flux generated in the exciting coil, the search coil can be eliminated from the electromagnetic actuator, and the cost of the electromagnetic actuator can be reduced.

In addition, when a stop state of the vehicle is detected, a predetermined DC constant voltage is applied to the excitation coil, and based on the rise time or fall time until the rise current or fall current of the excitation coil reaches a specified value. The air gap of the electromagnetic actuator is estimated by measuring the time constant of the excitation coil, and this estimated air gap can be used for the control of the electromagnetic actuator in the subsequent driving state of the vehicle, eliminating the search coil from the electromagnetic actuator. In spite of this simple configuration, there is an excellent effect that it is possible to improve the current rising characteristic in the PWM duty drive of the solenoid when the electromagnetic actuator is driven in the vehicle running state. In addition, when a stop state of the vehicle is detected, a predetermined DC constant voltage is applied to the excitation coil, and based on the rise time or fall time until the rise current or fall current of the excitation coil reaches a specified value. Since the air gap of the electromagnetic actuator need only be estimated at least once by measuring the time constant of the exciting coil, the air gap of the electromagnetic actuator can be estimated without imposing a burden on the processing circuit, and It has an excellent effect that accurate time constant measurement can be performed in a stable state. Furthermore, since the air gap is estimated when the vehicle is stopped, the electromagnetic brake is not engaged, and even if the DC brake is applied to apply the DC constant voltage to the excitation coil to estimate the air gap, the vehicle is stopped. Therefore, the air gap can be estimated stably.

  According to the invention described in claim 2, the air gap can be estimated when the electromagnetic brake is not engaged, and the same effect as in claim 1 can be achieved. When the electromagnetic brake is not engaged, it may include the vehicle stop state and the vehicle running state. However, when estimating the air gap when the electromagnetic brake is not engaged in the vehicle running state, the electromagnetic brake is applied as a constant voltage applied to the excitation coil. It is necessary to apply a constant voltage that is low enough not to be fastened.

  According to the third aspect of the present invention, since the inductance is corrected based on the temperature of the exciting coil, it is possible to accurately estimate the air gap.

  FIG. 1 is a diagram showing a schematic configuration of a power transmission device for a four-wheel drive vehicle based on a front engine / front drive (FF) vehicle to which the magnetic flux detection device or the air gap estimation device of the present invention can be applied.

  As shown in FIG. 1, the power transmission system includes a front differential device 6 in which power from an engine 2 disposed in front of the vehicle is transmitted from an output shaft 4a of a transmission 4, and power from the front differential device 6 is propeller shaft. 8 mainly includes a speed increasing device (transmission device) 10 transmitted through 8, a rear differential device 12 to which power from the speed increasing device 10 is transmitted, and an ECU 13 for performing vehicle running control and the like.

  The front differential device 6 has a conventionally known structure, and the power from the output shaft 4a of the transmission 4 is transmitted to the left and right front wheel drive shafts 20 and 22 via the plurality of gears 14 and the output shafts 16 and 18 in the differential case 6a. By transmitting, each front wheel is driven.

  As will be described later, the rear differential device 12 includes a pair of planetary gear sets and a pair of electromagnetic actuators for controlling the fastening of a multi-plate brake mechanism (multi-plate clutch mechanism), and controls the electromagnetic actuator. By transmitting power to the left and right rear wheel drive shafts 24 and 26, the rear wheels are driven.

  FIG. 2 is a sectional view of the speed increasing device (transmission device) 10 and the rear differential device 12 disposed on the downstream side of the speed increasing device 10. The speed increasing device 10 includes an input shaft 30 rotatably mounted in a casing 28 and an output shaft (hypoid pinion shaft) 32.

  The speed increasing device 10 further includes an oil pump subassembly 34, a planetary carrier subassembly 38, a direct coupling clutch subassembly 40, and a speed change brake 42.

  The rear differential device 12 provided on the downstream side of the speed increasing device 10 has a hypoid pinion gear 44 formed at the tip of the hypoid pinion shaft 32.

  The hypoid pinion gear 44 meshes with the hypoid ring gear 48, and the power from the hypoid ring gear 48 is input to the ring gears of the planetary gear sets 50A and 50B provided on the left and right.

  The sun gears of the planetary gear sets 50A and 50B are rotatably mounted around the left rear axle 24 and the right rear axle 26. The planetary carriers of the planetary gear sets 50A and 50B are fixed to the left rear axle 24 and the right rear axle 26. A planet gear carried on the planetary carrier meshes with the sun gear and the ring gear.

  The left and right planetary gear sets 50A and 50B are connected to an electromagnetic brake mechanism 51 provided for variably controlling the torque of the sun gear. The electromagnetic brake mechanism 51 includes a wet multi-plate brake 52 and an electromagnetic actuator 56 that operates the multi-plate brake 52.

  The brake plate of the wet multi-plate brake 52 is fixed to the casing 54, and the brake disc is fixed to the sun gears of the planetary gear sets 50A and 50B.

  The electromagnetic actuator 56 has a ring-shaped core (yoke) 58 made of a magnetic material having an annular groove, an annular excitation coil 60 inserted into the annular groove of the ring-shaped core 58, and a predetermined gap in the ring-shaped core 58. A ring-shaped armature 62 made of a magnetic material facing each other and an annular piston 64 connected to the armature 62 are configured.

  When an exciting current is passed through the exciting coil 60, the armature 62 is attracted to the core 58 by the magnetic flux generated in the magnetic circuit by the exciting current flowing through the exciting coil 60, and thrust is generated. Due to this thrust, the piston 64 integrally connected to the armature 62 presses the multi-plate brake 52, thereby generating a brake torque.

  As a result, the sun gears of the planetary gear sets 50A and 50B are fixed to the casing 54, respectively, and the driving force of the hypoid pinion shaft 32 passes through the ring gear, planet gear, and planet carrier of the planetary gear sets 50A and 50B. 26.

  In this way, by controlling the exciting current flowing through the exciting coil 60, the driving force of the input shaft 30 is increased in the directly connected state or with the speed increasing device 10, and is arbitrarily distributed to the left and right rear axles 24, 26. And optimal turning control can be realized.

  As described above, in order to obtain the same thrust, a larger excitation current is required as the air gap becomes larger. Therefore, if the air gap can be estimated by an appropriate method, the magnitude of the excitation current that generates the required thrust can be known.

  Hereinafter, an air gap estimation device for an electromagnetic actuator according to an embodiment of the present invention will be described with reference to FIGS. 3 to 13. In the present invention, a constant voltage is applied to the exciting coil, the inductance of the exciting coil is calculated based on the current rising time or falling time and the exciting coil resistance value, and the air gap between the core and the armature is estimated.

In the RL series circuit of FIG. 3, when the voltage is E, the coil resistance is R, and the coil inductance is L, the current i is
i = E / R (1-e- ^{(R / L) t} )
= I (1-e- ^{t / τ} )
Here, I = E / R, L / R = τ (time constant).

  FIG. 4 is a time chart when the current rises when a constant voltage is applied to the coil, and FIG. 5 is a time chart when the current falls.

In FIG. 4, the slope of the tangent at the origin is
| Di / dt | _{t = 0} = E / Rτ, | di ′ / dt | _{t = 0} = 1 / τ
According to the above principle, the inductance L is calculated as follows.

When the switch is turned on at t = 0, i = E / R (1-exp (−R / L * t)).
L = R * time constant = R * (the time required for the current value to rise to E / R * 0.632)
Next, an air gap estimation method according to an embodiment of the present invention will be described with reference to the flowcharts of FIGS. First, the detection condition is checked in step S10 of FIG. Details of this detection condition are shown in the flowchart of FIG.

  In step S30 of FIG. 7, it is determined whether or not the detection of inductance has been completed. If it has not been completed, the process proceeds to step S31 to determine whether or not the vehicle speed is zero.

  If it is determined in step S31 that the vehicle speed is 0, that is, the vehicle is in a stopped state, the process proceeds to step S32 to determine whether or not the voltage value of the constant voltage applied when measuring the time constant is within the specified range. To do. Here, when the vehicle is stopped, the electromagnetic brake mechanism 51 is in a non-engaged state, the wheel rotation speed is 0, and the gear position is preferably set to P or N.

  If it is determined that the voltage value is within the specified range, the process proceeds to step S33 to determine whether or not the brake is on. The reason for checking the brake is that it is desired to detect the inductance of the exciting coil when the vehicle is completely stopped.

  If it is determined in step S33 that the brake is on, the process proceeds to step S34 to determine whether the engine speed is equal to or greater than a certain value. When the engine speed is greater than or equal to a certain value, the inductance can be detected (step S35).

  If step S30 is affirmative and steps S31 to S34 are negative, this process ends.

  Referring to FIG. 8, a flowchart of detection conditions of another embodiment is shown. First, it is determined whether or not the detection of inductance is completed in step S40. If not completed, the process proceeds to step S41 to determine whether or not the electromagnetic brake mechanism 51 is not engaged.

  When the electromagnetic brake mechanism 51 is not engaged, the electromagnetic brake mechanism 51 is engaged and drive force distribution is not performed, and includes a vehicle stop state and an FF drive mode state.

  If it is determined in step S41 that the electromagnetic brake mechanism 51 is in the non-engaged state, the process proceeds to step S42 to determine whether or not the voltage value of the constant voltage applied when measuring the time constant is within the specified range.

  It should be noted here that when the air gap is estimated in the FF drive state, it is necessary to select a low constant voltage that does not engage the electromagnetic brake mechanism 51 even when a constant voltage is applied to the exciting coil. It is.

  If it is determined in step S42 that the voltage value is within the specified range, the process proceeds to step S43 to determine whether or not the engine speed is equal to or greater than a certain value. When the engine speed is equal to or greater than a certain value, the inductance can be detected (step S44). If step S40 is affirmative and steps S41 to S43 are negative, this process ends.

  When the detection condition check is completed in this way, the inductance of the exciting coil is detected in step S11 of FIG. This inductance detection step is shown in the flowchart of FIG.

  The inductance detection method of FIG. 9 is a method of calculating the inductance with the current rise time. First, in step S50, the current flowing through the exciting coil 60 during normal driving force control is stopped.

  Next, the process proceeds to step S51, where a constant voltage is applied to the exciting coil 60, and a time (time constant) until the current value becomes a specified value, that is, 0.632 times the maximum current value, is calculated (step S52).

  Next, the process proceeds to step S53, and the inductance L of the exciting coil 60 is calculated from the resistance value of the exciting coil 60 and the time constant τ from L = Rτ.

  When the detection of the inductance is completed in step S11 of FIG. 6, the process proceeds to step S12, and the temperature estimated from the resistance value of the exciting coil 60 is compared with the oil temperature of the wet multi-plate brake 52.

  In general, the resistance and temperature of a coil wound with a copper wire are in a proportional relationship as shown in FIG. Therefore, the temperature of the exciting coil can be detected by measuring the resistance of the exciting coil 60.

  Next, it is determined whether or not the difference between the temperature of the exciting coil 60 estimated from the resistance value and the oil temperature exceeds a predetermined threshold, for example, 50 ° C. in step S13. If it is determined that the threshold value has been exceeded, it cannot be said that the environment is suitable for air gap detection, and thus this processing is terminated.

  If it is determined in step S13 that the threshold value has not been exceeded, the process proceeds to step S14 to determine whether the inductance value detected in step S11 is appropriate. That is, the validity of the inductance is determined by the inductance validity determination flowchart of FIG.

  In step S60 of FIG. 10, the upper limit of the inductance is checked. In step S61, it is determined whether or not the upper limit value is exceeded. If it is determined that the upper limit value is exceeded, the process proceeds to step S65 and the inductance value is discarded. Increment.

  If it is determined in step S61 that the value does not exceed the upper limit value, the lower limit value of the inductance is checked in step S62, and it is determined whether or not the lower limit value of the inductance is lower in step S63.

  If it is determined that the value is below the lower limit value, the inductance value is abandoned in step S65, and the failure counter is incremented. If it is determined that the value does not fall below the lower limit value, it is determined that the inductance value is appropriate in step S64.

  If it is determined in step S14 in FIG. 6 that the inductance value is appropriate, the process proceeds to step S15, and the temperature of the exciting coil 60 is determined from the coil ambient temperature, that is, the oil temperature of the wet multi-plate brake 52 and the resistance value of the exciting coil 60. And the inductance value detected in step S11 is temperature-corrected.

  Specifically, since the inductance of the exciting coil 60 varies with temperature and exciting current, a table as shown in FIG. 12 is created by varying the temperature and exciting current through experiments. In FIG. 12, the straight line A is the temperature and inductance of the exciting coil 60 when the exciting current is 1 ampere (A), the straight line B is 3 amperes (A), and the straight line C is 5 amperes (A). Shows the relationship.

  Therefore, if the exciting current at the time of detecting the inductance of the exciting coil 60 is 1 ampere (A), the inductance can be detected from the temperature of the exciting coil 60 based on the straight line A.

  When the detection of the inductance after temperature correction is thus completed, the air gap can be estimated from the inductance-air gap table shown in FIG.

  Next, the process proceeds to step S16, the current response of the exciting coil 60 is adjusted by the detected inductance, and the current control amount of the exciting coil 60 is adjusted from the air gap detected in step S17. Details of step S17 will be described later.

  If it is determined in step S14 that the inductance value is not valid, the process proceeds to step S18 to abandon this inductance value and increment the failure counter. This step S18 is the same step as step S65 of FIG.

  In step S19, it is determined whether or not the failure counter exceeds a threshold value. If it is determined that the counter exceeds the threshold value, the process proceeds to step S20 to display an alarm signal on a car navigation system or an instrument panel meter.

  Next, with reference to FIGS. 14 to 17, a method for controlling the excitation current flowing through the excitation coil 60 from the air gap estimated by the air gap estimation method of the present invention will be described.

  FIG. 14 is an excitation coil 60 and peripheral circuit diagram for controlling the excitation current flowing in the excitation coil 60 of the electromagnetic actuator 56 in FIG. As shown in FIG. 14, the electromagnetic solenoid 70 includes a switch means (first switch means) 80, a flywheel diode (second switch means) 82, and an exciting coil 60.

  The first switch means 80 is a switch for turning on / off the supply of current from the battery power supply 90 to the exciting coil 60, and according to the high level / low level of the PWM drive signal applied to the control electrode. On / off, for example, an N-channel FET (hereinafter abbreviated as FET).

  The FET 80 and the exciting coil 60 are connected in series between the battery power supply 90 and the ground. For example, the FET 80 has a drain connected to a battery power supply 90 having a predetermined positive voltage, for example, 12V, and a source connected to one end (hereinafter referred to as a first end) of the exciting coil 60. A PWM drive signal is applied to the gate.

  The flywheel diode 82 is connected in parallel with the exciting coil 60. For example, the diode 82 has an anode connected to the ground and a cathode connected to the first end of the exciting coil 60.

  When the FET 80 is turned off, the flywheel diode 82 is forward-biased by the back electromotive force generated at both ends of the exciting coil 60 and is turned on to flow a reflux current a through the exciting coil 60 as shown in FIG. The flywheel diode 82 is reverse biased and turned off when the FET 80 is turned on.

  The ratio of the high level time of the PWM drive signal to a certain clock cycle is called the duty ratio. When the PWM drive signal is at a high level, the FET 80 is turned on, an exciting current flows through the exciting coil 60, and the exciting current corresponding to the duty ratio% increases.

  Further, when the PWM drive signal is at a low level, the FET 80 is turned off, back electromotive force is generated at both ends of the exciting coil 60, and the return current a flows. On the other hand, when the duty ratio becomes 0, it decreases until the return current a becomes 0.

  The exciting coil 60 has a first end connected to the source of the FET 80 and the other end (hereinafter referred to as a second end) connected to the ground via a resistor 260 provided in a current detecting means 122 described later. A current flows from the battery power supply 90 to the ground through the FET 80, the exciting coil 60 and the resistor 260. Thus, the search coil is eliminated from the electromagnetic actuator 56.

  The ECU 13 performs control for torque distribution according to the traveling state of the vehicle such as the turning direction, the steering angle, the throttle opening degree, and the vehicle speed. The ECU 13 executes a program that functions as the electromagnetic actuator control means 100 that controls the electromagnetic actuator 56 so that the brake torque generated by the electromagnetic actuator 56 is optimized in accordance with the traveling state.

  FIG. 15 is a functional block diagram of the electromagnetic actuator control means 100 according to the embodiment of the present invention. As shown in FIG. 15, the electromagnetic actuator control means 100 includes an air gap length estimation means 110, a target transmission torque calculation means 112, a target control current value calculation means 114, a PID calculation means 116, and a selection means according to the present invention. 118, PWM drive signal generation means 120, and current detection means 122.

  The target transmission torque calculation means 112 in FIG. 15 is output from a turning direction, a steering angle output from a steering angle sensor (not shown), a throttle opening output from a throttle opening sensor (not shown), a vehicle speed sensor (not shown), and the like. A target transmission torque to be distributed to the left and right rear wheel axles 24 and 26 is calculated according to the running state of the vehicle.

  FIG. 16 is a functional block diagram of the target control current value calculation means 114. As shown in FIG. 16, the target control current value calculation unit 114 includes a target control current conversion map 250 and a target control current conversion unit 252.

  In the target control current conversion map 250, target control current values corresponding to combinations of target transmission torques and air gaps are stored in advance. This map 250 is created by obtaining the brake torque (target transmission torque) by the thrust with respect to the target control current value in each air gap by the experiment of the electromagnetic actuator 56.

  The target control current conversion means 252 responds by referring to the target control current conversion map 250 from the combination of the air gap length stored in the storage means (not shown) and the target transmission torque calculated by the target transmission torque calculation means 112. The target control current value is converted.

  The PID calculation means 116 in FIG. 15 determines the duty ratio of the PWM drive signal so that the actual current value detected by the current detection means 122 converges to the target current value. That is, according to the difference between the actual current detected by the current detection means 122 and the target current value, if the target value is larger than the actual current, the target value is smaller than the actual current so that the actual current increases. If so, the duty ratio is determined so that the actual current is maintained if the target value matches the actual current so that the actual current decreases.

  The selection unit 118 selects one of the effective duty ratios output from the air gap length estimation unit 110 and the PID calculation unit 116 and outputs the selected duty ratio to the PWM drive signal generation unit 120.

  The PWM drive signal generation unit 120 outputs the PWM drive signal with the duty ratio output from the selection unit 118 to the electromagnetic solenoid 70.

  As illustrated in FIG. 14, the current detection unit 122 includes a resistor 260, an operational amplifier 262, an averaging unit 264, and an A / D converter 266. One end of the resistor 260 is connected to the exciting coil 60 and the negative terminal of the operational amplifier 262, and the other end is grounded and connected to the positive terminal of the operational amplifier 262.

  The operational amplifier 262 detects the value of the current flowing through the exciting coil 60 by calculating the voltage across the resistor 260. The averaging means 264 averages the current value (analog) output from the operational amplifier 262 using, for example, a CR filter. The A / D converter 266 converts the analog voltage value output from the averaging means 264 into a digital voltage value at a constant sampling period.

  In the normal control of the electromagnetic actuator 56, first, the target transmission torque to be distributed to the left and right rear axles 24, 26 is calculated by the target transmission torque calculation means 112 in accordance with the traveling state of the vehicle.

  Then, the target control current conversion means 252 in the target control current value calculation means 114 calculates the air gap estimated by the method of the present invention and the target transmission torque calculated by the target transmission torque calculation means 112 in step S70 of FIG. As shown, the target control current is calculated with reference to the target control current conversion map 250 in the target control current value calculation means 114.

  The PID calculation unit 116 performs PWM control so that the excitation current detected by the current detection unit 122 matches the target control current. Thereby, a target transmission torque is generated and the rear wheel axles 24 and 26 of the vehicle can be driven.

  As described above, according to the embodiment of the present invention, the inductance of the exciting coil 60 corresponding to the temperature is calculated, the air gap is estimated based on this inductance, and the target that flows through the exciting coil 60 according to the air gap is calculated. Since the control current value is controlled, the search coil can be eliminated from the electromagnetic solenoid 70, the search coil and the circuit for detecting the electromotive force of the search coil are unnecessary, and the cost of the electromagnetic actuator 56 can be reduced. it can.

It is the schematic which shows the power transmission system of a four-wheel drive vehicle. It is sectional drawing of a speed increasing apparatus (transmission apparatus) and a rear differential apparatus. It is a figure which shows RL series circuit. It is a time chart at the time of electric current rise. It is a time chart at the time of electric current fall. It is a flowchart which estimates the air gap which concerns on this invention embodiment. It is a flowchart which checks the detection conditions of an inductance. It is a flowchart which checks the other detection conditions of an inductance. It is a flowchart which shows the detection of the inductance at the time of an electric current rise. It is a flowchart of the validity judgment of an inductance. It is a graph which shows the relationship between the temperature of an exciting coil, and resistance. It is a table which shows the relationship between the temperature of an exciting coil, and an inductance. It is a table which shows the relationship between the inductance of an exciting coil, and an air gap. It is a figure which shows an electromagnetic solenoid and a peripheral circuit. It is a functional block diagram of an electromagnetic actuator control means. FIG. 16 is a functional block diagram of a target control current value calculation unit in FIG. 15. It is a flowchart which shows the normal control of an electromagnetic actuator.

Explanation of symbols

10 Speed increaser (transmission)
12 Rear differential devices 24, 26 Rear axle 30 Input shaft 32 Output shaft 50A, 50B Planetary gear set 51 Electromagnetic brake mechanism 52 Wet multi-plate brake 56 Electromagnetic actuator 58 Core (yoke)
60 Exciting coil 62 Armature 70 Electromagnetic solenoid

Claims (3)

An air gap estimation device for an electromagnetic actuator having a core having an exciting coil and an armature disposed so as to face the core via an air gap,
Vehicle stop state detecting means for detecting the stop state of the vehicle;
A constant voltage applying means for applying a predetermined DC constant voltage to the exciting coil when the vehicle stop state is detected by the vehicle stop state detecting means;
When the DC constant voltage is applied to the excitation coil by the constant voltage applying means, the excitation coil is activated based on the rise time or fall time until the rise current or fall current of the excitation coil reaches a specified value. A time constant measuring means for measuring a constant;
Inductance calculating means for calculating the inductance of the exciting coil from the time constant and the resistance of the exciting coil;
An air gap estimating means for estimating an air gap based on the inductance calculated by the inductance calculating means;
An air gap estimation device for an electromagnetic actuator, comprising: An air gap estimation device for an electromagnetic actuator having a core having an excitation coil and an armature disposed so as to face the core via an air gap and fastening an electromagnetic brake by energizing the excitation coil. And
Non-engagement detecting means for detecting non-engagement of the electromagnetic brake;
A constant voltage applying means for applying a predetermined DC constant voltage to the exciting coil when the non-engagement detecting means detects the non-engagement time of the electromagnetic brake;
When the DC constant voltage is applied to the excitation coil by the constant voltage applying means, the excitation coil is activated based on the rise time or fall time until the rise current or fall current of the excitation coil reaches a specified value. A time constant measuring means for measuring a constant;
Inductance calculating means for calculating the inductance of the exciting coil from the time constant and the resistance of the exciting coil;
An air gap estimating means for estimating an air gap based on the inductance calculated by the inductance calculating means;
An air gap estimation device for an electromagnetic actuator, comprising: Temperature detecting means for detecting the temperature of the exciting coil;
3. The air gap estimation device for an electromagnetic actuator according to claim 1, further comprising inductance correction means for correcting the inductance according to the temperature of the exciting coil.

Images