WO2023074825A1

WO2023074825A1 - Work machine

Info

Publication number: WO2023074825A1
Application number: PCT/JP2022/040264
Authority: WO
Inventors: 健太原田
Original assignee: 工機ホールディングス株式会社
Priority date: 2021-10-29
Filing date: 2022-10-27
Publication date: 2023-05-04

Abstract

Provided is a work machine capable of estimating position information of a brushless motor from a current, even when an operation unit is in an off state. A control unit 41 transitions from constant speed control to deceleration control when a switch 5 is turned off at a time t14. The deceleration control is for decreasing a duty ratio to a prescribed value (for example, 10%) and decreasing a rotor rotational speed at a smaller deceleration than inertial rotation. The control unit 41 performs the deceleration control when the rotor rotational speed exceeds a prescribed rotational speed. The control unit 41 detects (estimates) the rotor position on the basis of the motor current even when performing deceleration control, and transitions from the deceleration control to acceleration control when the switch 5 is turned on during the deceleration control.

Description

work machine

The present invention relates to a working machine having a brushless motor.

A brushless motor is used as a drive source for a working machine such as an electric tool. A sensorless control system is known as a control system for a brushless motor using an inverter circuit. Vector control is known as control for efficiently driving a brushless motor. When vector control is executed by the sensorless control method, the rotational position of the rotor is detected from the current flowing through the stator coil without providing a position sensor such as a Hall IC.

WO2016/067811

In the control of the brushless motor, if all the switching elements of the inverter circuit are turned off when the operation unit is turned off, the rotor of the brushless motor performs inertial rotation. In the sensorless control method, when estimating the rotor position from the current flowing through the brushless motor to execute vector control, the current cannot be measured when all the switching elements are off, so the rotor position cannot be estimated. Therefore, even if the operation unit is turned on again while the rotor is inertially rotating, the current position of the rotor cannot be estimated. In this case, for example, in order to prevent an abnormal operation, it is necessary to perform special control such as stopping the brushless motor once by applying a brake and then re-accelerating the motor. As a result, it takes time to reaccelerate the brushless motor when the operation unit is turned on again.

An object of the present invention is to solve at least one of the following

problems

1 and 2. [Problem 1] To provide a work machine in which a brushless motor of a sensorless control system is controlled by vector control, in which the time required for re-acceleration of the brushless motor when the operation unit is turned on again can be shortened. [Problem 2] To provide a work machine having a sensorless control type brushless motor that can reduce the number of revolutions of the brushless motor while detecting currents flowing through a plurality of stator coils when an operation unit is turned off. .

An aspect of the present invention is a brushless motor including a rotor and a stator having a plurality of stator coils, and instructing to start the brushless motor when turned on, and starting the brushless motor when turned off. a driving circuit having a plurality of switching elements and outputting a driving voltage to the plurality of stator coils; and a plurality of current detecting portions detecting the current flowing through each of the plurality of stator coils. and a control unit that controls the drive circuit by vector control based on the currents detected by the plurality of current detection units, wherein the control unit is operated after the operation unit is turned off. The drive circuit is controlled by vector control so that the rotation speed of the brushless motor increases without stopping the brushless motor when the operation unit is turned on before the brushless motor stops. , is a working machine characterized by: Another aspect of the present invention is a brushless motor comprising a rotor and a stator having a plurality of stator coils; a drive circuit having a plurality of switching elements and outputting a drive voltage to the plurality of stator coils; and a plurality of current detection units for detecting currents flowing through each of the plurality of stator coils. and a control section that controls the drive circuit based on the currents detected by the plurality of current detection sections, wherein the control section controls, when the operation section is turned off, the The drive circuit is controlled so that a drive voltage that reduces the rotation speed of the brushless motor is output to the plurality of stator coils, and the plurality of current detection units detects the current when the operation unit is turned off. The work machine is characterized in that it is configured to control the drive circuit based on the applied current.

The present invention may be expressed as "electric working machine", "electric tool", "electrical equipment", etc., and those expressed in such terms are also effective as aspects of the present invention.

According to the present invention, at least one of the

problems

1 and 2 can be solved.

1 is a plan view of a working machine 1 according to an embodiment of the present invention; FIG. FIG. 2 is a side cross-sectional view of the working machine 1; FIG. 3 is an axial view of the brushless motor 6 of FIG. 2 with a stator coil 3h omitted; FIG. 2 is a view of the stator of the brushless motor 6 viewed from the axial direction; FIG. 2 is a circuit block diagram of a control device 40 for the brushless motor 6; Schematic diagram showing the definition of a dq coordinate system in vector control. An explanatory diagram of an example of a current vector Idq in the dq coordinate system and its current phase angle β. (A) is a diagram showing an example of current vectors Iu, Iv, and Iw of each phase of U, V, and W, and a current vector Iuvw synthesized from them. (B) is a diagram showing a current vector Idq (=Iuvw) and current vectors Id and Iq which are its d component and q component. Explanatory diagrams of patterns 1 to 6 of ON/OFF combinations of switching elements Q1 to Q6 in vector control and output voltage vectors in each. FIG. 8 is an explanatory diagram of patterns 7 to 8 of ON/OFF combinations of switching elements Q1 to Q6 in vector control and output voltage vectors in each of them; (A) is an explanatory diagram showing an example of a target voltage vector in vector control and a method of synthesizing the target voltage vector. (B) is an on/off time chart of the switching elements Q1 to Q6 for generating the target voltage vector; (A) is a time chart of the rotation speed and current of the brushless motor 6 and the duty ratio of the PWM signal for controlling the inverter circuit 42 in the operation example 1 of the working machine 1; (B) is a time chart of the rotation speed and current of the brushless motor 6 and the duty ratio of the control signal of the inverter circuit 42 in the operation example 2 (comparative operation example) of the working machine 1; (A) is a time chart of the rotation speed of the brushless motor 6 in the operation example 3 of the working machine 1; (B) is a time chart of the rotation speed of the brushless motor 6 in the operation example 4 of the working machine 1; (C) is a time chart of the number of rotations of the brushless motor 6 in Example 5 of operation of the working machine 1; 10 is a time chart of the number of rotations of the brushless motor 6 in Operation Example 6 of the working machine 1; 4 is a control flowchart of the working machine 1; Explanatory drawing of the current vector at the time of deceleration control. 4 is a time chart showing rotation speed, DC link voltage, q-axis current, and d-axis current when the inertia of the tip tool is kept constant and the current vector is changed. B) is when the current vector is set to I2, and (C) is when the current vector is set to I3. 4 is a time chart showing rotation speed, DC ring voltage, q-axis current, and d-axis current when the current vector is constant regardless of the inertia of the tip tool; is small. 4 is a time chart showing rotation speed, DC link voltage, q-axis current, and d-axis current when the current vector is changed according to the inertia of the tip tool; is small.

Hereinafter, the same or equivalent constituent elements, members, etc. shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. The embodiments are illustrative rather than limiting of the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

The present embodiment relates to a working machine 1. FIG. Referring to FIG. 1, the front-rear, up-down, and left-right directions of the working machine 1 that are orthogonal to each other are defined. The work machine 1 is an AC-driven grinder (disk grinder), which is an example of an electric power tool, and operates with power supplied from an external AC power supply 60 (FIG. 5). The work machine 1 includes a grindstone 2 as a rotating tool (tip tool), and is used for grinding work, cutting work, and the like. A work machine 1 includes a housing 3 and a gear case 4 .

The housing 3 is, for example, a resin molding having a substantially cylindrical shape as a whole. A power cord 62 extends from the rear end of the housing 3 for connection to an AC power supply 60 (FIG. 5). The gear case 4 has a case body 10 made of metal such as an aluminum alloy, and a packing gland 11 that closes the opening of the case body 10 . The case body 10 is attached to the front end of the housing 3 .

The work machine 1 includes a brushless motor 6 and a fan 8 inside a housing 3 . The fan 8 is for cooling the brushless motor 6 and the like, is provided on the output shaft 6a of the brushless motor 6, and rotates integrally with the output shaft 6a. Fan 8 is positioned in front of brushless motor 6 . A first bevel gear 21 is provided at the front end of the output shaft 6a.

Two bearings (a needle bearing 12 and a ball bearing 13) are provided inside the gear case 4, and the spindle 20 is rotatably held by these bearings. The spindle 20 is perpendicular to the output shaft 6 a of the brushless motor 6 . One end of the spindle 20 penetrates the packing gland 11 and protrudes to the outside. The other end of the spindle 20 is positioned inside the gear case 4 .

A second bevel gear 22 is provided at the other end of the spindle 20 . The second bevel gear 22 meshes with the first bevel gear 21 . The rotation of the brushless motor 6 is transmitted to the spindle 20 after the rotation direction is changed by 90 degrees by the first bevel gear 21 and the second bevel gear 22 and the rotation speed is reduced. That is, the spindle 20 is rotationally driven by the brushless motor 6 .

The grindstone 2 is fixed to the spindle 20 by a wheel washer and a lock nut, and rotates integrally with the spindle 20 . The wheel guard 14 is attached to the packing gland 11 and covers approximately half of the grindstone 2 to prevent scattering of cutting powder, sparks, etc. generated during grinding. The spindle 20 and grindstone 2 are examples of the output section. Spindle 20 is an example of a tip tool attachment. The grindstone 2 is an example of a load part, a tip tool, and a rotating tool.

The work machine 1 includes a switch 5 as an operation unit for a user to instruct starting and stopping of the brushless motor 6 . The switch 5 is exposed on the left side surface of the housing 3 . When the user operates the switch 5, power is supplied from the AC power supply 60 (FIG. 3) to the brushless motor 6, and the output shaft 6a of the brushless motor 6 rotates. As the output shaft 6a rotates, the spindle 20 connected to the output shaft 6a by the first bevel gear 21 and the second bevel gear 22 rotates, and the grindstone 2 fixed to the spindle 20 rotates.

The working machine 1 includes a board 9 inside the housing 3 . The board 9 is positioned behind the brushless motor 6 . The substrate 9 mounts a plurality of switching elements 15 forming an inverter circuit 42 (FIG. 5), which will be described later. A plurality of switching elements 15 correspond to switching elements Q1 to Q6 shown in FIG. Board 9 mounts each member of control device 40 shown in FIG. 5 except for brushless motor 6 .

The brushless motor 6 includes a rotor core 6b that is provided around an output shaft 6a and rotates integrally with the output shaft 6a, a plurality of rotor magnets (permanent magnets) 6c that are inserted and held in the rotor core 6b, and magnets that surround the outer periphery of the rotor core 6b. It includes a stator core 6e provided and a plurality of stator coils 6h provided on the stator core 6e. The rotor core 6b and the rotor magnet 6c constitute a rotor of the brushless motor 6 (hereinafter referred to as "rotor"). The stator core 6e and the stator coil 6h constitute the stator of the brushless motor 6. As shown in FIG. The brushless motor 6 here has a 4-pole, 6-slot configuration, with four rotor magnets 6c and six stator coils 6h.

As shown in FIG. 3, the stator core 6e includes a cylindrical (annular) yoke portion 6f and a plurality of salient pole portions (teeth portions) 6g projecting radially inward from the yoke portion 6f. A stator coil 6h is provided for each salient pole portion 6g. As shown in FIG. 4, the stator coil 6h has U-phase coils U1 and U2, V-phase coils V1 and V2, and W-phase coils W1 and W2. The stator coils 6h are arranged in the axial direction of the brushless motor 6 in the order of V-phase coil V2, U-phase coil U1, W-phase coil W2, V-phase coil V1, U-phase coil U2, and W-phase coil W1. The stator coil 6h of each phase is Y-connected (star-connected) as shown in FIG.

FIG. 5 is a circuit block diagram of the control device 40 that controls the brushless motor 6. As shown in FIG. In FIG. 5, two stator coils 6h for each phase of the brushless motor 6 are simply shown as one. The control device 40 has a control section 41 , an inverter circuit 42 as a drive circuit, a voltage detection circuit 43 , an amplifier circuit 44 and a rectifier circuit 61 .

The rectifier circuit 61 includes, for example, a diode bridge and a smoothing capacitor, and converts alternating current supplied from the alternating current power supply 60 to direct current. The voltage detection circuit 43 detects the output voltage of the rectifier circuit 61 (voltage on the input side of the inverter circuit 42 ) and transmits it to the control section 41 . The inverter circuit 42 converts the DC power output from the rectifier circuit 61 into drive power for the brushless motor 6 and supplies the drive power to the brushless motor 6 (outputs a drive voltage to the stator coil 6h). Inverter circuit 42 includes three-phase bridge-connected switching elements Q1-Q6. Switching elements Q1-Q3 are upper switching elements, and switching elements Q4-Q6 are lower switching elements.

Switching elements Q1 and Q4 are connected to one end of the U-phase coil. Switching element Q1 is a U-phase upper switching element, and switching element Q4 is a U-phase lower switching element. Switching elements Q2 and Q5 are connected to one end of the V-phase coil. Switching element Q2 is a V-phase upper switching element, and switching element Q5 is a V-phase lower switching element. Switching elements Q3 and Q6 are connected to one end of the W-phase coil. Switching element Q3 is a W-phase upper switching element, and switching element Q6 is a W-phase lower switching element.

The shunt resistors Ru, Rv, and Rw are examples of current detection units, and are provided on the low potential side of the paths of the currents (currents of each phase) flowing through the stator coils 6h of the U, V, and W phases. Converts phase current to voltage (detects current in each phase). The amplifier circuit 44 amplifies the voltage across each of the shunt resistors Ru, Rv, and Rw, and transmits the amplified voltage to the control unit 41 as a current detection signal for each of the U, V, and W phases.

The control unit 41 includes, for example, a microcontroller and a driver IC, and controls the inverter circuit 42, that is, the switching element Q1, while monitoring the output voltage of the rectifier circuit 61 and the current of each phase according to the operation of the switch 5 by the user. The driving of the brushless motor 6 is controlled through the ON/OFF control of Q6.

The control unit 41 detects the rotational position of the rotor (hereinafter referred to as "rotor position") and the angular velocity of the rotor (hereinafter referred to as "rotor angular velocity") based on the voltage on the input side of the inverter circuit 42 and the current of each phase without a sensor. The control unit 41 can specify the number of rotations of the brushless motor 6, that is, the number of rotations of the rotor (hereinafter, "rotor number of rotations") from the rotor angular velocity.

Drive control of the brushless motor 6 by the controller 41 is, for example, vector control. Vector control is also called Space Vector Pulse Width Modulation (SVPWM).

FIG. 6 is a schematic diagram showing the definition of the dq coordinate system in vector control. FIG. 7 is an explanatory diagram of an example of the current vector Idq in the dq coordinate system and its current phase angle β. An electrical angle is used in the description of vector control. Since the brushless motor 6 has a 4-pole, 6-slot configuration, the mechanical angle of 180 degrees of the brushless motor 6 corresponds to the electrical angle of 360 degrees. FIG. 6 shows a schematic view of the configuration of the brushless motor 6 for a mechanical angle of 180 degrees, which is expanded to 360 degrees. One rotation of the brushless motor 6 (rotation of 360 electrical degrees) in FIG. 6 corresponds to a mechanical half rotation of the brushless motor 6 (180 mechanical degrees).

The brushless motor 6 has a direction of a current vector Idq (current phase The angle β) changes the torque and speed characteristics. If the current vector Idq can be controlled so that the torque and rotation speed characteristics are appropriate, the brushless motor 6 can be driven with high efficiency. Vector control is to control the current vector Idq.

The current vector Idq in the dq coordinate system is defined by the central axes (u-, v-, and w-axes) of the stator coils 6h of the U, V, and W phases of the inverter circuit 42 shown in FIG. The current vector Iuvw obtained by synthesizing the current vectors Iu, Iv, and Iw of each phase on the uvw coordinate system is converted to the dq coordinate system as shown in FIG. 8(B). Therefore, in order to perform vector control, it is necessary to control the currents of the U, V, and W phases. In order to control the current of each phase of U, V, and W, the inverter circuit 42 (switching elements Q1 to Q6 ) must be controlled.

As shown in FIGS. 9A to 9F and 10A to 10B, the energization pattern of the inverter circuit 42 includes upper (high side) and lower sides of each phase of U, V, and W. There are eight energization patterns depending on which of the (low side) switching elements is to be energized. FIGS. 9A and 9B also show the voltage components of each phase, which are the basis of the final voltage vector.

In energization pattern 1 shown in FIG. 9A, switching elements Q1, Q5, and Q6 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector oriented in the positive direction (U direction) of the U axis.

In energization pattern 2 shown in FIG. 9B, switching elements Q1, Q2, and Q6 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector oriented in the minus direction (W− direction) of the W axis.

In the energization pattern 3 shown in FIG. 9C, the switching elements Q2, Q4, and Q6 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector directed in the positive direction (V direction) of the V axis.

In energization pattern 4 shown in FIG. 9D, switching elements Q2, Q3, and Q4 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector oriented in the negative direction (U- direction) of the U axis.

In energization pattern 5 shown in FIG. 9(E), switching elements Q3, Q4, and Q5 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector oriented in the positive direction (W direction) of the W axis.

In the energization pattern 6 shown in FIG. 9(F), the switching elements Q1, Q3, and Q5 are on, and the others are off. In this case, combining the voltage vectors of the respective phases yields a voltage vector oriented in the negative direction (V- direction) of the V-axis.

Thus, in the energization patterns 1 to 6, voltage vectors with different directions are applied to the brushless motor 6 (stator coil 6h) at intervals of 60 degrees.

In the energization pattern 7 shown in FIG. 10A, the lower switching elements Q4, Q5, and Q6 are on, and the others are off. In the energization pattern 8 shown in FIG. 10B, the upper switching elements Q1, Q2, and Q3 are on, and the others are off. In the energization patterns 7 and 8, 0 vector is applied to the brushless motor 6 (stator coil 6h). One of the energization patterns 7 and 8 corresponds to the first state, and the other corresponds to the second state.

A voltage vector by each of the energization patterns 1 to 8 is hereinafter referred to as a "base vector". Since the voltage vector that can be applied in a single energization pattern is limited to the direction of the basis vector, it is necessary to synthesize and output two or more basis vectors in order to apply a voltage vector in an arbitrary direction.

FIG. 11A shows an example of a method of generating a target voltage vector by synthesizing basis vectors. In this example, the target voltage vector can be decomposed into a U direction basis vector (energization pattern 1), a W-direction basis vector (energization pattern 2), and a 0 vector basis vector (energization patterns 7 and 8). Therefore, if the

energization patterns

1, 2, 7, and 8 of the inverter circuit 42 are continued for a period of time (t1, t2, t7, t8) corresponding to the ratio of the length of each basis vector, the target voltage vector is output. can do. A basis vector of 0 vectors is required for adjustment of the absolute value (length) of the voltage vector.

FIG. 11(B) is a time chart of on/off of the switching elements Q1 to Q6 for generating the target voltage vector shown in FIG. 11(A). In vector control, at the leftmost point in FIG. 11B (that is, at the point of the first energization pattern 7), the currents of the U, V, and W phases are detected to specify the rotor position and rotor angular velocity. Then, a voltage vector to be applied to the brushless motor 6 (stator coil 6h) is set according to the specified rotor position and rotor angular velocity. The voltage vector is set by pulse width modulation (PWM) applied to each of the U, V, and W phases. Then, at the rightmost point in FIG. 11B (that is, at the point of the second energization pattern 7), the currents of the U, V, and W phases are detected again to specify the rotor position and the rotor angular velocity. The voltage vector to be applied to the brushless motor 6 (stator coil 6h) is reset according to the rotor position and rotor angular velocity. Therefore, one cycle of pulse width modulation (PWM) is from the left end of FIG. 11(B) to the right end of FIG. 11(B), which is one cycle of space vector pulse width modulation (SVPWM). When the U, V, and W phases are driven by PWM, each phase is driven so that the time ratio of each energization pattern within one cycle of PWM is t1:t2:t7:t8, as shown in FIG. 11(B). (the duty ratio of the PWM signal applied to each control terminal of the switching elements Q1 to Q6), the target voltage vector shown in FIG. 11A can be output. In SVPWM, an arbitrary target voltage vector is output in this way.

(Operation example 1) Fig. 12(A) shows the rotor rotation speed, the current flowing through the stator coil 6h (hereinafter referred to as "motor current"), and the PWM signal for controlling the inverter circuit 42 in operation example 1 of the working machine 1. 4 is a time chart of a duty ratio (hereinafter referred to as "duty ratio"); In this figure, the duty ratio is such that, among the energization patterns of the inverter circuit 42, the energization patterns (patterns 1 to 6 shown in FIGS. 9A to 9F) that give driving force to the brushless motor 6 are refers to the ratio of The same applies to FIG. 12(B), which will be described later.

When the switch 5 is turned on at time t11, the control unit 41 first performs initial position estimation control, and then performs open loop control. The initial position estimating control is control to turn on/off the switching elements Q1 to Q6 in a predetermined pattern, and to estimate the initial position of the rotor from the current of each phase at that time. Open-loop control increases the rotor speed by increasing the switching speed of the ON/OFF pattern of the switching elements Q1 to Q6 while controlling the current constant without relying on the feedback of the rotor position in the low speed range. be. The initial position estimation control corresponds to the first control, and the open loop control corresponds to the second control.

When the open loop control ends at time t12, the controller 41 performs acceleration control. Acceleration control is control for increasing the rotor speed toward a target value by increasing the duty ratio while detecting the rotor position. Motor current drops when transitioning from open-loop control to acceleration control. Acceleration control corresponds to the third control.

When the rotor speed reaches the target speed at time t13, the controller 41 shifts from acceleration control to constant speed control. Constant speed control is control that keeps the rotor speed constant while detecting the rotor position. In the illustrated example, the load applied to the brushless motor 6 is constant, and in constant speed control, the controller 41 maintains the rotor rotation speed at the target rotation speed by fixing the duty ratio. When the load fluctuates, the control unit 41 maintains the rotor rotation speed at the target rotation speed by changing the duty ratio. Motor current decreases when shifting from acceleration control to constant speed control. Constant speed control corresponds to the fourth control.

When the switch 5 is turned off at time t14, the controller 41 shifts from constant speed control to deceleration control. Deceleration control is control that reduces the duty ratio to a predetermined value and reduces the rotor rotation speed at a deceleration smaller than the inertial rotation. As the duty ratio decreases, the motor current also decreases. Deceleration control corresponds to the fifth control.

The predetermined value is a duty ratio within a range of duty ratios in which a detectable motor current flows, such as the lowest duty ratio within the range or a duty ratio in the vicinity thereof. Specifically, the predetermined value is, for example, 10% or less.

In deceleration control, the controller 41 continues to control the inverter circuit 42 with the reduced duty ratio. That is, in the deceleration control, the control unit 41 is configured to reduce and continue the output of the drive voltage from the inverter circuit 42 to the stator coil 6h to decelerate the rotor (reduce the rotor rotation speed). In other words, the control unit 41 is configured to output a drive voltage from the inverter circuit 42 to the stator coil 6h so as to decrease the rotation speed of the rotor.

The control unit 41 detects (estimates) the rotor position even during execution of deceleration control. Since the output of the drive voltage from the inverter circuit 42 to the stator coil 6h is continued, the control unit 41 can detect the rotor position based on the motor current even during execution of deceleration control.

The control unit 41 executes deceleration control when the rotor rotation speed exceeds a predetermined rotation speed. This is because the deceleration control is performed only within the rotation speed range in which the detection accuracy of the rotor position can be kept high. When the rotor position is detected without a sensor, the rotor position detection error increases in the low speed range. The predetermined number of revolutions is, for example, 600 rpm.

In this way, the control unit 41 determines that the switch 5 is turned off and that the rotor rotation speed exceeds a predetermined rotation speed as conditions necessary for starting and continuing deceleration control. In deceleration control, the control unit 41 may reduce the duty ratio to a predetermined value gradually or stepwise instead of reducing it all at once as in the illustrated example. Similarly, in the area of acceleration control, the duty ratio may not be increased at once, but may be increased gradually or step by step.

When the switch 5 is turned on at time t15 when the rotor speed exceeds the predetermined speed, the controller 41 shifts from deceleration control to acceleration control. Since the control unit 41 detects the rotor position even during execution of deceleration control, it can immediately shift to acceleration control when the switch 5 is turned on. The control unit 41 increases the duty ratio when shifting from deceleration control to acceleration control. Along with this, the output of the drive voltage from the inverter circuit 42 to the stator coil 6h increases, and the motor current rises. In reacceleration by turning on the switch 5 during execution of deceleration control, the control parameter (for example, duty ratio increase mode) may be changed so that the acceleration characteristic differs from that in the case of acceleration from a stopped state. When the rotor speed reaches the target speed at time t16, the controller 41 shifts from acceleration control to constant speed control.

(Operation example 2: Comparative operation example) Fig. 12(B) shows the rotor rotation speed, motor current, and duty ratio of the PWM signal for controlling the inverter circuit 42 in operation example 2 (comparative operation example) of the work machine 1. It is a time chart. The control for the period from time t11 to t14 in FIG. 12B is the same as the control for the period from time t11 to t14 in FIG. 12A.

When the switch 5 is turned off at time t14, the controller 41 shifts from constant speed control to inertial rotation control. Inertia rotation control is control to decelerate the rotor by inertia rotation by turning off all of the switching elements Q1 to Q6.

When the switch 5 is turned on at time t15 when the rotor rotation speed exceeds a predetermined rotation speed, the control unit 41 stops the rotor and then re-drives the rotor, as will be described later. During inertial rotation, all of the switching elements Q1 to Q6 are off, and the rotor position cannot be detected based on the motor current. Therefore, in order to prevent malfunction, the rotor must be stopped and then driven again.

At time t15, the control unit 41 shifts from the inertial rotation control to the brake control. Brake control is control for reducing the rotor speed at deceleration greater than inertial rotation. In brake control, for example, the control unit 41 turns off the switching elements Q1 to Q3, turns on at least one of the switching elements Q4 to Q6, and applies an electrical braking force (braking force) to the rotor.

When the rotor stops at time t17, the control unit 41 performs initial position estimation control and open loop control (t17 to t18), acceleration control (t18 to t19), constant speed control (t19 to ) in order. Since the rotor is stopped and then driven again, the time t19 at which the constant speed control is started in the operation example 2 is delayed from the time t16 at which the constant speed control is started in the operation example 1. FIG.

(Operation Example 3) FIG. 13(A) is a time chart of the rotor rotation speed in Operation Example 3 of the working machine 1. FIG. The control for the period from time t11 to t14 in FIG. 12A is the same as the control for the period from time t11 to t14 in FIG. 12A. When the switch 5 is turned off at time t14, the control unit 41 shifts from constant speed control to deceleration control as in the first operation example. When the rotor speed drops to a predetermined speed at time t21, the controller 41 transitions from deceleration control to brake control. The contents of the brake control are the same as those described in the operation example 2. The rotor stops at time t22. Brake control corresponds to the sixth control.

(Operation Example 4) FIG. 13(B) is a time chart of the rotor rotation speed in Operation Example 4 of the working machine 1. FIG. The control for the period before time t21 in FIG. 13B is the same as the control for the period before time t21 in FIG. 13A. When the rotor rotation speed decreases to a predetermined rotation speed at time t21, the controller 41 shifts from deceleration control to inertial rotation control. The contents of the inertial rotation control are the same as those described in the operation example 2. The rotor stops at time t25. Inertia rotation control corresponds to the sixth control.

(Operation Example 5) FIG. 13(C) is a time chart of the rotor rotation speed in Operation Example 5 of the working machine 1 . The control for the period before time t21 in FIG. 13(C) is the same as the control for the period before time t21 in FIGS. 13(A) and (B). When the rotor rotation speed drops to a predetermined rotation speed at time t21, the control unit 41 shifts from deceleration control to inertial rotation control, as in the case of Operation Example 4. FIG.

When the switch 5 is turned on at time t26, the control unit 41 performs control to stop the rotor and then re-drive it, as will be described later. Specifically, at time t26, the control unit 41 transitions from inertial rotation control to brake control. When the rotor stops at time t31, the control unit 41 performs initial position estimation control and open loop control (t31 to t32), acceleration control (t32 to t33), constant speed control (t33 to ) in order.

(Operation Example 6) FIG. 14 is a time chart of the rotor rotation speed in Operation Example 6 of the working machine 1 . The control for the period before time t14 in FIG. 14 is the same as the control for the period before time t14 in FIG. 12(A). In this operation example, the contents of the deceleration control starting at time t14 are different from those in operation examples 1 and 3-5. In the deceleration control, the control unit 41 makes the deceleration of the rotor in a predetermined rotation speed range including the resonance point 1 and the predetermined rotation speed range including the resonance point 2 larger than the deceleration of the rotor in other rotation speed ranges. . Resonance points 1 and 2 are rotor rotation speeds at which vibration and noise increase due to the mechanical configuration of work machine 1 . Deceleration can be adjusted by a duty ratio. Vibration and noise can be suppressed by increasing the deceleration of the rotor at the resonance points 1 and 2 and at the rotor rotational speeds in the vicinity thereof.

(Control Flow) FIG. 15 is a control flow chart of the working machine 1. FIG. The control unit 41 executes an initialization process when activated (S1). If the switch 5 is on (YES in S2), the controller 41 proceeds to determine whether or not the rotor speed exceeds the first threshold (S3). The first threshold is, for example, 600 rpm.

If the rotor rotation speed does not exceed the first threshold (NO in S3), the controller 41 proceeds to determine whether the rotor is in a stopped state (S4). When the rotor is in a stopped state (YES in S4), the control unit 41 performs open loop control (S6) after executing the initial position estimation control (S5). If the rotor is not stopped (NO in S4), the controller 41 performs open loop control (S6).

If the rotor speed exceeds the first threshold (YES in S3), the controller 41 performs acceleration control or constant speed control (S7). In step S7, acceleration control is performed if the rotor rotation speed has not reached the target rotation speed, and constant speed control is performed if it has reached the target rotation speed.

If the switch 5 is off (NO in S2), the controller 41 proceeds to determine whether or not the rotor speed exceeds the second threshold (S8). The second threshold value corresponds to the predetermined number of rotations described above. If the rotor speed is not equal to or less than the second threshold (NO in S8), the controller 41 performs deceleration control (S9). When the rotor rotation speed is equal to or less than the second threshold (YES in S8), the control unit 41 stops energizing the brushless motor 6 (S12), and performs inertial rotation control or brake control (S13). When the switch 5 is turned on (NO in S14) before the rotor stops (YES in S15), the controller 41 performs brake control (S16). When the rotor stops (YES in S14), the controller 41 returns to S2.

The control unit 41 detects the motor current (S10) and estimates the rotor position (S11 ) and return to S2.

According to this embodiment, the following effects can be obtained.

(1) When the switch 5 is turned on and the brushless motor 6 is rotating and the switch 5 is turned off, if the rotor rotation speed exceeds a predetermined rotation speed, the controller 41 performs deceleration control. . In deceleration control, the control unit 41 reduces and continues the output of the drive voltage from the inverter circuit 42 to the stator coil 6h to decelerate the rotor. In other words, the control unit 41 outputs a drive voltage from the inverter circuit 42 to the stator coil 6h so as to decrease the rotation speed of the rotor. Therefore, the control unit 41 can detect the rotor position (position information of the brushless motor 6) sensorlessly based on the motor current even during execution of deceleration control, and can smoothly respond to control changes during execution of deceleration control. In addition, since the power tool is a work machine that works while applying a load, the switching elements and the motor generate heat. malfunctions, etc., can be avoided.

(2) When the switch 5 is turned on during execution of deceleration control, the control unit 41 shifts from deceleration control to acceleration control, and outputs the driving voltage from the inverter circuit 42 to the stator coil 6h. is increased from the output of the drive voltage when This causes the rotor to reaccelerate without stopping. Therefore, compared to the case where the rotor is temporarily stopped and then accelerated again, the rotor rotation speed can be quickly increased to the target rotation speed. For the user, reacceleration of the grindstone 2 becomes smooth (the time required for reacceleration is shortened), so workability is good.

(3) The control unit 41 shifts from deceleration control to inertial rotation control or brake control when the rotor rotation speed becomes equal to or less than a predetermined rotation speed. As a result, the deceleration can be increased and the power consumption can be suppressed at a rotational speed equal to or lower than a predetermined rotational speed at which highly accurate detection of the rotor position is difficult.

(4) The control unit 41 is configured to stop the rotor and then accelerate it when the switch 5 is turned off while the rotor speed is equal to or less than a predetermined speed. As a result, it is possible to suppress abnormal operation associated with re-acceleration from a state in which the rotor position cannot be detected.

(5) The control unit 41 is configured to increase or decrease the drive voltage output from the inverter circuit 42 to the stator coil 6h by controlling the duty ratio of the PWM signal input to the control terminals of the switching elements Q1 to Q6. . Therefore, highly accurate control is possible with a simple configuration.

Furthermore, by controlling the current vector Idq in the deceleration control after the switch 5 is turned off, it is possible to control the characteristics during deceleration as follows. (1) Limit the current vector to the first or second quadrant on the dq coordinate system. As a result, the deceleration force (braking force) can be adjusted by using the original current vector during acceleration (current vector for powering) during deceleration. As a premise of this control, torque in the direction of deceleration always acts on the rotating portion due to factors such as mechanical loss, albeit slightly. Also, the current to be applied during deceleration is selected within a range in which the deceleration torque is greater than the generated torque (generated torque<above deceleration torque). Furthermore, it is possible to suppress the voltage rise of the smoothing capacitor (included in the rectifier circuit 61) due to the regenerative operation (regenerative energy). Note that the first quadrant is the region shown in FIG. 7 (the positive region of the d-axis and the positive region of the q-axis). The second quadrant is a negative d-axis region and a positive q-axis region (the region above the d-axis and on the left side of the q-axis in FIG. 7). The third quadrant is a negative d-axis region and a negative q-axis region (the region below the d-axis and on the left side of the q-axis in FIG. 7). The fourth quadrant is a region of positive d-axis and negative q-axis (lower side of d-axis and right side of q-axis in FIG. 7).

(2) Make the current vector (deceleration force) constant regardless of the inertia of the tip tool (rotating tool), that is, regardless of the tip tool attached to the spindle. As a result, it is possible to decelerate with a substantially constant torque. Note that this assumes that the deceleration torque due to mechanical loss or the like is constant. By applying this control and decelerating with a torque equal to or less than a predetermined value, it is possible to suppress loosening of the tip tool and reaction to the operator's hand.

(3) Change the angle of the current vector according to the inertia of the tip tool (attached tip tool). As a result, it is possible to decelerate for a certain period of time regardless of inertia.

First, the feature (1) will be described. FIG. 16 is a diagram showing the range of current vectors in the dq coordinate system during deceleration control. As the q-axis component increases in the plus (positive) direction (above the d-axis line in the drawing), the generated torque increases. That is, the deceleration becomes moderate. Conversely, as the q-axis component increases in the negative (negative) direction (below the d-axis line in the drawing), the generated torque in the opposite direction increases, making it easier to generate regenerative energy. Therefore, in deceleration control, it is preferable to set the current vector within the first quadrant or the second quadrant (hatched area in the figure). That is, the current vectors I1 and I2 in FIG. 16 can be set as the current vector Idq for deceleration control, but the current vector I3 is in the third quadrant, so it is not preferable to set it. It should be noted that the apparent induced voltage decreases as the d-axis component increases in the negative direction (to the left in the drawing). Also, β indicates the angle of the current vector I with respect to the d-axis.

FIG. 17 is a time chart showing rotation speed, DC link voltage, q-axis current, and d-axis current when the inertia of the tip tool is constant and the current vector is changed. If the reference (zero) for the q-axis current and the d-axis current in FIG. The distance corresponds to the magnitude of the current vector. That is, the value increases as the distance from the time axis increases in the plus direction (upward direction) or in the negative direction (downward direction). The difference between the current vectors I1 and I2 due to deceleration control is the magnitude of generated torque. As can be seen from FIG. 17, since the q-axis component of the current vector I1 is larger than that of the current vector I2, the generated torque (torque for forward rotation) is larger. When the generated torque is large, the brake is less effective than when the generated torque is small, and the deceleration becomes gentler. Therefore, when the switch 5 is turned off at time t14, the deceleration control shifts to deceleration control, but setting the current vector I1 in FIG. It becomes the characteristic to do. Note that when a current vector in the third quadrant such as the current vector I3 or a current vector in the fourth quadrant is used for deceleration control, as shown in FIG. It may cause an increase in a certain DC link voltage (capacitor voltage), which may lead to destruction of elements such as a smoothing capacitor.

Next, the feature (2) above will be described. FIG. 18 is a time chart showing rotation speed, DC ring voltage, q-axis current, d and d-axis current when the current vector is constant regardless of the inertia of the tip tool. Note that in FIG. 18, as in FIG. 17, the magnitude of the current vector is based on the time axis. When the current vector is controlled to be constant, the torque generated from the brushless motor 6 is constant, so the deceleration torque (deceleration force) of the tip tool is also substantially constant. As a result, the torque applied to the tip shaft (spindle 20) can be kept constant below a predetermined value. Therefore, it is possible to suppress the loosening of the tip tool (grindstone 2) on the spindle 20, and to suppress the recoil toward the hand of the operator to a certain level or less. However, since the deceleration force is constant, the time required for deceleration increases as the inertia increases.

Next, the feature (3) above will be described. FIG. 19 is a time chart showing rotation speed, DC link voltage, q-axis current and d-axis current when the current vector is changed according to the inertia of the tip tool. Note that in FIG. 19 as well as in FIGS. 17 and 18, the magnitude of the current vector is based on the time axis. If the inertia is large, a current vector that makes the q-axis current small is selected (set) ((A) in the figure), and if the inertia is small, a current vector that makes the q-axis current large is selected (set) ( (B)). As a result, the time required for deceleration can be made constant. However, when the inertia is large, the torque for deceleration becomes large, so the reaction to the operator becomes larger than when the inertia is small.

Although the present invention has been described above with reference to the embodiments, it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiments within the scope of the claims. By the way. Modifications will be discussed below.

The connection method of the stator coil 6h may be delta connection instead of Y connection. The number of poles of the rotor and the number of slots of the stator of the brushless motor 6, that is, the number of rotor magnets 6c and the number of stator coils 6h are arbitrary. For example, the brushless motor 6 may have a two-pole, three-slot configuration.

The shunt resistors Ru, Rv, and Rw may be provided on the high potential side of the current path of each phase. In this case, the current of each phase should be detected when the switching elements Q1 to Q6 are controlled by the energization pattern 8 shown in FIG. 10(B).

If there is no risk of damage to elements such as smoothing capacitors due to regenerative energy, the current vector may be set to the third quadrant (current vector I3 in FIG. 16) or fourth quadrant. In this case, for example, the current vector I3 is set in the third quadrant to start deceleration control. The voltage of the smoothing capacitor is detected, and when the voltage of the smoothing capacitor becomes equal to or higher than a first predetermined value (for example, the rated voltage of the smoothing capacitor) due to regenerative energy, the current vector is set to the first quadrant or the second quadrant (current vectors I1, I2). to suppress the generation of regenerative energy, and then repeat the control to restore the current vector when the voltage of the smoothing capacitor becomes less than the first predetermined value or a second predetermined value smaller than the first predetermined value. good.

The duty ratio, the threshold value of the rotor speed, and the like given as specific numerical values in the embodiments do not limit the scope of the invention, and can be arbitrarily changed according to the required specifications.

The work machine of the present invention may be of a cordless type that operates with power from a battery pack. The working machine of the present invention may be one other than the grinder exemplified in the embodiment.

DESCRIPTION OF SYMBOLS 1... Working machine, 2... Grindstone (rotary tool), 3... Housing, 4... Gear case, 5... Switch (operation part), 6... Brushless motor, 6a... Output shaft, 6b... Rotor core, 6c... Rotor magnet, 6e... Stator core, 6h... Stator coil, 6f... Yoke part, 6g... Salient pole part (teeth part), 8... Fan, 9... Substrate, 10... Case body, 11... Packing gland, 12... Needle bearing, 13... Ball bearing, DESCRIPTION OF SYMBOLS 14... Wheel guard 15... Switching element 20... Spindle 21... First bevel gear 22... Second bevel gear 40... Control device (brushless motor control device) 41... Control unit (microcomputer) 42... Inverter circuit (drive circuit) 43 Voltage detection circuit 44 Amplifier circuit 60 AC power supply 61 Diode bridge (full-wave rectifier circuit) 62 Power cord Q1 to Q6 Switching elements Ru, Rv, Rw: shunt resistor (current detector).

Claims

a brushless motor comprising a rotor and a stator having a plurality of stator coils;
an operation unit that instructs to start the brushless motor when turned on and instructs to stop the brushless motor when turned off;
a driving circuit having a plurality of switching elements and outputting a driving voltage to the plurality of stator coils;
a plurality of current detection units that detect a current flowing through each of the plurality of stator coils;
a control unit that controls the drive circuit by vector control based on the currents detected by the plurality of current detection units;
A working machine comprising
The control unit is configured to increase the rotation speed of the brushless motor without stopping the brushless motor when the operation unit is turned on after the operation unit is turned off until the brushless motor stops. configured to control the drive circuit by vector control;
A work machine characterized by:
a brushless motor comprising a rotor and a stator having a plurality of stator coils;
an operation unit that instructs to start the brushless motor when turned on and instructs to stop the brushless motor when turned off;
a driving circuit having a plurality of switching elements and outputting a driving voltage to the plurality of stator coils;
a plurality of current detection units that detect a current flowing through each of the plurality of stator coils;
a control unit that controls the drive circuit based on the currents detected by the plurality of current detection units;
A working machine comprising
The control unit controls the drive circuit so that, when the operation unit is turned off, a voltage that reduces the rotation speed of the brushless motor is output to the plurality of stator coils as the drive voltage, and the operation unit is turned off. configured to control the drive circuit based on the currents detected by the plurality of current detection units when the unit is turned off;
A work machine characterized by:
The working machine according to claim 1 or 2,
The control unit controls the drive circuit so that the rotational speed of the brushless motor decreases when the operation unit is turned off, and further controls the brushless motor so that the brushless motor stops when the operation unit is kept off. configured to control a drive circuit;
A work machine characterized by:
The working machine according to claim 1 or 2,
The control unit increases the rotation speed of the brushless motor when the operation unit is turned on after the operation unit is turned off until the rotation speed of the brushless motor drops below the predetermined rotation speed. controlling the drive circuit such that
The control unit stops and then restarts the brushless motor when the operation unit is turned on after the operation unit is turned off and the rotation speed of the brushless motor drops below the predetermined rotation speed. , configured to control the drive circuit to increase the rotation speed of the brushless motor;
A work machine characterized by:
The working machine according to claim 1 or 2,
The control unit is configured to input a PWM signal to a control terminal of the switching element and control the duty ratio of the PWM signal to increase or decrease the output of the drive voltage from the drive circuit,
When the operation unit is turned off while the operation unit is turned on and the brushless motor is rotating, the control unit gradually and stepwise increases the duty ratio toward a predetermined value other than 0. or configured to drop in bursts,
A work machine characterized by:
The working machine according to claim 5,
When the operation unit is turned off and the number of revolutions of the brushless motor drops below the predetermined number of revolutions, the control unit applies a brake to the brushless motor to stop the brushless motor, or stops the brushless motor. configured to control the drive circuit to turn off a switching element to stop the brushless motor;
A work machine characterized by:
The working machine according to claim 1 or 2,
Having an output unit driven by the brushless motor,
When the operation portion is turned off while the operation portion is turned on and the brushless motor is rotating, the control portion causes the rotor to rotate at a predetermined rotation speed during the process of decelerating the rotor to the predetermined rotation speed or less. configured to cause the deceleration of the rotor in a number range to be greater than the deceleration of the rotor in other speed ranges;
A work machine characterized by:
The working machine according to claim 1 or 2,
When the operation unit is turned on while the brushless motor is stopped, the control unit performs first control to turn on and off the plurality of switching elements in a predetermined pattern,
After executing the first control, the control unit executes a second control that increases the switching speed of the on-off pattern of the plurality of switching elements while controlling the current to be constant.
A work machine characterized by:
The working machine according to claim 8,
After executing the second control, the control unit executes a third control that increases the duty ratio of the PWM signal of the plurality of switching elements while detecting the position of the rotor based on the current.
A work machine characterized by:
The working machine according to claim 1 or 2,
The control unit is configured to control the deceleration force of the brushless motor by controlling a current vector in a vector control coordinate system based on the currents detected by the plurality of current detection units.
A work machine characterized by:
The working machine according to claim 10,
The coordinate system is a dq coordinate system in which the d-axis is the direction of the magnetic flux generated by the brushless motor and the q-axis is the direction magnetically perpendicular to the d-axis,
In the dq coordinate system, increasing the current vector in the positive direction of the q axis increases the driving force of the brushless motor,
When the load applied to the brushless motor is constant, the greater the driving force of the brushless motor, the smaller the deceleration force.
A work machine characterized by:
The working machine according to claim 10,
The deceleration time of the brushless motor when the current vector is fixed is configured to vary according to the load applied to the brushless motor.
A work machine characterized by:
The working machine according to claim 10,
The deceleration time of the brushless motor is configured to be constant by controlling the current vector according to the load applied to the brushless motor.
A work machine characterized by:
The working machine according to claim 13,
The coordinate system is a dq coordinate system in which the d-axis is the direction of the magnetic flux generated by the brushless motor and the q-axis is the direction magnetically perpendicular to the d-axis,
In the dq coordinate system, increasing the current vector in the positive direction of the q axis increases the driving force of the brushless motor,
When the load applied to the brushless motor is large, the current vector has a smaller magnitude in the positive direction of the q-axis than when the load is small.
A work machine characterized by:
The working machine according to claim 1 or 2,
Having a tip tool mounting part to which a tip tool that works by rotating the brushless motor is attached,
A work machine characterized by: