JP4678719B2 - Control device and control program for motor of construction machine - Google Patents

Description

 The present invention relates to a device for controlling a motor that drives an upper turning body or the like of a construction machine and a program for controlling the motor.

  In recent years, a hybrid system using an engine and an electric motor as a drive source has been put into practical use in general automobiles, and attempts have been made to incorporate the hybrid system in the field of construction machines such as hydraulic excavators.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2001-99103) discloses a hybrid hydraulic system in which an engine and an electric motor are used together as a drive source of a hydraulic pump.

  In a hybrid system for construction machines, for example, a PM (permanent magnet motor) type is used as an electric motor (hereinafter referred to as PM motor). The frequency and current (voltage) of the PM motor are controlled by an inverter, and the rotation speed (speed) and torque of the PM motor are controlled.

  FIGS. 1A and 1B show the configurations of the inverter 10 and the PM motor 30, respectively.

  As shown in FIG. 1A, the inverter 10 is configured by a three-phase (U phase, V phase, W phase) bridge circuit. That is, the inverter 10 is provided with six switching elements 11, 12, 13, 14, 15, and 16. For example, an IGBT is used as the switching element. Each switching element 11, 12, 13, 14, 15, 16 is connected in parallel with a circulating diode 17, 18, 19, 20, 21, 22.

  Switching signals (on / off voltages) Vu, Vv, and Vw are applied to the switching elements 11, 12, and 13 for the U-phase, V-phase, and W-phase on the upper side in the drawing, respectively. Switching signals (on / off voltages) corresponding to the switching signals (voltages) Vu, Vv, and Vw are applied to the U-phase, V-phase, and W-phase switching elements 14, 15, and 16 on the lower side in the figure.

  An electrical signal line 23 from which a U-phase phase current Iu is output is connected to a connection portion of the U-phase switching elements 11 and 14. An electrical signal line 24 that outputs a V-phase current Iv is connected to a connection portion of the V-phase switching elements 12 and 15. An electrical signal line 25 that outputs a W-phase current Iw is connected to a connection portion of the W-phase switching elements 13 and 16.

  A DC voltage is applied to the input terminal of the inverter 10 from a predetermined DC power source. A smoothing capacitor 40 for smoothing the DC voltage is connected to the input terminal of the inverter 10.

  Switching signals (voltages) Vu, Vv, and Vw are applied as gate signals to each switching element 11, 12, 13 (14, 15, 16) from a predetermined controller. The switching element is controlled by, for example, PWM control. By controlling the ON / OFF time and switching frequency of the switching signal applied to each switching element 11, 12, 13 (14, 15, 16), the phase of each electrical signal line 23, 24, 25 is shifted by 120 °. Further, sinusoidal phase currents Iu, Iv, Iw having a predetermined frequency and a predetermined amplitude flow.

  A PM motor 30 is connected to the output terminal of the inverter 10, and the phase currents Iu, Iv, Iw are converted into three-phase AC power via the electric signal lines 23, 24, 25 and the output terminal, respectively. To be supplied.

  FIG. 1B is a conceptual diagram of the PM motor 30, and the stator of the PM motor 30 is composed of coils 31, 32, 33, and permanent magnets are embedded in the rotor 34. That is, the PM motor 30 in FIG. 1B is an IPM type (embedded magnet type motor). Phase currents Iu, Iv, and Iw are energized to the coils 31, 32, and 33 through electrical signal lines 23, 24, and 25, respectively. When the phase currents Iu, Iv, and Iw are respectively supplied to the coils 31, 32, and 33, rotating magnetic fields 35 and 36 are formed in the stator, and the rotor 34 rotates according to the rotating magnetic fields 35 and 36.

  The PM motor 30 is provided with a rotation speed detector configured using a resolver, an encoder, and the like. The controller controls the PM motor 30 by outputting a switching signal to each of the switching elements 11 to 16 of the inverter 10 using the detected number of rotations as a feedback amount. The controller calculates a torque value for making the deviation between the target rotational speed of the PM motor 30 and the current rotational speed zero, and further, switching signals (voltages) Vu, Vv, Vw necessary for obtaining this torque value. Is output to the inverter 10.

  The inverter 10 is configured as a modularized casing, and is joined to a cooler such as a heat sink via a base that supports the casing. Switching elements 11 to 16 (IGBTs) that are heat generation sources in inverter 10 are cooled by the cooler.

  In the case of a construction machine, the PM motor 30 is often attached as a motor for driving the upper swing body.

  This is because it is possible to effectively regenerate the energy of DC power via the inverter 10 using the PM motor 30 as a generator.

  That is, in a construction machine such as a hydraulic excavator, excavation of a natural ground and the like is loaded into the bucket, the upper swing body is swung to move the bucket to the dump truck bed, and the load in the bucket is transferred to the dump truck. The loading operation of loading on the loading platform is repeated. During the loading operation, when the bucket is positioned on the loading platform of the dump truck, the upper swing body is suddenly braked, and a large torque is generated in the swing machinery that rotates the upper swing body. Torque generated by the swing machinery is transmitted to and absorbed by the drive shaft of the PM motor 30 to generate power. At the time of braking, a switching signal for extracting reverse torque is applied to the switching elements 11-16. As a result, AC power generated by the PM motor 30 is converted into DC power by the inverter 10. The DC power is supplied from the input terminal of the inverter 10 in the reverse direction to the DC power source such as a capacitor or a storage battery via a DC power line, and is stored (charged) as power.

  In this way, the loading operation is repeatedly performed and the energy regeneration is performed each time the upper-part turning body is repeatedly stopped, so that the fuel consumption of the construction machine can be greatly reduced.

(Prior art 1)
An invention in which an elevator is driven using the above-described inverter 10 and PM motor 30 is described in Patent Document 2 described later.

In Patent Document 2, an abnormal situation may occur in which the PM motor 30 is locked (rotation stopped) due to a disconnection in a signal line that feeds back the rotation speed of the PM motor 30 or due to mechanical factors. Are listed. In patent document 2, when the locked state of the PM motor 30 continues, the temperature of the joint portion of the switching elements 11 to 16 constituting the inverter 10 rapidly increases, and there is a possibility of causing thermal destruction. Based on the data relating to the control signal of the inverter 10 and the PM motor 30 and the control constant (phase current value, etc.) in the locked state, and the data relating to the cooling capacity of the cooler, the temperature of the switching element is calculated An invention is described in which an allowable time until thermal breakdown is obtained and control is performed to protect the switching elements 11 to 16 from thermal breakdown when the allowable time has elapsed.
JP 2001-99103 A JP 2004-64864 A

  In construction machines, such as hydraulic excavators, grooving and backfilling operations are performed. In the ditching work and backfilling work, the operation of turning the work machine and pressing the work machine against a natural ground or the like is repeatedly performed. At this time, in the PM motor 30 that drives the upper-part turning body, the rotation state and the lock state are repeated such as “rotation → lock → rotation → lock...”.

  When the PM motor 30 is locked, the rotation speed of the PM motor 30 becomes almost zero, and the controller that gives a command to the inverter 10 using this as a feedback amount gives a switching signal for generating a large torque to the inverter 10. Since the output continues and a large current continues to flow through the specific switching element, the heat generation amount of the specific switching element increases.

  For this reason, it is necessary to perform control for protecting the thermal destruction of the switching element as in the case of the prior art 1 described above.

  However, in the case of a construction machine, the prior art 1 applied to the elevator mentioned above cannot be applied as it is. The reason is as follows.

a) In the PM motor 30 of the prior art 1, the fact that it is locked is an abnormal situation by itself, and it is not assumed that it was locked last time. On the other hand, in the case of the PM motor 30 of a construction machine, it is natural that the locked state is repeated at the time of work, and it must be taken into account that it was locked last time. When the prior art 1 is applied to the PM motor 30 of the construction machine, every time the locked state is entered, the temperature of the switching element is calculated without considering the thermal history of the previous locked state. However, in reality, the temperature of the switching element has already risen in the previous locked state (or the last locked state), and the calculated temperature without considering the thermal history is the actual temperature. Therefore, it is impossible to perform control to thermally protect the switching element at an appropriate time.

b) There are many types of construction machines, and the rated output of the PM motor 30 necessary for turning the upper turning body varies. For this reason, according to the kind of PM motor 30, the magnitude | size of the electric current which flows into the switching element of the inverter 10 is also various, and the thing of the cooling performance from which a cooler differs also needs to be prepared in many kinds. In the prior art 1, since the temperature of the switching element is calculated based on the data on the cooling capacity of the cooler, if there are many types of coolers, a calculation program for calculation processing is prepared for each type of cooler. And must be installed on the controller. Therefore, it is possible to calculate the temperature of the switching element with a common calculation program regardless of the cooling capacity of the cooler, in order to increase the versatility of the controller, common parts, and cost reduction Has been requested.

  The present invention has been made in view of such a situation, so that the temperature of the switching element can be accurately calculated even when the motor repeatedly operates in a locked state and a rotating state like a motor of a construction machine. Thus, the first solution is to enable the switching element to be protected from thermal destruction at an accurate time. Further, in addition to the achievement of the first problem, the present invention provides a cooler even when there are many types of coolers (cooling capacity) such as a cooler for inverters of construction machinery. The second solution is to increase the versatility of the controller, to make parts common, and to reduce costs by enabling the temperature of switching elements to be calculated with a common calculation program regardless of the cooling capacity of the controller. It is.

The first invention is
A motor for driving the construction machine;
A switching element that is operated according to the input switching signal and outputs a drive signal to the motor;
A rotational speed detection means for detecting the rotational speed of the motor;
First control means for outputting a switching signal to the switching element using the rotational speed measured by the rotational speed detection means as a feedback amount;
Determining means for determining whether the motor is in a locked state or in a rotating state;
When it is determined that the motor is in the locked state, the temperature of the current switching element is sequentially calculated using the calculation formula for the locked state based on the temperature of the switching element calculated up to the previous time. With
When it is determined that the motor is in the rotating state, the temperature of the current switching element is sequentially calculated using the calculation formula for the rotating state based on the temperature of the switching element calculated up to the previous time. Temperature calculation means;
A construction machine motor control device comprising: a second control unit that performs control to thermally protect the switching element according to the temperature of the switching element calculated by the temperature calculation unit. .

The second invention is the first invention,
The switching element is a switching element constituting an inverter,
The inverter is configured by mounting a switching element on a base plate,
A cooler for cooling the switching element is joined to the base plate,
Temperature detecting means for detecting the temperature of the base plate is provided;
The temperature calculating means includes
If it is determined that the motor is in a locked state, the temperature of the current switching element and the temperature of the base plate are based on the temperature difference between the temperature of the switching element and the temperature of the base plate calculated up to the previous time. Sequentially calculate the temperature difference between
If it is determined that the motor is in the rotating state, the current switching element temperature and the base plate temperature are determined based on the temperature difference between the switching element temperature and the base plate temperature calculated up to the previous time. Calculate the temperature difference from the temperature sequentially,
Further, the temperature of the switching element is calculated by adding the temperature of the base plate detected by the temperature detecting means to the temperature difference.

The third invention is the first invention,
The motor is a motor that drives a swing body of a construction machine.

A fourth invention is the first invention,
The second control means includes
When the temperature of the switching element calculated by the temperature calculating means exceeds a predetermined threshold value, a switching signal for thermally protecting the switching element is sent from the first control means to the switching element. A command is given to the first control means so that it is output.

The fifth invention
In a program for controlling a motor that drives a construction machine and that is driven by a drive signal given from a switching element,
Determining whether the motor is in a locked state or in a rotating state;
When it is determined that the motor is in the locked state, the temperature of the current switching element is sequentially calculated using the calculation formula for the locked state based on the temperature of the switching element calculated up to the previous time. With
When it is determined that the motor is in a rotating state, the temperature of the current switching element is sequentially calculated using a calculation formula for the rotating state based on the temperature of the switching element calculated up to the previous time. ,
The switching element is controlled to be thermally protected in accordance with the calculated temperature of the switching element.

  The first to fifth inventions will be described with reference to FIG.

  It is determined whether the PM motor 30 is in a locked state or a rotating state (step 102).

  When it is determined that the PM motor 30 is in the locked state (determination Yes in step 102), the calculation formula for the locked state based on the junction-to-base temperature difference Tbjn-1 calculated so far, That is, the function value is calculated using the function fn (W), and the current junction-base temperature difference Tbjn (= fn (W)) is sequentially calculated (step 103).

  On the other hand, when it is determined that the PM motor 30 is in the rotating state (determination No in step 102), the calculation for the rotating state is performed based on the junction-to-base temperature difference Tbjn-1 calculated so far. The function value is calculated using the equation, that is, the function gn (W), and the current junction-base temperature difference Tbjn (= gn (W)) is sequentially calculated (step 104).

  When the junction-to-base temperature difference Tbjn is calculated, a process of adding the current base temperature Tbn to the junction-to-base temperature difference Tbjn is executed to obtain the current junction temperature Tjn (Tjn = Tbn + Tbjn). Step 105).

  Next, it is determined whether or not the junction temperature Tjn exceeds the upper limit value Terr (step 106).

  If it is determined that the junction temperature Tjn has exceeded the upper limit value Terr (Yes in step 106), it is determined that there is a possibility that the switching element may be thermally destroyed when the junction temperature further increases. A protection sequence for thermally protecting 16 is executed (step 107).

  The common effects of the first to fifth inventions will be described with reference to FIG.

  In “Lock (2)” shown in FIG. 4, based on the past “Lock (1)” and “Rotation (1)” thermal history, that is, the junction-to-base temperature difference Tbjn−1 calculated so far, A junction-to-base temperature difference Tbjn is calculated.

  For this reason, when the lock state and the rotation state are repeated, the junction-to-base temperature difference Tbjn can be obtained very accurately. Then, the junction temperature Tjn is obtained based on the accurately obtained junction-to-base temperature difference Tbjn (Tjn = Tbn + Tbjn). For this reason, the junction temperature Tjn is extremely accurate. As a result, it is possible to perform control to thermally protect the switching elements 11 to 16 at an appropriate time.

  The second invention is based on the configuration shown in FIG.

  That is, the inverter 10 is configured by mounting silicon chips 11C to 16C (switching elements 11 to 16) on a base plate 91 via an insulating substrate (not shown) (in practice). A cooler 92 for cooling the silicon chips 11C to 16C (switching elements 11 to 16) is joined to the base plate 91.

  In the second invention, the junction temperature Tjn is obtained by adding the base temperature Tbn to the junction-base temperature difference Tbjn (Tjn = Tbn + Tbjn), and the junction-base temperature difference Tbjn It is calculated by an arithmetic expression that does not depend on the cooling capacity.

 Therefore, according to the second invention, the following effects are obtained in addition to the common effects of the first to fifth inventions described above.

  That is, even when the heat sink 92 is changed to one having a different cooling performance, the temperature of the switching element (junction temperature Tjn) can be calculated with a common calculation program. For this reason, the IGBT protection controller 70 can be made common, the versatility of the controller is improved, and the parts are made common and the cost is reduced.

  Embodiments of a motor control device for a construction machine and a motor control program according to the present invention will be described below with reference to the drawings.

  FIG. 6 shows an extracted portion of the configuration of the hybrid system of the construction machine that drives and controls the upper swing body 1. In the embodiment, a hydraulic excavator is assumed as the construction machine.

  A PM motor 30 is attached to the hydraulic excavator as a motor for driving the upper swing body 1. In other words, a swing machinery 2 including a swing circle, a swing pinion, and the like is connected to the upper swing body 1. When the swing machinery 2 is driven, the upper swing body 1 rotates.

  The drive shaft of the PM motor 30 is connected to the drive shaft of the swing machinery 2.

  The output terminal of the inverter 10 is electrically connected to the input terminal of the PM motor 30. A DC power source 3 composed of a capacitor, a storage battery, or the like is electrically connected to the input terminal of the inverter 10. A generator motor is connected to the output shaft of the engine, and the electric power generated by the generator motor is stored in the DC power source 3.

  The controller 60 outputs a switching signal to the inverter 10 and controls the rotation speed and torque of the PM motor 30 via the inverter 10 to rotate the upper swing body 1 at a desired rotation speed.

  FIG. 2 shows the configuration of the inverter 10, the PM motor 30, and the controller 60. The controller 60 includes an IGBT protection controller 70 and an inverter control controller 80.

  The inverter 10 includes a three-phase (U phase, V phase, W phase) bridge circuit. That is, the inverter 10 is provided with six switching elements 11, 12, 13, 14, 15, and 16. For example, an IGBT is used as the switching element. Each switching element 11, 12, 13, 14, 15, 16 is connected in parallel with a circulating diode 17, 18, 19, 20, 21, 22.

  Switching signals (on / off voltages) Vu, Vv, and Vw are applied to the switching elements 11, 12, and 13 for the U-phase, V-phase, and W-phase on the upper side in the drawing, respectively. Switching signals (on / off voltages) corresponding to the switching signals (voltages) Vu, Vv, and Vw are applied to the U-phase, V-phase, and W-phase switching elements 14, 15, and 16 on the lower side in the figure.

  An electrical signal line 23 from which a U-phase phase current Iu is output is connected to a connection portion of the U-phase switching elements 11 and 14. An electrical signal line 24 that outputs a V-phase current Iv is connected to a connection portion of the V-phase switching elements 12 and 15. An electrical signal line 25 that outputs a W-phase current Iw is connected to a connection portion of the W-phase switching elements 13 and 16.

  A DC voltage is applied from the DC power supply 3 to the input terminal of the inverter 10. A smoothing capacitor 40 for smoothing the DC voltage is connected to the input terminal of the inverter 10.

  Switching signals (voltages) Vu, Vv, Vw are applied as gate signals from the inverter control controller 80 to the switching elements 11, 12, 13 (14, 15, 16). The switching element is controlled by, for example, PWM control. By controlling the ON / OFF time and switching frequency of the switching signal applied to each switching element 11, 12, 13 (14, 15, 16), the phase of each electrical signal line 23, 24, 25 is shifted by 120 °. Further, sinusoidal phase currents Iu, Iv, Iw having a predetermined frequency and a predetermined amplitude flow.

  A PM motor 30 is connected to the output terminal of the inverter 10, and the phase currents Iu, Iv, Iw are converted into three-phase AC power via the electric signal lines 23, 24, 25 and the output terminal, respectively. To be supplied.

  The PM motor 30 is provided with a rotational position (angle) detector 50 such as a resolver that detects the rotational position (rotational angle) θ of the PM motor 30. The inverter control controller 80 receives the detection signal θ of the rotational position detector 50. Based on the detection signal θ of the rotational position detector 50, the rotational speed (rotational speed) ω is calculated.

  Further, the phase currents Iu and Iw flowing through the electric signal lines 23 and 25 are detected and input to the inverter control controller 80.

  The inverter control controller 80 generates the switching signals Vu, Vv, Vw so that the rotational speed of the PM motor 30 becomes the target rotational speed ωp using the actual rotational speed ω of the PM motor 30 as a feedback amount, and the inverter 10 Are output to each of the switching elements 11 to 16 to control the PM motor 30.

  The inverter control controller 80 can be configured by a control system that performs vector control of the PM motor 30. That is, the inverter control controller 80 calculates a torque value τ for making the deviation between the target rotational speed ωp of the PM motor 30 and the current rotational speed ω zero, and further calculates this torque value τ in the rotational coordinate system d. The shaft current value Id and the q-axis current value Iq are converted. Based on the rotational position θ, the rotational speed ω, and the phase currents Iu and Iw, the d-axis current value Id and the q-axis current value Iq are converted into the d-axis voltage value Vd and the q-axis voltage value Vq, respectively. Then, based on the rotation position θ, the d-axis voltage value Vd and the q-axis voltage value Vq are converted into voltage values (switching signals) Vu, Vv, and Vw in the stationary coordinate system. The switching signals (voltages) Vu, Vv, Vw calculated in this way are output to the inverter 10.

  It operates as follows during energy regeneration.

  That is, the excavator excavates the ground and loads it into the bucket, turns the upper swing body 1 to move the bucket to the dump truck bed, and loads the load in the bucket onto the dump truck bed. Assume that this is repeated. During the loading operation, when the bucket is positioned on the loading platform of the dump truck, the upper swing body 1 is suddenly braked, and a large torque is generated in the swing machinery 2 that rotates the upper swing body 1. Torque generated by the swing machinery 2 is transmitted to and absorbed by the drive shaft of the PM motor 30 to generate power. At the time of braking, a switching signal for extracting reverse torque is applied to the switching elements 11-16. As a result, AC power generated by the PM motor 30 is converted into DC power by the inverter 10. The direct current power is supplied from the input terminal of the inverter 10 in the reverse direction to the direct current power source 3 via the direct current power line, and is stored (charged) as electric power.

  Since the loading operation is repeated in this way and the energy regeneration is performed each time the upper-part turning body 1 is repeatedly stopped, the fuel consumption of the construction machine can be greatly reduced.

  FIG. 5 is a perspective view showing a configuration of a device for cooling the inverter 10.

  In the inverter 10, silicon chips 11C, 12C, 13C, 14C, 15C, and 16C corresponding to the switching elements 11, 12, 13, 14, 15, and 16 are mounted on a base plate 91 via an insulating substrate (not shown). Is configured as a module.

  A heat sink 92 as a cooler is joined to the base plate 91. The heat sink 92 cools the silicon chips 11 </ b> C, 12 </ b> C, 13 </ b> C, 14 </ b> C, 15 </ b> C, 16 </ b> C, that is, the switching elements 11 to 16 (IGBT), by passing a predetermined amount of cooling water. In particular, the PN junction (IGBT junction) serving as a heat generation source is cooled. The PN junction (IGBT junction) is the thermally weakest part of the silicon chips 11C to 16C.

  The base plate 91 is provided with a temperature sensor 26 that detects the temperature (hereinafter referred to as base temperature) Tb of the base plate 91.

  Hereinafter, the temperature of the PN junction (IGBT junction) of the switching elements 11, 12, 13, 14, 15, 16 is defined as the junction temperature Tj, and the temperature difference between the junction temperature Tj and the base temperature Tb is defined as the junction temperature Tj. ~ Define temperature difference between bases Tbj.

  Next, the contents of control performed by the IGBT protection controller 70 will be described.

  The IGBT protection controller 70 is supplied with the voltage value Vdc of the DC power supply 3, the detected current values Iu and Iw of the phase current, and the detected rotational position θ of the PM motor 30.

  A control program shown in the flowchart of FIG. 3 is installed in the IGBT protection controller 70. In each of the processing units 71 to 77 of the IGBT protection controller 70, processing is sequentially executed according to the control program of FIG.

  In the following, it is assumed that the excavator performs grooving work and backfilling work. In the ditching work and backfilling work, the operation of turning the work machine and pressing the work machine against a natural ground or the like is repeatedly performed. At this time, in the PM motor 30 that drives the upper swing body 1, the rotation state and the lock state are repeated such as “rotation → lock → rotation → lock...”.

  When the PM motor 30 is locked, the rotational speed ω of the PM motor 30 becomes almost zero, and the inverter control controller 80 that gives a command to the inverter 10 using this as a feedback amount generates a large torque τ to the inverter 10. Therefore, a large amount of current continues to flow through the switching element, and the amount of heat generated by the switching element increases.

  Therefore, the IGBT protection controller 70 performs control for protecting the switching element from thermal destruction.

  The processing in FIG. 3 is performed every predetermined sampling time t. Therefore, the time at the n-th sampling is nt. In the following, the suffix “n” is given to the sign representing the variable to clarify the value at the time nt.

  First, in the IGBT loss calculation unit 74, the switching elements 11 to 16 (IGBT) based on the input voltage value Vdc of the DC power supply 3, phase current detection current values Iu and Iw, and data stored in the memory 78. Every time, the IGBT loss Wn (unit: joule J) between the times (n-1) t and nt is calculated.

  The IGBT loss Wn is obtained by the following equation.

IGBT loss Wn = steady loss W1n + switch loss W2n
Steady loss W1n = m ・ Vce (sat) ・ I ・ t
Switch loss W2n = Vdc.I. (. Tau.on + .tau.off) .f.t.a
However,
m: Modulation rate I: Phase current Iu, Iv, Iw
Vce (sat): ON (saturation) voltage of switching elements 11 to 16 (IGBT) Vdc: Power supply voltage τon: Rising time of switching elements 11 to 16 (IGBT) τoff: Falling time of switching elements 11 to 16 (IGBT) f: switching frequency a: coefficient Modulation rate m, saturation voltage Vce (sat), rise time τon, fall time τoff, switching frequency f, and coefficient a are stored in the memory 78 as specific constants. Of the phase current I, the V-phase current value Iv is obtained based on the input detected current values Iu and Iw (step 101).

  Next, the motor lock determination unit 72 determines whether the PM motor 30 is in a locked state or in a rotating state. For example, the speed signal processing unit 71 calculates the rotational speed ω based on the input rotational position θ. Then, a threshold value ω0 (for example, ± 50 rpm) for determining the locked state is set, and by determining whether or not the rotational speed ω of the PM motor 30 is equal to or less than the threshold value ω0, the PM motor It is determined whether or not 30 is locked (step 102).

  In the following, variables are defined as follows:

Tbjn: junction-to-base temperature difference at time nt fn (W): function for calculating junction-to-base temperature difference Tbjn when determined to be in the locked state at time nt gn (W): rotational state at time nt Tbn: Base temperature at time nt Tjn: Junction temperature at time nt Terr: Junction temperature upper limit value Tbj: Junction-base temperature difference Tbjn In the calculation unit 73, the junction-base temperature difference Tbjn at time nt is sequentially calculated for each sampling time t.

  That is, when it is determined that the PM motor 30 is in the locked state (determination Yes in step 102), the calculation formula for the locked state is based on the junction-to-base temperature difference Tbjn-1 calculated so far. That is, the function value is calculated using the function fn (W), and the current junction-base temperature difference Tbjn (= fn (W)) is sequentially calculated (step 103). On the other hand, when it is determined that the PM motor 30 is in the rotating state (determination No in step 102), the calculation formula for the rotating state is based on the junction-to-base temperature difference Tbjn-1 calculated so far. That is, the function value is calculated using the function gn (W), and the current junction-base temperature difference Tbjn (= gn (W)) is sequentially calculated (step 104).

  The functions fn (W) and gn (W) are represented by the following formulas, for example.

fn (W) = kL1 · Wn / (1 + τL1 / t)
+ (ΤL1 / t) / (1 + τL1 / t) · Tbjn-1 (1)
gn (W) = kR · Wn / (1 + τR / t)
+ (ΤR / t) / (1 + τR / t) · Tbjn-1 (2)
However,
kL1: primary delay gain in the locked state kR: primary delay gain in the rotating state τL1: primary delay time constant in the locked state τR: primary delay time constant in the rotating state Tbjn-1: previous time Junction to Base Temperature Difference at Sampling Time (n-1) t As shown in the above equations (1) and (2), the junction to base temperature difference Tbjn is the first-order lag (integral of the IGBT loss Wn). ). However, since the in-plane temperature distribution of the base plate 91 varies when the PM motor 30 is in the locked state compared to when it is in the rotating state, the gain kL1 of the first order lag when in the locked state is taken into consideration. Is set to a value larger than the first-order lag gain kR in the rotating state. That is, at the time of locking, the temperature distribution in the surface of the base plate 91 is biased. Therefore, the junction-to-base temperature difference Tbjn is obtained by taking into account the temperature rise due to the temperature distribution in the base plate surface.

  Furthermore, in the locked state, the temperature distribution in the surface of the base plate 91 is also captured as a first-order lag, and the junction-base temperature difference Tbjn (= fn (W)) can be calculated. In this case, the following formula (3) is used instead of the above formula (1).

fn (W) = Tbbjn + Tbbn (3)
However,
Tbbjn: The temperature difference between the temperature of the PN junction (IGBT junction) at the time nt and the temperature of the base plate 91 immediately below the PN junction (IGBT junction) (hereinafter, the temperature difference between the junction and the site directly below the junction)
Tbbn: temperature difference between the base plate 91 and the base temperature Tb immediately below the PN junction (IGBT junction) at the time nt (hereinafter, the temperature difference between the part directly below the junction and the base)
The above Tbbjn and Tbbn are each expressed by the following formula.

Tbbjn = kL2 / Wn / (1 + τL2 / t)
+ (ΤL2 / t) / (1 + τL2 / t) · Tbbjn-1 (4)
Tbbn = kL3 · Wn / (1 + τL3 / t)
+ (ΤL3 / t) / (1 + τL3 / t) · Tbbn-1 (5)
kL2: Gain of first-order lag in lock state (primary delay of IGBT loss Wn) kL3: Gain of first-order lag in lock state (first-order lag of temperature distribution in base plate surface) τL2: First-order lag in lock state (Primary delay of IGBT loss Wn) Time constant τL3: Primary delay in the locked state (primary delay of temperature distribution in the base plate surface) Time constant Tbbjn-1: Junction to di at the previous sampling time (n-1) t Temperature difference between the parts just below the junction Tbbn-1: Temperature difference between the parts just below the junction at the previous sampling time (n-1) t and the base-base temperature difference Tbjn When the current junction-base temperature difference Tbjn is calculated in this way, the adder 75 As shown in the following formula, a process of adding the current base temperature Tbn to the junction-to-base temperature difference Tbjn is executed, and the current Is determined.

Tjn = Tbn + Tbjn (Step 105)
In FIG. 4, the excavator performs a digging operation and a backfilling operation, and the PM motor 30 performs an operation of “lock (1) → rotation (1) → lock (2) → rotation (2) → lock (3)”. The calculation result of the temperature difference Tbj (Tbjn) between the junction and the base at the time of doing is illustrated. The horizontal axis represents time (seconds), and the vertical axis represents the junction-to-base temperature difference Tbj (° C).

  In “lock (1)” shown in FIG. 4, the junction-to-base temperature difference Tbjn is calculated by the function fn (W) for the lock state. For this reason, the junction-to-base temperature difference Tbjn increases with the elapse of time t determined to be in the locked state.

  In “Rotation (1)”, the junction-to-base temperature difference Tbjn is calculated based on the past “History of“ Lock (1) ”, that is, the junction-to-base temperature difference Tbjn−1 calculated so far. . In “Rotation (1)”, the junction-to-base temperature difference Tbjn is calculated by the function gn (W) for the rotation state. For this reason, the junction-to-base temperature difference Tbjn decreases with the elapse of the time t determined to be in the rotating state.

  “Lock (2)” is based on the past “Lock (1)” and “Rotation (1)” thermal history, that is, the junction-to-base temperature difference Tbjn−1 calculated so far. A temperature difference Tbjn is calculated. In “lock (2)”, the junction-to-base temperature difference Tbjn is calculated by the function fn (W) for the lock state. For this reason, the junction-to-base temperature difference Tbjn increases with the elapse of time t determined to be in the locked state. The same applies to “Rotation (2)” and “Lock (3)”. For this reason, when the lock state and the rotation state are repeated, the junction-to-base temperature difference Tbjn can be obtained very accurately. Therefore, since the junction temperature Tjn is obtained based on the accurately obtained junction-to-base temperature difference Tbjn, the junction temperature Tjn is extremely accurate.

  Next, the determination unit 76 determines whether or not the calculated junction temperature Tjn at the current sampling time exceeds the upper limit value Terr (step 106).

  If it is determined that the junction temperature Tjn at the current sampling time does not exceed the upper limit value Terr (determination No in step 106), the process returns to step 101 again and the same processing is repeated, but the junction temperature at the current sampling time is repeated. If it is determined that Tjn has exceeded the upper limit value Terr (Yes in step 106), it is determined that there is a possibility that the switching element may be thermally destroyed when the junction temperature further increases, and the process proceeds to step 107, where protection is performed. The sequence unit 77 executes a protection sequence for thermally protecting the switching element. In addition, since junction temperature Tjn is calculated | required for every switching element 11-16, if it judges that junction temperature Tjn exceeded upper limit Terr about at least 1 switching element, a protection sequence will be performed.

  As the protection sequence, for example, those listed below can be adopted.

1) Stop the PM motor 30.

  That is, the inverter control controller 80 calculates the torque value τ for making the deviation between the target rotational speed ωp of the PM motor 30 and the current rotational speed ω zero, but the junction temperature Tjn sets the upper limit value Terr. If exceeded, the IGBT protection controller 70 sends a command to the inverter control controller 80 to forcibly set the torque value τ to 0 regardless of the currently calculated torque value. The rotation of the motor is stopped by setting the value of the current flowing through to zero.

2) Gradually lower the torque (current) of the PM motor 30.

  If the torque is immediately reduced to 0 while the upper swing body 1 is turning, there is a risk of shock or danger to the operator or the operator around the hydraulic excavator. Therefore, when the junction temperature Tjn exceeds the upper limit value Terr, the IGBT protection controller 70 instructs the inverter control controller 80 to gradually decrease the torque value τ from the currently calculated torque value. The current value flowing through the PM motor 30 is gradually reduced.

  Also, a table in which the magnitude of the junction temperature Tjn is associated with the maximum torque value that can be output by the PM motor 30 is prepared, and when the junction temperature Tjn exceeds the upper limit value Terr, the IGBT protection controller 70 A command to calculate the torque value τ is sent to the control controller 80 with the maximum torque value corresponding to the current junction temperature Tjn as the upper limit, and the current value flowing through the PM motor 30 is limited.

3) Lower the switching frequency f to reduce the IGBT loss Wn.

  When the junction temperature Tjn exceeds the upper limit value Terr, the IGBT protection controller 70 sends a command to the inverter control controller 80 to generate a switching signal by reducing the switching frequency f, and switching elements 11 to 16 ( The IGBT loss Wn of the IGBT is reduced, and the heat generation of the switching elements 11 to 16 (IGBT) is suppressed. In this case, the torque of the PM motor 30 can be maintained, but the switching noise increases as the switching frequency f decreases.

4) The current vector is intentionally shifted to reduce the thermal load on a specific switching element (IGBT). However, the torque of the PM motor 30 is a current vector that can be maintained.

  When the junction temperature Tjn exceeds the upper limit value Terr, the IGBT protection controller 70 maintains the output torque of the PM motor 30 with respect to the inverter control controller 80, and the current value that flows through a specific phase and a specific switching element A command is sent to set the current vector to minimize.

  For example, in a sine wave drive (SM) interior magnet type motor (IPM), the torque τ can be calculated by the following equation.

τ = p (Ψ · iq + (Ld−Lq) · id · iq)
However,
τ: Torque p: Number of pole pairs Ψ: Torque constant iq: q-axis current id: d-axis current Ld: d-axis inductance Lq: q-axis inductance Current ratio determines the ratio and magnitude of d-axis current id and q-axis current iq Since they are vectors, there are many combinations of d-axis current id and q-axis current iq to output the same torque τ. Usually, in order to maximize the efficiency of the PM motor 30 and the inverter 10, the current value is minimized. However, when locked, it is not always optimal. For example, when the PM motor 30 is locked and the junction temperature Tjn exceeds the upper limit value Terr when the U-phase current value iu is 100A and the V-phase and W-phase current values iv and iw are -50A. By shifting the current vector by 30 °, the U-phase current value iu is (86.6 · k) A, the V-phase current value iv is 0A, and the W-phase current value iw is (−86.6 · k). ) A can reduce the thermal load on a specific switching element while maintaining the torque value τ. However, k is a constant (step 107).

  By the way, there are many types of construction machines such as a hydraulic excavator, and the rated output of the PM motor 30 necessary for turning the upper swing body 1 is various. For this reason, according to the kind of PM motor 30, the magnitude | size of the electric current which flows into the switching element of the inverter 10 is also various, and the heat sink 92 must also be prepared in various kinds with the cooling performance which differs according to it. For example, the flow rate of the cooling water flowing through the heat sink 92 is changed depending on the model.

  In this respect, in this embodiment described above, the junction temperature Tjn is obtained by adding the base temperature Tbn to the junction-base temperature difference Tbjn (Tjn = Tbn + Tbjn), and the junction-base temperature difference Tbjn. Is calculated by an arithmetic expression independent of the cooling capacity of the heat sink 92. Therefore, even when the heat sink 92 is changed to one having a different cooling performance, the temperature of the switching element (junction temperature Tjn) can be calculated with a common calculation program. For this reason, the IGBT protection controller 70 can be made common, the versatility of the controller is improved, and the parts are made common and the cost is reduced.

  In the above-described embodiment, the description has been made assuming a hydraulic excavator. However, the present invention can be similarly applied to other construction machines such as a wheel loader and a bulldozer other than the hydraulic excavator. Further, the description has been made assuming the configuration in which the PM motor 30 drives the upper swing body 1 (FIG. 6). However, instead of the configuration in which the PM motor 30 drives the upper swing body 1, a work machine (boom, arm, bucket) is provided. The present invention can also be applied to the case of a configuration in which the above is driven. Alternatively, the present invention can also be applied to a configuration in which the PM motor 30 drives the upper swing body 1 and the PM motor 30 drives a work implement (boom, arm, bucket).

  In the embodiments, the description has been made assuming a construction machine hybrid system. However, the present invention can naturally be applied to a system in which a drive source is only an electric motor (a system not used in combination with an engine).

FIGS. 1A and 1B are diagrams illustrating the configuration of the inverter and the configuration of the PM motor, respectively. FIG. 2 is a configuration diagram of the motor control device of the embodiment. FIG. 3 is a flowchart showing a processing procedure performed by the IGBT protection controller shown in FIG. FIG. 4 is a diagram illustrating the calculation result of the temperature difference between the junction and the base. FIG. 5 is a perspective view showing the configuration of the inverter of the embodiment and a cooler for cooling the inverter. FIG. 6 is a block diagram showing a part for driving and controlling the upper-part turning body in the hybrid system of the construction machine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Inverter 11-16 Switching element (IGBT), 30 PM motor, 70 IGBT protection controller, 80 Inverter control controller

Claims (5)

A motor for driving the construction machine;
A switching element that is operated according to the input switching signal and outputs a drive signal to the motor;
A rotational speed detection means for detecting the rotational speed of the motor;
First control means for outputting a switching signal to the switching element using the rotational speed measured by the rotational speed detection means as a feedback amount;
Determining means for determining whether the motor is in a locked state or in a rotating state;
When it is determined that the motor is in the locked state, the temperature of the current switching element is sequentially calculated using the calculation formula for the locked state based on the temperature of the switching element calculated up to the previous time. With
When it is determined that the motor is in a rotating state, the temperature of the current switching element is sequentially calculated using a calculation formula for the rotating state based on the temperature of the switching element calculated up to the previous time. ,
When it is determined that the motor has switched from the locked state to the rotating state, the rotational state arithmetic expression is calculated based on the previous switching element temperature calculated using the locked state arithmetic expression. To calculate the temperature of this switching element,
When it is determined that the motor has switched from the rotational state to the locked state, the rotational state arithmetic expression is calculated based on the previous switching element temperature calculated using the rotational state arithmetic expression. Temperature calculating means for calculating the temperature of the current switching element ,
A motor control device for a construction machine, comprising: a second control unit that performs control to thermally protect the switching element according to the temperature of the switching element calculated by the temperature calculation unit. The switching element is a switching element constituting an inverter,
The inverter is configured by mounting a switching element on a base plate,
A cooler for cooling the switching element is joined to the base plate,
Temperature detecting means for detecting the temperature of the base plate is provided;
The temperature calculating means includes
If it is determined that the motor is in the locked state, based on the temperature difference between the switching element temperature and the base plate temperature calculated up to the previous time, the calculation formula for the locked state is used. The temperature difference between the switching element temperature and the base plate temperature is sequentially calculated,
If it is determined that the motor is in a rotating state, based on the temperature difference between the temperature of the switching element and the temperature of the base plate calculated up to the previous time, this time using the calculation formula for the rotating state, Sequentially calculate the temperature difference between the temperature of the switching element and the temperature of the base plate,
If it is determined that the motor has switched from the locked state to the rotating state, based on the temperature difference between the temperature of the previous switching element and the temperature of the base plate calculated using the calculation equation for the locked state. Using the calculation formula for the rotation state, the temperature difference between the temperature of the current switching element and the temperature of the base plate is calculated,
When it is determined that the motor is switched from the rotation state to the lock state, based on the temperature difference between the temperature of the previous switching element and the temperature of the base plate calculated using the calculation equation for the rotation state. , By calculating the temperature difference between the temperature of the current switching element and the temperature of the base plate, using the calculation formula for the rotation state,
Further, the temperature of the switching element is calculated by adding the temperature of the base plate detected by the temperature detecting means to the temperature difference.
The motor control device for a construction machine according to claim 1. The motor is a motor that drives a swing body of a construction machine.
The motor control device according to claim 1. The second control means includes
When the temperature of the switching element calculated by the temperature calculating means exceeds a predetermined threshold value, a switching signal for thermally protecting the switching element is sent from the first control means to the switching element. Giving a command to the first control means to be output
The motor control device for a construction machine according to claim 1. In a program for controlling a motor that drives a construction machine and that is driven by a drive signal given from a switching element,
Determining whether the motor is in a locked state or in a rotating state;
When it is determined that the motor is in the locked state, the temperature of the current switching element is sequentially calculated using the calculation formula for the locked state based on the temperature of the switching element calculated up to the previous time. With
When it is determined that the motor is in a rotating state, the temperature of the current switching element is sequentially calculated using a calculation formula for the rotating state based on the temperature of the switching element calculated up to the previous time. ,
When it is determined that the motor has switched from the locked state to the rotating state, the rotational state arithmetic expression is calculated based on the previous switching element temperature calculated using the locked state arithmetic expression. To calculate the temperature of this switching element,
When it is determined that the motor has switched from the rotational state to the locked state, the rotational state arithmetic expression is calculated based on the previous switching element temperature calculated using the rotational state arithmetic expression. To calculate the temperature of this switching element,
A motor control program for a construction machine, which performs control for thermally protecting the switching element in accordance with the calculated temperature of the switching element.

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