WO2008026544A1

WO2008026544A1 - Hydraulic unit and method of controlling speed of motor in hydraulic unit

Info

Publication number: WO2008026544A1
Application number: PCT/JP2007/066559
Authority: WO
Inventors: Tetsuo Nakata; Junichi Miyagi; Yasuto Yanagida
Original assignee: Daikin Industries, Ltd.
Priority date: 2006-08-30
Filing date: 2007-08-27
Publication date: 2008-03-06
Also published as: CN101360917B; KR20080087084A; KR100954697B1; CN101360917A; EP1965083A4; JP4425253B2; ATE528512T1; JP2008057611A; EP1965083A1; US20090097986A1; EP1965083B1

Abstract

A hydraulic unit having an inverter (14) for supplying electric power to a motor (15), a load sensor (17) for sensing a load on a hydraulic pump (16A), a rotation sensor (19) for sensing the rotation speed of the motor (15), a current-command-value calculation means (12) for calculating an electric-current command value so that the difference between a speed command value representing a target rotation speed of the motor (15) and the rotation speed of the motor (15) is converged to zero, correction means (18A) for correcting the electric-current command value based on the load on the hydraulic pump (16A), and control signal creation means for outputting a control signal to the inverter (14) based on the corrected electric-current command value.

Description

Specification

Hydraulic unit and motor speed control method in hydraulic unit

The present invention relates to a hydraulic unit that drives a hydraulic pump by a motor.

Background art

Conventionally, in a hydraulic unit using a hydraulic pump directly connected to a motor as a drive source, a speed control (PI control) calculation is executed by comparing the motor speed command value with the current rotational speed. The current command value is calculated, and current control based on the current command value is realized by the inverter. And the pressure oil is discharged from the hydraulic pump by driving a motor controlled by an inverter. (For example, Patent Document 1).

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-162860

Disclosure of the invention

Problems to be solved by the invention

In such a hydraulic unit, when the total amount of oil discharged from the hydraulic pump by driving the hydraulic pump increases, the pressure (hydraulic pressure) of the oil increases. This increase in hydraulic pressure increases the load on the hydraulic pump at the time of discharge, and increases the load torque of the motor.

[0005] For this reason, in the hydraulic unit, for example, when a stepped speed command value is given, the load on the hydraulic pump suddenly increases when the rotational speed of the motor suddenly increases in response to the speed command value. As a result, the load torque of the motor suddenly increases. If the load torque of the motor suddenly increases, the speed control configured with PI control cannot follow, and the rotational speed of the motor may decrease.

[0006] As a technique for preventing a decrease in the rotational speed of the motor, for example, a technique of improving the processing speed of a microcomputer that performs PI control, shortening the control cycle of PI control, and improving control responsiveness is considered. It is done. If this method is used, the cost of the microcomputer will increase. In addition, since there is a physical limit in improving the processing speed of the microcomputer, this method cannot effectively prevent a reduction in the rotational speed of the motor. [0007] As another method, a method of estimating the load torque from acceleration information obtained by differentiating the rotation speed of the motor and using the load torque for speed control is conceivable. However, since the rotation speed is discrete information, the noise component increases due to differentiation. For this reason, if speed control is performed using load torque, the operation may become unstable.

[0008] Further, if the gain of speed control is increased in order to improve the responsiveness to load fluctuations, oscillation may occur when a step-like speed command value is given.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of improving the followability of the rotational speed of the motor with respect to changes in the load of the hydraulic pump. And

Means for solving the problem

[0010] A first aspect of the hydraulic unit according to the present invention is a hydraulic unit that drives a hydraulic pump (16A) by a motor (15) and supplies oil to an actuator. An inverter (14) for supplying electric power, a load sensor (17) for detecting a load of the hydraulic pump (16A), a rotation sensor (21) for detecting a rotation speed of the motor (15), and the motor Current command value calculating means (12) for calculating a current command value so that the deviation between the speed command value representing the target rotation speed in (15) and the rotation speed of the motor (15) converges to zero; Correction means (18A; ···; 18D) for correcting the current command value based on the pump load, and control for outputting a control signal to the inverter (14) based on the corrected current command value And a signal generation means (13).

[0011] A second aspect of the hydraulic unit is the first aspect, wherein the correction means (18A

18Ό) is characterized in that the current command value is corrected so as to increase the rotational speed of the motor (15) as the load of the hydraulic pump (16A) increases.

[0012] Further, a third aspect of the hydraulic unit is the first or second aspect thereof, wherein the correction means (18A; ··; 18D) includes a load of the hydraulic pump (16A). The current command value is increased with the increase.

[0013] Further, the fourth aspect of the hydraulic unit is any one of the first to third aspects, wherein the correction means (18A) performs correction using a preset correction coefficient (Kf). A value (If) is acquired, and the correction value (If) is added to the current command value. [0014] Further, a fifth aspect of the hydraulic unit is any one of the first to third aspects, wherein the correction means (18B; 18C; 18D) uses a data table DT acquired in advance. Then, a correction value (If) is obtained, and the correction value (If) is added to the current command value.

[0015] Further, a sixth aspect of the hydraulic unit is any one of the first to fifth aspects, wherein the load sensor (17) is provided in a discharge line (19) of the hydraulic pump (16A). It is a pressure sensor (17) that detects the oil pressure.

[0016] Further, according to a seventh aspect of the hydraulic unit, in the hydraulic unit that supplies the oil to the actuator by driving the hydraulic pump (16A) by the motor (15) controlled by the inverter (14). A method for controlling the speed of the motor (15), comprising: a) detecting the load of the hydraulic pump (16A), b) detecting the rotational speed of the motor (15), and c) the motor (15). ) Calculating the current command value so that the deviation between the speed command value representing the target rotation speed and the rotation speed of the motor (15) converges on the opening; d) the load of the hydraulic pump (16A) And a step of: e) outputting a control signal to the inverter (14) based on the corrected current command value based on the current command value.

Yes

The invention's effect

[0017] According to the first to seventh aspects of the hydraulic unit according to the present invention, the current command value is corrected based on the load of the hydraulic pump, so that the load of the hydraulic pump (load hydraulic pressure) varies. It is possible to improve the followability of the rotational speed of the motor with respect to the motor.

In particular, according to the second aspect of the hydraulic unit according to the present invention, the current command value is corrected so as to increase the rotational speed of the motor as the load of the hydraulic pump increases. It is possible to prevent a decrease in the rotation speed of the motor due to an increase in the motor.

The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Brief Description of Drawings

FIG. 1 is a schematic view showing a configuration of a hydraulic unit according to an embodiment.

FIG. 2 is a schematic diagram showing the configuration of a hydraulic unit that does not have a correction unit. FIG. 3 is a diagram showing an operation state when a stepped speed command is given in the hydraulic unit according to the embodiment.

FIG. 4 is a diagram showing an operation state when a stepped speed command is given to a hydraulic unit without a correction unit!

FIG. 5 is a schematic diagram showing a hydraulic unit having a correction unit capable of acquiring a correction value using a data table.

FIG. 6 is a schematic diagram showing a hydraulic unit that drives two hydraulic pumps with one motor.

FIG. 7 is a schematic diagram showing a hydraulic unit in which two hydraulic pumps are connected in series. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022] <Configuration>

FIG. 1 is a schematic diagram showing the configuration of a hydraulic unit 10A according to an embodiment of the present invention. The hydraulic unit 10A is connected to, for example, a molding machine and supplies oil as a working fluid to an actuator (not shown) that uses hydraulic pressure as a power source.

As shown in FIG. 1, the hydraulic unit 10 A includes a controller 20, an inverter unit 14, a motor 15, a hydraulic pump 16 A, a pressure sensor 17, and a pulse generator 21. In the hydraulic unit 10A having such a configuration, oil is sucked from a tank (not shown) by a hydraulic pump 16A driven by a motor 15, and the oil is discharged. The discharged oil passes through a discharge line 19 and is supplied to an actuator such as a hydraulic cylinder or a hydraulic motor.

[0024] The pressure sensor 17 functions as a load sensor for detecting the load of the hydraulic pump. And

The pressure sensor 17 detects the oil pressure (also referred to as “current pressure” or “load oil pressure”) in the discharge line 19 of the hydraulic pump.

[0025] The pulse generator 21 functions as a rotation sensor that outputs a noise signal for detecting the rotation speed of the motor to the controller 20 (speed detection unit 22).

The inverter unit 14 controls the number of rotations of the motor 15 by performing switching based on a control signal from the controller 20.

[0027] The controller 20 includes a P-Q control unit 11, a current command value calculation unit 12, a correction unit 18A, and a control signal. A signal generation unit 13 and a speed detection unit 22 are included. Then, the controller 20 outputs a control signal for driving the inverter.

[0028] The P—Q control unit 11 generates a discharge pressure-discharge flow rate characteristic (P—Q characteristic) based on a set pressure and a set flow rate from a host system such as a molding machine. Then, the PQ controller 11 outputs the speed command value with the current pressure from the pressure sensor 17 as an input.

[0029] A current command value calculation unit (also referred to as "PI control unit") 12 performs proportional integration (PI) control with the speed command value and the current speed as inputs, and outputs a current command value. More specifically, the PI control unit 12 calculates the current command value so that the deviation between the speed command value indicating the target rotation speed of the motor 15 and the rotation speed of the motor 15 converges to zero.

The correction unit 18A corrects the current command value based on the current pressure from the pressure sensor 17.

. Details will be described later.

[0031] The control signal generation unit 13 generates a control signal for controlling the inverter unit 14 based on the corrected current command value.

[0032] <Correction unit>

Next, the correction unit 18A will be described in detail.

[0033] FIG. 2 is a schematic diagram showing a configuration of a general hydraulic unit 10B. The hydraulic unit 10B has the same configuration as the hydraulic unit 10A, except that the correction unit 18A is not provided.

[0034] The molding machine to which the hydraulic unit 10B is connected is required to have high responsiveness from the viewpoint of mass production. For this reason, in the hydraulic unit 10B that drives the molding machine, stepped speed commands are given in a short cycle.

[0035] When the total amount of oil discharged from the hydraulic pump 16A increases, the hydraulic pressure (load hydraulic pressure) in the discharge line 19 of the hydraulic pump 16A increases. When the load hydraulic pressure increases, the load on the hydraulic pump 16A during discharge increases. That is, the load hydraulic pressure and the load torque of the motor 15 are generally in a proportional relationship, and as the load hydraulic pressure increases, the load torque of the motor 15 increases.

[0036] Therefore, when a stepped speed command is given in hydraulic unit 10B, the rotational speed of motor 15 increases rapidly in response to the speed command value. Rotation speed of motor 15 As the pressure increases, the load hydraulic pressure increases rapidly. As the load hydraulic pressure increases, the load torque increases rapidly. As a result, the speed control by PI control cannot follow, and the rotational speed of the motor 15 decreases.

[0037] In order to prevent such a decrease in the rotational speed of the motor 15 due to an increase in the load torque, it is sufficient that the generated torque of the motor 15 increases as the load torque increases. Here, since the generated torque of the motor 15 and the motor current are in a proportional relationship, in order to increase the generated torque of the motor 15, the motor current, that is, the current command value only needs to be increased.

That is, in short, if the current command value is changed along with the fluctuation of the load hydraulic pressure, the followability of the rotation speed of the motor 15 with respect to the fluctuation of the load hydraulic pressure can be improved. Further, if the current command value is increased as the load hydraulic pressure is increased, it is possible to prevent a decrease in the rotational speed of the motor 15.

Therefore, in the hydraulic unit 10A according to the present embodiment, a correction unit 18A that corrects the current command value based on the load hydraulic pressure is provided. In the correction unit 18A, the correction value (current correction value) If is acquired using the current pressure (pressure detection value) Pd detected by the pressure sensor 17 and the correction coefficient Kf acquired in advance. Then, the correction value If is added (added) to the current command value output from the current command value calculation unit 12.

[0040] According to the correction unit 18A, the current command value is corrected based on the load of the hydraulic pump 16A, that is, the oil pressure (load oil pressure) in the discharge line 19. Therefore, it is possible to improve (improve) the follow-up performance of the rotational speed of the motor 15 with respect to fluctuations in the load (load hydraulic pressure) of the hydraulic pump 16A.

[0041] As the correction coefficient Kf, a coefficient acquired in advance by a test is used. Specifically, the correction coefficient Kf is set so that the correction unit 18A can acquire a current command value required to prevent a decrease in the rotational speed of the motor 15 and follow the speed command. In addition, the correction coefficient Kf is expressed to be set so that the shortage of the current command value required to prevent the motor 15 from rotating and follow the speed command can be acquired as a correction value. I'll do it with power.

As described above, by using the correction coefficient Kf set so that the shortage of the current command value can be acquired as the correction value, the rotation speed of the motor 15 is given by the speed command value. The rotation speed can be controlled.

[0043] Further, the correction value If acquired using the correction coefficient Kf increases as the load hydraulic pressure increases. For this reason, the correction unit 18A can correct the current command value so as to increase the rotation speed of the motor 15 as the load hydraulic pressure increases, and the rotation speed of the motor 15 decreases as the load hydraulic pressure increases. Is prevented.

Next, the operation when the stepped speed command SC is given in the hydraulic unit 10A will be specifically described. FIG. 3 is a diagram showing the behavior of the hydraulic unit 10A according to the present embodiment when a step speed command SC is given.

[0045] As shown in Fig. 3 (a), when the stepped speed command SC is given in the hydraulic unit 10A, the rotational speed Rsl of the motor 15 rapidly increases in response to the speed command SC. Then, the pressure Pdl of the oil discharged from the hydraulic pump 16A increases rapidly, and the load torque of the motor 15 increases.

In the hydraulic unit 10A, the correction unit 18A obtains a correction value If that increases the value as the load hydraulic pressure Pdl increases. Then, the correction value If is added to the output from the current command value calculation unit 12, and the corrected current command value Icl is acquired (see FIG. 3B). In this way, the current command value Icl increases with the increase in the load hydraulic pressure Pdl, so that a decrease in the rotational speed Rsl of the motor 15 due to an increase in the load torque is prevented. Then, the rotational speed Rsl of the motor 15 can be made to follow the rotational speed given by the speed command SC.

[0047] Here, the operation when the stepped speed command SC is given in the hydraulic unit 10A is compared with the operation when given in the hydraulic unit 10B not having the correction unit 18A. FIG. 4 is a diagram showing the behavior of the hydraulic unit 10B when the stepped speed command SC is given.

[0048] As shown in FIG. 4 (a), when the stepped speed command SC is given in the hydraulic unit 10B, the motor 15 is affected by the increase in the load hydraulic pressure Pd2 due to the rapid increase in the rotational speed Rs2 of the motor 15. The rotational speed Rs2 of 15 has decreased.

[0049] Further, when FIG. 3 (b) is compared with FIG. 4 (b), the magnitude of the current command value is different in the section BT. The difference in the magnitude of the current command value is that the motor 15 The appropriate current command value required to make the rotation speed follow the speed command sc is obtained (calculated)! /, N! /, Indicating that it is! / (Fig. 4 (b)).

[0050] In this way, with only speed control configured by PI control, when a rapid speed command such as a stepped speed command SC is given, the rotational speed of the motor 15 follows the speed command. I can't!

In the present embodiment, a correction value If that increases as the load hydraulic pressure Pd increases is acquired using the load hydraulic pressure Pd detected by the pressure sensor 17 in the correction unit 18A and the correction coefficient Kf acquired in advance. Is done. Then, the correction value If is added to the current command value output from the current command value calculation unit 12.

[0052] As described above, by adding the correction value If acquired based on the load hydraulic pressure Pdl to the current command value output from the current command value calculation unit 12 in a feedforward manner, the current command value Icl Can be increased following the increase in the load hydraulic pressure Pdl. Then, it is possible to prevent a decrease in the rotational speed Rsl of the motor 15 due to an increase in load torque.

Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

[0054] For example, in the above embodiment, the force S that has acquired the correction value If using the correction coefficient Kf acquired in advance by the correction unit 18A is not limited to this. FIG. 5 is a schematic diagram showing a hydraulic unit 10C having a correction unit 18B that can acquire the correction value If using the data table DT.

Specifically, as shown in FIG. 5, the correction unit 18B performs correction using the data table DT indicating the relationship between the load oil pressure (pressure detection value) Pd acquired in advance and the correction value If. The value If may be obtained (calculated).

[0056] According to this, even when the load pressure and the correction value required to follow the speed command are not proportional, an appropriate correction value for the load pressure Pd from the pressure sensor 17 is obtained. It is possible to get If.

In the above embodiment, the force S that drives the hydraulic unit 10A using one hydraulic pump 16A is not limited to this. [0058] Specifically, the hydraulic unit may be driven using a plurality of hydraulic pumps. FIG. 6 is a schematic diagram showing a hydraulic unit 10D that drives two hydraulic pumps 16A and 16B with one motor.

[0059] For example, as shown in FIG. 6, when the hydraulic unit 10D is configured by two hydraulic pumps 16A and 16B, any hydraulic pump is driven from the PQ control unit 11 in accordance with the pump switching. (Pump drive information) indicating whether or not the correction is performed is output to the correction unit 18C. Then, in the correction unit 18C, the data table for acquiring the correction value If is switched according to the pump drive information, and the correction value If corresponding to the pump being driven is acquired.

[0060] When the two hydraulic pumps 16A and 16B are driven simultaneously, the two hydraulic pumps

A data table showing the relationship between the load hydraulic pressure (pressure detection value) Pd and the correction value If when 16A and 16B are driven simultaneously is used to obtain the correction value If.

[0061] Also, the two hydraulic pumps 16A, 16B may not be connected in parallel. FIG. 7 is a schematic diagram showing a hydraulic unit in which two hydraulic pumps are connected in series. As shown in FIG. 7, when two hydraulic pumps are connected in series so that oil discharged from one hydraulic pump 16B is sucked into the other hydraulic pump 16A, the downstream hydraulic pump 1 The pressure of oil discharged from 6A is detected by the pressure sensor (17). The current command value is corrected based on the hydraulic pressure discharged from the downstream hydraulic pump 16A.

The present invention has been described in detail. The above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that the myriad variations S that are not illustrated can be assumed without departing from the scope of the present invention.

Claims

The scope of the claims

A hydraulic unit that drives a hydraulic pump (16A) by a motor (15) and supplies oil to an actuator,

An inverter (14) for supplying power to the motor (15);

A load sensor (17) for detecting a load of the hydraulic pump (16A);

A rotation sensor (21) for detecting the rotation speed of the motor (15);

Current command value calculation means (12) for calculating a current command value so that the deviation between the speed command value representing the target rotation speed of the motor (15) and the rotation speed of the motor (15) converges to zero; ,

Correction means (18A; •••; 18D) for correcting the current command value based on the load of the hydraulic pump;

Control signal generating means (13) for outputting a control signal to the inverter (14) based on the corrected current command;

A hydraulic unit comprising:

The hydraulic unit according to claim 1,

The correction means (18A;... 18D) corrects the current command value so as to increase the rotational speed of the motor (15) as the load of the hydraulic pump (16A) increases. Hydraulic unit to do.

In the hydraulic unit according to claim 1 or claim 2,

The correction means (18A; ···; 18D) increases with the load of the hydraulic pump (16A).

A hydraulic unit that increases the current command value.

In the hydraulic unit according to claim 1 or claim 2,

The correction unit (18A) obtains a correction value (If) using a preset correction coefficient (Kf), and adds the correction value (If) to the current command value. . The hydraulic unit according to claim 3,

The correction unit (18A) obtains a correction value (If) using a preset correction coefficient (Kf), and adds the correction value (If) to the current command value. . In the hydraulic unit according to claim 1 or claim 2, The correction means (18B; 18C; 18D) acquires a correction value (If) using a data table DT acquired in advance, and adds the correction value (If) to the current command value. unit.

[7] In the hydraulic unit according to claim 3,

The correction means (18B; 18C; 18D) acquires a correction value (If) using a data table DT acquired in advance, and adds the correction value (If) to the current command value. unit.

[8] In the hydraulic unit according to claim 1 or claim 2,

The hydraulic unit, wherein the load sensor (17) is a pressure sensor (17) for detecting oil pressure in a discharge line (19) of the hydraulic pump (16A).

[9] The hydraulic unit according to claim 3,

[10] In the hydraulic unit according to claim 4,

[11] In the hydraulic unit according to claim 5 or claim 7,

[12] The hydraulic unit according to claim 6,

[13] A method for controlling the speed of the motor (15) in a hydraulic unit that drives a hydraulic pump (16A) by a motor (15) controlled by an inverter (14) and supplies oil to an actuator,

a) detecting the load of the hydraulic pump (16A);

b) detecting the rotational speed of the motor (15);

c) Speed command value indicating the target rotational speed of the motor (15) and the rotation of the motor (15) Calculating the current command value so that the deviation from the speed converges to zero;

d) correcting the current command value based on the load of the hydraulic pump (16A); e) outputting a control signal to the inverter (14) based on the corrected current command value;

A speed control method for a motor (15), comprising: