JP2008248816A - Compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a gas filling time to a tank by increasing a gas discharge amount when a suction pressure is lowered.
An air compressor (11) includes a compression unit (14) driven by an electric motor (12) and a control circuit (26) for controlling driving of the electric motor (12). A suction pressure sensor 24 is connected to the suction port 19 of the compression unit 14 via a pressure pipe 25. The electric motor 12 increases the rotational speed of the electric motor 12 according to the suction pressure Pin when the suction pressure Pin detected by the suction pressure sensor 24 falls below the reference pressure range P0.
[Selection] Figure 2

Description

  The present invention relates to a compressor that compresses a gas such as air and stores the compressed gas in a tank, and more particularly to a compressor that is suitable for use in a booster that boosts (increases) a previously compressed gas.

  In general, an air compressor including a compressor that compresses air by being driven by an electric motor and a tank that stores compressed air generated by the compressor is known as a compressor (for example, Patent Documents). 1). And the air compressor by a prior art was set as the structure which brings the pressure in a tank close to a target value quickly, controlling the rotation speed of an electric motor according to the pressure in a tank, for example, preventing an overshoot.

JP 2004-36411 A

  By the way, although the air compressor by a prior art controls the rotation speed of an electric motor according to the pressure in a tank, the suction pressure supplied to a suction inlet was not considered at all. That is, since the air compressor generally sucks and compresses atmospheric air, the suction pressure does not change greatly.

  On the other hand, for example, when an air compressor is used as a booster (booster), the suction port of the air compressor is connected to the factory piping, and the air compressor has an air pressure higher than the atmospheric pressure supplied from the factory piping. The compression operation is performed. In this case, the pressure in the factory pipe changes depending on the usage status of other pneumatic equipment connected to the factory pipe, and may be lower than a predetermined pressure. Thus, when the suction pressure of the air compressor is reduced, the power of the electric motor has a margin, but the amount of discharge air is reduced as compared with the case where air of a predetermined pressure is compressed. As a result, there is a problem that the time for filling the tank with air becomes long.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to increase the gas discharge amount and reduce the gas filling time to the tank when the suction pressure is reduced. It is to provide a compressor.

  In order to solve the above-described problems, the present invention includes a driving unit that rotates and drives, a compression unit that compresses the gas that is driven according to the number of rotations of the driving unit and that is supplied from the suction port, and is discharged from the compression unit. The present invention is applied to a compressor provided with a tank for storing compressed gas and control means for controlling the rotational speed of the driving means.

  A feature of the configuration adopted by the invention of claim 1 is that suction pressure detection means for detecting a suction pressure of gas supplied to the suction port of the compression section is provided, and the control means is based on the suction pressure detection means. When the detected pressure is lower than a predetermined reference pressure range, the number of revolutions of the driving unit is set higher than when the detected pressure is within the reference pressure range.

  According to a second aspect of the present invention, the control means is configured to continuously increase the rotational speed of the driving means according to the detected pressure when the pressure detected by the suction pressure detecting means is lower than a reference pressure range. Yes.

  According to a third aspect of the present invention, when the detected pressure by the suction pressure detecting means is lower than a reference pressure range, the control means increases the rotational speed of the driving means stepwise according to the detected pressure. Yes.

  According to the first aspect of the present invention, when the detected pressure by the suction pressure detecting means is lower than the reference pressure range, the control means increases the rotational speed of the driving means compared to when the detected pressure is within the reference pressure range. It is configured to do. For this reason, even when the gas discharge rate decreases as the suction pressure decreases, the gas discharge rate can be increased by increasing the rotational speed of the driving means, and the gas filling time for the tank can be reduced. It can be shortened.

  According to the invention of claim 2, the control means continuously increases the rotational speed of the drive means according to the detected pressure when the detected pressure by the suction pressure detecting means is lower than the reference pressure range. When the pressure is slightly decreased, the rotational speed of the driving means can be slightly increased, and when the suction pressure is greatly decreased, the rotational speed of the driving means can be greatly increased. For this reason, the rotation speed of the drive means can be increased in accordance with the decrease in the suction pressure, and the decrease in the amount of gas discharged from the compression section can be compensated.

  According to the invention of claim 3, when the pressure detected by the suction pressure detecting means is lower than the reference pressure range, the control means increases the rotational speed of the driving means stepwise according to the detected pressure. Similarly to the invention, the rotational speed of the driving means can be increased in accordance with the decrease in the suction pressure, and the decrease in the amount of gas discharged from the compression section can be compensated.

  Hereinafter, a booster type air compressor will be described as an example of a compressor according to an embodiment of the present invention and will be described in detail with reference to the accompanying drawings.

  In the figure, reference numeral 1 denotes a compressed air supply source for supplying compressed air. The compressed air supply source 1 stores compressed air having a rated pressure of, for example, about 0.5 MPa in the buffer tank 2 and through the buffer tank 2. Connected to the factory piping 3. Thereby, the compressed air supply source 1 supplies the compressed air of the rated pressure into the factory piping 3.

  A plurality of pneumatic devices 4 </ b> A to 4 </ b> N are connected in the middle of the factory piping 3. For this reason, the pressure in factory piping 3 changes according to the use condition of pneumatic equipment 4A-4N.

  11 is a booster type air compressor as a booster connected in the middle of the factory piping 3, and the air compressor 11 includes an electric motor 12, a compression unit 14, and a tank, which will be described later, as shown in FIGS. 21 and a control circuit 26 and the like.

  Reference numeral 12 denotes an electric motor as drive means, and the electric motor 12 is connected to an inverter circuit 13. The inverter circuit 13 includes a converter that converts a sine wave alternating current into a direct current, and a plurality of transistors (all not shown) that reversely convert the direct current into a variable frequency alternating current. In the inverter circuit 13, ON / OFF of the transistor is controlled by the control circuit 26, and the rated frequency of the electric motor 12 can be arbitrarily changed. Therefore, the output shaft of the electric motor 12 is rotationally driven at a rotational speed corresponding to the AC variable frequency output from the inverter circuit 13.

  Reference numeral 14 denotes a compression unit that is driven according to the number of rotations of the electric motor 12, and the compression unit 14 is constituted by, for example, a two-cylinder reciprocating compression mechanism. At this time, the compression unit 14 is mounted on a crankcase 15 provided on a tank 21 described later, a crankshaft 16 rotatably provided in the crankcase 15, and 2 mounted on the upper side of the crankcase 15. A cylinder 17 and the like are provided.

  The rear end side of the crankshaft 16 protrudes from the crankcase 15 and a pulley 16A is attached. The pulley 16A is connected to the output shaft of the electric motor 12 via a belt (not shown). Thereby, the rotation of the electric motor 12 is transmitted to the crankshaft 16 via the pulley 16A and the like.

  On the other hand, a piston (not shown) is inserted into each cylinder 17 so as to be able to reciprocate. At this time, the piston is connected to the crankshaft 16 through a connecting rod or the like, and reciprocates in the cylinder 17 according to the rotation of the crankshaft 16. In addition, a cylinder head 17A in which a suction chamber and a discharge chamber (both not shown) are defined is provided at the tip of each cylinder 17. The suction chamber is connected to a suction port 19 via a suction pipe 18, and the discharge chamber is connected to a tank 21 via a discharge pipe 20. Thereby, the compression unit 14 compresses the air supplied from the suction port 19 in the cylinder 17 and discharges the compressed air toward the tank 21 when the piston reciprocates in each cylinder 17.

  Reference numeral 21 denotes a tank for storing compressed gas discharged from the compression unit 14. The tank 21 is formed in a substantially cylindrical shape with both ends closed, and the electric motor 12, the compression unit 14, and the like are placed on the upper side. ing. Further, the tank 21 is connected to the compression unit 14 via the discharge pipe 20 and is connected to the pneumatic device 4X. And since the tank 21 stores the compressed air whose pressure is higher than the pressure (suction pressure) in the factory piping 3, the pneumatic equipment 4X is driven using this high-pressure compressed air.

  The tank 21 is provided with a pressure sensor 22, and the output side of the pressure sensor 22 is connected to a control circuit 26 described later. The pressure sensor 22 detects the tank pressure Pt in the tank 21 and outputs a detection signal corresponding to the pressure value to the control circuit 26 described later.

  Reference numeral 23 denotes a control box mounted on the tank 21, and a suction pressure sensor 24 and a control circuit 26 which will be described later are provided in the control box 23.

  Reference numeral 24 denotes a suction pressure sensor (suction pressure detection means) for detecting the suction pressure of air supplied to the suction port 19. The suction pressure sensor 24 is disposed in the control box 23 and is connected via a pressure pipe 25. It is connected to the suction port 19. Thereby, the suction pressure sensor 24 detects the pressure of the air supplied to the suction port 19 (suction pressure Pin), and outputs a detection signal corresponding to the pressure value to the control circuit 26 described later.

  Reference numeral 26 denotes a control circuit as a control means for controlling the number of revolutions of the electric motor 12, and the control circuit 26 is configured as an arithmetic processing circuit including a CPU, for example, and has a storage circuit including a ROM, a RAM, and the like. Yes. The sensors 22 and 24 are connected to the input side of the control circuit 26, and the inverter circuit 13 is connected to the output side of the control circuit 26.

  Here, the control circuit 26 stores in advance an upper limit pressure Pmax and a lower limit pressure Pmin for maintaining the pressure in the tank 21 in an appropriate range. Then, as shown in FIG. 4, the control circuit 26 operates to stop and operate the compression unit 14 (electric motor 12) according to the pressure in the tank 21 (tank pressure Pt) detected by the pressure sensor 22 (pressure opening / closing). Control). Thereby, the control circuit 26 maintains the tank pressure Pt at a pressure value between the upper limit pressure Pmax and the lower limit pressure Pmin. That is, in the pressure open / close control, for example, the operation of the compression unit 14 is stopped when the tank pressure Pt reaches the upper limit pressure Pmax, and the compression unit 14 is restarted when the tank pressure Pt decreases to the lower limit pressure Pmin. It has become.

  Further, the control circuit 26 stores in advance a reference pressure range P0 that serves as a reference for the suction pressure Pin. At this time, the reference pressure range P0 is, for example, an allowable range for the pressure (rated pressure) of air constantly supplied to the suction port 19, that is, an allowable range for the steady pressure of the factory piping 3 (for example, P0 = 0). .4 to 0.5 MPa). When the suction pressure Pin as the detected pressure read from the suction pressure sensor 24 is within the reference pressure range P0, the control circuit 26 sets the drive current for driving the electric motor 12 to the reference current value I0 to The rotational speed of the motor 12 is maintained at a predetermined constant speed value (reference rotational speed N0). At this time, the electric motor 12 is rotationally driven, for example, at a lower limit frequency, and is operated at the slowest rotational speed (reference rotational speed N0 = 1000 rpm).

  On the other hand, when the suction pressure Pin falls below the reference pressure range P0, the control circuit 26 calculates a rotation speed N (Pin) corresponding to the suction pressure Pin using a rotation speed map 27 described later. Thus, the control circuit 26 is configured to continuously increase the rotational speed of the electric motor 12 from the reference rotational speed N0 in accordance with the suction pressure Pin.

  Reference numeral 27 denotes a rotation speed map stored in the control circuit 26. As shown in FIG. 5, the rotation speed map 27 stores the rotation speed N (Pin) corresponding to the suction pressure Pin. Here, the rotation speed N (Pin) is the rotation speed of the electric motor 12 according to the margin when the suction pressure Pin falls below the reference pressure range P0 and there is a margin in the power of the electric motor 12. Is set to increase the speed.

  Specifically, it is as follows. First, as shown by a dotted line in FIG. 8, when the electric motor 12 is rotationally driven at the reference rotational speed N0 and the air at the suction pressure Pin is compressed, the drive current of the electric motor 12 is set as the comparison current Ia. Next, as shown by the solid line in FIG. 8, the drive current of the electric motor 12 is increased from the comparison current Ia in the range of the reference current value I0 or less, and the air at the suction pressure Pin is compressed. The rotational speed N (Pin) is obtained by measuring the rotational speed of the electric motor 12 in this state, as shown by a solid line in FIG. For this reason, the rotational speed N (Pin) is actually rotated when the air at the suction pressure Pin is compressed in a state where, for example, a driving current equivalent to the reference current value I0 is supplied to the electric motor 12. It is set to the same value as the driven rotational speed. As a result, the rotational speed N (Pin) increases more than the reference rotational speed N0 when the suction pressure Pin falls below the reference pressure range P0 as a pressure causing a margin in the power of the electric motor 12. Then, the control circuit 26 calculates the rotational speed N (Pin) from the suction pressure Pin using the rotational speed map 27.

  Next, control processing of the air compressor 11 using the control circuit 26 will be described with reference to FIGS. 1 to 5. It is assumed that the control processing program shown in FIG. 4 and the reference pressure range P0, upper limit pressure Pmax, lower limit pressure Pmin, rotation speed map 27, and the like are stored in the control circuit 26 in advance.

  First, when the air compressor 11 is activated, the control circuit 26 first operates the electric motor 12 at the lower limit frequency using the inverter circuit 13 in step 1. Next, in step 2, using the detection signal output from the suction pressure sensor 24, the pressure of the air supplied to the suction port 19 is read as the suction pressure Pin (detection pressure).

  Next, in step 3, it is determined whether or not the suction pressure Pin is lower than the reference pressure range P0. If it is determined as “YES” in step 3, the suction pressure Pin may be lower than the reference pressure range P0, and the electric motor 12 may have a margin in power. For this reason, the process proceeds to step 4 to perform the rotational speed calculation process. At this time, the control circuit 26 refers to the rotation speed map 27 and calculates the rotation speed N (Pin) corresponding to the suction pressure Pin. In step 5, the control circuit 26 instructs the electric motor 12 to rotate at the rotation speed N (Pin) calculated from the rotation speed map 27. Specifically, the control circuit 26 uses the inverter circuit 13 to increase the drive current of the electric motor 12 in the range of the reference current value I0 or less. As a result, the rotational speed of the electric motor 12 is continuously increased according to the suction pressure Pin, and the control circuit 26 shifts to the processing after step 6.

  On the other hand, if “NO” is determined in step 3, the suction pressure Pin is considered to be within the normal reference pressure range P0. Therefore, the rotation speed of the electric motor 12 is set to the rated rotation speed (in accordance with the reference pressure range P0). The operation at the lower limit frequency) is continued and the process proceeds to Step 6.

  Next, in step 6, the detection signal output from the pressure sensor 22 is used to read the pressure in the tank 21 as the tank pressure Pt. In step 7, it is determined whether the tank pressure Pt is higher than the upper limit pressure Pmax. judge. When it is determined “NO” in step 7, the tank pressure Pt is lower than the upper limit pressure Pmax, and it is considered that the pressure in the tank 21 is being increased. For this reason, the process of steps 2-6 is repeated.

  On the other hand, when it is determined as “YES” in Step 7, the tank pressure Pt exceeds the upper limit pressure Pmax and is high. For this reason, it transfers to step 8 and the driving | operation of the electric motor 12 and the compression part 14 is stopped.

  Next, in step 9, as in step 6, using the detection signal output from the pressure sensor 22, the pressure in the tank 21 is read as the tank pressure Pt. In step 10, the tank pressure Pt is less than the lower limit pressure Pmin. It is determined whether it is low. When it is determined “NO” in step 10, the tank pressure Pt is higher than the lower limit pressure Pmin, and the pressure in the tank 21 is in the process of being lowered. For this reason, it waits in this state and repeats the processing of steps 9 and 10.

  On the other hand, when it is determined as “YES” in Step 10, the tank pressure Pt exceeds the lower limit pressure Pmin and is low. For this reason, it transfers to step 11, the electric motor 12 and the compression part 14 are restarted, and the process after step 1 is repeated.

  The booster type air compressor 11 according to the present embodiment has the configuration as described above. Next, the effect of shortening the filling time of the tank 21 by the air compressor 11 will be described with reference to FIGS. .

  First, before describing the present embodiment, a case in which the electric motor 12 is rotationally driven at a constant reference rotational speed N0 (constant speed value) of, for example, about 1000 rpm regardless of the suction pressure Pin will be considered as a comparative example.

  In this comparative example, as shown by the dotted line in FIG. 6, even when the pressure of the factory piping 3 fluctuates depending on the usage conditions of the pneumatic devices 4A to 4N and the suction pressure Pin falls below the reference pressure range P0, The electric motor 12 is driven to rotate at a constant reference rotational speed N0. At this time, as shown by a dotted line in FIG. 7, the amount of discharge air discharged toward the tank 21 decreases as the suction pressure Pin decreases, so the time until the tank 21 is filled with a predetermined amount of air. There is a problem that becomes longer.

  On the other hand, in the present embodiment, when the suction pressure Pin is lower than the reference pressure range P0, the rotational speed of the electric motor 12 is increased according to the suction pressure Pin. Specifically, as shown by a solid line in FIG. 8, the electric motor 12 is driven within the reference current value I0 when the electric motor 12 is rotationally driven at the reference rotation speed N0 to compress the air in the reference pressure range P0. The drive current of 12 is increased as compared with the comparative example.

  That is, in the case of the comparative example, as indicated by a dotted line in FIG. 8, there is a margin in the power of the electric motor 12 due to the reduction of the suction pressure Pin, and the drive current of the electric motor 12 is lower than the reference current value I0. . In the present embodiment, in order to effectively utilize the power margin generated in the electric motor 12 as described above, the drive current of the electric motor 12 is increased in a range of the reference current value I0 or less. As a result, as shown by the solid line in FIG. 6, the electric motor 12 rotates at a higher speed than the reference rotational speed N0, so the amount of discharge air discharged toward the tank 21 is as shown by the solid line in FIG. Increased compared to the comparative example. As a result, the filling time for filling the tank 21 with compressed air can be shortened.

  Thus, according to the present embodiment, the control circuit 26 increases the rotational speed of the electric motor 12 in accordance with the suction pressure Pin when the suction pressure Pin (detected pressure) is lower than the reference pressure range P0. Therefore, even when the air discharge amount decreases as the suction pressure Pin decreases, the air discharge amount can be increased by increasing the number of revolutions of the electric motor 12, and the air to the tank 21 can be increased. The filling time can be shortened.

  The control circuit 26 continuously increases the rotational speed of the electric motor 12 in accordance with the suction pressure Pin when the suction pressure Pin is lower than the reference pressure range P0. The rotational speed of the motor 12 can be slightly increased, and when the suction pressure Pin is greatly reduced, the rotational speed of the electric motor 12 can be greatly increased. For this reason, the rotation speed of the electric motor 12 can be increased according to the decrease in the suction pressure Pin, and the decrease in the air discharge amount from the compression unit 14 can be compensated.

  Further, when the suction pressure Pin is lower than the reference pressure range P0, the control circuit 26 sets the drive current of the electric motor 12 to a range equal to or less than the reference current value I0 as compared with the case where the electric motor 12 is driven at the reference rotational speed N0. It is set as the structure which increases by. For this reason, it is possible to increase the drive current of the electric motor 12 by an amount in which a margin is generated in the power of the electric motor 12 due to the decrease in the suction pressure Pin. Thereby, according to the fall of the suction pressure Pin, the rotation speed of the electric motor 12 can be increased more than the reference rotation speed N0, and the discharge amount of air can be increased. In addition, the power of the electric motor 12 can be used sufficiently effectively against fluctuations in the suction pressure Pin.

  In the embodiment, the control circuit 26 is configured to calculate the rotational speed N (Pin) from the suction pressure Pin using the rotational speed map 27 shown in FIG. However, the present invention is not limited to this. For example, the rotational speed N (Pin) may be calculated from the suction pressure Pin using a mathematical formula. In this case, for example, the rotational speed N (Pin) may be increased in proportion to a decrease in the suction pressure Pin.

  In the embodiment, the control circuit 26 is configured to continuously increase the rotational speed of the electric motor 12 in accordance with the suction pressure Pin when the suction pressure Pin is lower than the reference pressure range P0. However, the present invention is not limited to this, and as in the modification shown in FIG. 9, when the suction pressure Pin is lower than the reference pressure range P0, the control circuit steps the rotation speed of the electric motor according to the suction pressure Pin. It is good also as a structure which raises automatically.

  In the embodiment, specific numerical values are exemplified as the reference pressure range P0, the reference current value I0, the reference rotation speed N0, and the like. However, the present invention is not limited to the numerical values exemplified in the embodiment, and it is needless to say that individual numerical values can be set freely.

  In the embodiment, the case where the compression unit 14 is configured by a reciprocating compression mechanism has been described as an example. However, the compression unit is configured by a compression mechanism of another type such as a scroll type, for example. Also good.

  Furthermore, in the embodiment, the air compressor 11 has been described as an example of the compressor. However, the compressor may be applied to a compressor that compresses another gas such as nitrogen or a compressor that compresses a fluid such as a refrigerant. Good.

It is a whole block diagram which shows the state which connected the air compressor by embodiment of this invention to factory piping. It is an external view which shows the air compressor in FIG. It is a block diagram which shows the circuit structure of an air compressor. It is a flowchart which shows the control processing of an air compressor. It is explanatory drawing which shows a rotation speed map. It is a characteristic diagram which shows the relationship between a suction pressure and the rotation speed of an electric motor. It is a characteristic line figure which shows the relationship between suction pressure and the amount of discharge air of a compression part. It is a characteristic line figure which shows the relationship between a suction pressure and the drive current of an electric motor. It is a characteristic diagram which shows the relationship between the suction pressure by the modification, and the rotation speed of an electric motor.

Explanation of symbols

3 Factory piping 11 Air compressor 12 Electric motor (drive means)
13 Inverter circuit 14 Compressor 21 Tank 24 Suction pressure sensor (Suction pressure detection means)
26 Control circuit (control means)

Claims (3)

Drive means for rotationally driving, a compression section that is driven according to the number of rotations of the drive means and compresses the gas supplied from the suction port, a tank that stores compressed gas discharged from the compression section, and the drive means And a compressor having a control means for controlling the rotational speed of
A suction pressure detecting means for detecting the suction pressure of the gas supplied to the suction port of the compression unit is provided,
The control means is configured to increase the rotational speed of the drive means when the detected pressure by the suction pressure detecting means is lower than a predetermined reference pressure range as compared to when the detected pressure is within the reference pressure range. A compressor characterized by that.   2. The compressor according to claim 1, wherein when the detected pressure by the suction pressure detecting means is lower than a reference pressure range, the control means continuously increases the rotational speed of the driving means according to the detected pressure. .   2. The compressor according to claim 1, wherein when the detected pressure by the suction pressure detecting means is lower than a reference pressure range, the control means increases the rotational speed of the driving means stepwise according to the detected pressure. .

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