JP4584599B2 - Compressor - Google Patents

Description

  The present invention relates to a compressor suitably used for compressing a gas such as air using, for example, an electric motor as a power source.

  In general, the compressor is widely used as an air compressor for driving a pneumatic device such as a nailing machine. This type of conventional air compressor includes a motor, a compression unit that is driven by the motor and discharges compressed air, and a tank that stores the compressed air discharged from the compression unit (for example, , See Patent Document 1).

JP 2003-254254 A

  For example, when performing a nailing operation or the like at a construction site, the compressed air in the tank is stored in the tank while the compressed air is stored in the tank by connecting the nailing machine to the air compressor and operating the compressor. The nailing work is performed by supplying the nailing machine.

  Further, the conventional air compressor is provided with a pressure sensor for detecting the pressure in the tank, and motor control means for controlling the operating state of the motor using the detection result of the pressure sensor. Then, when the pressure in the tank rises by operating the motor, the motor control means temporarily stops the motor when the pressure reaches the upper limit value, and then the pressure in the tank by using a nail driver or the like. When the value becomes lower than the lower limit value, the motor is operated again.

  By the way, the above-described conventional air compressor may be used together with a nailing machine or the like, for example, in a construction site where a private house is close or at a night work site. There is a demand to reduce noise.

  However, for example, when the number of rotations of the motor is set low and noise is thereby suppressed, the supply amount of compressed air is likely to be limited. For this reason, when using a compressor, for example, if many nailing operations are performed continuously, the air pressure in the tank will be insufficient even when the motor is in operation, and the operation will be suspended until the air pressure rises sufficiently. In other words, there is a problem that work efficiency decreases.

  On the other hand, when it is set as the structure which makes the rotation speed of a motor high, a noise will increase when a motor is drive | operated and a work site and the surrounding environment will deteriorate. Thus, in the prior art, there is a problem that it is difficult to appropriately set the rotation speed of the motor.

  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 provide a compressor capable of appropriately controlling the number of rotations of a motor according to the situation and improving performance while suppressing noise. It is to provide.

  In order to solve the above-described problems, the present invention relates to a motor, a compression unit that is driven by the motor and discharges compressed gas, a tank that stores compressed gas discharged from the compression unit, and a pressure in the tank. Pressure detecting means to detect, and the motor is operated when the pressure detected by the pressure detecting means falls below a lower limit value, and the motor is stopped when the pressure rises and reaches an upper limit value It is applied to a compressor comprising motor control means.

The feature of the configuration adopted by the invention of claim 1 is that the motor control means uses the detection result of the pressure detection means to calculate a pressure change value at which the pressure in the tank changes at a constant time. and change computing means, varies depending on the pressure in the tank, a value determined by a linear function of the pressure in the tank, the value of the pressure change corresponding to the reference consumption of the compressed gas in the tank A judgment value computing means for computing a judgment value for a certain pressure change; a judgment means for judging a relationship between the judgment value computed by the judgment value computing means and the pressure change computed by the pressure change computing means; According to the present invention, there is provided a configuration including rotation speed switching means for switching the rotation speed of the motor between the low speed side and the high speed side according to the determination result of the means.

  According to the invention of claim 2, the judgment value calculating means is configured to calculate a judgment value for low speed operation when the motor is operated at low speed, and the rotation speed switching means is operated at low speed. In this state, only when the pressure change in the tank is smaller than the judgment value for low speed operation, the motor speed is switched from low speed to high speed.

  According to a third aspect of the present invention, the determination value calculating means is configured to calculate a determination value for high speed operation when the motor is operating at high speed, and the rotation speed switching means is configured to operate the motor at high speed. In this state, the motor speed is switched from high speed to low speed only when the pressure change in the tank becomes equal to or higher than the judgment value for high speed operation.

  According to a fourth aspect of the present invention, the determination value calculation means is configured to calculate a determination value for a stop state when the motor is stopped, and the motor control means includes a tank in which the motor is stopped. An operation return means is provided for returning the motor from the stopped state to the operating state when the pressure change of the motor becomes equal to or greater than the determination value for the stopped state.

  According to a fifth aspect of the present invention, the determination value calculation means is configured to calculate the determination value using the number of rotations of the motor and the pressure in the tank.

  Furthermore, according to the invention of claim 6, the motor control means stores the pressure in the tank detected by the pressure detection means as detection data for every predetermined detection time, and the pressure change calculation means includes the detection data among the detection data. A difference between two pieces of detection data stored at a time interval more than twice the detection time is calculated as a pressure change, and the calculated value of the pressure change is updated every detection time.

According to the first aspect of the present invention, the pressure change calculation means can calculate the magnitude of the pressure change that occurs in a certain time in the tank by using a detection signal of a pressure sensor, for example. In this case, for example, if it is determined by pressure change whether or not the compressed gas is consumed with a constant reference consumption in a state where the rotation speed of the motor is constant, the magnitude of the pressure change corresponding to this reference consumption is large. The value varies depending on the pressure in the tank. Thus, for example, the magnitude of the pressure change corresponding to the reference consumption depends on the pressure in the tank, be previously stored as characteristic data of the determination values Ru value der determined by a linear function of the pressure in the tank Thus, the determination value calculation means can always calculate the determination value corresponding to the preset reference consumption amount accurately using this characteristic data and the detected pressure value, and the determination value can be determined even if the pressure changes. It is possible to stably compensate for the influence of the value.

  Then, the determination means can easily determine whether or not the consumption amount of the compressed gas actually consumed from the tank is larger than the reference consumption amount by comparing the magnitude of the pressure change with the determination value. . Further, the rotation speed switching means can efficiently operate the compressor by switching the rotation speed of the motor to the low speed side when, for example, the compressed gas consumption is small, and the motor rotation speed when the compressed gas consumption is large. Can be switched to the high speed side to sufficiently supply the compressed gas into the tank. As a result, when operating pneumatic devices such as nailing machines with a compressor, the motor is switched to the high speed side only when it is continuously used, and the pneumatic devices are operated smoothly. When the device is used intermittently, the motor can be switched to the low speed side to suppress noise, vibration, and the like.

  Therefore, it is possible to appropriately control the rotation speed of the motor according to the amount of compressed gas consumption while suppressing the operation noise of the motor, thereby stably maintaining the pressure in the tank and reducing noise and high operating efficiency. An energy type compressor can be realized. Further, the flow rate at which the compressed gas is consumed can be detected by a change in pressure, and it is not necessary to use a flow meter or the like. Therefore, the compressor can be made more compact accordingly, and the cost can be reduced.

  According to the second aspect of the present invention, even when the motor is operating at low speed, if the pressure change when the pressure in the tank rises is equal to or higher than the determination value for low speed operation, the amount of compressed gas consumed Therefore, it is possible to efficiently maintain the pressure in the tank while maintaining the rotation speed at a low speed. When the pressure change is smaller than the determination value for low speed operation, it can be determined that the amount of compressed gas consumed is large, so the motor rotation speed is switched to a high speed, and the flow rate of the compressed gas discharged from the compression unit into the tank Can be increased appropriately according to the air consumption.

  According to the invention of claim 3, even when the motor is operating at high speed, if the pressure change when the pressure in the tank rises is smaller than the judgment value for high speed operation, the consumption of compressed gas Since it can be determined that there is a large amount, the rotation speed can be maintained at a high speed, and a large amount of compressed gas can be continuously discharged from the compression section into the tank. Further, when the pressure change is equal to or higher than the determination value for high-speed operation, it can be determined that the amount of compressed gas consumed is small. Therefore, the number of rotations of the motor can be switched to low speed to prevent excessive high-speed operation.

  According to the invention of claim 4, when the pressure in the tank becomes equal to or higher than the upper limit value and the motor is stopped, the pressure change (pressure drop) in the tank becomes equal to or higher than the determination value for the stopped state. It can be determined that a large amount of compressed gas is consumed. In this case, before the pressure in the tank drops to the lower limit value, the motor can be returned from the stopped state to the operating state by the operation return means, and the pressure is reduced to the lower limit by consuming the compressed gas in the tank. It can be prevented that the value drops below the value.

  According to the invention of claim 5, for example, when a compressed gas having a flow rate corresponding to the rotational speed of the motor (including the stopped state) flows into the tank, the pressure change corresponding to a certain reference consumption is changed. The magnitude can be stored in advance as characteristic data of a determination value that changes in accordance with the number of rotations of the motor and the pressure in the tank. As a result, the determination value calculation means can always accurately calculate the determination value of the pressure change corresponding to the reference consumption by using the characteristic data, the rotation speed of the motor, and the detected pressure value.

  Furthermore, according to the invention of claim 6, the motor control means can store pressure detection data for every detection time, for example, and can calculate a pressure change every time data is stored. Thereby, the calculated value of the pressure change can be updated every detection time, and the responsiveness of the calculated value of the pressure change can be improved when the actual pressure in the tank changes.

  In this case, the time interval that becomes the pressure change measurement interval can be set as a time that is at least twice as long as the detection time. Therefore, when calculating the pressure change, for example, compared with individual detection data errors due to signal noise, etc. The calculated value of the pressure change can be a large value, and the S / N ratio of the calculated value can be sufficiently secured. As a result, the pressure change can be accurately calculated according to the pressure change actually generated in the tank.

  Hereinafter, an air compressor that supplies compressed air to a pneumatic device such as a nailing machine 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.

  Reference numeral 1 denotes, for example, an air compressor configured as a portable compressor. As shown in FIGS. 1 and 2, the air compressor 1 includes a motor 2, a compression unit 3, a tank 4, a pressure sensor 5, and a motor, which will be described later. The control circuit 6 is generally configured to supply compressed air to a pneumatic device 8 such as a nailing machine.

An electric motor 2 serves as a power source for the air compressor 1. The motor 2 is disposed, for example, on the upper side of the tank 4, and is compressed by being supplied with power from an external power source via the motor control circuit 6 or the like. The unit 3 is driven. In this case, the rotational speed N of the motor 2 is controlled by the motor control circuit 6 as described later, and is switched between a low rotational speed _{NL of} about 1600 rpm and a high rotational speed _{NH of} about 2500 rpm, for example.

  Reference numeral 3 denotes a compression unit provided on the upper side of the tank 4 together with the motor 2, and the compression unit 3 includes, for example, a reciprocating compressor, a scroll compressor, and the like, and is driven by the motor 2. The compression unit 3 sucks air from outside and discharges the compressed air into the tank 4, and the discharge amount increases as the rotation speed N of the motor 2 increases.

  Reference numeral 4 denotes a tank constituting the lower side of the air compressor 1. The tank 4 stores the compressed air discharged from the compression unit 3, and supplies the compressed air to the pneumatic equipment 8 and the like. In this embodiment, for example, the tank capacity V is about 9 liters.

  Reference numeral 5 denotes a pressure sensor as a pressure detection means provided in the tank 4, and the pressure sensor 5 is configured using, for example, a general-purpose commercially available sensor component. As shown in FIG. 2, the pressure sensor 5 detects the pressure in the tank 4 and outputs the detected signal as a pressure P to the motor control circuit 6.

  Reference numeral 6 denotes a motor control circuit as a motor control means for controlling the operating state of the motor 2. The motor control circuit 6 is composed of, for example, an electronic circuit including a drive circuit for a motor, and includes a storage circuit 7 to be described later. Yes. The motor control circuit 6 is connected to the pressure sensor 5 and the like on its input side, and the motor 2 is connected to its output side.

  The motor control circuit 6 performs motor control shown in FIG. 7 to be described later using the detection signal input from the pressure sensor 5, and the pressure P in the tank 4 is set to an upper limit value Pmax (for example, about 3.0 MPa) described later. ), The motor 2 is stopped. When the pressure P becomes lower than the lower limit value Pmin (for example, about 2.6 MPa), the motor 2 is operated again. The motor control circuit 6 controls the rotational speed N of the motor 2 in accordance with the consumption (flow rate) of compressed air consumed by the pneumatic device 8, as shown in FIGS. is there.

  In this case, the motor control circuit 6 first reads the pressure P in the tank 4 detected by the pressure sensor 5 at every detection time t of about 0.5 seconds, for example, and stores it in the storage circuit 7 to be described later. For example, a value at which the pressure in the tank 4 changes (increases or decreases) during a time interval T of about 3 seconds is calculated as a pressure change ΔP.

The motor control circuit 6, and the rotational speed N motor 2 as described later, the determination value by using the pressure P of the tank 4 (the determination value S _L for low speed _operation, the determination value S _H and for high-speed operation calculating any) of the decision value S _W for the stopped state. Then, by comparing and determining the magnitude relationship between the calculated determination value and the pressure change ΔP, the rotation speed N of the motor 2 is reduced to a low speed operation (low rotation speed N _L ) and a high speed operation (high speed) according to the determination result. Switching between the rotation speed N _H ).

Here, the determination value S _L, and S _H, S _W, as shown in the numerical formula 1 or several 3 described below, the consumption of compressed air as a criterion for determining whether switching the operating state of the motor 2 ( It is a value obtained by converting a later-described reference consumption amount K _L , K _H , K _W ) into a pressure change. Therefore, the process of comparing the pressure change ΔP with the determination values S _L , S _H , and S _W is whether or not the compressed air in the tank 4 is consumed more than the reference consumption amounts K _L , K _H , and K _W. This corresponds to the process of determining.

For example, the motor control circuit 6 operates in a state where the motor 2 is operated at low speed, and the pressure change ΔP in the upward direction in the tank 4 (pressure increase ΔP that increases as the pressure increases in a short time) is used for low speed operation. When it is determined that the value is equal to or greater than the determination value S _L , the motor 2 is held at the low rotation speed N _{L as shown} in FIG. That is, in this case, as shown in section a2 in FIG. 8 to be described later, the reference consumption K _L during low speed operation to be described later _(e.g., 20 liters / min approximately) a minor consumption of compressed air than The pressure in the tank 4 increases at an appropriate rate even when the motor 2 is operated at a low speed, so that the compressor can be operated efficiently at a low speed.

Further, when the pressure variation ΔP in the tank 4 is smaller than the determination value S _L, for example as shown in section a3 in FIG. 8, the consumption of compressed air increases than the reference consumption K _L, low speed operation Then, it is determined that the pressure in the tank 4 does not rise quickly, and the motor 2 is switched to the high rotation speed _NH as shown in FIG.

On the other hand, the motor 2 in a state of high speed operation, when the pressure change ΔP rising direction of the tank 4 is less than the determination value S _H of the high-speed operation, as shown in section a4 in FIG. 8, for high-speed operation to be described later Since the consumption amount of compressed air is larger than the reference consumption amount K _H (for example, about 10 liters / minute), it is determined that the rate of increase in pressure is moderate, and the motor 2 is held at a high rotational speed _NH . . Further, when the pressure change ΔP becomes the determination value S _H above, as shown in section a5, since compressed air consumption becomes smaller than the reference consumption K _H, it can maintain a sufficient pressure in the low-speed operation And the motor 2 is switched to the low rotation speed N _L.

Furthermore, when the motor 2 is stopped, the motor control circuit 6 reduces the pressure change ΔP in the decreasing direction (pressure decrease ΔP that increases as the pressure decreases in a short time) as the pressure in the tank 4 decreases. when but becomes equal to or larger than the reference value S _W for stop state, as shown in FIG. 9, it is determined that a large amount of compressed air as a reference consumption K _W or more for a stopped state is consumed, stops the motor 2 In addition to returning from the state, this is operated at a high rotational speed _NH . In this case, when the pressure variation ΔP in the decrease direction is smaller than the determination value S _W, as shown in FIG. 10, until the pressure P of the tank 4 is less than the lower limit value Pmin, the motor 2 is held in a stopped state.

Further, as shown in FIG. 6, the motor control circuit 6 reads the detection signal of the pressure sensor 5 every detection time t of, for example, about 0.5 seconds, and stores this in the storage circuit 7 as detection data D. At this time, for example, every time a new detection signal is read, the difference (for example, D _n−1 −D _n−7 , D _n −) between the latest detection data D and the detection data D stored previously by the time interval T. D _n-6 , D _{n + 1} -D _n-5 etc.) is calculated as the pressure change ΔP. Thereby, the motor control circuit 6 can update the calculated value of the pressure change ΔP every detection time t, and when the actual pressure in the tank 4 changes, the responsiveness of the calculated value of the pressure change ΔP can be improved. it can.

  In this case, the time interval T that is the measurement interval of the pressure change ΔP is set as a long time that is at least twice the detection time t (illustrated as six times in the present embodiment). As a result, the motor control circuit 6 can make the calculated value of the pressure change ΔP larger than the error of the individual detection data D due to, for example, signal noise, and the S / N ratio of the calculated value is sufficient. Can be secured. As a result, the pressure change ΔP can be accurately calculated in accordance with the pressure change actually generated in the tank 4.

  Reference numeral 7 denotes a storage circuit such as a ROM or a RAM provided in the motor control circuit 6. The storage circuit 7 includes a motor control program, an upper limit value Pmax, a lower limit value Pmin, and a return set value Pon used in this control. , Initial setting value Pstart and the like are stored in advance.

  In this case, the upper limit value Pmax that determines the upper limit of the pressure in the tank 4 is set to, for example, a pressure of about 3 MPa, and the lower limit value Pmin that sets the upper limit of the pressure is set to, for example, about 2.6 MPa. Further, the return set value Pon is an upper limit value when the motor 2 is returned from the stopped state, and is set to about 2.9 MPa, for example. Furthermore, the initial set value Pstart is a determination criterion for determining whether or not the pressure in the tank 4 is sufficiently large when the power is turned on, and is set to about 2.4 MPa, for example.

Further, the memory circuit 7, a low-speed operation, high-speed operation, the determination value S _L for the stopped _state, S _H, S _W are stored in advance. Referring to these determination values, first, the determination value S _L for low speed operation is the value in the tank 4 when the motor 2 is operated at a low rotation speed N _{L as} shown by the characteristic line 9 in FIG. It is set according to the pressure P, and determines whether or not the motor 2 is switched to the high rotational speed _NH . This determination value S _L is derived by the following equation (8), and is determined as the following equation (1), for example.

The right side of this equation while flowing compressed air at a predetermined flow rate into the tank 4 by low-speed operation of the motor 2, when the compressed air is consumed with a constant reference consumption K _L, the tank 4 This corresponds to the magnitude of the pressure change ΔP. As can be seen from this equation, for example, when the rotational speed N of the motor 2 is constant, the magnitude of the pressure change ΔP corresponding to the reference consumption K _L is a different value depending on the pressure in the tank 4.

Then, for example, when the compressed air consumption is increased than the reference consumption K _L, since the flow rate of air flowing into the tank 4 increases an amount corresponding substantially to a decrease in consumption, the pressure change ΔP in the tank 4 is , Smaller than the right side of Equation 1, that is, the judgment value S _L. Further, when the compressed air consumption is reduced than the reference consumption K _L, since the flow rate of air flowing into the tank 4 is substantially increased state, the pressure change ΔP is greater than the determination value S _L .

In this way, by comparing the determination value S _L of the equation 1 and the pressure change ΔP, it can be determined whether or not the consumption of compressed air during low-speed operation is greater than the reference consumption K _L. when air consumption is larger than a reference consumption K _L can switch the motor 2 from the low-speed operation to the high speed operation. Reference consumption K _L at the time of low-speed operation is set to the motor 2 flow rate such that insufficient air pressure of the high-speed operation and not the tank 4, for example, as a relatively large flow rate of about 20 liters / min.

On the other hand, the determination value S _H of the high-speed operation, as shown by the characteristic line 10 in FIG. 3, when the motor 2 is operated at high rotational speed N _H, is set according to the pressure P of the tank 4 It is determined whether or not the motor 2 is switched to the low rotation speed N _L. Then, the determination value _SH is derived from an expression 10 described later, and is defined as the following expression 2, for example.

The right side of this equation, much like the case of the decision value S _L for low-speed operation, the motor 2 and high-speed operation, when the compressed air in the tank 4 is consumed with a constant reference consumption K _H, This represents the magnitude of the pressure change ΔP. Thus, by comparing the decision value S _H and the pressure change ΔP of the foregoing equation 2, that the consumption of compressed air during high-speed operation to determine whether more than a reference consumption K _H it can.

When the pressure change ΔP in the tank 4 reaches a determination value S _H above, namely when the air consumption is equal to or less than the reference consumption K _H can be switched to low-speed operation of the motor 2 from the high-speed operation. Reference consumption K _H at the time of high speed operation, the flow rate value such as the motor 2 can be maintained air pressure in the tank 4 without high-speed operation, for example, it is set as a relatively small flow rate of approximately 10 l / min Yes.

Further, the determination value S _W for stop state, as shown by the characteristic line 11 in FIG. 5, when the motor 2 is stopped, is set according to the pressure P in the tank 4, the stopped state of the motor 2 To determine whether or not to operate at a high rotational speed _NH . This determination value _SW is derived by the following equation (11), and is determined, for example, by the following equation (3).

Next, referring to FIG. 4, the determination value _{S L,} S H, the number 1 to number 3 methods deriving sets the _{S W} will be described.

First, the described determination value S _L for low-speed operation, for example, the motor 2 is held in the low-speed operation, consider the case outflow quantity of the compressed air flowing out of the tank 4 (consumption) is zero. In this case, the air flow rate Q (liters / minute) discharged from the compression unit 3 into the tank 4 decreases as the pressure P (MPa) in the tank 4 increases. As shown by the characteristic line 12, it can be approximately expressed as a linear function. This characteristic line 12 is unique depending on the specification of the compressor 1 and the like, and when this is expressed as a mathematical expression, the following expression 4 is obtained.

Considering a state in which the compressed air in the tank 4 flows out to the outside with a constant outflow amount under this operating condition, this state is a state in which the air flow rate Q of the equation 4 is reduced by the outflow amount (that is, The characteristic line 12 can be treated equivalently to a state in which the characteristic line 12 is translated by the amount of the outflow. Thus, for example, the characteristic line when the outflow of the compressed air becomes 20 l / min about the reference consumption K _L is as shown by a characteristic line 13 shown in phantom in FIG. 4, the following equation 5 It can be expressed as:

On the other hand, between the change ΔP ′ (kg · f / m ² / min) in the pressure in the tank 4, the air flow rate Q (liter / min), and the capacity V (liter) of the tank 4, ΔP ′ = Since there is a relationship of Q / V, the formula 5 can be rewritten as the following formula 6.

Further, there is a unit between the pressure change ΔP (MPa / second) during the time interval T (second) calculated by the motor control circuit 6 and the pressure change ΔP ′ (kg · f / m ² / min). Due to the difference in the system, there is a relationship shown in the following formula 7.

  Therefore, by substituting the equation (6) into the equation (7), the following equation (8) can be obtained.

The equation for this number 8, the motor 2 is held in the low-speed operation, and represents the magnitude of the pressure change ΔP when the compressed air is consumed in the reference consumption K _L. Therefore, replacing the pressure variation ΔP in the equation to the determination value S _L, for example, the time interval T = 3 (seconds), by substituting tank volume V = 9 (l), the determination values corresponding to the reference consumption K _L S _L can be obtained as the above equation (1).

Thus, the determination value S _L is the quantity of air discharged from the compression unit 3 and are derived using a characteristic line 12 represents the relationship between the pressure P, as discharged air volume as the pressure P increases is reduced The effect is also compensated. Thus, during low-speed operation of the compressor, without being affected by the magnitude of the pressure P, always stably determined by the decision value S _L whether compressed air consumption is greater than the reference consumption K _L be able to.

Next, described a method of deriving a decision value S _H of the high-speed operation, when the motor 2 is a consumption of compressed air at high speed operating conditions is zero, the relationship between the air flow Q and pressure P, for example FIG. 4 is represented by the following equation (9).

In this operating condition, for example, the characteristic line when the consumption of compressed air was 10 liters / min about the reference consumption K _H is substantially similar to the case of low speed operation, characteristics indicated by the phantom line in FIG. 4 It becomes like a line 15 and can be expressed as the following equation (10).

The equation (2) can be obtained by modifying the equation (10) in the same procedure as the equations (6) to (8). Furthermore, for the decision value S _W for the stopped state, by deforming the characteristic line corresponding to the reference consumption K _W of appropriate size (e.g., the following equation number 11), deriving the equation (3) can do.

  The air compressor 1 according to the present embodiment has the above-described configuration. Next, motor control will be described with reference to FIG.

  First, when the power of the compressor is turned on, in step 1, the pressure P in the tank 4 detected by the pressure sensor 5 is read at every detection time t and stored in the storage circuit 7. In this case, the pressure P reading / storing process described in steps 1, 5, 11, 17, 20, and 25 in FIG. 7 is, for example, an interrupt process that is repeatedly executed at every detection time t during the motor control. This is illustrated in several places.

Next, in step 2, for example, it is determined whether or not the pressure P is equal to or higher than an initial set value Pstart of about 2.4 MPa. When it is determined as “ NO ”, for example, as shown in a section a1 in FIG. Since the amount of air in the tank 4 in the initial state after charging is small, in step 3, the motor 2 is operated at a high rotational speed NH, and the pressure P is quickly increased to a magnitude equal to or greater than the initial set value Pstart. When it is determined as “ YES ” in step 2, since a sufficient amount of compressed air has been stored in the tank 4, the process proceeds to step 4 and the motor 2 is operated at a low speed.

During this low speed operation, first, the rotational speed of the motor 2 is switched to the low rotational speed _NL in step 4 and the pressure P is read in step 5 while increasing the pressure in the tank 4 with a certain amount of discharge air. Then, the pressure change (pressure increase) ΔP during the time interval T is calculated with the increasing direction of the pressure P being positive. Then, in step 7 calculates the decision value S _L for low-speed operation by using the read value of the pressure P, and the stored characteristic data in the memory circuit 7 (characteristic line 9 in FIG. 3).

Next, in step 8, the pressure change ΔP of the upward pressure and positive, it is determined whether or not the determination value S _L or more, when it is determined as "YES", as shown in section a2 in FIG. 8 Since there is no consumption of compressed air, the pressure P in the tank 4 increases at an appropriate rate. Therefore, in step 9, it is determined whether or not the pressure P is equal to or higher than the upper limit value Pmax. If it is determined “YES”, the process proceeds to a stop state in step 16 described later. If “NO” is determined in the step 9, the process returns to the step 4 and the low speed operation is continued until the pressure P reaches the upper limit value Pmax.

On the other hand, when “NO” is determined in Step 8, for example, as shown in a section a3 in FIG. 8, the pneumatic equipment 8 such as a nailing machine is continuously used, so that the standard consumption for low speed operation is achieved. the amount K _L a large amount of compressed air is consumed than, the increase ratio of the pressure P becomes gentle, perform high-speed operation of the motor 2 proceeds to step 10. Thereby, as shown to the section a4, the pressure in the tank 4 can be raised smoothly.

During this high-speed operation, first, the rotational speed of the motor 2 is switched to a high rotational speed _NH in step 10, and the pressure P is read in step 11 while increasing the pressure in the tank 4 with the maximum discharge air amount. 12, the pressure change (pressure increase) ΔP during the time interval T is calculated with the increasing direction of the pressure P being positive. Then, in step 13, it calculates a decision value S _H of the high-speed operation by using the read value of the pressure P, and the characteristic data of the memory circuit 7 (characteristic line 10).

Next, in step 14, it is determined whether the pressure change ΔP determination value S _H above. When it is determined as “YES” in step 14, for example, as shown in a section a 5 in FIG. 8, for example, the use of the pneumatic device 8 becomes intermittent, so that the air consumption becomes the reference consumption for high speed operation. It becomes _KH or less, and the rate of increase in pressure P is larger than necessary. Therefore, in this case, as shown in the section a6, the process returns to step 4 to shift to the low speed operation, and when the pressure P becomes the upper limit value Pmax or more in the low speed operation, as shown in the section a7, in the later-described step 16 Transition to the stopped state.

  On the other hand, when it is determined as “NO” in step 14, the discharge air amount of the compression unit 3 is appropriately set, and the pressure P increases at an appropriate rate. Therefore, in step 15, it is determined whether or not the pressure P is equal to or higher than the upper limit value Pmax. If it is determined “YES”, the process proceeds to a stop state in step 16. Further, when it is determined as “NO” in Step 15, the high speed operation is continued until the pressure P reaches the upper limit value Pmax.

  Next, in step 16, since the pressure P in the tank 4 becomes equal to or higher than the upper limit value Pmax, the operation of the motor 2 is stopped. During this stop state, the pressure P is read in step 17, and in step 18, for example, it is determined whether or not the pressure P is equal to or lower than the set value Pon for restoration of about 2.9 MPa, and “NO” is determined. In this case, for example, as shown in a section b1 in FIG. 9, since the pressure P is maintained at a sufficient level, the stopped state is maintained while repeating steps 17 and 18.

If it is determined as “YES” in step 18, the pressure P is read in step 19. In step 20, the pressure change (pressure drop) ΔP during the time interval T is calculated with the pressure P decreasing direction as positive. Then, in step 21, it calculates a decision value S _W for stop state by using the read value of the pressure P, and the characteristic data of the memory circuit 7 (characteristic line 11).

Next, in step 22, it is determined whether the pressure change ΔP determination value S _W or more. When it is determined as “YES” in step 22, for example, as shown in a section b 2 in FIG. 9, the air consumption 8 is continuously used, so that the air consumption is the reference consumption K for the stop state. becomes larger than _W, the pressure P in the tank 4 is reduced by a large proportion. Therefore, in step 23, as shown in the section b3, the motor 2 is returned from the stopped state and is operated at a high speed.

  During this high speed operation, the pressure P is read in step 24, and it is determined in step 25 whether or not the pressure P has reached the upper limit value Pmax. If it is determined “YES”, the process returns to the stop state in step 16. When it is determined “NO” in step 25, the high-speed operation is continued while repeating steps 24 and 25.

  As described above, when the pneumatic device 8 consumes a large amount of compressed air after the compressor is temporarily stopped, for example, as shown in the section b4 in FIG. 9, the high-speed operation and the stopped state are alternately performed. The pressure in the tank 4 can be stably maintained between the upper limit value Pmax and the return set value Pon.

  On the other hand, when “NO” is determined in step 22, the amount of compressed air consumed by the pneumatic device 8 is small. For example, as shown in the sections c 1 and c 2 in FIG. 10, the pressure P gradually decreases from the stop state. Yes. Therefore, in step 26, for example, it is determined whether or not the pressure P has become lower than the lower limit Pmin of about 2.6 MPa.

  When it is determined as “YES” in step 26, the pressure in the tank 4 has reached the state where replenishment is required. Therefore, as shown in the section c3 in FIG. Return to and perform low-speed operation. Further, when “NO” is determined in Step 26, Steps 19 to 22 and 26 are repeatedly executed, and the stopped state is maintained until the pressure P becomes the lower limit value Pmin or less.

  Thus, when the air consumption of the pneumatic device 8 is relatively small after the compressor is temporarily stopped, the motor 2 is not operated at a high speed as shown in the sections c2 to c4 in FIG. The low-speed operation and the stop state can be alternately repeated, and the pressure in the tank 4 can be efficiently maintained between the upper limit value Pmax and the lower limit value Pmin.

Thus, according to the present embodiment, the pressure change ΔP during the time interval T is calculated using the pressure P in the tank 4 detected by the pressure sensor 5, and the rotational speed N of the motor 2 and the pressure in the tank 4 are calculated. together, it is determined that the pressure change ΔP determination value _{S L,} S H, the magnitude relation between _{S W,} depending on the determination result motor calculates a decision value _{S L, S H, S W} in accordance with the pressure P 2 is switched between the low speed side and the high speed side.

In this case, the storage circuit 7 indicates the magnitude of the pressure change corresponding to, for example, certain reference consumptions K _L , K _H , K _{W according} to the rotational speed N of the motor 2 and the pressure P in the tank 4. It can be stored in advance as data of the changing characteristic lines 9, 10, and 11. Therefore, during the operation of the compressor 1, reference consumptions K _L and K _H set in advance according to these characteristic lines 9, 10 and 11, the rotational speed N of the motor 2, and the pressure P in the tank 4. , K _W corresponding to the judgment values S _L , S _H , S _W can always be accurately calculated, and even if the pressure P changes, the influence of the judgment values S _L , S _H , S _W is stably compensated. be able to.

The magnitude of the pressure change ΔP and determination value _{S L, S H, S W} and by comparing the reference consumption consumption of compressed air that is actually consumed from the tank _{4 K L, K H, K} W It is possible to easily determine whether or not there are more. Thus, for example, when the consumption amount of compressed air is small, the rotation speed of the motor 2 can be switched to the low rotation number N _L and the compressor can be operated efficiently. When the consumption amount of compressed air is large, the rotation speed of the motor 2 is reduced. The compressed air can be sufficiently supplied into the tank 4 by switching to the high rotation speed _NH .

  For this reason, for example, when the pneumatic device 8 such as a nailing machine is operated by a compressor, the pneumatic device 8 is smoothly operated by switching the motor 2 to the high speed side only when the pneumatic device 8 is continuously used. Can do. Further, when the pneumatic device 8 is used intermittently, the motor 2 can be switched to the low speed side to suppress noise, vibration, and the like.

  Accordingly, the rotational speed N of the motor 2 can be appropriately controlled in accordance with the consumption amount of compressed air while suppressing the operation noise of the motor 2, thereby stably maintaining the pressure in the tank 4 and operating with low noise. An energy-saving compressor 1 with high efficiency can be realized. Further, since the flow rate at which the compressed air is consumed can be detected by the pressure change ΔP, and there is no need to use a flow meter or the like, the compressor can be made more compact accordingly, and the cost can be reduced.

In this case, holding a low rotational speed N _L when the pressure variation ΔP in the tank 4 in a state of switching the rotational speed N of the motor 2 to the low rotation speed N _L is the determination value S _L or more for low-speed operation, since the pressure change ΔP was switched to a high rotational speed N _H when it becomes smaller than the determination value S _L, when compressed air consumption is the reference consumption K _L or more, holding the low rotational speed N _L However, the pressure in the tank 4 can be maintained efficiently. Further, when the compressed air consumption is greater than the reference consumption K _L is the number of revolutions of the motor 2 can be switched to a high rotational speed N _H, the flow rate from the compression unit 3 of the compressed air discharged into the tank 4 Can be increased appropriately according to the air consumption.

Also, maintaining high rotational speed N _H when the pressure change ΔP rotational speed in a state of switching to the high rotational speed N _H of the motor 2 is smaller than the determination value S _H for high-speed operation, the pressure change ΔP is determined value since to switch to a low rotational speed N _L when it becomes equal to or greater than S _H, when the consumption of the compressed air is greater than the reference consumption K _H from the compression unit 3 by retaining the high rotational speed N _H A large amount of compressed air can continue to be discharged into the tank 4. Further, when the compressed air consumption is less than the reference consumption K _H is switched to the low rotational speed N _L can prevent excessive high speed operation, it is possible to save power consumption of the motor 2.

Further, during the stop state motor 2, when the pressure in the tank 4 is caused a pressure change ΔP in the above decision value S _W decreases, thereby returning the motor 2 from the stop state at a high rotational speed N _H Since the motor 2 is operated, when a large amount of compressed gas is consumed while the motor 2 is stopped, the motor 2 can be quickly returned from the stopped state and operated at a high speed, and the pressure in the tank 4 is lower than the lower limit. A large amount of compressed air can be fed into the tank 4 before it drops to the value Pmin. Thereby, it is possible to reliably prevent the air pressure from being insufficient due to the rapid consumption of the compressed air in the tank 4.

  In the above-described embodiment, steps 6, 12, and 20 in FIG. 7 show a specific example of the pressure change calculation means, and steps 7, 13, and 21 show a specific example of the determination value calculation means. Steps 8, 14, and 22 are specific examples of the determination means, steps 4 and 10 are specific examples of the rotation speed switching means, and step 23 is a specific example of the operation return means.

Further, in the embodiment, the determination values S _L , S _H , and S _W are calculated according to the pressure P in the tank 4 by using the equations 1 to 3 as the determination value calculation means. did. However, the present invention is not limited to this. For example, the relationship between the pressure and the judgment value corresponding to the formulas (1) to (3) is used as map data for each operation state including low speed operation, high speed operation, and stop state. The determination value calculating means may be configured by storing each of them in the storage circuit 7 and using these map data. Thus, when the compressor is in operation, the determination value can be calculated by referring to any one of the map data according to the rotation speed N of the motor 2 and the pressure P in the tank 4.

In the embodiment, the pressure change ΔP and the determination value S _L as the determination _unit, S _H, by determining the magnitude of S _W, setting the rotational speed N of the motor 2 in any one of slow and fast construction It was. However, the present invention is not limited to this, for example, pressure change ΔP and the determination value S _L, S _H, map sets the rotational speed N of the motor 2 for each individual combination according to the combination of values of S _W data May be stored in advance in the storage circuit 7, and the determination means may be configured by this map data.

Furthermore, to set the determination value _S L and the pressure P as described _above, S H, and the map data showing the relationship between _{S W,} the pressure change ΔP and the determination value _{S L,} S H, the rotational speed N in accordance with the _{S W} By combining and integrating the map data, map data for setting the rotational speed N of the motor 2 for each combination is formed according to the combination of the values of the pressure P and the pressure change ΔP. The determination value calculation means and the determination means may be configured as described above. In this case, the pressure P functions as a substantial determination value.

On the other hand, in the embodiment, the low rotation speed N _L , the high rotation speed N _H , the reference consumption K _L , K _H , the tank capacity V, the detection time t, the time interval T, the upper limit value Pmax, the lower limit value Pmin, the return As the setting value Pon, the initial setting value Pstart, etc., various specific numerical values have been described as examples. However, these numerical values are merely examples used in the embodiment, and the present invention is not limited to these numerical values.

  In the embodiment, the pressure sensor 5 directly detects the pressure in the tank 4. However, the pressure detection portion of the present invention is not limited to the inside of the tank 4, and it is sufficient to detect the pressure at an arbitrary portion where a pressure substantially the same as that in the tank 4 is generated. For example, a pipe connected to the tank 4 It is good also as a structure which detects pressures, such as.

  Furthermore, in the embodiment, the air compressor 1 has been described as an example. However, the present invention is not limited to this, and can be applied to various compressors that compress gas other than air.

It is an external view which shows the air compressor by embodiment of this invention. It is a block diagram which shows the circuit structure of an air compressor. It is a characteristic diagram which shows the relationship between each judgment value for low speed driving | operations and high speed driving | operations, and the pressure in a tank. It is a characteristic diagram which shows the relationship between the flow volume of the compressed air which comes in and out of a tank, and the pressure in a tank. It is a characteristic diagram which shows the relationship between the determination value for stop states, and the pressure in a tank. It is explanatory drawing which shows the relationship between the reading timing of the detection signal of a pressure sensor, and the calculation timing of a pressure change. It is a flowchart which shows motor control. It is a characteristic diagram which shows the state which a compressor performs a low speed operation and a high speed operation from an initial state. It is a characteristic diagram which shows the state which a compressor returns to a high speed driving | operation from a stop state. It is a characteristic diagram which shows the state which a compressor transfers to a low speed driving | operation from a stop state.

Explanation of symbols

1 Air compressor (compressor)
2 Motor 3 Compression section 4 Tank 5 Pressure sensor (pressure detection means)
6 Motor control circuit (motor control means)
7 storing circuit 8 pneumatic equipment N rotational speed N _L low rotational speed N _H high rotational speed P pressure t detection time T time interval ΔP pressure change _{S L,} S H, S _W determination value _{K L,} K H, K _W reference Consumption Pmax Upper limit Pmin Lower limit

Claims (6)

A motor, a compressor that is driven by the motor to discharge compressed gas, a tank that stores the compressed gas discharged from the compressor, a pressure detector that detects pressure in the tank, and a pressure detector In a compressor comprising motor control means for operating the motor when the detected pressure is reduced to a lower limit value or less and stopping the motor when the pressure increases and reaches an upper limit value,
The motor control means includes
Pressure change calculating means for calculating a pressure change value at which the pressure in the tank changes at a constant time using the detection result of the pressure detecting means;
Unlike in accordance with the pressure in the tank, a value determined by a linear function of the pressure in the tank, the determination of the pressure change is a value of a pressure change corresponding to the reference consumption of the compressed gas in the tank Judgment value calculating means for calculating a value;
Determination means for determining a relationship between the determination value calculated by the determination value calculation means and the pressure change calculated by the pressure change calculation means;
A compressor comprising: a rotation speed switching means for switching the rotation speed of the motor between a low speed side and a high speed side according to a determination result of the determination means.   The determination value calculating means is configured to calculate a determination value for low speed operation when the motor is operating at a low speed, and the rotation speed switching means is configured to operate in the tank while operating the motor at a low speed. 2. The compressor according to claim 1, wherein the rotation speed of the motor is switched from a low speed to a high speed only when a pressure change is smaller than a determination value for the low speed operation.   The determination value calculating means is configured to calculate a determination value for high speed operation when the motor is operating at high speed, and the rotation speed switching means is configured to operate in the tank while operating the motor at high speed. 3. The compressor according to claim 1, wherein the rotation speed of the motor is switched from a high speed to a low speed only when a pressure change becomes equal to or higher than the determination value for the high speed operation.   The determination value calculating means is configured to calculate a determination value for a stop state when the motor is stopped, and the motor control means is configured to detect a change in pressure in the tank while the motor is stopped. The compressor according to claim 1, 2, or 3, further comprising an operation return means for returning the motor from a stopped state to an operating state when a determination value for a stopped state is reached.   5. The compressor according to claim 1, 2, 3, or 4, wherein the determination value calculation unit is configured to calculate the determination value using a rotation speed of the motor and a pressure in the tank.   The motor control means stores the pressure in the tank detected by the pressure detection means as detection data for every predetermined detection time, and the pressure change calculation means has 2 times of the detection time among the detection data. The difference between two detection data stored with a time interval more than doubled is calculated as the pressure change, and the calculated value of the pressure change is updated every detection time. Or the compressor according to 5;

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