Compressor

Abstract

Provided is a compressor capable of improving an energy saving effect corresponding to a use state of compressed gas.　A control device 10 of a compressor has a control function for switching to an unload operation of a compressor body 1 when a discharge-side pressure rises to an upper limit pressure in a load operation of the compressor body 1. The control device 10 further has a control function for switching to an eco mode in which the upper limit pressure becomes a second pressure lower than a first pressure when a cycle time is equal to or longer than a determination time in a normal mode in which the upper limit pressure is the first pressure. The control device 10 records a transition of the pressure in a tank 4 detected by a tank pressure sensor 15, calculates a recommended value of the second pressure on the basis of a maximum value of a decrease width of the pressure in the tank 4, and causes the recommended value of the second pressure to be displayed on a display unit 13.

Description

Compressor

[0001] The present invention relates to a compressor that switches between a load operation and an unload operation of a compressor body.

[0002] Patent Document 1 discloses a compressor that switches between a load operation and an unload operation of a compressor body. The compressor of Patent Document 1 includes a compressor body that compresses gas, a suction throttle valve that can close the suction side of the compressor body, a discharge valve that can release gas from the discharge side of the compressor body, a discharge side pressure sensor that detects the discharge side pressure of the compressor body, and a control device that controls the suction throttle valve and the discharge valve based on the detection result of the discharge side pressure sensor.

[0003] The control device controls the suction throttle valve to be in an open state and the discharge valve to be in a closed state to perform a load operation of the compressor body. The control device determines whether the discharge side pressure detected by the discharge side pressure sensor has risen to the upper limit pressure during the load operation of the compressor body. When the discharge side pressure has risen to the upper limit pressure, the control device switches the suction throttle valve to a closed state and the discharge valve to an open state. Thereby, the compressor body is switched to an unload operation.

[0004] The control device determines whether the discharge side pressure detected by the discharge side pressure sensor has dropped to the lower limit pressure (where the lower limit pressure < upper limit pressure) during the unload operation of the compressor body. When the discharge side pressure has dropped to the lower limit pressure, the control device switches the suction throttle valve to an open state and the discharge valve to a closed state. Thereby, the compressor body is switched to a load operation.

[0005] Japanese Patent Application Laid-Open No. 2006-152946

[0006] Although not described in Patent Document 1, it is preferable that the control device further has a control function of switching between a normal mode in which the upper limit pressure is the first pressure and an eco mode in which the upper limit pressure is a second pressure lower than the first pressure.

[0007] In normal mode, the control unit determines whether the cycle time, which is the sum of the duration of load operation and the duration of unload operation, is equal to or greater than the judgment time (in other words, whether the amount of compressed gas used is low). If the cycle time is equal to or greater than the judgment time (in other words, whether the amount of compressed gas used is low), it switches to eco mode. This results in energy savings. In eco mode, the control unit determines whether the cycle time is less than the judgment time (in other words, whether the amount of compressed gas used is high). If the cycle time is less than the judgment time (in other words, whether the amount of compressed gas used is high), it switches to normal mode.

[0008] If the second pressure, which is the upper limit pressure for eco mode, cannot be changed, or if the second pressure can be changed but is not changed appropriately, eco mode may not adequately respond to the compressed gas usage conditions, and the energy-saving effect may not be fully achieved. One of the objectives of this invention is to improve the energy-saving effect in response to the compressed gas usage conditions.

[0009] To solve the above problems, the configuration described in the claims is applied. The present invention includes a plurality of means for solving the above problems, but to give one example, a compressor body for compressing gas, a tank for temporarily storing and supplying compressed gas discharged from the compressor body to the outside, a discharge-side pressure sensor for detecting the discharge-side pressure between the compressor body and the tank, a control function that switches to unload operation of the compressor body when the discharge-side pressure rises to the upper limit pressure during load operation of the compressor body, and switches to load operation of the compressor body when the discharge-side pressure falls to the lower limit pressure during unload operation of the compressor body, and the duration of the load operation and the duration of the unload operation in a normal mode where the upper limit pressure is the first pressure A compressor comprising a control device having a control function that switches to an eco mode in which the upper limit pressure becomes a second pressure lower than the first pressure if the cycle time, which is the sum of the two values, is greater than or equal to a determination time, and switches back to the normal mode if the cycle time in the eco mode is less than the determination time, wherein the compressor comprises a display unit that displays a set value including the second pressure, an input unit that can change the set value including the second pressure, and a tank pressure sensor that detects the pressure in the tank, wherein the control device records the change in the pressure in the tank detected by the tank pressure sensor, calculates a recommended value for the second pressure based on the maximum value of the decrease in the pressure in the tank, and displays the recommended value for the second pressure on the display unit.

[0010] According to the present invention, energy-saving effects can be improved in accordance with the usage conditions of compressed gas.

[0011] Furthermore, other issues, structures, and effects not mentioned above will be clarified in the following explanation.

[0012] This is a schematic diagram showing the configuration of a compressor in one embodiment of the present invention. This is a diagram showing a specific example of the change in discharge pressure in one embodiment of the present invention. This is a diagram showing a specific example of the change in pressure inside the tank in one embodiment of the present invention, along with the maximum value of the decrease in pressure inside the tank. This is a diagram showing a specific example of the change in pressure inside the tank in one embodiment of the present invention, along with the average value of the decrease in pressure inside the tank. This is a diagram showing the screen of the display unit in one embodiment of the present invention.

[0013] One embodiment of the present invention will be described with reference to the drawings.

[0014] Figure 1 is a schematic diagram showing the configuration of the compressor in this embodiment.

[0015] The compressor of this embodiment comprises a compressor body 1 for compressing a gas such as air, a filter 2 provided on the suction side of the compressor body 1, and a tank 4 that temporarily stores the compressed gas discharged from the compressor body 1 via a discharge pipe 3 and supplies it to the outside (in other words, to the destination of the compressed gas).

[0016] The compressor body 1 includes, for example, a pair of male and female screw rotors that mesh with each other, and a casing that houses the screw rotors. Multiple working chambers are formed in the tooth grooves of the screw rotors. Each working chamber moves in the axial direction of the rotor as the rotor rotates, and sequentially performs an intake process to draw in gas, a compression process to compress the gas, and a discharge process to discharge the compressed gas.

[0017] The compressor of this embodiment includes a suction throttle valve 5 that can close the suction side of the compressor body 1, a vent valve 8 located in a pipe 7 connected, for example, between the upstream side of the check valve 6 of the discharge pipe 3 and the upstream side of the suction throttle valve 5, which allows air to be released from the discharge side of the compressor body 1, a discharge pressure sensor 9 that detects the discharge pressure between the compressor body 1 and the tank 4 (specifically, the downstream side of the check valve 6 of the discharge pipe 3), a control device 10, and a communication device 11. The compressor body 1, filter 2, suction throttle valve 5, vent valve 8, discharge pressure sensor 9, and control device 10 are housed in a casing and constitute a unit 12. The control device 10 is capable of communicating with external equipment via the communication device 11.

[0018] The control device 10 includes a processor that executes control according to a program, and a memory for storing programs and data. The control device 10 has a control function for switching between load operation and unload operation of the compressor body 1.

[0019] To explain in more detail, the control device 10 controls the suction throttle valve 5 to be in the open state and the air release valve 8 to be in the closed state to perform a load operation of the compressor body 1. During the load operation of the compressor body 1, the control device 10 determines whether the discharge pressure detected by the discharge pressure sensor 9 has risen to the upper limit pressure (details will be described later). If the discharge pressure rises to the upper limit pressure, the control device 10 switches the suction throttle valve 5 to the closed state and the air release valve 8 to the open state. This switches the compressor body 1 to unload operation.

[0020] The control device 10 determines whether the discharge pressure detected by the discharge pressure sensor 9 has dropped to the lower limit pressure Pd (where Pd < upper limit pressure) during the unload operation of the compressor body 1. If the discharge pressure has dropped to the lower limit pressure Pd, the control device 10 switches the suction throttle valve 5 to the open state and the air release valve 8 to the closed state. This switches the compressor body 1 to load operation.

[0021] The control device 10 further has a control function that switches between a normal mode in which the upper limit pressure is the first pressure Pu1 and an eco mode in which the upper limit pressure is the second pressure Pu2.

[0022] As explained in detail using Figure 2, in normal mode, the control device 10 determines whether the cycle time t, which is the sum of the duration of load operation and the duration of unload operation, is equal to or greater than the determination time (in other words, whether the amount of compressed gas used is small). If the cycle time t is equal to or greater than the determination time (in other words, if the amount of compressed gas used is small), the control device 10 switches to eco mode. In eco mode, the control device 10 gradually changes the upper limit pressure so that it decreases by a pressure range ΔP from the first pressure Pu1 (in other words, every cycle) to the second pressure Pu2.

[0023] The control device 10, in eco mode, determines whether the cycle time t is less than the determination time (in other words, whether the amount of compressed gas used is high). If the cycle time is less than the determination time (in other words, if the amount of compressed gas used is high), it switches to normal mode.

[0024] Here, if the settings including the second pressure Pu2 cannot be changed, or if the settings including the second pressure Pu2 are changeable but not changed appropriately, the eco mode may not adequately respond to the compressed gas usage, and the energy-saving effect may not be fully achieved.

[0025] Therefore, the compressor of this embodiment includes a display unit 13 that displays a set value including the second pressure Pu2 (in this embodiment, in addition to the second pressure Pu2, the pressure width ΔP and the determination time), and an input unit 14 that can change the set value including the second pressure Pu2. The display unit 13 is composed of, for example, a display, and the input unit 14 is composed of, for example, a plurality of switches. The display unit 13 and the input unit 14 may be an integrated touch panel.

[0026] Furthermore, the compressor of this embodiment is equipped with a tank pressure sensor 15 that detects the pressure inside the tank 4. The control device 10 records the changes in the pressure inside the tank 4 detected by the tank pressure sensor 15, and uses this to calculate recommended values ​​for the set values, including a recommended value for the second pressure Pu2 (in this embodiment, in addition to the recommended value for the second pressure Pu2, recommended values ​​for the pressure width ΔP and the judgment time), and displays the recommended values ​​for the set values ​​on the display unit 13.

[0027] Using Figure 3, the control device 10 extracts the maximum pressure A1 and minimum pressure B1 from the pressure changes in the tank 4 and calculates the pressure decrease ΔX1, which is the difference between them. It also extracts the maximum pressure A2 and minimum pressure B2 and calculates the pressure decrease ΔX2, which is the difference between them. Furthermore, it extracts the maximum pressure A3 and minimum pressure B3 and calculates the pressure decrease ΔX3, which is the difference between them. Then, it selects the maximum value of the pressure decrease ΔXmax from among the pressure decreases ΔX1, ΔX2, and ΔX3. Based on the maximum value ΔXmax of the pressure decrease in the tank 4, the control device 10 calculates a recommended value for the second pressure Pu2. Specifically, as the recommended value for the second pressure Pu2, it calculates a value that is, for example, (ΔXmax + Pd), or a value that is this value plus a predetermined value as a safety margin. The control device 10 displays the calculated recommended value for the second pressure Pu2 on the display unit 13. If the recommended value for the second pressure Pu2 mentioned above is set, even if the pressure inside the tank 4 drops by the maximum value ΔXmax, it can be prevented from falling below the minimum pressure Pd, and compressed gas can be stably supplied from the tank 4 to the outside.

[0028] As explained using Figure 4, the control device 10 extracts the maximum pressure A1 and minimum pressure B1 from the pressure changes in the tank 4 and calculates the pressure decrease rate ΔY1, which is the rate of change between them. It also extracts the maximum pressure A2 and minimum pressure B2 and calculates the pressure decrease rate ΔY2, which is the rate of change between them. Furthermore, it extracts the maximum pressure A3 and minimum pressure B3 and calculates the pressure decrease rate ΔY3, which is the rate of change between them. Then, it calculates the average value ΔYave of the pressure decrease rates ΔY1, ΔY2, and ΔY3. Based on the average value ΔYave of the pressure decrease rates in the tank 4, the control device 10 calculates a recommended value for the pressure width ΔP. Specifically, the recommended value for the pressure width ΔP is calculated to be, for example, a value of (t × ΔYave), or a value obtained by subtracting a predetermined value as a safety margin from this value. The control device 10 displays the calculated recommended value for the pressure width ΔP on the display unit 13. If the recommended value for the pressure range ΔP mentioned above is set, it is possible to prevent the upper limit pressure from reaching the second pressure Pu2 during the first cycle of eco mode. If the upper limit pressure were to reach the second pressure Pu2 during the first cycle of eco mode, the amount of compressed gas produced would become insufficient under conditions where the amount of compressed gas used is above a certain level, and the pressure inside tank 4 could fall below the minimum pressure Pd. By preventing the upper limit pressure from reaching Pu2 during the first cycle of eco mode, it is possible to prevent a drastic decrease in the amount of compressed gas produced, and to stably supply compressed gas from tank 4 to the outside.

[0029] The control device 10 estimates the cycle time t2 when the upper limit pressure becomes the second pressure Pu2, based on the cycle time t1 when the upper limit pressure is the first pressure Pu1 (in other words, in normal mode) and the second pressure Pu2. It then calculates a recommended value for the determination time so that it is smaller than the estimated cycle time t2 by a predetermined value, and displays the recommended value for the determination time on the display unit 13. Once the aforementioned recommended value for the determination time is set, the eco mode can be maintained under the condition that the amount of compressed gas used remains unchanged.

[0030] The display unit 13 displays, for example, the screen 20 shown in Figure 5. The screen 20 has a second pressure recommended value display field 21, a pressure width recommended value display field 22, a judgment time recommended value display field 23, a second pressure change field 24, a pressure width change field 25, a judgment time change field 26, and a confirmation button 27.

[0031] The second pressure recommended value display field 21, the pressure width recommended value display field 22, and the judgment time recommended value display field 23 display the recommended values ​​for the second pressure Pu2, the pressure width ΔP, and the judgment time, respectively, calculated by the control device 10. The second pressure change field 24, the pressure width change field 25, and the judgment time change field 26 display the current values ​​for the second pressure Pu2, the pressure width ΔP, and the judgment time, respectively, as default values.

[0032] The user can change the setting of the second pressure Pu2 by referring to the recommended value of the second pressure Pu2 displayed in the second pressure recommendation value display field 21, changing the second pressure Pu2 displayed in the second pressure change field 24 using the input unit 14, and operating the confirmation button 27. The user can change the setting of the pressure width ΔP by referring to the recommended value of the pressure width ΔP displayed in the pressure width recommendation value display field 22, changing the pressure width ΔP displayed in the pressure width change field 25 using the input unit 14, and operating the confirmation button 27. The user can change the setting of the judgment time by referring to the recommended value of the judgment time displayed in the judgment time recommendation value display field 23, changing the judgment time displayed in the judgment time change field 26 using the input unit 14, and operating the confirmation button 27. Therefore, it is possible to respond to the usage conditions of compressed gas and improve energy saving effects.

[0033] In the above embodiment, the control device 10 was described as calculating and displaying on the display unit 13 a recommended value for the second pressure Pu2, as well as a recommended value for the pressure width ΔP and a recommended value for the determination time, but it is not limited to this. The control device 10 may calculate and display only the recommended value for the second pressure Pu2 on the display unit 13, or it may calculate and display on the display unit 13 only one of the recommended values ​​for the pressure width ΔP and the recommended value for the determination time, along with the recommended value for the second pressure Pu2.

[0034] Furthermore, although the above embodiment described an example in which the compressor is equipped with both a suction throttle valve 5 and a vent valve 8, it is not limited to this, and may be equipped with only one of the suction throttle valve 5 and the vent valve 8.

[0035] 1... Compressor body, 4... Tank, 9... Discharge side pressure sensor, 10... Control device, 13... Display unit, 14... Input unit, 15... Tank pressure sensor

Claims

1. A compressor comprising: a compressor body for compressing gas; a tank for temporarily storing and supplying compressed gas discharged from the compressor body to the outside; a discharge-side pressure sensor for detecting the discharge-side pressure between the compressor body and the tank; a control function that switches to unload operation of the compressor body when the discharge-side pressure rises to an upper limit pressure during load operation of the compressor body, and switches back to load operation of the compressor body when the discharge-side pressure falls to a lower limit pressure during unload operation of the compressor body; and a control device that switches to an eco mode where the upper limit pressure becomes a second pressure lower than the first pressure when the cycle time, which is the sum of the duration of load operation and the duration of unload operation, is greater than or equal to a determination time in normal mode where the upper limit pressure is a first pressure, and switches back to normal mode when the cycle time in eco mode is less than the determination time, wherein the compressor further comprises: a display unit for displaying a set value including the second pressure; an input unit for changing the set value including the second pressure; and a tank pressure sensor for detecting the pressure inside the tank. The compressor is characterized in that the control device records the changes in the pressure inside the tank detected by the tank pressure sensor, calculates a recommended value for the second pressure based on the maximum value of the decrease in pressure inside the tank, and displays the recommended value for the second pressure on the display unit.

2. The compressor according to claim 1, wherein the control device changes the upper limit pressure in stages in the eco mode such that the pressure decreases in stages from the first pressure to the second pressure.

3. The compressor according to claim 2, wherein the control device calculates a recommended value for the pressure range based on the average value of the rate of decrease of pressure in the tank, and displays the recommended value for the pressure range on the display unit.

4. The compressor according to claim 1, wherein the control device estimates the cycle time when the upper limit pressure becomes the second pressure based on the cycle time when the upper limit pressure is the first pressure and the second pressure, calculates a recommended value for the determination time such that it is less than the estimated cycle time by a predetermined value, and displays the recommended value for the determination time on the display unit.

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