Rotation speed control method and rotation speed control device for engine-driven compressor

Abstract

The invention provides a rotational speed control method and a rotational speed control device for an engine-driven compressor. The purpose of the present invention is to control the rotational speed of an engine-driven compressor, whereby the rotational speed can approach a target rotational speed regardless of fluctuations in the load applied to an engine. An electronic control device (controller) for outputting a control signal for specifying a target rotational speed to an ECU of an engine is provided, and an allowable range for the target rotational speed is stored in a storage means of the electronic control device. During operation of the engine-driven compressor, the rotation speed of the engine is compared with the upper limit speed and the lower limit speed of an allowable range for a specified target rotation speed, and when the rotation speed is lower than the lower limit speed of the allowable range or exceeds the upper limit speed, the rotation speed of the engine is controlled. The rotation speed is corrected so as to gradually increase or decrease the specified target rotation speed until the rotation speed is within the allowable range.

Description

Technical Field

[0001] The present invention relates to a rotational speed control method and a rotational speed control device for an engine-driven compressor, and more particularly, to a rotational speed control method and a rotational speed control device for an engine-driven compressor that suppress an excessive decrease and / or excessive increase in rotational speed caused by changes in the load applied to the engine during unloaded operation and / or full-load operation. Background Art

[0002] As an example of an engine driven compressor, if we refer to Figure 7 A structural example of an oil-cooled engine-driven compressor 100 will be described. The oil-cooled engine-driven compressor 100 includes an oil-cooled compressor body 120 , an engine 130 that drives the compressor body 120 , and a receiving container 140 that introduces compressed gas discharged from the compressor body 120 .

[0003] The oil-cooled compressor body 120 is constructed as follows: the air sucked in through the suction port and other compressed gases are compressed together with the lubricating oil supplied into the compression action space for lubrication, sealing and cooling, and the compressed gas is ejected as a gas-liquid mixed fluid mixed with the lubricating oil. In this way, the compressed gas ejected as a gas-liquid mixed fluid mixed with the lubricating oil can be introduced into the aforementioned receiving container 140 to perform gas-liquid separation, and the compressed gas after the lubricating oil is separated can be supplied to the consumption side.

[0004] The engine driven compressor 100 configured as described above is provided with a capacity control device 200 so as to stably supply compressed gas to the consumption side.

[0005] As such a capacity control device 200, Figure 7 The engine driven compressor 100 shown has the following structure: an unloader valve 121 is provided for controlling the opening and closing of the suction port of the compressor body 120, and a control piping 150 is provided for introducing the compressed gas in the receiving container 140 into the closed valve pressure receiving chamber 122 of the unloader valve 121, and a pressure regulator 151 is provided on the control piping 150.

[0006] Furthermore, the structure is as follows: a pressure detection mechanism (pressure sensor) 160 is provided for detecting the pressure (control pressure P) in the control piping 150 on the secondary side of the pressure regulator 151, and an electronic control unit (controller) 170 outputs a control signal for specifying a target rotational speed Rt to an engine control unit (ECU) 131 of the engine 130 based on the pressure detected by the pressure detection mechanism 160. By performing the following “full load operation”, “unload operation” and “intermediate operation” according to changes in the control pressure P, the aforementioned capacity control can be performed.

[0007] (Full-load operation) If the pressure in the receiving container 140 drops below the operating start pressure of the pressure regulator 151, causing the pressure regulator 151 to close the control pipe 150 and the control pressure P detected by the pressure detection mechanism 160 to drop to a predetermined full-load operation start pressure Pfl (for example, gauge pressure is 0 MPa), the supply of compressed gas to the valve closing pressure chamber 122 of the unloading valve 121 provided at the suction port of the compressor main body 120 is stopped. The unloading valve 121 fully opens, and the electronic control device (controller) 170 outputs a control signal to the ECU 131 designating the full-load rotation speed Rfl, which is the upper limit rotation speed during capacity control, as the target rotation speed Rt, starting full-load operation to increase the rotation speed of the engine 130.

[0008] (Unloading operation) On the other hand, if the control pressure P rises above a predetermined unloading operation start pressure Pul due to the stoppage of consumption of compressed gas by the pneumatic equipment on the consumption side or the like, the unloading valve 121 provided at the suction port of the compressor main body 120 closes the suction port, stopping the suction of the compressor main body 120. The electronic control device (controller) 170 outputs a control signal to the ECU 131 designating the unloading rotation speed Rul, which is the lower limit rotation speed during capacity control, as the target rotation speed Rt, shifting to unloading operation to decrease the rotation speed of the engine 130.

[0009] (Intermediate operation) Moreover, when the control pressure P is in a pressure range (Pfl < P < Pul) that exceeds the full-load operation start pressure Pfl and is less than the unloading operation start pressure Pul, intermediate operation is performed. During this intermediate operation, as the control pressure P rises, the unloading valve 121 is throttled, and the control signal output to the ECU 131 is changed in such a way as to decrease the target rotation speed Rt designated for the ECU 131 of the engine 130. On the other hand, as the control pressure P decreases, the opening degree of the unloading valve 121 increases, and the control signal is changed in such a way as to increase the target rotation speed Rt designated for the ECU 131 of the engine 130.

[0010] In this way, it is configured to generate and supply compressed gas corresponding to the change in the consumption amount of compressed gas on the consumption side by switching the operating state of the engine-driven compressor 100 among full-load operation, unloading operation, and intermediate operation, thereby enabling stable supply of compressed gas to the consumption side.

[0011] Here, in the engine driven compressor 100, the input shaft of the compressor body 120 is connected to the output shaft of the engine 130 via the coupling 180. If the unload rotation speed Rul is reduced to the minimum rotation speed Rmin of the engine 130, the risk of damage to the coupling 180 increases due to vibration caused by resonance.

[0012] In addition, during unloading operation, although it can be said that the compressor body 120 closes the suction port and becomes a no-load operating state, since the compressor body 120 is rotated, it operates under a loaded state compared to the operating state of the engine 130 alone. Therefore, if the unloading rotation speed Rul is reduced to the minimum rotation speed Rmin of the engine 130, there is a risk that the starting performance of the engine 130 will deteriorate due to insufficient torque, and there is a risk of the engine stalling during no-load operation.

[0013] On the other hand, if the full load rotation speed Rfl is increased to the maximum rotation speed Rmax of the engine 130, the engine 130 is operated at a high rotation speed when generating compressed gas, so there is a risk that fuel consumption will deteriorate.

[0014] In addition, generally speaking, the torque generated by the engine 130 reaches its peak at a rotational speed lower than the maximum rotational speed Rmax, but in the engine-driven compressor 100, the load (torque) applied to the engine 130 reaches its peak when operating at full load. Therefore, for the engine of an engine-driven compressor that rotates at high speed under high load like this, the engine manufacturer sometimes recommends or specifies that a rotational speed lower than the maximum rotational speed Rmax disclosed as the engine specification be set as the upper limit of the operating speed range.

[0015] Therefore, if Figure 8 As shown, the rotational speed range (unload rotational speed Rul to full load rotational speed Rfl) for capacity control is usually set to a narrower range than the rotational speed range (minimum rotational speed Rmin to maximum rotational speed Rmax) of the engine itself, and the target rotational speed Rt of the engine 130 is set to the unload rotational speed Rul during unload operation, so that the rotational speed of the engine 130 will not be lower than the minimum rotational speed Rmin, and the target rotational speed Rt of the engine 130 is set to the full load rotational speed Rfl during full load operation, so that the rotational speed of the engine 130 will not be higher than the maximum rotational speed Rmax.

[0016] In addition, although it is not an invention related to the control of the rotational speed of the engine of the engine-driven compressor, the following patent document 1 proposes: as an engine rotational speed control, droop control is performed when the engine is between the minimum rotational speed and the maximum rotational speed, and the rotational speed is controlled in a manner such that the output of the engine is fixed according to the change in load. On the other hand, when the engine rotational speed is lower than the minimum rotational speed of the engine and exceeds the maximum rotational speed of the engine, switching is performed to isochronous control for maintaining the engine rotational speed fixed regardless of the load change. By maintaining the engine rotational speed fixed at the minimum rotational speed when the engine rotational speed is lower than the minimum rotational speed of the engine and maintaining the speed fixed at the maximum rotational speed when the engine rotational speed exceeds the maximum rotational speed of the engine, the engine can be prevented from stalling or overspeeding.

[0017] Patent Document 1: Japanese Patent Application Publication No. 2015-45255

[0018] As described above, in the engine-driven compressor, the engine's rotational speed range during capacity control (unload rotational speed Rul to full-load rotational speed Rfl) is set to be narrower than the engine's rotational speed range (minimum rotational speed Rmin to maximum rotational speed Rmax), and a control signal is output to ECU131 during unload operation to designate the unload rotational speed Rul as the target rotational speed Rt, and a control signal is output to ECU131 during full-load operation to designate the full-load rotational speed Rfl as the target rotational speed Rt.

[0019] Thus, ECU131 operates the engine at a fixed fuel injection amount corresponding to a predetermined unload rotational speed Ru1 which is a target rotational speed Rt during unload operation in accordance with a control signal received from the electronic control unit 170, and operates the engine at a fixed fuel injection amount corresponding to a predetermined full load rotational speed Rf1 which is a target rotational speed Rt during full load operation.

[0020] On the other hand, even if the load applied to the engine 130 changes by changing the control pressure P, which is the discharge side pressure of the compressor body 120, within the range above the unload operation start pressure Pul or below the full load operation start pressure Pfl, the target rotation speed Rt specified by the ECU 131 is maintained fixed, the fuel injection does not change, and therefore the rotation speed of the engine changes.

[0021] Therefore, even if the unload rotation speed Rul is set to be higher than the minimum rotation speed Rmin of the engine, and the full load rotation speed Rfl is set to be lower than the maximum rotation speed Rmax of the engine, the engine rotation speed R may drop below the minimum rotation speed Rmin during unload operation, or the engine rotation speed R may rise to above the maximum rotation speed Rmax during full load operation.

[0022] Furthermore, in the engine driven compressor 100 , when the rotation speed R of the engine 130 becomes lower than the minimum rotation speed Rmin, not only the coupling 180 described above may be damaged by vibration due to resonance, but also the engine 130 may stall.

[0023] Furthermore, if the engine 130 is operated for a long time in a state where the rotation speed R is increased to or higher than the maximum rotation speed Rmax and exceeds the speed limit, this may cause a failure such as engine explosion.

[0024] Therefore, even when the load applied to the engine changes during unloading operation and full-load operation, the engine rotation speed needs to be maintained near the unloading rotation speed Ru1 during unloading operation and not be reduced to the minimum rotation speed Rmin, and the engine 130 rotation speed needs to be maintained near the full-load rotation speed Rf1 during full-load operation and not be increased to the maximum rotation speed Rmax.

[0025] Here, by applying the control method described in the aforementioned patent document 1 to the rotational speed control of the engine of the engine-driven compressor, when the rotational speed of the engine is lower than the minimum rotational speed Rmin, or when it exceeds the maximum rotational speed Rmax, the rotational speed control is switched from droop control to isochronous control, so that the minimum rotational speed Rmin or the maximum rotational speed Rmax is maintained fixed, thereby preventing the rotational speed R of the engine from being significantly lower than the minimum rotational speed Rmin, or significantly exceeding the maximum rotational speed Rmax.

[0026] However, when the control method of Patent Document 1 is applied to the control of the engine of the engine-driven compressor, the rotational speed R of the engine still changes until it exceeds the unload rotational speed Ru1 and the full-load rotational speed Rf1 and then reaches the minimum rotational speed Rmin and the maximum rotational speed Rmax. Even if the control method of Patent Document 1 is directly applied to the rotational speed control of the engine 130 of the engine-driven compressor 100, the aforementioned problem cannot be eliminated.

[0027] In addition, it is also possible to consider changing the minimum rotational speed Rmin and the maximum rotational speed Rmax set as thresholds in the control method of Patent Document 1 to the unload rotational speed Rul and the full-load rotational speed Rfl. When the engine rotational speed is lower than the unload rotational speed Rul or exceeds the full-load rotational speed Rfl, the droop control is switched to the isochronous control. Even if the load applied to the engine changes, the engine rotational speed is maintained fixed at the unload rotational speed Rul during unload operation, and is maintained fixed at the full-load rotational speed Rfl during full-load operation.

[0028] However, when performing such control, it is necessary to always calculate the engine rotation speed for droop control and isochronous control, which makes the control complicated, and requires a controller with high computing processing power that pre-stores programs for droop control and isochronous control, which increases the manufacturing cost of the engine-driven compressor.

[0029] On the other hand, if it is possible to prevent the rotational speed during unloading operation and the rotational speed during full load operation from reaching the minimum rotational speed Rmin and the maximum rotational speed Rmax, it is sufficient to maintain the rotational speed during unloading operation and the rotational speed during full load operation within a range of rotational speeds with a certain degree of amplitude, and there is no need for accurate control such as isochronous control to fix the unloading rotational speed Rul and the full load rotational speed Rfl. Summary of the invention

[0030] Therefore, in view of the shortcomings of the above-mentioned prior art, the present invention aims to provide a rotational speed control method for an engine-driven compressor and a rotational speed control device for executing the rotational speed control method, which, through a relatively simple structure, can make the rotational speed R of the engine close to the target rotational speed Rt even when the rotational speed of the engine deviates from the target rotational speed Rt due to changes in the load on the engine applied to the engine-driven compressor.

[0031] In addition, an object of the present invention is to provide a rotational speed control method for an engine-driven compressor and a rotational speed control device for executing the rotational speed control method, which, through a relatively simple structure, can make the rotational speed of the engine close to the unloading rotational speed Rul without being reduced to the minimum rotational speed Rmin even when the rotational speed of the engine is reduced due to load changes generated when the engine-driven compressor is in an unloaded operating state.

[0032] Furthermore, an object of the present invention is to provide a rotational speed control method for an engine-driven compressor and a rotational speed control device for executing the rotational speed control method, which, through a relatively simple structure, can make the engine rotational speed close to the full-load rotational speed Rfl without rising to the maximum rotational speed Rmax even if the engine rotational speed increases due to load changes generated when the engine-driven compressor is in a full-load operating state.

[0033] The means for solving the technical problem will be described below together with the reference numerals used in the embodiments of the invention. The reference numerals are recorded to make the correspondence between the claims and the embodiments of the invention clear, and are certainly not used to limit the interpretation of the technical scope of the present invention.

[0034] In order to achieve the above-mentioned object, in a rotation speed control method of an engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 that realizes a fuel injection amount corresponding to a specified target rotation speed Rt, the rotation speed control method of the engine-driven compressor specifies the target rotation speed Rt corresponding to a control pressure P as a pressure on the discharge side of the compressor body 20 based on a predetermined correspondence relationship and drives the engine 30, wherein a predetermined allowable range is set for the target rotation speed Rt, the rotation speed R of the engine is monitored, and when the rotation speed R of the engine is lower than a lower limit speed of the allowable range for the specified target rotation speed Rt or exceeds an upper limit speed of the allowable range, a rotation speed correction is performed to gradually increase or decrease the specified target rotation speed Rt until the rotation speed R of the engine 30 becomes a rotation speed within the allowable range (method 1).

[0035] In another rotation speed control method of an engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 that realizes a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined minimum rotation speed Rmin, the rotation speed control method of the engine-driven compressor closes the suction port of the compressor body 20 according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, and performs an unloaded operation of driving the engine 30 with an unloaded rotation speed Rul as the target rotation speed Rt, the unloaded rotation speed Rul being a rotation speed higher by a predetermined amount than the minimum rotation speed Rmin, wherein a lower limit unloaded rotation speed Rul (L) (as an example, 1300 rpm) and an upper limit unloaded rotation speed Rul (H) (as an example, 1350 rpm) are set, the lower limit unloaded rotation speed Rul (L) being higher than the engine 3 0 is a rotation speed that is higher than the minimum rotation speed Rmin by a predetermined margin and is lower than the unloading rotation speed Rul, the upper limit unloading rotation speed Rul(H) is a rotation speed that is higher than the lower limit unloading rotation speed Rul(L) by a predetermined amount and is a rotation speed that is higher than the unloading rotation speed Rul(L), and is a rotation speed that is higher than the unloading rotation speed Rul, during the unloading operation, the rotation speed R of the engine 30 is monitored, and an unloading rotation speed increase correction and an unloading rotation speed decrease correction are repeatedly performed, the unloading rotation speed increase correction is performed when the rotation speed R of the engine 30 is less than the lower limit unloading rotation speed Rul(L), and the target rotation speed Rt is gradually increased from the unloading rotation speed Rul until the rotation speed R of the engine 30 rises to the lower limit unloading rotation speed Rul(L), and the unloading rotation speed decrease correction is performed when the rotation speed R of the engine 30 exceeds the upper limit unloading rotation speed Rul(H), and the target rotation speed Rt increased by the unloading rotation speed increase correction is gradually decreased until the rotation speed R of the engine 30 drops to the upper limit unloading rotation speed Rul(H) (method 2).

[0036] In another rotation speed control method of an engine driven compressor of the present invention, the engine driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 for realizing a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined maximum rotation speed Rmax, the rotation speed control method of the engine driven compressor fully opens the suction port of the compressor body 20 according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, and performs a full load operation of driving the engine 30 with a full load rotation speed Rfl as the target rotation speed Rt, wherein an upper limit full load rotation speed Rfl (H) (as an example, 1850 rpm) and a lower limit full load rotation speed Rfl (L) (as an example, 1750 rpm) are set, the upper limit full load rotation speed Rfl (H) being a value lower than the maximum rotation speed Rmax. The maximum rotation speed Rmax of the engine 30 is a rotation speed that is lower than the maximum rotation speed Rmax by a predetermined margin and is higher than the full load rotation speed Rfl, the lower limit full load rotation speed Rfl (L) is a rotation speed that is lower than the upper limit full load rotation speed Rfl (H) by a predetermined amount and is lower than the full load rotation speed Rfl, and during the full load operation, the rotation speed R of the engine 30 is monitored, and full load rotation speed reduction correction and full load rotation speed increase correction are repeatedly performed, the full load rotation speed reduction correction is performed when the rotation speed R of the engine 30 exceeds the upper limit When the full load rotation speed is Rfl(H), the target rotation speed Rt is gradually reduced from the full load rotation speed Rfl until the rotation speed R of the engine 30 drops to the upper limit full load rotation speed Rfl(H), and when the full load rotation speed increase correction is made when the rotation speed R of the engine is less than the lower limit full load rotation speed Rfl(L), the target rotation speed Rt reduced by the full load rotation speed reduction correction is gradually increased until the rotation speed R of the engine 30 rises to the lower limit full load rotation speed Rfl(L) (method 3).

[0037] In addition, in another rotation speed control method of an engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 for realizing a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined maximum rotation speed Rmax and a minimum rotation speed Rmin. In the rotation speed control method of the engine-driven compressor, according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, when the control pressure P is below a predetermined full-load operation start pressure Pfl, the suction port of the compressor body 20 is fully opened, and the full load operation is performed. The full-load operation of the engine 30 is driven by taking the load rotation speed Rfl as the target rotation speed Rt, the full-load rotation speed Rfl is a rotation speed that is a predetermined amount lower than the maximum rotation speed Rmax, and when the control pressure P is above the unloading operation start pressure Pul, the suction port of the compressor main body 20 is closed, and the unloading operation of the engine 30 is driven by taking the unloading rotation speed Rul as the target rotation speed Rt, the unloading operation start pressure Pul is a pressure that is a predetermined amount higher than the full-load operation start pressure Pfl, the unloading rotation speed Rul is a rotation speed that is a predetermined amount higher than the minimum rotation speed Rmin, and is a predetermined amount lower than the full-load rotation speed Rfl. The rotation speed of the engine 30 is set to a certain amount, wherein a lower limit unloading rotation speed Rul (L) (as an example, 1300 rpm) and an upper limit unloading rotation speed Rul (H) (as an example, 1350 rpm) are set, wherein the lower limit unloading rotation speed Rul (L) is a rotation speed that is higher than the minimum rotation speed Rmin of the engine 30 by a predetermined margin and is lower than the unloading rotation speed Rul, and the upper limit unloading rotation speed Rul (H) is a rotation speed that is higher than the lower limit unloading rotation speed Rul (L) by a predetermined amount and is higher than the unloading rotation speed Rul, and the upper limit full load rotation speed Rfl (H) (as an example, 1850 rpm) and the lower limit full load rotation speed R fl(L) (for example, 1750 rpm), the upper limit full load rotation speed Rfl(H) is a rotation speed that is lower than the maximum rotation speed Rmax of the engine 30 by a predetermined margin and is higher than the full load rotation speed Rfl, the lower limit full load rotation speed Rfl(L) is a rotation speed that is lower than the upper limit full load rotation speed Rfl(H) by a predetermined amount and is lower than the full load rotation speed Rfl, the rotation speed R of the engine is monitored, and in the unloading operation, an unloading rotation speed increase correction and an unloading rotation speed decrease correction are repeatedly performed, and the unloading rotation speed increase correction is performed when the rotation speed R of the engine 30 is lower than the lower limit unloading rotation speed Ru1(L),The target rotational speed Rt is gradually increased from the unload rotational speed Rul until the rotational speed R of the engine 30 rises to the lower limit unload rotational speed Rul(L), and when the rotational speed R of the engine 30 exceeds the upper limit unload rotational speed Rul(H), the target rotational speed Rt increased by the unload rotational speed increase correction is gradually decreased until the rotational speed R of the engine 30 drops to the upper limit unload rotational speed Rul(H), and in the full load operation, the full load rotational speed reduction correction and the full load rotational speed increase correction are repeated, and the full load rotation The speed reduction correction is to gradually reduce the target rotational speed Rt from the full load rotational speed Rfl when the rotational speed R of the engine 30 exceeds the upper limit full load rotational speed Rfl (H) until the rotational speed R of the engine 30 drops to the upper limit full load rotational speed Rfl (H). The full load rotational speed increase correction is to gradually increase the target rotational speed Rt reduced by the full load rotational speed reduction correction when the rotational speed R of the engine 30 is less than the lower limit full load rotational speed Rfl (L) until the rotational speed R of the engine 30 rises to the lower limit full load rotational speed Rfl (L) (method 4).

[0038] In the rotation speed control method, it is preferred that a decrease rate (D / 2C) of the target rotation speed Rt in the unload rotation speed decrease correction is made slower than an increase rate (B / 2A) of the target rotation speed Rt in the unload rotation speed increase correction (method 5).

[0039] Furthermore, it is preferable that an increase rate (H / 2G) of the target rotational speed Rt in the full load rotational speed increase correction is made slower than a decrease rate (F / 2E) of the target rotational speed Rt in the full load rotational speed decrease correction (method 6).

[0040] Furthermore, it is preferred to make the decrease speed (D / 2C) of the target rotational speed Rt in the unload rotational speed decrease correction slower than the increase speed (B / 2A) of the target rotational speed Rt in the unload rotational speed increase correction, and to make the increase speed (H / 2G) of the target rotational speed Rt in the full load rotational speed increase correction slower than the decrease speed (F / 2E) of the target rotational speed Rt in the full load rotational speed decrease correction (Method 7).

[0041] Furthermore, the number of times n that the rotational speed R of the engine 30 is lower than the lower limit unloading rotational speed Rul (L) during one unloading operation may be counted, and as the counted number n increases, the increase rate of the target rotational speed Rt in the unloading rotational speed increase correction may be slowed down, and / or the decrease rate of the target rotational speed Rt in the unloading rotational speed decrease correction may be slowed down (method 8).

[0042] Similarly, the number of times N that the rotational speed R of the engine 30 exceeds the upper limit full load rotational speed Rfl (H) during a full load operation may be counted, and as the count number N increases, the decrease rate of the target rotational speed Rt in the full load rotational speed decrease correction may be slowed down, and / or the increase rate of the target rotational speed Rt in the full load rotational speed increase correction may be slowed down (Method 9).

[0043] In addition, in the rotation speed control device 10 of the engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 that realizes a fuel injection amount corresponding to a specified target rotation speed Rt, the rotation speed control device 10 of the engine-driven compressor includes an electronic control device (controller) 70, the electronic control device (controller) 70 outputs a control signal specifying the target rotation speed Rt corresponding to a control pressure P to the engine control unit 31 based on a predetermined correspondence relationship, the control pressure P being the pressure on the discharge side of the compressor body 20 detected by the pressure detection mechanism 60, wherein the The electronic control unit 70 comprises: a storage mechanism 71 for storing a predetermined allowable range set for the target rotational speed Rt; a rotational speed acquisition mechanism 72 for acquiring the rotational speed R of the engine 30; and a rotational speed correction mechanism (74 to 77) for comparing the rotational speed R of the engine 30 acquired by the rotational speed acquisition mechanism 72 with the upper limit speed of the allowable range and the lower limit speed of the allowable range for the specified target rotational speed Rt, and when the rotational speed R of the engine 30 is less than the lower limit speed of the allowable range or exceeds the upper limit speed of the allowable range, gradually increasing or decreasing the specified target rotational speed Rt until the rotational speed R of the engine 30 becomes a rotational speed within the allowable range (method 10).

[0044] In addition, in another rotation speed control device 10 of an engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 for realizing a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined minimum rotation speed Rmin, and the rotation speed control device 10 of the engine-driven compressor closes the suction port of the compressor body 20 according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, and performs the unloading rotation speed Rul as the desired value when the control pressure P is above a predetermined unloading operation start pressure Pul. The target rotational speed Rt is used to drive the unloading operation of the engine 30, and the unloading rotational speed Rul is a rotational speed that is higher than the minimum rotational speed Rmin by a predetermined amount, wherein the rotational speed control device 10 of the engine-driven compressor is provided with: a pressure detection mechanism 60, which detects the control pressure P; and an electronic control device (controller) 70, which outputs a control signal specifying the target rotational speed Rt to the engine control unit 31 according to the control pressure P detected by the pressure detection mechanism 60, and the electronic control device 70 is provided with: a storage mechanism 71, which stores a lower limit unloading rotational speed Rul (L) (as an example, 1300 rpm) and an upper limit unloading rotational speed R ul(H) (for example, 1350rpm), the lower limit unloading rotational speed Rul(L) is higher than the minimum rotational speed Rmin of the engine 30 by a predetermined margin and is set to a rotational speed below the unloading rotational speed Rul, the upper limit unloading rotational speed Rul(H) is a rotational speed higher than the lower limit unloading rotational speed Rul(L) by a predetermined amount and is set to a rotational speed above the unloading rotational speed Rul; a rotational speed acquisition mechanism 72, which acquires the rotational speed R of the engine 30; a control signal output mechanism 73, which outputs a signal to the pressure detection mechanism 60 when the pressure detection mechanism 60 detects a pressure higher than the unloading operation start pressure Pul as the control pressure P. The engine control unit 31 outputs a control signal that sets the unloading rotation speed Ru1 to the target rotation speed Rt; the unloading rotation speed increasing mechanism 74 compares the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 with the lower limit unloading rotation speed Ru1(L) stored in the storage mechanism 71 during unloading operation, and when the rotation speed R of the engine 30 is less than the lower limit unloading rotation speed Ru1(L), the control signal output by the control signal output mechanism 73 is changed in such a way that the target rotation speed Rt gradually increases from the unloading rotation speed Ru1 until the rotation speed R of the engine 30 rises to the lower limit unloading rotation speed Ru1(L);and an unloading rotation speed reducing mechanism 75, which changes the control signal output by the control signal output mechanism 73 in such a manner that the target rotation speed Rt increased by the unloading rotation speed increasing mechanism 74 gradually decreases when the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 exceeds the upper limit unloading rotation speed Rul(H) during the unloading operation, until the rotation speed R of the engine 30 drops to the upper limit unloading rotation speed Rul(H) (mode 11). ;

[0045] In addition, in another rotation speed control device 10 of an engine-driven compressor of the present invention, the engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 that realizes a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined maximum rotation speed Rmax. The rotation speed control device 10 of the engine-driven compressor fully opens the suction port of the compressor body 20 and increases the full load rotation speed Rf according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, and when the control pressure P is below a predetermined full load operation start pressure Pfl. l as the target rotational speed Rt to drive the full-load operation of the engine 30, the full-load rotational speed Rfl being a rotational speed lower by a predetermined amount than the maximum rotational speed Rmax, wherein the rotational speed control device 10 of the engine-driven compressor is provided with: a pressure detection mechanism 60 for detecting the control pressure P; and an electronic control device (controller) 70 for outputting a control signal specifying the target rotational speed Rt to the engine control unit 31 according to the control pressure P detected by the pressure detection mechanism 60, wherein the electronic control device 70 is provided with: a storage mechanism 71 for storing an upper limit full-load rotational speed Rfl (H) (as an example, 1850 rpm) and a lower limit full-load rotational speed The upper limit full load rotation speed Rfl(H) is lower than the maximum rotation speed Rmax of the engine 30 by a predetermined margin and is set to a rotation speed higher than the full load rotation speed Rfl; the lower limit full load rotation speed Rfl(L) is a rotation speed lower than the upper limit full load rotation speed Rfl(H) by a predetermined amount and is set to a rotation speed lower than the full load rotation speed Rfl; a rotation speed acquisition mechanism 72, which acquires the rotation speed R of the engine 30; a control signal output mechanism 73, which outputs a signal to the pressure detection mechanism 60 when the pressure detection mechanism 60 detects a pressure lower than the full load operation start pressure Pfl as the control pressure P. The engine control unit 31 outputs a control signal that sets the full-load rotational speed Rfl as a target rotational speed Rt; the full-load rotational speed reducing mechanism 76 compares the rotational speed R of the engine 30 obtained by the rotational speed obtaining mechanism 72 with the upper limit full-load rotational speed Rfl (H) stored in the storage mechanism 71 during full-load operation, and when the rotational speed R of the engine 30 exceeds the upper limit full-load rotational speed Rfl (H), changes the control signal output by the control signal output mechanism 73 in such a manner that the target rotational speed Rt is gradually reduced from the full-load rotational speed Ru1 until the rotational speed R of the engine 30 drops to the upper limit full-load rotational speed Rfl (H);and a full-load rotation speed increasing mechanism 77, which changes the control signal output by the control signal output mechanism 73 in such a manner that the target rotation speed Rt reduced by the full-load rotation speed reducing mechanism 76 gradually increases when the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 is less than the lower limit full-load rotation speed Rfl(L) during the full-load operation, until the rotation speed R of the engine 30 rises to the lower limit full-load rotation speed Rfl(L) (mode 12). ;

[0046] In addition, in another rotation speed control device 10 of the present invention, an engine-driven compressor includes an engine 30 and a compressor body 20 driven by the engine 30, the engine 30 includes an engine control unit (ECU) 31 that realizes a fuel injection amount corresponding to a specified target rotation speed Rt, and has a predetermined maximum rotation speed Rmax and a minimum rotation speed Rmin. In the rotation speed control device 10 of the engine-driven compressor, according to a change in a control pressure P as a pressure on the discharge side of the compressor body 20, when the control pressure P is less than a predetermined full-load operation start pressure Pfl, the suction port of the compressor body 20 is fully opened, and the engine 30 is driven with the full-load rotation speed Rfl as the target rotation speed Rt. The full-load operation, the full-load rotation speed Rfl is a rotation speed lower than the maximum rotation speed Rmax by a predetermined amount, and when the control pressure P is above the unloading operation start pressure Pul, the suction port of the compressor body 20 is closed, and the unloading operation of the engine 30 is driven by taking the unloading rotation speed Rul as the target rotation speed Rt, the unloading operation start pressure Pul is a pressure higher than the full-load operation start pressure Pfl by a predetermined amount, the unloading rotation speed Rul is a rotation speed higher than the minimum rotation speed Rmin by a predetermined amount, and is a rotation speed lower than the full-load rotation speed Rfl by a predetermined amount, wherein the rotation speed control device 10 of the engine-driven compressor is provided with: a pressure detection mechanism 60, detecting the control pressure P;and an electronic control device (controller) 70, which outputs a control signal specifying the target rotational speed Rt to the engine control unit 31 according to the control pressure P detected by the pressure detection mechanism 60, wherein the electronic control device 70 is provided with: a storage mechanism 71, which stores a lower limit unloading rotational speed Rul (L) (as an example, 1300 rpm) and an upper limit unloading rotational speed Rul (H) (as an example, 1350 rpm), and stores an upper limit full load rotational speed Rfl (H) (as an example, 1850 rpm) and a lower limit full load rotational speed Rfl (L) (as an example, 1750 rpm), wherein the lower limit unloading rotational speed The speed Rul (L) is higher than the minimum rotation speed Rmin of the engine 30 by a predetermined margin and is set to a rotation speed below the unload rotation speed Rul, the upper limit unload rotation speed Rul (H) is a rotation speed higher than the lower limit unload rotation speed Rul (L) by a predetermined margin and is set to a rotation speed higher than the unload rotation speed Rul, the upper limit full load rotation speed Rfl (H) is lower than the maximum rotation speed Rmax of the engine 30 by a predetermined margin and is set to a rotation speed higher than the full load rotation speed Rfl, and the lower limit full load rotation speed Rfl (L) is a rotation speed higher than the upper limit full load rotation speed Rfl (H). l(H) is a rotational speed lower than a predetermined amount and is set to a rotational speed lower than the full-load rotational speed Rfl; a rotational speed obtaining mechanism 72, which obtains the rotational speed R of the engine 30; a control signal output mechanism 73, which outputs a control signal to set the unload rotational speed Rul to the target rotational speed Rt when the pressure detection mechanism 60 detects a pressure higher than the unload operation start pressure Pul as the control pressure P, and outputs a control signal to set the full-load rotational speed Rul to the engine control unit 31 when the pressure detection mechanism 60 detects a pressure lower than the full-load operation start pressure Pfl as the control pressure P. The unloading rotation speed increasing mechanism 74 compares the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 with the lower limit unloading rotation speed Ru1(L) stored in the storage mechanism 71 during unloading operation, and when the rotation speed R of the engine 30 is less than the lower limit unloading rotation speed Ru1(L), the control signal output by the control signal output mechanism 73 is changed in such a way that the target rotation speed R1 is gradually increased from the unloading rotation speed Ru1 until the rotation speed R of the engine 30 rises to the lower limit unloading rotation speed Ru1(L);The unloading rotational speed reducing mechanism 75 changes the control signal output by the control signal output mechanism 73 in such a way that the target rotational speed Rt increased by the unloading rotational speed increasing mechanism 74 gradually decreases during the unloading operation, when the rotational speed R of the engine 30 obtained by the rotational speed obtaining mechanism 72 exceeds the upper limit unloading rotational speed Rul (H), until the rotational speed R of the engine 30 drops to the upper limit unloading rotational speed Rul (H); the full load rotational speed reducing mechanism 76 compares the rotational speed R of the engine 30 obtained by the rotational speed obtaining mechanism 72 with the upper limit full load rotational speed Rfl (H) stored in the storage mechanism 71 during the full load operation, and when the rotational speed R of the engine 30 exceeds the upper limit full load rotational speed The control signal output by the control signal output mechanism 73 is changed in such a manner that the target rotation speed Rt gradually decreases from the full load rotation speed Ru1 until the rotation speed R of the engine 30 drops to the upper limit full load rotation speed Rf1(H); and the full load rotation speed increasing mechanism 77, in the full load operation, when the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 is less than the lower limit full load rotation speed Rf1(L), the control signal output by the control signal output mechanism 73 is changed in such a manner that the target rotation speed Rt reduced by the full load rotation speed reducing mechanism 76 gradually increases until the rotation speed R of the engine 30 rises to the lower limit full load rotation speed Rf1(L) (method 13). ;

[0047] In the rotational speed control device 10 of the above-described structure, it is preferred that the reduction speed (D / 2C) at which the unloading rotational speed reduction mechanism 75 reduces the target rotational speed Rt is slower than the increase speed (B / 2A) at which the unloading rotational speed increase mechanism 74 increases the target rotational speed Rt (method 14).

[0048] Similarly, it is preferable that the increase speed (H / 2G) of the full load rotation speed increasing mechanism 77 to increase the target rotation speed Rt is slower than the decrease speed (F / 2E) of the full load rotation speed decreasing mechanism 76 to decrease the target rotation speed Rt (method 15).

[0049] Furthermore, it is preferred that the speed at which the unload rotational speed reducing mechanism 75 reduces the target rotational speed Rt (D / 2C) is slower than the speed at which the unload rotational speed increasing mechanism 74 increases the target rotational speed Rt (B / 2A), and that the speed at which the full load rotational speed increasing mechanism 77 increases the target rotational speed Rt (H / 2G) is slower than the speed at which the full load rotational speed reducing mechanism 76 reduces the target rotational speed Rt (F / 2E) (method 16).

[0050] The electronic control unit 70 is provided with a counting mechanism 78, which counts the number of times n that the rotation speed R of the engine 30 is lower than the lower limit unloading rotation speed Rul (L) during one unloading operation. As the number of counts n of the counting mechanism 78 increases, the unloading rotation speed increasing mechanism 74 is set to slow down the increase speed of the target rotation speed Rt, and / or as the number of counts n of the counting mechanism 78 increases, the unloading rotation speed decreasing mechanism 75 is set to slow down the decrease speed of the target rotation speed Rt (method 17).

[0051] Similarly, the electronic control unit 70 is provided with a counting mechanism 78, which counts the number N of times the rotation speed R of the engine 30 exceeds the upper limit full load rotation speed Rfl (H) during a full load operation. As the number of counts N of the counting mechanism 78 increases, the full load rotation speed reduction mechanism 76 is set to slow down the reduction speed of the target rotation speed Rt, and / or as the number of counts N of the counting mechanism 78 increases, the full load rotation speed increase mechanism 77 is set to slow down the increase speed of the target rotation speed Rt (method 18).

[0052] With the configuration of the present invention described above, according to the rotation speed control method and the rotation speed control device 10 of the engine driven compressor 1 of the present invention, the following remarkable effects can be obtained.

[0053] By setting an allowable range for the target rotational speed Rt and monitoring the rotational speed R of the engine, when the rotational speed R of the engine is less than the lower limit speed of the allowable range or exceeds the upper limit speed of the allowable range, a rotational speed correction is performed to gradually increase or decrease the target rotational speed Rt until the rotational speed R of the engine 30 becomes a rotational speed within the allowable range. Thus, even if the rotational speed R of the engine 30 deviates from the target rotational speed Rt due to changes in the load applied to the engine, the rotational speed R of the engine 30 can be brought close to the target rotational speed Rt.

[0054] In addition, due to individual differences between engines, even when a control signal specifying a common target rotational speed is input, the actual rotational speed of the engine will deviate. Therefore, in the manufacturing process of the engine-driven compressor, it is necessary to manually fine-tune the signal strength of the control signal so that the deviation of the rotational speed relative to the predetermined target rotational speed Rt (for example, the unloaded rotational speed RuI, the fully loaded rotational speed Rfl) is within the allowable error range. However, as described above, the rotational speed control device 10 automatically adjusts the rotational speed of the engine so that the rotational speed of the engine converges within the allowable range for the target rotational speed. Therefore, the aforementioned cumbersome adjustment operation previously performed in the manufacturing process of the engine-driven compressor 1 is not performed, and the product can be launched on the market, which can reduce the manufacturing cost of the engine-driven compressor 1.

[0055] Moreover, unlike the complex control of switching between droop control and isochronous control adopted in the aforementioned patent document 1, in the control of an engine with a droop characteristic, only a simple correction of the control signal is required to achieve the control of the rotational speed. Therefore, when the control method of the present invention is adopted, there is no need to significantly change the rotational speed control device 10 or the control program. Not only can the rotational speed control method of the present invention be applied to an engine-driven compressor at a low cost, but it can also be easily incorporated into an existing engine-driven compressor.

[0056] When such rotational speed control is performed during unloading operation, if the actual rotational speed R of the engine 30 during unloading operation is lower than the lower limit unloading rotational speed (allowable lower limit speed) Rul(L), an unloading rotational speed increase correction is performed to increase the target rotational speed Rt until the actual rotational speed R of the engine 30 rises to the lower limit unloading rotational speed Rul(L), thereby increasing the fuel injection amount of the engine 30. The lower limit unloading rotational speed is set to a rotational speed below the unloading rotational speed Rul which is the target rotational speed Rt. Furthermore, if the rotational speed R of the engine 30 is higher than the upper limit unloading rotational speed (allowable upper limit speed) Rul(H), an unloading rotational speed decrease correction is performed to decrease the target rotational speed Rt until the rotational speed R of the engine 30 drops to the upper limit unloading rotational speed Rul(H). As a result, the rotational speed R of the engine 30 during unloading operation can be gradually stabilized in a manner converging within the rotational speed range between the upper limit unloading rotational speed Rul(H) and the lower limit unloading rotational speed Rul(L) through relatively simple control.

[0057] As a result, by presetting the lower limit unloading rotational speed RuI (L) to a rotational speed that is higher than the minimum rotational speed Rmin of the engine 30 by a necessary margin, it is possible to prevent the rotational speed R of the engine 30 from falling below the minimum rotational speed Rmin and causing the engine 30 to stall, even if the load applied to the engine 30 changes (increases) during unloading operation. On the other hand, it is possible to prevent the fuel consumption during unloading operation from deteriorating due to continued unloading operation when the rotational speed R of the engine 30 exceeds the upper limit unloading rotational speed RuI (H).

[0058] Similarly, if the actual rotational speed R of the engine 30 exceeds the upper limit full load rotational speed (allowable upper limit speed) Rfl(H) during full load operation, a full load rotational speed reduction correction is performed to reduce the target rotational speed Rt until the actual rotational speed R of the engine 30 drops to the upper limit full load rotational speed Rfl(H), thereby reducing the fuel injection amount. The upper limit full load rotational speed is set to a rotational speed greater than the full load rotational speed Rfl serving as the target rotational speed Rt. Furthermore, if the rotational speed R of the engine 30 is lower than the lower limit full load rotational speed (allowable lower limit speed) Rfl(L), a full load rotational speed increase correction is performed to increase the target rotational speed Rt until the rotational speed R of the engine 30 rises to the lower limit full load rotational speed Rfl(L). This allows the rotational speed R of the engine 30 during full load operation to gradually stabilize in a manner that converges within the rotational speed range between the lower limit full load rotational speed Rfl(L) and the upper limit full load rotational speed Rfl(H), thereby preventing the engine from exceeding the maximum rotational speed Rmax and overspeeding.

[0059] In particular, by making the reduction speed (D / 2C) of the target rotational speed Rt by the unloading rotational speed reducing mechanism 75 slower than the increase speed (B / 2A) of the target rotational speed Rt by the unloading rotational speed increasing mechanism 74, the rotational speed R of the engine 30 can be stabilized earlier in a manner converging between the upper limit unloading rotational speed Rul (H) and the lower limit unloading rotational speed Rul (L).

[0060] Similarly, by setting the increase speed (H / 2G) of the target rotational speed Rt by the full load rotational speed increasing mechanism 77 to be slower than the decrease speed (F / 2E) of the target rotational speed Rt by the full load rotational speed decreasing mechanism 76, the rotational speed R of the engine 30 can converge earlier between the lower limit full load rotational speed Rfl (L) and the upper limit full load rotational speed Rfl (H).

[0061] Furthermore, by configuring the system to count the number of times n that the rotational speed R of the engine 30 is lower than the lower limit unloading rotational speed Rul (L) during one unloading operation, as the count number n increases, the unloading rotational speed increasing mechanism 74 increases the target rotational speed Rt at a slower rate, and / or as the count number n increases, the unloading rotational speed decreasing mechanism 75 decreases the target rotational speed Rt at a slower rate, thereby enabling the variation range of the engine rotational speed R to be gradually reduced and the engine rotational speed R to be stabilized at a fixed value earlier.

[0062] Similarly, with respect to the full-load rotational speed reducing mechanism 76 and / or the full-load rotational speed increasing mechanism 77, by slowing down the increase and / or decrease speed of the target rotational speed Rt as the count number N of the number of times the upper limit full-load rotational speed Rfl (H) is exceeded in a full-load operation increases, the fluctuation range of the rotational speed R of the engine 30 can be gradually reduced, thereby stabilizing the rotational speed R of the engine 30 at a fixed value as soon as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a functional block diagram of an engine driven compressor including the rotation speed control device of the present invention. Figure 2 It is a timing chart showing the state of the rotation speed control during unloading operation (Example 1). Figure 3 It is a timing chart showing the state of rotation speed control during full load operation (Example 1). Figure 4 This is a flowchart showing the operation of the rotation speed control method (Example 1) of the present invention. Figure 5 This is a timing chart showing the state of the rotation speed control during unloading operation (Example 2). Figure 6 It is a flowchart showing the operation of the rotation speed control method (Example 2) of the present invention. Figure 7 This is an illustration of an engine-driven compressor. Figure 8 It is an explanatory diagram showing the relationship between the engine rotation speed range (the minimum rotation speed Rmin to the maximum rotation speed Rmax) and the rotation speed range under capacity control (the unloaded rotation speed Rul to the full-loaded rotation speed Rfl). DETAILED DESCRIPTION

[0064] Hereinafter, a configuration example of the rotation speed control device 10 for the engine driven compressor 1 according to the present invention will be described with reference to the drawings.

[0065] In addition, in the following description, the case where the rotational speed control device 10 of the present invention is set to perform both speed control during unloading operation and speed control during full load operation is described, but the rotational speed control device 10 of the present invention can also be configured to perform only one of the speed control during unloading operation and the speed control during full load operation.

[0066] In this case, in the following configuration, the configuration for the other speed control may be omitted as necessary.

[0067] (Overall structure of engine-driven compressor) Figure 1 The overall structure of an engine driven compressor including the rotation speed control device 10 of the present invention is shown.

[0068] Figure 1 The engine driven compressor 1 shown includes an oil-cooled compressor body 20 , an engine 30 that drives the compressor body 20 , and a receiving container 40 that introduces compressed gas discharged from the compressor body 2 together with lubricating oil.

[0069] An unloading valve 21 for opening and closing the suction port is provided at the suction port of the compressor body 20, and a control piping 50 for introducing compressed gas in the receiving container 40 into the closed valve pressure receiving chamber 22 of the unloading valve 21 is connected to the suction port of the compressor body 20, and is constructed so that the control piping 50 can be opened and closed by a pressure regulator 51 provided in the control piping 50.

[0070] The pressure regulator 51 is constructed as follows: when the pressure on the primary side of the pressure regulator 51, that is, the pressure on the discharge side of the compressor body 20 (in the illustrated example, the pressure in the receiving container 40) is less than a predetermined pressure, the valve is closed, and the introduction of compressed gas into the closed valve pressure receiving chamber 22 of the unloading valve 21 through the control piping 50 is stopped, and the unloading valve 21 becomes fully open. If the pressure regulator 51 starts to open the control piping 50 as the pressure on the discharge side of the compressor body 20 rises, compressed gas starts to be introduced into the closed valve pressure receiving chamber 22 of the unloading valve 21, and the unloading valve 21 throttles the suction port of the compressor body 20 at an opening corresponding to the introduction amount of compressed gas. If the pressure on the discharge side of the compressor body rises to a pressure above the pressure that makes the pressure regulator 51 fully open, the unloading valve 21 becomes fully closed.

[0071] Therefore, by setting up a pressure detection mechanism (pressure sensor) 60 for detecting the pressure in the control piping 50 on the secondary side of the pressure regulator 51 and detecting the pressure at this position as the control pressure P, the control pressure P can be set as the pressure indicating that the pressure regulator 51 is in a fully closed state (as an example, the case where the gauge pressure is 0 MPa) and the pressure at which the unloading valve 21 fully opens the suction port of the compressor body 20 to start full load operation (full load operation start pressure Pfl), and the control pressure P detected by the pressure detection mechanism 60 can be set as the pressure at which the unloading valve 21 becomes fully closed and the pressure at which the unloading operation with the suction port of the compressor body 20 closed starts (unloading operation start pressure Pul).

[0072] The control pressure P detected by the pressure detection mechanism 60 is sent to an electronic control device (controller) 70 composed of a microcontroller, etc. The electronic control device (controller) 70 that receives the control pressure P from the pressure detection mechanism 60 outputs a control signal indicating a target rotational speed Rt to an engine control unit (hereinafter referred to as "ECU") 31 based on the received control pressure P and the actual rotational speed R of the engine 30 received by an engine control unit (hereinafter referred to as "ECU") 31 provided in the engine 30.

[0073] The ECU 31 , which has received the control signal from the electronic control unit 70 , is configured to control the rotation speed of the engine 30 by realizing a fuel injection amount corresponding to the target rotation speed Rt specified by the control signal.

[0074] Therefore, if Figure 1 As shown in the figure surrounded by a dashed line in FIG. 1 , the rotation speed control device 10 of the engine driven compressor of the present invention is constituted by the pressure detection mechanism 60 , the electronic control device (controller) 70 , and the ECU 31 .

[0075] (Electronic Control Unit (Controller)) In order to implement the rotation speed control of the present invention, as Figure 1 As shown, the aforementioned electronic control device (controller) has a storage device 71 storing predetermined programs, etc., and has a rotation speed acquisition mechanism 72, a control signal output mechanism 73, an unloaded rotation speed increasing mechanism 74, an unloaded rotation speed decreasing mechanism 75, a full load rotation speed decreasing mechanism 76 and a full load rotation speed increasing mechanism 77 which are realized by executing the programs stored in the storage device 71.

[0076] (1) Storage institution The storage means 71 stores the aforementioned necessary programs and the like, and also stores various data used as threshold values ​​and the like when performing the control of the present invention.

[0077] Among them, as data related to the rotation speed, the upper limit full load rotation speed Rfl (H), the full load rotation speed Rfl, the lower limit full load rotation speed Rfl (L), the upper limit unload rotation speed Rul (H), the unload rotation speed Rul and the lower limit unload rotation speed Rul (L) are stored. In addition, it can also further include the maximum rotation speed Rmax and the minimum rotation speed Rmin of the engine.

[0078] The aforementioned full-load rotation speed Rfl is a rotation speed used as the initial target rotation speed Rt when shifting to the full-load operation, and the unload rotation speed Ru1 is a rotation speed used as the initial target rotation speed Rt when shifting to the unload operation.

[0079] The aforementioned upper limit full load rotational speed (allowable upper limit speed) Rfl (H) is a rotational speed that serves as a threshold value for starting the reduction correction of the target rotational speed Rt by the full load rotational speed reduction mechanism 76 described later, and is a rotational speed that is set as a rotational speed that is lower than the maximum rotational speed Rmax of the engine 30 by a necessary margin, and is set to a rotational speed greater than the aforementioned full load rotational speed Rfl. As an example, in the present embodiment, it is set to 1850 rpm.

[0080] In addition, the aforementioned lower limit full load rotational speed (allowable lower limit speed) Rfl (L) is a rotational speed that serves as a threshold for starting the increase correction of the target rotational speed Rt by the full load rotational speed increasing mechanism 77 described later, and is a rotational speed that is a predetermined amount lower than the aforementioned upper limit full load rotational speed Rfl (H), and is set to a rotational speed below the aforementioned full load rotational speed Rfl. As an example, in this embodiment, it is set to 1750 rpm.

[0081] Furthermore, the aforementioned lower limit unloading rotational speed (allowable lower limit speed) Rul (L) is a rotational speed that serves as a threshold value for starting the reduction correction of the target rotational speed Rt by the unloading rotational speed reduction mechanism 74 described later, and is a rotational speed that is set as a rotational speed that is higher than the minimum rotational speed Rmin of the engine by a necessary margin, and is set to a rotational speed below the aforementioned unloading rotational speed Rul, and is set to 1300 rpm as an example in the present embodiment.

[0082] In addition, the aforementioned upper limit unloading rotational speed (allowable upper limit speed) Rul (H) is a rotational speed that serves as a threshold value for starting the reduction correction of the target rotational speed Rt by the unloading rotational speed reduction mechanism 75 described later, and is a rotational speed that is a predetermined amount higher than the aforementioned lower limit unloading rotational speed Rul (L), and is set to a rotational speed greater than the unloading rotational speed Rul. In this embodiment, as an example, it is set to 1350 rpm.

[0083] Furthermore, the storage mechanism 71 stores the full-load operation start pressure Pfl and the unload operation start pressure Pul as reference values ​​related to pressure.

[0084] The full-load operation start pressure Pfl is a threshold pressure for switching the operating state of the engine-driven compressor 1 to full-load operation. If the control pressure P detected by the pressure detection mechanism 60 becomes the full-load operation start pressure Pfl (in this embodiment, the gauge pressure is 0 MPa), the full-load operation starts.

[0085] The unload operation start pressure Pul is a pressure serving as a threshold value when the operation state of the engine driven compressor is switched to the unload operation. When the control pressure P detected by the pressure detection mechanism 60 becomes equal to or higher than the unload operation start pressure Pul, the unload operation is started.

[0086] Furthermore, the storage mechanism 71 stores the signal strength of the control signal corresponding to the unloading rotation speed Rul and the signal strength of the control signal corresponding to the full load rotation speed Rfl, and can pre-store the correspondence between the change in the target rotation speed Rt and the change in the control pressure P between the unloading operation start pressure Pul and the full load operation start pressure Pfl, as well as the correspondence between the target rotation speed Rt and the signal strength of the control signal.

[0087] (2) Rotation speed acquisition mechanism The rotation speed acquisition unit 72 acquires the actual rotation speed R of the engine 30 , and in the illustrated embodiment, receives a rotation speed signal from the ECU 31 , thereby being able to acquire the real-time rotation speed R of the engine 30 .

[0088] In place of the illustrated configuration, for example, a rotation speed sensor for detecting the rotation speed of the engine 30 may be provided independently of the ECU 31 , and the actual rotation speed R of the engine 30 may be acquired based on a detection signal from the rotation speed sensor.

[0089] (3) Control signal output mechanism When the control pressure P detected by the pressure detection mechanism 60 is greater than the predetermined unloading operation start pressure Pul, the control signal output mechanism 73 outputs a control signal to the ECU 31 to set the unloading rotation speed Rul to the target rotation speed Rt. Furthermore, when the control pressure P detected by the pressure detection mechanism is the full-load operation start pressure Pfl, the control signal output mechanism 73 outputs a control signal to the ECU to set the full-load rotation speed Rfl to the target rotation speed.

[0090] In addition, in the following description, an example is given of a case in which the target rotational speed Rt indicated to ECU31 increases due to an increase in the signal strength (voltage value) of the control signal output by the control signal output mechanism 73, and the target rotational speed Rt indicated to ECU31 decreases due to a decrease in the signal strength of the control signal, but the present invention is not limited to this example, and the opposite may be true, in which the target rotational speed Rt increases due to a decrease in the signal strength, and the target rotational speed Rt decreases due to an increase in the signal strength.

[0091] In addition, in the present embodiment, a structure is adopted in which the pressure in the control piping 50 on the secondary side of the pressure regulator 51 is detected as the control pressure P and the rotation speed of the engine 30 is controlled based on the control pressure P, but it is also possible to replace this structure with a structure in which the pressure in the receiving container 40 and the pressure in the supply piping 55 from the receiving container 40 to the consumption side are detected as the control pressure P and the rotation speed R of the engine 30 is controlled.

[0092] (4) Unloading rotation speed increasing mechanism (rotation speed correction mechanism) During the unloading operation, the unloading rotational speed increasing mechanism 74 compares the rotational speed R of the engine 30 obtained by the rotational speed obtaining mechanism 72 with the lower limit unloading rotational speed Rul(L) stored in the storage mechanism 71. When the rotational speed R of the engine 30 is less than the lower limit unloading rotational speed Rul(L), the control signal output by the control signal output mechanism 73 is corrected to change in the direction of increasing the target rotational speed Rt until the rotational speed R of the engine 30 rises to the lower limit unloading rotational speed Rul(L).

[0093] In this embodiment, the structure is as follows: by increasing the signal strength of the control signal (control voltage) output by the control signal output mechanism 73, the target rotation speed Rt specified by the ECU 31 is increased (the fuel injection amount is increased), and by reducing the signal strength of the control signal (control voltage), the target rotation speed Rt specified by the ECU 31 is reduced (the fuel injection amount is reduced). Figure 2 In the embodiment shown, the following structure is adopted: every predetermined addition processing time 2A, the signal strength is increased stepwise by a predetermined addition amplitude B until the engine rotation speed R obtained by the rotation speed acquisition mechanism 72 increases to the lower limit unloading rotation speed Rul (L) (refer to Figure 2 (changes in the control signal of T6-T7 in the example).

[0094] In addition, in the embodiment, the signal strength of the control signal is set to be Figure 2 Although the control signal changes in stages as shown, it is also possible to change the control signal steplessly (linearly) instead of this configuration.

[0095] (5) Unloading rotation speed reduction mechanism (rotation speed correction mechanism) When the rotation speed R of the engine 30 exceeds the upper limit unloading rotation speed Rul (H) as a result of the signal strength of the control signal being changed by the aforementioned unloading rotation speed increasing mechanism 74 in the direction of increasing the target rotation speed Rt, the unloading rotation speed decreasing mechanism 75 changes the signal strength of the control signal increased by the unloading rotation speed increasing mechanism 74 in the direction of decreasing the target rotation speed Rt (in the direction of reducing the signal strength) until the rotation speed R of the engine 30 drops to the upper limit unloading rotation speed Rul (H).

[0096] exist Figure 2 In the illustrated embodiment, the signal strength is reduced in stages at a predetermined subtraction amplitude D every predetermined subtraction processing time 2C until the rotational speed R of the engine 30 obtained by the rotational speed acquisition mechanism 72 drops to the upper limit unloading rotational speed Rul (H), but this structure may be replaced by a stepless (linear) change in the control signal.

[0097] like Figure 2 As shown, the speed of decrease (D / 2C) of the signal strength of the control signal reduced by the unloading rotation speed reducing mechanism 75 is preferably slower than the speed of increase (B / 2A) of the signal strength of the control signal increased by the unloading rotation speed increasing mechanism 74. Such a speed reduction can be achieved by setting the processing time of the speed of decrease (D / 2C) of the signal strength of the control signal reduced by the unloading rotation speed reducing mechanism 75 to be longer than the processing time of the speed of increase (B / 2A) of the signal strength of the control signal increased by the unloading rotation speed increasing mechanism 74 (2A<2C), or by setting the subtraction amplitude D to be smaller than the addition amplitude B (B>D), or by both.

[0098] (6) Full load rotation speed reduction mechanism (rotation speed correction mechanism) During full-load operation, the full-load rotational speed reducing mechanism 76 compares the rotational speed R of the engine 30 obtained by the rotational speed obtaining mechanism 72 with the upper limit full-load rotational speed Rfl (H) stored in the storage mechanism 71. When the rotational speed R of the engine 30 exceeds the upper limit full-load rotational speed Rfl (H), the signal strength of the control signal output by the control signal output mechanism 73 is changed in the direction of reducing the target rotational speed Rt specified for the ECU 31 until the rotational speed R of the engine 30 drops to the upper limit full-load rotational speed Rfl (H).

[0099] exist Figure 3In the illustrated embodiment, the signal strength of the control signal is reduced in stages at a predetermined subtraction amplitude F every predetermined subtraction processing time 2E until the rotational speed R of the engine 30 obtained by the rotational speed acquisition mechanism 72 drops to the upper limit full load rotational speed Rfl (H), but this structure may also be replaced by a stepless (linear) reduction of the control signal.

[0100] (7) Full load rotation speed increasing mechanism (rotation speed correction mechanism) When the result of the control signal being corrected by the aforementioned full-load rotational speed reducing mechanism 76 in the direction of reducing the target rotational speed Rt is that the rotational speed R of the engine 30 is lower than the lower limit full-load rotational speed Rfl(L), the full-load rotational speed increasing mechanism 77 increases the signal strength of the control signal after being reduced by the full-load rotational speed reducing mechanism 76 until the rotational speed R of the engine 30 rises to the lower limit full-load rotational speed Rfl(L).

[0101] exist Figure 3 In the embodiment shown, the signal strength is increased step by step at a predetermined addition amplitude H every predetermined addition time 2G until the engine rotational speed R obtained by the rotational speed acquisition mechanism 72 rises to the lower limit full load rotational speed Rfl (L), but this structure can also be replaced by setting the control signal change to be stepless (linear).

[0102] The increasing speed (H / 2G) of the signal strength of the control signal increased by the full-load rotation speed increasing mechanism 77 is preferably slower than the decreasing speed (F / 2E) of the signal strength of the control signal reduced by the full-load rotation speed reducing mechanism 76. Such a speed reduction can be achieved by setting the processing time in the increasing speed (H / 2G) of the signal strength of the control signal increased by the full-load rotation speed increasing mechanism 77 to be longer than the processing time in the decreasing speed (F / 2E) of the signal strength of the control signal reduced by the full-load rotation speed reducing mechanism 76 (2E<2G), or by setting the addition amplitude H to be smaller than the subtraction amplitude F (F>H), or by both.

[0103] (Action, etc.) Reference Figure 2 to Figure 4 The operation of the rotation speed control device 10 in the engine driven compressor 1 of the present invention described above will be described.

[0104] If the state of compressed gas consumption on the consumption side is changed to stopping the compressed gas consumption ( Figure 2 The control pressure P starts to rise and after reaching the predetermined unloading operation starting pressure Pul ( Figure 2 It exceeds the unloading operation starting pressure Pul and rises further.

[0105] The control signal output mechanism 73 of the electronic control device (controller) 70 reduces the signal strength of the control signal output to the ECU 31 of the engine 30 according to the corresponding relationship stored in the storage mechanism 71 in accordance with the increase of the control pressure P. If the control pressure P becomes equal to or higher than the unloading operation start pressure Pul (P≥Pul) ( Figure 4 If the answer of S1 is “Yes”), the signal strength of the control signal is reduced to the signal strength corresponding to the unloading rotation speed Ru1 and maintained fixed ( Figure 2 of T2).

[0106] After the control signal output mechanism 73 starts to output a control signal of a fixed strength corresponding to the unloading rotation speed Ru1, the rise of the control pressure P stops with a delay and stabilizes ( Figure 2 The engine speed R decreases further and stops with a delay and stabilizes at a fixed speed ( Figure 2 T4).

[0107] Thus, in the state of unloading operation, for example, if a small amount of compressed gas ( Figure 2 The discharge side pressure of the compressor body 20 decreases, and the load applied to the engine 30 increases. However, since the control pressure P is still maintained at a pressure higher than the unloading operation start pressure Pul, the control signal output mechanism 73 outputs the control signal to the ECU 31 to maintain a control signal with a fixed signal strength corresponding to the unloading rotation speed Rul ( Figure 2 T5-T6).

[0108] As a result, the ECU 31 maintains the fuel injection amount of the engine 30 at a fixed amount, while the load applied to the engine 30 increases, so the engine 30 starts to decelerate ( Figure 2 T5).

[0109] If the rotation speed R of the engine 30 decreases to a value lower than the lower limit unload rotation speed Rul(L)(R <Rul(L))( Figure 2 T6 Figure 4 If the answer of S2 is "Yes", the unloading rotation speed increasing mechanism 74 of the electronic control device 70 is started to perform a process of increasing the signal strength of the control signal output by the control signal output mechanism 73 by a predetermined addition amplitude B ( Figure 2 T6 Figure 4 S3).

[0110] Even if the signal strength is increased by the addition amplitude B and the predetermined addition processing time 2A ( Figure 4In the case where the engine 30 rotation speed R does not become equal to or higher than the lower limit unload rotation speed Rul(L) (R ≥ Rul(L)), Figure 4 The unloading rotation speed increasing mechanism 74 increases the signal strength again by the addition amplitude B, and this process is repeated ( Figure 2 T6-T7), until the engine rotation speed R obtained by the rotation speed acquisition mechanism 72 becomes greater than the lower limit unload rotation speed Rul(L) (R ≥ Rul(L)) ( Figure 4 S5 "yes").

[0111] In this way, by increasing the signal strength of the control signal, the rotation speed R of the engine 30 exceeds the lower limit unload rotation speed Ru1(L) ( Figure 4 Then, if the rotation speed R further increases and exceeds the upper limit unloading rotation speed Ru1(H), ( Figure 2 T8 Figure 4 (“Yes” in S6 ), the unloading rotation speed reducing mechanism 75 of the electronic control device 70 is started.

[0112] If the unloading rotation speed reducing mechanism 75 is activated, the unloading rotation speed reducing mechanism 75 performs a process of reducing the signal strength of the control signal output by the control signal output mechanism 73 by a predetermined subtraction amplitude D ( Figure 2 T8 Figure 4 S7).

[0113] Even if the signal strength is reduced by the subtraction amplitude D and the predetermined subtraction processing time 2C ( Figure 4 If the engine 30 rotation speed R does not become lower than the upper limit unloading rotation speed Ru1(H) ( Figure 4 The unloading rotation speed reducing mechanism 75 reduces the signal strength by the subtraction amplitude D again, and this process is repeated ( Figure 2 T8-T9), until the engine rotation speed R obtained by the rotation speed acquisition mechanism 72 becomes lower than the upper limit unloading rotation speed Ru1(H) ( Figure 4 S9's "yes").

[0114] During the period when the control pressure P becomes a pressure higher than the unloading operation start pressure Pul ( Figure 4S1 is "Yes", that is, in the unloading operation, by repeatedly performing the aforementioned processing, even if the rotation speed R of the engine 30 during the unloading operation changes due to the change of the load applied to the engine 30, by gradually stabilizing the rotation speed R of the engine 30 in a manner converging between the upper limit unloading rotation speed Rul (H) and the lower limit unloading rotation speed Rul (L), it is possible to appropriately prevent the rotation speed R of the engine 30 during the unloading operation from decreasing below the minimum rotation speed Rmin and causing the engine 30 to stall.

[0115] In addition, the correction of the signal strength of the control signal by the unloading rotation speed increasing mechanism 74 and the unloading rotation speed decreasing mechanism 75 during the unloading operation and the correction of the target rotation speed Rt accompanying this, together with the control pressure P becoming a pressure less than the unloading operation starting pressure Pul ( Figure 4 The unloading operation is terminated by "No" in S1.

[0116] On the other hand, if the control pressure P becomes lower than the unloading operation start pressure Pul due to the consumption of compressed gas on the consumption side, etc. ( Figure 4 The “No” of S1) further increases the consumption of compressed gas ( Figure 3 When the discharge pressure of the compressor body 20 decreases to a value lower than the operation start pressure of the pressure regulator 51, the pressure regulator 51 is closed and the control pressure P decreases to a predetermined full load operation start pressure Pfl (in the illustrated embodiment, the gauge pressure is 0 MPa) ( Figure 3 T11).

[0117] The control signal output mechanism 73 of the electronic control device (controller) 70 increases the signal strength of the control signal output to the ECU 31 of the engine 30 in accordance with the correspondence relationship stored in the storage mechanism 71 in accordance with the decrease in the control pressure P. If the control pressure P reaches the full load operation start pressure Pfl (0 MPa) ( Figure 4 If the signal strength of the control signal output to the ECU 31 is increased to the signal strength corresponding to the full load rotation speed Rfl, the signal strength of the control signal is maintained constant ( Figure 3 T11).

[0118] After the full load operation is started, the increase in the rotation speed R of the engine 30 is delayed and stopped, and the engine 30 is stabilized at a fixed rotation speed R (0 MPa). Figure 3 T12).

[0119] In this way, if the consumption of compressed gas on the consumption side is further increased in the state of full-load operation, the discharge side pressure of the compressor body 20 (the pressure in the receiving container 40) decreases, and the load applied to the engine 30 decreases. However, since the control pressure P is still maintained at the full-load operation start pressure Pul (0 MPa), the control signal output by the control signal output mechanism 73 to the ECU 31 is maintained as a control signal with a fixed signal strength corresponding to the full-load rotation speed Rfl ( Figure 3 T13-T14).

[0120] As a result, the ECU 31 maintains the fuel injection amount to the engine constant, and on the other hand, the load applied to the engine is reduced, so the engine starts to accelerate ( Figure 3 T13).

[0121] If the engine speed R exceeds the upper limit full load speed Rfl(H) due to the acceleration ( Figure 3 T14, Figure 4 If the answer of S11 is "Yes", the full-load rotation speed reduction mechanism 76 of the electronic control device 70 is started to execute the processing of reducing the signal strength of the control signal output by the control signal output mechanism 73 to the ECU 31 by a predetermined subtraction amplitude F ( Figure 3 T1 Figure 4 of S12).

[0122] Even if the signal strength is reduced by the subtraction amplitude F and the predetermined subtraction processing time 2E ( Figure 4 If the engine 30 rotation speed R does not become lower than the upper limit full load rotation speed Rfl (H) ( Figure 4 The full load rotation speed reduction mechanism 76 reduces the signal strength by the subtraction amplitude F again, and this process is repeated ( Figure 3 T14-T15), until the engine rotation speed R obtained by the rotation speed obtaining mechanism 72 becomes lower than the upper limit full load rotation speed Rfl (H) ( Figure 4 of S14 (“Yes”).

[0123] In this way, by making correction to reduce the signal strength of the control signal output by the control signal output means 73, the rotation speed R of the engine 30 becomes equal to or less than the upper limit full load rotation speed Rfl (H) ( Figure 4 ) but if the rotation speed further decreases thereafter and falls below the lower limit full load rotation speed Rfl(L) ( Figure 3 T16, Figure 4 (“Yes” in S15 ), the full-load rotation speed increasing mechanism 77 of the electronic control device 70 is started.

[0124] By activating the full-load rotation speed increasing mechanism 77, the full-load rotation speed increasing mechanism 77 performs a correction (increasing the signal strength of the control signal output by the control signal output mechanism 73 to the ECU 31 by a predetermined addition width H) Figure 4 S16).

[0125] Even if the signal strength is increased by the addition amplitude H and the predetermined addition processing time 2G ( Figure 4 If the engine 30 rotation speed R does not rise to or above the lower limit full load rotation speed Rfl(L) ( Figure 4 The full load rotation speed increasing mechanism 77 increases the signal strength by the addition amplitude H again, and this process is repeated ( Figure 3 T16-T17) until the engine rotation speed R obtained by the rotation speed obtaining mechanism 72 becomes greater than the lower limit full load rotation speed Rfl (L) ( Figure 4 S18 of “Yes”).

[0126] By repeating this process, even if the rotation speed R of the engine 30 during full load operation changes due to changes in the load applied to the engine 30, the rotation speed R of the engine 30 is gradually converged between the lower limit full load rotation speed Rfl (L) and the upper limit full load rotation speed Rfl (H), thereby appropriately preventing the rotation speed of the engine 30 from over-revolution during full load operation.

[0127] During the period when the control pressure P reaches the full load operation start pressure Pfl (0 MPa) ( Figure 4 If the control pressure P exceeds the full load operation start pressure Pfl ( Figure 4 If the full load operation is ended by "No" in S10 of S10), the processing is ended and the speed control under the normal capacity control is restored.

[0128] (Variation) (Example 2) Above, in reference Figure 2 to Figure 4 In the described embodiment (Example 1), the following structure is adopted: regardless of the number of times the rotation speed R of the engine 30 is lower than the lower limit unloading rotation speed Rul (L), the unloading rotation speed increasing mechanism 74 always increases the signal strength of the control signal at a fixed increasing speed (B / 2A), and the unloading rotation speed decreasing mechanism 75 reduces the signal strength of the control signal at a fixed decreasing speed (D / 2C).

[0129] In contrast, in the embodiment (Example 2) described below, a counting mechanism 78 (see Figure 1 ), the number of times n that the unloading rotation speed is lower than the lower limit Rul (L) during the unloading operation is counted, and as the count number n increases, the speed at which the signal strength of the control signal of the unloading rotation speed increasing mechanism 74 increases becomes slower, and the speed at which the signal strength of the control signal of the unloading rotation speed decreasing mechanism 75 decreases becomes slower.

[0130] As an example, in Figure 5 In the embodiment shown, the increasing speed of the signal strength of the control signal of the unloading rotation speed increasing mechanism 74 is calculated based on the following formula, and the increasing speed is reduced every time the number of times n below the lower limit speed increases. (B / Xn) / 2AXn B is the basic addition amplitude, 2A is the basic addition processing time, X is a constant, and n is the number of times the unloading rotation speed falls below the lower limit.

[0131] In addition, Figure 5 In the embodiment shown, the reduction speed of the signal strength of the control signal by the unloading rotation speed reduction mechanism 75 is calculated based on the following formula, and the reduction speed is reduced every time the number of times n that the unloading rotation speed falls below the lower limit Rul (L) increases. (D / Yn) / 2CYn D is the basic subtraction amplitude, 2C is the basic subtraction processing time, Y is a constant, and n is the number of times the unloading rotation speed is lower than the lower limit.

[0132] In addition, in the present embodiment (Example 2), the aforementioned counting mechanism 78 is also made to count the number of times N that the upper limit full load rotational speed Rfu (H) is exceeded during full load operation. As the count number N increases, the speed at which the full load rotational speed reducing mechanism 76 reduces the signal strength of the control signal is slowed down, and the speed at which the full load rotational speed increasing mechanism 77 increases the signal strength of the control signal is slowed down.

[0133] As an example, in this embodiment, the speed at which the full-load rotation speed reduction mechanism 76 reduces the signal strength of the control signal is calculated based on the following formula, and the speed is reduced every time the number of times N exceeding the upper limit full-load rotation speed increases. (F / XN) / 2EXN F is the basic subtraction amplitude, 2E is the basic subtraction processing time, X is a constant, and N is the number of times the upper limit full load rotation speed is exceeded.

[0134] In addition, in this embodiment, the increasing speed of the signal strength of the control signal of the full-load rotation speed increasing mechanism 77 is calculated based on the following formula, and the increasing speed is slowed down every time the number of times N exceeding the upper limit full-load rotation speed Rfl (H) increases. (H / YN) / 2GYN H is the basic addition amplitude, 2G is the basic addition processing time, Y is a constant, and N is the number of times the upper limit full load rotation speed is exceeded.

[0135] In addition, Figure 5 In the embodiment shown (Example 2), whenever the number n of times the unloading rotation speed falls below the lower limit Rul (L) increases, the rate of increase of the signal strength of the control signal by the unloading rotation speed increasing mechanism 74 is slowed down not only by reducing the addition amplitude (B / Xn) of the control signal but also by increasing the addition processing time (2AXn). However, this structure may be replaced by only reducing the addition amplitude (B / Xn) of the control signal and increasing the addition processing time (2AXn) to slow down the increase rate.

[0136] Similarly, in the present embodiment (Example 2), whenever the number of times n that the unloading rotation speed falls below the lower limit Rul (L) increases, the signal strength of the control signal in the unloading rotation speed reduction mechanism 75 may be reduced by only reducing the subtraction amplitude (D / Yn) of the control signal and increasing the subtraction processing time (2CYn).

[0137] Furthermore, in the full-load rotation speed reducing mechanism 76, the speed of decrease in the signal strength of the control signal can be reduced relative to an increase in the number N of times the upper limit full-load rotation speed Rfl (H) is exceeded by only either a decrease in the subtraction amplitude (F / XN) or an increase in the subtraction processing time (2EXN), and the speed of increase in the signal strength of the control signal can be reduced relative to an increase in the number N of times the upper limit full-load rotation speed Rfl (H) is exceeded by only either a decrease in the addition amplitude (H / YN) or an increase in the addition processing time (2GYN) by the full-load rotation speed increasing mechanism 77.

[0138] (Action, etc.) Reference Figure 5 and Figure 6 The operation of the rotation speed control device 10 of the present embodiment (Embodiment 2) described above will be described.

[0139] If the state of compressed gas consumption on the consumption side is changed to stopping the compressed gas consumption ( Figure 5 The control pressure P starts to rise and after reaching the predetermined unloading operation starting pressure Pul ( Figure 5It exceeds the unloading operation starting pressure Pul and rises further.

[0140] The control signal output mechanism 73 of the electronic control device (controller) 70 reduces the signal strength of the control signal output to the ECU 31 of the engine 30 according to the corresponding relationship stored in the storage mechanism in accordance with the increase of the control pressure P. If the control pressure P becomes higher than the unloading operation start pressure Pul ( Figure 6 If the answer of S1 is “Yes”), the signal strength of the control signal is reduced to the signal strength corresponding to the unloading rotation speed Ru1 and maintained fixed ( Figure 5 of T2).

[0141] After the control signal output mechanism 73 starts to output a control signal of a fixed strength corresponding to the unloading rotation speed Ru1, the rise of the control pressure P stops with a delay and stabilizes ( Figure 5 The decrease in the rotation speed R of the engine 30 is further delayed and stops, stabilizing at a fixed rotation speed ( Figure 5 T4).

[0142] Thus, in the state of unloading operation, for example, if a small amount of compressed gas ( Figure 5 The discharge side pressure of the compressor body 20 is slightly reduced, and the load applied to the engine 30 is increased. However, since the control pressure P is still maintained at a pressure higher than the unloading operation start pressure Pul, the control signal output mechanism 73 outputs the control signal to the ECU 31 at a fixed signal strength corresponding to the unloading rotation speed Rul ( Figure 5 T5-T6).

[0143] As a result, the ECU 31 maintains the fuel injection amount for the engine 30 constant, while the load applied to the engine 30 increases, so the engine 30 starts to decelerate ( Figure 5 T5).

[0144] If the rotation speed R of the engine 30 decreases to or below the lower limit unload rotation speed Ru1(L) ( Figure 5 T6 Figure 6 If the answer of S2 is “Yes”), the counting mechanism 78 of the electronic control device 70 counts the number of times n when the unloading rotation speed is reduced to the lower limit Rul (L) and updates the count number n ( Figure 6 S3), and the unloading rotation speed increasing mechanism 74 is started to execute the processing (S4) of increasing the signal strength of the control signal output by the control signal output mechanism 73 to the ECU 31 by a predetermined addition amplitude (B / Xn) corresponding to the count number n. Figure 5 T6 Figure 6 S4).

[0145] Even if the signal strength is increased by the addition width (B / Xn) and a predetermined addition processing time (2AXn) corresponding to the count number n has passed ( Figure 6 If the engine 30 rotation speed R does not become higher than the lower limit unload rotation speed Ru1(L) ( Figure 6 The signal strength is increased again by the addition amplitude (B / Xn), and this process is repeated until the engine rotation speed R obtained by the rotation speed acquisition mechanism 72 becomes greater than the lower limit unloading rotation speed Ru1(L) ( Figure 6 S6's "yes")( Figure 5 of T6-T7).

[0146] In this way, by increasing the signal strength of the control signal, the rotation speed R of the engine 30 not only exceeds the lower limit unload rotation speed Rul (L) ( Figure 6 If the unloading rotation speed further increases and exceeds the upper limit unloading rotation speed Ru1(H), then the unloading rotation speed will be increased to a value lower than the upper limit unloading rotation speed Ru1(H). Figure 5 T8 Figure 6 If the answer of S7 is "Yes", the unloading rotation speed reducing mechanism 75 of the electronic control device 70 is started, and the signal strength of the control signal is reduced by a predetermined subtraction amplitude (D / Yn) according to the number of times n that the unloading rotation speed falls below the lower limit Rul (L) counted by the counting mechanism 78 ( Figure 6 S8).

[0147] Even if the signal strength is reduced by the subtraction width (D / Yn) and a predetermined subtraction processing time (2CYn) corresponding to the count number n has passed ( Figure 6 If the engine 30 rotation speed R does not drop below the upper limit unloading rotation speed Ru1(H) ( Figure 6 The signal strength is reduced again by the subtraction amplitude (D / Yn), and this process is repeated ( Figure 5 T8-T9), until the rotation speed R of the engine 30 obtained by the rotation speed obtaining mechanism 72 decreases to below the upper limit unloading rotation speed Ru1(H) ( Figure 6 S10's "yes").

[0148] So, in Figure 5In the illustrated embodiment, the addition amplitude is set to "B / Xn" and the unloading rotation speed increasing mechanism 74 performs an increase correction, so that the addition amplitude when the count number n is 2 (n=2) is 1 / 2 of the addition amplitude when the count number n is 1 (n=1) for the number of times below the lower limit unloading rotation speed Rul (L), and the addition processing time is set to "2AXn", so that the addition processing time when the count number n is 2 (n=2) is twice the addition processing time when the count number n is 1 (n=1).

[0149] Similarly, in Figure 5 In the illustrated embodiment, the subtraction amplitude is set to "D / Yn" and the unloading rotation speed reduction mechanism 75 performs a reduction correction, so that the subtraction amplitude when the count number n is 2 (n=2) is 1 / 2 of the subtraction amplitude when the count number n is 1 (n=1) for the number of times below the lower limit unloading rotation speed Rul (L), and the subtraction processing time is set to "2CYn", so that the subtraction processing time when the count number n is 2 (n=2) is twice the subtraction processing time when the count number n is 1 (n=1).

[0150] As a result, the rotation speed R of the engine 30 can be brought within the speed range between the lower limit unload rotation speed Rul (L) and the upper limit unload rotation speed Rul (H) in a shorter time.

[0151] In addition, the rotational speed control performed by the rotational speed control device 10 of the present embodiment (Example 2) during full-load operation also counts the number of times N that the rotational speed R of the engine 30 exceeds the upper limit full-load rotational speed Rfl (H) during full-load operation. As the count number N increases, the reduction speed of the signal strength reduced by the full-load rotational speed reduction mechanism 76 and the increase speed of the signal strength increased by the full-load rotational speed increase mechanism 77 are reduced in the same manner as during unloading operation, and therefore detailed description of the actions during full-load operation is omitted. Description of Reference Numerals

[0152] 1.100 Engine driven compressor 10 Rotation speed control device 20, 120 compressor body 21, 121 Unloading valve 22, 122 Closed valve pressure chamber 30, 130 engine 31, 131 Engine Control Unit (ECU) 40, 140 receiving container 50, 150 control piping 51, 151 Pressure regulator 55 Supply piping 60, 160 pressure detection mechanism (pressure sensor) 70, 170 Electronic control device (controller) 71 Storage Institutions 72 Rotation speed acquisition mechanism 73 Control signal output mechanism 74 Unloading rotation speed increasing mechanism 75 Unloading rotation speed reduction mechanism 76 Full load rotation speed reduction mechanism 77 Full load rotation speed increase mechanism 78 counting mechanism 180 Coupling 200 Capacity control device R Engine rotation speed Rul Unload rotation speed Rul(L) Lower limit unloading rotation speed (allowable lower limit speed) Rul(H) Upper limit unloading rotation speed (allowable upper limit speed) Rfl full load rotation speed Rfl(L) lower limit full load rotation speed (allowable lower limit speed) Rfl(H) Maximum full load rotation speed (allowable upper limit speed) Rt Target rotation speed Rmax Maximum engine speed Rmin minimum engine rotation speed P Control pressure Pul Unloading operation start pressure Pfl Full load operation start pressure.

Claims

1. A method for controlling the rotation speed of an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit for realizing a fuel injection amount corresponding to a specified target rotation speed, and a rotation speed control method for the engine driven compressor specifies the target rotation speed corresponding to a control pressure as a pressure on a discharge side of the compressor body based on a predetermined correspondence relationship and drives the engine. The rotation speed control method of the engine driven compressor is characterized in that: setting a predetermined permissible range for the target rotation speed, monitoring the rotational speed of the engine, When the rotation speed of the engine is lower than the lower limit speed of the allowable range for the specified target rotation speed or exceeds the upper limit speed of the allowable range, a rotation speed correction is performed to gradually increase or decrease the specified target rotation speed until the rotation speed of the engine becomes a rotation speed within the allowable range.

2. A method for controlling the rotation speed of an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit that realizes a fuel injection amount corresponding to a specified target rotational speed and has a predetermined minimum rotational speed, a rotational speed control method for the engine driven compressor closes a suction port of the compressor body according to a change in a control pressure as a pressure on a discharge side of the compressor body when the control pressure is equal to or higher than a predetermined unload operation start pressure, and performs an unload operation of driving the engine with an unloaded rotational speed as the target rotational speed, the unloaded rotational speed being a rotational speed that is higher than the minimum rotational speed by a predetermined amount, The rotation speed control method of the engine driven compressor is characterized in that: a lower limit unloading rotational speed and an upper limit unloading rotational speed, wherein the lower limit unloading rotational speed is a rotational speed which is higher than the lowest rotational speed of the engine by a predetermined margin and is lower than the unloading rotational speed, and the upper limit unloading rotational speed is a rotational speed which is higher than the lower limit unloading rotational speed by a predetermined amount and is higher than the unloading rotational speed, During the unloading operation, monitoring the rotation speed of the engine, Repeat the unloading rotation speed increase correction and unloading rotation speed decrease correction. The unload rotation speed increase correction gradually increases the target rotation speed from the unload rotation speed until the rotation speed of the engine rises to the lower limit unload rotation speed when the rotation speed of the engine is less than the lower limit unload rotation speed. The unload rotation speed reduction correction gradually reduces the target rotation speed increased by the unload rotation speed increase correction until the engine rotation speed drops to the upper limit unload rotation speed when the engine rotation speed exceeds the upper limit unload rotation speed.

3. A method for controlling the rotation speed of an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit that realizes a fuel injection amount corresponding to a specified target rotational speed and has a predetermined maximum rotational speed, and a rotational speed control method for the engine driven compressor, based on a change in a control pressure as a pressure on a discharge side of the compressor body, when the control pressure is below a predetermined full load operation start pressure, causes a suction port of the compressor body to be fully opened, and performs full load operation of the engine by using a full load rotational speed as the target rotational speed, the full load rotational speed being a rotational speed lower than the maximum rotational speed by a predetermined amount, The rotation speed control method of the engine driven compressor is characterized in that: an upper limit full load rotational speed and a lower limit full load rotational speed, wherein the upper limit full load rotational speed is a rotational speed lower than the maximum rotational speed of the engine by a predetermined margin and higher than the full load rotational speed, and the lower limit full load rotational speed is a rotational speed lower than the upper limit full load rotational speed by a predetermined amount and lower than the full load rotational speed, During the full-load operation, monitoring the rotation speed of the engine, Repeat the full load rotation speed reduction correction and full load rotation speed increase correction. The full-load rotation speed reduction correction gradually reduces the target rotation speed from the full-load rotation speed until the rotation speed of the engine drops to the upper limit full-load rotation speed when the rotation speed of the engine exceeds the upper limit full-load rotation speed. The full load rotation speed increase correction gradually increases the target rotation speed reduced by the full load rotation speed reduction correction until the engine rotation speed reaches the lower full load rotation speed limit when the engine rotation speed is lower than the lower full load rotation speed limit.

4. A method for controlling the rotation speed of an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit for realizing a fuel injection amount corresponding to a specified target rotational speed and has a predetermined maximum rotational speed and a minimum rotational speed. In a rotational speed control method for the engine driven compressor, based on a change in a control pressure as a pressure on a discharge side of the compressor body, when the control pressure is below a predetermined full load operation start pressure, a suction port of the compressor body is fully opened, and a full load operation of the engine is performed with a full load rotational speed as the target rotational speed, the full load rotational speed being a rotational speed lower than the maximum rotational speed by a predetermined amount, and when the control pressure is above an unload operation start pressure, the suction port of the compressor body is closed, and an unload operation of the engine is performed with an unload rotational speed as the target rotational speed, the unload operation start pressure being a pressure higher than the full load operation start pressure by a predetermined amount, the unload rotational speed being a rotational speed higher than the minimum rotational speed by a predetermined amount, and being a rotational speed lower than the full load rotational speed by a predetermined amount, The rotation speed control method of the engine driven compressor is characterized in that: a lower limit unloading rotational speed and an upper limit unloading rotational speed, wherein the lower limit unloading rotational speed is a rotational speed which is higher than the lowest rotational speed of the engine by a predetermined margin and is lower than the unloading rotational speed, and the upper limit unloading rotational speed is a rotational speed which is higher than the lower limit unloading rotational speed by a predetermined amount and is higher than the unloading rotational speed, and setting an upper full-load rotational speed limit and a lower full-load rotational speed limit, wherein the upper full-load rotational speed limit is a rotational speed that is lower than the maximum rotational speed of the engine by a predetermined margin and is higher than the full-load rotational speed, and the lower full-load rotational speed limit is a rotational speed that is lower than the upper full-load rotational speed by a predetermined amount and is lower than the full-load rotational speed, monitoring the rotational speed of the engine, In the unloading operation, the unloading rotation speed increase correction and the unloading rotation speed decrease correction are repeatedly performed. The unload rotation speed increase correction gradually increases the target rotation speed from the unload rotation speed until the rotation speed of the engine rises to the lower limit unload rotation speed when the rotation speed of the engine is less than the lower limit unload rotation speed. The unload rotation speed reduction correction gradually reduces the target rotation speed increased by the unload rotation speed increase correction when the rotation speed of the engine exceeds the upper limit unload rotation speed until the rotation speed of the engine drops to the upper limit unload rotation speed. And during the full-load operation, full-load rotation speed reduction correction and full-load rotation speed increase correction are repeatedly performed, The full-load rotation speed reduction correction gradually reduces the target rotation speed from the full-load rotation speed until the rotation speed of the engine drops to the upper limit full-load rotation speed when the rotation speed of the engine exceeds the upper limit full-load rotation speed. The full load rotation speed increase correction gradually increases the target rotation speed reduced by the full load rotation speed reduction correction until the engine rotation speed reaches the lower full load rotation speed limit when the engine rotation speed is lower than the lower full load rotation speed limit.

5. The rotation speed control method of an engine driven compressor according to claim 2, characterized in that: The speed of decrease of the target rotation speed in the unload rotation speed decrease correction is made slower than the speed of increase of the target rotation speed in the unload rotation speed increase correction.

6. The rotation speed control method of an engine driven compressor according to claim 3, characterized in that: The increase speed of the target rotation speed in the full load rotation speed increase correction is made slower than the decrease speed of the target rotation speed in the full load rotation speed decrease correction.

7. The method for controlling the rotation speed of an engine driven compressor according to claim 4, characterized in that: making the speed of decrease of the target rotation speed in the unloaded rotation speed decrease correction slower than the speed of increase of the target rotation speed in the unloaded rotation speed increase correction, And the increase speed of the target rotation speed in the full load rotation speed increase correction is made slower than the decrease speed of the target rotation speed in the full load rotation speed decrease correction.

8. The method for controlling the rotation speed of an engine driven compressor according to claim 2, 4, 5 or 7, characterized in that: The number of times that the rotation speed of the engine is lower than the lower limit unloading rotation speed in one unloading operation is counted, and as the count number increases, slowing down the increase rate of the target rotational speed in the unloading rotational speed increase correction, and / or The speed of reduction of the target rotation speed in the unload rotation speed reduction correction is slowed down.

9. The rotation speed control method of an engine driven compressor according to claim 3, 4, 6 or 7, characterized in that: The number of times the engine rotation speed exceeds the upper limit full-load rotation speed during the full-load operation is counted, and as the count number increases, slowing down the speed of decrease of the target rotation speed in the full-load rotation speed decrease correction, and / or The increasing speed of the target rotation speed in the full-load rotation speed increase correction is slowed down.

10. A rotation speed control device for an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit for realizing a fuel injection amount corresponding to a specified target rotational speed, a rotational speed control device of the engine driven compressor includes an electronic control device, the electronic control device outputs a control signal specifying the target rotational speed corresponding to a control pressure to the engine control unit based on a predetermined correspondence relationship, the control pressure being a pressure on a discharge side of the compressor body detected by a pressure detection mechanism, The rotation speed control device of the engine driven compressor is characterized in that: The electronic control device comprises: a storage mechanism for storing a predetermined permissible range set for the target rotation speed; A rotation speed acquisition mechanism for acquiring the rotation speed of the engine; and The rotational speed correction mechanism compares the rotational speed of the engine obtained by the rotational speed obtaining mechanism with the upper limit speed and the lower limit speed of the allowable range for the specified target rotational speed, and when the rotational speed of the engine is less than the lower limit speed of the allowable range or exceeds the upper limit speed of the allowable range, gradually increases or decreases the specified target rotational speed until the rotational speed of the engine becomes a rotational speed within the allowable range.

11. A rotation speed control device for an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit that realizes a fuel injection amount corresponding to a specified target rotational speed and has a predetermined minimum rotational speed, a rotational speed control device of the engine driven compressor closes a suction port of the compressor body according to a change in a control pressure as a pressure on a discharge side of the compressor body, and performs an unloaded operation in which the engine is driven using an unloaded rotational speed as the target rotational speed, the unloaded rotational speed being a rotational speed that is higher than the minimum rotational speed by a predetermined amount when the control pressure is equal to or higher than a predetermined unloaded operation start pressure, The rotation speed control device of the engine driven compressor is characterized by being provided with: a pressure detection mechanism for detecting the control pressure; and an electronic control device, which outputs a control signal specifying the target rotation speed to the engine control unit based on the control pressure detected by the pressure detection mechanism, The electronic control device is provided with: a storage mechanism for storing a lower limit unload rotational speed, the lower limit unload rotational speed being higher than the lowest rotational speed of the engine by a predetermined margin and being set to a rotational speed below the unload rotational speed, and an upper limit unload rotational speed being a rotational speed higher than the lower limit unload rotational speed by a predetermined amount and being set to a rotational speed above the unload rotational speed; A rotation speed obtaining mechanism for obtaining the rotation speed of the engine; a control signal output mechanism that outputs a control signal to set the unloaded rotational speed to a target rotational speed to the engine control unit when the pressure detection mechanism detects a pressure equal to or higher than the unloaded operation start pressure as the control pressure; an unloading rotation speed increasing mechanism that compares the rotation speed of the engine acquired by the rotation speed acquiring mechanism with the lower limit unloading rotation speed stored in the storage mechanism during unloading operation, and when the rotation speed of the engine is less than the lower limit unloading rotation speed, changes the control signal output by the control signal output mechanism in such a manner that the target rotation speed gradually increases from the unloading rotation speed until the rotation speed of the engine rises to the lower limit unloading rotation speed; and The unloading rotational speed reducing mechanism changes the control signal output by the control signal output mechanism in such a manner that the target rotational speed increased by the unloading rotational speed increasing mechanism gradually decreases when the rotational speed of the engine obtained by the rotational speed obtaining mechanism exceeds the upper limit unloading rotational speed during the unloading operation, until the rotational speed of the engine drops to the upper limit unloading rotational speed.

12. A rotation speed control device for an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit for realizing a fuel injection amount corresponding to a specified target rotation speed and has a predetermined maximum rotation speed, a rotation speed control device of the engine driven compressor fully opens a suction port of the compressor body according to a change in a control pressure as a pressure on a discharge side of the compressor body, and performs a full load operation in which the engine is driven with a full load rotation speed as the target rotation speed, the full load rotation speed being a rotation speed lower than the maximum rotation speed by a predetermined amount when the control pressure is below a predetermined full load operation start pressure, The rotation speed control device of the engine driven compressor is characterized by being provided with: a pressure detection mechanism for detecting the control pressure; and an electronic control device, which outputs a control signal specifying the target rotation speed to the engine control unit based on the control pressure detected by the pressure detection mechanism, The electronic control device is provided with: a storage mechanism for storing an upper limit full load rotational speed, the upper limit full load rotational speed being lower than the maximum rotational speed of the engine by a predetermined margin and being set to a rotational speed higher than the full load rotational speed, and a lower limit full load rotational speed being a rotational speed lower than the upper limit full load rotational speed by a predetermined amount and being set to a rotational speed lower than the full load rotational speed; A rotation speed obtaining mechanism for obtaining the rotation speed of the engine; a control signal output mechanism that outputs a control signal to the engine control unit to set the full-load rotation speed as a target rotation speed when the pressure detection mechanism detects a pressure below the full-load operation start pressure as the control pressure; a full-load rotational speed reducing mechanism that compares the rotational speed of the engine acquired by the rotational speed acquiring mechanism with the upper limit full-load rotational speed stored in the storage mechanism during full-load operation, and when the rotational speed of the engine exceeds the upper limit full-load rotational speed, changes the control signal output by the control signal output mechanism in such a manner that the target rotational speed gradually decreases from the full-load rotational speed until the rotational speed of the engine drops to the upper limit full-load rotational speed; and A full-load rotational speed increasing mechanism, during the full-load operation, when the rotational speed of the engine obtained by the rotational speed obtaining mechanism is less than the lower limit full-load rotational speed, the control signal output by the control signal output mechanism is changed in such a way that the target rotational speed reduced by the full-load rotational speed reducing mechanism is gradually increased until the rotational speed of the engine rises to the lower limit full-load rotational speed.

13. A rotation speed control device for an engine driven compressor, An engine driven compressor includes an engine and a compressor body driven by the engine, the engine includes an engine control unit for realizing a fuel injection amount corresponding to a specified target rotational speed, and has a predetermined maximum rotational speed and a minimum rotational speed, and in a rotational speed control device of the engine driven compressor, according to a change in a control pressure as a pressure on a discharge side of the compressor body, when the control pressure is below a predetermined full load operation start pressure, a suction port of the compressor body is fully opened, and a full load operation of the engine is performed with a full load rotational speed as the target rotational speed to drive the engine, the full load rotational speed being a rotational speed lower by a predetermined amount than the maximum rotational speed, and when the control pressure is above an unload operation start pressure, the suction port of the compressor body is closed, and an unload operation of the engine is performed with an unload rotational speed as the target rotational speed to drive the engine, the unload operation start pressure being a pressure higher by a predetermined amount than the full load operation start pressure, the unload rotational speed being a rotational speed higher by a predetermined amount than the minimum rotational speed, and being a rotational speed lower by a predetermined amount than the full load rotational speed, The rotation speed control device of the engine driven compressor is characterized by being provided with: a pressure detection mechanism for detecting the control pressure; and an electronic control device, which outputs a control signal specifying the target rotation speed to the engine control unit based on the control pressure detected by the pressure detection mechanism, The electronic control device is provided with: a storage mechanism storing a lower limit unload rotational speed and an upper limit unload rotational speed, and storing an upper limit full load rotational speed and a lower limit full load rotational speed, wherein the lower limit unload rotational speed is higher than the lowest rotational speed of the engine by a predetermined margin and is set to a rotational speed below the unload rotational speed, the upper limit unload rotational speed is a rotational speed higher than the lower limit unload rotational speed by a predetermined margin and is set to a rotational speed above the unload rotational speed, the upper limit full load rotational speed is lower than the highest rotational speed of the engine by a predetermined margin and is set to a rotational speed above the full load rotational speed, and the lower limit full load rotational speed is a rotational speed lower than the upper limit full load rotational speed by a predetermined margin and is set to a rotational speed below the full load rotational speed; A rotation speed obtaining mechanism for obtaining the rotation speed of the engine; a control signal output mechanism that outputs a control signal to the engine control unit to set the unloaded rotational speed to a target rotational speed when the pressure detection mechanism detects a pressure that is higher than the unloaded operation start pressure as the control pressure, and outputs a control signal to the engine control unit to set the full-load rotational speed to a target rotational speed when the pressure detection mechanism detects a pressure that is lower than the full-load operation start pressure as the control pressure; an unloading rotation speed increasing mechanism, which, during unloading operation, compares the rotation speed of the engine acquired by the rotation speed acquiring mechanism with the lower limit unloading rotation speed stored in the storage mechanism, and when the rotation speed of the engine is less than the lower limit unloading rotation speed, changes the control signal output by the control signal output mechanism in such a manner that the target rotation speed gradually increases from the unloading rotation speed until the rotation speed of the engine rises to the lower limit unloading rotation speed; an unloading rotation speed reducing mechanism, which, during the unloading operation, when the rotation speed of the engine obtained by the rotation speed obtaining mechanism exceeds the upper limit unloading rotation speed, changes the control signal output by the control signal output mechanism in such a manner that the target rotation speed increased by the unloading rotation speed increasing mechanism is gradually reduced until the rotation speed of the engine drops to the upper limit unloading rotation speed; a full-load rotational speed reducing mechanism that compares the rotational speed of the engine acquired by the rotational speed acquiring mechanism with the upper limit full-load rotational speed stored in the storage mechanism during full-load operation, and when the rotational speed of the engine exceeds the upper limit full-load rotational speed, changes the control signal output by the control signal output mechanism in such a manner that the target rotational speed gradually decreases from the full-load rotational speed until the rotational speed of the engine drops to the upper limit full-load rotational speed; and A full-load rotational speed increasing mechanism, during the full-load operation, when the rotational speed of the engine obtained by the rotational speed obtaining mechanism is less than the lower limit full-load rotational speed, the control signal output by the control signal output mechanism is changed in such a way that the target rotational speed reduced by the full-load rotational speed reducing mechanism is gradually increased until the rotational speed of the engine rises to the lower limit full-load rotational speed.

14. The rotation speed control device of an engine driven compressor according to claim 11, characterized in that: The speed at which the unload rotational speed decreasing mechanism decreases the target rotational speed is made slower than the speed at which the unload rotational speed increasing mechanism increases the target rotational speed.

15. The rotation speed control device of an engine driven compressor according to claim 12, characterized in that: The speed at which the full-load rotational speed increasing mechanism increases the target rotational speed is made slower than the speed at which the full-load rotational speed decreasing mechanism decreases the target rotational speed.

16. The rotation speed control device of an engine driven compressor according to claim 13, characterized in that: The unloading rotational speed reducing mechanism reduces the target rotational speed at a speed slower than the unloading rotational speed increasing mechanism increases the target rotational speed. Furthermore, the speed at which the full-load rotational speed increasing mechanism increases the target rotational speed is made slower than the speed at which the full-load rotational speed decreasing mechanism decreases the target rotational speed.

17. The rotation speed control device for an engine driven compressor according to claim 11, 13, 14 or 16, characterized in that: The electronic control device is provided with a counting mechanism, which counts the number of times the rotation speed of the engine is lower than the lower limit unloading rotation speed in one unloading operation. As the number of counts by the counting mechanism increases, the unloading rotation speed increasing mechanism is configured to slow down the increase rate of the target rotation speed, and / or The unloading rotation speed reducing mechanism is set to make the speed of reducing the target rotation speed slower as the counted number of times by the counting mechanism increases.

18. The rotation speed control device for an engine driven compressor according to claim 12, 13, 14 or 16, characterized in that: The electronic control device is provided with a counting mechanism, which counts the number of times the rotation speed of the engine exceeds the upper limit full-load rotation speed during one full-load operation. As the number of counts by the counting mechanism increases, the full-load rotation speed reducing mechanism is set to slow down the speed of reducing the target rotation speed, and / or The full load rotation speed increasing mechanism is set to slow down the speed of increasing the target rotation speed as the counted number of times by the counting mechanism increases.

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