Maintenance and operation methods for internal combustion engines

Abstract

The present invention provides a maintenance operation method for an internal combustion engine that can form an oil film on the sliding surface of the cylinder in a short period of time, thereby reducing the number of no-load and loaded operations during maintenance operation of the internal combustion engine. [Solution] A maintenance operation method for an internal combustion engine comprising a cylinder and a piston housed so as to be reciprocable along the sliding surface of the cylinder, comprising: an oil supply step of supplying oil to the sliding surface of the cylinder by an oil supply device for supplying oil to the sliding surface of the cylinder while the internal combustion engine is stopped; and a cranking step of cranking the internal combustion engine while the oil supply step is being performed, wherein in the cranking step, an electric starter is driven to rotate a rotating shaft capable of transmitting driving force to the piston, and the rotating shaft is rotated at a rotational speed of a predetermined number of revolutions or higher.

Description

Technical Field

[0001] The present disclosure relates to a maintenance operation method for an internal combustion engine.

Background Art

[0002] For an internal combustion engine, particularly an internal combustion engine mounted on an emergency generator, a maintenance operation may be performed to form an oil film on the sliding surface of the cylinder by periodically performing no-load operation or load operation of the internal combustion engine in preparation for emergency start, thereby preventing seizure of the piston.

[0003] In addition, in order to suppress oil starvation of bearings and valve mechanisms of the internal combustion engine, the priming pump of the lubricating oil system may be periodically operated to supply lubricating oil to the bearings and valve mechanisms.

[0004] In the invention described in Patent Document 1, during standby of an emergency diesel engine, lubricating oil is supplied to the engine by operating the priming pump, and turning is performed using a decompression mechanism to maintain a good lubricated state of the main bearing and the like.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the no-load or loaded operation of an internal combustion engine, fuel is consumed, resulting in running costs each time maintenance is performed. Furthermore, wet stacking can cause various malfunctions in the lubrication oil supply system and exhaust gas discharge system. In addition, in the turning operation of an internal combustion engine, the low rotational speed (generally a few rpm) means that it takes a long time to supply lubricating oil to the entire circumference of the cylinder's sliding surface, and there is a risk that the oil film formed on the cylinder's sliding surface will be scraped off by the slow-moving piston. For these reasons, turning in an internal combustion engine is not suitable as a maintenance operation to replace no-load or loaded operation of the internal combustion engine because it is difficult to ensure sufficient thickness of the oil film formed on the cylinder's sliding surface.

[0007] In view of the circumstances described above, at least one embodiment of the present disclosure aims to provide a maintenance operation method for an internal combustion engine that can form an oil film on the sliding surface of a cylinder in a short period of time and reduce the number of no-load and loaded operations during maintenance operation of the internal combustion engine. [Means for solving the problem]

[0008] A maintenance operation method for an internal combustion engine according to at least one embodiment of this disclosure is: A maintenance operation method for an internal combustion engine comprising a cylinder and a piston housed so as to be reciprocable along the sliding surface of the cylinder, An oil supply step of supplying oil to the sliding surface of the cylinder by an oil supply device for supplying oil to the sliding surface of the cylinder while the internal combustion engine is stopped, The system includes a cranking step in which the internal combustion engine is cranked while the oil supply step is being performed, In the cranking step, an electric starter is driven to rotate a rotating shaft capable of transmitting driving force to the piston, causing the rotating shaft to rotate at a predetermined rotational speed or higher. The predetermined rotational speed of the cranking is higher than the turning speed (several rpm). [Effects of the Invention]

[0009] According to at least one embodiment of the present disclosure, a maintenance operation method for an internal combustion engine is provided that can form an oil film on the sliding surface of a cylinder in a short period of time and can reduce the number of no-load and loaded operations during maintenance operation of the internal combustion engine. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of an internal combustion engine that is the target of maintenance operation in a maintenance operation method for an internal combustion engine in one embodiment of the present disclosure. [Figure 2] This is a schematic diagram of the oil supply system of an internal combustion engine that is the target of maintenance operation in a maintenance operation method for an internal combustion engine in one embodiment of the present disclosure. [Figure 3] This is a flowchart of a maintenance operation method for an internal combustion engine according to one embodiment of the present disclosure. [Figure 4] This is an explanatory diagram illustrating an oil injection nozzle in one embodiment of the present disclosure. [Figure 5] This is an explanatory diagram illustrating an oil injection nozzle in one embodiment of the present disclosure. [Figure 6] This is an explanatory diagram illustrating an oil injection nozzle in one embodiment of the present disclosure. [Figure 7] This is an explanatory diagram illustrating the cranking step in one embodiment of the present disclosure. [Figure 8] This is an explanatory diagram illustrating the cranking step in one embodiment of the present disclosure. [Figure 9] This is an explanatory diagram illustrating the cranking step in one embodiment of the present disclosure. [Figure 10] This is an explanatory diagram illustrating the cranking step in one embodiment of the present disclosure. [Figure 11] This is an explanatory diagram illustrating the cranking step in one embodiment of the present disclosure. [Figure 12] This is a schematic diagram of a starter in one embodiment of the present disclosure. [Figure 13]It is an explanatory diagram for explaining a plurality of starters in one embodiment of the present disclosure. [Figure 14] It is an explanatory diagram for explaining a plurality of starters in one embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples.

[0012] (Internal Combustion Engine) FIG. 1 is a schematic diagram of an internal combustion engine 1 which is the object of maintenance operation of the maintenance operation method of the internal combustion engine 1 in one embodiment of the present disclosure. As shown in FIG. 1, the internal combustion engine 1 according to some embodiments includes at least one (a plurality in the illustrated example) of cylinders 2, at least one (a plurality in the illustrated example) of pistons 3, and a rotating shaft 4. In the following embodiments, the case where the internal combustion engine 1 is a diesel engine mounted on an emergency generator will be described. However, the internal combustion engine 1 of the present disclosure may be an internal combustion engine other than the internal combustion engine mounted on an emergency generator, or may be an engine other than a diesel engine such as a gas engine.

[0013] Each of the plurality of pistons 3 has a top surface (surface) 31 and a back surface 32, and the piston 3 is accommodated in the corresponding cylinder 2. As shown in FIGS. 4 to 6, each of the plurality of cylinders 2 has an inner peripheral surface 201 that forms an internal space 20 extending along the central axis CA of the cylinder 2, and an opposing surface 202 that faces the top surface 31 of the piston 3 accommodated in the internal space . The cylinder 2 has a combustion chamber 20A formed by the inner peripheral surface 201 of the cylinder 2, the opposing surface 202, and the top surface 31 of the piston 3.

[0014] The piston 3 is housed in the cylinder 2 so as to be able to reciprocate along the sliding surface 21. The piston 3 is configured to reciprocate between the top dead center and the bottom dead center along the axial direction of the cylinder 2 (the direction in which the central axis CA extends). The sliding surface 21 is the portion of the inner circumferential surface 201 that the outer circumferential surface of the piston 3 faces when the piston 3 reciprocates between the top dead center and the bottom dead center.

[0015] The internal combustion engine 1, as shown in Figure 1, comprises at least one (multiple in the illustrated example) injectors 10 configured to inject high-pressure liquid fuel into the combustion chamber 20A. Each of the multiple injectors 10 is provided in the cylinder 2 corresponding to the injector 10. The internal combustion engine (diesel engine) 1 causes the liquid fuel to spontaneously ignite by injecting high-pressure liquid fuel from the injectors 10 into compressed air in the combustion chamber 20A that has been compressed by the piston 3 and exceeded its ignition point. The piston 3 is pushed out by the expansion of the combustion gas produced by the spontaneous ignition of the liquid fuel, and reciprocates within the cylinder 2, generating driving force.

[0016] The rotating shaft 4 is configured to transmit driving force to each of the multiple pistons 3. The rotating shaft 4 is configured to rotate when the driving force generated by each of the multiple pistons 3 is transmitted to it. The rotating shaft 4 includes a crankshaft 41 configured to rotate in conjunction with the reciprocating motion of each of the multiple pistons 3, and a transmission shaft 42 configured to rotate in conjunction with the rotation of the crankshaft 41.

[0017] In the illustrated embodiment, the internal combustion engine 1, as shown in Figure 1, comprises a plurality of connecting rods 11 configured to transmit driving force between each of a plurality of pistons 3 and a crankshaft 41, a pair of bearings 12 configured to rotatably support the crankshaft 41, a first drive force transmission device 13 configured to transmit driving force between the crankshaft 41 and a transmission shaft 42, and a generator 14 configured to generate electricity when the driving force of the rotating shaft 4 is transmitted.

[0018] In the embodiment shown in Figure 1, each of the multiple connecting rods 11 is mechanically connected at one end to a corresponding piston 3 via a piston pin 111 (see Figures 4 to 6), and at the other end to a connecting portion 411 of the crankshaft 41. The connecting portion 411 of the crankshaft 41 is located between a pair of supported portions of the crankshaft 41, each supported by a pair of bearings 12. The crankshaft 41 rotates due to the driving force transmitted from the piston 3 via the connecting rods 11. The piston 3 also reciprocates due to the driving force transmitted from the crankshaft 41 via the connecting rods 11.

[0019] In the embodiment shown in Figure 1, the first drive force transmission device 13 includes a crank-side gear (external gear) 131 attached to the crankshaft 41, and a transmission-side gear (external gear) 132 attached to the transmission shaft 42 and configured to mesh with the crank-side gear 131. The first drive force transmission device 13 enables the transmission of drive force between the crank-side gear 131 and the transmission-side gear 132 by the meshing of the crank-side gear 131 and the transmission-side gear 132. The first drive force transmission device 13 is not limited to the illustrated example, as long as it is configured to transmit drive force between the crankshaft 41 and the transmission shaft 42. The generator 14 is mechanically connected to the transmission shaft 42.

[0020] In the illustrated embodiment, the internal combustion engine 1, as shown in Figure 1, includes at least one electric starter 6 having a drive shaft 61 and configured to rotate the drive shaft 61 by power supplied from a power source (not shown), and a second drive force transmission device 15 configured to transmit driving force between a rotating shaft 4 (crankshaft 41 in the illustrated example) and the drive shaft 61 of at least one starter 6.

[0021] In the embodiment shown in Figure 1, the second drive force transmission device 15 includes a flywheel 151 attached to the crankshaft 41 and equipped with an external gear 152, and a starter-side gear (external gear) 153 attached to the drive shaft 61 and configured to mesh with the external gear 152. The second drive force transmission device 15 is capable of transmitting drive force between the external gear 152 and the starter-side gear 153. The second drive force transmission device 15 is not limited to the illustrated example and only needs to be configured to transmit drive force between the rotating shaft 4 and the drive shaft 61.

[0022] Figure 2 is a schematic diagram of the oil supply system of an internal combustion engine 1 which is the subject of maintenance operation in a maintenance operation method for an internal combustion engine 1 in one embodiment of the present disclosure. The internal combustion engine 1 is equipped with an oil supply device 5 for supplying oil to the sliding surface 21 of the cylinder 2. As shown in Figure 2, the oil supply device 5 includes at least one oil injection nozzle 51, an oil introduction line 53 for leading oil from an oil supply source 52 to at least one oil injection nozzle 51, and an electric oil pump P1 for sending oil from the oil supply source 52 to at least one oil injection nozzle 51 via the oil introduction line 53. The oil supply source 52 has an oil reservoir 520 in which oil is stored. The electric oil pump P1 has a rotating body which rotates when power is supplied from a power source (not shown), and is configured to send oil by the rotation of the rotating body.

[0023] In the illustrated embodiment, the oil supply source 52 is an oil pan (see Figure 1) mounted below the cylinder 2 (cylinder block 23, see Figure 4) in the internal combustion engine 1, and has an oil reservoir 520 where oil flowing down from the sliding surface 21 of the cylinder 2 accumulates. The oil introduction line 53 may also lead oil to oil demand parts 50 (501, 502) other than at least one oil injection nozzle 51 (51A, 51B). The oil demand parts 50 (501, 502) are parts that require at least one of oil lubrication or cooling. Examples of oil demand parts 50 (501, 502) include a rotating body such as a rotating shaft 4, a drive force transmission part such as a second drive force transmission device 15, or an oil passage (not shown) provided around the combustion chamber 20A of the cylinder 2.

[0024] As shown in Figure 2, the oil inlet line 53 may be equipped with an oil cooler 54 for cooling the oil flowing through the oil inlet line 53, and an oil filter 55 for removing foreign matter from the oil flowing through the oil inlet line 53. In the illustrated example, the oil filter 55 is located downstream of the oil cooler 54 in the oil inlet line 53 (towards the oil demand section 50).

[0025] As shown in Figure 2, the oil introduction line 53 is connected to an operating oil introduction line 56 that guides oil from an oil supply source 52 to an oil demand section 50 including at least one oil injection nozzle 51 during operation of the internal combustion engine 1, and may share a portion of the line with the operating oil introduction line 56. An oil pump P2 is provided in the operating oil introduction line 56. The oil pump P2 has a rotating body that rotates when the driving force (rotational force) of the rotating shaft 4 is transmitted, and is configured to deliver oil by rotating this body.

[0026] In the embodiment shown in Figure 2, the upstream end of the oil introduction line 53 and the upstream end of the operating oil introduction line 56 are each connected to the oil reservoir 520. The downstream end of the operating oil introduction line 56 is connected to a connection part 57 located upstream of the oil introduction line 53 (towards the oil reservoir 520) from the oil cooler 54 and the oil filter 55.

[0027] As shown in Figure 2, the electric oil pump P1 is preferably an oil priming pump configured to supply oil to the oil demand unit 50 when the internal combustion engine 1 is started. By using an oil priming pump that is sometimes mounted on the internal combustion engine 1 as the electric oil pump P1, the line for guiding oil to the oil demand unit 50 when the internal combustion engine 1 is started can be reused as the oil introduction line 53, thereby suppressing the complexity of the structure of the internal combustion engine 1.

[0028] (Maintenance and operation methods for internal combustion engines) Figure 3 is a flowchart of a maintenance operation method for an internal combustion engine 1 according to one embodiment of the present disclosure. A maintenance operation method for an internal combustion engine 1 according to several embodiments comprises an oil supply step S1 and a cranking step S2, as shown in Figure 3.

[0029] In the oil supply step S1, oil is supplied to the sliding surface 21 of the cylinder 2 by an oil supply device 5 while the internal combustion engine 1 is stopped. In the cranking step S2, the internal combustion engine 1 is cranked while the oil supply step S1 is being performed. In the cranking step S2, an electric starter 6 is driven to rotate a rotating shaft 4 capable of transmitting driving force to the piston 3, causing the rotating shaft 4 to rotate at a rotational speed of a predetermined speed or higher. Here, the predetermined rotational speed is 10 rpm or higher, which is higher than the rotational speed during turning (several rpm). The predetermined rotational speed may be 50 rpm or higher, or 100 rpm or higher.

[0030] In the maintenance operation method for the internal combustion engine 1 according to this embodiment, an oil film can be formed on the sliding surface 21 of the cylinder 2 by performing the oil supply step S1 and the cranking step S2 instead of the no-load and loaded operations that require fuel consumption. Therefore, by performing the maintenance operation method for the internal combustion engine 1, the number of no-load and loaded operations during maintenance operation of the internal combustion engine 1 can be reduced. Furthermore, in the maintenance operation method for the internal combustion engine 1 according to this embodiment, an oil film can be formed on the sliding surface 21 of the cylinder 2 in a short period of time by rotating the rotating shaft 4 at a speed higher than the rotational speed during turning using the electric starter 6. In the maintenance operation method for the internal combustion engine 1 according to this embodiment, by rotating the rotating shaft 4 at high speed using the electric starter 6, it is possible to suppress the scraping off of the oil film formed on the sliding surface 21 of the cylinder 2 by the piston 3, thereby ensuring the thickness of the oil film formed on the sliding surface 21.

[0031] (Oil spray nozzle) Figures 4 to 6 are explanatory diagrams illustrating an oil injection nozzle 51 in one embodiment of the present disclosure. Figures 4 to 6 show a cross-section along the central axis CA of the cylinder 2, with the piston 3 at top dead center indicated by a solid line. The at least one oil injection nozzle 51 described above has an injection hole 511 for injecting oil, as shown in Figures 4 to 6. In the oil supply step S1 described above, an electric oil pump P1 is driven to inject oil from the injection hole 511 of the at least one oil injection nozzle 51.

[0032] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, an electric oil pump P1 is driven and oil is injected from the injection hole 511 of at least one oil injection nozzle 51, thereby quickly supplying oil to the sliding surface 21 of the cylinder 2 while the internal combustion engine 1 is stopped.

[0033] In the embodiments shown in Figures 4 to 6, the cylinder 2 includes a cylinder head 22 to which an injector 10 is attached, a cylinder block 23 housing a piston 3 and a crankshaft 41, and a cylinder liner 24 which is a cylindrical body attached to the cylinder block 23 and extending along the central axis CA of the cylinder 2. The inner circumferential surface 201 described above is the inner circumferential surface of the cylinder liner 24, and the sliding surface 21 is a part of the inner circumferential surface of the cylinder liner 24. The cylinder head 22 has the opposing surface 202 described above.

[0034] In the embodiments shown in Figures 4 to 6, the piston 3 has a cylindrical projection 33 that protrudes cylindrically in a direction away from the top surface 31 than the back surface 32 in the axial direction of the piston 3, extending the outer circumferential surface of the piston 3 in a direction away from the top surface 31. The piston 3 has an oil passage 34 formed inside the piston 3 between the top surface 31 and the back surface 32 in the axial direction of the piston 3, an oil inlet 35 provided on the back surface 32, and an oil outlet 36 provided on the back surface 32. The oil passage 34 is formed in an annular shape extending along the circumferential direction of the piston 3 and communicates with the back surface side space 20B facing the back surface 32 of the internal space 20 via the oil inlet 35 and the oil outlet 36.

[0035] In some embodiments of the internal combustion engine 1, the central axis CA of the cylinder 2 is inclined with respect to the vertical direction (up and down direction in the illustrated plane), as shown in Figures 4 to 6. The sliding surface 21 described above includes an upper sliding surface 21A located above the central axis CA in a cross-section including the central axis CA of the cylinder 2 as shown in Figures 4 to 6, and a lower sliding surface 21B located below the central axis CA.

[0036] In some embodiments, the at least one oil injection nozzle 51 described above includes a first oil injection nozzle 51A whose nozzle 511 is directed toward the upper sliding surface 21A, as shown in Figure 4. The direction of the nozzle 511 of the first oil injection nozzle 51A toward the upper sliding surface 21A means that the extension line LA1, obtained by extending the central axis of the nozzle 511 of the first oil injection nozzle 51A in the injection direction, passes through the upper sliding surface 21A.

[0037] As shown in Figure 4, when the piston 3 is at bottom dead center, the position of the upper sliding surface 21A facing the rearmost part of the piston 3 (the part closest to the crankshaft 41 in the axial direction of the cylinder 2, in the illustrated example, the tip of the cylindrical projection 33) is defined as the 0% position, and when the piston 3 is at top dead center, the position of the upper sliding surface 21A facing the aforementioned rearmost part of the piston 3 is defined as the 100% position. In this case, it is preferable that the extension line LA1 passes between the 0% position and the 100% position. Furthermore, it is preferable that the extension line LA1 passes between the 20% and 80% positions of the upper sliding surface 21A, and even more preferable that it passes between the 40% and 60% positions of the upper sliding surface 21A.

[0038] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, in the oil supply step S1, oil can be injected from the injection hole 511 of the first oil injection nozzle 51A, thereby supplying oil to the upper sliding surface 21A, which is located above the central axis CA of the cylinder 2 and is relatively difficult to supply oil to, and forming an oil film on the upper sliding surface 21A. Furthermore, in the maintenance operation method of the internal combustion engine 1 according to this embodiment, a portion of the oil supplied to the upper sliding surface 21A flows down to the lower sliding surface 21B, thereby ensuring the formation of an oil film around the entire circumference of the sliding surface 21.

[0039] In some embodiments, the at least one oil injection nozzle 51 described above includes, as shown in Figure 4, a first oil injection nozzle 51A and a second oil injection nozzle 51B whose nozzle 511 is directed toward the back surface 32 of the piston 3. The statement that the nozzle 511 of the second oil injection nozzle 51B is directed toward the back surface 32 means that the extension line LA2 obtained by extending the central axis of the nozzle 511 of the second oil injection nozzle 51B in the injection direction passes through the back surface 32.

[0040] A portion of the oil injected from the second oil injection nozzle 51B is introduced into the oil passage 34 via the oil inlet 35, and cools the piston 3 as it flows through the oil passage 34. The oil that has flowed through the oil passage 34 is discharged to the outside of the piston 3 via the oil outlet 36. A portion of the oil injected from the second oil injection nozzle 51B collides with the back surface 32 of the piston 3 and then flows down to the lower sliding surface 21B, which is a sliding surface 21 located below the central axis CA of the cylinder 2.

[0041] It is preferable that the extension line LA2 of the second oil injection nozzle 51B passes through the oil inlet 35 provided on the back surface 32. In this case, it is easier to introduce the oil injected from the second oil injection nozzle 51B into the oil passage 34 via the oil inlet 35, and it is easier to exert the cooling effect of the piston 3 by the oil flowing through the oil passage 34.

[0042] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, in the oil supply step S1, oil is injected from the injection hole 511 of the second oil injection nozzle 51B, causing the injected oil to flow down from the back surface 32 of the piston 3 to the lower sliding surface 21B, which is a sliding surface 21 located below the central axis CA of the cylinder 2, thereby forming an oil film on the lower sliding surface 21B. The second oil injection nozzle 51B may be mounted on the internal combustion engine 1 to supply oil to the back surface 32 of the piston 3 during operation of the internal combustion engine 1. By reusing the second oil injection nozzle 51B for oil supply during maintenance operation, the complexity of the structure of the internal combustion engine 1 can be suppressed.

[0043] In some embodiments of the internal combustion engine 1, as shown in Figure 4, an oil injection amount adjustment device 7 is provided that is configured to adjust the oil injection amount of the first oil injection nozzle 51A and the oil injection amount of the second oil injection nozzle 51B. In the oil supply step S1 described above, the oil injection amount adjustment device 7 adjusts the oil injection amount so that the oil injection amount of the first oil injection nozzle 51A is greater than the oil injection amount of the second oil injection nozzle 51B. Alternatively, in the oil supply step S1, the oil injection amount adjustment device 7 may set the oil injection amount of the second oil injection nozzle 51B to zero.

[0044] During normal operation of the internal combustion engine 1 (no-load operation, loaded operation), the oil injection amount adjustment device 7 adjusts the oil injection amount of the second oil injection nozzle 51B to be greater than the oil injection amount of the first oil injection nozzle 51A. Alternatively, during normal operation of the internal combustion engine 1, the oil injection amount adjustment device 7 may set the oil injection amount of the first oil injection nozzle 51A to zero.

[0045] In the embodiment shown in Figure 4, the oil introduction line 53 described above branches at the branching section 533 into a first oil introduction line 531 for introducing oil to the first oil injection nozzle 51A and a second oil introduction line 532 for introducing oil to the second oil injection nozzle 51B. The oil injection amount adjustment device 7 includes a first flow rate adjustment valve 71 provided in the first oil introduction line 531, a second flow rate adjustment valve 72 provided in the second oil introduction line 532, and a valve opening indicator device 73 for instructing the valve opening degree of the first flow rate adjustment valve 71 and the second flow rate adjustment valve 72. The oil injection amount adjustment device 7 may also include a three-way valve provided in the branching section 533 instead of the first flow rate adjustment valve 71 and the second flow rate adjustment valve 72, and the valve opening indicator device 73 may be configured to instruct the valve opening degree of the three-way valve.

[0046] The valve opening indicator (controller) 73 is an electronic control unit for controlling the valve openings of the first flow control valve 71 and the second flow control valve 72. The valve opening indicator 73 may be configured as a microcomputer including an input device (input interface), an output device (output interface), a storage device (such as ROM or RAM memory, or external storage device), and a processing unit (CPU). The valve opening indicator 73 is configured such that, for example, the CPU operates (for example, by performing calculations on data) according to instructions from a program loaded into the main memory of the above-mentioned memory, thereby achieving valve opening control of the first flow control valve 71 and the second flow control valve 72, as described later.

[0047] The valve opening indicator device 73 is capable of acquiring operating mode information indicating whether the current operating mode of the internal combustion engine 1 is normal operation (no-load operation, loaded operation) or maintenance operation. The valve opening indicator device 73 stores the operating mode information acquired via the input device and first association information, which associates the pre-set operating mode with the valve openings of the first flow control valve 71 and the second flow control valve 72, in the storage device. Based on the operating mode information and the first association information stored in the storage device, the valve opening indicator device 73 acquires the valve openings of the first flow control valve 71 and the second flow control valve 72 according to the current operating mode of the internal combustion engine 1, and instructs the valve openings of the first flow control valve 71 and the second flow control valve 72, respectively, via the output device.

[0048] In one embodiment, the first association information sets the valve openings of the first flow control valve 71 and the second flow control valve 72 so that when the operating mode of the internal combustion engine 1 is maintenance operation, the oil flow rate through the first oil introduction line 531 is greater than the oil flow rate through the second oil introduction line 532.

[0049] In the maintenance operation method for the internal combustion engine 1 according to this embodiment, in the oil supply step S1, the amount of oil injected by the first oil injection nozzle 51A is made greater than the amount of oil injected by the second oil injection nozzle 51B, thereby enabling oil to be supplied to the upper sliding surface 21A, which is relatively difficult to supply oil to, and enabling the formation of an oil film on the upper sliding surface 21A. As a result, the maintenance operation method for the internal combustion engine 1 can reliably form an oil film around the entire circumference of the sliding surface 21.

[0050] In some embodiments, the valve opening indicator 73 may obtain information (signals) indicating the oil temperature from an oil temperature acquisition device 8 (see Figure 4) configured to acquire the current temperature of the oil in either the oil supply source 52 (illustrated example) or the oil introduction line 53. The oil temperature acquisition device 8 may be a temperature sensor configured to measure the oil temperature, and the temperature sensor may be configured to send the measured oil temperature to the valve opening indicator 73 via wired or wireless means.

[0051] During maintenance operation, shutdown, and startup of the internal combustion engine 1, the oil temperature is lower than during steady-state operation because fuel heat is not applied to the oil. The valve opening indicator device 73 may store in the storage device information information indicating the oil temperature obtained from the oil temperature acquisition device 8, and second association information which associates a preset oil temperature with the valve openings of the first flow control valve 71 and the second flow control valve 72, respectively. Based on the oil temperature information and the second association information stored in the storage device, the valve opening indicator device 73 obtains the valve openings of the first flow control valve 71 and the second flow control valve 72 according to the current oil temperature of the internal combustion engine 1, and instructs the valve openings of the first flow control valve 71 and the second flow control valve 72, respectively, via the output device.

[0052] In one embodiment, the second association information sets the valve openings of the first flow control valve 71 and the second flow control valve 72 so that when the oil temperature acquired by the oil temperature acquisition device 8 is below a threshold, the oil flow rate through the first oil introduction line 531 is greater than the oil flow rate through the second oil introduction line 532. Furthermore, the second association information sets the valve openings of the first flow control valve 71 and the second flow control valve 72 so that when the oil temperature acquired by the oil temperature acquisition device 8 exceeds a threshold, the oil flow rate through the second oil introduction line 532 is greater than the oil flow rate through the first oil introduction line 531.

[0053] In some embodiments, the at least one oil injection nozzle 51 described above comprises a wide-angle oil injection nozzle 51C configured to inject oil at a wide angle onto the upper sliding surface 21A, which is a sliding surface located above the back surface 32 of the piston 3 and the central axis CA inclined with respect to the vertical direction of the cylinder 2, as shown in Figure 6. The injection angle θ of the wide-angle oil injection nozzle 51C is preferably 60 degrees or more and 120 degrees or less, and more preferably 60 degrees or less and 90 degrees or less.

[0054] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, in the oil supply step S1, oil is injected from the injection hole 511 of the wide-angle oil injection nozzle 51C, thereby supplying oil to the upper sliding surface 21A located above the central axis CA of the cylinder 2 and the lower sliding surface 21B located below the central axis CA, respectively, and an oil film can be formed on these sliding surfaces 21A and 21B. As a result, the maintenance operation method of the internal combustion engine 1 can reliably form an oil film around the entire circumference of the sliding surface 21.

[0055] In some embodiments, the at least one oil injection nozzle 51 described above comprises a second oil injection nozzle 51B, whose injection hole 511 is directed toward the back surface 32 of the piston 3, as shown in Figure 5. The oil injection nozzle 51 in this embodiment does not include a first oil injection nozzle 51A.

[0056] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, in the oil supply step S1, oil is injected from the injection hole 511 of the second oil injection nozzle 51B, causing the injected oil to flow down from the back surface 32 of the piston 3 to the lower sliding surface 21B located below the central axis CA of the cylinder 2, thereby forming an oil film on the lower sliding surface 21B. The second oil injection nozzle 51B may be mounted on the internal combustion engine 1 to supply oil to the back surface 32 of the piston 3 during operation of the internal combustion engine 1. By reusing the second oil injection nozzle 51B for oil supply during maintenance operation, the complexity of the structure of the internal combustion engine 1 can be suppressed.

[0057] In some of the internal combustion engines 1 according to the embodiments described above, the central axis CA of the cylinder 2 was inclined with respect to the vertical direction (up and down direction in the illustrated plane). However, the maintenance operation methods for the internal combustion engines 1 according to some embodiments of this disclosure are also applicable when the central axis CA of the cylinder 2 extends along the vertical direction.

[0058] (Cranking step) Figures 7 to 11 are explanatory diagrams illustrating the cranking step S2 in one embodiment of the present disclosure. In Figures 7 to 11, the on / off state of the oil pump P1 is shown by a solid line L1 on a graph with time T on the horizontal axis. Also in Figures 7 to 11, the change in the rotational speed N of the rotating shaft 4 (crankshaft 41) is shown by a solid line L2 on a graph with time T on the horizontal axis and rotational speed N on the vertical axis. In Figure 11, the change in the temperature ST of the starter 6 is shown by a solid line L3 on a graph with time T on the horizontal axis and the temperature ST of the starter 6 on the vertical axis.

[0059] As shown in Figures 7 to 11, the cranking of the internal combustion engine 1 in cranking step S2 occurs after a predetermined waiting period has elapsed since the oil pump P1 was turned on. The waiting period includes the period from when the oil pump P1 was turned on until oil was injected from the oil injection nozzle 51 (first waiting period). The waiting period may further include the period from when oil injection from the oil injection nozzle 51 began until sufficient oil was supplied to the sliding surface 21 (second waiting period). In this case, since cranking is performed after oil has been reliably supplied to the sliding surface 21, wear on the piston 3 and the sliding surface 21 can be suppressed. In one embodiment, the waiting period is set to 5 seconds or more and 15 seconds or less.

[0060] In the cranking step S2 of the maintenance operation method for the internal combustion engine 1 according to several embodiments, as shown in Figures 7, 8, and 11, the cranking is performed intermittently multiple times, with a stop period SP in between during which the internal combustion engine 1 is not cranked. The stop period SP may be a predetermined period set in advance. Multiple stop periods SP (two in the illustrated example) may be provided in the cranking step S2.

[0061] In the embodiments shown in Figures 7 and 8, in the cranking step S2 described above, cranking is performed for a predetermined period of time, which is the operating period DP, then cranking is stopped for a stop period SP, and after the stop period SP has elapsed, cranking is performed again.

[0062] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, the cranking of the internal combustion engine 1 in the cranking step S2 is performed intermittently with a stop period SP in between, thereby shortening the continuous operating time of the starter 6. This suppresses the load on the starter 6 and also suppresses damage to the starter 6 due to overheating.

[0063] In some other embodiments, as shown in Figures 9 and 10, the cranking of the internal combustion engine 1 described above may be performed continuously in the cranking step S2 without interrupting the stop period SP. In the embodiments shown in Figures 9 and 10, the cranking in the cranking step S2 is performed only for a predetermined period, which is the operating period DP. In the maintenance operation method of the internal combustion engine 1 according to this embodiment, the cranking period can be shortened compared to the case where it is performed intermittently by performing the cranking of the internal combustion engine 1 continuously.

[0064] In some embodiments of the maintenance operation method for the internal combustion engine 1, as shown in Figures 8 and 10, the cranking step S2 described above includes a first rotation step S21 and a second rotation step S22 performed after the first rotation step S21. In the first rotation step S21, the starter 6 rotates the rotating shaft 4 at a first rotation speed which is equal to or greater than the predetermined rotation speed described above. In the second rotation step S22, the starter 6 rotates the rotating shaft 4 at a second rotation speed which is greater than the first rotation speed.

[0065] In the illustrated embodiment, the starter 6 is configured to increase or decrease its rotational speed in accordance with the voltage supplied to the starter 6. In the embodiment shown in Figure 8, the starter 6 is configured such that the voltage supplied to the starter 6 is increased during the stop period SP, thereby increasing the rotational speed of the rotating shaft 4 after the stop period SP (second rotational speed N2) compared to the rotational speed of the rotating shaft 4 before the stop period SP (first rotational speed N1). In the embodiment shown in Figure 10, the starter 6 is configured such that the voltage supplied to the starter 6 is increased during the operating period DP, thereby increasing the rotational speed of the rotating shaft 4 from the first rotational speed N1 to the second rotational speed N2 during the operating period DP. As shown in Figure 10, the increase in the rotational speed of the rotating shaft 4 in the cranking step S2 may be performed two or more times.

[0066] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, by gradually increasing the rotational speed during the execution of the cranking step S2, wear of the piston 3 and sliding surface 21 can be suppressed while an oil film can be formed on the sliding surface 21 of the cylinder 2 in a short period of time. Specifically, by rotating the rotating shaft 4 at a relatively low first rotational speed in the first rotational step S21, wear of the piston 3 and sliding surface 21 at the start of rotation when sufficient oil has not been supplied to the sliding surface 21 can be suppressed. Furthermore, by rotating the rotating shaft 4 at a relatively high second rotational speed in the second rotational step S22, the piston 3 can be reciprocated at a relatively high speed when sufficient oil has been supplied to the sliding surface 21.

[0067] In some other embodiments, as shown in Figures 7 and 9, the starter 6 may be used to rotate the rotating shaft 4 at a constant speed without changing its rotational speed during the cranking step S2 described above.

[0068] (Starter temperature acquisition device) Figure 12 is a schematic diagram of a starter 6 in one embodiment of the present disclosure. As shown in Figure 12, the starter 6 includes the drive shaft 61 described above, an armature (rotor) 62, a field coil (stator) 63, a casing 64, and brushes 65 for supplying current to the armature 62. The armature 62 includes an armature coil 621 and a commutator 622 and is mounted on the drive shaft 61 and configured to rotate with the drive shaft 61. The field coil 63 is positioned on the outer circumference of the armature 62 and is configured to form a magnetic field. The casing 64 houses the armature 62, the field coil 63 and the brushes 65 and supports the field coil 63.

[0069] Some embodiments of the internal combustion engine 1, as shown in Figure 1, include a starter temperature acquisition device 9 configured to acquire the current temperature of the starter 6, and a starter control device 90 for controlling the drive of the starter 6. The starter temperature acquisition device 9 is preferably a temperature sensor configured to measure the temperature of a part of the starter 6 that becomes relatively hot. The starter temperature acquisition device 9 is preferably one of the following, as shown in Figure 12: a temperature sensor 9A configured to measure the temperature of the armature 62 (committer 622 in the illustrated example), a temperature sensor 9B configured to measure the temperature of the field coil 63, or a temperature sensor 9C configured to measure the temperature of the brush 65.

[0070] The starter control device (controller) 90 is an electronic control unit for controlling the drive of the starter 6. The starter control device 90 may be configured as a microcomputer including an input device (input interface), an output device (output interface), a storage device (such as ROM or RAM memory, or an external storage device), and an arithmetic unit (CPU). The starter control device 90 is configured such that, for example, the CPU operates (for example, performs calculations on data) according to the instructions of a program loaded into the main memory of the above-mentioned memory, thereby realizing the drive control of the starter 6, which will be described later. The cranking in the cranking step S2 is performed by driving the starter 6 and is controlled by the starter control device 90.

[0071] The starter control device 90 is configured to acquire information (signals) indicating the temperature of the starter 6 from the starter temperature acquisition device 9. The starter temperature acquisition device 9 may be configured to send the acquired temperature value (measured value) of the starter 6 to the starter control device 90 via wired or wireless connection.

[0072] In some embodiments of the maintenance operation method for the internal combustion engine 1, a starter temperature acquisition step is included in which the temperature of the starter 6 is acquired by a starter temperature acquisition device 9. In the cranking step S2 described above, as shown in Figure 11, if the temperature of the starter 6 acquired in the starter temperature acquisition step exceeds the first temperature threshold TH1, cranking is not started. In one embodiment, the starter control device 90 is configured not to issue a drive command to the starter 6 in the cranking step S2 if the temperature of the starter 6 acquired by the starter temperature acquisition device 9 exceeds the first temperature threshold TH1.

[0073] In the maintenance operation method for the internal combustion engine 1 according to this embodiment, if the temperature of the starter 6 exceeds a first temperature threshold TH1, cranking is not started, thereby suppressing damage to the starter 6 due to overheating.

[0074] In some embodiments, during the cranking step S2, as shown in Figure 11, if the temperature of the starter 6 acquired in the temperature acquisition step exceeds the second temperature threshold TH2, the cranking that is currently in progress is stopped. In one embodiment, the starter control device 90 is configured to release or stop the drive instruction to the starter 6 during the cranking step S2 if the temperature of the starter 6 acquired by the starter temperature acquisition device 9 exceeds the second temperature threshold TH2. The second temperature threshold TH2 is lower than the allowable temperature, which is the upper limit of the temperature at which the temperature measurement target in the starter temperature acquisition device 9 can operate, and higher than the first temperature threshold TH1.

[0075] In the maintenance operation method for the internal combustion engine 1 according to this embodiment, if the temperature of the starter 6 exceeds the second temperature threshold TH2, the cranking that is currently in progress is stopped, thereby suppressing damage to the starter 6 due to overheating.

[0076] Figures 13 and 14 are explanatory diagrams illustrating a plurality of starters 6 in one embodiment of the present disclosure. In some embodiments, the internal combustion engine 1 comprises a plurality of the starters 6 described above, as shown in Figures 13 and 14. The internal combustion engine 1 may have two starters 6 (see Figure 13) or three starters 6. Each of the plurality of starters 6 is configured to transmit the rotational force (driving force) generated by the starter 6 to the rotating shaft 4 via a second drive force transmission device 15. In some embodiments, the cranking step S2 described above involves driving one of the plurality of starters 6. In the cranking step S2, the other starters 6 of the plurality of starters 6 are not driven.

[0077] In the maintenance operation method of the internal combustion engine 1 according to this embodiment, by limiting the starter 6 driven in the cranking step S2 to one, the probability of failure of the starter 6 that is not used for maintenance operation among the multiple starters 6 can be reduced, thereby ensuring robustness when starting the internal combustion engine 1.

[0078] Furthermore, the starter 6 that is driven in cranking step S2 may be a starter 6 dedicated to maintenance operation of the internal combustion engine 1, which is not driven during normal operation of the internal combustion engine 1 (no-load operation and loaded operation). For example, of the three starters 6 shown in Figure 14, one starter 6 is for maintenance operation and the other two starters 6 are for normal operation. By limiting the starter 6 driven in cranking step S2 to a starter 6 dedicated to maintenance operation, the probability of failure of the starter 6 used during operation of the internal combustion engine 1 can be reduced, thereby ensuring robustness when starting the internal combustion engine 1.

[0079] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components.

[0080] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0081] The contents described in some of the embodiments above can be understood, for example, as follows:

[0082] [1] A maintenance operation method for an internal combustion engine (1) according to at least one embodiment of the present disclosure is: A maintenance operation method for an internal combustion engine (1) comprising a cylinder (2) and a piston (3) housed so as to be reciprocable along the sliding surface (21) of the cylinder (2), An oil supply step (S1) is performed by supplying oil to the sliding surface (21) of the cylinder (2) by an oil supply device (5) for supplying oil to the sliding surface (21) of the cylinder (2) while the internal combustion engine (1) is stopped, The system includes a cranking step (S2) in which the internal combustion engine (1) is cranked while the oil supply step (S1) is being performed, In the cranking step (S2), an electric starter (6) is driven to rotate a rotating shaft (4) capable of transmitting driving force to the piston (3), causing the rotating shaft (4) to rotate at a rotational speed of a predetermined number of revolutions or higher.

[0083] According to the method described in [1] above, an oil film can be formed on the sliding surface (21) of the cylinder (2) by performing the oil supply step (S1) and the cranking step (S2) instead of the no-load and loaded operations that require fuel consumption. Therefore, by performing the maintenance operation method for the internal combustion engine (1), the number of no-load and loaded operations during maintenance operation of the internal combustion engine (1) can be reduced. Furthermore, according to the method described in [1] above, an oil film can be formed on the sliding surface (21) of the cylinder (2) in a short period of time by rotating the rotating shaft (4) at a speed higher than the rotational speed during turning using the electric starter (6). According to the method described in [1] above, by rotating the rotating shaft (4) at high speed using the electric starter (6), it is possible to suppress the scraping off of the oil film formed on the sliding surface (21) of the cylinder (2) by the piston (3), thereby ensuring the thickness of the oil film formed on the sliding surface (21).

[0084] [2] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [1] above, The oil supply device (5) is At least one oil injection nozzle (51) having an injection hole (511) for injecting the oil, An oil introduction line (53) for guiding the oil from the oil supply source (52) to the at least one oil injection nozzle (51), Includes an electric oil pump (P1) for sending the oil from the oil supply source (52) to the at least one oil injection nozzle (51) via the oil introduction line (53), In the oil supply step (S1), the electric oil pump (P1) is driven to inject the oil from the nozzle (511) of the at least one oil injection nozzle (51).

[0085] According to the method described in [2] above, an electric oil pump (P1) is driven to inject oil from the nozzle (511) of at least one oil injection nozzle (51), thereby quickly supplying oil to the sliding surface (21) of the cylinder (2) while the internal combustion engine (1) is stopped.

[0086] [3] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [2] above, The at least one oil injection nozzle (51) is The system includes a first oil injection nozzle (51A) whose injection hole (511) directs the sliding surface (upper sliding surface 21A) located above the central axis (CA) of the cylinder (2) which is inclined with respect to the vertical direction of the cylinder (2).

[0087] According to the method described in [3] above, by injecting oil from the nozzle (511) of the first oil injection nozzle (51A), oil can be supplied to the sliding surface (upper sliding surface 21A) located above the central axis (CA) of the cylinder (2), which is relatively difficult to supply oil to, and an oil film can be formed on the sliding surface (21A). Furthermore, according to the method described in [3] above, a portion of the oil supplied to the upper sliding surface (21A) flows down to the lower sliding surface (21B, the sliding surface located below the central axis CA), thereby more reliably forming an oil film around the entire circumference of the sliding surface (21).

[0088] [4] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [3] above, The at least one oil injection nozzle (51) is The system further includes a second oil injection nozzle (51B) whose injection hole (511) is directed towards the back surface (32) of the piston (3).

[0089] According to the method described in [4] above, by injecting oil from the nozzle (511) of the second oil injection nozzle (51B), the injected oil flows down from the back surface (32) of the piston (3) to the sliding surface (lower sliding surface 21B) located below the central axis (CA) of the cylinder (2), and an oil film can be formed on the sliding surface (21B). The second oil injection nozzle (51B) may be mounted on the internal combustion engine (1) to supply oil to the back surface (32) of the piston (3) during operation of the internal combustion engine (1). By repurposing the second oil injection nozzle (51B) for oil supply during maintenance operation, the complexity of the structure of the internal combustion engine (1) can be suppressed.

[0090] [5] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [4] above, The system further includes an oil injection amount adjustment device (7) configured to adjust the oil injection amount of the first oil injection nozzle (51A) and the oil injection amount of the second oil injection nozzle (51B), In the oil supply step (S1), the oil injection amount adjustment device (7) adjusts the oil injection amount so that the oil injection amount of the first oil injection nozzle (51A) is greater than the oil injection amount of the second oil injection nozzle (51B).

[0091] According to the method described in [5] above, by making the amount of oil injected by the first oil injection nozzle (51A) greater than the amount of oil injected by the second oil injection nozzle (51B), oil can be supplied to the sliding surface (21A) located above the central axis (CA) of the cylinder (2), which is relatively difficult to supply oil to, and an oil film can be formed on the sliding surface (21A). As a result, the maintenance operation method of the internal combustion engine (1) can reliably form an oil film over the entire circumference of the sliding surface (21).

[0092] [6] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [2] above, The at least one oil injection nozzle (51) is The device consists of a wide-angle oil injection nozzle (51C) configured to spray the oil at a wide angle onto the back surface (32) of the piston (3) and the sliding surface (21A) located above the central axis (CA) of the cylinder (2) which is inclined with respect to the vertical direction.

[0093] According to the method described in [6] above, by injecting oil from the nozzle (511) of the wide-angle oil injection nozzle (51C), oil can be supplied to the sliding surface (21A) located above the central axis (CA) of the cylinder (2) and the sliding surface (21B) located below the central axis (CA), respectively, and an oil film can be formed on these sliding surfaces (21A, 21B). As a result, the maintenance operation method of the internal combustion engine (1) can reliably form an oil film around the entire circumference of the sliding surface (21).

[0094] [7] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in [2] above, The at least one oil injection nozzle (51) is The second oil injection nozzle (51B) is directed towards the back surface (32) of the piston (3) by the injection hole (511).

[0095] According to the method described in [7] above, by injecting oil from the nozzle (511) of the second oil injection nozzle (51B), the injected oil flows down from the back surface (32) of the piston (3) to the sliding surface (21B) located below the central axis (CA) of the cylinder (2), and an oil film can be formed on the sliding surface (21B). The second oil injection nozzle (51B) may be mounted on the internal combustion engine (1) to supply oil to the back surface (32) of the piston (3) during operation of the internal combustion engine (1). By reusing the second oil injection nozzle (51B) for oil supply during maintenance operation, the complexity of the structure of the internal combustion engine (1) can be suppressed.

[0096] [8] In some embodiments, a maintenance operation method for an internal combustion engine (1) as described in any of [1] to [7] above, In the cranking step (S2), the cranking is performed intermittently, with periods of inactivity in between.

[0097] According to the method described in [8] above, intermittent cranking can suppress the load on the starter (6) and prevent damage to the starter (6) due to overheating.

[0098] [9] In some embodiments, a maintenance operation method for an internal combustion engine (1) as described in any of [1] to [8] above, The aforementioned cranking step (S2) is, A first rotation step (S21) in which the rotating shaft (4) is rotated at a first rotation speed which is equal to or greater than the predetermined rotation speed, The process includes, after the first rotation step (S21), a second rotation step (S22) in which the rotating shaft (4) is rotated at a second rotation speed exceeding the first rotation speed.

[0099] According to the method described in [9] above, by gradually increasing the rotational speed during the cranking step (S2), wear on the piston (3) and sliding surface (21) can be suppressed while an oil film can be formed on the sliding surface (21) of the cylinder (2) in a short period of time. Specifically, by rotating the rotating shaft (4) at a relatively low first rotational speed in the first rotational step (S21), wear on the piston (3) and sliding surface (21) can be suppressed at the start of rotation when sufficient oil has not been supplied to the sliding surface (21). Furthermore, by rotating the rotating shaft (4) at a relatively high second rotational speed in the second rotational step (S22), the piston (3) can be reciprocated at a relatively high speed when sufficient oil has been supplied to the sliding surface (21).

[0100]

[10] In some embodiments, a maintenance operation method for an internal combustion engine (1) as described in any of [1] to [9] above, The system further includes a temperature acquisition step in which the temperature of the starter (6) is acquired by a starter temperature acquisition device (9) for acquiring the temperature of the starter (6), In the cranking step (S2), if the temperature of the starter (6) obtained in the temperature acquisition step exceeds the first temperature threshold, the cranking is not started.

[0101] According to the method described in

[10] above, if the temperature of the starter (6) exceeds a first temperature threshold, cranking is not started, thereby suppressing damage to the starter (6) due to overheating.

[0102]

[11] In some embodiments, a maintenance operation method for the internal combustion engine (1) described in

[10] above, In the cranking step (S2), if the temperature of the starter (6) obtained in the temperature acquisition step exceeds the second temperature threshold, the cranking that is currently being performed is stopped.

[0103] According to the method described in

[11] above, if the temperature of the starter (6) exceeds the second temperature threshold, the cranking that is in progress is stopped, thereby suppressing damage to the starter (6) due to overheating.

[0104]

[12] In some embodiments, a maintenance operation method for an internal combustion engine (1) described in any of [1] to

[11] above, The internal combustion engine (1) is equipped with a plurality of starters (6), In the cranking step (S2), one of the multiple starters (6) is driven.

[0105] According to the method described in

[12] above, by limiting the starter (6) driven in the cranking step (S2) to one, the probability of failure of the starter (6) that is not used for maintenance operation among the multiple starters (6) can be reduced, thereby ensuring robustness when starting the internal combustion engine (1). [Explanation of Symbols]

[0106] 1. Internal combustion engine 2-cylinder 3 pistons 4-rotation shaft 5. Oil supply device 6 Starters 7. Oil injection volume adjustment device 8. Oil temperature acquisition device 9. Starter temperature acquisition device 9A, 9B, 9C Temperature Sensors 10 Injectors 11 Connecting Rods 12 bearings 13. First drive force transmission device 14 Generators 15. Second drive force transmission device 20 Interior space 20A Combustion Chamber 21 Sliding surface 21A Upper sliding surface 21B Lower sliding surface 22 cubic head 23 Cylinder Block 24 Cylinder Liner 31 Top surface 32 Back side 33 Cylindrical projection 34 Oil passage 35 Oil inlet 36 Oil drain port 41 Crankshaft 42 Transmission shaft 50 Oil Demand Section 51 Oil spray nozzle 51A First oil injection nozzle 51B Second oil injection nozzle 51C Wide-angle oil spray nozzle 52. Sources of oil 53 Oil introduction line 54 Oil cooler 55 Oil Filter 56 Oil introduction line during operation 61 Drive shaft 62 Armatures 63 Field Coil 64 Casing 65 brushes 71. First flow control valve 72. Second flow control valve 73 Valve opening indication device 90 Starter control device 131 Crank-side gear 132 Transmission gear 151 Flywheel 152 External gear 153 Starter-side gear 201 Inner surface 202 Opposing surface 511 nozzles 520 Oil reservoir 531 First oil introduction line 532 Second oil introduction line 533 Branching point 621 Armature Coil 622 commutator CA center axis DP operating period LA1,LA2 extension line P1, P2 Oil Pump S1 Oil supply step S2 Cranking Step S21 First rotation step S22 Second rotation step SP suspension period TH1 First temperature threshold TH2 Second temperature threshold θ injection angle

Claims

1. A maintenance operation method for an internal combustion engine comprising a cylinder and a piston housed so as to be reciprocable along the sliding surface of the cylinder, An oil supply step of supplying oil to the sliding surface of the cylinder by an oil supply device for supplying oil to the sliding surface of the cylinder while the internal combustion engine is stopped, The system includes a cranking step in which the internal combustion engine is cranked while the oil supply step is being performed, In the cranking step, an electric starter is driven to rotate a rotating shaft capable of transmitting driving force to the piston, causing the rotating shaft to rotate at a predetermined rotational speed or higher. Maintenance and operation methods for internal combustion engines.

2. The oil supply device is, At least one oil injection nozzle having an injection hole for injecting the oil, An oil introduction line for guiding the oil from the oil supply source to the at least one oil injection nozzle, Includes an electric oil pump for supplying the oil from the oil source to the at least one oil injection nozzle via the oil introduction line, In the oil supply step, the electric oil pump is driven to inject the oil from the nozzle of the at least one oil injection nozzle. A method for maintaining and operating an internal combustion engine according to claim 1.

3. The at least one oil injection nozzle is The system includes a first oil injection nozzle whose nozzle is directed towards the sliding surface located above the central axis inclined with respect to the vertical direction of the cylinder, A method for maintaining and operating an internal combustion engine according to claim 2.

4. The at least one oil injection nozzle is The system further includes a second oil injection nozzle whose injection hole is directed toward the back surface of the piston. A method for maintaining and operating an internal combustion engine according to claim 3.

5. The system further includes an oil injection amount adjustment device configured to adjust the oil injection amount of the first oil injection nozzle and the oil injection amount of the second oil injection nozzle, In the oil supply step, the oil injection amount adjustment device adjusts the oil injection amount so that the oil injection amount from the first oil injection nozzle is greater than the oil injection amount from the second oil injection nozzle. A method for maintaining and operating an internal combustion engine according to claim 4.

6. The at least one oil injection nozzle is The wide-angle oil injection nozzle is configured to spray the oil at a wide angle onto the back surface of the piston and the sliding surface located above the central axis inclined with respect to the vertical direction of the cylinder. A method for maintaining and operating an internal combustion engine according to claim 2.

7. The at least one oil injection nozzle is The back surface of the piston is directed towards the second oil injection nozzle, A method for maintaining and operating an internal combustion engine according to claim 2.

8. In the cranking step, the cranking is performed intermittently, with a stop period in between during which the cranking does not occur. A method for maintaining and operating an internal combustion engine according to any one of claims 1 to 7.

9. The aforementioned cranking step is A first rotation step in which the rotating shaft is rotated at a first rotation speed which is equal to or greater than the predetermined rotation speed, The process includes, after the first rotation step, a second rotation step in which the rotating shaft is rotated at a second rotation speed exceeding the first rotation speed, A method for maintaining and operating an internal combustion engine according to any one of claims 1 to 7.

10. The system further includes a temperature acquisition step in which the temperature of the starter is acquired by a starter temperature acquisition device for acquiring the temperature of the starter, In the cranking step, if the starter temperature obtained in the temperature acquisition step exceeds a first temperature threshold, the cranking is not started. A method for maintaining and operating an internal combustion engine according to any one of claims 1 to 7.

11. In the cranking step, if the starter temperature obtained in the temperature acquisition step exceeds a second temperature threshold, the cranking that is currently being performed is stopped. A method for maintaining and operating an internal combustion engine according to claim 10.

12. The internal combustion engine is equipped with multiple starters, In the cranking step, one of the multiple starters is driven. A method for maintaining and operating an internal combustion engine according to any one of claims 1 to 7.

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