Internal combustion engine

Abstract

To provide a device improving the startability of an internal combustion engine.SOLUTION: An internal combustion engine is equipped with a crank shaft 31, a first cylinder 7 and a second cylinder 8, and a decompression device that decompresses the first cylinder and the second cylinder after rotation starting and increases the decompression amount of the second cylinder as compared with the decompression amount of the first cylinder. A plurality of valves is provided, which opens and intercepts combustion chambers of the first cylinder and the second cylinder to the outside. The decompression device, in a compression stroke of the internal combustion engine, drives the plurality of valves so as to increase an opening period of the second cylinder, as compared with an opening period of the first cylinder.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an internal combustion engine equipped with a decompression device.

Background Art

[0002] Patent Document 1 discloses a decompression device that reduces the torque required to crank and start an internal combustion engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When starting an internal combustion engine, for example, a starting motor is used. In this case, if the torque of the starting motor is not sufficient, the starting performance of the internal combustion engine deteriorates. Also, depending on the design conditions and usage situation of the internal combustion engine, further shortening of the starting start time may be required.

[0005] Therefore, the present disclosure aims to improve the starting performance of an internal combustion engine.

Means for Solving the Problems

[0006] An internal combustion engine according to an aspect of the present disclosure includes a crankshaft, a first cylinder and a second cylinder, and a decompression device that decompresses the first cylinder and the second cylinder during rotational start more than after rotational start, and makes the decompression amount of the second cylinder larger than the decompression amount of the first cylinder.

Effects of the Invention

[0007] According to an aspect of the present disclosure, the starting performance of an internal combustion engine can be improved.

Brief Description of the Drawings

[0008] [Figure 1] Figure 1 is a schematic diagram of a vehicle according to an embodiment. [Figure 2] Figure 2 is a partial cross-sectional view of the camshaft of the internal combustion engine shown in Figure 1, viewed from the axial direction. [Figure 3] Figure 3 is an external view of the decompression shaft shown in Figure 2. [Figure 4] Figure 4 is an external view of the camshaft shown in Figure 2. [Figure 5] Figure 5 is a cross-sectional view of the camshaft and decompression shaft shown in Figure 2. [Figure 6] Figure 6 shows the state of the weights in the crankshaft shown in Figure 1 when it is rotating at a low speed. [Figure 7] Figure 7 shows the state of the weights when the crankshaft in Figure 1 is rotating at high speed. [Figure 8] Figure 8 is an enlarged cross-sectional view of the third cam and decompressor body shown in Figure 4. [Figure 9] Figure 9 is an enlarged cross-sectional view of the fourth cam and decompressor body shown in Figure 4. [Figure 10] Figure 10 is an enlarged cross-sectional view of the decompressor during the decompression operation shown in Figure 4. [Figure 11] Figure 11 shows the relationship between the rotation angle of the camshaft and the valve lift amount of the internal combustion engine shown in Figure 1. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. The directions described below are based on the direction as seen from the perspective of the vehicle's occupant. Furthermore, the decompression operation described below refers to reducing the compression resistance of the internal combustion engine by reducing the pressure in the cylinders of the internal combustion engine to a level lower than that after rotational starting. Furthermore, rotational starting of the internal combustion engine refers to the rotational starting of the crankshaft of the internal combustion engine by an external force applied to the internal combustion engine. In other words, the rotational starting state refers to the state until the rotational drive of the crankshaft by the explosion of fuel in the cylinders of the internal combustion engine begins. The external force includes, for example, the rotational driving force provided by an electric motor of the driving source, and the external force provided by a person such as an occupant.

[0010] (First Embodiment) Figure 1 is a schematic diagram of a vehicle 1 according to the first embodiment. As shown in Figure 1, the vehicle 1 of this embodiment includes, as an example, a plurality of driving power sources E and M, and drive wheels DW to which the driving force of the driving power sources E and M is transmitted. The plurality of driving power sources E and M include a first driving power source for driving and a second driving power source separate from the first driving power source. The first driving power source in this embodiment is an internal combustion engine E. The second driving power source in this embodiment is an electric motor M. As an example, the vehicle 1 is a hybrid vehicle. The vehicle 1 is configured to be switchable between a first driving mode in which only the electric motor M is used as the driving power source, and a second driving mode in which at least the internal combustion engine E is used as the driving power source. The vehicle 1 of this embodiment is configured so that the internal combustion engine E can be started while the vehicle is running on the electric motor M. As a result, the vehicle 1 is configured to be able to switch the driving mode from the first driving mode to the second driving mode while the vehicle is running in the first driving mode. For example, Vehicle 1 is a saddle-type vehicle that a rider straddles and is a motorcycle.

[0011] Vehicle 1 is equipped with a generator G and a battery B. The generator G generates electricity using the driving force of the internal combustion engine E. In this embodiment, the generator G is, for example, an ISG (Integrated Starter Generator) and also functions as a starter motor that rotates the crankshaft 31 when the internal combustion engine E starts rotating. The battery B is connected to the generator G and the electric motor M and drives the generator G and the electric motor M, which function as a starter motor. The battery B also stores energy using the output of the generator G. The drive wheels DW are driven by the output of the electric motor M in the first driving mode and by at least the output of the internal combustion engine E in the second driving mode. Note that Vehicle 1 is not limited to a motorcycle, but may be a three-wheeled or four-wheeled vehicle, for example. Also, Vehicle 1 may be equipped with only the internal combustion engine E as the driving source.

[0012] The internal combustion engine E of this embodiment includes, as an example, a plurality of pistons 18, a plurality of cylinders 30 arranged corresponding to each piston 18, and a crankshaft 31 that is rotationally driven by the explosion in the combustion chamber 30a (see Figure 2) within the cylinder 30. The plurality of cylinders 30 in this embodiment include a first cylinder 7 and a second cylinder 8. The internal combustion engine E of this embodiment is, as an example, a four-stroke engine. Therefore, during one cycle of the operating period of the internal combustion engine E, the crankshaft 31 rotates twice around its axis. During the aforementioned one cycle, the piston 18 reciprocates between the bottom dead center and the top dead center within the cylinder 30. In the compression stroke, when the piston 18 moves from the bottom dead center to the top dead center, the gas inside the cylinder 30 is compressed, causing the pressure inside the cylinder 30 to rise.

[0013] As will be described in more detail later, the internal combustion engine E is equipped with a decompression device 9 (see Figure 2) that reduces the pressure in the first cylinder 7 and the second cylinder 8 to a level lower than that after rotational starting during engine start-up. In vehicle 1, decompression is achieved by using the decompression device 9. Hereinafter, when the maximum pressure in cylinder 30 compressed during the compression stroke of the internal combustion engine E without decompression is taken as the base pressure, the amount by which the maximum pressure in cylinder 30 compressed during the compression stroke of the internal combustion engine E becomes smaller than the base pressure due to the decompression is expressed as the reduction amount. That is, the larger the reduction amount, the smaller the pressure in cylinder 30 compressed during the compression stroke.

[0014] The decompression device 9 of this embodiment increases the pressure reduction amount of the second cylinder 8 compared to the pressure reduction amount of the first cylinder 7 when the internal combustion engine E is started. As a result, when the internal combustion engine E is started, the total pressure in the cylinders 30 compressed during the compression stroke is smaller compared to when only a single cylinder is depressurized or when the second cylinder 8 is depressurized by the same amount as the first cylinder 7. In other words, when the internal combustion engine E is started, the total compression resistance when compressing the gas in the cylinders 30 during the compression stroke is reduced. This reduces the external force required to start the crankshaft 31, and the internal combustion engine E can be started easily. When the multiple cylinders 30 include three or more cylinders, for example, it is preferable that the multiple cylinders 30 include a single first cylinder 7 and multiple second cylinders 8. In this case, the multiple cylinders 30 include more cylinders with large pressure reduction amounts than cylinders with small pressure reduction amounts.

[0015] The vehicle 1 also includes a control device 14 that controls the combustion state in the second cylinder 8. The control device 14 controls, for example, at least one of an ignition device I provided in the internal combustion engine E to ignite the fuel in the cylinder 30, a fuel injector F provided in the internal combustion engine E to inject fuel into the cylinder 30, and an electronic control throttle T provided in the internal combustion engine E to adjust the intake air amount into the cylinder 30. The control device 14 has a combustion control circuit that controls the combustion state in the cylinder 30. The control device 14 of the present embodiment includes a memory 60 in which a program is stored and a processor 61 that executes the program stored in the memory 60. As an example, the combustion control circuit is realized by the memory 60 and the processor 61. As another example, the control device 14 includes an ECU (Electronic Control Unit).

[0016] The vehicle 1 also includes a transmission TM that changes the output rotational speed of the driving sources E and M for traveling, and a clutch C that connects and disconnects the power transmission path disposed between the internal combustion engine E and the transmission TM. The transmission TM has an input shaft 10 to which a driving force is transmitted from the outside and an output shaft 11 that outputs a driving force to the outside. The transmission TM also has gear trains 12 and 13 disposed on the axes of the input shaft 10 and the output shaft 11. The output of the transmission TM is transmitted from the output shaft 11 to the drive wheels DW via a transmission body 16 provided in the vehicle 1. The transmission body 16 includes, for example, a chain, a belt, or a drive shaft, but the configuration of the transmission body 16 is not limited to this. The generator G is housed in an internal space disposed on one side in the vehicle width direction of the crankcase 20 (see FIG. 2) of the internal combustion engine E. The generator G of the present embodiment has a function of starting the internal combustion engine E, but the configuration of the generator G is not limited to this. For example, the vehicle 1 may include a starter motor that starts the crankshaft 31 rotating separately from the generator G.

[0017] FIG. 2 is a partial cross-sectional view of the camshafts 39, 40 of the internal combustion engine E in FIG. 1 as seen from the axial direction. In FIG. 2, a part of the combustion chamber 30a which is the internal space of the second cylinder 8 and a radial cross-section of the camshafts 39, 40 are shown. As shown in FIG. 2, the internal combustion engine E has a plurality of intake ports 30b and a plurality of exhaust ports 30c. The intake port 30b communicates with an intake passage 5d that is provided in the internal combustion engine E and allows intake air supplied from the outside to flow into the cylinder 30. The exhaust port 30c communicates with an exhaust passage 5e that is provided in the internal combustion engine E and allows exhaust gas discharged from the cylinder 30 to flow outside the internal combustion engine E. The ports 30b, 30c communicate the internal space of the cylinder 30 with the outside. As an example, in the internal combustion engine E, two intake ports 30b and two exhaust ports 30c are arranged for each cylinder 30. The number of ports 30b, 30c arranged for each cylinder 30 is not limited to this.

[0018] The internal combustion engine E includes a plurality of valves that open and close the combustion chamber 30a of the cylinder 30 with respect to the outside. The plurality of valves includes a plurality of intake valves 35 and a plurality of exhaust valves 36. The plurality of intake valves 35 are arranged corresponding to the plurality of intake ports 30b individually. As an example, in the internal combustion engine E, two intake valves 35 and two exhaust valves 36 are arranged for each cylinder 30. The configuration and arrangement of the valves are not limited to this.

[0019] The internal combustion engine E has a valve biasing body 37 that biases the intake valve 35 in a direction that closes the intake port 30b. The intake port 30b is closed by the intake valve 35, which is pressed against the opening periphery of the intake port 30b by the biasing force of the valve biasing body 37. Multiple exhaust valves 36 are arranged corresponding to multiple exhaust ports 30c. The internal combustion engine E also has a valve biasing body 38 that biases the exhaust valve 36 in a direction that closes the exhaust port 30c. The exhaust port 30c is closed by the exhaust valve 36, which is pressed against the opening periphery of the exhaust port 30c by the biasing force of the valve biasing body 38. The biasing bodies 37 and 38 include springs as an example. The configuration of the biasing bodies 37 and 38 is not limited to this. Note that one valve does not open and close the combustion chambers 30a of two or more cylinders 30 to the outside simultaneously.

[0020] The internal combustion engine E also includes a first camshaft 39 and a second camshaft 40 that rotate due to the rotational driving force of the crankshaft 31. The camshafts 39 and 40 each have a shaft body 41 that is rotatably supported and a plurality of cams 42 attached to the shaft body 41. The plurality of cams 42 rotate around a predetermined axis to provide driving force to a plurality of valves. In this embodiment, the plurality of cams 42 rotate together with the shaft body 41 around the axis of the shaft body 41. As an example, the plurality of cams 42 include an intake cam 42X and an exhaust cam 42Y. The intake cam 42X is attached to the first camshaft 39 and is positioned corresponding to the intake valve 35. The exhaust cam 42Y is attached to the second camshaft 40 and is positioned corresponding to the exhaust valve 36. The plurality of cams 42 are arranged such that the cam lobes 42a (see Figure 4) are located at predetermined positions in the circumferential direction of the shaft body 41 in accordance with the opening timing of the corresponding valves among the plurality of valves.

[0021] The second camshaft 40 is, for example, a cylindrical body. A decompression shaft 43, which applies an external force to the decompression body 50 (described later), is inserted inside the second camshaft 40. For example, the second camshaft 40 and the decompression shaft 43 are arranged on the same axis and are individually rotatably supported around the axis of that axis.

[0022] As an example, internal combustion engine E is equipped with valve lifters 44 and 45 attached to valves 35 and 36. The valve lifters 44 and 45 are positioned to be in contact with the cam 42. Valve lifter 45 is also positioned to be in contact with the decompression body 50. The valve lifters 44 and 45 transmit the external forces applied by the cam 42 and the decompression body 50 to the valves 35 and 36. Valve lifters are also called tappets.

[0023] As the first camshaft 39 rotates, the cam lobe 42a of the intake cam 42X presses against the valve lifter 44, transmitting an external force from the intake cam 42X to the intake valve 35 and the biasing body 37. This external force pushes the intake valve 35 downward towards the inside of the cylinder 30, against the elastic force of the biasing body 37. This opens the intake port 30b. As the first camshaft 39 rotates, the cam lobe 42a of the intake cam 42X moves distal to the valve lifter 44, and the external force transmitted to the intake valve 35 and the biasing body 37 disappears. As a result, the intake valve 35 moves due to the biasing force of the biasing body 37, and the intake port 30b is closed again by the intake valve 35.

[0024] Furthermore, as the second camshaft 40 rotates, the cam lobe 42a of the exhaust cam 42Y presses against the valve lifter 45, transmitting an external force from the cam 42 to the exhaust valve 36 and the biasing body 38. This external force pushes the exhaust valve 36 downward towards the inside of the cylinder 30, against the elastic force of the biasing body 38. As a result, the exhaust port 30c is opened. As the second camshaft 40 rotates, the cam lobe 42a of the exhaust cam 42Y moves distal to the valve lifter 44, and the external force transmitted to the exhaust valve 36 and the biasing body 38 disappears. As a result, the exhaust valve 36 moves due to the biasing force of the biasing body 38, and the exhaust port 30c is closed again by the exhaust valve 36.

[0025] Thus, the internal combustion engine E includes, as an example, a valve train 19 having camshafts 39, 40, a cam 42, and biasing bodies 37, 38. The valve train 19 operates a plurality of valves in at least one of the intake stroke and exhaust stroke of the internal combustion engine E. The configuration of the valve train 19 is not limited to this. For example, the valve train 19 may have a configuration in which the cam 42 applies an external force to the valves 35, 36 via a rocker arm.

[0026] The decompression device 9 reduces the pressure in the first cylinder 7 and the second cylinder 8 to a level lower than that after rotational start-up when the internal combustion engine E is started. The decompression device 9 of this embodiment has a plurality of decompression bodies 50 and a shifter 51. The decompression bodies 50 are arranged so as to be able to protrude outward from the outer circumferential surface of a plurality of cams 42. As an example, the decompression device 9 of this embodiment drives the exhaust valve 36 to reduce the compression resistance of cylinder 30 by opening the combustion chamber 30a of cylinder 30 to the outside. For this purpose, the decompression body 50 is arranged on the exhaust cam 42Y so as to be able to protrude toward the exhaust valve 36.

[0027] The decompression units 50 are arranged to correspond individually to the first cylinder 7 and the second cylinder 8. For example, multiple decompression units 50 have the same structure. Also, the internal combustion engine E of this embodiment includes, for example, a single camshaft to which all the decompression units 50 and all the multiple cams 42 corresponding to all the decompression units 50 are attached. The single camshaft in this embodiment is the second camshaft 40. The second camshaft 40 rotates the multiple cams 42, which are exhaust cams 42Y, around the axis of the shaft body 41. The shifter 51 shifts the multiple decompression units 50 between a reference position P1 and a protruding position P2 (see Figure 7), which will be described later, according to the rotational speed of the crankshaft 31. The decompression device 9 of this embodiment has multiple shifters 51 arranged to correspond individually to the multiple decompression units 50.

[0028] Figure 3 is an external view of the decompression shaft 43 shown in Figure 2. The decompression shaft 43 is pivotally supported independently of the second camshaft 40 around its axis and applies an external force to multiple decompression bodies 50 to shift them. As shown in Figure 3, the decompression shaft 43 has a shaft body 48 and a control plate 49 positioned at one axial end of the shaft body 48. The shaft body 48 has a plurality of recesses 48a arranged on its circumferential surface. The plurality of recesses 48a are positioned to correspond individually to the plurality of decompression bodies 50. The plurality of recesses 48a are positioned at different circumferential positions of the shaft body 48. The control plate 49 controls the relative position of the second camshaft 40 and the decompression shaft 43 around its axis by an external force applied from a weight 54 (see Figure 4). The control plate 49 has at least one projection 49a that protrudes outward from the plate surface in the axial direction of the shaft body 48.

[0029] Figure 4 is an external view of the second camshaft 40 of Figure 2. As shown in Figure 4, the second camshaft 40 has a sprocket gear 53 positioned at one axial end of the shaft body 41 and at least one weight 54 positioned in conjunction with the sprocket gear 53. The sprocket gear 53 is fixed to the shaft body 41. The rotational driving force of the crankshaft 31 is transmitted to the sprocket gear 53 by a transmission body 17 (see Figure 6) provided in the internal combustion engine E. The transmission body 17 includes, as an example, a chain, a belt, or a drive shaft, but the configuration of the transmission body 17 is not limited thereto. The sprocket gear 53 is a spur gear. The sprocket gear 53 has at least one shaft body 55 that protrudes outward from the plate surface in the axial direction of the shaft body 41. The second camshaft 40 has the same number of weights 54 and shaft bodies 55.

[0030] The weight 54 is pivotally supported on the shaft 55 so as to be rotatable within a certain angular range around the axis of the shaft 55. In this embodiment, the at least one weight 54 includes a pair of weights 54A and 54B. The at least one shaft 55 includes a shaft 55A that pivotally supports weight 54A and a shaft 55B that pivotally supports weight 54B. The decompression device 9 also has a weight biasing body 56 that biases the pair of weights 54A and 54B toward each other. The pair of weights 54A and 54B are connected by the biasing body 56. The biasing body 56 includes a spring as an example. The configuration of the biasing body 56 is not limited to this.

[0031] Multiple exhaust cams 42Y are arranged spaced apart in the axial direction of the second camshaft 40. The positions of the cam lobes 42a of the multiple exhaust cams 42Y are adjusted in the circumferential direction of the second camshaft 40 so as to apply an external force to the exhaust valve 36 at a predetermined timing. The multiple exhaust cams 42Y include at least two cams arranged in correspondence with the first cylinder 7 and two or more cams arranged in correspondence with the second cylinder 8.

[0032] The multiple exhaust cams 42Y of this embodiment include a total of four cams 42. For example, the multiple exhaust cams 42Y include a pair of cams, a first cam 42A and a second cam 42B, which are arranged in accordance with the first cylinder 7. The multiple exhaust cams 42Y also include a pair of cams, a third cam 42C and a fourth cam 42D, which are arranged in accordance with the second cylinder 8. For example, the positions of the peaks of the cam lobes 42a of the pair of cams 42A and 42B in the circumferential direction of the camshaft 40 coincide. The positions of the peaks of the cam lobes 42a of the pair of cams 42C and 42D in the circumferential direction of the camshaft 40 coincide. In the circumferential direction of the camshaft 40, the positions of the peaks of the cam lobes 42a of the pair of cams 42A and 42B and the positions of the peaks of the cam lobes 42a of the pair of cams 42C and 42D are different from each other. As a result, in the internal combustion engine E, the timing at which the exhaust valves 36 are opened and closed by cams 42C to 42D differs between the first cylinder 7 and the second cylinder 8. The second camshaft 40 may also have other cams besides cams 42A to 42D to open and close the intake valves 35 corresponding to the first cylinder 7 and the second cylinder 8, respectively.

[0033] The multiple exhaust cams 42Y include multiple cams with openings, each having multiple openings 42b arranged on its outer surface. For example, the cams with openings in this embodiment are cams 42B to 42D. There are more cams with openings corresponding to the second cylinder 8 than there are cams with openings corresponding to the first cylinder 7. The multiple openings 42b are arranged individually in correspondence with the multiple decompression bodies 50. The multiple openings 42b are arranged at different circumferential positions on the second camshaft 40. When viewed from the axial direction of the shaft body 41, the first contact surfaces 50a of the decompression bodies 50, which are arranged in correspondence with the openings 42b of cams 42C and cams 42D, are located at positions spaced apart in the circumferential direction of the shaft body 41.

[0034] Figure 5 is a cross-sectional view of the second camshaft 40 and the decompression shaft 43 in Figure 2. Figure 5 shows a cross-section of the shafts 40 and 43 viewed from the radial direction. As shown in Figure 5, a lubrication space S is located radially between the second camshaft 40 and the decompression shaft 43. Lubricating oil is placed in the lubrication space S to lubricate the inner circumferential surface of the second camshaft 40 and the outer circumferential surface of the decompression shaft 43. This lubricating oil is, as an example, the engine oil used to lubricate the crankshaft 31.

[0035] The internal combustion engine E includes a plurality of bearings located inside the camshaft 40 that support the decompression shaft 43. The plurality of bearings in this embodiment include a pair of bearings BR1 and BR2. For example, bearings BR1 and BR2 include needle bearings, but the bearing configuration is not limited thereto. For example, the pair of bearings BR1 and BR2 are arranged corresponding to the axial end and the other axial end of the shaft body 48.

[0036] The second camshaft 40 has a shaft support portion 40a that is located between two adjacent cams among a plurality of cams 42 and rotatably supports the decompression shaft 43. In this embodiment, the shaft support portion 40a is located between the second cam 42B and the third cam 42C. The shaft support portion 40a is, for example, a reduced-diameter portion of the second camshaft 40 in which the inner diameter is partially reduced. The shaft support portion 40a has an inner circumferential surface that extends in the axial direction of the shaft body 48. The inner circumferential surface of the shaft support portion 40a is, for example, a smooth surface. The inner circumferential surface of the shaft support portion 40a faces at least a portion of the outer circumferential surface of the shaft body 48. A portion of the lubricating oil present in the lubrication space S is arranged between the shaft support portion 40a and the decompression shaft 43. This reduces the frictional resistance between the shaft support portion 40a and the decompression shaft 43. In this embodiment, a groove 48c is provided on a portion of the outer circumferential surface of the shaft body 48 facing the shaft support portion 40a, which holds lubricating oil internally. By positioning the shaft support portion 40a between two adjacent cams, the deflection of the decompression shaft 43 due to the reaction force that the decompression body 50 receives from the outside during decompression operation is appropriately suppressed. This allows the decompression body 50 to operate more accurately. The second camshaft 40 may have multiple shaft support portions 40a.

[0037] Figure 6 shows the state of the weight 54 when the crankshaft 31 in Figure 1 is rotating at a low speed. Figure 6 shows the sprocket gear 53 in a plan view. The low-speed rotation state referred to here includes the rotation state of the crankshaft 31 when the internal combustion engine E is starting up. As shown in Figure 6, the sprocket gear 53 has an opening 53a that exposes a pair of projections 49a of the decompression shaft 43 to the outside. The pair of projections 49a are spaced apart radially from the sprocket gear 53. In a plan view of the sprocket gear 53, the weight 54 has an arm 54a that extends from a position where it is pivotally supported on the shaft body 55 and a position spaced apart in the circumferential direction of the sprocket gear 53, towards the projection that is distal to the pair of projections 49a, radially outward from the axis of the decompression shaft 43. The weight 54 has an engagement groove 54b located at the tip of the arm 54a that engages with the projection 49a via the opening 53a.

[0038] As the sprocket gear 53 rotates around the axis of the decompression shaft 43, the pair of weights 54A and 54B rotate together with the sprocket gear 53. This causes a centrifugal force to act on the pair of weights 54A and 54B. Figure 7 shows the state of the weights 54 when the crankshaft 31 is rotating at high speed as shown in Figure 1. The state of high-speed rotation here includes the rotation state of the crankshaft 31 after the internal combustion engine E has started rotating. As shown in Figure 7, the centrifugal force increases as the rotational speed of the crankshaft 31 increases. When the rotational speed of the crankshaft 31 exceeds a predetermined decompression release speed, the centrifugal force becomes greater than the biasing force of the biasing body 56. As a result, the pair of weights 54A and 54B swing away from each other around the axes of the shafts 55A and 55B, against the biasing force of the biasing body 56. At this time, the external force applied by the pair of weights 54A and 54B is transmitted to the decompression shaft 43 via a pair of protrusions 49a that engage with the engagement grooves 54b of the pair of weights 54A and 54B. The decompression shaft 43 rotates within a certain range around the axis of the shaft body 48 due to this external force. As a result, the relative position of the decompression shaft 43 and the second camshaft 40 around the axis changes. In this embodiment, the decompression release speed is set to a predetermined rotational speed of the crankshaft 31 obtained by the rotational start of the internal combustion engine E.

[0039] Furthermore, as the rotational speed of the sprocket gear 53 decreases, the centrifugal force decreases. As a result, the pair of weights 54A and 54B swing toward each other due to the biasing force of the biasing body 56. In this way, the relative position of the second camshaft 40 and the decompression shaft 43 around the axis changes according to the rotational speed of the crankshaft 31. In this embodiment, the relative position of the pair of weights 54A and 54B changes by reciprocating between a first position, where they are closest to each other, as shown in Figure 6, and a second position, where they are furthest apart, as shown in Figure 7, according to the rotational speed of the crankshaft 31.

[0040] As shown in Figure 4, the plurality of decompression bodies 50 in this embodiment include a decompression body 50B arranged in correspondence with the cam 42B. The decompression body 50B is positioned at a predetermined location on the outer circumferential surface of the cam 42B so as to be retractable inward from the outer circumferential surface of the cam 42B. The plurality of decompression bodies 50 in this embodiment also include a pair of decompression bodies 50C, 50D arranged in correspondence with a pair of cams 42C, 42D. The pair of decompression bodies 50C, 50D are positioned at different locations on the outer circumferential surfaces of the pair of cams 42C, 42D so as to be retractable inward from the outer circumferential surfaces of the pair of cams 42C, 42D.

[0041] In this embodiment, the arrangement of the decompression unit 50B relative to cam 42B and the arrangement of the decompression unit 50C relative to cam 42C are set similarly, while the arrangement of the decompression units 50B and 50C relative to cams 42B and 42C and the arrangement of the decompression unit 50D relative to cam 42D are set differently. Note that the decompression unit 50 is not provided for cam 42A.

[0042] Figure 8 is an enlarged cross-sectional view of the third cam 42C and decompression body 50C in Figure 4. Figure 9 is an enlarged cross-sectional view of the fourth cam 42D and decompression body 50D in Figure 4. In Figures 8 and 9, the decompression bodies 50C and 50D positioned at the reference position P1 are shown by dashed lines, and the decompression bodies 50C and 50D positioned at the protruding position P2 are shown by solid lines. In this embodiment, the basic configuration including the decompression bodies 50B to 50D and the shifter 51 is the same. Therefore, the configuration shown in Figure 8 will be described as an example for the decompression bodies 50B to 50D and the shifter 51.

[0043] As shown in Figure 8, the shifter 51 has a sleeve 57 and a decompression biaser 58. The sleeve 57 is located in the internal space of a recess 42c, which is located on the outer circumferential surface of the cam 42 in a region substantially opposite to the cam lobe 42a. The recess 42c is in communication with an opening 42b. A decompression body 50C is inserted through the sleeve 57. The sleeve 57 has an opening 57a that exposes a portion of the decompression body 50C, which is located at a protruding position P2, to the outside. The sleeve 57 guides the movement of the decompression body 50C between a reference position P1 located inside the cam 42 and a protruding position P2 that protrudes outward from the outer circumferential surface of the cam 42 from the reference position P1. The decompression biaser 58 biases the decompression body 50C from the protruding position P2 toward the reference position P1 within the sleeve 57. The biaser 58 includes, for example, a spring. The configuration of the biaser 58 is not limited to this.

[0044] The decompression body 50C has a cylindrical shape. The decompression body 50C extends radially along the shaft body 48. In this embodiment, the decompression body 50C also extends axially along the sleeve 57. The decompression body 50C has a first contact surface 50a located at one longitudinal end that contacts the valve lifter 45, and a second contact surface 50b located at the other longitudinal end that contacts the decompression shaft 43. Viewed from the axial direction of the shaft body 48, the first contact surface 50a has, for example, an arc shape in which the center protrudes outward more than both ends. The second contact surface 50b alternately contacts the bottom surface within the recess 48a of the shaft body 48 and the circumferential surface 48b located outward from both sides of the bottom surface in the circumferential direction of the shaft body 48 as the decompression shaft 43 rotates around its axis. The decompression body 50C also has an engagement portion 50c that engages with the biasing body 58. The engaging portion 50c, for example, has a plate-like shape extending radially from the decompression body 50C. In this embodiment, the biasing body 58, when inserted through the decompression body 50C, is in contact with the opening periphery of the sleeve 57 and the plate surface of the engaging portion 50c.

[0045] As shown in Figure 9, the decompression body 50D is positioned so as to protrude outward from the fourth cam 42D from a position offset in the circumferential direction of the fourth cam 42D, with respect to the position on the outer circumferential surface of the fourth cam 42D opposite to the top of the cam lobe 42a. In this embodiment, as an example, when viewed from the axial direction of the decompression shaft 43, the decompression bodies 50C and 50D are positioned within the same region of the internal area of ​​the cams 42C and 42D that is divided by a straight line L1 passing through the top of the cam lobe 42a of the cams 42C and 42D and the axis of the decompression shaft 43. Also as an example, the inclination angle θ1 (see Figure 8) of the axis L2 of the decompression body 50C with respect to the straight line L1 is smaller than the inclination angle θ2 (see Figure 9) of the axis L3 of the decompression body 50D with respect to the straight line L1. The inclination angles θ1 and θ2 are not limited to these and can be adjusted as appropriate.

[0046] Figure 10 is an enlarged cross-sectional view of the decompression body 50 during the decompression operation shown in Figure 4. Figure 10 shows a decompression body 50D positioned at the protruding position P2 as an example. In Figure 10, the valve lifter 45 is shown by a dashed line when the decompression body 50D is positioned at the reference position P1. As shown in Figure 10, when the second contact surface 50b of the decompression body 50 contacts the circumferential surface 48b of the shaft body 48, the external force applied from the shaft body 48 is transmitted to the decompression body 50 and the biasing body 58. Due to this external force, the decompression body 50 moves from the reference position P1 (see Figure 9) to the protruding position P2, while resisting the elastic force of the biasing body 58. Also, when the second contact surface 50b of the decompression body 50 contacts the bottom surface of the recess 48a of the shaft body 48, the external force applied from the decompression shaft 43 to the decompression body 50 and the biasing body 58 is reduced or disappears. As a result, the decompressor 50 moves from the protruding position P2 to the reference position P1 due to the elastic force of the biasing body 58.

[0047] Thus, the positions P1 and P2 of the decompression body 50 change depending on the relative position of the decompression shaft 43 and the decompression body 50 in the circumferential direction of the decompression shaft 43. In this embodiment, the decompression body 50 is positioned at the protruding position P2 when the pair of weights 54A and 54B are positioned at the first position, and the decompression body 50 is positioned at the reference position P1 when the pair of weights 54A and 54B are positioned at the second position, with a plurality of recesses 48a on the decompression shaft 43.

[0048] Furthermore, when the decompression body 50 is in the protruding position P2, the decompression body 50 protrudes outward from the outer circumferential surface of the cam 42, and the first contact surface 50a contacts the surface of the valve lifter 45. As a result, the external force from the decompression body 50 is transmitted to the exhaust valve 36 and the biasing body 38 via the valve lifter 45. This causes the exhaust valve 36 to be pushed down toward the inside of the cylinder 30 against the elastic force of the biasing body 38, and the exhaust port 30c is opened. The internal space of the cylinder 30 becomes in communication with the outside, and the gas inside the cylinder 30 is discharged from the exhaust port 30c. This suppresses the pressure rise inside the cylinder 30. Also, the pressure inside the cylinder 30 decreases relative to the base pressure. As a result, the compression resistance of the internal combustion engine E is reduced.

[0049] Furthermore, when the decompression unit 50 is in the reference position P1, the first contact surface 50a becomes non-contact with the surface of the valve lifter 45. As a result, the external force transmitted from the decompression unit 50 to the exhaust valve 36 and the biasing body 38 disappears. Consequently, the exhaust valve 36 moves due to the biasing force of the biasing body 38, and the exhaust port 30c is closed again. The exhaust port 30c is no longer opened by the decompression unit 50.

[0050] Based on the above operations, when the rotational speed of the crankshaft 31 obtained by the rotational start of the internal combustion engine E is less than or equal to the predetermined speed, in other words, when the internal combustion engine E is rotationally started, the weights 54A and 54B are positioned in the first position and the decompression body 50 is positioned in the protruding position P2. Accordingly, the exhaust port 30c is opened by the decompression body 50, thereby realizing the decompression operation. Furthermore, when the rotational speed of the crankshaft 31 exceeds the predetermined speed, in other words, after the rotational start of the internal combustion engine E, the weights 54A and 54B are positioned in the second position and the decompression body 50 is positioned in the reference position P1. Accordingly, the operation of opening the exhaust port 30c by the decompression operation ends.

[0051] In this embodiment, during the operation of the decompression unit 50, the decompression shaft 43 is appropriately supported by the shaft support portion 40a in the vicinity of the decompression units 50B and 50C. This prevents the decompression shaft 43 from bending due to external forces such as the reaction force received by the decompression unit 50 from the valve lifter 45. Therefore, the external force applied from the decompression shaft 43 can be appropriately transmitted to the decompression unit 50. Thus, accurate decompression operation is achieved.

[0052] In this embodiment, as an example, the number of decompression bodies 50 arranged in accordance with the second cylinder 8 is greater than the number of decompression bodies 50 arranged in accordance with the first cylinder 7. In this embodiment, the multiple decompression bodies 50 arranged in accordance with the second cylinder 8 are arranged with a phase difference around the axis of the camshaft 40 (see Figure 4). As a result, in the second cylinder 8, the opening period during which the exhaust port 30c is opened by the decompression body 50, i.e., the valve opening period, can be increased compared to the first cylinder 7. This allows the compression resistance to be reduced in the second cylinder 8 by the decompression body 50 compared to the first cylinder 7.

[0053] Thus, the decompression device 9 drives multiple valves to make the amount of pressure reduction in the second cylinder 8 greater than the amount of pressure reduction in the first cylinder 7. For example, during the compression stroke of the internal combustion engine E, it drives multiple valves to make the opening period of the second cylinder 8 greater than the opening period of the first cylinder 7.

[0054] The following describes an example of valve drive by the decompression device 9. Figure 11 shows the relationship between the rotation angles of the camshafts 39 and 40 of the internal combustion engine E in Figure 1 and the lift amounts of the valves 35 and 36. In Figure 11, the graph shown at the top corresponds to the first cylinder 7, and the graph shown at the bottom corresponds to the second cylinder 8. The vertical axis of each graph shows the change in the lift amount of the intake valve 35 and the exhaust valve 36. The horizontal axis of each graph shows the range of rotation angles around the axis of the camshaft 40, which rotates twice during one cycle of the operating cycle of the internal combustion engine E, relative to a predetermined reference angle.

[0055] In Figure 11, the lift amount of the exhaust valve 36 due to the decompression unit 50B is shown by graph line BL1. The lift amount of the exhaust valve 36 due to the decompression unit 50C is shown by graph line BL2. The lift amount of the exhaust valve 36 due to the decompression unit 50D is shown by graph line BL3. Figure 11 also shows the compression period Q0 in each graph when there is no decompression operation. In Figure 11, for convenience, the lift timing of the intake valve 35 due to cam 42X and the lift timing of the exhaust valve 36 due to cam 42Y are set to match in the first cylinder 7 and the second cylinder 8. In this embodiment, the respective lift timings are actually set to be offset from each other.

[0056] As shown in Figure 11, in the internal combustion engine E of this embodiment, decompression is performed using the exhaust valve 36 in both the first cylinder 7 and the second cylinder 8 during one cycle of the operating period. For example, the number of decompression operations corresponding to the second cylinder 8 during one cycle is greater than the number of decompression operations corresponding to the first cylinder 7 during the same cycle. In this embodiment, multiple decompression operations are performed on the second cylinder 8 during one cycle. These multiple decompression operations include two decompression operations, but may include three or more decompression operations.

[0057] In this embodiment, with the number of decompression operations set as described above, the valve opening period corresponding to the second cylinder 8 during one cycle is longer than the valve opening period corresponding to the first cylinder 7 during one cycle. In other words, the compression period Q2 of the decompression operation corresponding to the second cylinder 8 during one cycle is shorter than the compression period Q1 of the decompression operation corresponding to the first cylinder 7 during one cycle.

[0058] As a result, in the internal combustion engine E, the internal pressure of the first cylinder 7 and the second cylinder 8 is reduced during rotational starting compared to after rotational starting. Furthermore, during one cycle, the amount of pressure reduction in the second cylinder 8 is increased compared to the amount of pressure reduction in the first cylinder 7. This allows, for example, the rotational driving force of the internal combustion engine E to be obtained by combustion in the combustion chamber 30a of the first cylinder 7, while reducing the compression resistance of the second cylinder 8 to that of the first cylinder 7, thereby reducing the overall compression resistance of the internal combustion engine E. As a result, the rotational starting performance of the internal combustion engine E is improved.

[0059] For example, when an ISG is used as the starting motor for an internal combustion engine E, the low torque of the starting motor may necessitate improved starting performance for the internal combustion engine E. Furthermore, improved starting performance may also be required for the internal combustion engine E depending on the design conditions and usage conditions. These usage conditions include, for example, when restarting the internal combustion engine E from an idle stop state, or when switching the driving mode from the first driving mode to the second driving mode while the vehicle 1 is in motion to rapidly start the internal combustion engine E. According to this embodiment, the decompression device 9 improves the rotational starting performance of the internal combustion engine E, allowing the rotational speed of the internal combustion engine E to increase in a short time from the start of starting. Therefore, these situations can be dealt with appropriately. Also, when starting the internal combustion engine E by switching the driving mode from the first driving mode to the second driving mode while the vehicle 1 is in motion, it is possible to prevent a decrease in the driving feeling perceived by the occupant of the vehicle 1 due to the rotational speed of the internal combustion engine E not increasing sufficiently. Furthermore, according to this embodiment, the decompression device 9 operates automatically in accordance with the rotational speed of the crankshaft 31. Therefore, for example, when starting the internal combustion engine E, the user of the internal combustion engine E or the passengers of the vehicle 1 do not need to perform an operation to reduce the compression resistance of the second cylinder 8 to that of the first cylinder 7.

[0060] Furthermore, in this embodiment, the multiple decompression bodies 50, which are arranged in accordance with the second cylinder 8, are positioned with a phase difference around the axis of the camshaft 40. As a result, as can be seen from the graph lines BL2 and BL3, there is a gap between the preceding decompression operation and the subsequent decompression operation among the multiple decompression operations in one cycle.

[0061] The timing of multiple decompression operations is adjusted by the positions of multiple recesses 48a in the circumferential direction of the decompression shaft 43. For example, increasing the spacing between the multiple recesses 48a in the circumferential direction of the decompression shaft 43, as viewed from the axial direction of the decompression shaft 43, extends the time between a preceding decompression operation and another subsequent decompression operation. Conversely, decreasing the spacing between the multiple recesses 48a shortens the time between a preceding decompression operation and another subsequent decompression operation. Furthermore, arranging the multiple recesses 48a in the circumferential direction of the decompression shaft 43 so that they partially overlap, as viewed from the axial direction of the decompression shaft 43, can extend the time for each individual decompression operation. In this embodiment, as an example, there is a timing in which the intake valve 35 and the exhaust valve 36 are opened simultaneously during multiple decompression operations in one cycle. Multiple decompression operations in one cycle may also be performed at timings when the intake valve 35 is not opened.

[0062] Furthermore, the multiple decompression bodies 50 may include, for example, decompression bodies 50 having different shapes. In this case, for example, the shape of the decompression body 50 arranged in accordance with the first cylinder 7 and the shape of the decompression body 50 arranged in accordance with the second cylinder 8 may be different. Also, in this embodiment, one decompression body 50 is arranged for one cam 42, but two or more decompression bodies 50 may be arranged for one cam 42. In this case, two or more decompression bodies 50 may be arranged at a distance from the outer circumferential surface of one cam 42 at a position spaced apart from the cam lobe 42a of the cam 42, and spaced apart in the circumferential direction of the cam 42. Also, in this embodiment, the external force applied from the decompression body 50 is transmitted to the exhaust valve 36, which opens the exhaust port 30c and performs the decompression operation, but the external force applied from the decompression body 50 may be transmitted to the intake valve 35, which opens the intake port 30b and performs the decompression operation.

[0063] Furthermore, the method by which the decompression device 9 increases the amount of pressure reduction in the second cylinder 8 compared to the amount of pressure reduction in the first cylinder 7 is not limited to a method of driving multiple valves so that the open period of the second cylinder 8 is greater than the open period of the first cylinder 7 during the compression stroke of the internal combustion engine E. For example, the decompression device 9 may drive multiple valves so that the lift amount of the valves corresponding to the second cylinder 8 is greater than the lift amount of the valves corresponding to the first cylinder 7 during the compression stroke of the internal combustion engine E.

[0064] The valve lift amount referred to here, in other words, refers to the amount by which ports 30b and 30c are opened by valves 35 and 36, for example. The amount by which ports 30b and 30c are opened is proportional to the flow rate of gas passing through ports 30b and 30c per unit time within a certain range. The decompression device 9 can increase the valve lift amount by adjusting the protrusion position P2 of the decompression body 50 so as to increase the amount of the decompression body 50 protruding from the outer surface of the cam 42.

[0065] Furthermore, as a method for the decompression device 9 to make the amount of pressure reduction in the second cylinder 8 greater than the amount of pressure reduction in the first cylinder 7, for example, the opening diameters of the ports 30b and 30c of the second cylinder 8 may be made larger than the opening diameters of the ports 30b and 30c of the first cylinder 7.

[0066] The internal combustion engine E may also have a single cylinder 30. In this case, the multiple decompression bodies 50 may be positioned at different positions on the outer circumferential surfaces of the pair of cams 42C and 42D around the axis of the shaft body 41 of the pair of cams 42C and 42D, and may be retractable inward from the outer circumferential surfaces of the pair of cams 42C and 42D. This makes it easier to obtain the force necessary to start the crankshaft 31 when starting the internal combustion engine, thereby improving the starting performance of the internal combustion engine E. The first and second modifications of this embodiment will be described below.

[0067] (First variation) The vehicle according to the first modified example is a series hybrid vehicle. This vehicle includes a generator G that generates electricity using the driving force of an internal combustion engine E, an electric motor M for driving driven by the output of the generator G, and drive wheels DW driven by the output of the electric motor M. This vehicle also includes a storage battery B connected to the generator G and the electric motor M. The storage battery B is charged by the output of at least one of the generator G and the electric motor M. The storage battery B supplies power to the electric motor M while driving. The internal combustion engine E is equipped with a decompression device 9 similar to that of the first embodiment.

[0068] The vehicle according to the first modified example also achieves the same effects as vehicle 1 of the first embodiment. Furthermore, even when the output of the generator G, which generates electricity using the driving force of the internal combustion engine E, drives the electric motor M for driving, and the electric motor M drives the drive wheels DW, the starting performance of the internal combustion engine E is improved, allowing the vehicle to be brought into a state where it can be driven quickly. Similar effects can also be obtained when the crankshaft 31 is rotated and started by an external force applied by a person.

[0069] (Second variation) In the vehicle according to the second modification, the control device 14 further controls the combustion state in the second cylinder 8 so that the combustion state in the second cylinder 8 differs between when the internal combustion engine E is starting up and after the internal combustion engine E has started up. For example, the control device 14 controls the combustion state in the second cylinder 8 when the internal combustion engine E is starting up to be milder than the combustion state in the second cylinder 8 after the internal combustion engine E has started up. "Controlling to be milder" here includes, for example, controlling the fuel injector F to reduce the amount of fuel supplied to the second cylinder 8. It also includes, for example, controlling the electronically controlled throttle T to reduce the amount of intake air to the second cylinder 8. It also includes, for example, controlling the ignition device I to stop the combustion of the second cylinder 8. After the internal combustion engine E has started up, the control device 14 controls the combustion state of the first cylinder 7 and the second cylinder 8 in the same manner.

[0070] The same effects as in the first embodiment can be obtained in the vehicle according to the second modified example. Furthermore, by using the control device 14 that controls the combustion state in the second cylinder 8, for example, when the internal combustion engine E is started, the combustion of fuel in the second cylinder 8 is stopped, the fuel supply to the second cylinder 8 is stopped, or the scale of combustion in the second cylinder 8 is reduced compared to that after starting. As a result, the fuel consumption of the internal combustion engine E can be saved, and the outflow of unburned gas from the second cylinder 8 to the outside can be suppressed or avoided. The second embodiment will now be described, focusing on the differences from the first embodiment.

[0071] (Second Embodiment) The internal combustion engine E of the vehicle according to the second embodiment includes a decompression device 9 having the same number of decompression bodies 50 arranged corresponding to the first cylinder 7 and the second cylinder 8. The decompression device 9 includes a camshaft, which is a cylindrical body to which a pair of cams are attached, and a decompression shaft, which is inserted inside the camshaft and pivotally supported independently of the camshaft so as to rotate around the axis of the camshaft, and which applies an external force to the multiple decompression bodies 50 to shift the decompression bodies 50.

[0072] The decompression device 9 of the second embodiment has a second camshaft 40 to which a pair of cams, a second cam 42B and a third cam 42C, are attached. The decompression device 9 also has, as an example, a decompression body 50B positioned corresponding to the second cam 42B and a decompression body 50C positioned corresponding to the third cam 42C. The second camshaft 40 has a shaft support portion 40a positioned between the pair of cams that rotatably supports the decompression shaft 43 (see Figure 5). In the decompression device 9 of the second embodiment, as an example, the decompression body 50D is omitted. The shaft support portion 40a of the second embodiment has the same configuration as that of the first embodiment.

[0073] In the internal combustion engine E of the second embodiment, the decompression shaft 43 is appropriately supported by the shaft support portion 40a near the decompression bodies 50B and 50C. This prevents the decompression shaft 43 from bending inside the second camshaft 40 due to external forces such as the reaction force received by the decompression body 50 from the valve lifter 45. Therefore, the decompression shaft 43 is stably supported by the second camshaft 40. As a result, the external force applied from the decompression shaft 43 can be appropriately transmitted to the decompression body 50, and the decompression body 50 can be moved accurately between the reference position P1 and the protruding position P2. This prevents insufficient protrusion of the decompression body 50 and realizes accurate decompression operation. Therefore, when the internal combustion engine E is started up, it is possible to prevent insufficient reduction of the compression resistance of the internal combustion engine E due to improper decompression operation. As a result, the rotational starting performance of the internal combustion engine E is improved. A third modified example, which is a modification of the second embodiment, will be described below.

[0074] (Third variation) The internal combustion engine E of the vehicle according to the third modified example comprises a single cylinder 30. The decompression device 9 of this internal combustion engine E has a second camshaft 40 to which a third cam 42C and a fourth cam 43D are attached as a pair of cams. The second camshaft 40 has a shaft support portion 40a located between these pair of cams that rotatably supports the decompression shaft 43. That is, the shaft support portion of this modified example is positioned correspondingly between the third cam 42C and the fourth cam 43D.

[0075] In the vehicle of the third modified example having the above configuration, the same effects as in the second embodiment are achieved. That is, the bending of the decompression shaft 43 inside the second camshaft 40 is suppressed by external forces such as the reaction force that the decompression body 50 receives from the valve lifter 45, so that the external force applied from the decompression shaft 43 can be appropriately transmitted to the decompression body 50. As a result, accurate decompression operation is achieved.

[0076] As described above, embodiments and modifications have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited thereto and can be applied to embodiments that have been modified, replaced, added, omitted, etc. as appropriate. Furthermore, it is possible to combine the components described in the embodiments and modifications to create new embodiments. For example, some components in one embodiment may be applied to other components, and some components in an embodiment can be separated from other components in that embodiment and extracted as appropriate. In addition, the components described in the attached drawings and detailed description include not only components that are essential for solving the problem, but also components that are not essential for solving the problem, in order to illustrate the technology.

[0077] (Disclosure items) Each of the following items is a disclosure of a preferred embodiment.

[0078] [Item 1] Crankshaft and The first cylinder and the second cylinder, An internal combustion engine comprising a decompression device that, during rotational starting, reduces the pressure of the first cylinder and the second cylinder compared to after rotational starting, and increases the pressure reduction of the second cylinder compared to the pressure reduction of the first cylinder.

[0079] According to the above configuration, when the internal combustion engine is started, the decompression device reduces the pressure in both the first and second cylinders to levels lower than those after starting. This reduces the compression resistance during the starting of the internal combustion engine compared to when only a single cylinder is reduced to levels lower than those after starting. Furthermore, the first cylinder, which has a smaller pressure reduction than the second cylinder, can have a higher explosive force during combustion. This makes it easier to generate the force necessary to rotate the crankshaft. In other words, the second cylinder, which has a larger pressure reduction than the first cylinder, requires less force to rotate the crankshaft. Therefore, the pressure reduction in the second cylinder can be further increased compared to the first cylinder. Thus, the effect of reducing compression resistance can be enhanced. As a result, when the internal combustion engine is started, the force necessary to rotate the crankshaft can be obtained, and compression resistance can be further reduced.

[0080] [Item 2] The combustion chambers of the first cylinder and the second cylinder are provided with a plurality of valves for opening and closing them to the outside, The internal combustion engine according to item 1, wherein the decompression device drives the plurality of valves such that the opening period of the second cylinder is greater than the opening period of the first cylinder during the compression stroke of the internal combustion engine.

[0081] According to the above configuration, when the internal combustion engine starts up, the decompression device drives multiple valves, thereby increasing the pressure reduction in the second cylinder compared to the pressure reduction in the first cylinder. Furthermore, during the compression stroke of the internal combustion engine, the decompression device makes the opening periods of the first and second cylinders different, thereby increasing the pressure reduction in the second cylinder compared to the first cylinder. This minimizes the impact on strokes other than the compression stroke of the internal combustion engine while increasing the pressure reduction in the second cylinder.

[0082] [Item 3] Multiple valves that open and close the combustion chambers of the first and second cylinders to the outside, It comprises a plurality of cams that rotate around a predetermined axis and provide driving force to the plurality of valves, The decompression device is, A plurality of decompression bodies are arranged to correspond individually to the first cylinder and the second cylinder, and are configured to be shiftable between a reference position located inside the plurality of cams and a protruding position that protrudes outward from the outer circumferential surface of the plurality of cams from the reference position, An internal combustion engine according to item 1 or 2, comprising a shifter that shifts the plurality of decompression bodies between the reference position and the protruding position in accordance with the rotational speed of the crankshaft.

[0083] According to the above configuration, the amount of protrusion of the decompression body from the outer circumference of the cam can be changed according to the rotational speed of the crankshaft. This allows the valve opening time to be extended during the rotational start of the internal combustion engine compared to after the engine has started. In addition, the amount of pressure reduction between the first and second cylinders during the rotational start of the internal combustion engine can be easily adjusted by the decompression bodies, which are individually positioned to correspond to the first and second cylinders.

[0084] [Item 4] The internal combustion engine according to item 3, wherein the number of decompression bodies arranged in accordance with the second cylinder is greater than the number of decompression bodies arranged in accordance with the first cylinder.

[0085] According to the above configuration, during rotational starting of the internal combustion engine, the composite unit including the cam and decompression body positioned for the second cylinder can be made larger than the composite unit including the cam and decompression body positioned for the first cylinder. This makes it easier to increase the pressure reduction amount in the second cylinder compared to the first cylinder.

[0086] [Item 5] The plurality of cams include a pair of cams arranged in accordance with the second cylinder, The internal combustion engine according to item 3 or 4, wherein the plurality of decompression bodies include a pair of decompression bodies arranged in correspondence with the pair of cams.

[0087] According to the above configuration, for example, it is easier to arrange the decompression bodies in relation to a cam compared to arranging multiple decompression bodies in relation to a single cam. This makes it easier to house the decompression bodies inside the cam, for example. As a result, the assembly of the internal combustion engine can be simplified.

[0088] [Item 6] The internal combustion engine according to item 5, wherein the pair of decompression bodies are positioned at different positions on the outer circumferential surfaces of the pair of cams so as to be retractable inward from the outer circumferential surfaces of the pair of cams.

[0089] According to the above configuration, a pair of decompression bodies, positioned to be retractable inward from the outer circumferential surface of a pair of cams, can be used to operate the valves corresponding to the second cylinder at different timings. This increases the valve opening period for the entire second cylinder during rotational startup of the internal combustion engine. Furthermore, compared to, for example, a case where a pair of decompression bodies are positioned to be retractable inward from the outer circumferential surface of a single cam, the external shape of the composite including the cams and decompression bodies can be suppressed to lessen compared to the external shape of the cams alone. Therefore, the internal combustion engine can be manufactured more easily.

[0090] [Item 7] The aforementioned multiple decompression bodies are internal combustion engines according to any one of items 3 to 6, having the same structure.

[0091] According to the above configuration, the parts of the internal combustion engine can be standardized. Therefore, by reducing the number of parts, the manufacturing cost of the internal combustion engine can be reduced.

[0092] [Item 8] An internal combustion engine according to any one of items 3 to 7, comprising a single camshaft from which all of the decompression bodies and all of the plurality of cams corresponding to all of the decompression bodies are mounted.

[0093] According to the above configuration, the camshafts to which the cams that position multiple decompression bodies are attached can be consolidated. This makes it easy to standardize the configuration of the shifter that shifts the multiple decompression bodies between a reference position and a protruding position. Therefore, the structure of the internal combustion engine can be simplified compared to, for example, a case where at least two or more decompression bodies are individually positioned corresponding to multiple camshafts.

[0094] [Item 9] The decompression device is, The camshaft is a cylindrical body to which the aforementioned multiple cams are attached, The system includes a decompression shaft inserted inside the camshaft, which is pivotally supported independently of the camshaft so as to rotate independently of the camshaft's axis, and which applies an external force to the plurality of decompression bodies to shift the decompression bodies. The internal combustion engine according to any one of items 3 to 8, wherein the camshaft has a shaft support portion located between two adjacent cams among the plurality of cams, which rotatably supports the decompression shaft.

[0095] According to the above configuration, during the operation of the decompressor body, the decompressor shaft is properly supported near the decompressor body by the shaft support portion located between two adjacent cams among the plurality of cams. This prevents the decompressor shaft from bending due to external forces acting on the decompressor body. Therefore, the external force applied from the decompressor shaft can be properly transmitted to the decompressor body. This enables accurate decompression. Consequently, it is possible to prevent insufficient reduction of the compression resistance of the internal combustion engine E due to improper decompression during rotational startup of the internal combustion engine.

[0096] [Item 10] An internal combustion engine according to any one of items 1 to 9, further comprising a control device for controlling the combustion state such that the combustion state in the second cylinder differs between the rotational start of the internal combustion engine and after the rotational start of the internal combustion engine.

[0097] According to the above configuration, by using a control device that controls the combustion state in the second cylinder, for example, when starting the internal combustion engine, the combustion of fuel in the second cylinder may be stopped, the fuel supply to the second cylinder may be stopped, or the scale of combustion in the second cylinder may be reduced compared to that after starting. This makes it possible to save fuel consumption in the internal combustion engine and to suppress or avoid the leakage of unburned gases from the second cylinder to the outside.

[0098] [Item 11] An internal combustion engine according to any one of items 1 to 10, further comprising a starter motor that generates electricity using the driving force of the crankshaft and rotates the crankshaft when the internal combustion engine is started.

[0099] Here, an ISG motor can be used as the starting motor. Such a starting motor has a different gear shifting structure compared to a motor that does not have a power generation function. For this reason, if the power generation function of the starting motor is prioritized, the starting torque may be small. In contrast, with the above configuration, when starting the rotation of the internal combustion engine, the force necessary to rotate the crankshaft can be obtained, and the compression resistance can be further reduced, so that even if the starting torque of the starting motor is small, the crankshaft can be rotated quickly. Thus, the starting performance of an internal combustion engine with multiple cylinders can be improved.

[0100] [Item 12] Crankshaft and Cylinders and, Multiple valves that open and close the combustion chamber of the cylinder to the outside, A decompression device that reduces the pressure of the cylinder during rotational startup compared to after rotational startup, It comprises a pair of cams that rotate around a predetermined axis and provide driving force to the plurality of valves, The decompression device is, It has a plurality of decompression bodies arranged corresponding to the cylinders and configured to be shiftable between a reference position located inside the pair of cams and a protruding position that protrudes outward from the outer circumferential surface of the pair of cams from the reference position, An internal combustion engine in which the plurality of decompression bodies are arranged to be retractable inward from the outer surface of the pair of cams at positions on the outer surfaces of the pair of cams that are different from each other on the outer surfaces of the pair of cams.

[0101] According to the above configuration, when starting an internal combustion engine, the force required to start the crankshaft can be easily obtained by operating multiple decompression units of the decompression device at different timings. Furthermore, it becomes easier to further reduce compression resistance when starting an internal combustion engine. As a result, the starting performance of the internal combustion engine can be improved.

[0102] [Item 13] The decompression device is, A camshaft is a cylindrical body to which the pair of cams are attached, The system includes a decompression shaft inserted inside the camshaft, which is pivotally supported independently of the camshaft so as to rotate independently of the camshaft's axis, and which applies an external force to the plurality of decompression bodies to shift the decompression bodies. The internal combustion engine according to item 12, wherein the camshaft has a shaft support portion located between the pair of cams that rotatably supports the decompression shaft.

[0103] According to the above configuration, during the operation of the decompressor body, the decompressor shaft is properly supported near the decompressor body by the shaft support located between the pair of cams. This prevents the decompressor shaft from bending due to external forces acting on the decompressor body. Therefore, the external force applied from the decompressor shaft can be properly transmitted to the decompressor body. This enables accurate decompression. Consequently, it is possible to prevent insufficient reduction of the compression resistance of the internal combustion engine E due to improper decompression during rotational starting of the internal combustion engine.

[0104] [Item 14] A first drive source for driving, which is the internal combustion engine described in any one of items 1 to 13, It comprises a second drive source for driving, separate from the first drive source, A vehicle in which the first drive source is configured to be able to be started while the vehicle is being driven by the second drive source.

[0105] According to the above configuration, in a vehicle equipped with a first drive source, which is an internal combustion engine having multiple cylinders, and a second drive source for driving separate from the first drive source, the starting performance of the first drive source while driving on the second drive source is improved. As a result, the starting of the first drive source can be expedited while driving on the second drive source. Consequently, when switching from a driving mode using the second drive source to a driving mode using the first drive source while driving on the second drive source, it is possible to prevent a decrease in the driving feeling perceived by the vehicle's occupants due to the internal combustion engine's rotational speed not having increased sufficiently.

[0106] [Item 15] Crankshaft and The first cylinder and the second cylinder, An internal combustion engine having a decompression device that, at rotational startup, reduces the pressure of the first cylinder and the second cylinder compared to after startup, and increases the pressure reduction of the second cylinder compared to the pressure reduction of the first cylinder, A vehicle that starts by the rotation of the aforementioned crankshaft.

[0107] According to the above configuration, the internal combustion engine in the vehicle can obtain the force necessary to rotate the crankshaft, while also further reducing compression resistance. As a result, for example, the vehicle can be started smoothly. [Item 16] A generator that generates electricity using the driving force of the internal combustion engine, A traction motor driven by the output of the aforementioned generator, A storage battery connected to the generator and the electric motor, The vehicle according to item 12 or 13, comprising: drive wheels driven by the output of the aforementioned electric motor.

[0108] According to the above configuration, even when the output of a generator that generates electricity using the driving force of an internal combustion engine drives an electric motor for traction, and the drive wheels are driven by the electric motor, the starting performance of the internal combustion engine is improved, allowing the vehicle to be brought to a state where it can be driven quickly.

[0109] [Item 17] Crankshaft and The first cylinder and the second cylinder, Multiple valves that open and close the combustion chambers of the first and second cylinders to the outside, A valve train that includes a camshaft that rotates around an axis to which the rotational driving force of the crankshaft is transmitted, and which operates the plurality of valves in at least one of the intake stroke and the exhaust stroke, The system includes a decompression device that reduces the pressure in the first and second cylinders to a level lower than that after rotational startup, The decompression device is, A plurality of decompression bodies are provided, each corresponding to the first cylinder and the second cylinder, and are configured to be shiftable between a reference position located inside the plurality of cams and a protruding position that protrudes outward from the outer circumferential surface of the plurality of cams from the reference position. The system includes a shifter that shifts the plurality of decompression bodies between the reference position and the protruding position according to the rotational speed of the crankshaft, An internal combustion engine in which at least one valve is opened by an external force transmitted from at least one decompressor body, thereby increasing the amount of pressure reduction in the second cylinder compared to the amount of pressure reduction in the first cylinder. [Explanation of symbols]

[0110] DW Drive Wheels E Internal combustion engine G Generator (starter motor) M Electric Motor P1 reference position P2 protrusion position 1 vehicle 3. First drive source 4. Second drive source 7. First cylinder 8. Second cylinder 9. Decompression device 14 Control device 30 cylinders 31 Crankshaft 36 Exhaust valve (valve) 40 Camshaft (Second Camshaft) 40a Shaft support section 42, 42Y cam 42C, 42D pair of cams 43 Decompression Shaft 50 decompressed bodies 50C, 50D Pair of Decompression Units 51 Shifter

Claims

1. Crankshaft and The first cylinder and the second cylinder, A decompression device that, during rotational startup, reduces the pressure of the first cylinder and the second cylinder compared to after rotational startup, and increases the pressure reduction of the second cylinder compared to the pressure reduction of the first cylinder, A plurality of valves that open and close the combustion chambers of the first cylinder and the second cylinder to the outside, It comprises a plurality of cams that rotate around a predetermined axis and provide driving force to the plurality of valves, The decompression device is, A plurality of decompression bodies are arranged to correspond individually to the first cylinder and the second cylinder, and are configured to be shiftable between a reference position located inside the plurality of cams and a protruding position that protrudes outward from the outer circumferential surface of the plurality of cams from the reference position, An internal combustion engine having a shifter that shifts the plurality of decompression bodies between a reference position and a protruding position according to the rotational speed of the crankshaft.

2. The internal combustion engine according to claim 1, wherein the decompression device drives the plurality of valves such that, in the compression stroke of the internal combustion engine, the opening period of the second cylinder is greater than the opening period of the first cylinder.

3. The internal combustion engine according to claim 1, wherein the number of decompression bodies arranged in accordance with the second cylinder is greater than the number of decompression bodies arranged in accordance with the first cylinder.

4. The plurality of cams include a pair of cams arranged in accordance with the second cylinder, The internal combustion engine according to claim 3, wherein the plurality of decompression bodies include a pair of decompression bodies arranged in correspondence with the pair of cams.

5. The internal combustion engine according to claim 4, wherein the pair of decompression bodies are arranged to be retractable inward from the outer circumferential surfaces of the pair of cams at positions on the outer circumferential surfaces of the pair of cams.

6. The internal combustion engine according to claim 1, wherein the plurality of decompression bodies have the same structure.

7. The internal combustion engine according to claim 1, comprising a single camshaft from which all of the decompression bodies and all of the plurality of cams corresponding to all of the decompression bodies are attached.

8. The internal combustion engine according to claim 1 or 2, further comprising a control device for controlling the combustion state such that the combustion state in the second cylinder differs between the time the internal combustion engine is started and after the internal combustion engine has started.

9. The decompression device is, The camshaft is a cylindrical body to which the aforementioned multiple cams are attached, The system includes a decompression shaft inserted inside the camshaft, which is pivotally supported independently of the camshaft so as to rotate independently of the camshaft's axis, and which applies an external force to the plurality of decompression bodies to shift the decompression bodies. The internal combustion engine according to claim 1, wherein the camshaft has a shaft support portion located between two adjacent cams among the plurality of cams, which rotatably supports the decompression shaft.

10. Crankshaft and Cylinders and, Multiple valves that open and close the combustion chamber of the cylinder to the outside, A decompression device that reduces the pressure of the cylinder during rotational startup compared to after rotational startup, It comprises a pair of cams that rotate around a predetermined axis and provide driving force to the plurality of valves, The decompression device is, It has a plurality of decompression bodies that are arranged corresponding to the cylinders and are configured to be shiftable between a reference position located inside the pair of cams and a protruding position that protrudes outward from the outer circumferential surface of the pair of cams from the reference position, An internal combustion engine in which the plurality of decompression bodies are arranged to be retractable inward from the outer surface of the pair of cams at positions on the outer surfaces of the pair of cams that are different from each other on the outer surfaces of the pair of cams.

11. The decompression device is, A camshaft is a cylindrical body to which the pair of cams are attached, The system includes a decompression shaft inserted inside the camshaft, which is pivotally supported independently of the camshaft so as to rotate independently of the camshaft's axis, and which applies an external force to the plurality of decompression bodies to shift the decompression bodies. The internal combustion engine according to claim 10, wherein the camshaft has a shaft support portion located between the pair of cams that rotatably supports the decompression shaft.

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