Camshaft

Abstract

This utility model relates to engine engineering, specifically to a camshaft for an internal combustion engine (ICE) equipped with a cylinder deactivation system. The camshaft of an internal combustion engine with deactivatable cylinders comprises variable-profile cams, each of which is secured to an axis mounted by support bearings in a blind bore in the camshaft extending from its end parallel and eccentric to the camshaft's axis of rotation. The variable-profile cams are located in grooves in the camshaft and are capable of rotating when said axis rotates, changing the variable-profile cam profile from the working profile to the zero profile and vice versa. This utility model addresses the problem of expanding the arsenal of technical means for the corresponding purpose.

Description

[0001] The utility model relates to the field of engine engineering, namely to the camshaft of an internal combustion engine (ICE) equipped with a system for shutting off gas exchange in cylinders.

[0002] Internal combustion engines equipped with systems for shutting off gas exchange in cylinders (cylinder shut-off systems) are widely known.

[0003] A camshaft for the valve timing mechanism of internal combustion engines is known (see patent application RU 93016774 A). The camshaft cams are designed as a roller on an axis, installed in a groove in the shaft eccentrically to its axis of rotation.

[0004] A cylinder deactivation system is known (see patent application DE 102009030373 A1), consisting of an actuator, a sliding cam block, a fixed cam block, a ball detent, and a camshaft. A signal is sent to the actuator, causing a corresponding metal rod to extend and engage in a guide groove in the sliding cam block. Due to the spiral shape of the groove and the rotation of the camshaft, the cam block shifts along the camshaft axis, replacing the working cam with a zero-profile cam above the valve rocker.

[0005] A variable valve mechanism is known (see US Patent 10001037 B2), consisting of an actuator, a sliding cam block, a ball detent, and a camshaft. A signal is sent to the actuator, causing a metal rod to extend and engage a guide groove in the sliding cam block. Due to the groove profile and rotation of the camshaft, the cam block moves along the camshaft axis, replacing the working cam.

[0006] Thus, in similar designs, profile changes are achieved by axially shifting a cam block with different profiles. The cam assembly is secured with a spring-loaded pin that engages the annular grooves of the movable cam block. This complicates the camshaft design and requires increased precision in cam placement and profiling.

[0007] The technical problem is the expansion of the arsenal of technical means in relation to the design of the camshaft of the cylinder deactivation system.

[0008] The technical result consists in developing an alternative design of the camshaft of the cylinder deactivation system.

[0009] A camshaft of an internal combustion engine with deactivatable cylinders, containing cams with a variable profile, each of which is secured on an axis mounted with the help of support bearings in a blind hole in the camshaft, passing from its end parallel and eccentrically relative to the axis of rotation of the camshaft, wherein the cams with a variable profile are located in grooves of the camshaft and are made with the possibility of rotation when the said axis is rotated to change the profile of the cam with a variable profile from the working profile to the zero profile and vice versa.

[0010] The axle is installed in the specified hole by means of three bearings.

[0011] The axle contains front, rear and intermediate journals designed to be installed in support bearings.

[0012] The diameter of the support journals increases from the front journal to the rear journal, and the diameter of the support bearings decreases from the end of the camshaft.

[0013] The variable profile cam is fixed to the axle by means of a key installed in a keyway provided on the axle.

[0014] The rotation of the variable profile cams is provided by means of actuators connected to the axes of the variable profile cams by means of a gear transmission.

[0015] Fig. 1 shows a general view of the camshaft of the gas exchange shut-off system in the cylinders of an internal combustion engine using the example of the camshaft of the intake valves.

[0016] Fig. 2 shows a longitudinal section of the camshaft of Fig. 1.

[0017] Fig. 3 shows a cross-section of the cam mechanism, where the variable profile cam is in the position of the working cam profile (gas exchange is on).

[0018] Fig. 4 shows a cross-section of the cam mechanism, where the variable profile cam is in the zero cam profile position (gas exchange is turned off).

[0019] Fig. 5 shows a cross-section of the cam mechanism at the start of rotation of the cam axis with a variable profile to change the cam profile from the working profile to the zero profile.

[0020] Fig. 6 shows a cross-sectional view of the cam mechanism at the completion of the rotation of the variable profile cam axis to change the cam profile from the working profile to the zero profile.

[0021] Fig. 7 shows an axonometric view of an example of the implementation of a cam axis with a variable profile.

[0022] The following positions are indicated on the figures: 1 - camshaft; 2 - cam with a constant profile; 3 - cam with a variable profile; 4 - axis of the cam with a variable profile; 5 - actuator; 6 - actuator shaft; 7 - gear; 8 - front support journal; 9 - rear support journal; 10 - intermediate support journal; 11 - pinion; 12 - keyway.

[0023] The system for shutting off gas exchange in the cylinders of an internal combustion engine comprises a camshaft 1, one or more cams 2 with a constant profile, one or more cams 3 with a variable profile, one or more axes 4 of a cam with a variable profile, one or more actuators 5, one or more shafts 6 of an actuator and a control system (not shown).

[0024] On the camshaft 1, cams 2 with a constant profile and cams 3 with a variable profile are located. As shown in the figures, each cam 3 with a variable profile is located in grooves made according to its shape on the camshaft 1. Each cam 3 with a variable profile is mounted on a corresponding axis 4, which passes inside the camshaft 1, comes out from its end and ends with a gear mounted on it. The axis (axes) 4 pass parallel to the axis of rotation of the camshaft and is eccentric to it, i.e. the axis (axes) of the cam 3 with a variable profile does not coincide with the axis of rotation of the camshaft 1. In Fig. 1 and 2, it is shown that each cam 3 with a variable profile is mounted on its own axis 4, however, it should be noted that in another embodiment they can be located on one common axis 4.

[0025] The actuators 5, preferably servo drives, are mounted coaxially with the camshaft 1 from its ends, as shown in Fig. 2, and by means of a gear transmission 7 change the profile of the cams 3 with a variable profile from the working profile to the zero profile and vice versa.

[0026] As a specialist should understand, the working cam profile is the profile (profile section) with which, when interacting with the valve actuator (specifically, via the rocker arm), the tappet performs the valve's power stroke, ensuring the mechanism's intended operation. A zero cam profile, on the other hand, is a profile (profile section) that does not interact with the valve actuator, or interacts only slightly with the valve actuator, resulting in no power stroke for the valve, thus shutting off gas exchange in the given cylinder, effectively shutting it off.

[0027] The shaft 4 of the cam 3 with a variable profile is a shaft (see Fig. 7) that is installed in a blind hole (tunnel) inside the camshaft 1 by means of support bearings installed in said tunnel, similar to the camshaft, which is installed inside the cylinder block. The support bearings provide a stable surface for the shaft to rotate on, reducing friction and wear.

[0028] For installation in support bearings, the axle 4 comprises a front support journal 8, a rear support journal 9 and at least one intermediate support journal 10 (in Fig. 7, two intermediate support journals 10 are shown as an example). In order to ensure the possibility of installing the axle 4 in the tunnel of the camshaft 1, the tunnel formed inside the camshaft 1 and, accordingly, the diameter of the support bearings under the support journals 8, 9, 10 of the axle 4 have a larger diameter at the beginning of the tunnel (at the end of the camshaft 1) and decrease as the tunnel deepens (from the rear support bearing to the front support bearing), the diameter of the support journals 8, 9, 10 increases from the front support journal 8, which has the smallest diameter, to the rear support journal 9, which has the largest diameter. This makes it possible to install the axle 4 through the bearings installed in the tunnel of the camshaft 1. To interact with the drive, a gear 11 is provided at the rear support on the axle 4.

[0029] Axle 4 can be lubricated through oil channels passing through journals 8, 9, 10 of camshaft 1 bearings whenever the openings of the oil channels used for lubricating the bearings and the openings of the outlet channels are aligned. Axle 4 is secured at the end against longitudinal displacement with a lock washer (not shown).

[0030] The cam 3 with a variable profile is mounted on the axis 4 and fixed with the help of a key (not shown) entering the keyway 12 provided on the axis 4.

[0031] When the internal combustion engine is running on all cylinders, the actuator 5 rotates on the camshaft 1. The shaft 6 of the actuator 5 is locked and holds the cam 3 with a variable profile in the position of the working profile, to carry out gas exchange of all cylinders.

[0032] When specified conditions are met, in particular, when the load on the internal combustion engine drops below a certain level from the maximum power, the control system switches off one or more internal combustion engine cylinders.

[0033] After cam 3 with variable profile passes the rocker arm (see Fig. 5; α = 70°÷80°), actuator 5 releases the lock on its shaft 6, rotates it 180°, and locks its shaft 6 again. This brings cam 3 with variable profile to the zero profile position in the off-gas mode. The cam profile rotation, accordingly, occurs with the valve closed.

[0034] A position sensor, such as an encoder or a Hall sensor (not shown in the figure), is used to monitor the position of the variable-profile cam 3. The profile position of the variable-profile cam 3 is fixed by the servo drive of the actuator 5.

[0035] When the load increases to 50% or more, the control system restores operation of the deactivated cylinders. After cam 3 with the variable profile passes the rocker arm, actuator 5 releases the lock on its shaft 6, rotates it 180°, and locks its shaft 6 again, thereby fixing cam 3 with the variable profile in the operating profile position in the gas exchange mode.

[0036] A position sensor such as an encoder or a Hall sensor (not shown) is used to monitor the position of the camshaft 1 to start rotating the variable profile cam 3.

[0037] Power supply to actuator 5 (not shown) is provided via a brush assembly or by electromagnetic induction.

[0038] In particular, this cylinder gas exchange shutoff system can be used in the internal combustion engine of a diesel generator set (DGS). When the DGS is operating in its primary mode (primary power source), the engine load must be at least 50% of its maximum power. At lower loads, the internal combustion engine becomes unstable, causing the current frequency to fluctuate, and the engine itself to be subject to increased wear. Therefore, when the DGS drive load is less than 50% of its maximum power, one or more cylinders of the DGS are shut off. This means the intake and exhaust valves of the deactivated cylinders remain closed, and the fuel supply to these cylinders is cut off. The DGS operates more efficiently and reliably on the remaining cylinders, and the operating range of the DGS drive loads is 25-100% of its maximum power.

[0039] Thus, the technical problem has been solved by developing an alternative camshaft design. The main difference between this solution and existing ones is that the cam profile is changed by rotating the cam around an axis parallel to the camshaft axis, rather than by shifting the camshaft along the axis. Mounting bearings on the camshaft axis, which features a variable profile and is located inside the engine's camshaft tunnel, provides a stable support surface for the axis, reducing friction and wear.

Claims

1. A camshaft of an internal combustion engine with deactivatable cylinders, comprising cams with a variable profile, each of which is secured on an axis mounted with the aid of support bearings in a blind hole in the camshaft, extending from its end parallel and eccentrically relative to the axis of rotation of the camshaft, wherein the cams with a variable profile are located in grooves of the camshaft and are made with the possibility of rotation when the said axis is rotated to change the profile of the cam with a variable profile from the working profile to the zero profile and vice versa.

2. The camshaft according to paragraph 1, characterized in that the axle is installed in the specified hole by means of three bearings.

3. The camshaft according to paragraph 2, characterized in that the axle contains front, rear and intermediate journals designed with the possibility of installation in support bearings.

4. The camshaft according to paragraph 3, characterized in that the diameter of the support journals increases from the front journal to the rear journal, and the diameter of the support bearings decreases from the end of the camshaft.

5. A camshaft according to claim 1, characterized in that the cam with a variable profile is secured to the axis using a key installed in a keyway provided on the axis.

6. A camshaft according to paragraph 1, characterized in that the rotation of the cams with a variable profile is provided by means of actuators connected to the axes of the cams with a variable profile by means of a gear transmission.

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