JP2014129730A - Engine accessory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine accessory that reduces noises and vibrations generated when the engine accessory with fluctuating load torque is driven by a cam shaft.SOLUTION: In an engine accessory 20 driven by a cam shaft 15 rotating in synchronization with a crank shaft 11 of an engine 10, a phase of the crank shaft, in which one of drive torque transferred to the engine accessory from the cam shaft and load torque required for drive of the engine accessory is set to a maximum value, and a phase of the crank shaft, in which the other one of the drive torque and the load torque is set to a minimum value, are separated from each other.

Description

  The present invention relates to an engine accessory driven by a camshaft of an engine, and more particularly to a device that reduces noise and vibration generated when an engine accessory whose drive torque varies is driven by a camshaft.

An automobile engine is sometimes provided with a vacuum pump such as a vane type in order to generate a negative pressure used for operating a brake booster.
For example, in Patent Document 1, a vane vacuum pump is driven by a drive shaft such as an engine camshaft, and the drive shaft and the drive shaft are absorbed in order to absorb eccentricity caused by a dimensional tolerance between the drive shaft and the pump rotor. It is described that an Oldham coupling is provided between the rotor and the rotor.
Japanese Patent Application Laid-Open No. 2004-228561 describes that in an Oldham coupling that transmits a driving force from a camshaft to a supply pump, a predetermined protrusion is provided to prevent misassembly and fluttering.

JP 2010-112332 A JP 2010-249151 A

Since the camshaft receives a reaction force from the valve spring when the cam crest drives the valve, the driving torque transmitted from the camshaft to the engine accessory such as a vacuum pump fluctuates at a predetermined cycle. .
On the other hand, the load torque required for driving the vacuum pump also varies at a predetermined cycle according to the positions of the rotor and the vane.
For this reason, when an Oldham coupling is interposed between the camshaft and the vacuum pump and the vacuum pump is driven, the camshaft and the vacuum pump rotor are displaced from each other in the rotational direction. Anomalous noise such as sudden noise and impact noise may occur.
An object of the present invention is to provide an engine accessory in which noise and vibration generated when an engine accessory whose driving torque varies is driven by a camshaft is reduced.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is an engine accessory driven by a camshaft that rotates in synchronization with a crankshaft of an engine, the driving torque transmitted from the camshaft to the engine accessory, and the engine accessory The engine auxiliary machine is characterized in that one of the load torques required for driving the crankshaft is spaced apart from the phase of the crankshaft where the other has a maximum value.
According to a second aspect of the present invention, the crankshaft phase in which one of the driving torque and the load torque has a maximum value and the phase of the crankshaft in which the other has a minimum value are separated by 90 degrees or more with a crank angle. The engine accessory according to claim 1, wherein the engine accessory is provided.
According to this, when the drive torque transmitted from the camshaft to the engine accessory increases, the load torque required to drive the engine accessory decreases, and the rotational speed of the engine accessory accelerates rapidly. When the torque is reduced, it is possible to prevent the load torque from increasing and the rotational speed of the engine accessory from rapidly decelerating, and to suppress noise and vibration from the joint due to a sudden change in the rotational speed.
In the present specification, claims, and the like, “maximum value” and “minimum value” are comparisons having a cycle of 90 degrees or more in terms of a crank angle, for example, in waveforms of driving torque fluctuation and load torque fluctuation. It is assumed that a peak value generated by a low-order component is indicated, and a peak value that appears in large numbers due to a short-cycle high-order component is not included.

The invention according to claim 3 is characterized in that at least one of the phase of the crankshaft in which the driving torque and the load torque each have a maximum value and the phase of the crankshaft in which each has a minimum value are brought close to each other. The engine accessory according to claim 1 or 2.
The invention according to claim 4 is an engine accessory driven by a camshaft that rotates in synchronization with the crankshaft of the engine, the drive torque transmitted from the camshaft to the engine accessory, and the engine accessory. The engine auxiliary machine is characterized in that at least one of the phase of the crankshaft in which the load torque required for driving each takes a maximum value and the phase of the crankshaft in which the load torque takes a minimum value are brought close to each other.
The invention according to claim 5 is within 45 degrees with the crank angle being at least one of the phase of the crankshaft in which the driving torque and the load torque each have a maximum value and the phase of the crankshaft in which each has a minimum value. The engine accessory according to claim 3 or 4, wherein the engine accessory is arranged as described above.
According to this, when the drive torque transmitted from the camshaft to the engine accessory increases, the load torque required to drive the engine accessory increases, and when the drive torque decreases, the load torque decreases. Thus, the change in the rotational speed of the engine accessory can be suppressed, and the noise and vibration from the joint due to the sudden change in the rotational speed can be suppressed.

  According to a sixth aspect of the invention, in any one of the first to fifth aspects, the engine accessory is a vacuum pump driven by the camshaft via an Oldham coupling. It is an engine auxiliary machine of description.

  As described above, according to the present invention, it is possible to provide an engine accessory with reduced noise and vibration generated when the engine accessory whose drive torque varies is driven by the camshaft.

It is a mimetic diagram showing composition of an engine which has an example of an engine auxiliary machine to which the present invention is applied. It is a schematic diagram which shows the structure of the vacuum pump provided in the engine of FIG. FIG. 2 is a schematic diagram illustrating a camshaft, a vacuum pump, and an Oldham coupling provided therebetween in the engine of FIG. 1. It is a graph which shows the log | history of the rotational direction deviation | shift amount of the camshaft and rotor in the Oldham coupling outer peripheral part at the time of making the vane phase angle of a vacuum pump advance with respect to a reference | standard vane angle. It is a graph which shows the log | history of the rotational direction deviation | shift amount of the camshaft and rotor in the Oldham coupling outer peripheral part at the time of delaying the vane phase angle of a vacuum pump with respect to a reference | standard vane angle. It is a graph which shows the correlation with the vane phase angle of a vacuum pump, and the rotation deviation amount which becomes the maximum. It is a graph which shows the correlation with the vane phase angle of a vacuum pump, and the vibration which Oldham coupling generate | occur | produces. It is a graph which shows the log | history of the driving torque input into a vacuum pump from a cam shaft, and the load torque required for the drive of a vacuum pump.

  The present invention aims to provide an engine accessory with reduced noise and vibration generated when the engine accessory whose driving torque varies is driven by a camshaft. The engine accessory (from the camshaft via the Oldham coupling) For example, the driving torque input to the vacuum pump) and the load torque required for driving the engine auxiliary machine are separated from the crankshaft phase at which the maximum value and the crankshaft phase at which the other has the minimum value are separated, and the driving torque and load The problem was solved by bringing the crankshaft phase at which the torque takes a maximum value and the crankshaft phase at which the torque takes a minimum value close to each other.

Embodiments of an engine accessory to which the present invention is applied will be described below.
The engine accessory of the embodiment is a vacuum pump that is driven by the camshaft of the engine and generates a negative pressure used for operating the brake booster.
FIG. 1 is a schematic diagram illustrating a configuration of an engine having a vacuum pump according to an embodiment.
FIG. 1 shows the engine viewed from above.

The engine 10 is mounted on an automobile such as a passenger car and used as a driving power source.
As an example, the engine 10 is a horizontally opposed four-cylinder four-stroke gasoline or diesel engine.
The engine 10 includes a crankshaft 11, a piston 12, a connecting rod 13, a valve 14, a camshaft 15, a crank sprocket 16, a cam sprocket 17, a timing chain 18, and the like.

  The crankshaft 11 is an output shaft of the engine 10 and includes a journal portion supported by a main bearing provided in the cylinder block, a crankpin portion arranged eccentrically with respect to the journal portion, a journal portion and a crankpin portion. And a crank web portion provided between the two.

The piston 12 is a member that is inserted into the cylinder and reciprocates.
The connecting rod (connecting rod) 13 is swingably connected to a piston pin provided on the piston 12 and a crankpin portion of the crankshaft 11, and transmits force between the piston 12 and the crankshaft 11. It is.

The valve 14 is a valve body that opens and closes an intake port for introducing fresh air (combustion air) into a combustion chamber provided in the cylinder and an exhaust port for discharging exhaust gas from the combustion chamber at predetermined valve timings. .
The camshaft 15 is a rotating shaft having a cam portion that drives the valve 14, and is arranged in the cylinder head in parallel with the crankshaft 11.
When the engine 10 is a DOHC engine, one camshaft 15 is provided on each of the intake side (for example, upper side) and the exhaust side (for example, lower side).

The camshaft 15 is rotationally driven at a speed half that of the crankshaft by a drive system including a crank sprocket 16, a cam sprocket 17, a timing chain 18, and the like.
The crank sprocket 16 is a gear provided at the front end of the crankshaft 11.
The cam sprocket 17 is a gear provided at the front end of the camshaft 15 and has twice as many teeth as the crank sprocket 16.
The timing chain 18 is stretched over the crank sprocket 16 and the cam sprocket 17, and transmits a driving force from the crankshaft 11 to the camshaft 15.

A vacuum pump 20 is provided at the rear end (the end opposite to the crank sprocket 16) of the intake shaft of the right bank of the engine 10 via an Oldham coupling 30 (see FIG. 3). ing.
The vacuum pump 20 is a vane pump that is driven by the camshaft 15 to generate a negative pressure that operates a negative pressure brake booster.

FIG. 2 is a schematic diagram showing the configuration of the vacuum pump, and shows a state in which the inside of the housing is viewed from the direction of the rotation axis of the rotor.
In FIG. 2, the reference values that are reference examples of the present invention are shown for the phases of the crankshaft, camshaft, and vane.
Hereinafter, the phase angle of the vane with respect to the camshaft 15 at this time will be described as a “reference vane angle”.
The vacuum pump 20 includes a housing 21, an intake port 22, an exhaust port 23, a rotor 24, a vane 25, and the like.

The housing 21 is a member that accommodates the rotor 24, the vane 25, and the like, and is formed of a light alloy such as aluminum.
The housing 21 is fixed to the cylinder head of the engine 10.
A space portion that is substantially elliptical when viewed from the rotor axial direction is formed inside the housing 21.
This space part functions as a chamber for compressing air.
The intake port 22 has an attachment to which a through hole and a pipe formed in the outer peripheral surface portion of the housing 21 are connected, and is a portion that introduces air into the housing 21.
The exhaust port 23 is an opening formed in a planar portion (surface portion that is in sliding contact with the side end of the vane) on the inner surface of the housing 21 that is orthogonal to the rotor rotation axis, and is a portion that exhausts air from the housing 21.
The exhaust port 23 is disposed adjacent to the rotor 24.

The rotor 24 is a member that is connected to the camshaft 15 via the Oldham coupling 30 and rotates relative to the housing 21 at a rotation speed of 1: 1 with the camshaft 15 by being driven to rotate by the camshaft 15. is there.
The rotor 24 is formed in a substantially cylindrical shape, and is arranged offset to one side in the minor axis direction with respect to the center of the elliptical space inside the housing 21.
The rotor 24 is formed with a groove portion that holds the vane 25 in a slidable manner.

The vane 25 is a member formed in a flat plate shape, for example, and is held in a groove portion of the rotor 24 so as to be slidable along the radial direction of the rotor 24.
The vane 25 rotates relative to the housing 21 while sliding relative to the rotor 24 according to the rotation of the rotor 24.
At this time, both end portions of the vane 25 slide with the inner peripheral surface of the housing 21.
Due to such movement, the vane 25 sucks air from the intake port 22 and conveys it to the region where the exhaust port 23 is provided while compressing it, and discharges it from the exhaust port 23.
As shown in FIG. 2, the vane 25 is configured to be a tip position that is a neutral position when the camshaft phase angle is −36 ° and the crankshaft phase angle is −72 °.

In such a vane type vacuum pump, it is known that noise and vibration are significantly generated during operation depending on the phase of the vane 25 with respect to the phases of the crankshaft 11 and the camshaft 15.
Such noise and vibration are generated from the Oldham coupling 30 that connects the camshaft 15 and the rotor 24.
FIG. 3 is a schematic diagram showing a camshaft, a vacuum pump, and an Oldham coupling provided between them in the engine of FIG.

The Oldham coupling 30 is a joint that is provided between the camshaft 15 and the rotor 24 and transmits a driving force while absorbing the eccentricity therebetween.
The Oldham coupling 30 is between the first slider portion 31 that permits relative translational movement along the radial direction between the camshaft 15 and the Oldham coupling 30, and between the rotor 24 and the Oldham coupling 30. And a second slider portion 32 that allows relative translational movement along the radial direction.
The first slider portion 31 is configured to have a ridge formed at the end of the camshaft 15 and a groove portion provided on the Oldham coupling 30 side into which the ridge is inserted.
The second slider portion 32 is configured to have a ridge formed at the end of the input shaft portion of the rotor 24 and a groove portion provided on the Oldham coupling 30 side into which the ridge is inserted. .
The guide directions of the first slider part 31 and the second slider part 32 (extending direction of the ridges and grooves) are, for example, arranged so as to be orthogonal when the Oldham coupling 30 is viewed from the central axis direction. Yes.

In the case of the configuration described above, the driving torque input from the camshaft 15 to the vacuum pump 20 has periodic fluctuations due to the valve driving of each cylinder by the cam.
On the other hand, the load torque required to drive the vacuum pump 20 also periodically varies according to the position of the vane. Therefore, the rotational speed of the rotor 24 of the vacuum pump 20 also varies periodically, and the camshaft 15 Rotational deviation occurs between the two.

Since the first slider portion 31 and the second slider portion 32 of the Oldham coupling 30 have inevitably provided gaps due to dimensional tolerances, etc., the rotor 24 rotates relative to the camshaft 15. When it deviates in the direction, as shown in FIG. 3, the Oldham coupling 30 shows a rattling behavior, and a collision sound (impact sound) is generated by colliding with other parts.
Such an impact sound is considered to become more prominent as the rotational deviation increases.

FIG. 4 is a graph showing a history of rotational direction deviation between the camshaft and the rotor at the outer periphery of the Oldham coupling when the vane phase angle of the vacuum pump is advanced with respect to the reference vane angle.
FIG. 5 is a graph showing the history of the rotational displacement between the camshaft and the rotor at the outer periphery of the Oldham coupling when the vane phase angle of the vacuum pump is retarded with respect to the reference vane angle.
4 and 5, the horizontal axis indicates the phase of the crankshaft 11, and the vertical axis indicates the rotational deviation amount calculated by simulation.
This rotational deviation amount (lifting amount) is obtained by calculating the rotational speed fluctuations of both from the camshaft driving torque fluctuation and the vacuum pump load torque fluctuation and analyzing the difference.
As shown in FIG. 4 and FIG. 5, it can be seen that the rotational deviation periodically occurs in a specific phase, and the magnitude thereof varies depending on the phase of the vane.

FIG. 6 is a graph showing the correlation between the vane phase angle of the vacuum pump and the maximum rotational deviation amount.
In FIG. 6, the horizontal axis indicates the advance amount and retard amount of the vane phase angle with respect to the reference vane angle, and the vertical axis indicates the maximum rotational deviation amount in one cycle.
Further, FIG. 6 plots data at the time of low engine load (corresponding to constant vehicle speed travel) and data at high load (corresponding to acceleration travel).

As shown in FIGS. 4 to 6, it can be seen that the rotational deviation is significantly reduced when the vane phase angle is advanced with respect to the reference vane angle at any negative pressure.
In particular, it can be seen that when the advance amount of the vane phase angle with respect to the reference vane angle is 30 to 60 °, the amount of rotational deviation is remarkably reduced, and in particular, the best at 45 °.

FIG. 7 is a graph showing the correlation between the vane phase angle of the vacuum pump and the vibration generated by Oldham coupling.
In FIG. 7, the horizontal axis indicates the advance amount and retard amount of the vane phase angle with respect to the reference vane angle, and the vertical axis indicates the acceleration due to the vibration of the cam cap that holds the cam shaft 15 in the vicinity of the Oldham coupling.
FIG. 7 plots data when the engine is under a low load (equivalent to constant vehicle speed traveling) and data during a high load (equivalent to acceleration traveling) (both engine speeds are 2000 rpm).
Also in FIG. 7, it can be seen that a tendency similar to the tendency described in FIG.

Hereinafter, the generation mechanism of noise and vibration as described above will be considered.
FIG. 8 is a graph showing the history of the drive torque input from the camshaft to the vacuum pump and the load torque required to drive the vacuum pump.
In FIG. 8, the horizontal axis represents the crank angle, and the vertical axis represents the torque.
Further, FIG. 8 shows reference vane angle data and data obtained by advancing the vane phase angle by + 45 ° and + 60 °, respectively.

As shown in FIGS. 4 and 5, in the case of the reference vane angle, when the crank angle is around 610 to 620 °, the amount of rotational deviation becomes extremely large, and the sudden change in the rotational speed of the rotor 24 here is noise and vibration. This is thought to be the cause of this.
As shown in FIG. 8, the driving torque of the camshaft takes a minimum value min1 near a crank angle of 610 °.
On the other hand, at the reference vane angle, the load torque of the vacuum pump 20 has a maximum value max1 near the crank angle of 620 °.
Accordingly, it is presumed that the rotational speed of the rotor 24 rapidly decreases and a relatively large rotational deviation occurs between the rotor 24 and the camshaft 15.

On the other hand, by advancing the vane phase angle with respect to the reference vane angle, the phase angle of the crankshaft at which the load torque has a maximum value max1 is set to the phase angle of the crankshaft at which the drive torque has a minimum value min1. Can be shifted.
For example, by advancing the vane phase angle by + 45 ° with respect to the reference vane angle, the maximum value max2 corresponding to the maximum value max1 at the reference vane angle appears near the crank angle of 530 °.
Further, there is a maximum value max3 of the drive torque in the vicinity of the crank angle 530 °.
On the other hand, there is a minimum load torque value min2 in the vicinity of the crank angle 590 ° close to the crank angle at which the minimum value min1 of the drive torque appears.

In this way, the rotational speed of the rotor 24 of the vacuum pump 20 is prevented from suddenly decelerating by separating the crank phase angle at which the drive torque takes a minimum value and the crank phase angle at which the load torque takes a maximum value. be able to.
Also, the crank phase angle at which the drive torque takes the maximum value and the crank phase angle at which the load torque takes the maximum value are brought close to each other, and the crank phase angle at which the drive torque takes the minimum value and the crank phase at which the load torque takes the minimum value By bringing the corners close to each other, fluctuations in the rotational speed of the rotor can be suppressed.
Thereby, the behavior of the Oldham coupling 30 with respect to the camshaft 15 and the rotor 24 can be suppressed, and noise and vibration can be reduced.

As a result of the above examination and consideration, in this embodiment, the phase angle of the vane 25 is advanced by 45 ° or 60 ° with respect to the reference vane angle.
Even when the advance angle is 60 °, the same tendency as in the case of 45 ° is observed although there is a difference in degree.
These optimal advance and retard amounts themselves depend on the camshaft specifications such as the number of cylinders of the engine, valve timing, and the structure of the vacuum pump. The crank phase angle at which one of the load torques has a maximum value and the crank phase angle at which the other has a minimum value are preferably separated by, for example, 90 ° or more.
Further, it is considered preferable that the crank phase angle at which the drive torque has a maximum value and the crank phase angle at which the load torque has a maximum value are close to each other, for example, within 45 °.
Further, it is considered preferable that the crank phase angle at which the drive torque takes a minimum value and the crank phase angle at which the load torque takes a minimum value are close to each other, for example, within 45 °.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
In the embodiment, the crank phase angle at which the drive torque takes the minimum value and the crank phase angle at which the load torque takes the maximum value are separated from each other, but the crank phase angle at which the drive torque takes the maximum value and the load torque are minimized. It is considered that substantially the same effect can be obtained even when the crank phase angle taking a value is separated.
Further, the engine accessory driven by the camshaft is not limited to the vane type vacuum pump, but may be another type of vacuum pump or a device other than the pump.

DESCRIPTION OF SYMBOLS 10 Engine 11 Crankshaft 12 Piston 13 Connecting rod 14 Valve 15 Camshaft 16 Crank sprocket 17 Cam sprocket 18 Timing chain 20 Vacuum pump 21 Housing 22 Intake port 23 Exhaust port 24 Rotor 25 Vane 30 Oldham coupling 31 1st slider part 32 1st 2 slider part

Claims (6)

An engine accessory driven by a camshaft that rotates in synchronization with the crankshaft of the engine,
One of the drive torque transmitted from the camshaft to the engine accessory and the load torque required to drive the engine accessory has a maximum value, and the other has a minimum value. An engine accessory characterized in that The crankshaft phase in which one of the driving torque and the load torque has a maximum value and the phase of the crankshaft in which the other has a minimum value are separated from each other by 90 degrees or more as a crank angle. Item 2. The engine accessory according to Item 1. The at least one of the phase of the crankshaft in which the driving torque and the load torque each have a maximum value and the phase of the crankshaft in which the driving torque and the load torque each have a minimum value are close to each other. Engine accessory described in 1. An engine accessory driven by a camshaft that rotates in synchronization with the crankshaft of the engine,
A driving torque transmitted from the camshaft to the engine accessory and a load torque required to drive the engine accessory each have a maximum value of the crankshaft, and a phase of the crankshaft having a minimum value. An engine accessory characterized in that at least one of them is close. The drive torque and the load torque are arranged such that at least one of the phase of the crankshaft in which the driving torque and the load torque have a maximum value and the phase of the crankshaft in which the driving torque and the load torque respectively have a minimum value is within 45 degrees. The engine accessory according to claim 3 or claim 4. The engine accessory according to any one of claims 1 to 5, wherein the engine accessory is a vacuum pump driven by the camshaft via an Oldham coupling.

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