JP2006336622A - Transmission mechanism and starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce vibration and noise of a motor when cranking. <P>SOLUTION: This starter 10 is provided with the motor 12 for outputting constant torque and the transmission mechanism 15 for converting output torque of the motor 12 into a predetermined form to transmit to a crank shaft 52. The transmission mechanism 15 is provided with a pair of first gears 20 composed of a pair of elliptical gears 24, 26 and a pair of second gears 22 composed of a pair of elliptical gears 28, 30. In all of the pair of first gears 20 and the pair of second gears 22, torque transmission rate fluctuates at a predetermined period. A fluctuation period of torque transmission rate of the pair of second gears 22 is 1/2 of that of the pair of first gears 20. The pair of second gears 22 are attached to the pair of first gears 20 with difference in phase of 1/4π. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission mechanism that transmits torque from a starter motor to a crankshaft of an engine, and an engine starter that includes the transmission mechanism.

  When starting an engine mounted on a vehicle or the like, the engine is ignited after the crankshaft of the engine is rotated by a starter motor. At this time, there is a problem that vibration or noise of the starter motor is likely to occur during the time from the start of rotation of the crankshaft to ignition, so-called cranking.

  A major cause of this motor vibration or the like is a variation in reaction torque generated on the crankshaft. As is well known, the crankshaft rotates to repeat four cycles of suction, compression, explosion, and exhaust, but the reaction torque generated on the crankshaft also varies with this cycle change. This reaction torque fluctuation naturally occurs even before engine ignition. For this reason, the fluctuating reaction force torque is transmitted to the motor and the like, causing vibration and noise of the motor. In particular, an engine mounted on a hybrid vehicle needs to be ignited at a higher speed than a conventional gasoline vehicle engine. When the crankshaft is rotated at a high speed, the torque fluctuation increases, and as a result, the motor vibration tends to increase.

  In view of this, several techniques for preventing vibration associated with fluctuations in the reaction torque have been proposed. For example, Patent Document 1 discloses a starting device in which a pair of non-circular gears are provided between a link gear of a starter motor and a crankshaft. This is configured to transmit a constant torque output from the starter motor to the crankshaft via a pair of non-circular gears, specifically, a pair of elliptical gears. When a pair of elliptical gears is used, the elliptical gear connected to the link gear rotates at a constant speed, but the other elliptical gear meshing with the elliptical gear undergoes a periodic angular velocity change. Patent Document 1 discloses that the pair of elliptical gears are positioned so that the periodic angular velocity change of the other elliptical gear cancels the torque fluctuation of the crankshaft.

JP-A-3-294656

  Torque output from a pair of elliptical gears as disclosed in Patent Document 1 fluctuates in a sine wave shape. Therefore, the technique of Patent Document 1 is effective when the reaction torque of the crankshaft varies in a sine wave shape. In practice, however, the reaction torque generated on the crankshaft of the engine is often not sinusoidal. For example, in the case of a four-cycle four-cylinder engine, it is known that the reaction torque of the crankshaft fluctuates in a deformed sine wave shape having two large peaks and two small peaks during one fluctuation period. In the case of such an engine, the technique disclosed in Patent Document 1 cannot effectively counteract the reaction torque, resulting in a problem that motor vibration or the like is likely to occur.

  Therefore, an object of the present invention is to provide a transmission mechanism and a starting device that can more effectively prevent vibrations of the motor at the time of starting the engine.

  A transmission mechanism according to the present invention is a transmission mechanism that transmits torque from a starter motor to a crankshaft of an engine. The transmission mechanism includes at least a pair of non-circular gears, and transmits torque as the pair of non-circular gears rotates. A first gear pair whose ratio fluctuates in a first fluctuation cycle and a pair of non-circular gears connected to the first gear pair, and the torque transmission ratio is changed according to the rotation of the pair of non-circular gears. A second gear pair that fluctuates in a second fluctuation period, which is a different period from the motor, and the ratio of the fluctuation period between each gear pair and the value of the phase angle between each gear pair are constant torque from the motor to the transmission mechanism. Is set to a value at which the torque output from the transmission mechanism becomes a torque corresponding to the reaction torque generated in the crankshaft.

  In a preferred embodiment, the torque conversion ratio of each gear pair varies sinusoidally. The non-circular gears constituting each gear pair are preferably elliptical gears.

  When F≈αsinθ + βsin2θ holds when the reaction torque generated on the crankshaft is F, α, β are constants, and θ is the crank angle, the second fluctuation period is 1/2 of the first fluctuation period, The phase angle of the second gear pair with respect to one gear pair is preferably 1 / 4π. At that time, the pair of elliptical gears constituting the first gear pair has the same shape, and the point eccentric from the center of the ellipse is the center of rotation, and the pair of elliptical gears constituting the second gear pair is In any case, it is desirable that they have the same shape and have the center of the ellipse as the center of rotation. This is particularly suitable when the crankshaft is a crankshaft of a 4-cycle 4-cylinder engine.

  Another starter according to the present invention is an engine starter that forcibly rotates a crankshaft to start the engine, and outputs a starter motor that outputs a driving force for rotation of the crankshaft, and is output from the starter motor. A transmission mechanism that transmits the torque to the crankshaft, and the transmission mechanism comprises at least a pair of non-circular gears, and the torque transmission ratio fluctuates in the first fluctuation period as the pair of non-circular gears rotate. And a pair of non-circular gears connected to the first gear pair, and the torque transmission ratio is a period different from the first fluctuation period as the pair of non-circular gears rotates. A second gear pair that fluctuates at a fluctuating period, and the ratio of the fluctuating period between each gear pair and the value of the phase angle between each gear pair are determined when a constant torque is input from the motor to the transmission mechanism. Wherein the torque output from the reach mechanism is set to a value that causes a torque corresponding to the reaction torque generated in the crankshaft.

  According to the present invention, a plurality of non-circular gear pairs having different torque transmission ratio fluctuation cycles are provided, and when the constant torque is input from the motor to the transmission mechanism, the fluctuation cycle ratio and phase angle value are determined. The torque output from the transmission mechanism is set to a value corresponding to the reaction torque generated on the crankshaft. Therefore, the reaction force torque that varies in a complicated manner, such as a deformed sine wave, can be canceled more reliably. As a result, vibrations of the motor can be effectively prevented.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a starting device 10 according to an embodiment of the present invention. The starting device 10 has a configuration suitable for starting a four-cycle four-cylinder engine mounted on a vehicle, particularly an engine that needs to be ignited at a high speed. However, it can also be applied to starting other types of engines by appropriately adjusting the number of gear pairs constituting the starting device 10 and the mounting angle.

  The starting device 10 is a device that forcibly rotates the crankshaft 52 of the engine 50 by the rotational force of the motor 12 in order to start the engine 50. The starting device 10 of the present embodiment is roughly divided into a motor 12 that is a power source for rotation of the crankshaft 52 and a transmission mechanism 15 that transmits torque from the motor 12 to the crankshaft 52. The motor 12 is controlled by a control device (not shown). When starting the engine 50, the motor 12 rotates at a high speed and outputs a constant torque. A pinion 14 is attached to the rotating shaft of the motor 12 and meshes with a link gear 16 described later.

  The transmission mechanism 15 includes a link gear 16 that meshes with the pinion 14 of the motor 12, and a two-stage gear 18 that converts torque from the link gear 16 into a predetermined form and transmits the torque to the crankshaft 52. The link gear 16 decelerates the rotational force output from the motor 12 and amplifies the output torque by meshing with a pinion attached to the rotation shaft of the motor 12. The amplified torque is transmitted to the two-stage gear 18.

  The two-stage gear 18 includes two pairs of gears, that is, a first gear pair 20 and a second gear pair 22. FIG. 2 is a diagram showing a schematic configuration of the two-stage gear 18. In FIG. 2, the solid line indicates the first gear pair 20, and the broken line indicates the second gear pair 22. The first gear pair 20 includes a first gear 24 connected to the link gear 16 by a first shaft 32 and a second gear 26 that meshes with the first gear 24. The first gear 24 and the second gear 26 are elliptic gears having the same shape. The two gears rotate around the points O1 and O2 that are the focal points of the ellipse.

  Here, as is well known, in the case of an elliptical gear pair, the rotational force is not transmitted as it is, but is transmitted after being decelerated to some extent. This reduction ratio, in other words, the torque transmission ratio is not constant, and varies periodically according to the rotation of the elliptical gear pair. In the case of the first gear pair 20, the rotation centers O 1 and O 2 of the two elliptical gears 24 and 26 are the focal points of the ellipse and are eccentric from the center of the ellipse. Therefore, the fluctuation cycle of the torque transmission ratio is one rotation (2π). is there. Further, the fluctuation waveform of the torque transmission ratio is sinusoidal. That is, assuming that the torque input to the first gear pair is Tin, the torque output from the first gear pair 20 is Tout, and the rotation angle is θ, Tout = Tin · R · sin θ + M (R and M are constants) Become.

  The second gear pair 22 includes a third gear 28 connected to the second gear 26 by the second shaft 34, and a fourth gear 30 meshing with the third gear 28 and connected to the crankshaft 52. Similarly to the first and second gears 24 and 26, the third gear 28 and the fourth gear 30 are also elliptical gears. However, unlike the first and second gears 24 and 26, the third gear 28 and the fourth gear 30 rotate around the elliptical centers O3 and O4. In the present embodiment, the phase angle α of the third gear 28 with respect to the second gear 26 is about 45 degrees (1 / 4π). The meaning of the value of the phase angle α will be described in detail later.

  Also in the second gear pair 22, the torque transmission ratio fluctuates at a predetermined cycle, and the fluctuation waveform is a sine wave. However, in the case of the second gear pair 22, the rotational centers O3 and O4 of the two elliptical gears 28 and 30 are the elliptical center. Therefore, the fluctuation cycle of the torque transmission ratio is half rotation (1 / 2π). Therefore, when the input torque to the second gear pair 22 is Tin, the output torque from the second gear pair 22 is Tout, and the rotation angle is θ, Tout = Tin · R ′ · sin 2θ + M ′ (R ′, M ′ is Constant). In other words, the fluctuation cycle of the torque transmission ratio of the second gear pair 22 is ½ that of the first gear.

Next, the relationship between the torque transmission in the two-stage gear 18 and the reaction torque generated in the crankshaft 52 will be described with reference to FIG. 3A to 3D show the reaction torque T generated on the crankshaft 52, the torque Tm output from the motor 12, the torque Td transmitted to the crankshaft 52 via the transmission mechanism 15, and the motor 12, respectively. It is a graph which shows the vibration level. First, the reaction torque generated in the crankshaft 52 will be briefly described. As is well known, in a four-cycle engine, the crankshaft 52 performs four cycles, that is, compression, explosion, exhaust, and intake, during two rotations (4π). With this cycle variation, the reaction torque generated in the crankshaft 52 also varies. FIG. 3A is a graph showing fluctuations in the reaction torque generated in the crankshaft 52 during the two rotations and four cycles. As is clear from FIG. 3A, it can be seen that the reaction torque varies in a substantially sinusoidal shape with one rotation (2π) as one cycle. However, it is not an accurate sine wave but a modified sine wave having large peaks at 1 / 4π and 7 / 4π and small peaks at 3 / 4π and 5 / 4π. This reaction torque T can be approximated by the following equation (1).

  Here, F is the force applied to the piston, L is the connecting rod length, r is the crank radius, and φ is the crank angle. F, L, and r are constants. The reaction force torque T generated in the crankshaft 52 causes vibration and noise of the motor 12 and the like. Such vibration and noise are not only unpleasant for the passenger of the vehicle on which the engine 50 is mounted, but may also adversely affect the vehicle and the engine 50. Therefore, it has been conventionally desired to reduce vibrations based on the reaction force torque T. In particular, an engine or the like mounted on a hybrid vehicle is ignited at a relatively high rotation speed. However, if the engine speed is high, the generated reaction force torque T increases. For this reason, in an engine that is ignited at such a high speed, reducing vibrations based on the reaction force torque T is one of the important issues.

  In the present embodiment, in order to reduce vibration and the like based on the reaction force torque T, the torque Tm output from the motor 12 is converted so as to cancel the reaction force torque T and transmitted to the crankshaft 52. Specifically, the fluctuation cycle of the torque transmission ratio of the second gear pair 22 is set to ½ that of the first gear pair 20, and the second gear pair 22 is about 45 to the first gear pair 20. The configuration has a phase difference of degrees. As a result, the reaction force torque T can be canceled and vibrations and the like can be greatly reduced. This will be described with reference to FIGS. 4 is a diagram showing the positional relationship of the first gear pair 20, and FIG. 5 is a diagram showing the positional relationship of the second gear pair 22.

First, the torque transmission characteristics of the first gear pair 20 will be described. As described above, the first gear 24 and the second gear 26 constituting the first gear pair 20 are elliptic gears having the same shape, and the rotation centers O1 and O2 are elliptical focal points. The torques applied to the first gear 24 and the second gear 26 are Ta and Tb, the distances from the rotation center to the meshing point X are Ra and Rb, and the rotation angles are θ and ψ, respectively. The center-to-center distance is R, and the long axes of both gears are m and n. In the initial state, θ = ψ = 0. At this time, Equation (2) is established from the balance of forces, and Equation (3) is established from the polar coordinate representation of the ellipse.

Here, since R = Ra + Rb (constant), if the above equation (3) and θ = ψ = 0 are substituted into this equation, equation (4) can be derived.

Then, when Expression (3) and Expression (4) are substituted into Expression (2) and the output torque Tb of the second gear is expressed by the expression of the rotation angle ψ of the second gear, Expression (5) is obtained.

  Here, the torque Ta applied to the first gear 24 is a constant torque output from the motor 12 and amplified by the link gear 16 (Ta = N · Tm, N: link gear reduction ratio, Tm: motor output) torque). That is, according to the first gear pair 20 including the pair of elliptical gears 24 and 26 that are the points where the rotation centers O1 and O2 are decentered from the center of the ellipse (ellipse focal point), the torque Tm output from the motor 12 is sine. It can be seen that the torque can be converted to a fluctuating torque.

Next, the torque transmission characteristics of the second gear pair 22 will be described with reference to FIG. The third gear 28 and the fourth gear 30 constituting the second gear pair 22 are elliptic gears having the same shape, and the center of the ellipse is set as the rotation centers O3 and O4. The torque applied to the third gear 28 and the fourth gear 30 is Tc, Td, the distances from the rotation centers O3, O4 to the meshing point X ′ are Rc, Rd, the rotation angles are τ, φ, both gears 28, The distance between the rotation centers of 30 is R ′, and the long axes of both gears 28 and 30 are m ′ and n ′. In the initial state, τ = 0 and φ = 1 / 2π. At this time, Equation (6) is established from the balance of forces, and Equation (7) is established from the polar coordinate representation of the ellipse.

Here, R ′ = Rc + Rd (constant). By substituting the above equation (7) and τ = 0, φ = 1 / 2π into this equation, the following equation (8) can be derived.

Then, when Expressions (7) and (8) are substituted into Expression (6) and the output torque Td of the fourth gear 30 is expressed by the expression of the rotation angle τ of the third gear 28, Expression (9) is obtained. .

Here, the torque Tc applied to the third gear 28 is the torque Tb output from the second gear 26, and the equation Tc = Tb is established. Further, when the phase angle between the second gear 26 and the third gear 28 is α, the equation ψ = τ−α is established. Therefore, the following equation (10) is obtained by substituting equation (5) and ψ = τ−α into equation (9).

Next, the relationship between the angle τ of the third gear 28 and the angle φ of the fourth gear 30 can be expressed by the following equation (11) from the equations (7) and (8).

And if this formula (11) is substituted into formula (10), formula (12) will be obtained.

Here, ε and ε ′ are constants. The torque Ta transmitted from the link gear 16 is also constant. Therefore, Expression (12) can be rewritten as the following Expression (13).
Td = Asinφ + Bsin2φ + C (13)

  This equation (13) shows the torque transmission characteristic of the two-stage gear 18. As can be seen from Equation (13), the two-stage gear 18 converts the constant torque Ta transmitted from the link gear 16 into a deformed sine wave.

Here, the equation (13) is compared with the equation (1) indicating the reaction torque T generated in the crankshaft 52. It can be seen that the first and second terms in equation (13) are proportional to sin φ and sin 2φ, as in equation (1). Therefore, by adjusting ε, ε ′, and Ta so that A = Fr and B = Fr ² / 2L, the reaction force torque T can be canceled by the output torque Td from the fourth gear 30. On the other hand, C, which is a constant value regardless of the angle, is a torque for rotating the crankshaft 52. The crankshaft 52 is rotated by the torque corresponding to C, and the engine is started.

  FIG. 3C shows the output torque Td from the fourth gear 30. When FIG. 3C is compared with FIG. 3A illustrating the reaction force torque T, it can be seen that both torques have very similar fluctuation modes. Therefore, most of the reaction force torque T is canceled by the output torque Td. As a result, the vibration level generated in the motor can be greatly reduced as shown in FIG.

  That is, in the starting device 10, by providing a plurality of elliptical gear pairs in the transmission mechanism 15 that transmits the torque from the motor 12 to the crankshaft 52, it is possible to cancel the reaction force torque that fluctuates in a complicated manner. 12 vibrations can be prevented. In this embodiment, two gear pairs are used, but a larger number of gear pairs may be used. That is, in this embodiment, the engine 50 for a four-cycle four-cylinder engine is a start target. However, if the number of cylinders or the like is changed, the variation mode of the generated reaction force torque is also changed. In that case, what is necessary is just to adjust the number of gear pairs, a phase angle, etc. so that the torque according to the fluctuation | variation aspect of the reaction force torque can be output. Moreover, you may provide a gear between each gear pair as needed. By providing the gear, the fluctuation cycle of the torque transmission ratio of each gear pair can be flexibly changed, so that it is possible to cope with reaction force torque that fluctuates more complicatedly. Further, in the present embodiment, an elliptical gear pair that is relatively easy to handle is used. However, other shapes of non-circular gears may be used as long as the torque transmission ratio fluctuates in a predetermined cycle.

1 is a schematic configuration diagram of an engine starter according to an embodiment of the present invention. It is a figure which shows the structure of a two-stage gearwheel. It is a figure which shows the reaction torque T of a crankshaft, the output torque Tm of a motor, the output torque Td from a two-stage gear, and the vibration level of a motor, respectively. It is a figure which shows the positional relationship of a 1st gear pair. It is a figure which shows the positional relationship of a 2nd gear pair.

Explanation of symbols

  10 starter, 12 motor, 14 pinion, 15 transmission mechanism, 16 link gear, 18 double gear, 20 first gear pair, 22 second gear pair, 24 first gear, 26 second gear, 28 third gear, 30 Fourth gear, 32 First shaft, 34 Second shaft, 50 Engine, 52 Crankshaft, O1, O2, O3, O4 Rotation center, R, R 'Distance between rotation centers.

Claims (7)

A transmission mechanism that transmits torque from a starter motor to a crankshaft of an engine,
A first gear pair comprising a pair of non-circular gears, and with the rotation of the pair of non-circular gears, the torque transmission ratio varies in a first variation period;
The second gear is composed of a pair of non-circular gears connected to the first gear pair, and the torque transmission ratio fluctuates in a second fluctuation period that is different from the first fluctuation period as the pair of non-circular gears rotate. A pair of gears,
With
The ratio of the fluctuation period between each gear pair and the value of the phase angle between each gear pair are the reaction force torque generated on the crankshaft by the torque output from the transmission mechanism when a constant torque is input from the motor to the transmission mechanism. A transmission mechanism characterized by being set to a value corresponding to torque. The transmission mechanism according to claim 1,
A transmission mechanism characterized in that the torque conversion ratio of each gear pair varies in a sine wave shape. The transmission mechanism according to claim 2,
A non-circular gear constituting each gear pair is an elliptical gear. The transmission mechanism according to claim 3,
When F≈αsinθ + βsin2θ holds when the reaction torque generated in the crankshaft is F, α, β are constants, and θ is the crank angle,
The second fluctuation period is 1/2 of the first fluctuation period,
The phase angle of the second gear pair with respect to the first gear pair is 1 / 4π. The transmission mechanism according to claim 4,
A pair of elliptical gears constituting the first gear pair are both in the same shape, and a point eccentric from the center of the ellipse is the center of rotation,
A pair of elliptical gears constituting the second gear pair have the same shape, and the transmission mechanism is characterized in that the center of the ellipse is the center of rotation. The transmission mechanism according to claim 4 or 5,
A transmission mechanism, wherein the crankshaft is a crankshaft of a four-cycle four-cylinder engine. An engine starter that forcibly rotates a crankshaft to start an engine,
A starter motor that outputs the driving force of rotation of the crankshaft;
A transmission mechanism that transmits the torque output from the starter motor to the crankshaft;
And the transmission mechanism is at least
A first gear pair comprising a pair of non-circular gears, and with the rotation of the pair of non-circular gears, the torque transmission ratio varies in a first variation period;
The second gear is composed of a pair of non-circular gears connected to the first gear pair, and the torque transmission ratio fluctuates in a second fluctuation period that is different from the first fluctuation period as the pair of non-circular gears rotate. A pair of gears,
With
The ratio of the fluctuation period between each gear pair and the value of the phase angle between each gear pair are the reaction force torque generated on the crankshaft by the torque output from the transmission mechanism when a constant torque is input from the motor to the transmission mechanism. The starting device is set to a value corresponding to torque.

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