JP2002349283A - Balancer mechanism for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a balancer mechanism for an internal combustion engine for reducing vibration of the internal combustion engine, causing no adverse influence of hardly starting the internal combustion engine even when lubricating oil is put in a low temperature state such as starting time of the internal combustion engine in an unwarmed state, and obtaining the internal combustion engine superior in a starting characteristic. SOLUTION: This balancer mechanism has a balance shaft 50 for reducing the vibration of the internal combustion engine 2 by axially rotating an eccentric mass part formed so as to be eccentric to the axis, and a rotation transmitting means 51 for rotating the balance shaft 50 by transmitting rotation of a crankshaft 3 to the balance shaft 50, is arranged so that at least a part of the eccentric mass part is soaked in the lubricating oil 14 stored inside an oil pan 5 arranged under the crankshaft 3, and is characterized in that the rotation transmitting means 51 selectively switches driving and nondriving of the balance shaft 50 by a temperature sensitive member 55, and transfers to a driving state when the temperature sensitive member 55 is deformed by sensing a temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balancer mechanism for an internal combustion engine for reducing vibration of the internal combustion engine.

[0002]

2. Description of the Related Art Generally, when an internal combustion engine is operated, vibration is generated by reciprocating motion of a piston or the like. This is because unbalanced inertial force and couple remain due to the cylinder arrangement. For example, in the case of an in-line four-cylinder internal combustion engine, a secondary component of the inertial force remains unbalanced, and vibration occurs.
In order to reduce these vibrations, the internal combustion engine is provided with a balance shaft having a balancer weight parallel to the crankshaft, and the balance shaft is driven and rotated by the crankshaft, thereby canceling the vibration of the internal combustion engine. It has been known.

Normally, such a balancer mechanism is disposed in a cylinder block or the like, like the crankshaft. In this case, lubrication stored in an oil pan disposed below the crankshaft due to space limitations. It is often arranged so that part of it is immersed in oil.
For example, as disclosed in Japanese Utility Model Laid-Open No. 5-30407, a balancer mechanism in which a balance shaft is disposed so that a balancer weight is immersed in lubricating oil is disclosed. In this balancer mechanism, a rotation transmitting means by meshing gears attached to the crankshaft and the balance shaft respectively drives and rotates the balance shaft.

[0004]

However, a balancer mechanism arranged so that a part thereof is immersed in the lubricating oil stored in the oil pan, for example, a balancer weight is immersed in the lubricating oil. In the balancer mechanism, resistance is generated by stirring the lubricating oil. In particular, when the lubricating oil is in a low temperature state, such as when the internal combustion engine is not warmed up, the viscosity of the lubricating oil is high, and the stirring resistance becomes large. Therefore, the lower the temperature of the lubricating oil, the higher the viscosity and the greater the rotational resistance of the balance shaft, resulting in an adverse effect such as difficulty in starting the internal combustion engine. Further, in order to improve the startability of the internal combustion engine, it is necessary to provide a higher-performance, higher-output starting / charging system such as, for example, increasing the output of the starter or increasing the injection fuel at the time of starting. Disadvantages may also occur. In addition, the need to reduce the vibration of the internal combustion engine by the balancer mechanism is generally high only in a specific rotation speed region where resonance occurs, and in a low-speed rotation region such as when the internal combustion engine is started, the vibration is originally high. Since there is little change in the vibration generation state due to the presence or absence of the operation of the balancer mechanism, the balancer mechanism is almost unnecessary. Therefore, in the low-speed rotation region, the influence of the reduction in power performance and fuel consumption due to the rotation resistance of the balance shaft becomes apparent.

The present invention has been made in view of the above circumstances,
In addition to reducing the vibration of the internal combustion engine, even when the lubricating oil is in a low temperature state, such as when starting the internal combustion engine that has not been warmed up, it does not cause adverse effects such as making the internal combustion engine difficult to start, An object of the present invention is to provide a balancer mechanism for an internal combustion engine capable of obtaining an internal combustion engine having excellent characteristics.

[0006]

According to a first aspect of the present invention, there is provided a balancer mechanism for an internal combustion engine which rotates an eccentric mass portion formed to be eccentric with respect to an axis around an axis. An oil pan disposed below the crankshaft, comprising: a balance shaft that reduces vibration of the internal combustion engine; and a rotation transmitting unit that transmits rotation of the crankshaft to the balance shaft to rotate the balance shaft. At least a portion of the eccentric mass portion is immersed in the lubricating oil stored in the rotary shaft, and the rotation transmitting means selectively switches between a driving state and a non-driving state of the balance shaft by a temperature-sensitive member. Wherein the temperature-sensitive member is deformed in response to a change in the temperature of the lubricating oil to switch between a driving state and a non-driving state of the balance shaft. And it features. Here, the “rotation transmitting unit” may be any unit that can transmit the rotation of the crankshaft to the balance shaft, such as a gear train, a toothed belt and a pulley, a chain and a sprocket. Further, the “temperature sensitive member” may be any material such as a bimetal or a shape memory alloy as long as it is deformed in response to a temperature change. The phrase “selecting the drive / non-drive state selectively using the temperature-sensitive member” means connecting and disconnecting the crankshaft and the balance shaft with the temperature-sensitive member. That is, when in the non-driving state, the crankshaft and the balance shaft are not connected to each other by the rotation transmitting means, and are free from each other, and the balance shaft does not rotate. Then, by the "temperature-sensitive member deforming in response to a change in the temperature of the lubricating oil", the rotation transmitting unit shifts to a state in which the crankshaft and the balance shaft are connected to each other, thereby enabling the rotational drive of the balance shaft. Things. The transition to the connection state may be any state, such as a state where the temperature-sensitive member itself is deformed so as to be engaged and a state where the temperature-sensitive member is deformed so as to increase friction at the connection part.

With this configuration, when the lubricating oil is in a low temperature state and has a high viscosity, such as when starting an internal combustion engine that is not warmed up, the rotation transmitting means connects the crankshaft to the balance shaft. The balance shaft does not rotate. Therefore, no rotational resistance is generated in the balance shaft. However, when the internal combustion engine is started and the internal combustion engine warms up, the temperature of the temperature-sensitive member in the rotation transmitting means also rises, and deformation of the temperature-sensitive member is induced. Connect the shaft. At this time, the temperature of the lubricating oil also increases, and the viscosity decreases,
There is no significant rotational resistance on the balance shaft. Also, before reaching a specific rotation speed region where resonance occurs,
Since the temperature of the internal combustion engine is sufficiently raised, the crankshaft and the balance shaft are reliably connected, and vibration can be reduced. Further, there is no need to provide a higher-performance and higher-output starting / charging system in order to improve the startability of the internal combustion engine, and an internal combustion engine having excellent starting characteristics can be easily realized. Even when the balancer mechanism for reducing vibration is unnecessary in a low-speed rotation region such as when the internal combustion engine is started, since the crankshaft and the balancer mechanism are not connected, the rotation resistance of the balance shaft in the low rotation speed region is reduced. Therefore, there is also an effect that it is possible to prevent a decrease in power performance and fuel efficiency due to the above. As described above, even when the lubricating oil is in a low temperature state, there is provided a balancer mechanism for an internal combustion engine capable of obtaining an internal combustion engine having excellent starting characteristics without causing adverse effects such as difficulty in starting the internal combustion engine. Is what you do.

According to a second aspect of the present invention, in the balancer mechanism for an internal combustion engine according to the first aspect, the rotation transmitting means transmits rotation from a crank gear attached to the crankshaft to a balance shaft gear attached to the balance shaft. By rotating the balance shaft, the temperature-sensitive member is deformed in response to a change in the temperature of the lubricating oil. It is characterized in that the shaft is switched to a driving / non-driving state. The balancer mechanism for an internal combustion engine according to a third aspect is characterized in that, in the second aspect, the temperature sensitive member uses a shape memory alloy.

According to the second and third aspects of the present invention, it is possible to realize a simple structure of the rotation transmitting means for selectively switching the driving / non-driving of the balance shaft by the temperature sensitive member. Therefore, even when the lubricating oil is in a low temperature state, it is possible to provide a balancer mechanism for an internal combustion engine that easily realizes an internal combustion engine with excellent starting characteristics without causing adverse effects such as difficulty in starting the internal combustion engine. it can.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a state in which a balancer mechanism 1 for an internal combustion engine (hereinafter, referred to as “balancer mechanism 1”) according to an embodiment of the present invention is used in an in-line four-cylinder internal combustion engine 2 (hereinafter, referred to as “internal combustion engine 2”). FIG. 2 schematically shows a connection state between the balancer mechanism 1 and the crankshaft 3. In addition,
The balancer mechanism 1 according to the present embodiment is particularly
Although shown for a case where the present invention is used for a cylinder internal combustion engine, the present invention is not necessarily limited to an in-line four-cylinder internal combustion engine, but can be applied to all internal combustion engines. Incidentally, in the case of a four-cylinder internal combustion engine such as a diesel engine, vibration is likely to occur due to high torque, and a balancer mechanism is often required.

Referring to FIG. 1, an internal combustion engine 2 using a balancer mechanism 1 according to the present embodiment includes a cylinder block 4 and an oil pan 5 disposed below the cylinder block 4. , Crankshaft 3
have. As shown in FIGS. 1 and 2, the balancer mechanism 1 has a balance shaft 50 and a rotation transmitting unit 51, and is mounted so that the balance shaft 50 is parallel to the crankshaft 3. In FIG. 1, a crankshaft 3 has a crank pulley 6 attached to a tip thereof, has a crankpin 7 and a flywheel 8, and is rotatably supported by a journal 10 in a bearing 10 in a cylinder block 4. ing. Also, the crankshaft 3 and the balance shaft 50
Are connected by the rotation transmission means 51.

1 and 2, a balance shaft 50 reduces the vibration of the internal combustion engine 2 by rotating the eccentric mass portions 16a, 16b formed so as to be eccentric with respect to the axis. Lubricating oil having a first balance shaft 1a and a second balance shaft 1b arranged in parallel, both of which are stored in an oil pan 5 arranged below the crankshaft 3. A part of the eccentric masses 16a and 16b is disposed so as to be immersed with respect to 14, and is rotatably supported in the casing 20.

The first balance shaft 1a has a shaft 15a, and one end of the shaft 15a has a rotation transmitting means 51 described later.
Is mounted. The mounting configuration of the balance shaft gear 13 will be described later in detail. The other end of the shaft 15a is formed with a semi-cylindrical eccentric mass portion 16a formed to be eccentric in mass with respect to the axis. A gear 17a is fitted in the middle of the shaft 15a, and meshes with a gear 17b fitted to a second balance shaft 1b described later. The shaft 15a is provided with bearings 18a and 18b rotatably supported by the bearings. The bearings 18a are provided on the balance shaft gear 13 side and supported by the bearings 19a. , A bearing 19 provided between the gear 17a and the eccentric mass 16a.
b (see FIG. 1).

In FIG. 2, the second balance shaft 1b
Has a shaft 15b arranged in parallel with the shaft 15a of the first balance shaft 1a, and one end of the shaft 15b is provided with a gear 17b that meshes with the gear 17a. The other end of the shaft 15b is provided with a semi-cylindrical eccentric mass 16b similar to the eccentric mass 16a. Also,
A bearing 18c supported by a bearing (not shown) is provided between the gear 17a and the eccentric mass 16b. The balance shaft 50 is configured as described above, and is driven via the rotation transmission means 51 described later, so that the shaft 15a rotates, and with this rotation, the eccentric mass portion 16a also rotates. When the gear 17b is driven, the shaft 15b also rotates. Therefore, the eccentric mass 16b rotates in the opposite direction to the eccentric mass 16a. With these configurations, vibration generated in the internal combustion engine 2 is reduced.

Next, the rotation transmitting means 51 for transmitting the rotation of the crankshaft 3 to the balance shaft 50 to rotate the balance shaft 50 will be described. 1 and 2, the rotation transmitting means 51 includes a crank gear 11 attached to the crankshaft 3, a balance shaft gear 13 attached to the shaft 15a of the first balance shaft 1a, and an idle gear located between these. 12 are provided. The crank gear 11 is fitted on the crankshaft 11 and the crank gear 11
Are meshed with the idle gear 12, and the idle gear 12 is further meshed with the balance shaft gear 13. As described above, the rotation transmitting unit 51 transmits the rotation from the crank gear 11 to the balance shaft gear 13 to enable the rotation of the balance shaft 50, and the balance shaft 50 is driven by the crank shaft 3. Thus, the vibration of the internal combustion engine 2 is reduced. At this time, the ratio of the number of teeth of the balance shaft gear 13 to that of the crank gear 11 is set to 2: 1 to reduce the vibration of the secondary component as described in the description of the related art.

The rotation transmitting means 51 has a structure in which switching between driving and non-driving of the balance shaft 50 is selectively performed by a temperature-sensitive member 55.
5 changes to a driving state by deforming in response to a temperature change. The structure for mounting the balance shaft gear 13 to the shaft 15a, which specifically realizes this configuration, will be described in detail. FIG. 3 and FIG.
FIG. 3 shows a mounting structure of the balance shaft gear 13 and the shaft 15a.
FIG. 4 shows a state in which the balance shaft 50 is in a drivable state in which the balance shaft 50 is in a drivable state. Is shown. In addition,
FIGS. 3A and 4A show a part of the shaft 15a and an axial cross section of the balance shaft gear 13. FIGS. 3B and 4B show FIGS. a) and FIG.
(A) is a diagram as viewed from the left.

The shaft 15a is machined so that a small-diameter portion 52 having a smaller shaft diameter than other portions is formed at the shaft end. At one place on the outer periphery of the small diameter portion 52,
A key groove 53 extending in the axial direction is machined. Also,
The small-diameter portion 52 of the shaft 15a includes the balance shaft gear 13
Is loosely fitted. The balance shaft gear 13 has a key groove 54 formed at one portion of an inner peripheral portion that is loosely fitted to the shaft 15a. A temperature sensitive member 55 is attached to the key groove 53. This temperature sensitive member 55
Uses a shape memory alloy, and in the present embodiment, has a short columnar shape having a dome-shaped cross section. And since it is formed of a shape memory alloy, it is deformed according to a temperature change, and its shape changes. FIG. 3 shows the state after the deformation. In FIG. 3, the temperature-sensitive member 55 has a dome-shaped cross section having a higher height,
The shape is deformed so that the width is reduced. The shape change from the state of FIG. 4 to the state of FIG. 3 occurs as the temperature of the temperature-sensitive member 55 increases. Note that the temperature-sensitive member 55 is
It is attached to the side so as to allow deformation according to the temperature change.

In FIG. 4, since the temperature-sensitive member 55 is in a state before the temperature rise and the height of the dome-shaped portion is low, the shaft 15a and the balance shaft gear 13 are loosely fitted to each other. Yes, not connected. Therefore, as the crankshaft 3 rotates, the crank gear 1
1, the idle gear 12 and the balance shaft gear 13 rotate, but the balance shaft 50 does not rotate.

However, in FIG. 3, the temperature-sensitive member 55 is deformed as the temperature rises, and the height of the dome-shaped portion is increased, so that the temperature-sensitive member 55 is fitted so as to engage with the key groove 54 of the balance shaft gear 13. In addition, the balance shaft gear 13 and the shaft 15a are connected. Thus, the rotation of the crankshaft 3 is transmitted to the balance shaft 50 through the rotation transmitting means 51. In other words, the rotation transmitting means 51 increases the temperature of the temperature-sensitive member 55 in accordance with a change in the temperature of the lubricating oil 14 and deforms.
The balance shaft gear 13 can be engaged with and disengaged from the balance shaft 1, and the balance shaft 1 can be switched between a driving state and a non-driving state.

Next, the operation of the balancer mechanism 1 according to the embodiment configured as described above will be described. First, in FIG. 1, the internal combustion engine 2 is started from a state in which the internal combustion engine is not warmed up. At this time, since the temperature of the internal combustion engine 2 is low, the lubricating oil 14 in the oil pan 5 is also in a low temperature state,
The viscosity is significantly higher than during operation of the internal combustion engine 2. At this time, since the balance shaft 50 immersed in the lubricating oil 14 is also in a low temperature state like the lubricating oil 14, the temperature sensitive member 55 is in a state before being deformed due to a temperature rise as shown in FIG. The shape of the dome-shaped portion is low. Therefore, the temperature sensitive member 5
5 is not engaged with the key groove portion 54 of the balance shaft gear 13, the balance shaft gear 13 remains loosely fitted to the shaft 15a, and the rotation transmitting means 51 is connected to the crankshaft 3 and the balance shaft 50. Is not concatenated.

1 and 2, when the internal combustion engine 2 is started, a piston (not shown) reciprocates in the cylinder, and a connecting rod (not shown) connected to the piston is connected to the crank pin 7. The crankshaft 3 rotates with the reciprocation of the piston. This rotational movement of the crankshaft 3 is transmitted to the idle gear 1 by the crank gear 11.
2 to the balance shaft gear 13. However, as described above, the temperature sensitive member 55
Since the state before the temperature rise is maintained, the balance shaft gear 13 and the shaft 15a are not connected, and the balance shaft gear 13 idles with respect to the shaft 15a, so that the balance shaft 50 does not rotate. That is, the balance shaft 50 is not driven. In the low-speed rotation region when the internal combustion engine 2 is started, vibration due to resonance does not occur.
Is not required.

Shortly after the start, the temperature of the internal combustion engine 2 rises, and accordingly, the temperature of the lubricating oil 14 in the oil pan 5 also rises. Thereby, the rotation transmitting means 51
, The temperature of the temperature-sensitive member 55 also increases, and the deformation of the temperature-sensitive member 55 is induced. That is, the temperature-sensitive member 55 changes from the state shown in FIG. 4 to the state shown in FIG. 3, and is deformed so that the height of the dome-shaped portion increases, and the key groove portion 54 of the balance shaft gear 13 and the key Groove 5
When they face each other, they engage so as to fit into the key groove portion 54. Thus, the rotation transmitting means 51
The crankshaft 3 and the balance shaft 50 are connected, and the balance shaft 50 shifts to a driving state.
At this time, since the temperature of the lubricating oil 14 has risen and the viscosity has fallen, no great rotational resistance occurs in the balance shaft 50. In addition, since the temperature of the internal combustion engine 2 has risen sufficiently before reaching a specific rotation speed region where resonance occurs, the dimensions and physical properties of the temperature sensitive member 55 and the shapes of the key groove portions 53 and 54 are changed. With proper selection, the crankshaft 3 and the balance shaft 50 are securely connected, and vibration can be reduced.

When the balance shaft 50 is in the above-described driving state, the first balance shaft 1a rotates together with the balance shaft gear 13. At this time,
When the gear 17b is driven by the gear 17a, the second balance shaft 1b is driven by the first balance shaft 1a.
And rotate in the opposite direction. Here, both the first balance shaft 1a and the second balance shaft 1b rotate at twice the rotation speed with respect to the crankshaft 3, and the two eccentric mass portions generate a large inertial force. Can be reduced so as to cancel out the secondary component of the vibration generated in.

As described above, according to the balancer mechanism 1 for an internal combustion engine according to this embodiment, even when the lubricating oil is in a low temperature state, the internal combustion engine does not have an adverse effect such as being difficult to start. An internal combustion engine having excellent characteristics can be obtained, and a balancer mechanism for an internal combustion engine that contributes to prevention of reduction in power performance and fuel efficiency due to rotational resistance of a balance shaft can be provided. Further, in order to improve the startability of the internal combustion engine, there is no need to provide a higher-performance and higher-output starting / charging system, and an internal combustion engine having excellent starting characteristics can be easily realized.

The above is an explanation of the present embodiment, but the embodiment is not limited to the above, and may be modified as follows, for example. (1) The temperature-sensitive member is not limited to a shape memory alloy, but may be formed of any other material that can be deformed in response to a temperature change, such as another temperature-sensitive member such as a bimetal. There may be. Further, regarding the shape of the temperature-sensitive member and the form of the portion to be engaged with the temperature-sensitive member,
The embodiment is not necessarily limited to the one as long as the engagement and detachment can be performed according to the temperature change.

(2) In this embodiment, the temperature sensitive member is deformed in accordance with the temperature and engages with and removes from the key groove of the balance shaft gear. However, this is not necessarily the case, and the temperature-sensitive member deforms in response to a change in temperature, so that the rotation transmitting means shifts to a state in which the crankshaft and the balance shaft are connected, and the balance shaft can be rotated. It may have any configuration as long as For example, the rotation transmitting means has a clutch plate, a temperature-sensitive member disposed between the clutch plates is deformed, and engages and disengages with an engaged portion formed on the clutch plate,
The clutch plate itself may be deformed according to the temperature so as to increase the friction at the connecting portion.

(3) In this embodiment, the rotation transmitting means has a configuration including a crank gear, an idle gear, and a balance shaft gear. However, the present invention is not limited to this. Any device that can transmit rotation to a balance shaft, such as a toothed belt, a pulley, a chain, and a sprocket, which can transmit rotation of a crankshaft to a balance shaft, may be used.

(4) The balance shaft according to the present embodiment is configured to have two shafts, but this need not be the case, and the balance shaft may have only one shaft. .

(5) The shape of the eccentric mass portion is formed in a semi-cylindrical shape, but this is not necessarily the case, and any shape may be used as long as it is eccentric in mass with respect to the axis. Such a thing may be used. For example, a cylindrical mass part may be attached to the balance shaft axis center while being shifted from the center of the cylinder.

[0030]

According to the first aspect of the present invention, when the lubricating oil is in a low temperature state and has a high viscosity, such as when starting an internal combustion engine that is not warmed up, the rotation transmitting means balances the crankshaft with the crankshaft. Not connected to the shaft,
The balance shaft does not rotate. Therefore, no rotational resistance is generated in the balance shaft. However, when the internal combustion engine is started and the internal combustion engine warms up, the temperature of the temperature-sensitive member in the rotation transmitting means also rises, and this deformation of the temperature-sensitive member is induced. Connect the shaft. At this time, since the temperature of the lubricating oil also increases and the viscosity decreases, no great rotational resistance occurs in the balance shaft. In addition, by the time the internal combustion engine has sufficiently heated up to the specific rotation speed region where resonance occurs, the crankshaft and the balance shaft are securely connected,
Vibration can also be reduced. Furthermore, there is no need to provide a higher-performance, higher-output starting / charging system in order to improve the starting performance of the internal combustion engine, and an internal combustion engine having excellent starting characteristics can be easily realized. Even when the balancer mechanism for reducing vibration is not required in a low-speed rotation region such as when the internal combustion engine is started, the crankshaft and the balancer mechanism are not connected to each other. Therefore, there is also an effect that it is possible to prevent a decrease in power performance and fuel efficiency due to the above. As mentioned above,
Even when the lubricating oil is in a low temperature state, it is possible to provide a balancer mechanism for an internal combustion engine capable of obtaining an internal combustion engine having excellent starting characteristics without causing adverse effects such as difficulty in starting the internal combustion engine.

According to the second and third aspects, it is possible to realize, with a simple structure, a rotation transmitting unit that selectively switches between driving and non-driving of the balance shaft by using a temperature sensitive member. Therefore, even when the lubricating oil is in a low temperature state, it is possible to provide a balancer mechanism for an internal combustion engine that easily realizes an internal combustion engine with excellent starting characteristics without causing adverse effects such as difficulty in starting the internal combustion engine. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which a balancer mechanism for an internal combustion engine according to the present invention is attached to an internal combustion engine.

FIG. 2 is a diagram illustrating a connection state between a balancer mechanism for an internal combustion engine and a crankshaft according to the present invention.

FIG. 3 is a diagram illustrating a connection structure between a balance shaft and a balance shaft gear in the balancer mechanism for an internal combustion engine according to the present invention.

FIG. 4 is a diagram illustrating a connection structure between a balance shaft and a balance shaft gear in the balancer mechanism for an internal combustion engine according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 balancer mechanism for internal combustion engine 1a first balance shaft 1b second balance shaft 2 in-line four-cylinder internal combustion engine 3 crankshaft 5 oil pan 11 crank gear 12 idle gear 13 balance shaft gear 14 lubricating oil 15a, b shaft 16a, b eccentric mass Part 50 Balance shaft 51 Rotation transmitting means 53, 54 Key groove part 55 Temperature sensitive member

Claims (3)

[Claims] 1. A balance shaft for rotating an eccentric mass portion formed to be eccentric with respect to an axis about an axis to reduce vibration of an internal combustion engine, and transmitting rotation of a crankshaft to the balance shaft. And a rotation transmitting means for rotating the balance shaft. The eccentric mass part is immersed in lubricating oil stored inside an oil pan disposed below the crankshaft. The rotation transmitting means selectively switches between a driving state and a non-driving state of the balance shaft by a temperature-sensitive member, and the temperature-sensitive member deforms in response to a temperature change of the lubricating oil. To drive the balance shaft
A balancer mechanism for an internal combustion engine that switches between non-driving states. 2. The rotation transmission means rotates the balance shaft by transmitting rotation from a crank gear attached to the crankshaft to a balance shaft gear attached to the balance shaft. The temperature responsive member is deformed in response to the temperature change, thereby engaging and disengaging the balance shaft gear with the balance shaft, and switching the balance shaft to a driving / non-driving state. The balancer mechanism for an internal combustion engine according to claim 1. 3. The balancer mechanism for an internal combustion engine according to claim 2, wherein said temperature responsive member uses a shape memory alloy.