JPH06129492A - Balance shaft driver of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption by applying braking force to a balance shaft in time of low engine speed and inhibiting this braking force at a speed range of more than the specified engine speed. CONSTITUTION:An annular chamber 17 is installed in the circumference of each end of two balance shafts 3, 4, while hydraulic pressure out of an oil pump is conducted into this annular chamber 17, and a relief valve 12 is installed in an oil exhaust passage 15 out of the annular chamber 17, and a rotation checking force imparting means imparting rotation checking force to the balance shafts 3, 4 only at a time when the relief valve 12 is closed is installed in this annular chamber 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear type balance shaft drive device for an internal combustion engine, and more particularly to a noise reduction structure thereof.

[0002]

2. Description of the Related Art In an internal combustion engine, for example, a four-cylinder internal combustion engine, when the pistons of the first and fourth cylinders are at the top dead center position, the pistons of the second and third cylinders are at the bottom dead center position.
Unbalanced upward force remains due to unbalanced inertial force due to reciprocating inertial mass of piston / connecting rod, etc. Also, when the pistons of Nos. 2 and 3 cylinders are at the top dead center position, the same unbalanced upward force remains. Since the force remains, the vertical vibration occurs twice per one rotation of the crankshaft.

In order to obtain vibration due to unbalance of inertial force due to reciprocating inertial mass of piston / connecting rod or the like peculiar to the four cylinders, there is an unbalanced mass that balances with unbalance of inertial force due to reciprocating inertial mass of piston / connecting rod or the like. The balance shaft is installed and the crankshaft 1
A balancer configured to rotate twice for each rotation may be provided. However, if only one balance shaft is provided, vertical vibration that occurs due to imbalance of inertial force due to reciprocating inertial mass such as piston / connecting rod will disappear, but horizontal vibration will occur due to unbalanced mass of the balance shaft itself. In order to eliminate this, two balance shafts are provided, arranged side by side and rotated in reverse so as to cancel the left-right unbalance.

When two balance shafts are arranged below the crankshaft and the balance shaft is rotated in conjunction with the crankshaft, the rotation transmission method is as follows.
Conventionally, there are a chain drive type, a belt drive type, and a gear drive type. For example, Japanese Utility Model Publication No. 58-35880, Japanese Patent Application Laid-Open No. 58-160647, and Japanese Utility Model Application Laid-Open No. 1-102545 show a gear drive type. The gear drive type has less mechanical loss than the chain drive type and belt drive type, and it is possible to add a balancer relatively easily without adding large changes to the cylinder block structure of the existing engine without balancer. Although it has advantages, it has the following problems, and measures must be taken against them.

That is, the gear drive type balancer generates a comparatively large amount of rattling noise (hereinafter referred to as rattling noise). This rattling noise is loud near idling and does not occur at high rotation speeds. As one of the causes of the rattling noise, it is conceivable that the teeth of the gear collide with the teeth of another gear meshing with the teeth. For example, when the crankshaft switches from acceleration in the explosion stroke to deceleration, inertial force causes the rotation of the balance shaft to exceed the rotation of the crankshaft. Move
Generates a collision hit sound. When switching from deceleration to acceleration, a collision striking sound occurs due to the opposite phenomenon.

In the gear-driven balancer, in order to reduce the rattling noise caused by the gear hitting sound, the applicant of the present invention first applies a braking force of constant operation to the balance shaft.
A countermeasure has been proposed in which tooth engagement always occurs only on one side of the tooth (Japanese Patent Application No. 3-148114).

[0007]

However, the following problems arise in noise reduction measures by applying a braking force. (1) Since the friction is always applied, the fuel efficiency and power performance of the internal combustion engine deteriorate. (2) Braking force changes over time due to wear of springs and shafts due to sliding, and noise reduction capability changes.

An object of the present invention is to provide a balance shaft drive device for an internal combustion engine, which reduces a rattling noise, which is particularly problematic in a low speed rotation range such as idling, without substantially impairing the fuel consumption and power performance of the internal combustion engine. The purpose is to provide.

[0009]

In order to achieve the above object, a balance shaft drive device for an internal combustion engine according to the present invention comprises the following. That is, a gear-driven balance shaft that is rotationally driven from a crankshaft via gears, an annular chamber that extends around the outer periphery of a portion of the balance shaft in the axial direction, and an oil that supplies oil from an oil pump to the annular chamber. A passage, a relief valve provided in the oil discharge passage from the annular chamber to the oil pan and opened at a predetermined hydraulic pressure or more, and a rotation restraining force applied to the balance shaft when the relief valve provided in the annular chamber is closed. A balance shaft drive device for an internal combustion engine, comprising: a rotation restraining force applying means for substantially eliminating the rotation restraining force when the relief valve is opened.

[0010]

The rattling noise of gears is often heard in the vicinity of idling, where the rotation fluctuation of the crankshaft is large, and the rotation fluctuation is small in the high-speed rotation range, so that it does not occur. For this reason, the rotation inhibiting force is applied to the balance shaft only at low speed rotation (about 1000 rpm or less), and the rotation inhibiting force applied to the balance shaft in other cases is reduced to reduce fuel consumption and power performance. I want to prevent it.

In the present invention, since the oil from the oil pump is guided to the annular chamber through the oil passage, a large hydraulic pressure is applied to the relief valve to open the relief valve when the engine rotates at a high speed, and the relief valve opens when the engine rotates at a low speed. The hydraulic pressure becomes small and the relief valve closes. Since the rotation restraining force applying means applies the braking force to the balance shaft only when the relief valve is closed, that is, only when the engine is rotating at low speed, the rattling noise at low speed rotation is suppressed. On the other hand, during high-speed rotation, the relief valve opens, and the balance shaft rotation restraining force of the rotation restraining force applying means almost disappears, so the engine generated power is not consumed by this braking force and good fuel economy is maintained. It

[0012]

1 to 7 show a balance shaft drive system for an internal combustion engine according to a preferred embodiment of the present invention. As shown in FIGS. 1 to 4, the crankshaft 1 is rotatably supported by the cylinder block 20, and the balance shaft 3 is provided below the crankshaft 1 at symmetrical positions.
4 is rotatably arranged. Crankshaft 1,
The balance shafts 3 and 4 extend parallel to each other in the longitudinal direction of the engine. The balance shafts 3 and 4 are disposed below only the central portion in the longitudinal direction of the crankshaft 1, and are disposed inside the oil pan 21. The balance shafts 3 and 4 have unbalanced masses 3a and 4a, respectively, and the total of them is balanced with the unbalanced inertial force due to the reciprocating inertial mass of the piston / connecting rod in the vertical direction of the engine.

Of the two balance shafts 3, 4, one balance shaft 3 is gear-driven by the crankshaft 1, and the other balance shaft 4 is gear-driven by the one balance shaft 3. The balance shafts 3 and 4 rotate in mutually opposite directions, whereby the unbalance masses 3a and 4a are balanced in the left-right direction. The rotation transmission from the crank gear 1 to the balance shaft 3 is performed by the engagement of the drive gear 2 of the crank gear 1 and the balancer gear 5 of the balance shaft 3, and the rotation transmission from the balance shaft 3 to the other balance shaft 4 is performed. The balancer gear 5 of No. 3 and the balancer gear 6 of the balance shaft 4 are engaged with each other. The meshing position between the drive gear 2 and the balancer gear 5 and the meshing position between the balancer gear 5 and the balancer gear 6 are shifted in the engine longitudinal direction as shown in FIG. These gear meshing parts are inside the oil pan 21, and are parts where a large amount of oil is applied.

As shown in FIGS. 5 to 7, the balance shafts 3 and 4 are supported by the balancer housing 16 via bearings 22, and the ends thereof bulge outward in the radial direction to form the flanges 3a and 4a. Is formed. A friction case 8 having an L-shaped cross section is fixed to the end of the balancer housing 16 so as to surround the outer peripheral portions of the end flanges of the balance shafts 3 and 4. An annular chamber 17 is formed around the outer peripheries of the flanges 3a, 4a at the ends of the balance shafts 3, 4, and the annular chamber 17 is surrounded by the friction case, the balancer housing end face, and the balance shaft flanges 3a, 4a. It consists of an open space. The annular chamber 17 is separated from the outside except the oil passages 10 and 11 and the oil discharge passage 15.

The oil passage 11 opens into the annular chamber 17, extends radially inward and is connected to the oil passage 10. Oil passage 10
Extends axially on the axis of the balancer shafts 3, 4. Although not shown, the oil passage 10 is connected to an oil hole formed in the cylinder block 20 via the journal portions of the balancer shafts 3 and 4 and the journal bearing on the cylinder block side. The oil that has been pumped up and pressurized by the oil pump from the oil pan flows into the oil hole, and part of it is supplied to the annular chamber 17 through the oil passages 10 and 11.

An oil discharge passage 15 formed in the friction case 8 is opened in the annular chamber 17, and a relief valve 12 is provided in the oil discharge passage 15. The relief valve 12 includes a valve case 23 having a hole 24 formed in a side wall thereof, a valve body 25 that slides in the valve case 23, and a spring 13 that biases the valve body 25 against hydraulic pressure. When the oil pressure in the annular chamber 17 is low, the valve body 25 urged by the spring 13 closes the hole 24. When the oil pressure is high, the spring 13 is compressed and the valve body 25 closes the hole 24. The strength of the spring 13 is determined so as to come to the position where it opens.

The annular chamber 17 is provided with a rotation inhibiting force applying means for imparting a rotation inhibiting force to the balance shafts 3 and 4 when the relief valve 12 is closed and for almost eliminating the rotation inhibiting force when the relief valve 12 is opened. ing.
The rotation restraining force applying means is, for example, as shown in FIG.
Radially extending grooves 18 formed on the rotating balance shafts 3 and 4, fins 9 inserted into and retracted from the grooves 18, and radially inwardly formed on the inner peripheral surface of the fixed friction case 8. Protruding portion 19 that smoothly protrudes
The oil discharge passage 15 is formed at a position slightly distant from the protrusion 19 in the direction opposite to the balance shaft rotation direction.

Therefore, when the relief valve 12 is closed and the oil discharge passage 15 is closed, the oil pushed in the rotational direction by the fins 9 protruding outward by the centrifugal force is
The pressure generated by the resistance, which is passed through the narrowed gap 26 between the protrusion 19 and the outer circumference of the balance shaft flange, acts in the direction of suppressing the rotation of the fin 9, and thus imparts a rotation suppressing force to the balance shafts 3 and 4. Further, when the relief valve 12 is opened and the oil discharge passage 15 is opened, the oil pushed by the fins 9 in the rotational direction is released.
Since the holes 24 are discharged into the external oil pan, the balance shafts 3 and 4 receive almost no rotation restraining force. Thus, the members such as the fins 9 constitute rotation restraining force applying means.

Next, the operation will be described. During low-speed rotation including idling (when the engine speed is about 1000 rpm or less), the oil pump rotated in conjunction with the crankshaft also has a low rotation speed, so the oil pressure is low, and thus the oil pressure in the annular chamber 17 is also low. Low. Therefore, the oil pressure pushing the valve body 25 of the relief valve 12 is small, the moving amount of the valve body 25 against the spring 13 is small, and the relief valve 12 is in the closed state. When the balance shafts 3 and 4 rotate in this state and the oil is pushed by the fins 9, all the oil passes through the small gap 26, so that a resistance force is generated and the back pressure rises, and this back pressure is applied to one side of the fins 9. Therefore, the balance shafts 3 and 4 act to suppress the rotation of the balance shafts 3 and 4. This is the same as when the brakes were applied,
Gear meshing always occurs on only one side, and rattle noise due to rotational fluctuation does not occur. In other words, the rattling noise that occurs when idling, which has conventionally occurred, disappears.

On the other hand, a predetermined number of revolutions or more, for example, about 100
In the rotation range of 0 rpm or more, the discharge pressure of the oil pump rises, the pressure of the annular chamber 17 rises accordingly, and the relief valve 12 opens. When the relief valve 12 is opened, the oil pushed by the fin 9 returns to the oil pan through the hole 24 of the relief valve 12 and causes almost no resistance. Therefore, the pressure applied to one side of the fin 9 for suppressing rotation is small, and the balance shafts 3 and 4 are hardly applied with rotation suppressing force.

[0021]

According to the present invention, since the relief valve is closed during idling and a rotation restraining force acts on the balance shaft, rattling noise of gear meshing does not occur, and the relief valve opens in a speed range of a predetermined number of revolutions or more. As a result, the balance shaft does not exert a rotation restraining force, so that deterioration of fuel efficiency is prevented.

[Brief description of drawings]

FIG. 1 is a front view of a balance shaft drive device for an internal combustion engine.

FIG. 2 is a front view showing only the gear in FIG.

3 is a side view of the gear of FIG. 2. FIG.

FIG. 4 is a plan view of an end portion of the internal combustion engine.

FIG. 5 is a front view of an axial end portion of a balance shaft drive device for an internal combustion engine according to an embodiment of the present invention.

6 is a cross-sectional view taken along line 6-6 of FIG.

7 is a sectional view taken along line 7-7 of FIG.

[Explanation of symbols]

 2 crankshaft 3 balance shaft 4 balance shaft 5 balancer gear 6 balancer gear 8 friction case 9 fins 10 oil passage 11 oil passage 12 relief valve 13 spring 14 seal 15 oil discharge passage 17 annular chamber 18 groove 19 protrusion 23 valve case 24 hole 25 valve Body 26 gap

Claims (1)

[Claims] 1. A gear-driven balance shaft rotatably driven from a crankshaft through a gear, an annular chamber extending around an outer periphery of a part of the balance shaft in the axial direction, and oil from an oil pump in the annular chamber. An oil passage to supply, a relief valve provided in the oil discharge passage from the annular chamber to the oil pan and opened at a predetermined hydraulic pressure or more, and a rotation restraining force to the balance shaft provided in the annular chamber when the relief valve is closed. And a rotation restraint force applying means for substantially eliminating the rotation restraint force when the relief valve is opened, and a balance shaft drive device for an internal combustion engine.