JPH06272673A - Internal tooth gear pump - Google Patents

Abstract

PURPOSE:To keep a tooth form theoretically free from abrasion, and ensure long-term stable operation, even when a small volume of liquid having a wide range of viscosity is forcibly fed under high prepare. CONSTITUTION:A rotatably supported driven external tooth gear 2 is made to have whole addendum tooth forms 2a, and the tooth forms 1a of an internal tooth drive gear 1 are kept in contact with the tooth forms 2a at projection points 6a only at one side for the reduction of torque acting on the gear 2 due to liquid pressure to zero, thereby keeping a tooth form theoretically free from abrasion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal gear pump, and more particularly to an internal gear pump in which rotational torque acting on a driven tooth profile is always zero.

[0002]

2. Description of the Related Art Gear pumps are used as relatively high pressure pumps because of their simple structure and small size. The gear pump includes an external gear pump, an internal gear pump, and an internal gear pump. The internal gear pump is composed of an outer rotor having a special tooth profile and an inner rotor that rotates with a number of contact points that is one less than the number of teeth of the outer rotor and rotates. The outer rotor rotates in the same direction by driving the rotor. Therefore, since the relative speed of the rotor is small, the noise is low and the pump can be made efficient. However, there is a problem that the tooth profile is special and it takes a long time to perform the gear cutting process, and the tooth surface is easily damaged due to the inclusion of foreign matter. On the other hand, since the tooth profile of the external gear pump or the internal gear pump is generally an involute gear,
It can be an inexpensive pump.

Further, when comparing the external gear pump and the internal gear pump, generally, in the external gear pump, the driven gear and the drive gear are composed of gears of the same shape, and therefore internal gears composed of different gears are used. The number of gear cutting steps is smaller than that of the gear pump, and the gear pump can be made more inexpensive. However, both the internal gear pump and the external gear pump have substantially the same theoretical discharge amount relationship to the number of teeth, but the external gear pump has a much larger discharge amount pulsation than the internal gear pump, Is also unsuitable for small gear pumps. Further, since the discharge amount pulsates, the discharge pressure also pulsates, and as a result, vibration increases and noise also increases.

In a gear pump, various losses are not taken into consideration,
The torque relationship is as follows in terms of energy in which the energy given to the liquid by the pump is equal to the power given to the drive shaft. The radiuses of the tip circles of the driving gear and the driven gear are R ₁ and R ₂ , the gear thicknesses are both b, and the radii from the shaft center to the tooth contact point C are R _C1 and R _C2 respectively for the driving gear and the driven gear, and the pressure. When the difference is P, the rotational torque T ₁ due to the hydraulic pressure resisting the rotation of the drive gear is

[0005]

[Equation 1]

Similarly, the rotational torque T ₂ due to the hydraulic pressure of the driven gear is

[0007]

[Equation 2]

[0008]

However, in the involute gear, the contact point C moves on the line of action, so that T ₁ and T ₂ acting on the gear are applied.
Fluctuates. T ₁ is used in the driving gear itself, and only the torque T _{2 of the} driven wheel acts as the tooth surface force. As described above, in the conventional internal gear pump having the involute coat tooth profile, the torque T ₂ due to the hydraulic pressure of the driven gear has a predetermined magnitude determined by the equation (2) and varies according to the rotation. The tooth profile wear at the contact point C was caused, and in particular, a low-viscosity liquid having low lubricity could not be used for a long time.

[0010]

[Purpose] The present invention has been made in view of the above circumstances, and can be used for liquids having a wide viscosity range from low-viscosity liquids to high-viscosity liquids, and is theoretical even when used under high rotation and high pressure. The object of the present invention is to provide a small-capacity and small-sized internal gear pump with no tooth profile wear.

[0011]

In order to achieve the above object, the present invention provides (1)
A driven gear that is rotatably supported by an external gear having a tooth profile that is a part of a pitch circle and is rotatably supported by an external gear, and a drive gear for an internal gear that has a tooth profile that contacts only at one projecting point of the driven gear, It has a sickle-shaped crescent disposed in a space formed by the driven gear and the drive gear and liquid-sealing between the addendums of the driven gear and the drive gear, and the rotational torque due to the hydraulic pressure of the driven gear is always zero. What has been done, further, (2) above (1)
In the above, the tooth profile of the tooth tip of the driven gear that comes into contact with the drive gear is an arc having a radius that can be ignored with respect to the tooth width of the driven gear. Hereinafter, description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining the principle of an internal gear pump according to the present invention, in which 1 is a drive gear, 2 is a driven gear, 3 is a driven gear shaft, 4 is a crescent,
Reference numeral 5 is a drive gear space, 6 is a contact point, 7 is a suction port, 8 is a discharge port, 9 is a contact surface, and 10 is a base.

In FIG. 1, the drive gear 1 is rotatably supported around an axis O ₁ by a sliding surface 9 fixed to a base 10, and is rotationally driven by a drive means (not shown) such as a motor. , An internal gear having a trochoidal tooth profile 1a, for example. Follower gear 2 is rotatably supported about the shaft O ₂ which is eccentric to the axis O ₁ of the drive wheel 1 in the driving gear 1, an outer gear having a tooth profile 2a of the addendum. That is, the tooth tip surface 2b of the driven gear 2 is equal to the pitch circle radius of R _C2, therefore, equal to the addendum circle radius R ₂ and a pitch circle radius R _C2.

The tooth profile 2a of all the deden dams of the driven gear 2 is
Although it has two projecting points 6a and 6b formed by the pitch circle and the tooth surface, since the drive gear 1 and the driven gear 2 come into contact with each other with backlash, the drive gear 1 and the driven gear 2 Are in contact with each other only at one projecting point 6a. Further, even in the tooth profile 2a different from the tooth profile 2a by one pitch, the tooth profile 2a is in contact with one projecting point 6a.

The crescent 4 includes a driving gear 1 and a driven gear 2.
Is a sickle-shaped plate-like member having a thickness equal to the tooth thickness of the drive gear 1 and the driven gear 2, and the concave surface 4a that contacts the blade is a driven gear. 2 tooth tip surface 2b
And the opposite convex surface 4b is a sliding surface with the tooth surface 1b of the drive gear 1. The crescent 4 is a known seal member that seals the low pressure side and the high pressure side of the drive gear space 5.

The suction port 7 is an inlet opening to the low pressure side of the drive gear space 5 to introduce the liquid on the low pressure side, and the discharge port 7 is opened to the high pressure side of the driven gear space 8 to be pressurized. It is an outlet for discharging high-pressure liquid.

Next, the operation of the internal gear pump constructed as described above will be described. Arrow R showing the drive gear 1 in solid line
Driven in the direction, the driven gear 4 rotates in the arrow r direction indicated by the same dotted line. At this time, the force due to the meshing of the teeth acts on the driven gear 4 in addition to the force due to the hydraulic pressure. The driving gear 1 has a torque T ₁ due to the hydraulic pressure acting on the driving gear 1 and a torque T ₂ due to the hydraulic pressure acting on the driven gear _2.
The torque of the sum of and acts.

The torque T ₁ acting on the drive gear 1 by the hydraulic pressure P is from the tooth thickness b, the tooth tip radius R ₁ , the shaft O ₁ to the contact point projection 6a, as in the above equation (1). Average radius R
_C1

[0019]

[Equation 3]

Is the torque T ₂ acting on the driven gear _2.
Is the radius R _C2 between the tip radius R ₂ of the driven gear ₂ and the center O ₂ to the projecting point 6a, which is the contact point, as in the equation (2),

[0021]

[Equation 4]

Is satisfied. However, the tooth profile 2 of the driven gear 2
a is an all-Addendum tooth profile, the tip radius R ₂ is constant, the radius R _C2 is also constant, and R ₂ = R _C2 (3). Therefore, T ₂ = 0 (4) and only the torque T ₁ due to the hydraulic pressure of the drive gear 1 acts on the drive gear 1. However, since T ₁ is consumed by the drive gear itself by the motor or the like, the tooth surface force applied to the tooth surface is T ₂ = 0.

This is because the tooth tip of the driven gear 2 is formed as a part of the pitch circle radius R _2C , and the hydraulic pressures acting on both sides of the tooth profile are equal, so that the pressure is always balanced and the tooth profile 2a
Means that the force due to hydraulic pressure does not act on.

FIG. 2 is a view showing an example of the shape of the protruding points of the driven gear of the internal gear pump according to the present invention. In the drawing, 9 is a contact surface, which is the driven gear 2 which is the external gear shown in FIG. Point 6a
Is a contact surface of an arc surface having a radius that is negligibly smaller than the width of the tooth tip. Since the projecting point 6a is the contact surface 6 of the circular arc having the small radius, the rotational torque of the driven gear 2 is not zero, but it is small and can be ignored, and the projecting point 6a does not contact at an acute angle. The shape of the contact surface 9 is stable for a long time. According to an experiment by the applicant, no change in tooth profile was observed even when a low-viscosity liquid of 1 cP or less was continuously operated at a high pressure for several tens of hours.

[0025]

As is apparent from the above description, according to the present invention, the hydraulic pressure acting on the driven gear is balanced, and the torque due to the hydraulic pressure is zero or substantially zero, so there is theoretically no wear of the tooth profile. It is possible to provide a pump capable of stably pumping a liquid having a wide viscosity range from a low-viscosity liquid to a high-viscosity liquid under a high-speed rotation and high pressure for a long period of time.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining the principle of an internal gear pump according to the present invention.

FIG. 2 is a diagram showing an example of a projected point shape of a driven gear of the internal gear pump according to the present invention.

[Explanation of symbols]

1 ... Drive gear, 2 ... Drive gear, 3 ... Drive gear shaft, 4 ... Crescent, 5 ... Drive gear space, 6 ... Contact point, 7 ... Suction port, 8 ... Discharge port, 9 ... Contact surface.

Claims (2)

[Claims] 1. A driven gear, which is rotatably supported by an external gear having an all-Dedendum tooth profile whose tooth tip is a part of a pitch circle, and an internal gear having a tooth profile which is in contact with only one projecting point of the driven gear. A drive gear and a sickle-shaped crescent disposed in a space formed by the driven gear and the drive gear and having a liquid seal between tooth tips of the driven gear and the drive gear, and rotation of the driven gear by hydraulic pressure. An internal gear pump characterized in that the torque is always zero. 2. A tooth profile of a tip of a tooth tip of the driven gear that comes into contact with the drive gear is an arc having a radius that can be ignored with respect to a tooth width of the driven gear. The internal gear pump according to 1.