JPH10272376A - Roller mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a roller mill from being vibrated by self-excitation, by providing a dynamic vibration absorber, which shows high vibration proofing effects and is low in price, with respect to the roller mill. SOLUTION: This roller mill is equipped with a rotary table 3 with a groove part 2, a roller part having a crushing roller 4 and a bracket 5, and a pressing frame 6, which supports the roller part from above. In addition, a deformation element 14 which is elastic and has vibration energy absorbing properties and a weight supported by the deformation element 14 are provided on the bracket 5. Further, the natural frequency of a vibration system made up of the deformation element 14 and the weight 15 is tuned to the frequency of a self-excited vibration generated in the roller mill. In addition, the plural units 14, 15 of the vibration system are installed on the bracket 5 and the natural frequency of each of the units 14, 15 of the vibration system is tuned to the different frequencies, in the process of development, of the self-excited vibration of the roller mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulverizer for finely pulverizing agglomerates, which comprises a rotary table and a pulverizing roller which rotates according to the rotation of the table, and which is provided with a dynamic vibration absorber.

[0002]

2. Description of the Related Art As one type of pulverizer for finely pulverizing agglomerates such as coal, cement raw materials or new raw materials,
A vertical roller mill having a rotating rotary table and a plurality of crushing rollers is used, and has recently become one of representative models.

[0003] This type of crusher is a disk-shaped rotary table which is driven by a motor having a speed reducer at a lower portion in a cylindrical casing (housing) and rotates at a low speed in a horizontal plane, and has a circumferential surface on the upper surface thereof. A plurality of crushing rollers that are rotated by being pressed by a hydraulic rod are provided at positions equally divided in the direction. The crushing roller is supported by a bracket so as to be able to rotate according to the rotation of the rotary table, and a pressure frame provided on the upper side of the bracket allows a pendulum motion of the rotary table in a radial direction via a pivot. Supported by

Chute (supply pipe) to center of rotary table
The crushed material supplied from the rotary table draws a spiral trajectory on the rotary table due to the centrifugal force caused by the rotation of the rotary table and moves to the outer peripheral portion. Crushed in between and crushed. Hot air sent through the duct is guided to the base of the casing, and the hot air is blown upward from the air throat between the outer periphery of the rotary table and the inner wall of the casing toward the upper side of the mill. The powder produced by the pulverization is dried while rising in the casing by hot air blown from an air throat.

The granules transported to the upper part of the casing fall from the coarse material by gravity (primary classification), and the finer granules passing therethrough are re-emitted by a rotary classifier provided in the upper part of the casing. The fine powder having a predetermined particle size or less is conveyed by hot air, and is sent to a pulverized coal burner or a fine powder storage bin in a boiler, for example. A coarse flow larger than a predetermined particle size that has not passed through the classifier falls onto a rotary table and is pulverized again with the raw material just supplied into the mill. In this way, the crushing is repeated by the crushing roller in the mill.

[0006]

In recent years, coal-fired boilers have been required to operate in low-pollution combustion (low NOx and low unburned combustion) and in a wide range of load fluctuations. However, high grinding performance and minimum load reduction are also required.

The crushing roller of the roller mill crushes the powder and granules between the crushing groove of the rotary table and the crushing force by compressing and shearing. At the same time, the crushing roller applies its own weight and the load for the crushing. Supported by layers of the body. When the particle size of the granular material is improved, the supporting force of the granular material layer is weakened, and the thickness of the granular material layer between the rotary table and the grinding roller is reduced.

[0008] When the granular material layer has a certain thickness or less, self-excited vibration occurs. This self-excited vibration is a strong vibration in which the roller jumps in the vertical direction, and hinders stable operation of the roller mill.

As one means for reducing the vibration of the roller mill, a weight and a deformation element for supporting the vertical movement thereof are provided on the pressurizing frame, and the natural frequency of a vibration system composed of the deformation element and the weight is determined. Japanese Patent Application Laid-Open No. 5-31385 describes a method of reducing vibration by tuning to the frequency of generated vibration.

Since the frequency of the self-excited vibration of the roller mill is not constant and changes during the generation of the vibration,
The publication describes a method of detecting the frequency and changing the characteristics of the deformable element in accordance with the frequency.

However, such an active method is disadvantageous in terms of cost. Further, since the deforming element and the weight are provided above the pressing frame, the height of the entire roller mill must be increased. In addition, although it is preferable that the weight of the weight is lighter in terms of mechanism and cost, in order to suppress this by synchronizing with the large continuous self-excited vibration generated in the roller mill, a weight with a considerably large weight is required. is necessary.

An object of the present invention is to constitute a relatively light and inexpensive dynamic vibration absorber and prevent self-excited vibration of a roller mill.

[0013]

An object of the present invention is to provide a vibration system or a bracket in which a key-shaped weight is supported on a top surface and a back surface of a bracket by a deformation element in which a plurality of plate-like elastic bodies are stacked in a roller mill. One bracket has a plurality of vibration systems supported by a deforming element having a mechanism for amplifying or rotating the relative movement of the weight and the weight, and the natural frequency of each vibration system can be seen with a roller mill. 20% to 5 higher than the frequency of continuous self-excited vibration
The problem can be solved by setting 0% higher.

By tuning the natural frequency of the vibration system including the deforming element and the weight to the frequency of the self-excited vibration generated in the roller mill, the vibration is suppressed by the effect as a dynamic vibration absorber.

The frequency of the self-excited vibration of the roller mill changes in the course of its development, but the natural frequencies of a plurality of vibration systems are tuned to the frequency of the self-excited vibration in the course of its development. Before the self-excited vibration develops greatly by tuning to the frequency, the dynamic vibration absorber exerts its effect and suppresses the vibration. Thus, self-excited vibration can be prevented.

Further, a highly efficient structure using a deformable element in which a plurality of plate-like elastic bodies are stacked and a key-shaped weight is installed on a bracket, thereby increasing the height of the entire roller mill. Can be prevented.

Further, the weight of the weight can be reduced by using a vibration system supported by a deformation element having a mechanism for amplifying or rotating the relative movement between the bracket and the weight.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view showing the entire configuration of a roller mill according to an embodiment of the present invention as a partial cross section in a vertical cross section passing through the center axis of the mill.

In FIG. 1, this roller mill according to one embodiment of the present invention is driven by a motor (not shown) having a speed reducer in a housing 1 and rotates in a horizontal plane. A rotary table 3 having a crushing groove 2 in a shape, a crushing roller 4 arranged at a position dividing the circumference of the upper surface of the crushing groove 3 into three equal parts, a bracket 5 for fixing the crushing roller 4,
A triangular pressure frame 6, three weight rods 7, a chute 9 for supplying a raw material 8 and a rotary classifier 10 are provided above the mill.

The crushing roller 4 rotates in accordance with the rotation of the rotary table 3 with the shaft 11 fixed to the bracket 5 as a rotation axis. The bracket 5 is connected to the pressurizing frame 6 via a pivot 12 so as to have a degree of freedom of rotation about the pivot 12. The pivot 12 prevents the grinding roller 4 from pendulum moving in the radial direction of the rotary table 3. Accept.

The weight rod 7 transmits a crushing load 13 generated by hydraulic pressure to the pressure frame 6 and presses the crushing roller 4 against the rotary table 3. The bracket 5 has a deformation element 1
A weight 15 supported by the 4 and the deformation element 14 in the vertical direction is provided. The deformation element 14 and the weight 15 are accommodated in a case 16.

FIG. 2 is a view of the bracket 5 as viewed from the housing 1 side. In order to understand the state of the dynamic vibration absorber, the case 16 and the weight 15 on the left side are partially shown in cross section. A deformation element 14 in which a large number of plate-like elastic bodies 21 are stacked is provided on the back surface 22 and the upper surface 23 of the bracket 5, and the rear surface 2
2 and the weight 15 along the upper surface 23 are supported.

FIG. 3 is a view of the bracket 5 as viewed from the circumferential direction of the turntable 3, and the case 16 is omitted.
By forming the weight 15 in the key shape in this way, a downward surface is formed on both the upper portion 26 and the lower portion 25 of the weight, and the portion is connected to and supported by the bracket 5 via the deformable element 14 at that portion. Thus, the posture of the weight can be stabilized without any special guide. Also, the space utilization efficiency is good.

The plate-like elastic body 21 is bundled by a support 27 and the rear surface 22 or the upper surface 23 of the bracket 5.
Then, the plate-shaped elastic body 21 is fixed so that the surface thereof extends along the horizontal direction. The plate-like elastic body 21 can be deformed only in a direction perpendicular to its surface, and the weight 15 supported by the deforming element 14
Can move only in the vertical direction.

Further, as shown in FIG. 4, the deformation element 14 generates a frictional force F because the deformation thereof causes relative sliding in the longitudinal direction between the plate-shaped elastic bodies 21. Since the frictional force F acts to attenuate the energy of the vibration with respect to the vertical vibration of the weight 15 shown in FIG. 2, the deformation element 14 has the effect of the vibration damping together with the effect as the elastic body. Have.

If the frequency of the vibration generated in the roller mill matches the natural frequency of the vibration system composed of the deforming element 14 and the weight 15, the weight 15 vibrates greatly due to resonance, and the vibration of the deforming element 14 Due to the energy absorption characteristics, vibration of the main roller mill can be suppressed. This is widely known as a dynamic vibration absorber.

The vibration of the roller mill is a self-excited vibration that does not depend on an external excitation force. In a system that generates self-excited vibration, once the vibration grows, the vibration becomes large, but if sufficiently damped, no self-excited vibration is generated. Also in the roller mill having this configuration, if the amount of energy dissipated by the damping effect of the deforming element 14 and the weight 15 is set so as to exceed the amount of energy entering the system during self-excited vibration, the generation of self-excited vibration is prevented. It is possible to suppress.

The vibration damping effect of the dynamic vibration absorber is determined by the mass ratio between the main vibration system and the weight of the dynamic vibration absorber. The larger the weight of the weight, the greater the vibration damping effect. FIG. 5 shows the results of a simulation of the effect of suppressing vibration when the mass of the weight is changed. When the mass of the weight is sufficient (a), the self-excited vibration itself is completely suppressed, but when it is insufficient (b),
Although the magnitude of the vibration is somewhat smaller, the self-excited vibration is still occurring.

That is, when the dynamic vibration absorber is applied to the self-excited vibration of the roller mill, the effect of the mass ratio is not linear, but has a certain threshold. If the mass ratio is larger than that value, the self-excited vibration is completely eliminated. However, if the mass ratio is small, the effect of suppressing vibration is small. FIG. 6 schematically illustrates this.

When designing a dynamic vibration absorber, it is important to make its natural frequency coincide with the frequency of the main vibration system.
However, in the self-excited vibration of the roller mill, as shown in FIG. 7, the frequency changes in the course of the development of the vibration. At a stage where the amplitude of the vibration development is small at the initial stage, the frequency is relatively high, and as the vibration develops, the frequency decreases.

The frequency at the initial stage of vibration development is about 60% higher than the frequency of a sufficiently developed vibration. In addition, a large vibration means that a large amount of energy flows in, and a large damping effect is required to suppress such a large vibration, and a large mass is required for the weight of the dynamic vibration absorber. Becomes

That is, in order to produce a sufficient effect with a weight having a small mass, it is efficient to tune the natural frequency of the dynamic vibration absorber to a relatively high frequency in the development stage of the vibration of the roller mill. Further, by providing a plurality of dynamic absorbers per roller, for example, two, and adjusting each to a different frequency, the vibration damping effect can be exhibited in a wider range of the development stage of the vibration of the roller mill, and more effective. Vibration can be prevented.

That is, as shown in FIG. 8, the natural frequencies are set at f _A and f _B corresponding to the frequencies in the course of the development of the self-excited vibration, whereby the vibrations are generated during the development of the self-excited vibration. The self-excited vibration can be effectively suppressed by the weight having a small mass ratio by suppressing the vibration to develop into a large vibration.

As the natural frequencies f _A and f _B of the dynamic vibration absorber,
Considering that the frequency in the early stage of the vibration development is about 60% higher than the frequency of the sufficiently developed vibration and the width of the frequency at which the dynamic vibration absorber has an effect, the frequency of the developed self-excited vibration is 20%. It is preferable to tune to a frequency that is higher by 50% from 50% and that the natural frequencies of the respective dynamic vibration absorbers differ from each other by about 20%.

However, if the magnitude of the vibration reaches a level corresponding to the portion C, the effect of the dynamic vibration absorber can no longer be expected. However, in order to suppress such a large level of vibration, a weight having a larger mass is required, which is not efficient in terms of cost.

FIG. 9 is a diagram showing a bracket portion of an embodiment using a disc spring 31 as a deforming element as viewed from the housing 1 side. A plurality of disc springs 31 are combined and stacked, and are installed so as to sandwich the weight 32 from above and below, and are fixed by fasteners 33. The stacked disc springs 31 slip with each other when deformed by a vibration load, and attenuate the vibrations due to a loss of energy due to friction.

In the dynamic vibration absorber, the mass ratio described above is the ratio of the inertia of the main vibration system to the inertia of the weight. By increasing the apparent inertia of the weight, it is possible to reduce the actual mass of the weight. it can. For example, if the moving amount of the weight is increased with respect to the deformation of the deformation element, the apparent inertia of the weight is increased.

FIG. 10 shows an embodiment of a dynamic vibration absorber configured to increase the apparent inertia of the weight. The weight includes a support portion 42 supported by a coil spring 41 and a moving portion 43 that moves relative to the support portion 42. The support part 42 includes
A roller 44 is provided, and the roller 44 is sandwiched between a rail 45 provided on the main vibrator and the moving unit 43. Moving part 4
Numerals 3 are arranged so as to sandwich the rail 45 and the support portion 42 from both sides, and are fastened and fixed to each other by a bar 46.

When the support portion 42 moves due to the deformation of the coil spring 41, the roller 44 rolls, so that the relative motion between the support portion 42 and the moving portion 43 is the same as the relative motion between the support portion 42 and the rail 45. Therefore, the relative motion of the moving part 43 is twice as large as the deformation amount of the coil spring 41, so that the apparent inertia of the moving part 43 is doubled, and the apparent inertia of the entire weight is reduced. As a result, the mass of the weight can be reduced.

FIG. 11 shows this effect. Assuming that the mass of the supporting portion 42 is M, the mass of the moving portion 43 is m, the spring constant of the coil spring 41 is K, the displacement of the supporting portion 42 is u, and the displacement of the main vibrator is x, the displacement of the moving portion 43 is , 2 (ux) + x
= (2u-x). If the external force acting on the dynamic vibration absorber is f, the equation of motion is as shown in equation (1), and when deformed, it is as equation (2).

[0042]

(Equation 1)

[0043]

(Equation 2)

[0044]

(Equation 3)

[0045]

(Equation 4)

In general, when the dynamic vibration absorber is appropriately set and exerts its effect, the displacement of the weight is opposite in direction to the displacement of the main vibrator, and its magnitude is several times larger. Therefore, equation (3)
Then, Equation (4) is obtained. According to this, the apparent inertia is [M + (2 + α) m], which is larger than the actual mass (M + m) by (1 + α) m.

FIG. 12 shows an embodiment of a roller mill having the dynamic vibration absorber 47 having the above-described configuration. Two dynamic vibration absorbers 47 are installed on the back of the bracket 5, and the whole is covered with a case 48.

Also, the mass of the weight can be reduced by converting the translational motion of the weight into a rotational motion in response to the deformation of the deformable element. In other words, the actual mass is reduced by increasing the apparent inertia by using the rotational inertia of the weight.

FIG. 13 shows an embodiment thereof. The weight 51 includes a rotating weight 51, a ball screw 52, a bearing 53, and a coil spring 54. The translational motion due to the deformation of the coil spring 54 is converted into a rotational motion by the ball screw 52, and the weight 51 rotates while translating up and down. Do exercise. The coil spring 54 and the weight 51 are connected via a bearing 53.

FIG. 14 is a partial sectional view showing a main part of an embodiment of a roller mill having the dynamic vibration absorber 55. Two dynamic vibration absorbers 55 are installed on the upper surface of the bracket 5, and the whole is covered with a case 56.

It is also effective to supply seal air or the like to the above-described deformable element / weight system in order to prevent coal from being mixed and deposited.

[0052]

According to the present invention, an inexpensive dynamic vibration absorber having a high vibration damping effect can be provided for a roller mill, and self-excited vibration of the roller mill can be prevented.

[Brief description of the drawings]

FIG. 1 is a front view showing a partial cross section of the entire configuration of a roller mill according to an embodiment of the present invention.

FIG. 2 is a front view of a part of the bracket according to the embodiment of the present invention as viewed from a housing side.

FIG. 3 is an explanatory view of a bracket part according to an embodiment of the present invention as viewed from a lateral direction.

FIG. 4 is an explanatory diagram showing a behavior of a deformation element.

FIG. 5 is an explanatory diagram of a result of examination by simulation of the effect of the dynamic vibration absorber.

FIG. 6 is an explanatory diagram schematically showing a relationship between a mass ratio and a vibration suppression effect.

FIG. 7 is an explanatory diagram showing a state where the frequency changes during the development of the self-excited vibration of the roller mill.

FIG. 8 is an explanatory diagram of a natural frequency and a vibration isolation effect of the dynamic vibration absorber.

FIG. 9 is a front view of a main part of one embodiment of the present invention as viewed from a housing side.

FIG. 10 is a front view showing a main part of one embodiment of the present invention in a partial cross section.

FIG. 11 is an explanatory diagram showing an effect of the present invention.

FIG. 12 is a front view of a main part of a second embodiment of the present invention viewed from a housing side.

FIG. 13 is a front view of a main part of a third embodiment of the present invention viewed from a housing side.

FIG. 14 is a front view of a main part of a fourth embodiment of the present invention viewed from a housing side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Crushing groove 3 Rotary table 4 Crushing roller 5 Bracket 6 Pressure frame 7 Weight rod 8 Raw material 9 Chute 10 Rotary classifier 11 Shaft 12 Pivot 13 Crushing load 14 Deformation element 15 Weight 16 Case

Claims (5)

[Claims] 1. A rotary table having a groove on the circumference by rotating in a horizontal plane below a mill housing, a grinding roller arranged to face the groove, and a bracket rotatably supporting the grinding roller. A roller mill comprising: a plurality of roller units having: a pressurizing frame that supports the roller unit from above so as to allow the roller unit to move in the radial direction of the rotary table; A deforming element having energy absorption characteristics and a weight supported by the deforming element in a vertical motion are provided on the bracket, and a natural frequency of a vibration system including the deforming element and the weight is generated in the roller mill. A roller mill characterized by tuning to the frequency of self-excited vibration. 2. The roller mill according to claim 1, wherein the weight has a key shape, and the deformation element has a shape in which a plurality of plate-like elastic bodies are stacked, and the weight is formed via the deformation element. A roller mill, wherein the weight is supported on an upper surface and a rear surface of the bracket. 3. The roller mill according to claim 1, wherein a plurality of vibration systems including the deformation element and a weight supported by the deformation element are installed on the bracket, and the plurality of vibrations are provided. A roller mill wherein each natural frequency of the system is tuned to a different frequency during the development of self-excited vibration of the roller mill. 4. The roller mill according to claim 1, wherein a deformation element having a mechanism for amplifying a relative movement between the bracket and the weight is used. 5. The roller mill according to claim 1, wherein a deformable element having a mechanism for converting a relative motion between the bracket and the weight into a rotary motion is used.