JPS603401A - Apex seal for rotary piston engine - Google Patents

Abstract

PURPOSE:To prevent leakage of compressed gas from a combustion chamber, which could lead to pressure loss of the combustion chamber, by providing an apex seal comprising a base portion made of sintered Fe-alloy with relatively low rigidity, and a sliding portion made of cast iron alloy having a chilled-cast-iron structure. CONSTITUTION:A rotary engine 1 comprises a casing 4 defined jointly by a rotor housing 2 having a trochoidal inner surface 2a and a side housing 3 having an inner surface of a gas soft-nitrided layer, and a planetary rotation rotor 5 supported on an eccentric shaft 6. Each of apexes of the rotor 5 has a seal groove 7 in which received are an apex seal 8 comprising a base portion 15 of sintered Fe-alloy and a sliding portion 16 of cast iron alloy having a chiled-cast-iron structure, a side piece 9, and a leaf spring 10 underlying the apex seal 8. With this arrangement, the apex seal 8 is able to follow the contour of the trochoidal inner surface 2a consistently as moved with the rotor 5 for thereby keeping the apex seal 8 free from incomplete local contact thereof with the trochoidal surface 2a, wherein the property of wear resistance of the sliding portion 16 due to the chilled-cast-iron structure ensures an effective gas seal to prevent gas leakage which could lead to pressure loss of the compressed gas in a combustion chamber of the rotary engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apex seal for a rotary piston engine.

(Prior Art) It has been conventional practice to form the apex seal of a rotary piston engine from alloyed cast iron, and to chill the sliding portion that comes into sliding contact with the trochoid surface of the rotor bearing. Such an apex seal made of partially chilled cast iron reduces metal contact between the chromium plating applied to the trochoid surface and the sliding part, preventing sintering and improving wear resistance. Since the seal as a whole has high rigidity (longitudinal elastic modulus of 7330θ to about 9/-), it cannot bend and deform following the shape of the trochoidal surface, and there is a problem that local contact occurs and welding occurs.

In contrast, as disclosed in Japanese Patent Application Laid-open No. 60-70♂0♂, the apex seal is formed of a sintered alloy, and the rigidity of the apex seal is reduced to improve its ability to follow the uneven shape of the trochoidal surface. The idea of improving things is well known. However, since such a sintered alloy has pores in the sliding portion, the trochoid surface is likely to be scratched, resulting in poor sealing performance. In addition, there has been a proposal to form a cermet (titanium carbide) film on the sliding part of the sintered metal apex seal, but since the cermet itself is too hard, there is no way to solve the above scratch problem. This has not yet been achieved.

The problem of welding or scratching on apex seals made of partially chilled cast iron or sintered metal is particularly noticeable in engines that require high rotation and high output, resulting in deterioration of sealing performance and the resulting damage to the engine. It is desired to improve the apex seal in order to prevent a drop in compression pressure.

(Object of the Invention) In view of the above, the present invention has the advantages of a partially chilled cast iron apex seal that the sliding part itself has good wear resistance, and an apex seal made of sintered alloy that has good followability to the trochoidal surface. The present invention provides an apex seal for a rotary piston engine that has the advantages of an apex seal, and solves the problem of reduction in engine output due to welding and scratches.

(Structure of the Invention) The present invention comprises a casing composed of a rotor housing and side housings disposed on both sides of the rotor housing, and a seal groove is provided at the top of the rotor that rotates planetarily within the casing. This relates to an apex seal for a rotary piston engine in which the apex seal is inserted into a seal groove.

The apex nord is comprised of a base and a sliding part that is joined to the base and slides against the trochoidal surface of the rotor housing. The base has a density of 6.5~l, 6f'/
cA, longitudinal elastic modulus 7.500~/, 3000Kq/
- It is composed of iron-based sintered alloy. The sliding part is made of alloyed cast iron with a chill structure.

The density and modulus of longitudinal elasticity of the base of the apex seal have a correlation between them, and as the density increases, the modulus of longitudinal elasticity also increases. However, the density is 6.6
Below f/crd, the longitudinal elastic modulus is 760θKq/
If it is less than -, the strength of the apex seal is low and there is a problem that it may break. On the other hand, the density is 1. ．． 3 f /
When cnl is exceeded, the longitudinal elastic modulus exceeds /〃00Kq/-, and the rigidity becomes as high as that of the conventional alloy cast iron apex seal, and it is not effective in preventing compression pressure drop.Therefore, The base of the apex seal changes its density to j6~l, j?/cttl.

It is preferable that the longitudinal elastic modulus is 750θ to /30θθKg/mA.

Even if the density is in the range of 55 to 3 Fl/crA, depending on the material of the iron-based sintered alloy, the modulus of longitudinal elasticity may fall outside the numerical range described above. Needless to say, this method is unsuitable in terms of compression pressure drop. Conversely, the longitudinal elastic modulus or 7j00
Even if the density is in the range of ~/30θθKy/-, the density is 1. ．．
5? / When crA is exceeded, the weight of the apex seal becomes thicker (as a result, the surface pressure of the apex seal acting on the trochoid surface increases, which has a negative effect on the trochoid surface and also increases the load applied to the sliding part of the apex seal. In addition, if the density is less than 3.61 (9/crd), there will be a problem of decreased strength, which is undesirable.

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

In the rotary piston engine 1 shown in FIG.
is a rotor housing whose inner peripheral surface is a trochoidal surface 2a, and as shown in FIG.
The rotor housing 2 and the casing 4 are composed of a side housing filter having a gas nitrocarburizing layer disposed on both sides of the rotor housing 2 on its surface. Inside the casing 4, a substantially triangular rotor 5 is supported by an eccentric shaft B and rotates planetarily in the direction of arrow A.

At each top of the rotor 5 there is a '1' shown also in FIGS.
A seal groove 7 is formed as shown in FIG.
An apex seal 8 and a side piece 9 are fitted into the. There is a gap between the bottom of the seal groove 7 and the seal 8 and side piece 9.

A ring 10 is interposed and urges the apex seal 8 against the trochoid surface 2a of the rotor housing 2. The trochoid surface is porous chrome plated.

In addition, as shown in FIG.
are provided respectively, and the rotor 50 is provided with a side seal 14.
is installed.

The specific structure of the apex seal 8 is shown in FIGS. 7 and 5.

That is, the apex seal 8 is made by joining a base part 15 made of a ferrous sintered alloy and a sliding part 16 made of alloyed cast iron having a chilled structure. It is designed to come in sliding contact with the To explain an example of the dimensions, in the figure, the height h is = 5':
6 rtan, the length ℃ is ♂θ, the width W is 3 mm, the height hl of the sliding part B is 2.0-2.6 mm, and the protrusion amount h2 of the protrusion 17 downward at the end is 10 votes, 2wn for the radius of the sliding part 16.

Next, the Apex seal according to the example of the present invention will be explained based on a comparative test with a comparative example.

The structure and physical properties of each of the apex seals of Examples and Comparative Examples are shown in Table 1.

In this table, A and I in the apex seal structure column
) is the symbol of the material constituting the apex seal, the contents of which are shown in Table 2. Similarly, the symbol 10 means the connection between the base and the sliding part.

! ) Table 2 The manufacturing method of the Apex seal of each Example and each Comparative Example is as follows.

<Example/and 3~B, Comparative example/and! 〉Made of iron-based sintered alloy (C or D), length 2j, height 2m,
Width! ;While molding the base material for the base, mold the sliding part material with a length of 25 mm, height of 3 mm, and width of 6 mm using alloy cast iron (A or B), and then mold the sliding part material on the base material. Then, they are temporarily joined together in a hydrogen gas atmosphere at a temperature of /y, 20° C., and a time of 28 minutes. The material for the sliding part of this bonded product is heated and rapidly cooled with an electron beam to chill it, and the bonded part is fused to form an apex seal having the dimensions and shape shown in FIGS. 7 and 5.

<Example! 〉 A base material and a sliding part having the same dimensions and shapes as in the above example were molded from iron-based sintered alloy C (density, 3.0 sy/cni) and alloyed cast iron A, and then slid onto the base material. A moving part material is placed, and the sliding part material is chilled with an electron beam, and is bonded to a base material and processed into an apex seal having the dimensions and shape shown in FIGS. Thereafter, the pores of the sintered alloy constituting the base were sealed by impregnation treatment with water glass (50% by weight aqueous sodium silicate solution), and the temperature was ♂0°C.
Dry for 7 hours. The reason why such a pore sealing treatment is performed is that in the case of a low-density sintered alloy, there is a concern that gas leakage may occur due to the pores, leading to knee + notation defects. Incidentally, the weight increase due to the processing agent remaining in the apex seal due to this sealing treatment is about 00// in terms of weight ratio, and no particular problem occurs.

Comparative Examples 3 to j> A part of the cast iron alloy (A or B) (the part corresponding to the sliding part) was heated and rapidly cooled with an electron beam to obtain a chilled structure. It is processed into an apex seal having the dimensions and shape shown in FIG. 1, and for comparative example G, it is processed into a bottom-up apex seal with the height of the portion corresponding to height h adjusted to zz.

The measurement method for the load/deflection column in Table 1 is shown in FIG. That is, Apex seal sample material 1
8 and 3; fulcrum member 19.19 with an interval of Ommm below.
A load P was applied to the apex seal sample 18 from above at the center between both fulcrum members 19 and 19, and the relationship between the load and the amount of deflection of the apex seal sample 18 was investigated.

Moreover, the weight ratio in Table 1 is / for Comparative Example 3.

Test method> The rotary piston engine used in the test has a working chamber volume of 7.3 I! , with a turbocharger, and the maximum output is /OQPS.

-Measurement of Compression Pressure Decrease Rate- A cycle in which the engine speed is increased from 7000 rpm to 700θrpm under full load operation with the accelerator fully open, and then the accelerator is immediately released and the engine speed is lowered to 6θ0rpm (it takes 7 minutes and the water temperature is also forcibly increased. After performing 3 cycles of 3 cycles, the compression pressure is measured and compared with the compression pressure in the engine before the test to determine the rate of decrease.

The measurement results are shown in the column of compression pressure reduction rate in Table 3.

1) Measurement of height wear of apex seal - After the above test, the engine is disassembled and the amount of wear of the apex seal is measured. The measurement results are shown in the height wear column of Table 3.

-Evaluation of vertical scratches on the trochoid surface- The condition of the vertical scratches on the trochoid surface of the rotor housing of the disassembled engine is judged by the touch with fingertips and toes, and the state of wear of the porous chromium plating on the trochoid surface is examined. The evaluation criteria are shown in Table 7, and the evaluation on a 70-point scale is shown in the vertical scratch evaluation column of Table 3.

- Judgment of test status - Inspect the welding status of the trochoid surface and apex seal from the disassembled engine rotor/ushing described above, and check for breakage of the apex seal. The results are shown in the status column of Table 3.

Table 3 Table 〈Consideration of test results〉 In the case of the examples, the wear amount of the apex seal is θ
02.5 or less, and the vertical scratch evaluation was 7 points or higher, and the compression pressure reduction rate did not significantly exceed 7% (there were no particular problems with the vertical scratches on the trochoid surface.

Of course, no breakage or welding of the apex seal was observed in the examples. It is recognized that this test result is related to the fact that the value of (load/deflection) was less than 3θθKy/rrvn, and the apex seal's followability to the trochoid surface was good. Furthermore, as in Examples j, F, and J, the density of the iron-based sintered alloy constituting the base is reduced to reduce the longitudinal elastic modulus to 7jθ0Kq/
- In the case where the apex seal was kept to a moderate level, there was almost no wear on the apex seal, the vertical scratch evaluation was 2 points, and the compression pressure reduction rate also showed a negative value, indicating that the apex seal and trochoid surface fit well. The results showed very good results.

On the other hand, products such as Comparative Example / in which the density and modulus of longitudinal elasticity of the iron-based sintered alloy constituting the base are increased, and products made of partially chilled alloy cast iron such as Comparative Examples 3 and j, The measured value of (load/deflection) is 9/r at 30θ
The apex seal has a large amount of wear, and there is welding around the ignition plug 1 lobe a on the training side, and the vertical scratch rating is 5 points or less, indicating a decrease in compression pressure. is also getting bigger. Also, a comparative example! In the case where the base was made of an iron-based sintered alloy having a low density (6,21 i'/cA) and a small modulus of longitudinal elasticity (2/00 Ks+/-), the apex seal broke during the test.

The value of (load/deflection) of this comparative example is quite low at 73/0.3 Ky/hear.

Therefore, the above example! Alternatively, from a comparison of the test results of G, B and Comparative Example 2, it is preferable that the density of the iron-based sintered alloy constituting the base of the apex seal is J: 6 f / ad or more, the longitudinal elastic modulus is 7600 Ky/- or more, and It turns out that it is preferable for the hardness to be 70 or higher on the HRB scale.
The (load/deflection) value of the apex seal is also 770Kq.
It can be seen that there is no problem if the value is around /na.

In addition, from the comparison of the test results of Examples/3 and 6 and Comparative Examples, the above density is less than or equal to Jfl/crd,
The longitudinal elastic modulus is /300 (17Kg/- or less, hardness HRB
is preferably r0 or less, and even considering Comparative Examples 3 and j, the value of (load/deflection) is 7/++ for 3θθ.
It can be seen that ++++ or less is preferable.

Comparative example G lowers the height h of the apex seal to lower its rigidity, and makes the value of (load/deflection) similar to Examples No. and G, etc., and Table 3 shows that it is relatively good. The test results show that because the height of the apex seal is low, the amount of unburned gas that passes through the bottom of the seal increases, causing gas leakage, which is undesirable because it causes poor emissions.

In addition, in manufacturing the apex seal, in the above example, a sliding part material made of alloyed cast iron was placed on a base material made of ferrous sintered metal and heated and rapidly cooled with an electron beam. In this case, the height of the sliding part material is preferably about 2.6 to j 6 tan. In other words, the height of the sliding part material is i, less than 6 m (
In the experiment, two pharynxes were used. ), the entire sliding part material is chilled, but the chill layer becomes very thin, less than /j standard, and on the other hand, the above height is higher than 3.5 mm (in the experiment, it was set as 3.5 mm). In this case, a portion of the sliding portion that is not chilled remains and the rigidity becomes high, which is not preferable.

(Effects of the Invention) As described above, the base of the apex seal is made of a relatively low-rigid iron-based sintered alloy, and the sliding part is made of alloyed cast iron having a chill structure. During the operation of a rotary piston engine, the apex seal closely follows the unevenness of the trochoid surface to prevent local contact, and is compatible with the wear resistance of chilled cast iron. As a result, a decrease in compression pressure can be prevented without causing gas leakage.

[Brief explanation of drawings]

1 to 5 illustrate embodiments of the present invention, FIG. 1 is a longitudinal sectional view of a rotary piston engine, and FIG. 2 is a longitudinal sectional view of a rotary piston engine.
An enlarged sectional view taken along the nm line in the figure, Figure 3 is m in Figure 2.
7 is a front view showing the apex seal partially omitted, FIG. 5 is a side view of the apex seal, and FIG. 3 is a front view showing the aspect of the load-deflection test.

Claims (1)

[Claims] (/l A seal groove is provided at the top of the rotor that rotates planetarily in a casing constituted by a rotor housing joint and side housings arranged on both sides of the rotor housing, and an apex seal is installed in the seal groove. In a rotary piston engine that is fitted in a rotary piston engine, the base of the apex seal has a density of 56 to 56?/cr&,
It is made of an iron-based sintered alloy with a longitudinal elastic modulus of 7soo~/JθθθKf/-, and the sliding part of the apex seal, which is joined to this base and slides on the trochoidal surface of the rotor housing, is made of alloyed cast iron with a chill structure. An apex seal for a low-resolution piston engine.