JPH0526034B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an internal gear pump having two gears (an inner rotor and an outer rotor) with a difference in the number of teeth of one. [Prior Art] Conventionally, as this type of gear pump, a trochoid pump that utilizes trochoid tooth profiles as the tooth profile of an inner rotor and an outer rotor has been widely used. This trochoid pump brings various types of inner rotor into contact with various types of outer rotor, and by increasing or decreasing the space formed between each contact part, pressure oil is sucked from the suction port and discharged from the discharge port. It has the advantages of simple structure and high efficiency. [Problems to be Solved by the Invention] However, in the above-mentioned trochoid pump, oil is sucked in and discharged by changing the volume of all spaces, so while the pump efficiency is very high, the high speed rotation is At times, the negative pressure within the suction port becomes abnormally large, resulting in cavitation. Furthermore, since the oil pressure in each space changes as the volume of the space changes, cavitation also occurs within the space due to the instantaneous low pressure generated in the space on the suction port side. This cavitation causes problems such as abnormal noises and vibrations, damage to the pump, and a decrease in pump efficiency. Conversely, instantaneous high pressure is generated in the space on the discharge port side, and furthermore, as the volume of the space changes, so-called pulsation occurs and the discharge pressure fluctuates, which is coupled with the occurrence of cavitation. As a result, the noise and vibrations mentioned above become even more likely to occur. [Object of the Invention] The present invention was made in order to solve the above-mentioned problems, and an object thereof is to provide an internal gear pump that can significantly reduce noise generation. [Structure of the Invention] The internal gear pump of the present invention has a groove formed in the end face of at least one of the inner rotor and the outer rotor, extending in the circumferential direction and communicating with adjacent tooth grooves. It is something. [Function] In the internal gear pump having the above configuration, the spaces formed between the contact parts of the inner rotor and the outer rotor communicate with each other through the grooves, so that instantaneous low pressure may occur in either space. Alternatively, even if high pressure is generated, pressure oil is moved between spaces to relieve the pressure and prevent cavitation from occurring. Moreover, since pressure oil flows back from the discharge port to the suction port through the groove and each space, it is possible to prevent cavitation from occurring in the suction port and to alleviate pressure fluctuations in the discharge oil. Therefore, the pulsations and pressure fluctuations of the discharged oil can be suppressed to a low level, and the accompanying vibrations of the rotor and its surrounding parts can be reduced, and the generation of noise can be significantly reduced. [Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. The attached drawing shows an inner rotor and an outer rotor of a trochoid pump according to the present invention, and in this drawing, reference numeral 1 indicates the inner rotor. This inner rotor 1 has n teeth 1a and tooth grooves 1b (in this example, n=10), and has a casing (not shown) centered on the axis O _I.
It is rotatably installed. Moreover, the code|symbol 2 is an outer rotor. This outer rotor is n
It has +1 tooth 2a and tooth groove 2b, and is rotatably provided in the casing in a state eccentric by e with respect to the inner rotor 1. When the inner rotor 1 and the outer rotor 2 are rotated in the direction of the arrow A in the figure in the meshed state, each tooth 1 of the inner rotor 1 and the outer rotor 2 is rotated.
The volume of the space S formed between the contact parts a and 2a gradually decreases with rotation in the left part of the figure.
It gradually increases in the right part of the figure. Along with this,
Pressure oil is discharged from the space S on the left side to the discharge port A, and pressure oil is sucked into the space S on the right side from the suction port B. By the way, as mentioned above, in the trochoid pump having the above configuration, large noise is generated due to cavitation in the suction port B and the space S on the suction port side, as well as pulsation and pressure fluctuation in the discharge port A. Therefore, in the trochoid pump of this embodiment,
A groove 3 extending in the circumferential direction is formed in the tooth root side portion of the end surface of the outer rotor 2. Each end of this groove 3 is open to tooth grooves 2b, 2b existing on both sides of the groove 3, respectively. Therefore, the pressure oil existing in each space S can move to other spaces S through the grooves 3. In this case, increasing the cross-sectional area of the groove 3 will allow the pressure oil to move more freely and reduce cavitation, pressure oil pulsation, and pressure fluctuations, but there is a risk that the efficiency of the pump will decrease. There is. Therefore, the cross-sectional area of the groove 3 needs to be determined in consideration of reducing pulsation and pressure fluctuations and reducing pump efficiency. In this embodiment, the grooves 3 are formed on the end surface of the outer rotor 2, but they may be formed on the end surface of the inner rotor 1 or both. [Test Example] Next, the results of a noise test conducted to confirm the effects of this invention will be introduced. In this noise test, the oil pump according to the present invention and the conventional oil pump had the same specifications except that a groove (width 1.2 mm, depth 1.2 mm) was formed on the end face of the outer rotor according to the present invention. I have to. The common specifications are as follows. Inner rotor large diameter _I φ71.5 Inner rotor small diameter d _I φ58.5 Outer rotor large diameter D _O φ78.1 Outer rotor small diameter d _O φ65.1 Outer rotor trough radius of curvature R 5.982 Eccentricity 3.25 Number of inner rotor teeth 10 Outer rotor Number of teeth 11 Teeth Width 10 Theoretical discharge amount 10.33cc/rev The test results are shown in Attached Tables 1 and 2, respectively. Attached Table 1 shows the results of a noise test using a conventional oil pump, and Attached Table 2 shows the results of a noise test using an oil pump according to the present invention. As is clear from these tables, the oil pump according to the present invention was able to significantly reduce noise compared to the conventional oil pump. Moreover, the decrease in pump efficiency due to the formation of the groove is 800 to 1000 r.pm.
In the range of 1000rpm, it was less than 15%, and in the range exceeding 1000rpm, it was very low, less than 10%. In the above test, #30 mechanical hydraulic oil was used as the pressure oil, and the oil temperature was kept constant at 50°C. [Effects of the Invention] As described above, according to the internal gear pump of the present invention, teeth extending in the circumferential direction and adjacent to each other are provided on the end face of at least one of the inner rotor and the outer rotor. Since the grooves are formed to communicate with each other, the spaces formed between the contact parts of the inner rotor and the outer rotor are communicated by the grooves, so there is no chance of instantaneous low or high pressure in either space. Even if cavitation occurs, pressure oil is moved between spaces to alleviate the problem and prevent cavitation. Further, since the pressure oil flows back from the discharge port to the suction port through the groove and each space, cavitation in the suction port can be prevented, and pulsation and pressure fluctuations of the discharged oil can be alleviated. Therefore, generation of noise and vibration or damage to the pump can be prevented. Also, instead of grooves, it is possible to form sloped surfaces on the teeth such that the tooth width narrows from the root side to the tooth tip side, but if this is done, the inner rotor and outer rotor In addition, the area of the tooth surface that receives force (rotational force) becomes smaller, increasing the surface pressure. Wear occurs, which causes noise, but
In the internal gear pump of the present invention, the grooves are formed in at least one end face of the inner rotor and the outer rotor, so that the above-mentioned noise does not occur.

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【table】 [Brief explanation of drawings]

The attached drawing is a front view showing an embodiment of the present invention. 1... Inner rotor, 1a... Teeth, 1b...
Tooth groove, 2... Outer rotor, 2a... Teeth, 2b
... tooth groove, 3... groove, S... space.

Claims (1)

[Claims] 1. In an internal gear pump equipped with an inner rotor having a number of teeth of n (n≧2) and an outer rotor having a number of teeth of n+1, an end face of at least one of the inner rotor and the outer rotor. An internal gear pump characterized in that a groove is formed extending circumferentially around the entire circumference and constantly communicating between adjacent tooth grooves.