JP4493142B2 - Water pump - Google Patents

Description

【００１７】
この発明は、鳴き音の発生が、メカニカルシール部分を起振源とし、ポンプシャフトとそれに取付けられた駆動プーリ及びインペラによって共振系が構成されていることに鑑み、起振源側ではなく共振系を構成するＬ，Ｉ_im，ｎ，ε_s，ｄ，γ_d，ε₁の各要素を操作することで鳴き音の発生を防止するようにしたものである。
【００２１】
【発明の実施の形態】
次に、本発明の実施の形態を図面に基づいて説明する。
【００２２】
図１は、本発明にかかるウォータポンプの一実施形態を示すものであり、このウォータポンプは自動車のエンジンブロックに取り付けられ、冷却水をエンジン内部に送給するものである。尚、このウォータポンプの全体的な基本構成は従来の技術で説明した図７に示すものと同様であるため、この図７に示すものと同一機能部分については同一符号を付すものとする。
【００２３】
このウォータポンプの全体構成について簡単に説明すると、エンジンブロック（図示せず。）に結合されるハウジング１にはインペラ３が収容され、このインペラ３と外部の駆動プーリ５を連結するポンプシャフト４がハウジング１の側壁を貫通している。そして、ポンプシャフト４はプーリ取付部側が太軸部６、インペラ取付部側が細軸部７とされ、太軸部６が軸受８を介してハウジング１に回転自在に支持されると共に、細軸部７がハウジング１との間をメカニカルシール９によって液密に封止されている。
【００２４】
ウォータポンプにおける鳴き音の根本原因は、メカニカルシール９の摩擦トルクの速度特性における負の勾配であることが知られている（「メカニカルシールの鳴き現象とその防止に関する研究」〔１９９０年９月，九州大学博士学位論文，吉柳健二著〕の１０５頁等に記載。）が、この実施形態のウォータポンプは、液漏れ防止機能に影響するメカニカルシール９の摩擦特性については手を加えず、ポンプシャフト４を中心とする共振系を改善にすることによって鳴き音（スティック・スリップ自励振動。）の発生を抑えるようにしている。
【００２５】
本発明の発明者による研究によれば、ポンプシャフト４を中心とする共振系を構成する諸元のうちの以下に記載したＬ，Ｉ_im，ｎ，ε_s，ｄ，γ_d，ε₁の各値が鳴き音の発生に直接関与することが理論的に判明され、（１）式のＡの値が９×１０⁴ｋｇ^-0.5・ｍ^-2.5以下になれば鳴き音の問題が生じないことが実験的に確認された。
【００２６】
Ｌ：ポンプシャフト４の全長
Ｉ_im：インペラ３のイナーシャモーメント
ｎ：駆動プーリ５とインペラ３とのイナーシャモーメント比（プーリイナーシャＩ_pu／インペライナーシャＩ_im）
ε_s：ポンプシャフト４上のインペラ３側の端部からメカニカルシール取付部までの距離とポンプシャフト４の全長Ｌとの比（シール取付位置／全長Ｌ）
ｄ：ポンプシャフト４の太軸部６の直径
γ_d：ポンプシャフト４の細軸部７と太軸部６との直径比（細軸部直径／太軸部直径）
ε₁：ポンプシャフト４の太軸部６の長さと同シャフト４の全長Ｌとの比
【００２７】
【数２】

【００２８】
【数３】

【００２９】
このことからは、具体的には、ポンプシャフト４の全長Ｌを短く、インペラ３のイナーシャモーメントＩ_imを大きく、即ち、Ｌ／Ｉ_imを小さくすることが鳴き音の発生防止に有効であることが容易に想像できるが、ポンプシャフト４の全長Ｌは車両のエンジンルームの許容スペースから制約を受け、また、インペラ３のイナーシャモーメントＩ_imは車両から要求される吐出性能によって必然的に定まる値であるので設計的自由度はほとんど無い。これに対して（２）式のＢの値はウォータポンプの内部の寸法諸元によって構成されているので、メカニカルシール９の鳴き音を低減させるための最適設計が車両搭載上の制約を受けず可能である。
【００３０】
したがって、例えばポンプシャフト４のインペラ３側の端部からのメカニカルシール９の取付位置を図中左側に移動させてε_sの値を大きくし、ポンプシャフト４の太軸部６の直径ｄを大きく、ポンプシャフト４の直径比γ_dを１に近付け、イナーシャモーメント比ｎを小さくする等によって鳴き音の発生を防止することができる。つまり、この場合、メカニカルシール９の取付位置を図中左側に移動させる（ε_sの値を大きくする。）ことによって、起振源であるメカニカルシール９の取付部をポンプシャフト４を中心とする共振系の固有振動モードの節点に近付けることが可能になり、さらに、太軸部６の直径ｄを大きくし、直系比γ_dを１に近付けることによって共振系の共振周波数を高めることが可能になると共に、イナーシャモーメント比ｎを小さくすることによって、共振系の固有振動モードを、節点がメカニカルシール９の取付位置に近付くような形に変えることが可能になる。
【００３１】
因みに、（１），（２）式のＬ，Ｉ_im，ε₁の各値を調整することによってもＡの値を小さくすることができるが、ポンプシャフト４の全長Ｌを短くした場合には、共振周波数が高まり、インペラ３のイナーシャモーメントＩ_imを大きくした場合には、固有振動モードが変化する。また、太軸部６と全長Ｌの長さ比ε₁ を大きくした場合には、共振周波数と固有振動モードの両方が変化する。
【００３２】
ここで、図２はＡの値がほぼ１１×１０⁴（ｋｇ^-0.5・ｍ^-2.5）の従来タイプのウォータポンプの例（比較例）を示し、図３はＡの値がほぼ３×１０⁴（ｋｇ^-0.5・ｍ^-2.5）となるように設計した本発明にかかるウォータポンプの実施例を示すものである。
【００３３】
図３に示す実施例のものは、図２に示す比較例に対してメカニカルシール９の取付位置を図中左側に１０mm移動させることによってε_sの値をほぼ０．１から０．２に変更すると共に、太軸部６の直径ｄを１５．９mmから１７．５mmに増大させ、さらに、駆動プーリ５を小型にかつアルミ化することによってイナーシャモーメント比ｎを約５から２に変更した。
【００３４】
図４と図５は、この比較例と実施例のものに対して夫々近接音の測定を行ったときの時間軸波形を示すものであり、これらの図を比較して明かなように、実施例のものにおいては鳴き音が消滅している。
【００３５】
次に、前述の（１）式のＡの値を９×１０⁴ｋｇ^-0.5・ｍ^-2.5以下にすることで、鳴き音の発生が防止できる、との結論を得るべく行われた台上実験について説明する。
【００３６】
まず、発明者の行った台上実験におけるＯＫ・ＮＧの判定方法と、台上実験の結果とポンプの実使用環境下における鳴き音の関係について説明する。
【００３７】
鳴き音の根本原因は、メカニカルシール９の摩擦トルクの速度特性における負の勾配であることは前述した通りであるが、シールの摩擦特性は水温とポンプシャフト４の回転数に関係し、水温が高く、シャフト回転数が低い場合に負勾配が大きくなり、鳴き音が発生し易いことが知られている。このため、表１に結果を示した台上実験では、水温が高い場合から低い場合、シャフト回転数が低い場合から高い場合までをマトリクスに条件分けし、夫々の条件下で鳴き音発生の有無を確認した。そして、この実験では全条件での鳴き音の発生の有無を確認し、鳴き音の発生した条件の数を全条件数で割った値を「台上鳴き率」と称して、鳴き音に関してのＯＫ・ＮＧの判定の目安とした。表１の例では全４２条件のなかで７つの条件で鳴き音が発生しているので、台上鳴き率は７条件／全４２条件＝１７％となる。
【００３８】
また、実際のポンプ使用環境での鳴き現象については、既に繰り返し行った実験の経験から、台上鳴き率が２０％以下であれば全く問題にならないものと判断された。したがって、ここでは実験でのＯＫ・ＮＧの判定基準を台上鳴き率２０％とした。
【００３９】
【表１】

【００４０】
実際の実験においては、以上のような鳴き音のＯＫ・ＮＧ判定基準において、（１）式のＬ／Ｉ_imの値とＢの値を様々に変えたポンプに対して台上実験を行い、それぞれについてＯＫ・ＮＧの判定を行った。
【００４１】
以下の表２は、Ｌ／Ｉ_imの値の異なる４仕様のポンプに対して、シール取付位置と全長Ｌとの比ε_s，太軸部６の直径ｄ，イナーシャモーメント比ｎ等を変えることによってＢの値を種々に変化させ、夫々に対して台上実験を行ってＯＫ・ＮＧの判定を行った結果である。
【００４２】
【表２】

【００４３】
図６は、Ｂの値を縦軸に、（Ｌ／Ｉ_im）^0.5の値を横軸に夫々とり、種々のＡの値に対するＯＫ・ＮＧの判定結果を調べたものである。同図中には、表２で示した結果がプロットしてあり，そのうちの黒丸のプロットは台上鳴き率が２０％よりも大きいＮＧ判断を示し、白丸のプロットは台上鳴き率が２０％以下となるＯＫ判断を示す。このプロットを見て判るように、同図の左下側ではＡの値が小さく鳴き音が発生しにくく、逆に同図の右上側ではＡの値が大きく鳴き音が発生し易くなる。
【００４４】
図６中のプロットは一例であるが、実際にはさらに多くの条件で同様の台上実験を行い、その結果、鳴き音のＯＫ・ＮＧの境界値は９×１０⁴ｋｇ^-0.5・ｍ^-2.5（図６中の太線参照。）であり、鳴き音は、Ａの値が９×１０⁴ｋｇ^-0.5・ｍ^-2.5以下のときに確実に低減できるとの結論が得られた。
【００４５】
尚、本発明の実施形態は以上で説明したものに限るものでなく、例えば、（１）式のＡの値を小さくすべくメカニカルシール９の取付位置２０を駆動プーリ５側に移動させるときに、メカニカルシール９の摺動部材相互の接触面２１は一定位置にし、取付位置２０だけを駆動プーリ５側に移動させるようにしても良い。このようにした場合には、メカニカルシール９の実質的なシール位置は軸方向に移動しなくなり、ポンプ室２は軸受８側に必要外に膨出しなくなることから、ポンプ全体の小型・軽量化を図ることが可能になる。
【００４６】
また、Ａの値を９×１０⁴ｋｇ^-0.5・ｍ^-2.5以下に設定する場合に、インペラ３のイナーシャモーメントだけを大きくするようにすれば、インペラ３の交換のみによって対処することができる。とりわけ、このときインペラ３を鋳物にする等によって比重を増大させるようにすれば、既存のウォータポンプに対してほとんど寸法変更等の設計変更を行わずに鳴き音の発生を防止することができる。したがって、このようにした場合には、製造コストの高騰を最小限に抑えることが可能になる。
【００４７】
【発明の効果】
以上のように請求項１に記載の発明は、メカニカルシールを起振源とする自励振動の共振系を、鳴き音の発生を低減すべく適切に改善することができるため、メカニカルシールによる液漏れ防止機能の低下を招くことなく、鳴き音の発生を確実に防止することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す側面図。
【図２】比較例を示す側面図。
【図３】本発明の実施例を示す側面図。
【図４】比較例の鳴き近接音の時間軸波形を示す図。
【図５】本発明の実施例における鳴き近接音の時間軸波形を示す図。
【図６】台上実験の結果を示すグラフ。
【図７】従来の技術を示す断面図。
【図８】従来の技術を示すメカニカルシールの断面図。
【符号の説明】
１…ハウジング
２…ポンプ室
３…インペラ
４…ポンプシャフト
５…駆動プーリ
６…太軸部
７…細軸部
８…軸受
９…メカニカルシール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water pump used for cooling an automobile engine, and more particularly to a water pump that seals a housing and a pump shaft with a mechanical seal.
[0002]
[Prior art]
A water pump used for cooling an automobile engine usually has a structure as shown in FIG.
[0003]
The water pump shown in the figure will be briefly described. The housing 1 is coupled to an engine block (not shown) and a pump chamber 2 is formed between the housing 1 and the pump chamber 2 by rotation. The impeller 3 which acts is accommodated. The impeller 3 is integrated with a drive pulley 5 via a pump shaft 4 penetrating the housing 1, and when the pulley 5 is rotationally driven by engine power, the rotational force is transmitted via the pump shaft 4. It has become so. Further, a thick shaft portion 6 and a thin shaft portion 7 are connected between the pulley mounting portion and the impeller mounting portion of the pump shaft 4, and the thick shaft portion 6 is freely rotatable via the bearing 8 on the housing 1. While being supported, the thin shaft portion 7 is hermetically sealed with the housing 1 by a mechanical seal 9.
[0004]
And as the mechanical seal 9 used here, what is shown, for example in FIG. 8 is used.
[0005]
The mechanical seal 9 has a first sliding member 10 attached to the housing 1 and a second sliding member 11 attached to the thin shaft portion 7 of the pump shaft 4 so as to be axially displaceable. When the member 11 is urged in the axial direction by the spring 12, the end surfaces are always in contact with the first sliding member 10. Therefore, when the pump shaft 4 rotates with respect to the housing 2, the mechanical seal 9 rotates while the first sliding member 10 and the second sliding member 11 always maintain contact with each other, and the housing 1 and the pump This prevents liquid outflow from between the shafts 4.
[0006]
In this example, the second sliding member 11 is attached to the drive ring 13 coupled to the pump shaft 4 via the rubber bellows 14 so as to be axially displaceable, while the case 15 surrounding the rubber bellows 14 is attached. The provided front and rear projections 16 and 17 are engaged with the drive ring 13 and the grooves 18 and 19 of the second sliding member 11, respectively. Therefore, the second sliding member 11 can always rotate integrally with the pump shaft 4 regardless of the axial displacement of the member 11.
[0007]
However, when the mechanical seal 9 has such a structure, a so-called stick-slip self-excited vibration occurs due to frictional torque between the sliding members 10 and 11 and play in the circumferential direction of the protrusion 16 and the groove 18. However, it has been confirmed that it is easy to generate an unpleasant squealing noise. Conventionally, as disclosed in Japanese Utility Model Laid-Open No. 5-1075, this has been devised.
[0008]
The mechanical seal described in this publication is provided with a pressure contact portion that elastically contacts the bottom of the groove on the protrusion of the case that engages with the groove of the drive ring, and eliminates rattling between the case and the drive ring by this elastic contact. In this way, the generation of noise caused by stick-slip is suppressed.
[0009]
[Problems to be solved by the invention]
However, the occurrence of squealing using a mechanical seal as a vibration source is not only caused by the play of the support portion of the sliding member, but the current situation is that it cannot be sufficiently suppressed only by the above measures.
[0010]
The vibration at the mechanical seal part in the water pump is considered to be related to the frictional characteristics of the contact surface of the sliding member as the first, but the mechanical seal is originally intended to prevent liquid leakage from the pump chamber. Therefore, it is naturally impossible to design in consideration of only the improvement of the frictional characteristics of the sliding member. In other words, if the hydraulic fluid is positively guided to the contact surface by means such as reducing the pressing force between the sliding members, and so-called fluid lubrication is performed by this hydraulic fluid, the frictional resistance of the contact surface is reduced and the squealing occurs. Although the generation of noise can be reliably suppressed, the fact that the hydraulic fluid easily moves around the sliding surface means that the possibility of liquid leakage from the pump chamber is increased, and the mechanical seal structure It is difficult to achieve both the prevention of squealing and the prevention of liquid leakage only by simple improvement.
[0011]
Japanese Patent Application Laid-Open No. Hei 7-19349 discloses a technique for achieving both noise prevention and liquid leakage prevention by devising the material and surface shape of the sliding member constituting the mechanical seal.
[0012]
According to the technology described in this publication, one sliding member is made of carbon, the other sliding member is made of alumina ceramic, and appropriate voids and irregularities are formed on the sliding surface of the sliding member. The hydraulic fluid that contributes to the above can be held on the contact surface.
[0013]
However, even in this technique, the effect obtained is not sufficient, and if it is attempted to further prevent lubrication by further improving the lubricity, the problem of liquid leakage from the pump chamber is caused as before.
[0014]
Accordingly, the present invention is intended to provide a water pump that can reliably prevent generation of squeal noise by improving parts other than the mechanical seal, and can achieve both squeal noise prevention and liquid leakage prevention. .
[0015]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, the invention described in claim 1 is a housing that forms a pump chamber, an impeller that is housed in the pump chamber of the housing, and is disposed outside the housing, A drive pulley to which rotational power is input, a pump shaft connecting the drive pulley and the impeller, a thick shaft portion rotatably supported by the housing via a bearing, and a mechanical seal In a water pump in which a thin shaft portion that seals between the pump shaft and the impeller mounting portion side of the pump shaft is connected to the impeller mounting portion side, the overall length L of the pump shaft, the inertia moment I _{im of the} impeller, the drive Inertia moment ratio n between pulley and impeller, impeller on the pump shaft The ratio ε _s between the distance from the end on the side to the mechanical seal mounting portion and the total length L of the pump shaft, the diameter d of the thick shaft portion of the pump shaft, the diameter of the thin shaft portion and the thick shaft portion of the pump shaft Each value of the ratio γ _d and the ratio ε ₁ between the length of the thick shaft portion of the pump shaft and the total length L of the pump shaft is 9 × 10 ⁴ kg ^-0.5 · m ^-2.5 or less in the following formula It set so that it might become.
[0016]
[Expression 1]

[0017]
In view of the fact that the generation of squeal is caused by a mechanical seal portion as a vibration source and the resonance system is constituted by a pump shaft, a drive pulley and an impeller attached thereto, the resonance system is not at the vibration source side. Is generated by manipulating elements L, I _im , n, ε _s , d, γ _d , and ε ₁ .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 shows an embodiment of a water pump according to the present invention. This water pump is attached to an engine block of an automobile and supplies cooling water into the engine. Since the overall basic configuration of the water pump is the same as that shown in FIG. 7 described in the prior art, the same functional parts as those shown in FIG. 7 are denoted by the same reference numerals.
[0023]
Briefly describing the overall configuration of this water pump, an impeller 3 is accommodated in a housing 1 coupled to an engine block (not shown), and a pump shaft 4 for connecting the impeller 3 and an external drive pulley 5 is provided. The side wall of the housing 1 is penetrated. The pump shaft 4 has a thick shaft portion 6 on the pulley mounting portion side and a thin shaft portion 7 on the impeller mounting portion side, and the thick shaft portion 6 is rotatably supported by the housing 1 via a bearing 8, and the thin shaft portion 7 is hermetically sealed between the housing 1 and a mechanical seal 9.
[0024]
It is known that the root cause of the squealing noise in the water pump is a negative gradient in the speed characteristic of the friction torque of the mechanical seal 9 ("Study on mechanical squealing phenomenon and its prevention" [September 1990, Kyushu University Doctoral Dissertation, written by Kenji Yoshiyanagi], page 105, etc.)), but the water pump of this embodiment does not change the frictional characteristics of the mechanical seal 9 that affects the liquid leakage prevention function. thereby suppressing the occurrence of squeaking (Stick-slip self-excited vibration.) by the improved resonance system about the shaft 4.
[0025]
According to research by the inventors of the present invention, L described in the following of the specification that constitutes the resonance system around the pump shaft _{4, I im, n, ε} s, d, γ d, ε 1 of It is theoretically found that each value is directly related to the generation of squeal, and if the value of A in equation (1) becomes 9 × 10 ⁴ kg ^-0.5 · m ^-2.5 or less, the problem of squeal will not occur. It was confirmed experimentally.
[0026]
L: Total length of pump shaft 4 I _im : Inertia moment of impeller 3 n: Inertia moment ratio of drive pulley 5 and impeller 3 (pulley inertia I _pu / impeller liner I _im )
ε _s : ratio of the distance from the impeller 3 side end on the pump shaft 4 to the mechanical seal mounting portion and the total length L of the pump shaft 4 (seal mounting position / total length L)
d: diameter of the thick shaft portion 6 of the pump shaft 4 gamma _d: diameter ratio of the thin part 7 and the thick shaft portion 6 of the pump shaft 4 (thin shaft diameter / thickness shank diameter)
ε ₁ : ratio of the length of the thick shaft portion 6 of the pump shaft 4 to the total length L of the shaft 4
[Expression 2]

[0028]
[Equation 3]

[0029]
From this, specifically, it is effective to prevent the generation of squeaking noise by shortening the overall length L of the pump shaft 4 and increasing the inertia moment I _im of the impeller 3, that is, reducing L / I _im. However, the total length L of the pump shaft 4 is limited by the allowable space in the engine room of the vehicle, and the inertia moment I _im of the impeller 3 is a value inevitably determined by the discharge performance required from the vehicle. There is almost no design freedom. Since this respect (2) the value of expression of B is constituted by an internal dimension specifications of the water pump, the optimum design for reducing squeaking of the mechanical seal 9 is not restricted on-vehicle Is possible.
[0030]
Therefore, for example, the attachment position of the mechanical seal 9 from the end portion on the impeller 3 side of the pump shaft 4 is moved to the left side in the drawing to increase the value of ε _s and increase the diameter d of the thick shaft portion 6 of the pump shaft 4. By making the diameter ratio γ _d of the pump shaft 4 close to 1 and reducing the inertia moment ratio n, it is possible to prevent the generation of squeal. That is, in this case, by moving the mounting position of the mechanical seal 9 to the left side in the drawing (increasing the value of ε _s ), the mounting portion of the mechanical seal 9 that is the vibration source is centered on the pump shaft 4. It becomes possible to approach the node of the natural vibration mode of the resonance system, and further, it is possible to increase the resonance frequency of the resonance system by increasing the diameter d of the thick shaft portion 6 and bringing the direct ratio γ _d close to 1. At the same time, by reducing the inertia moment ratio n, the natural vibration mode of the resonance system can be changed so that the node approaches the attachment position of the mechanical seal 9.
[0031]
Incidentally, the value of A can be reduced by adjusting the values of L, I _im , and ε _{1 in} the expressions (1) and (2), but when the total length L of the pump shaft 4 is shortened, When the resonance frequency is increased and the inertia moment I _im of the impeller 3 is increased, the natural vibration mode changes. Further, when the length ratio ε ₁ between the thick shaft portion 6 and the total length L is increased, both the resonance frequency and the natural vibration mode change.
[0032]
Here, FIG. 2 shows an example (comparative example) of a conventional water pump having a value of A of approximately 11 × 10 ⁴ (kg ^−0.5 · m ^−2.5 ), and FIG. ⁴ shows an embodiment of a water pump according to the present invention designed to be ⁴ (kg ^−0.5 · m ^−2.5 ).
[0033]
In the embodiment shown in FIG. 3, the value of ε _s is changed from approximately 0.1 to 0.2 by moving the mounting position of the mechanical seal 9 10 mm to the left in the drawing relative to the comparative example shown in FIG. In addition, the diameter d of the thick shaft portion 6 was increased from 15.9 mm to 17.5 mm, and the inertia moment ratio n was changed from about 5 to 2 by making the drive pulley 5 smaller and aluminized.
[0034]
FIG. 4 and FIG. 5 show the time-axis waveforms when the proximity sound is measured for the comparative example and the example, respectively. As is clear by comparing these figures, FIG. In the example, the squeal disappears.
[0035]
Next, the table was made to conclude that the occurrence of squealing can be prevented by setting the value of A in the above equation (1) to 9 × 10 ⁴ kg ^-0.5 · m ^-2.5 or less. The experiment will be described.
[0036]
First, the OK / NG determination method in the bench experiment conducted by the inventor, and the relationship between the result of the bench experiment and the squealing sound under the actual use environment of the pump will be described.
[0037]
As described above, the root cause of the squeal is the negative gradient in the speed characteristic of the friction torque of the mechanical seal 9, but the friction characteristic of the seal is related to the water temperature and the rotational speed of the pump shaft 4, and the water temperature is It is known that when the shaft rotation speed is high and the shaft rotation speed is low, the negative gradient becomes large and a squealing noise is likely to occur. For this reason, in the bench test whose results are shown in Table 1, the water temperature is high to low, the shaft rotation speed is low to high, and the condition is divided into matrices, and whether or not squeal is generated under each condition. It was confirmed. And in this experiment, we confirmed the presence or absence of squeaking sound under all conditions, and the value obtained by dividing the number of squeaking sound conditions by the total number of conditions is called the “table squealing rate”. This was used as a guide for OK / NG determination. In the example of Table 1, since the squeaking sound is generated under 7 conditions among all 42 conditions, the tabletop squeal rate is 7 conditions / total 42 conditions = 17%.
[0038]
Further, regarding the squealing phenomenon in an actual pump usage environment, it has been determined from the experience of repeated experiments that if the squealing rate is 20% or less, there is no problem. Therefore, the OK / NG criterion in the experiment was set to 20% on the table.
[0039]
[Table 1]

[0040]
In the actual experiment, on the OK / NG criteria for the squeak as described above, a bench experiment was conducted for a pump in which the values of L / I _im and B in Equation (1) were changed variously. OK / NG determination was performed for each.
[0041]
Table 2 below changes the ratio ε _s between the seal mounting position and the total length L, the diameter d of the thick shaft portion 6, the inertia moment ratio n, etc., for the four specification pumps having different L / I _im values. This is a result of changing the value of B in various ways and performing a bench test for each to determine OK / NG.
[0042]
[Table 2]

[0043]
FIG. 6 shows the results of OK / NG determination for various values of A, with the value of B on the vertical axis and the value of (L / I _im ) ^{0.5 on} the horizontal axis. In the figure, the results shown in Table 2 are plotted. Among them, the black circle plot shows an NG judgment with a tabletop squeal rate larger than 20%, and the white circle plot shows a tabletop squeal rate of 20%. The following OK judgment is shown. As can be seen from this plot, the value of A is small on the lower left side of the figure, and it is difficult for squealing to occur. Conversely, the value of A is large on the upper right side of the figure, and squealing is likely to occur.
[0044]
Although the plot in FIG. 6 is an example, the same bench experiment actually more conditions, as a result, the boundary value of the OK · NG squeaking sounds ^{9 × 10 4 kg -0.5 · m} - ^{It was 2.5} (see the thick line in FIG. 6), and it was concluded that the squealing sound can be reliably reduced when the value of A is 9 × 10 ⁴ kg ^-0.5 · m ^-2.5 or less.
[0045]
The embodiment of the present invention is not limited to that described above. For example, when the mounting position 20 of the mechanical seal 9 is moved to the drive pulley 5 side in order to reduce the value of A in the equation (1). The contact surfaces 21 of the sliding members of the mechanical seal 9 may be set at a fixed position, and only the mounting position 20 may be moved to the drive pulley 5 side. In this case, the substantial seal position of the mechanical seal 9 does not move in the axial direction, and the pump chamber 2 does not bulge out to the bearing 8 side. It becomes possible to plan.
[0046]
Further, when the value of A is set to 9 × 10 ⁴ kg ^−0.5 · m ^−2.5 or less, if only the inertia moment of the impeller 3 is increased, it can be dealt with only by replacing the impeller 3. In particular, if the specific gravity is increased by, for example, casting the impeller 3 at this time, the generation of squealing can be prevented with little design change such as dimensional change with respect to the existing water pump. Therefore, in this case, it is possible to minimize the increase in manufacturing cost.
[0047]
【The invention's effect】
As described above, the invention according to claim 1 can appropriately improve the resonance system of self-excited vibration using the mechanical seal as a vibration source so as to reduce the generation of noise. Generation of squealing can be reliably prevented without causing a deterioration in the leakage prevention function .
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment of the present invention.
FIG. 2 is a side view showing a comparative example.
FIG. 3 is a side view showing an embodiment of the present invention.
FIG. 4 is a diagram showing a time axis waveform of a squeak proximity sound of a comparative example.
FIG. 5 is a diagram showing a time axis waveform of a squeak sound in an embodiment of the present invention.
FIG. 6 is a graph showing the results of a bench test.
FIG. 7 is a cross-sectional view showing a conventional technique.
FIG. 8 is a cross-sectional view of a mechanical seal showing a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Pump chamber 3 ... Impeller 4 ... Pump shaft 5 ... Drive pulley 6 ... Thick shaft part 7 ... Thin shaft part 8 ... Bearing 9 ... Mechanical seal

Claims (1)

A housing forming a pump chamber, an impeller accommodated in the pump chamber of the housing, a drive pulley disposed outside the housing and receiving rotational power from outside the pump, and connecting the drive pulley and the impeller A thick shaft portion that is rotatably supported by the housing via a bearing, and a thin shaft portion that seals between the housing by a mechanical seal from the pulley mounting portion side of the pump shaft. In the water pump that is connected to the impeller mounting part,
The total length L of the pump shaft, the inertia moment I _{im of} the impeller, the inertia moment ratio n of the drive pulley and the impeller, the distance from the impeller side end on the pump shaft to the mechanical seal mounting portion, and the pump shaft The ratio ε _s with the total length L, the diameter d of the thick shaft portion of the pump shaft, the diameter ratio γ _d between the thin shaft portion and the thick shaft portion of the pump shaft, the length of the thick shaft portion of the pump shaft and the shaft A water pump characterized in that each value of the ratio ε ₁ with respect to the total length L is set so that the value of A represented by the following formula is 9 × 10 ⁴ kg ^-0.5 · m ^-2.5 or less.

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