RU2043550C1 - Four-link pivot crank mechanism - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: length of connecting rod 3 and rocker 4 is 9 times lesser than the length of crank 2. The distance between the axes of connections of crank 2 and rocker 4 with stand 1 is 6 times lesser than the length of crank 2. EFFECT: improved design. 2 dwg

Description

 The invention relates to mechanical engineering and can be used in internal combustion engines and pneumatic devices with uneven movement of the working bodies, in mechanisms for transmitting forces to rotational movement, mainly in muscular drives.

 Known four-link articulated crank mechanism containing a rack and placed on it a crank, connecting rod and beam.

 A disadvantage of the known mechanism is the low efficiency (efficiency) of the transfer of forces to rotational motion due to the failure of the mechanism with certain parameters.

 The technical result of the invention is to increase the efficiency.

 This is achieved by the fact that the four-link articulated crank mechanism is made with a connecting rod and rocker length less than 9.0 crank lengths and the distance between the axes of the connection of the crank and rocker arm to the rack is less than 6.0 crank lengths.

F·r·cosφ n¹= 1, 2, 3; где M_i сумма моментов на оси;
F сила действующая вдоль шатуна;
r длина кривошипа;
φ угол давления;
Механизм содержит стойку 1, кривошип 2, шатун 3 и коромысло 4. Поставленная задача, повышения КПД (эффективности) решается определением зависимостей величин моментов на оси А от длин звеньев четырехзвенного шарнирного кривошипно-коромыслового механизма, стойки 1, кривошипа 2, шатуна 3, коромысла 4. Принимается угол Ψ независимый параметр, φ- функция. Задача сводится φ(Ψ) функция положения. По теореме косинусов из Δ АВД иΔ ДВС после преобразований определяем φ₁ и φ₂
φ₁ arccos a; φ₂= arccos K где a

K

после введения безразмерных относительных величин δ

P

λ

возможны два случая
1. φ₁+φ₂=

+ φ Δ
2. φ₁+φ₂=

φ Δ
Δ arccos

a·k-

Для упрощения анализа моментов принимается F 1, r 1,
тогда M

sinΔ(Ψ)dΨ
При условии l

R или λ

р обеспечивается равномерное перемещение точек В и С в соответствующих прямом и обратном направлениях, а также достигается максимальный результат по моменту, где
Δ arccos

1-δcosΨ-δsinΨ

Расчетами получены величины суммарных моментов в зависимости от параметров (относительных величин звеньев) четырехзвенников). Данные расчетов приведены на графике (фиг.2) зависимостей М ( λ,P,δ) при условии

p в области существования, проворачиваемого кривошипа. Расчеты единичных моментов произведены с точностью до четвертого знака. Предельные значения углов положения Ψ₁ и Ψ₂ определены, как
Ψ₁= arccos m;
Ψ₂ arccos n; где m

n

для каждого значения параметров. Для сравнения приведен единичный момент кривошипного, кривошипно-ползунного, известного шарнирного кривошипно-коромыслового четырехзвенного механизма и др. который равен 114,588. Момент вышеназванных механизмов не зависит от величин звеньев и равен константе при действии силы, равной единице, и кривошипе, равном единице. Значение М 114,588 получено с достаточной степенью точности для практического примечания. В доступной литературе (по механике, физике и др.) не приходилось встречать вышеназванную постоянную. Константа 114,588 имеет размерность произведения длины на силу и характеризует вращательный эффект силы при силе, равной единице, и (плече) кривошипе, равном единице, для механизмов, содержащих кривошип.The increase in efficiency (efficiency) of the four-link articulated crank mechanism when transferring forces F to rotational motion is characterized by a moment M on the crank axis λ and is determined by the pressure angle φ in FIG. 1. By means of the pressure angles, the sum of the moments of forces on the axis A is determined;
M _i =

F r cos cos n ¹ = 1, 2, 3; where M _{i is the} sum of the moments on the axis;
F force acting along the connecting rod;
r crank length;
φ pressure angle;
The mechanism contains a rack 1, a crank 2, a connecting rod 3 and a rocker 4. The task, increasing the efficiency (efficiency) is solved by determining the dependence of the values of the moments on the axis A on the lengths of the links of the four-link articulated crank-beam mechanism, rack 1, crank 2, connecting rod 3, rocker arm 4. Accepted angle параметр independent parameter, φ-function. The problem is reduced to the φ (Ψ) position function. By the cosine theorem from Δ AED and Δ ICE after transformations, we determine φ ₁ and φ ₂
φ ₁ arccos a; φ ₂ = arccos K where a

K

after the introduction of dimensionless relative quantities δ

P

λ

two cases are possible
1. φ ₁ + φ ₂ =

+ φ Δ
2. φ ₁ + φ ₂ =

φ Δ
Δ arccos

a · k-

To simplify the analysis of moments adopted F 1, r 1,
then M

sinΔ (Ψ) dΨ
Provided l

R or λ

p provides uniform movement of points B and C in the corresponding forward and reverse directions, and also achieved the maximum result in time, where
Δ arccos

1-δcosΨ-δsinΨ

The calculations obtained the values of the total moments depending on the parameters (relative values of the links) four-link). The calculation data are shown in the graph (figure 2) of the dependencies M (λ, P, δ) under the condition

p in the area of existence of the crank cranked. Calculations of single moments are made to the fourth digit. The limit values of the position angles Ψ ₁ and Ψ _{2 are} defined as
Ψ ₁ = arccos m;
Ψ ₂ arccos n; where m

n

for each parameter value. For comparison, a single moment of a crank, crank-slide, known articulated crank-link four-link mechanism, etc. is given, which is 114.588. The moment of the above mechanisms does not depend on the magnitude of the links and is equal to a constant under the action of a force equal to one, and a crank equal to one. The value M 114.588 was obtained with a sufficient degree of accuracy for a practical note. In the available literature (in mechanics, physics, etc.), one did not have to meet the aforementioned constant. The constant 114.588 has the dimension of the product of the length and the force and characterizes the rotational effect of the force with a force equal to one and a (shoulder) crank equal to one for mechanisms containing the crank.

 In FIG. 1 is a kinematic diagram of a four link articulated crank mechanism.

It contains a rack 1, placed on it a crank 2, a connecting rod 3 and a rocker 4 in three positions. In the initial position Cl Ψ ₁ , in an arbitrary position C ₁ Ψ, and in the final position C ₂ , Ψ ₂ .

 Figure 2 shows the values of the total unit moments depending on the parameters of the four-link articulated crank-link mechanisms. The curve δ = 1.0 is the largest in the total moment. The curve δ 6.0 is the smallest in the total moment, i.e. it closely adjoins the horizontal line M (λ, p, δ) 114.588, which displays the total unit moment of the known mechanism (crank, crank-slide and known four-link, etc.).

The mechanism works as follows. Under the action of the force F (Fig. 1), the points C ₁ and B _{1 of the} mechanism move to the position C2 and B2 counterclockwise. Accordingly, when the crank is moved from the initial position Ψ ₁ to the final position Ψ ₂ , a working stroke or maximum transfer of force F takes place to form the total moment on the axis A of the crank with certain parameters of the mechanism. Then, from the position Ψ ₂ to the position Ψ _{1 of the} crank, a reverse stroke occurs, also counterclockwise, the force F does not act, i.e. point C2 of the mechanism returns to its original position. Then this cycle repeats.

Claims (1)

 The four-link articulated crank-and-beam mechanism contains a rack, cranks, a connecting rod and a beam, located in it, characterized in that the length of the connecting rod and the beam is less than 9 crank lengths, and the distance between the axes of the connection of the crank and the beam to the rack is less than 6 crank lengths.

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