CN101285415B - Diaphragm piston type thermostat valve actuator - Google Patents

Abstract

The invention provides a valve driving device of a diaphragm piston type thermostat, comprising a cylinder, a piston and a piston rod, the piston is in fit with an inner cavity of the cylinder, the piston rod is connected with the piston, the head part of the piston rod is pulled through an upper end of the cylinder and extends out directly, a piston stroke limit check ring is arranged at a lower end of the cylinder, vents are arranged on the upper end of the cylinder and on the piston; a temperature sensing cylinder inner cavity is filled with liquid with the boiling point between fifty centi degrees and seventy centi degrees, an opening of the temperature sensing cylinder is provided with an expansion diaphragm and the surrounding of which is air sealed with the temperature sensing cylinder; the temperature sensing cylinder is arranged at the lower end of the cylinder and is connects with the cylinder to form a whole unit. The valve driving device acts on the expansion diaphragm, the piston and the piston rod by the pressure produced in liquid vaporization to push the valve to be switched on/off certain range of temperatures, which is simple in structure, stable in performance, long in service life and can replace the prior valve driving mechanism.

Description

Diaphragm piston type thermostat valve actuator

Technical field

The present invention relates to a kind of piston pneumatic type thermostat, the valve actuator that especially utilizes air pressure to promote.

Background technique

Cooling system is the important component part of motor, and thermostat plays crucial effects again in cooling system.What extensively adopt in the engine-cooling system at present is waxtype thermostat, presses the functional part branch and is made up of valve driving mechanism, valve mechanism, carriage.This thermostat is made up of support, main valve, push rod, paraffin, sebific duct, auxiliary-valve, thermostat shell, spring etc.As temperature sensing medium, utilize the melted paraffin wax volumetric expansion with paraffin, force sebific duct to shrink, thereby promote push rod, valve is opened gradually.Also have ether formula thermostat, it is to charge into ether in folding cylinder, utilizes ether to form vacuum when liquefaction, and the principle of volumetric expansion during vaporization produces folding cylinder and shrinks or elongation, reaches the purpose that control valve opens and closes.

Because the absolute expansion amount of paraffin thermal expansion can not produce enough displacements, promote valve and realize switch motion.Therefore, waxtype thermostat is actually and utilizes hydraulic principle, the push rod of the extruding force promotion minor diameter that expands by the liquid paraffin in the major diameter chamber, and promptly the big piston mode that pushes away small piston increases the push rod stroke, causes the structure relative complex.In addition, also will consider the sealing problem of liquid paraffin, its manufacture difficulty, precision and manufacture cost are higher relatively.Ether formula thermostat expands with variation of temperature constantly because of folding cylinder or shrinks, and causes mechanical fatigue easily, causes folding damage.

Summary of the invention

The objective of the invention is to that a kind of temperature sensing medium is cheap, simple in structure in order to provide, stable performance, long diaphragm piston type thermostat valve actuator of life-span, substitute existing valve driving mechanism.Constitute a thermostat by valve driving mechanism, valve mechanism, carriage.

Inventive concept: the present invention utilizes vaporizing liquid to produce pressure and acts on inflatable membrane, piston and piston rod by the suitable liquid of a kind of boiling point, promotes valve and realize switch motion in certain temperature range.

For this reason, technological scheme of the present invention is: diaphragm piston type thermostat valve actuator, comprise cylinder barrel, piston, piston rod, piston cooperates with the inner chamber of cylinder barrel, piston rod is connected with piston, the head of piston rod passes the cylinder barrel upper end and directly stretches out, and it is characterized in that: the lower end of cylinder barrel is provided with the spacing back-up ring of piston stroke, all is provided with vent on the upper end of cylinder barrel, the piston; A temperature-sensitive barrel cavity is equipped with the liquid of boiling point between 50 ℃～70 ℃, and the opening of temperature-sensitive bucket is provided with inflatable membrane, inflatable membrane periphery and the hermetic seal of temperature-sensitive bucket; Described temperature-sensitive bucket places the lower end of cylinder barrel, and links into an integrated entity with cylinder barrel.

Working procedure: this diaphragm piston type thermostat valve actuator applies in the thermostat, be contained in valve mechanism and constitute thermostat on the carriage, at normal temperatures or when the temperature of motor is lower than 85 ℃, vaporization phenomenon does not take place in the liquid in the temperature-sensitive bucket under the precompression effect of return spring.Along with the temperature of the cooling liquid in the engine water jacket constantly raises, when coolant temperature was higher than uniform temperature, the liquid in the temperature-sensitive bucket began vaporization, and the pressure of inflatable membrane below is raise, the promotion inflatable membrane moves upward, thereby promotion piston and piston rod move upward.The impacting force that piston rod promotion valve overcomes return spring moves upward together, with valve open.After valve is opened fully, piston motion is to the top of cylinder barrel, when the temperature of the liquid in the temperature-sensitive bucket continues to raise, the pressure of inflatable membrane below will increase, the boiling point of the liquid in the temperature-sensitive bucket increases thereupon, thereby make temperature and its boiling point of the liquid in the temperature-sensitive bucket form a kind of state of equilibrium, the liquid in the temperature-sensitive bucket stops vaporization, and thermostat is in a kind of more stable state of equilibrium.When engine water temperature is lower than uniform temperature, the liquid in the temperature-sensitive bucket will liquefy, and the pressure of inflatable membrane below reduces, and the aperture of valve reduces thereupon, until throttle down.

Beneficial effect: this valve actuator adopts the liquid cheap, that boiling point is suitable, utilize the relation of fluid pressure and boiling point, make liquid produce driving force at suitable temperature vaporized expanding, and adopt simple piston cylinder operator transmission of drive force, act on valve mechanism, the purpose that reaches valve opening or close.A kind of so innovative device has advantage simple in structure, good reliability, applies to the automobile thermostat, can increase a kind of not only practical but also can bring the novel product of good economic benefit.

Description of drawings

Fig. 1 is the plan view of diaphragm piston type thermostat valve actuator.

Fig. 2 is the inflatable membrane structural front view.

Fig. 3 is an inflatable membrane structure plan view.

Fig. 4 is the saturation vapour pressure of acetone and the experimental curve diagram of boiling point.

Fig. 5 carries out the rectilinear that fitting a straight line obtains with the MatLab simulation software.

Among Fig. 1, the 1st, inflatable membrane, the 2nd, liquid, the 3rd, temperature-sensitive bucket, the 4th, the spacing back-up ring of piston stroke, the 5th, piston, the 6th, piston rod, the 7th, cylinder barrel.

Embodiment

Diaphragm piston type thermostat valve actuator as shown in Figure 1, comprise temperature-sensitive bucket 3, inflatable membrane 1, spacing back-up ring 4, cylinder barrel 7, piston 5, piston rod 7, piston 5 cooperates with the inner chamber of cylinder barrel 7, piston rod 7 is connected with piston 5, the head of piston rod passes the cylinder barrel upper end and directly stretches out, the spacing back-up ring 4 of piston stroke is located at the lower end of cylinder barrel, all is provided with vent on the upper end of cylinder barrel 7, the piston 5; Temperature-sensitive bucket 3 inner chambers are equipped with the liquid 2 of boiling point between 50 ℃～70 ℃, and the opening of temperature-sensitive bucket is provided with inflatable membrane 1, inflatable membrane 1 periphery and 3 hermetic seals of temperature-sensitive bucket; Described temperature-sensitive bucket 3 places the lower end of cylinder barrel, and links into an integrated entity with cylinder barrel 7.

Liquid 2 in the temperature-sensitive bucket is the liquid of boiling point between 50 ℃～70 ℃, makes that thermostatic valve is can open between 85 ℃～90 ℃ the time at engine water temperature.

Shown in Fig. 2,3 inflatable membrane, the surface 3 of inflatable membrane is scraggly curved surface, this is in order to reduce the amount of deformation of inflatable membrane when expanding, to reduce the tensile stress that inflatable membrane work is, allaying tiredness destroys, and improves working life.

During use, diaphragm piston type thermostat valve actuator and valve mechanism directly are connected on the carriage, and piston rod 7 acts on the valve.

The selection of liquid and the design of return spring and calculating

Liquid can be selected boiling point pure organic chemistry liquid between 50 ℃～70 ℃, we have chosen acetone (boiling point is 56.48 ℃) by experiment thus, and by correction to the acetone laboratory data, return spring is designed, thereby obtain the design parameter of return spring that whole thermostat is played an important role.

The diameter of choosing piston in the experiment is 20mm, and spring rate is 1.3N/m, and the precompressed amount of spring is 15mm.The laboratory data such as the table 1 of the temperature and pressure relation of acetone:

Table 1 acetone temperature and pressure concern laboratory data

The acetone temperature (℃)	Piston displacement (mm)	Spring pressure (N)
			40	0	19.5
42	0	19.5

44	0	19.5
			46	0	19.5
48	0	19.5
			50	0	19.5
52	0	19.5
			54	0	19.5
56	0	19.5
			58	0	19.5
60	0	19.5
			62	1.3	21.2
64	1.5	21.5
			66	1.8	21.8
68	2.8	23.1
			70	3.8	24.4
72	4.5	25.4
			74	5.8	27.0
76	7.3	28.9

78	8.8	30.9
			80	10.3	32.9
82	12	35.1
			84	14.3	38.1
86	16.5	40.9
			88	19.3	44.6
90	21.5	47.5
			92	24.5	51.4
94	27.5	55.3

Press the designing requirement of thermostat, when 85 ℃～90 ℃ valves were opened fully, aperture should be 7mm.From laboratory data as can be seen, piston about 6mm that in this temperature range, risen, the acetone boiling point is 56.48 ℃, can be used as the preferably selection of temperature sensing liquid.

Because experimentation has error to exist, and need revise laboratory data, makeover process is as follows:

According to the relation of the saturation vapour pressure and the boiling point of liquid, i.e. Clausius-Clapeyron equation:

$\frac{d\ln p}{\mathrm{dT}}=\frac{{\mathrm{\&Delta;}}_{\mathrm{vap}}{H}_{m_{\mathrm{<figure-callout\; id="2"\; label="m\; RT"\; filenames="S2008100478164E00011.png"\; state="\{\{state\}\}">m</figure-callout>}}}}{{\mathrm{RT}}^{}}$

R is a molar gas constant, and T is a thermodynamic temperature, Δ _VapH _mBe the molar heat of vaporization of neat liquid under a certain temperature, temperature range hour, Δ _VapH _mCan be similar to as constant, integration gets:

$\ln p=-\frac{{\mathrm{\&Delta;}}_{\mathrm{vap}}{H}_m}{R}\frac{1}{T}+C$

Right with lnp

Mapping should be straight line, because the boiling point of acetone is 56.48 ℃, before reaching boiling point, piston should not have displacement, so can study since 56 ℃ according to theoretical.Data are made its curve by experiment, as Fig. 4.

After carrying out fitting a straight line with MatLab, the straight line that obtains such as Fig. 5.

According to the resulting linear equation of Fig. 5 be:

$y=\left\{\begin{array}{cc}-2.2458x+17.8120,& 2.86\&le;x\&le;3.04\\ -4.3456x+23.8740,& 2.78\&le;x\&le;2.86\\ -5.07x+25.9459,& 2.86\&le;x\&le;2.88\\ -5.0677x+25.8783,& 2.70\&le;x\&le;2.78\end{array}\right.$

Can revise and error analysis data by the linear equation after the match, make form such as table 2 (wherein Δ is an absolute error, | Δ |/F is a relative error, and δ is a standard deviation).

The error analysis of table 2 straight line model fitting function

As can be seen from Table 2, the maximum value of absolute error Δ is 1.0, relative error | Δ | and the maximum value of/F is 5%, standard deviation $\mathrm{\&delta;}=\sqrt{\frac{1}{22}\underset{i=1}{\overset{22}{\mathrm{\&Sigma;}}}{\left({\mathrm{\&delta;}}_i\right)}^2}=0.55,$ Satisfy the design accuracy requirement.

Because the valve fitness for purpose of thermostat is opened between 85 ℃～90 ℃, so need calculate the pairing force value of each temperature spots in this temperature range, i.e. work loads during return spring work is so that carry out the design of spring.Aperture 7mm with valve calculates, and can calculate each temperature spots corresponding spring amount of deformation, and is as shown in table 3, thereby can draw the rigidity of spring.

Table 3 temperature and spring deflection corresponding relation

t(℃)

Work loads F i(N)

Amount of deformation f i(mm)

85	39.4	31.27
			86	41.5	32.94

87	42.2	33.49
			88	43.6	34.60
89	45.3	35.95
			90	48.2	38.25

The rigidity of spring is: (48.2-39.4)/(38.25-31.27)=1.26N/mm, know that by table 3 pre compressed magnitude of spring is 31.27mm, can carry out the design of spring thus.

In sum, select acetone for use, the relation according to its boiling point and surface pressure designs return spring, can satisfy design and practical requirement.

Claims (3)

1. diaphragm piston type thermostat valve actuator, comprise cylinder barrel, piston, piston rod, piston cooperates with the inner chamber of cylinder barrel, piston rod is connected with piston, the head of piston rod passes the cylinder barrel upper end and directly stretches out, it is characterized in that: the lower end of cylinder barrel is provided with the spacing back-up ring of piston stroke, all is provided with vent on the upper end of cylinder barrel, the piston; A temperature-sensitive barrel cavity is equipped with the liquid of boiling point between 50 ℃～70 ℃, and the opening of temperature-sensitive bucket is provided with inflatable membrane, inflatable membrane periphery and the hermetic seal of temperature-sensitive bucket; Described temperature-sensitive bucket places the lower end of cylinder barrel, and links into an integrated entity with cylinder barrel.

2. diaphragm piston type thermostat valve actuator according to claim 1 is characterized in that: the surface of described inflatable membrane is scraggly curved surface.

3. diaphragm piston type thermostat valve actuator according to claim 1 and 2 is characterized in that: the liquid of described temperature barrel cavity dress is acetone.

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