GB2032585A - A hydraulic transmission device - Google Patents

Abstract

A hydraulic transmission device using hydraulic oil for transmitting the torque output of an engine. The cross- sectional area of the hydraulic oil circulating passageway is made substantially constant throughout the passageway by arranging the thickness distribution (2c', 2c'') of the blade (2c) provided on the rotating members to meet the variation of the cross-sectional area (S) along the circulating passageway. <IMAGE>

Description

SPECIFICATION A hydraulic transmission device The present invention relates to a hydraulic transmission device, such as a hydraulic torque converter or a hydrodynamic coupling comprising a number of relatively rotatable members having blades or vanes and being able to transmit power by passing hydraulic oil between the blades of respective rotatable members and circulating said hydraulic oil through respective members in succession.

A conventional hydraulic transmission device will be explained in general by taking as a typical example a torque converter by referring to Fig. 1.

In this figure, 1 designates a pump impeller, 2 a turbine runner, 3 a stator or reaction member. The torque converter having the rotatable members with the center of rotation at line o is driven by an engine through its crankshaft (not shown), coupled with a converter cover 4, which is in turn coupled to the pump impeller 1. During such driving motion, the pump impeller 1 ejects the hydraulic oil in a direction of an arrow a through ring shaped passageways bounded by its outer shells 1 a and cores 1 b. The ejected hydraulic oil passes through other ring shaped passageways bounded by outer shells 2a and cores 2b of the turbine runner 2 as indicated by an arrow b and then passes through further ring shaped passageways bounded by outer shells 3a and cores 3b of the stator 3 as indicated by an arrow c and returns back to the pump impeller 1.The circulation of the hydraulic oil is caused by blades 1 c, 2c and 3c of the respective rotatable elements 1, 2 and 3. The stator 3 is coupled with an output axis (not shown) of the torque converter rotating with the turbine runner 2 via a uni-directional clutch 5. Accordingly, the hydraulic oil drives the turbine runner 2 as torque conversion during the circulation under reaction of the stator 3. The torque converted engine output power may be taken out through the torque converter output axis.

In the practical design of such a hydraulic transmission device, it is desired to minimize the flow loss of the hydraulic oil and to obtain a high efficiency. In order to realize such an object, an optimum cross-sectional area of the hydraulic oil circulating passageway is calculated and the cross-sectional area of the passageway should be made the same as far as possible in the whole length thereof.

In general, in the example of a torque converter, a passageway factor a, which is expressed by S/r2, wherein S is a cross-sectional area of the hydraulic oil passageway and r is a radius of rotation as shown in Fig. 2, is selected to be 0.7 to 0.9 and the cross-sectional area S is decided. In practice, as shown in Fig. 3, the shapes of cores 1 b, 2b and 3b are so selected as to satisfy a condition that a cross-sectional area S = 27rr x B (B is width of the passageway) of the passageway will assume said optimum value at any point on the circulating passageway of the hydraulic oil.

Namely, the shapes of the cores are so decided that the core becomes more spaced from the respective outer shell or to enlarge the width of the passageway at a smaller radius of rotation r.

It has been the usual practice that the determination of the above factors is made without taking into account the thickness of the blades and number thereof. Accordingly, the calculated cross-sectional area of the hydraulic oil circulating passageway in the conventional device is decreased by the thickness of blades in practice.

Furthermore the rate of decrease in the cross sectional area is larger at a position nearer to the center of rotation o of the rotatable members since the width of the passageway is larger as has been explained above. It also becomes larger according to an increase of the number of blades.

More detail of this decrease in the cross sectional area will be explained by referring to Fig.

4 which shows a partial section of the passageway provided for the turbine runner 2. In Fig. 4, Si shows a cross-sectional area at the input of the passageway and So shows a cross sectional area at the output of the same. These areas are expressed by the following equations as mentioned above.

Si = li x Bi So = lo x Bo Then we assume to arrange blades 2c in this passageway of a thickness T and of a number which is n. In this case, the cross-sectional area decreases at the input by T x Bi x n and at the output by T x Bo x n both by the thickness of the blades. Since a relation exists that Bo > Bi, it becomes T x Bo x n > T x Bi x n. Accordingly, the cross-sectional area of the passageway at the output side decreases more by T x n(Bo - Bi) than that of the input side by the provision of the blades 2c. It is also understood that this difference becomes larger according to an increase in the number n of the blades.

Fig. 5a shows an example in which a straight blade 2c extending in the direction of flow of the hydraulic oil shown by the arrow is used. However, it is very seldom such staight blades are used extending in the direction of the flow. Usually, the blade is of curved shape in the direction of flow of the hydraulic oil as shown for example in Figs. 5b to 5e. Again we may consider the passageway of the hydraulic oil formed between two adjacent blades. The effective cross-sectional area at each position corresponds to a value of diameter of an internal tangential circle of respective position (only those at input and output of the hydraulic oil passageway are shown by dash-dot line) multiplied by the width of the passageway (such as width Bi or Bo at the input or output shown in Fig. 4a).As can be seen from Figs. 5a to 5c, the passageway formed between two adjacent blades has progressively decreased in cross-sectional area towards the output of the hydraulic oil and increased curvature of the blades 2c. Also in other types as shown in Fig. 5d or 5e, contrary to the above embodiment, the cross-sectional area decreases towards the input of the passageway (Fig. 5d), or it decreases towards both ends of the passageway (Fig. 5e).

As shown in the foregoing examples, if the cross-sectionai area of the passageway of the hydraulic oil is decreased on the way, the flow thereof of is restricted or impeded there and the flow is not smooth. This causes a lowering of the torque ratio of the hydraulic transmission device, a lowering of the space factor, deterioration of the efficiency, etc. so that a substantial lowering of the characteristics results.

In order to solve this problem, it has been considered to alter the shape of the core so that the hydraulic oil circulating passageway of the hydraulic transmission device becomes uniform when the blades are mounted. It was also considered to decrease the number of blades so that the cross-sectional area of the hydraulic oil passageway becomes a desired value at the narrowest portion of the passageway as the base.

However, by the former proposal, the width of the passageway should become larger so that the flow of the hydraulic oil is altered substantially and the aforementioned passageway factor a may become outside the ideal range of 0.7-0.9. As a result, usually the problem cannot be solved even when the cross-sectional area of the passageway is uniform and the characteristics of the hydraulic transmission device is worse than before. Further by the latter proposal, the decrease in the number of blades causes slipping of the hydraulic oil at the output of the blades. This merely worsens further the characteristics of the hydraulic transmission device and the problem never has been solved.

In view of the foregoing problems, the present invention has for its object to solve the disadvantages of the conventional hydraulic transmission devices. According to the present invention, the basic design of the hydraulic transmission device relating to the passageway of the hydraulic oil, number of blades and etc. is not faltered at all but the distribution of thickness of the blades, which has relatively high freedom of alteration, is modified along the passageway of the hydraulic oil so that the cross-sectional area of the passageway is made uniform throughout the - full length thereof and 9 hydraulic transmission device solving the aforementioned problems and definitely improving the characteristics of the device is realized.

For a better understanding of the invention, reference is made to the accompanying drawings, in which: Fig. 1 is a side view in vertical cross-section for showing a torque converter as an embodiment of the hydraulic transmission device; Figs. 2 and 3 are diagrams showing the circulating passageway of the hydraulic oil; Fig. 4 is a perspective view showing a partial section of the passageway of the hydraulic oil in the turbine runner; Figs. 5a to 5e are explanatory views showing the shape of the blades of the turbine runner; Fig. 6 is a perspective view of a turbine blade made in accordance with the present invention; Fig. 7 is a cross-sectional view taken along line A-A in Fig. 6;; Figs. 8 to 11 show other embodiments of the turbine blade made in accordance with the present invention in cross-sectional views corresponding to Fig. 7; and Fig. 12 is a diagram showing the improvement of the characteristics of a torque converter of the present invention.

The invention will now be explained by referring to the accompanying drawings.

Fig. 6 shows a blade 2c of turbine runner 2 made according to the present invention. As can be better seen from Fig. 7, which is a crosssectional view taken along line A-A of Fig. 6, the thickness of the blade 2c is made gradually thinner from the input end 2c' of the hydraulic oil toward the output end 2c" thereof. This blade is for use in a turbine runner having the crosssectional area of the passageway of the hydraulic oil decreasing gradually towards the output of the hydraulic oil. If this blade 2c is used for a turbine runner having passageway as shown in Figs. 5a to 5c, the decrease in the cross-sectional area of the passageway may be compensated by the decrease in the thickness of the blade so that the cross-sectional area of the passageway can be maintained constant.

For use in a turbine runner as shown in Fig. 5d, which has a smaller cross-sectional area of the passageway at the input side and gradually increasing towards the output thereof, the thickness distribution of the blade of the present invention may be made opposite to that shown in Figs. 6 and 7. Namely as shown in Fig. 8, the thickness of the blade is maximum at the output end 2c" of the passageway and decreases towards input end 2c' thereof.

For use in a turbine runner as shown in Fig. 5e, which has its largest passageway crosssection in the middle of passageway in the direction of flow and has the cross-sectional area gradually decreasing towards both ends thereof as shown in Fig. 9, the thickness distribution of the blade 2c is maximum in the middle point 2c"' in the direction of flow and gradually decreases towards the input end 2c' and the output end 2c" thereof.

Also in the embodiment, by using the blade 2c for a turbine runner 2 having passageway of which cross-sectional area varies correspondingly, the cross-sectional area of the passageway can be made uniform along the direction of the flow.

According to further aspect of the present invention, instead of varying the thickness of the blade 2c along its whole length continuously so as to make the cross-sectional area uniform throughout the whole length of the passageway as explained in the foregoing embodiment, it is possible in close approximation to cut obliquely the blade 2c only at a portion where the passageway formed by the blades is narrowest.

For instance, if the passageway formed by the blades 2c is narrowest at the output end of the hydraulic oil, the blade 2c may be cut obliquely in the cross-section at the corresponding portion in the proximity of the output end 2c" as shown in Fig. 10 or Fig. 11 by a reference numeral 6. Thus by making only a portion of the blade 2c thinner, the unification of the cross-sectional area of the passageway is obtained in close approximation and the object of the invention may be satisfied to some extent.

In the foregoing explanation, the present invention had been explained with respect to the unification of the passageways provided in the turbine runner, however, other constructional members, such as the pump impeller 1 and the stator or reaction member 3 may have blades according to the present invention. Namely by varying the thickness distribution of the blade 1 C or 3c, the unification of the cross-section of the passageway is obtained so as to realize the object of the present invention In a further aspect of the present invention, the cross-sectional area of the hydraulic oil circulating passageway may be unified throughout different constructional members of the hydraulic transmission device.Namely, in case of a torque converter, the cross-sectional area of the passageway may be unified by combination of the -pump impeller 1, the turbine runner 2 and the stator 3. In this example, the constructional member having a smaller radius of rotation r, i.e.

the blade 3c of the stator 3 is made thinner than the blade 1 C of the pump impeller 1 or the blade 2c of the turbine runner 2 so that the amount of decrease in passageway cross-sectional area by the thickness of the blade is made equal among all the rotatable members. This is by the abovementioned principle that the narrowing of the passageway by the thickness of the blade is more effective at a smaller radius of rotation r.

In a still further aspect of the present invention, if the number of blades are different between members even having equal radius of rotation, i.e.

if such numbers of blades are different in the case of a torque converter for the pump impeller 1 and the turbine runner 2 having the same radius of rotation, namely if the number of blades 1 c and that of 2c provided thereon are different each other, the blades provided on a member having a greater number of blades are made thinner than the blades provided on a member having less blades. This is for the same reason as mentioned above that the passageways for a member having more blades are more restricted by the blades. By this arrangement, it is possible to make the reduction of the cross-sectional area by the thickness of the blades to be the same for both constructional members so that the crosssectional area of the hydraulic oil circulating passageway can be made uniform throughout the whole length of the passageway.

In the foregoing explanation, the present invention has been described by referring to an application for a torque converter. The present invention is not limited for such an application only, but it can be applied equally to other hydraulic transmission devices, for instance, a hydraulic coupling or the like.

The hydraulic transmission device made in accordance with the present invention comprising the hydraulic oil circulating passageway of uniform cross-sectional area throughout the whole length of the passageway as has been mentioned above, the flow loss of the hydraulic oil can be made minimum without causing any adverse influence. Fig. 12 shows an improvement of the characteristics in the case of a torque converter.

Fig. 12 is a graph having its abscissa plotted in conversion velocity ratio e. The ordinate thereof shows torque ratio t, torque capacity coefficient T, and efficiency 11 respectively. In the figure, dotted lines show these values for a conventional device and full lines show the corresponding values for a device of the present invention. As can be seen therefrom all these values show a substantial increase in the case of the present invention so that improvement obtained by the present invention is remarkable.

Claims (5)

1. A hydraulic transmission device comprising a plurality of conestructional members and able to transmit power by means of hydraulic oil being circulated by blades of the members among these members successively, wherein the thickness distribution of the blades is so arranged as to make a cross-sectional area of passageway of the hydraulic oil flowing through a circulating path to be substantially constant along the circulating path.

2. A hydraulic transmission device as claimed in claim 1, wherein the thickness of the blades is made thinner according to an increase of width of the circulating path.

3. A hydraulic transmission device as claimed in claim 1, wherein the thickness of the blades provided on a constructional member having smaller radius of rotation is made thinner than that of blades provided on a constructive member having larger radius of rotation.

4. A hydraulic transmission device as claimed in claim 1, wherein among the blades provided on constructional members of the same radius of rotation, the thickness of the blades provided on a member having more blades are made thinner than that of blades provided on a member having less blades compared thereto.

5. A hydraulic transmission device substantially as described with reference to, and as illustrated in, Figs. 6 and 7, or Fig. 8, or Fig. 9, or Fig. 10, or Fig. 11, of the accompanying drawings.