Power transmission device |
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申请号 | EP10188005.2 | 申请日 | 2007-08-23 | 公开(公告)号 | EP2302244B1 | 公开(公告)日 | 2012-05-23 |
申请人 | Sanden Corporation; | 发明人 | Takai, Kazuhiko c/o Sanden Corporation; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | The present invention relates to a power transmission device, for example, to a power transmission device which is suitable to transmit drive power from a vehicle engine to a device mounted in a vehicle (e.g. a compressor used in an air conditioning system for a vehicle). A power transmission device is frequently required to have a function of a torque limiter which interrupts to transmit excessive drive power. For example, when a drive load at the side of a compressor as a driven body becomes excessive from some reason when the compressor is driven by transmitting drive power from a vehicle engine to the compressor in an air conditioning system for a vehicle, drive power transmission (torque transmission) is desired to be interrupted to protect the vehicle engine or a belt. As such torque transmission interruption mechanisms, various mechanisms are known, such as a rupture-type torque limiter which has a member or a part to be ruptured when a transmission load over a predetermined value is applied between a member at the driving side and a member at the driven side. For example, a power transmission device described in Patent document 1 has a rupture-type torque limiter having a coupling member which is formed between a pulley at the drive source side and a rotation transmission plate attached to a shaft of a compressor at the driven side, and which is to be ruptured when the compressor abnormally stops by a failure, etc. Patent document 1: Japanese Utility Model Laid-Open However, the conventional rupture-type torque limiter as described above generally has the following problems, specifically in a case where the drive source accompanies an output fluctuation like an engine. To be explained by taking the structure shown in the above-described Patent document 1 as an example, in the structure shown in the above-described Patent document 1, as shown in Patent Patent Application Such problems in the conventional devices can be expressed schematically as below. Namely, a rotational fluctuation accompanied with a stroke change of explosion / compression of the engine generates an engine output fluctuation. When the maximum torque value at the side of positive torque including a torque fluctuation in the above-described power transmission device is referred to as Wp, and the maximum torque value at the side of negative torque is referred to as Wn, the total amplitude of the torque fluctuation can be expressed as (Wp+Wn), as shown in Accordingly, an object of the present invention is to provide a power transmission device which can minimize an affection of torque fluctuation which may exist (e.g., even if an output torque fluctuation of an engine may exist) at the side of a driving body, and which can interrupt torque accurately at a target interruption torque value. To solve the above-described problems, a power transmission device according to claim 1 is provided. The present invention comprises a power transmission device, in which a driven body and a driving body for driving the driven body are rotated in the same direction and are connected to each other by a connection section to transmit torque of the driving body to the driven body and in which a transmission of torque from the driving body is interrupted when a drive load on the driven body exceeds a predetermined level, wherein the connection section is constructed by combining separate elements that are a positive torque transmission member which transmits torque in a normal rotational direction and interrupts transmission of torque from the driving body by breaking itself when a drive load on the driven body exceeds the predetermined level, and a negative torque transmission mechanism or a negative torque transmission member which can transmit torque in a reverse rotational direction. Namely, alternate loads of positive torque and negative torque are applied not to a single member but respectively to the separate members comprising the positive torque transmission member and the negative transmission member. Such a structure makes it possible to suppress generation of a fatigue phenomenon only in a single member by the alternate loads, and to prevent the rupture of the torque transmission member at a torque much less than a target interruption torque value. In the power transmission device according to the present invention, it is preferred that a rigidity or a rupture strength of the positive torque transmission member is set lower than a rigidity or a rupture strength of the negative torque transmission mechanism or negative torque transmission member. Such a structure aims to surely realize to rupture the positive torque transmission member when an excessive torque is generated, from the viewpoint of that the torque interruption should be preferably performed against the excessive torque at the positive torque side for protecting devices, at the time of torque interruption at a target interruption torque value. Further, it is preferred that pre-loads in directions opposite to each other are given to the positive torque transmission member and the negative torque transmission mechanism or negative torque transmission member at an assembly condition thereof, and the pre-loads are nearly balanced to each other by relation of action and reaction. By giving such pre-loads, torque fluctuation amplitude during transmission can be greatly reduced as described later, so that an affection of the material fatigue can be suppressed to the minimum. As the above-described pre-loads, for example, a tensile pre-load can be applied to the positive torque transmission member and a compressive pre-load can be applied to the negative torque transmission mechanism or negative torque transmission member, in a device rotational direction. By thus applying both of the tensile pre-load and the compressive pre-load in the device rotational direction together, the tensile pre-load and the compressive pre-load can act in the almost opposite directions during reduction of torque fluctuation amplitude so that the torque fluctuation amplitude can be greatly reduced efficiently and very effectively. A structure of each torque transmission member is not limited especially, and for example, the above-described positive torque transmission member can be constructed as a continuous body extending between the driving body and the driven body. Because the positive torque transmission member is constructed as the continuous body, a target torque interruption can be surely accomplished even if a rupture is generated at any position thereof, so that it is enough to set a part, where the rupture should be generated, loosely in an appropriate range so as to be able to contribute simplification of the structure. Further, a rigidity or a sectional area, etc. of the part where the rupture should be generated can be easily set, thereby facilitating the design. On the other hand, the negative torque transmission mechanism or negative torque transmission member can be formed, for example, in a divisional structure having a contact section in the mechanism or member, namely, a structure, wherein at least two parts have the contact section and a compression load, etc. is given to the contact section, may be employed. If the rupture is generated at the side of the positive transmission member, a target torque interruption can be accomplished, and therefore, the structure at the side of the negative torque transmission mechanism or negative torque transmission member may be enough merely to be able to receive the negative torque, and it is not always necessary to be a continuous body. Rather than that, in a combined structure of the positive torque transmission member and the negative torque transmission mechanism or negative torque transmission member, when a rupture is generated in the positive torque transmission member, a coupling condition in the negative torque transmission mechanism or negative torque transmission member is preferred to be interrupted immediately in conjunction with the rupture of the positive torque transmission member, so as to avoid the negative torque transmission mechanism or negative torque transmission member from becoming an obstacle to the torque interruption condition, and therefore, it is preferably formed in the above-described divisional structure. In the structure where the tensile and compressive pre-loads are applied as described above, a length of a part to which the tensile pre-load of the positive torque transmission member is applied is preferably set shorter than a length of a part to which the compressive pre-load of the above-described negative torque transmission mechanism or negative torque transmission member is applied. By employing such a structure, for example, when both of the positive torque transmission member and the negative torque transmission mechanism or negative torque transmission member are coupled to each other by a bolt, a pin, a rivet, etc., at a condition where the positive torque transmission member is elongated by the tensile pre-load and the negative torque transmission mechanism or negative torque transmission member is compressed by the compressive pre-load, they may be easily assembled, and a condition where pre-loads are mutually applied may be easily realized. Further, the negative torque transmission mechanism can be formed, for example, in such a structure that has a spring section that exhibits a spring force in a device radial direction and has an engagement section that engages a side of the driving body and a side of the driven body via the spring section. In such a case, the engagement section is preferably constructed so as to be able to keep the spring force of the spring section in the device radial direction. Further in that case, the spring section is preferably constructed so as to be able to get back, by its own spring force, to its own free position that is non-interactive with the driving body or driven body, after release of keeping of the spring force that is accompanied with an interruption of torque transmission between the driving body and the driven body. Namely, in such a structure, keeping the spring force of the spring section by the engagement section makes it possible that any torque other than positive torque is not substantially applied to the positive torque transmission member in a torque transmission condition, and the spring section can get back naturally and quickly by its own spring force to its own non-interactive free position after the torque interruption by the rupture of the positive torque transmission member. Further, it is also preferred that the positive torque transmission member and the negative torque transmission member are pre-assembled as parts that can construct the connection section, at a condition applied with respective predetermined pre-loads. In such a structure, because the element constructing the coupling section can be prepared substantially as a single part configuration beforehand, the incorporation thereof into the power transmission device can be extremely facilitated. Furthermore, the device structure can be greatly simplified as a whole. Further, in a case where the negative torque transmission mechanism or negative torque transmission member is formed in the divisional structure as aforementioned, it is preferred that means for regulating relative positional displacement between both sides of the contact section (e.g., means for regulating relative positional displacement in the axial direction of the mechanism or member) is provided for the negative torque transmission mechanism or negative torque transmission member which is constructed as the divisional structure. Thus, by having the means for regulating relative positional displacement, the predetermined structure of the negative torque transmission mechanism or negative torque transmission member can be kept even in a divisional structure. In addition, it is also possible to give this function as the means for regulating relative positional displacement to the positive torque transmission member as shown in the example described later. The power transmission device according to the present invention is effective in a case where there is a fluctuation in an output torque of a source of driving, and specifically, effective in a case where the source of driving force is an engine of a vehicle. When the driving force from the engine of the vehicle is transmitted, since the fluctuation of the engine output is inevitably generated more or less by a rotational fluctuation accompanied with a stroke change of expansion / compression of the engine, a required torque interruption can be accurately performed at the time of torque transmission. Further, the power transmission device according to the present invention is effective, for example, also as a device for transmitting torque to a compressor, and the device can adequately protect the compressor or the drive source side by an accurate torque interruption when an excessive torque is generated. It is specifically effective as a device for transmitting torque to a compressor used in an air conditioner for a vehicle, and in particular, as a device for transmitting torque to a compressor whose drive source is an engine. When an engine is used as a drive source, the above-described pre-loads are preferably greater than a value of torque to be transmitted including a torque fluctuation of the engine and smaller than a set value of torque at which a torque transmission should be interrupted. Such a setting makes it possible that, even if the engine torque fluctuation exists, a usual fluctuation is all within the range of the pre-loads and is absorbed within the range of the pre-loads so as not to be transmitted as a substantial fluctuation to the driven body, and it acts to the coupling section so that a desirable torque interruption is performed, only when an excessive transmission torque is generated by a trouble at the side of the driven body, etc. Thus, in the power transmission device according to the present invention, even if torque fluctuation exists at the side of a drive source or a driving body, for example, even if an engine torque fluctuation exists, its affection can be suppressed to the minimum, and occurrence of fatigue of materials of the connection section can be suppressed and torque can be interrupted accurately at a target interruption torque value. Further, in the power transmission device according to the present invention, the structure of the coupling section may be formed in a simple structure, and therefore, the device can be achieved with few parts at low cost.
Hereinafter, desirable embodiments of the present invention will be explained referring to figures. Each coupling section 7 is constructed by combination of a positive torque transmission member and a negative torque transmission mechanism or a negative torque transmission member which are separated from each other, wherein the positive torque transmission member transmits torque in the normal rotational direction (direction shown by the arrow in Further, negative torque transmission mechanism 9 is provided to transmit negative torque in this example. Such negative torque transmission mechanism 9 is formed in a divisional structure with contact section 12 therein. Further, outer circumferential part in a radial direction of hub body 3 in negative torque transmission mechanism 9 is formed in an arm shape extended substantially in a device rotational direction, and has spring section 13 exhibiting a spring force in a device radial direction, and has engagement section 14 engaging a driving body side (pulley 2 side) and a driven body side (hub body 3 side) via a tip of spring section 13. Engagement section 14 is constructed so as to be able to keep the spring force of spring section 13 in the device radial direction, which can exhibit to get spring section 13 back inside in the device radial direction. Then, spring section 13, as described later, is constructed so as to be get back to its own free position that is non-interactive with the driving body by its own spring force, after release of keeping the spring force that is accompanied with an interruption of torque transmission between the driving body and the driven body. In this example, the above-described positive torque transmission member 8 couples the side of a tip of spring section 13, which is thus kept to engagement section 14 and the side of pulley 2 as driving body. In case that pulley 2 as driving body and hub body 3 as driven body are coupled together via coupling section 7, pre-loads in directions opposite to each other are given respectively to positive torque transmission member 8 and negative torque transmission mechanism 9, which construct coupling section 7 at an assembly condition, with both pre-loads nearly balanced to each other by relation of action and reaction. In this example, a tensile pre-load and a compressive pre-load are applied respectively in the device rotational direction to positive torque transmission member 8 and negative torque transmission mechanism 9, and they are assembled so as to realize such a condition. The tensile pre-load applied to positive torque transmission member 8 is set larger than torque value with consideration of the engine torque fluctuation which is generated between pulley 2 as driving body and hub body 3 as driven body, and is set smaller than a target interruption torque value. Positive torque transmission member 8 has a narrow rupture section existing between coupling sections of both end sections, and can weaken a rigidity at that section by the existing of that section, suppress spring constant of a tension and rupture at that section, when an excessive torque is generated, since the rupture strength at that section is weakened. In order to rupture surely at the side of positive torque transmission member 8, in case that an excessive torque is generated, a rigidity or a rupture strength of positive torque transmission member 8 is set lower than a rigidity or a rupture strength of negative torque transmission mechanism 9. Further, as aforementioned, negative torque transmission mechanism 9 is formed as a divisional structure, and is in a condition where a compressive pre-load is applied by the structure of the portions present at both sides of contact section 12 contacted to each other. If only this part is regarded as an independent structure, because the portions at both sides of contact section 12 are allowed to be moved relatively (in particular, moved to relatively in the plate thickness direction) (a structure capable of being displaced in position), means for regulating relative positional displacement is provided in order to prevent such a relative positional displacement. In this example, because such a means for regulating relative positional displacement is accomplished by being provided at the position where positive torque transmission member 8 extending between pulley 2 and hub body 3 substantially overlaps with contact section 12, positive torque transmission member 8 doubles as the above-described means for regulating relative positional displacement. In thus constructed power transmission device 1 according to example 1, torque is transmitted as described below. Thus, even if an engine torque fluctuation exists, its affection can be suppressed to the minimum. More concretely, amplitude of transmission torque fluctuation can be greatly reduced and a metal fatigue, and a fatigue of positive torque transmission member 8 in particular, can be minimized, and therefore, an accurate operation at the target rupture torque can be performed when an excessive torque is generated. On the other hand, when an excessive torque is generated, as shown in Each coupling section 26, as shown in Further, negative torque transmission member 28 is provided for transmission of negative torque in this example. Such negative torque transmission member 28 is formed in a divisional structure with contact section 31 therein, and has at least two such parts as main body of negative torque transmission member 28a which form contact section 31 and collar 28b in this example. By employing such successive members, coupling section 7 can be assembled as shown at the bottom in Namely, at an assembly condition of sub ASSY of torque transmission member 32, pre-loads in directions opposite to each other are given respectively to positive torque transmission member 27 and negative torque transmission member 28, and the pre-loads are nearly balanced to each other by relation of action and reaction. In this example, a tensile pre-load and a compressive pre-load are applied, respectively in the device rotational direction to positive torque transmission member 27 and negative torque transmission member 28, and they are assembled so as to realize such a condition, at the assembly step of sub ASSY of torque transmission members 32. Also in this case, the tensile pre-load applied to positive torque transmission member 27 is set larger than torque value with consideration of the engine torque fluctuation which is generated between pulley 22 as driving body and hub body 23 as driven body, and is set smaller than a target interruption torque value. Positive torque transmission member 27, similarly in example 1, has a narrow rupture section existing between coupling sections of both end sections, and can weaken a rigidity at that section by the existing of that section, suppress spring constant of a tension and rupture at that section when an excessive torque is produced, since the rupture strength at that section is weakened. In order to rupture surely at the side of positive torque strength of positive torque transmission member 27 in case that an excessive torque is generated, a rigidity or a rupture strength of positive torque transmission member 27 is set lower than a rigidity or a rupture strength of negative torque transmission member 28. Further, as aforementioned, negative torque transmission member 28 is formed as a divisional structure and is in a condition where a compressive pre-load is applied by the structure of the portions present at both sides of contact section 31 contacted to each other. If only this part is regarded as an independent structure, because the portions at both sides of contact section 31 are allowed to be moved relatively (in particular, moved to relatively in the plate thickness direction)(a structure capable of being displaced in position), a means for regulating relative positional displacement is provided in order to prevent such a relative positional displacement. In this example, because such a means for regulating relative positional displacement is accomplished by being nipped with a divisional section (contact section 31) of negative torque transmission member 28 between a head section of pin or rivet 29 and positive torque transmission member 27, the nipping structure comprises the above-described means for regulating relative positional displacement. In thus constructed power transmission device 21 according to example 2, torque is transmitted as described below. Thus, also in example 2, even if an engine torque fluctuation exists, its affection can be suppressed to the minimum. More concretely, amplitude of transmission torque fluctuation can be greatly reduced and a metal fatigue, and a fatigue of positive torque transmission member 27 in particular, can be minimized, and therefre, an accurate operation at the target rupture torque can be performed when an excessive torque is generated. On the other hand, when the excessive torque is generated, as shown in Meanwhile, at the time of such rupture, a condition of coupling section 26 which has been constructed as the above-described assembly part becomes as shown in The power transmission device-related structure according the present invention can be applied to a general power transmission device which can interrupt torque by rupture of coupling member between a rotational driving body and a driven body, and specifically, it is suitable in a case where a drive source is an engine of a vehicle, and for example, where the power is transmitted to a compressor used in an air conditioning system for a vehicle. Conclusively, the present application according to a first aspect describes a power transmission device in which a driven body and a driving body for driving said driven body are rotated in the same direction and are connected to each other by a connection section to transmit torque of said driving body to said driven body and in which a transmission of torque from said driving body is interrupted when a drive load on said driven body exceeds a predetermined level, wherein said connection section is constructed by combining separate elements that are a positive torque transmission member which transmits torque in a normal rotational direction and interrupts transmission of torque from said driving body by breaking itself when a drive load on said driven body exceeds said predetermined level, and a negative torque transmission mechanism or a negative torque transmission member which can transmit torque in a reverse rotational direction. According to a second aspect, the power transmission device according to the first aspect is described, wherein a rigidity or a rupture strength of said positive torque transmission member is set lower than a rigidity or a rupture strength of said negative torque transmission mechanism or negative torque transmission member. A third aspect describes a power transmission device according to the first aspect, wherein pre-loads in directions opposite to each other are given to said positive torque transmission member and said negative torque transmission mechanism or negative torque transmission member at an assembly condition thereof, and said pre-loads are nearly balanced to each other by relation of action and reaction. A fourth aspect describes a power transmission device according to the third aspect, wherein a tensile pre-load is applied to said positive torque transmission member and a compressive pre-load is applied to said negative torque transmission mechanism or negative torque transmission member, in a device rotational direction. A fifth aspect describes a power transmission device according to the first aspect, wherein said positive torque transmission member is constructed as a continuous body extending between said driving body and said driven body. A sixth aspect describes a power transmission device according to the first aspect, wherein said negative torque transmission mechanism or negative torque transmission member is formed in a divisional structure having a contact section in said mechanism or member. In a seventh aspect, a power transmission device according to the fourth aspect is described, wherein a length of a part to which said tensile pre-load of said positive torque transmission member is applied is set shorter than a length of a part to which said compressive pre-load of said negative torque transmission mechanism or negative torque transmission member is applied. In an eighth aspect, a transmission device according to the first aspect is described, wherein said negative torque transmission mechanism has a spring section that exhibits a spring force in a device radial direction and has an engagement section that engages a side of said driving body and a side of said driven body via said spring section. In a ninth aspect of the present invention, a power transmission device according to the eigth aspect is described, wherein said engagement section is constructed so as to be able to keep said spring force of said spring section in said device radial direction. In a tenth aspect, a power transmission device according to a ninth aspect, wherein said spring section is constructed so as to be able to get back, by its own spring force, to its own free position that is non-interactive with said driving body or driven body, after release of keeping of said spring force that is accompanied with an interruption of torque transmission between said driving body and said driven body. In an eleventh aspect, a power transmission device according to the first aspect is described, wherein said positive torque transmission member and said negative torque transmission member are pre-assembled as parts that can construct said connection section, at a condition applied with respective predetermined pre-loads. In a twelfth aspect, a power transmission device according to the sixth aspect is described, wherein means for regulating relative positional displacement between both sides of said contact section is provided for said negative torque transmission mechanism or negative torque transmission member which is constructed as said divisional structure. In a thirteenth aspect, a power transmission device according to the first aspect is described, wherein a source of driving force is an engine of a vehicle. In a fourteenth aspect, a power transmission device according to the first aspect is described, wherein said power transmission device is a device for transmitting torque to a compressor. In a fifteenth aspect, a power transmission device according to the fourteenth aspect is described, wherein said power transmission device is a device for transmitting torque to a compressor used in an air conditioner for a vehicle. In a sixteenth aspect, a power transmission device according to the thirteenth aspect is described, wherein pre-loads which are applied in directions opposite to each other are given to said positive torque transmission member and said negative torque transmission mechanism or negative torque transmission member at an assembly condition thereof, said pre-loads are nearly balanced to each other by relation of action and reaction, and said pre-loads are greater than a value of torque to be transmitted including a torque fluctuation of said engine and smaller than a set value of torque at which a torque transmission should be interrupted |