Patent Publication Number: US-2023163612-A1

Title: Battery holder, power transfer device, electric vehicle and installation method for power transfer device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of U.S. application Ser. No. 16/958,763 filed on Oct. 20, 2021, which is a National Stage of PCT Application No. PCT/CN2018/125679, filed on Dec. 29, 2018, which requests the priority of the Chinese patent application with the application date of Dec. 29, 2017 and the application number of CN201711482966.3 and CN201711486896.9. This application refers to the full text of the above-mentioned Chinese patent application. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of electric vehicles, in particularly relates to a battery holder, a power transfer device, an electric vehicle and installation method for electric vehicle. 
     BACKGROUND 
     The existing battery pack installation methods of electric vehicles are generally divided into fixed type and replaceable type, in which the fixed battery pack is generally fixed on the vehicle, and the vehicle is directly used as the charging object during charging. The replaceable battery pack is usually installed in a movable way, the battery pack can be removed and replaced at any time. 
     In the process of replacing a new battery pack, it involves locking and unlocking the battery pack. Generally speaking, the left and right sides of the battery pack are equipped with locking shafts; the lock mechanism is fixed on the battery pack holder to assemble into a power transfer device, and the power transfer device is installed on the chassis of the electric vehicle; the locking shaft and the lock mechanism cooperate to realize the locking of the battery pack. 
     However, the above structural form has the following defects: only a locking mechanism matched with the locking shaft of the battery pack is arranged on the fixed bracket, and the weight of the battery pack is concentrated on the locking mechanism of the fixed bracket, resulting in the stress concentration of the lock mechanism, the service life of the lock mechanism is low, and the connection strength of the battery pack and the fixed bracket is low. 
     In the process of replacing a new battery pack, the electrical connection device is also involved. The lock mechanism not only affects the connection between the battery pack and the battery pack holder, but also affects the reliability of the electrical connection between the battery pack and the electrical connection device. 
     However, in the prior art, the lock mechanism and the electrical connecting device are arranged independently, the lock mechanism might have locked the battery pack in place, while the reliable electrical connection between the battery pack and the electrical connection device is not achieved, or the battery pack and the electrical connection device are connected reliably, but the battery pack is not locked in place. That is to say, it is difficult to realize the synchronous function of the lock mechanism and the electrical connection device in the prior art, and it is easy to affect the efficiency and reliability of the power exchange. 
     DISCLOSURE OF THE INVENTION 
     The technical problem to be solved by the present invention is to overcome the defects in the prior art and provide a power transfer device and an installation method thereof. 
     The present invention solves the technical problem by the following technical scheme: 
     A battery holder, for being mounted on the body of an electric vehicle to fix a battery pack, the battery holder comprises a fixing bracket and a lock mechanism, the lock mechanism is fixed on the fixing bracket, the battery holder further comprises: 
     a plurality of supporting devices, the supporting device is fixed on one side of the fixing bracket facing the battery pack, and the plurality of supporting devices provide a plurality of support points to support the battery pack. 
     In the present scheme, on the basis of matching the lock mechanism with the locking shaft to realize the locking of the battery pack, a plurality of supporting portions are arranged on the battery pack, and the plurality of supporting devices for supporting the supporting portions are arranged on the fixing bracket, the weight of the battery pack can be simultaneously distributed on the plurality of supporting devices and the lock mechanism, the force is more evenly distributed on the fixing bracket, the force applied by the battery pack to the lock mechanism is reduced, the force concentration of the lock mechanism on the fixing bracket is prevented, the service life of the lock mechanism is improved, so as to improve safety performance, and improve the connection strength between the battery pack assembly and the battery holder. In addition, the structure of battery holder is simple and production cost is low, at the same time, over positioning is avoided, thus reducing the risk that the lock mechanism cannot be unlocked. 
     Preferably, the lock mechanism includes a locking base, the locking base is provided with an opening and a cavity extending from the opening, the opening is used for the locking shaft installed on the battery pack to enter the cavity; the supporting device is provided with a supporting groove, a lower surface of the supporting groove is in the same plane with a lower surface of the cavity. 
     In the present scheme, the lower surface of the supporting groove and the lower surface of the cavity of the lock mechanism are in the same plane, so that the battery pack can be more firmly fixed in the fixing bracket, so that the battery pack can be stably moved. 
     Preferably, the supporting device is provided with a supporting groove; the supporting device comprises a supporting base, the supporting base is provided with a supporting opening and a supporting groove which extends from the supporting opening, and the supporting opening is used for a supporting portion mounted on the battery pack to enter the supporting groove. 
     In the present scheme, when the locking shaft enters the lock mechanism, the supporting portion of the battery pack enters the supporting groove of the battery holder, and at the same time when the locking is in place, the supporting portion is further pressed in the supporting groove of the supporting base, so that the battery pack can be more firmly fixed in the fixing bracket. 
     Preferably, the fixing bracket has an upper-position accommodation cavity, the upper-position accommodation cavity is located above the supporting opening, an upper-position sensor is arranged in the upper-position accommodation cavity, the upper-position sensor is used for detecting whether the supporting portion of the battery pack has passed through the supporting opening; 
     and/or, the fixing bracket has a front-position accommodation cavity, the front-position accommodation cavity is located at the front end of the supporting groove, a front-position sensor is arranged in the front-position accommodation cavity, the front-position sensor is used to detect whether the supporting portion of the battery pack has entered a front end of the supporting groove. 
     In the present scheme, the upper-position sensor detects whether the supporting portion of the battery pack has passed through the supporting opening, so as to determine whether the battery pack has been installed in place relative to the battery holder in the height direction of the electric vehicle; the front-position sensor detect whether the supporting portion of the battery pack has entered the front end of the supporting groove, thus, it can be determined whether the battery pack is installed in place relative to the battery holder in the length direction of the electric vehicle, so that the electric vehicle can be ensure to be driven under the condition that the battery pack is installed in place and improve the safety of the electric vehicle. 
     Preferably, the supporting device further comprises an elastic part, the elastic part is at least partially located in the supporting groove, and the elastic part is used for butting the supporting portion of the battery pack. In the present scheme, the elastic part is not necessary to be in contact with the support, but once in contact, the rigid impact between the supporting portion and the supporting base can be prevented. 
     Preferably, the elastic part comprises an elastic pad, an elastic handle and an elastic head connected in sequence; the elastic pad is located in the supporting groove, the elastic pad is used for abutting against the supporting portion of the battery pack; the elastic handle passes through the supporting base, and a wall portion of the supporting base is clamped between the elastic pad and the elastic head. In the present scheme, in this way, the entire elastic part can be stably installed on the supporting base. 
     Preferably, the supporting base is provided with a locating hole, the supporting device further includes a dowel pin, the dowel pin is partially located outside the locating hole, and the dowel pin is in interference fit with the locating hole; 
     and/or, the supporting base is provided with a mounting hole, the mounting hole is a threaded hole, the supporting base can be detachably connected to the fixing bracket through the mounting hole; 
     and/or, the supporting opening is a bell mouth. 
     In the present scheme, the dowel pin is partially located outside the locating hole, and the dowel pin is in interference fit with the locating hole, when the supporting device is installed on the fixing bracket, the dowel pin can be used for positioning. The mounting hole is a threaded hole, threaded fasteners can be threaded through the mounting holes to mount the supporting device to the fixing bracket. The supporting opening is a bell mouth, which is convenient for the supporting portion to enter the supporting groove. 
     Preferably, the plurality of supporting devices are distributed on both sides of the fixing bracket in the length direction of the fixing bracket. In the present scheme, the above structural setting mode is adopted, the battery pack can be installed on the battery holder more smoothly. Preferably, the numbers of supporting devices respectively located on both sides of the fixing bracket are the same, and the supporting devices arranged on both sides of the fixing bracket are one-to-one corresponding and relatively arranged. Preferably, both sides of the fixing bracket in the length direction of the fixing bracket are provided with the lock mechanisms, the supporting device and the lock mechanism which are on the same side are arranged at intervals. Preferably, in the supporting devices and the lock mechanisms which are on the same side, and in the length direction of the fixing bracket, the supporting devices are distributed at both ends of the fixing bracket, the lock mechanisms are located in the middle part of the fixing bracket. 
     Preferably, at the length direction of the fixing bracket, both sides of the fixing bracket are arranged with two lock mechanisms, the two lock mechanisms on the same side of the fixing bracket are arranged at intervals, and are respectively a primary lock mechanism and a secondary lock mechanism. In the present scheme, the secondary lock mechanism can provide a secondary locking function or a locking protection function for the battery pack, when the primary lock mechanism fails, it is used to prevent the battery pack from falling and improve the safety performance. 
     Preferably, the primary lock mechanism comprises a locking link, at least one primary locking tongue and at least one primary locking base, the primary locking base is fixed on the fixing bracket, the primary locking base is provided with a primary opening and a primary cavity extending from the primary opening, the primary opening is used for the primary locking shaft installed on the battery pack to enter the primary cavity, the locking link is rotatably connected with the at least one primary locking tongue, the locking link is used to drive the primary locking tongue to rotate under the action of external force, so that the primary locking tongue can rotate relative to the primary locking base to change between a primary unlocking state and a primary locking state, when the primary locking tongue is in the primary locking state, the primary locking tongue can prevent the primary locking shaft from leaving the primary cavity from the primary opening; 
     and/or, the secondary lock mechanism comprises: 
     a secondary locking base, the secondary locking base is fixed on the fixing bracket, the secondary locking base is provided with a secondary opening and a secondary cavity extending from the secondary opening, the secondary opening is used for the secondary locking shaft installed on the battery pack to enter the secondary cavity; 
     a secondary locking tongue, the secondary locking tongue can rotate relative to the secondary locking base to change between an unlocking state and a locking state, the secondary locking tongue includes a secondary locking tongue body and a secondary locking tongue extension portion which are fixedly connected, the secondary locking tongue extension portion is on the outside of the secondary locking base, when the secondary locking tongue is in the locking state, the secondary locking tongue body can prevent the secondary locking shaft from leaving the secondary cavity from the secondary opening ; and, 
     a secondary reset part, the secondary reset part is arranged on the secondary locking base, and the secondary reset part acts on the secondary locking tongue, the secondary reset part is able to be elastically deformed, the secondary reset part is used to rotate the secondary locking tongue in a locking direction to reset from the unlocking state to the locking state. 
     In the present scheme, in the secondary lock mechanism, by setting the secondary reset part, it is convenient for the secondary locking tongue to reset from the unlocking state to the locking state, making the battery pack easy to install and lock, in addition, under the action of the secondary reset part, the secondary locking tongue will not easily change to the unlocking state and the locking is more reliable; the secondary locking tongue extension portion is arranged outside the secondary locking base, which can realize the rotation of the secondary locking tongue body by acting on the secondary locking tongue extension portion, and it is convenient for unlocking. 
     Preferably, the fixing bracket comprises a frame and a temporary connector, one side of the frame in the width direction of the fixing bracket has a bracket opening, and the temporary connector is detachably connected to the portions at the two ends of the bracket opening in the frame, and is covered the bracket opening or in the bracket opening; 
     and/or, the battery holder further includes a quick-change sensor, the quick-change sensor is arranged on the fixing bracket, the quick-change sensor is used to detect the position signal of a power transfer equipment and transmit the position signal to a controller. 
     In the present scheme, the temporary connector is detachably connected to the portions in the frame at both ends of the bracket opening, when the battery pack and the battery holder are installed to the electric vehicle, the temporary connector can be removed, which is beneficial to reducing the weight of the electric vehicle. 
     The quick-change sensor is a force off high-voltage sensor, which can detect the position signal of the power transfer equipment. When the power transfer equipment has reached the preset setting, the quick-change sensor transmits the detected signal to the controller, so as to perform a power off operation on the battery pack, and to ensure that the battery pack is replaced in the case of power failure and improve its safety performance. 
     The present invention further provides a power transfer device, characterized in that the power transfer device includes the battery holder as described above, the fixing bracket forms a battery pack containment cavity for containing the battery pack, two sides of the battery pack are provided with locking shafts, and the lock mechanism is fixed on two sides of the battery pack containment cavity, the power transfer device further comprises: 
     a electrical connector of the vehicle side, the electrical connector of the vehicle side is arranged in the battery pack containment cavity, and the electrical connector of the vehicle side faces the electrical connector of the battery side of the battery pack, both of the electrical connector of the vehicle side and the electrical connector of the battery side have a plurality of corresponding poles; 
     wherein when the locking shaft of the battery pack rises in place in the lock mechanism along the height direction of the battery pack, the distance between the locking shaft and the lock point along the length of the battery pack in the lock mechanism is greater than the gap between the electrical connector of the battery side and the electrical connector of the vehicle side along the length direction of the battery pack; 
     when the locking shaft reaches the locking point of the lock mechanism, the pole of the electrical connector of the battery side is abutting against the pole of the electrical connector of the vehicle side. 
     In the present scheme, when the locking shaft of the battery pack is locked in place in the lock mechanism, the electrical connector of the battery side can be reliably connected with the electrical connector of the vehicle side, so as to improve the reliability and efficiency of electric vehicle power exchange by using the power transfer device. 
     Preferably, the distance between the locking shaft and the lock point along the length of the battery pack in the lock mechanism is called a first distance, and the gap between a high-voltage pole of the electrical connector of the battery side and a high-voltage pole of the electrical connector of the vehicle side along the length direction of the battery pack is called a second distance; 
     the height of the low-voltage pole of the electrical connector of the vehicle side is lower than the height of the high-voltage pole of the electrical connector of the vehicle side, and the height difference between the low-voltage pole of the electrical connector of the vehicle side and the high-voltage pole of the electrical connector of the vehicle side is less than or equal to the difference between the first distance and the second distance; 
     or, the height of the low-voltage pole of the electrical connector of the battery side is lower than the height of the high-voltage pole of the electrical connector of the battery side, and the height difference between the low-voltage pole of the electrical connector of the battery side and the high-voltage pole of the electrical connector of the battery side is less than or equal to the difference between the first distance and the second distance. 
     In the present scheme, the relationship between the height difference and the difference makes the high voltage first connected and the low voltage second connected when the electrical connector of the vehicle side is connected with the electrical connector of the battery side. As long as the low voltage contacts, the contactor control switch in the battery pack can output the high voltage. In addition, when the connection between the electrical connector of the vehicle side and the electrical connector of the battery side is disconnected, the low-voltage firstly disconnects to control the high-voltage disconnection, so as to prevent the pole arcing sintering and other adverse phenomena from happening due to the high-voltage not being disconnected. 
     Preferably, the range of height difference between the low-voltage pole of the electrical connector of the vehicle side and the high-voltage pole of the electrical connector of the vehicle side is 0-2 mm. 
     Preferably, the distance between the locking shaft and the lock point along the length of the battery pack in the lock mechanism is called the first distance, and the gap between a high-voltage pole of the electrical connector of the battery side and a high-voltage pole of the electrical connector of the vehicle side along the length direction of the battery pack is called the second distance; 
     the height of the low-voltage pole of the electrical connector of the vehicle side is lower than the height of the high-voltage pole of the electrical connector of the vehicle side, and the height of the low-voltage pole of the electrical connector of the battery side is lower than the height of the high-voltage pole of the electrical connector of the battery side; 
     the sum of the height difference between the low-voltage pole of the electrical connector of the vehicle side and the high-voltage pole of the electrical connector of the vehicle side and the height difference between the low-voltage pole of the electrical connector of the battery side and the high-voltage pole of the electrical connector of the battery side is less than or equal to the difference between the first distance and the second distance. 
     In the present scheme, the relationship between the height difference and the difference makes that the high voltage is connected before the low voltage second is connected when the electrical connector of the vehicle side is connected with the electrical connector of the battery side. As long as the low voltage contacts, a contactor control switch in the battery pack can output high voltage. In addition, when the connection between the electrical connector of the vehicle side and the electrical connector of the battery side is disconnected, the low-voltage firstly disconnects the high-voltage, so as to prevent the pole arcing sintering and other adverse phenomena from happening due to the high-voltage not being disconnected. 
     Preferably, the electrical connector of the vehicle side is used for floating electric connection with the electrical connector of the battery side; 
     preferably, the high-voltage pole of the electrical connector of the vehicle side has an electrical contact end and a wiring terminal; 
     wherein the end face of the electrical contact end of the high-voltage pole is provided with a groove, the groove is concave inwards along the axial direction of the high-voltage pole, the groove is embedded with a conductive elastic part, and the conductive elastic part protrudes from a contact surface of the electrical contact end; preferably, the conductive elastic part is a conductive spring. 
     Preferably, the lock mechanism includes a locking base, the locking base is provided with an opening and a cavity extending from the opening, the opening is used for the locking shaft to enter the cavity; 
     the battery pack holder is provided with an upper-position accommodating cavity, the upper-position accommodating cavity is located above the opening, the upper-position accommodating cavity is provided with an upper-position sensor; the upper-position sensor is used to detect whether the locking shaft has passed through the opening, and to detect whether the locking shaft has risen in place in the lock mechanism along the height direction of the battery pack; 
     and/or, the battery pack holder is provided with a front-position accommodating cavity, the front-position accommodating cavity is located at the front end of the cavity, the front-position accommodating cavity is provided with a front-position sensor; the front-position sensor is used to detect whether the locking shaft has entered the front end of the cavity, and to detect whether the locking shaft has been locked in place in the lock mechanism along the length direction of the battery pack. 
     In the present scheme, the upper-position sensor can detect whether the locking shaft rises in place in the lock mechanism, the front-position sensor can detect whether the locking shaft is locked in place in the front end of the cavity and reaches the locking point, the upper-position sensor and the front-position sensor can improve the locking reliability of the battery pack, which is conducive to improving the electricity connection of the electrical connector of the vehicle side and the electrical connector of the battery side, and further to improve the reliability of the electric vehicle power exchange. 
     Preferably, both sides of the battery pack holder in the length direction of the battery pack holder are provided with two of the lock mechanisms, and the two lock mechanisms on the same side of the battery pack holder are arranged at intervals, and the two lock mechanisms are respectively a primary lock mechanism and a secondary lock mechanism; the electrical connector of the vehicle side is arranged on one side wall of the battery pack holder along the width direction of the battery pack holder; wherein the length direction of the battery pack holder is parallel to the length direction of the battery pack. 
     In the present scheme, when the primary lock mechanism fails, the secondary lock mechanism functions to lock the locking shaft of the battery pack and prevent the battery pack from falling off, which is conducive to further improving the reliability of electric vehicle power exchange. 
     Preferably, the power transfer device further includes a locking protection mechanism, the locking protection mechanism is fixed on the side opposite to the primary lock mechanism on the battery pack holder, and the locking protection mechanism is arranged on the moving path of the locking link to limit the movement of the locking link relative to the primary locking base of the primary lock mechanism; 
     preferably, the locking protection mechanism can move between a first position and a second position relative to the locking link; wherein when the locking protection mechanism is in the first position, the locking protection mechanism acts on the locking link to limit the movement of the locking link relative to the primary locking base; when the locking protection mechanism is in the second position, the locking protection mechanism is separated from the locking link to allow the movement of the locking link relative to the primary locking base. 
     In the present scheme, when the primary lock mechanism locks the locking shaft, the locking protection mechanism can restrict the movement of the locking link relative to the primary locking base, thereby improving the locking effect of the primary lock mechanism, so that the primary lock mechanism can lock the locking shaft reliably. Furthermore, it is beneficial to improve the reliability of electric vehicle. 
     Preferably, the locking protection mechanism includes: 
     a lower housing, the first lower housing can be detachably connected to a side opposite to the locking shaft in the primary locking base, the inner part of the first lower housing has a holding cavity, and the side wall of the lower housing has a through hole communicated with the holding cavity; 
     a locking pin, the locking pin is located in the holding cavity, and the locking pin is penetrated in the locking pin, and can switch between an extended state and a retracted state, wherein when the locking pin is in the extended state, the locking pin is in the first position; when the locking pin is in the retracted state, the locking pin is in the second position. 
     Preferably, the locking protection mechanism further includes: a driving pin, the driving pin acts on the locking pin, and the driving pin can move relative to the locking pin under an action of an external force to be engaged with or separated from the locking pin; wherein when the driving pin is separated from the locking pin, a force is applied to the locking pin along the retraction direction to make the locking pin in the retracted state; when the driving pin is engaged with the locking pin, the locking pin is the extended state. 
     Preferably, the battery pack holder is further provided with a wire harness, the wire harness is used to transmit the upper-position signal detected by the upper-position sensor and the front-position signal detected by the front-position sensor to the power transfer equipment. 
     Preferably, the power transfer device further includes a plurality of support structures, the plurality of support structures are fixed on one side of the battery pack holder facing the battery pack, and the plurality of support structures are used to provide a plurality of support points for supporting the battery pack; 
     preferably, the support structure includes: 
     a supporting base, the supporting base is provided with a supporting opening and a supporting groove extending from the supporting opening, the supporting opening is used for a support part installed on the battery pack to enter the supporting groove; 
     preferably, the plurality of support structures are distributed on both sides of the battery pack holder in the length direction of the battery pack holder, and the support structures arranged on the two sides of the battery pack holder are one-to-one corresponding and relatively arranged; 
     both sides of the battery pack holder in the length direction of the battery pack holder are provided with the lock mechanisms, and the support structures and the lock mechanisms on the same side are interval set. 
     In the present scheme, the supporting mechanism can support the battery pack, facilitate the installation of the battery pack and the battery pack holder, and improve the locking effect of the lock mechanism, so as to improve the power exchange reliability of the electric vehicle. 
     Preferably, the battery pack holder further includes a power exchange sensor, the power exchange sensor is arranged on the battery pack holder, the power exchange sensor is used to sense the power transfer equipment and to control the disconnection of the electrical connection between the electrical connector of the vehicle side and the electrical connector of the battery side. 
     In the present scheme, when the battery pack is removed from the battery pack holder by the power transfer equipment, the power exchange sensor can disconnect the electric connection between the electrical connector of the vehicle side and the electrical connector of the battery side, so as to protect the electric vehicle. 
     The present invention further provides an installation method of the above-mentioned power transfer device, characterized in that the installation method for electric vehicle includes the following steps: 
     S1. install the battery pack from the bottom of the battery pack holder along the height direction of the battery pack into the battery pack holder until the locking shaft rises in place in the lock mechanism along the height direction of the battery pack; 
     S2. move the battery pack forward along its length direction until the locking shaft reaches the locking point in the lock mechanism along the length direction of the battery pack. 
     The present invention further provides an electric vehicle, the electric vehicle includes a battery pack assembly, the battery pack assembly includes a battery pack and a locking shaft, the locking shaft is mounted on the battery pack, the electric vehicle further comprises the battery holder as described above, the battery pack assembly is mounted on the battery holder, the locking shaft is located in the lock mechanism; 
     the battery pack assembly further includes a plurality of supporting portion, the plurality of supporting portion are mounted on the battery pack and are provided in one-to-one correspondence with the plurality of support devices, the supporting devices are used to support the supporting portion correspondingly. 
     In the present scheme, the electric vehicle with the battery holder as above, on the basis of assembling the lock mechanism and the locking shaft to lock the battery pack, a plurality of the supporting portions are mounted on the battery pack to match the plurality of supporting devices on the fixing bracket, the weight of the battery pack can be simultaneously distributed on the plurality of supporting devices and the lock mechanism, the force of the fixing bracket is more evenly, the force applied by the battery pack to the lock mechanism is reduced, the force concentration of the lock mechanism on the fixing bracket is prevented, the service life of the lock mechanism is improved, so as to improve safety performance, and improve the connection strength between the battery pack, battery pack assembly and the battery holder, so as to improve the safety performance of the electric vehicle. 
     Preferably, the lock mechanism includes a locking base, the locking base is provided with an opening and a cavity extending from the opening, the opening is used for the locking shaft to enter the cavity, the locking shaft is mounted on the cavity; 
     the supporting device comprises a supporting base, the supporting base is provided with a supporting opening and a supporting groove which extends from the supporting opening, and the supporting opening is used for the supporting portion to enter the supporting groove; 
     the supporting portion includes a supporting shaft, the supporting shaft is pressed in the supporting base and located in the supporting groove. 
     In the present scheme, when the locking shaft enters the opening, the supporting shaft enters the supporting opening, when the locking shaft enters the cavity of the lock mechanism, the supporting shaft of the battery pack enters the supporting groove of the battery holder, and when the locking is in place, the supporting shaft is further pressed in the supporting groove of the supporting base, so that the battery pack can be more firmly fixed in the fixing bracket. 
     Preferably, the supporting portion further includes a shaft sleeve, the shaft sleeve is rotatably sleeved on the supporting shaft. In the present scheme, the shaft sleeve is rotatably sleeved on the supporting shaft, so that the shaft sleeve can roll, thus ensuring multiple installation, reducing wear and improving the service life of the supporting portion. 
     Preferably, the material of the shaft sleeve is elastic material; 
     and/or, the supporting portion further comprises a gasket, the gasket is sleeved on the supporting shaft and pressed on one end of the shaft sleeve; 
     and/or, the supporting shaft comprises a shaft body and a flange portion, the flange portion is coaxially arranged at one end of the shaft body, the shaft sleeve is sleeved on the shaft body, the flange portion is detachably connected to the battery pack. 
     Preferably, the supporting shaft is provided with an electromagnetic induction component, preferably, the electromagnetic induction component is magnetic steel; 
     the fixing bracket has an upper-position accommodation cavity, the upper-position accommodation cavity is located above the supporting opening, an upper-position sensor is arranged in the upper-position accommodation cavity acts on the electromagnetic induction component to detect whether the supporting portion of the battery pack has passed through the supporting opening; 
     and/or, the fixing bracket has a front-position accommodation cavity, the front-position accommodation cavity is located at the front end of the supporting groove, a front-position sensor is arranged in the front-position accommodation cavity, the front-position sensor acts on the electromagnetic induction component to detect whether the supporting portion of the battery pack has entered the front end of the supporting groove. 
     In the present scheme, the upper-position sensor acts on the electromagnetic induction component to detect whether the supporting portion of the battery pack has passed through the supporting opening. Thus, it can be determined whether the battery pack is installed in place relative to the battery holder in the height direction of the electric vehicle. 
     The front-position sensor acts on the electromagnetic induction component to detect whether the supporting portion of the battery pack has entered the front end of the supporting groove. Thus, it can be judged whether the battery pack is installed in place relative to the battery holder in the length direction of the electric vehicle, so as to ensure that the electric vehicle can drive when the battery pack is installed in place and improve the safety of the electric vehicle. 
     Preferably, one end of the supporting shaft far from the battery pack is provided with a concave part, and the electromagnetic induction element is located in the concave part, and the electromagnetic induction component is on the same plane with the two ends of the supporting shaft far away from the battery pack. 
     Preferably, the supporting portion includes: 
     a supporting shaft, the supporting shaft is pressed in the supporting device; 
     a shaft sleeve, the shaft sleeve is rotatably sleeved on the supporting shaft. 
     Preferably, the electric vehicle further includes a chassis, and the battery holder is fixed on the chassis. 
     On the basis of meeting the general knowledge in the art, the above preferred conditions can be arbitrarily combined to obtain better examples of the invention. 
     The positive progress effect of the present invention lies in that: 
     The battery holder and the electric vehicle including the battery holder of the present invention, on the basis of matching the lock mechanism with the locking shaft to realize the locking of the battery pack, the plurality of supporting portions are arranged on the battery pack, and the plurality of supporting devices for supporting the supporting portions are arranged on the fixing bracket, the weight of the battery pack can be simultaneously distributed on the plurality of supporting devices and the lock mechanism, the force is more evenly applied on the fixing bracket, the force applied by the battery pack to the lock mechanism is reduced, the force concentration of the lock mechanism on the fixing bracket is prevented, the service life of the lock mechanism is improved, so as to improve safety performance, and improve the connection strength between the battery pack assembly and the battery holder. In addition, the structure of battery holder is simple and production cost is low, at the same time, over positioning is avoided, thus reducing the risk that the lock mechanism cannot be unlocked. In the power transfer device of the present invention, when the locking shaft of the battery pack is locked in place in the lock mechanism, the electrical connector of the battery side can be reliably connected with the electrical connector of the vehicle side, so as to improve the reliability and power exchange efficiency of the electric vehicle using the power transfer device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic perspective diagram of the battery holder according to the first embodiment of the present invention. 
         FIG.  2    is a partial schematic diagram of the battery holder according to the first embodiment of the present invention. 
         FIG.  3    is another partial schematic diagram of the battery holder according to the first embodiment of the present invention, wherein the part coincides with  FIG.  2   . 
         FIG.  4    is a schematic structure diagram of the secondary lock mechanism of the battery holder according to the first embodiment of the present invention. 
         FIG.  5    is a schematic structure diagram of the supporting device of the battery holder according to the first embodiment of the present invention. 
         FIG.  6    is a schematic perspective diagram of assembly of a battery pack assembly and a battery holder of an electric vehicle according to the first embodiment of the present invention. 
         FIG.  7    is a schematic perspective diagram of the battery pack assembly of the electric vehicle according to the first embodiment of the present invention. 
         FIG.  8    is a schematic perspective diagram of the supporting portion of the battery pack assembly of the electric vehicle according to the first embodiment of the present invention. 
         FIG.  9    is a schematic internal diagram of the supporting portion of the battery pack assembly of the electric vehicle according to the first embodiment of the present invention. 
         FIG.  10    is a partial schematic diagram of the power transfer device according to the second embodiment of the present invention. 
         FIG.  11    is another partial schematic diagram of the power transfer device according to the second embodiment of the present invention. 
         FIG.  12    is a schematic structure diagram of the primary lock mechanism of the power transfer device according to the second embodiment of the present invention. 
         FIG.  13    is a schematic structure diagram of the secondary lock mechanism of the power transfer device according to the second embodiment of the present invention. 
         FIG.  14    is a schematic sectional diagram of the locking protection mechanism of the power transfer device according to the second embodiment of the present invention, wherein the locking pin is in the extended state. 
         FIG.  15    is a schematic diagram of the exploded structure of the locking protection mechanism of the power transfer device according to the second embodiment of the present invention. 
         FIG.  16    is another schematic sectional diagram of the locking protection mechanism of the power transfer device according to the second embodiment of the present invention, wherein the locking pin is in the retracted state. 
         FIG.  17    is a schematic structure diagram of the locking pin of the locking protection mechanism according to the second embodiment of the present invention. 
         FIG.  18    is a schematic structure diagram of the driving pin of the locking protection mechanism according to the second embodiment of the present invention. 
         FIG.  19    is a schematic structure diagram of the support structure of the power transfer device according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SYMBOLS IN THE FIGURES 
     Embodiment 1 
     battery holder  10 ; fixing bracket  11 ; frame  110 ; bracket opening  111 ; temporary connector  112 ; primary lock mechanism  12 ; locking link  120 ; primary locking tongue  121 ; primary locking base  122 ; primary opening  123 ; primary cavity  124 ; secondary lock mechanism  13 ; secondary locking tongue  130 ; secondary locking tongue body  1300 ; secondary locking tongue extension portion  1301 ; secondary locking base  131 ; secondary opening  132 ; secondary cavity  133 ; secondary reset part  134 ; supporting device  14 ; supporting base  140 ; supporting opening  141 ; supporting groove  142 ; elastic part  143 ; elastic pad  1430 ; elastic head  1431 ; locating hole  144 ; dowel pin  145 ; mounting hole  146 ; battery pack assembly  30 ; battery pack  31 ; primary locking shaft  32 ; secondary locking shaft  33 ; supporting portion  34 ; supporting shaft  340 ; shaft body  3400 ; flange portion  3401 ; shaft sleeve  341 ; gasket  342 ; electromagnetic induction component  343 ; concave part  344 ; width direction of fixing bracket W; length direction of fixing bracket L 
     Embodiment 2 
     locking protection mechanism  10 ; first lower housing  101 ; first holding cavity  1011 ; through hole  1012 ; locking pin  102 ; executive part  1021 ; connecting part  1022 ; second holding cavity  1023 ; first inclined part  1024 ; concave part  1025 ; second electromagnetic induction component  1026 ; driving pin  103 ; blocking part  1031 ; second inclined part  1032 ; first electromagnetic induction component  104 ; first elastic element  105 ; second elastic element  106 ; second lower housing  107 ; third holding cavity  1071 ; upper housing  108 ; fourth holding cavity  1081 ; first sensor  1082 ; second sensor  1083 ; primary lock mechanism  20 ; locking link  201 ; primary locking tongue  202 ; primary locking base  203 ; primary cavity  204 ; unlocking block  205 ; secondary lock mechanism  30 ; secondary locking base  301 ; secondary opening  3011 ; secondary cavity  3012 ; secondary locking tongue  302 ; secondary locking tongue body  3021 ; secondary locking tongue extension portion  3022 ; secondary reset part  303 ; support structure  40 ; supporting base  401 ; supporting opening  402 ; supporting groove  403 ; electrical connector of the vehicle side  50 ; wiring terminal  501 ; electrical contact end  502 ; battery pack holder  60 ; hole  601 ; battery pack containment cavity  602 ; wire harness  70 , low-voltage pole of the electrical connector of the vehicle side  81 , high-voltage pole of the electrical connector of the vehicle side  82 . 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present invention will be further described in the way of embodiments, but it is not limited to the scope of embodiments, but the present invention is not hence limited within the range of the embodiments. 
     Embodiment 1 
     According to an embodiment of the present invention,  FIGS.  1 - 5    show a schematic structure diagram of a battery holder. As shown in  FIGS.  1 - 5   , the battery holder  10  is mounted on the body of a electric vehicle to fix a battery pack  31 , so as to install a quick changeable battery pack or a rechargeable battery pack. The battery holder  10  comprises a fixing bracket  11 , a lock mechanism and a plurality of supporting devices  14 . The lock mechanism is fixed on the fixing bracket  11 . The plurality of supporting devices  14  are fixed on one side of the fixing bracket  11  facing the battery pack  31  and provide a plurality of support points to support the battery pack  31 . 
     In the present embodiment, on the basis of matching the lock mechanism with the locking shaft to realize the locking of the battery pack  31 , a plurality of supporting portions  34  are arranged on the battery pack  31 , and the plurality of supporting devices  14  for supporting the supporting portions  34  are arranged on the fixing bracket  11 , the weight of the battery pack  31  can be simultaneously distributed on the plurality of supporting devices  14  and the lock mechanism, the force is more evenly distributed on the fixing bracket  11 , the force applied by the battery pack  31  to the lock mechanism is reduced, the force concentration of the lock mechanism on the fixing bracket  11  is prevented, the service life of the lock mechanism is improved, so as to improve safety performance, and improve the connection strength between the battery pack assembly  30  and the battery holder  10 . In addition, the structure of battery holder  10  is simple and production cost is low, at the same time, over positioning is avoided, thus reducing the risk that the lock mechanism can not be unlocked. 
     As shown in  FIG.  1   , the fixing bracket is a frame structure. The lock mechanism and the plurality of supporting devices  14  are fixed in the frame of the frame structure. Of course, in other embodiments, the fixing bracket  11  can also be a disc-shaped structure with an annular side wall, a cuboid structure with an opening at the bottom or a plate-shaped structure, which does not limit the protection scope of the present invention. 
     The fixing bracket  11  comprises a frame  110  and a temporary connector  112 . One side of the frame  110  in the width direction of the fixing bracket W has a bracket opening  111 , and the temporary connector  112  is detachably connected to the portions in the frame  110  at both ends of the bracket opening  111 , and covers the bracket opening  111  or is located in the bracket opening  111 . When the battery pack  31  and the battery holder  10  are installed to the electric vehicle, the temporary connector  112  can be removed, which is beneficial to reducing the weight of the electric vehicle. 
     In addition, the lock mechanism generally includes a locking base, the locking base is provided with an opening and a cavity extending from the opening, the opening is used for the locking shaft installed on the battery pack  31  to enter the cavity. The supporting device  14  is provided with a supporting groove  142 , a lower surface of the supporting groove  142  is in the same plane with a lower surface of the cavity. In this way, the battery pack  31  can be more firmly fixed in the fixing bracket  11 , so that the battery pack  31  can be stably moved. 
     In a preferred embodiment, as shown in  FIG.  1   , in the length direction of the fixing bracket L, both sides of the fixing bracket  11  are provided with lock mechanisms, the supporting devices  14  and the lock mechanisms which are on the same side are arranged at intervals. The length direction of the fixing bracket  11  and the length direction of the electric vehicle are approximately same. 
     Further preferably, in the supporting devices  14  and the lock mechanisms which are on the same side, and in the length direction of the fixing bracket L, the supporting devices  14  are distributed at both ends of the fixing bracket  11 , and the lock mechanisms are located in the middle part of the fixing bracket  11 . 
     As shown in  FIGS.  1 - 3   , in the length direction of the fixing bracket L, both sides of the fixing bracket  11  are all arranged with two lock mechanisms. The two lock mechanisms on the same side of the fixing bracket  11  are arranged at intervals, and are respectively a primary lock mechanism  12  and a secondary lock mechanism  13 ; wherein the secondary lock mechanism  13  and the primary lock mechanism  12  are used in cooperation; the primary lock mechanism  12  can refer to the “locking device” disclosed in the Chinese patent application with the publication number of CN106427514A. The secondary lock mechanism  13  can provide a secondary locking function or a locking protection function for the battery pack  31 , when the primary lock mechanism  12  fails, it is used to prevent the battery pack  31  from falling and improve the safety performance. 
     In addition, the primary lock mechanism  12  comprises a locking link  120 , at least one primary locking tongue  121  and at least one primary locking base  122 . The primary locking base  122  is fixed on the fixing bracket  11 . In the present embodiment, three primary locking bases  122  and three primary locking tongues  121  are respectively arranged on both sides of the frame of the fixing bracket  11 .  FIG.  2    and  FIG.  3    are partial schematic diagrams on one side. 
     As shown in  FIGS.  2 - 3   , the primary locking base  122  is provided with a primary opening  123  and a primary cavity  124  extending from the primary opening  123 , the primary opening  123  is used for the primary locking shaft  32  installed on the battery pack  31  to enter the primary cavity  124 . The locking link  120  is rotatably connected with at least one primary locking tongue  121 , which is used to drive the primary locking tongue  121  to rotate under the action of external force, so that the primary locking tongue  121  can rotate relative to the primary locking base  122  to change between a primary unlocking state and a primary locking state. When the primary locking tongue  121  is in the primary locking state, the primary locking tongue  121  can prevent the primary locking shaft  32  from leaving the primary cavity  124  from the primary opening  123 . The “primary locking state” refers to a locking state of the primary lock mechanism  12 ; the “primary unlocking state” refers to an unlocking state of the primary lock mechanism  12 . 
     As shown in  FIG.  4   , the secondary lock mechanism  13  comprises a secondary locking base  131 , a secondary locking tongue  130  and a secondary reset part  134 . The secondary locking base  131  is fixed on the fixing bracket  11 . The secondary locking base  131  is provided with a secondary opening  132  and a secondary cavity  133  extending from the secondary opening  132 , the secondary opening  132  is used for the secondary locking shaft  33  (the structure is the same as or similar to the primary locking shaft  32 ) installed on the battery pack  31  to enter the secondary cavity  133 . 
     The secondary locking tongue  130  can rotate relative to the secondary locking base  131  to change between an unlocking state and a locking state. The secondary locking tongue  130  includes a secondary locking tongue body  1300  and a secondary locking tongue extension portion  1301  which are fixedly connected, the secondary locking tongue extension portion  1301  is on the outside of the secondary locking base  131 . When the secondary locking tongue  130  is in the locking state, the secondary locking tongue body  1300  can prevent the secondary locking shaft  33  from leaving the secondary cavity  133  from the secondary opening  132 . 
     The secondary reset part  134  is arranged on the secondary locking base  131 , and the secondary reset part  134  acts on the secondary locking tongue  130 . The secondary reset part  134  is able to be elastically deformed, the secondary reset part  134  is used to rotate the secondary locking tongue  130  in a locking direction to reset from the unlocking state to the locking state. 
     In the secondary lock mechanism  13 , by setting the secondary reset part  134 , it is convenient for the secondary locking tongue  130  to reset from the unlocking state to the locking state, making the battery pack  31  easy to install and lock, in addition, under the action of the secondary reset part  134 , the secondary locking tongue  130  will not easily change to the unlocking state and the locking is more reliable; the secondary locking tongue  130  extension portion is arranged outside the secondary locking base  131 , which can realize the rotation of the secondary locking tongue  130  body by acting on the secondary locking tongue  130  extension portion, and it is convenient for unlocking. 
     In the present embodiment, as shown in  FIGS.  1 - 5   , the lower surface of the supporting groove  142  is in the same plane with a lower surface of the primary cavity  124  and the secondary cavity  133 . The lower surface of the supporting groove  142 , the lower surface of the primary cavity  124  and the lower surface of the secondary cavity  133  all refer to the surface close to the ground during use, which bear the support function of the supporting portion  34  of the battery pack  31 , the primary locking shaft  32  and the secondary locking shaft  33 , the three are located in the same plane which can make the battery pack  31  move smoothly. 
     In a preferred embodiment, the plurality of supporting devices  14  are distributed on both sides of the fixing bracket  11  in the length direction of fixing bracket L. This enables the battery pack  31  to be more smoothly mounted on the battery holder  10 . The numbers of the supporting devices  14  respectively located on both sides of the fixing bracket  11  are the same, and the supporting devices  14  arranged on both sides of the fixing bracket  11  are one-to-one corresponding and relatively arranged. 
     In the present embodiment, the supporting device  14  is similar to the structure of the primary locking base  122  and the secondary locking base  131 , but it does not have a function of locking and only serves as a supporting platform for the battery pack  31 . In other embodiments, other similar supporting mechanisms with supporting platforms may be applicable. The number of the supporting devices  14  can be adjusted according to the actual weight of the battery pack  31 , preferably the average weight supported by each supporting device  14  does not exceed 25 Kg. 
     As shown in  FIG.  5   , the supporting device  14  comprises a supporting base  140 , the supporting base  140  is provided with a supporting opening  141  and a supporting groove  142  which extends from the supporting opening  141 , and the supporting opening  141  is provided for the supporting portion  34  mounted on the battery pack  31  to enter the supporting groove  142 . 
     When the locking shaft enters the lock mechanism (in the present embodiment, the primary locking shaft  32  enters the primary lock mechanism  12 , the secondary locking shaft  33  enters the secondary lock mechanism  13 ), the supporting portion  34  of the battery pack  31  enters the supporting groove  142  of the battery holder  10 , and at the same time when the locking is complete, the supporting portion  34  is also pressed in the supporting groove  142  of the supporting base  140 , so that the battery pack  31  can be more firmly fixed in the fixing bracket  11 . 
     In addition, the supporting device  14  further comprises an elastic part  143 , the elastic part  143  is at least partially located in the supporting groove  142 , and the elastic part  143  is used for abutting against the supporting portion  34  of the battery pack  31 . The elastic part  143  is not necessary to be in contact with the support  34 , but once in contact, the rigid impact between the supporting portion  34  and the supporting base  140  can be prevented. 
     Specifically, the elastic part  143  comprises an elastic pad  1430 , an elastic handle (not shown), and an elastic head  1431  that are sequentially connected. The elastic pad  1430  is located in the supporting groove  142 , and is used for abutting against the supporting portion  34  of the battery pack  31 . The elastic handle passes through the supporting base  140 , and a wall portion of the supporting base  140  is clamped between the elastic pad  1430  and the elastic head  1431 . In this way, the entire elastic part  143  can be stably installed on the supporting base  140 . The elastic part  143  is preferably made of rubber. 
     Further, the supporting base  140  is provided with a locating hole  144 . The supporting device  14  further includes a dowel pin  145 . The dowel pin  145  is partially located outside the locating hole  144 , and the dowel pin  145  is in interference fit with the locating hole  144 . When the supporting device  14  is installed on the fixing bracket  11 , the dowel pin  145  can be used for positioning. 
     The supporting base  140  is provided with a mounting hole  146 , the mounting hole  146  is a threaded hole, the supporting base  140  can be detachably connected to the fixing bracket  11  through the mounting hole  146 . The supporting opening  141  is a bell mouth, which is convenient for the supporting portion  34  to enter the supporting groove  142 . 
     As shown in  FIGS.  1 - 3  and  5   , the fixing bracket  11  has an upper-position accommodation cavity (not shown), which is located above the supporting opening  141 . An upper-position sensor (not shown) is arranged in the upper-position accommodation cavity to detect whether the supporting portion  34  of the battery pack  31  has passed through the supporting opening  141 , so as to determine whether the battery pack  31  has been installed in place relative to the battery holder  10  in the height direction of the electric vehicle. 
     The fixing bracket  11  has a front-position accommodation cavity (not shown), which is located at a front end of the supporting groove  142 . The front end refers to the position close to the front of the electric vehicle in the length direction. A front-position sensor (not shown) is arranged in the front-position accommodation cavity, which is used to detect whether the supporting portion  34  of the battery pack  31  has entered the front end of the supporting groove  142 . Thus, it can determine whether the battery pack  31  is installed in place relative to the battery holder  10  in the length direction of the electric vehicle, so that the electric vehicle can be ensure to be driven under the condition that when the battery pack  31  is installed in place, which improves the safety of the electric vehicle. 
     The battery holder  10  further includes a quick-change sensor (not shown), which is arranged on the fixing bracket  11 . The quick-change sensor is used to detect a position signal of a power transfer equipment and transmit the position signal to a controller. The quick-change sensor is a force off high-voltage sensor, which can detect the position signal of the power transfer equipment. When the power transfer equipment has reached the preset setting, the quick-change sensor transmits the detected signal to the controller, so as to perform a power off operation on the battery pack  31 , and to ensure that the battery pack  31  is replaced in the case of power failure and improve its safety performance. 
     The present invention further provides an electric vehicle, as shown in  FIG.  6   , the electric vehicle includes a battery pack assembly  30  and the battery holder  10  as above, the battery pack assembly  30  is mounted on the battery holder  10 . In the present embodiment, the electric vehicle further includes a chassis (not shown), and the battery holder  10  is fixed on the chassis. 
     As shown in  FIG.  7   , the battery pack assembly  30  includes the battery pack  31  and the locking shaft (in the present embodiment, the locking shaft comprises a primary locking shaft  32  and a secondary locking shaft  33 ), the locking shaft is mounted on the battery pack  31 . The locking shaft is located in the lock mechanism (in the present embodiment, the primary locking shaft  32  is located in the primary lock mechanism  12 , the secondary locking shaft  33  is located in the secondary lock mechanism  13 ). 
     The battery pack assembly  30  further includes a plurality of supporting portion  34 , the plurality of supporting portion  34  are mounted on the battery pack  31  and are provided in one-to-one correspondence with the plurality of support devices  14 , the supporting devices  14  are used to support the corresponding supporting portion  34 . 
     The electric vehicle with the battery holder  10  as above, on the basis of assembling the lock mechanisms and the locking shafts to lock the battery pack  31 , the plurality of the supporting portions  34  are mounted on the battery pack  31  to match the plurality of supporting devices  14  on the fixing bracket  11 , the weight of the battery pack  31  can be simultaneously distributed on the plurality of supporting devices  14  and the lock mechanisms, the force of the fixing bracket  11  is more evenly, the force applied by the battery pack  31  to the lock mechanism is reduced, the force concentration of the lock mechanism on the fixing bracket  11  is prevented, the service life of the lock mechanism is improved, so as to improve safety performance, and to improve the connection strength between the battery pack  31  battery pack assembly  30  and the battery holder  10 , so as to improve the safety performance of the electric vehicle. 
     As shown in  FIG.  5    and  FIGS.  8 - 9   , the supporting portion  34  includes the supporting shaft  340 , the supporting shaft  340  is pressed in the supporting base  140  and located in the supporting groove  142 . When the locking shaft enters the opening (in the present embodiment, the primary locking shaft  32  enters the primary opening  123 , and the secondary locking shaft  33  enters the secondary opening  132 ), the supporting shaft  340  enters the supporting opening  141 , when the locking shaft enters the cavity of the lock mechanism (in the present embodiment, the primary locking shaft  32  enters the primary cavity  124  of the primary lock mechanism  12 , the secondary locking shaft  33  enters the secondary cavity  133  of the secondary lock mechanism  13 ), the supporting shaft  340  of the battery pack  31  enters the supporting groove  142  of the battery holder  10 , and when the locking is in place, the supporting shaft  340  is also pressed in the supporting groove  142  of the supporting base  140 , so that the battery pack  31  can be more firmly fixed in the fixing bracket  11 . 
     In addition, the supporting portion  34  further includes a shaft sleeve  341 , the shaft sleeve  341  is rotatably sleeved on the supporting shaft  340 . The shaft sleeve  341  is rotatably sleeved on the supporting shaft  340 , so that the shaft sleeve  341  can roll, thus ensuring multiple installations, reducing wear and improving the service life of the supporting portion  34 . The preferable material of the shaft sleeve  341  is elastic material. 
     In a preferred embodiment, the supporting portion  34  further comprises a gasket  342 , the gasket  342  is sleeved on the supporting shaft  340  and pressed on one end of the shaft sleeve  341 . The supporting shaft  340  comprises a shaft body  3400  and a flange portion  3401 , the flange portion  3401  is coaxially arranged at one end of the shaft body  3400 , the shaft sleeve  341  is sleeved on the shaft body  3400 , the flange portion  3401  is detachably connected to the battery pack  31 . 
     Further preferably, the supporting shaft  340  is provided with an electromagnetic induction component  343 . The electromagnetic induction component  343  is preferably magnetic steel. One end of the supporting shaft  340  far from the battery pack  31  is provided with a concave part  344 , and the electromagnetic induction element  343  is located in the concave part  344 . And the electromagnetic induction component  343  is on the same plane with the two ends of the supporting shaft  340  far away from the battery pack  31 . 
     An upper-position sensor acts on the electromagnetic induction component  343  to detect whether the supporting portion  34  of the battery pack  31  has passed through the supporting opening  141 . Thus, it can be determined whether the battery pack  31  is installed in place relative to the battery holder  10  in the height direction of the electric vehicle. 
     An front-position sensor acts on the electromagnetic induction component  343  to detect whether the supporting portion  34  of the battery pack  31  has entered the front end of the supporting groove  142 . Thus, it can be determined whether the battery pack  31  is installed in place relative to the battery holder  10  in the length direction of the electric vehicle, so that the electric vehicle can be ensure to be driven under the condition that the battery pack  31  is installed in place and improve the safety of the electric vehicle. 
     Then, mainly refer to  FIGS.  4 - 5    and  FIG.  7   , the working process of the secondary lock mechanism  13  and the supporting device  14  is briefly described, mainly including an unlocking process and a locking process, in which the initial state is the locking state. 
     The locking process: the secondary locking shaft  33  moves upward under the action of an external force and enters the secondary cavity  133  through the secondary opening  132 . The secondary locking shaft  33  acts on the secondary locking tongue  130  to make the secondary locking tongue  130  rotate counterclockwise, at the same time, the supporting portion  34  moves upward under the action of an external force and enters the supporting groove  142  through the support opening  141 ; the secondary locking tongue  130  acts on the secondary reset part  134  to make the elastic force of the secondary reset part  134  changed; after the secondary locking tongue  130  is rotated to a certain angle, a channel for the secondary locking shaft  33  to pass through is formed in the secondary cavity  133 , the secondary locking shaft  33  can move from back to front, and at the same time, the supporting portion  34  can move from back to front in the supporting groove  142 ; until the secondary locking shaft  33  is no longer in contact with the secondary locking tongue  130 , the secondary locking tongue  130  rotates clockwise under the action of the reset part to reset to the locked state. When the secondary locking shaft  33  is locked in place, the supporting portion  34  is also installed in place. 
     The unlocking process: a force is applied to the secondary locking tongue  130  to make the secondary locking tongue  130  rotate counterclockwise; the secondary locking tongue  130  acts on the secondary reset part  134  to change the elastic force of the secondary reset part  134 ; after the secondary locking tongue  130  rotates to a certain angle, a channel for the secondary locking shaft  33  to pass through in the secondary cavity  133  is formed; the secondary locking shaft  33  can move from front to back, then moves downward through the secondary opening  132  to leave the secondary lock mechanism  13 , at the same time, the supporting portion  34  can move from front to back in the supporting groove  142 , and then moves downward through the supporting opening  141  to leave the supporting device  14 . 
     Embodiment 2 
     The present embodiment discloses a power transfer device for power exchange of an electric vehicle. As shown in  FIG.  10    and  FIG.  11   , the power transfer device includes a battery pack holder  60  (the battery pack holder corresponds to the battery holder in embodiment 1) and an electrical connector of the vehicle side of vehicle side  50 . The fixing bracket of the battery pack holder forms a battery pack containment cavity  602  for containing the battery pack (not shown in the figure), two sides of the battery pack are provided with locking shafts, and the lock mechanism is fixed on two sides of the battery pack containment cavity  602 . The electrical connector of the vehicle side  50  is arranged on one side of the electrical connector of the battery side facing the battery pack in the battery pack containment cavity  602 . When the locking shaft of the battery pack rises along the height direction of the battery pack in place in the lock mechanism, the distance between the locking shaft and the lock point along the length of the battery pack in the lock mechanism is greater than the gap between the electrical connector of the battery side and the electrical connector of the vehicle side  50  along the length direction of the battery pack. When the locking shaft reaches the locking point of the lock mechanism, the electrical connector of the battery side and the electrical connector of the vehicle side  50  are under interference fit. 
     In the present embodiment, when the locking shaft of the battery pack is locked in place in the lock mechanism, the electrical connector of the battery side can be reliably connected with the electrical connector of the vehicle side  50 , so as to improve the reliability and efficiency of battery exchange of the electric vehicle by using the battery transfer device. 
     For ease of description, the distance between the locking shaft and the lock point along the length of the battery pack in the lock mechanism is called a first distance, and the gap between the high-voltage pole of the electrical connector of the battery side and the high-voltage pole of the electrical connector of the vehicle side  82  along the length direction of the battery pack is called a second distance. In the present embodiment, the height of the low-voltage pole of the electrical connector of the vehicle side  81  is lower than the height of the high-voltage pole of the electrical connector of the vehicle side  82 , and the height difference between the low-voltage pole of the electrical connector of the vehicle side  81  and the high-voltage pole of the electrical connector of the vehicle side  82  is less than or equal to the difference between the first distance and the second distance. 
     In the present embodiment, the relationship between the height difference and the difference makes that the high voltage is connected before the low voltage is connected when the electrical connector of the vehicle side  50  is connected with the electrical connector of the battery end. As long as the low voltage contacts, a contactor control switch in the battery pack can output high voltage. In addition, when the connection between the electrical connector of the vehicle side  50  and the electrical connector of the battery is disconnected, the low-voltage firstly disconnects the high-voltage, so as to prevent the pole arcing sintering and other adverse phenomena from happening due to the high-voltage not being disconnected. Preferably, the range of height difference between the low-voltage pole of the electrical connector of the vehicle side  81  and the high-voltage pole of the electrical connector of the vehicle side  82  is 0-2 mm. In the present embodiment, the height difference between the low-voltage pole of the electrical connector of the vehicle side  81  and the high-voltage pole of the electrical connector of the vehicle side  82  is 1 mm. 
     It should be noted that on the basis that the electrical connector of the vehicle side  50  and the electrical connector of the battery side can be realized, the height difference between the low-voltage pole of the electrical connector of the vehicle side  81  and the high-voltage pole of the electrical connector of the vehicle side  82  can be any value between 0 and the difference between the first distance and the second distance. 
     In other alternative embodiments, it can also be set as: the height of the low-voltage pole of the electrical connector of the battery side is lower than the height of the high-voltage pole of the electrical connector of the battery side, and the height difference between the low-voltage pole of the electrical connector of the battery side and the high-voltage pole of the electrical connector of the battery side is less than or equal to the difference between the first distance and the second distance. 
     In another alternative embodiment, it can also be set as: the height of the low-voltage pole of the electrical connector of the vehicle side  81  is lower than the height of the high-voltage pole of the electrical connector of the vehicle side  82 , and the height of the low-voltage pole of the electrical connector of the battery side is lower than the height of the high-voltage pole of the electrical connector of the battery side; the sum of the height difference between the low-voltage pole of the electrical connector of the vehicle side  81  and the high-voltage pole of the electrical connector of the vehicle side  82  and the height difference between the low-voltage pole of the electrical connector of the battery side and the high-voltage pole of the electrical connector of the battery side is less than or equal to the difference between the first distance and the second distance. 
     In the present embodiment, the connection between the electrical connector of the battery side and the electrical connector of the vehicle side is floating electrical connection, the high-voltage pole of the electrical connector of the vehicle side  82  in  FIG.  10    has an electrical contact end  502  and a wiring terminal  501 , wherein the end face of the electrical contact end  502  of the high-voltage pole is provided with a groove (not shown in the figure), the groove is concave inwards along the axial direction of the high-voltage pole, the groove is embedded with a conductive elastic part (not shown in the figure), and the conductive elastic part protrudes from a contact surface of the electrical contact end  502 . Preferably, the conductive elastic part is a conductive spring. In addition, the electrical connector of the vehicle side  50  includes a flexible electrical connector (not shown in the figure) and a high-voltage plug, one end of the flexible electrical connector is floating electrically connected with the wiring terminal  501  of the high-voltage pole. The high-voltage plug is floating electrically connected with the other end of the flexible electrical connector. 
     In the present embodiment, the lock mechanism includes a locking base, the locking base is provided with an opening and a cavity extending from the opening, the opening is used for the locking shaft to enter the cavity. The battery pack holder  60  is provided with an upper-position accommodating cavity which is located above the opening, the upper-position accommodating cavity is provided with an upper-position sensor, the upper-position sensor is used to detect whether the locking shaft has passed through the opening, and has installed in place in the lock mechanism along the height direction of the battery pack. The battery pack holder  60  is further provided with a front-position accommodating cavity, which is located at the front end of the cavity, the front-position accommodating cavity is provided with a front-position sensor, the front-position sensor is used to detect whether the locking shaft has entered the front end of the cavity, and has installed in place in the lock mechanism along the length direction of the battery pack. 
     In the present embodiment, the upper-position sensor can detect whether the locking shaft rises in place in the lock mechanism, the front-position sensor can detect whether the locking shaft locks in place in the front end of the cavity and reaches the locking point, the upper-position sensor and the front-position sensor can improve the locking reliability of the battery pack, which is conducive to improving the electricity connection of the electrical connector of the vehicle side  50  and the electrical connector of the battery side, and further to improve the reliability of the electric vehicle power exchange. 
     As shown in  FIG.  10   , the battery pack holder  60  is further provided with a wire harness  70 , which is used to transmit the upper-position signal detected by the upper-position sensor and the front-position signal detected by the front-position sensor to the power transfer equipment. 
     Referring to  FIG.  10    and  FIG.  11   , two lock mechanisms are arranged on both sides of the battery pack holder  60  in the length direction of the battery pack holder, and the two lock mechanisms on the same side of the battery pack holder  60  are arranged at intervals, and the two lock mechanisms are respectively a primary lock mechanism and a secondary lock mechanism. The electrical connector of the vehicle side  50  is arranged on one side wall of the battery pack holder  60  along the width direction of the battery pack holder  60 . The length direction of the battery pack holder  60  is parallel to the length direction of the battery pack. When the primary lock mechanism  20  fails, the secondary lock mechanism  30  functions to lock the locking shaft of the battery pack and prevent the battery pack from falling off, which is conducive to further improving the reliability of electric vehicle power exchange. 
     Referring to  FIGS.  10 - 12   , the primary lock mechanism  20  includes a locking link  201 , at least one primary locking tongue  202 , at least one primary locking base  203 , the primary locking base  203  is fixed on the battery pack holder  60 , the primary locking base  203  is provided with a primary opening and a primary cavity  204  extending from the primary opening, the primary opening is used for the primary locking shaft of the battery pack to enter the primary cavity  204 , and the locking link  201  is rotatably connected with at least one primary locking tongue  202  to drive the primary locking tongue  202  to rotate under the action of external force, so that the primary locking tongue  202  can rotate relative to the primary locking base  203  to change between a primary unlocking state and a primary locking state, when the primary locking tongue  202  is in the primary unlocking state, the primary locking tongue  202  can prevent the primary locking shaft from leaving the primary cavity  204  from the primary opening. One side of the locking link  201  toward the primary locking base  203  is further provided with an unlocking block  205 , the unlocking block  205  is an arc convex formed outward from the locking link  201 , and the top of the unlocking block  205  is an inner arc groove concave into the locking link  201 . In the present embodiment, the number of the primary locking tongue  202  and the number of the primary locking base  203  are both three. 
     Referring to  FIG.  10    and  FIG.  13   , the secondary lock mechanism  30  includes a secondary locking base  301 , a secondary locking tongue  302  and a secondary reset part  303 . Wherein, the secondary locking base  301  is fixed on the battery pack holder  60 , the secondary locking base  301  is provided with a secondary opening  3011  and a secondary cavity  3012  extending from the secondary opening  3011 , and the secondary opening  3011  is used for the secondary locking shaft of the battery pack to enter the secondary cavity  3012 . The secondary locking tongue  302  can rotate relative to the secondary locking base  301  to change between a secondary unlocking state and a secondary locking state. The secondary locking tongue  302  includes a secondary locking tongue body  3021  and a secondary locking tongue extension portion  3022 , the secondary locking tongue body  3021  and the secondary locking tongue extension portion  3022  are fixedly connected, the secondary locking tongue extension portion  302  is located outside the secondary locking base  301 . When the secondary locking tongue  302  is in the secondary locking state, the secondary locking tongue body  3021  can prevent the secondary locking shaft from leaving the secondary cavity  3012  from the secondary opening  3011 . The secondary reset part  303  is arranged on the secondary locking base  301  and acts on the secondary locking tongue  302 , the secondary reset part  303  is capable of elastic deformation, the secondary reset part  303  is used to rotate the secondary locking tongue  302  in a locking direction to reset from the secondary unlocking state to the secondary locking state. 
     Referring to  FIG.  10   ,  FIG.  11    and  FIGS.  14 - 16   , the power transfer device further includes a locking protection mechanism  10 . The locking protection mechanism  10  is fixed on the side opposite to the primary lock mechanism on the battery pack holder  60 , and the locking protection mechanism  10  is arranged on the moving path of the locking link  201  to limit the movement of the locking link  201  relative to the primary locking base  203 . The locking protection mechanism  10  can move between a first position and a second position relative to the locking link  201 . When the locking protection mechanism  10  is in the first position, the locking protection mechanism  10  acts on the locking link  201  to limit the movement of the locking link  201  relative to the primary locking base  203 ; when the locking protection mechanism  10  is in the second position, the locking protection mechanism  10  is separated from the locking link  201  to allow the movement of the locking link  201  relative to the primary locking base  203 . 
     When the primary lock mechanism  20  locks the locking shaft, the locking protection mechanism  10  can limit the movement of the locking link  201  relative to the primary locking base  203 , thereby improving the locking effect of the primary lock mechanism  20 , so that the primary lock mechanism  20  can lock the locking shaft reliably. Furthermore, it is beneficial to improve the reliability of electric vehicle. 
     Understand with reference to  FIG.  11    and  FIGS.  14 - 18   , the locking protection mechanism  10  includes a first lower housing  101  and a locking pin  102 . The first lower housing  101  can be detachably connected to a side opposite to the locking shaft in the primary locking base  203 , the inner part of the first lower housing  101  has a first holding cavity  1011 , and the side wall of the lower housing has a through hole  1012  communicated with the first holding cavity  1011 . The locking pin  102  is located in the first holding cavity  1011 , and the locking pin penetrates in the through hole  1012 , and can switch between an extended state and a retracted state. Wherein, when the locking pin  102  is in the extended state, the locking pin  102  is in the first position; when the locking pin  102  is in the retracted state, the locking pin  102  is in the second position. The switching of the locking pin  102  between the first position and the second position is realized by controlling the extension and retraction of the locking pin  102 , which is simple in structure and easy to realize. In addition, as shown in  FIG.  2   , a hole  601  is arranged on the battery pack holder  60 , and the locking pin  102  switches between the first position and the second position through the hole  601 . 
     The locking protection mechanism  10  further includes a driving pin  103 , a first electromagnetic induction component  104  and a first elastic element  105 . The driving pin  103  acts on the locking pin  102 , and the driving pin  103  can move relative to the locking pin  102  to be engaged with or separate from the locking pin  102 . The first electromagnetic induction component  104  is arranged on the driving pin  103 , the first electromagnetic induction component  104  is used to drive the driving pin  103  to exert a force on the locking pin  102  along the retraction direction of the locking pin  102  under an action of an external electromagnetic equipment. The first elastic element  105  is connected to one end of the locking pin  102  far away from the cavity, the first elastic element  105  is abutted between the locking pin  102  and the inner wall surface of the first holding cavity  1011 , and the first elastic element  105  is used to apply a force to the locking pin  102  in the extending direction of the locking pin  102 . When the first electromagnetic induction component  104  is engaged with the external electromagnetic device, the driving pin  103  is separated from the locking pin  102 , and a force is applied to the locking pin  102  along the retraction direction to make the locking pin  102  in the retracted state; when the first electromagnetic induction component  104  is separated from the external electromagnetic device, the first elastic element  105  exerts a force on the locking pin  102  in the extension direction, and the driving pin  103  is engaged with the locking pin  102 , so that the locking pin  102  is in the extended state. 
     In the present embodiment, when the first electromagnetic induction component  104  is engaged with an external electromagnetic device, the driving pin  103  moves away from the locking pin  102 , and a force is applied to the locking pin  102  along the retraction direction, so that the locking pin  102  retracts, and the locking pin  102  will squeeze the first elastic element  105 . When the driving pin  103  is completely separated from the locking pin  102 , the first elastic element  105  provides a restoring force to the locking pin  102  to return the locking pin  102  to a position for engagement with the driving pin  103 . When the first electromagnetic induction component  104  is separated from the external electromagnetic device, the driving pin  103  moves in a direction toward the locking pin  102  to engage with the locking pin  102 , so that the locking pin  102  is in the extension state. In addition, in the present embodiment, the magnetic engagement method is used to control the engagement and separation of the driving pin  103  and the locking pin  102 , and then to control the extension and retraction of the locking pin  102 . The control method is simple and the control efficiency is high. 
     The locking pin  102  has an executive part  1021  and a connecting part  1022 . The connecting part  1022  is connected to one end of the executing part  1021  which is far away from the primary cavity  204 , the connecting part  1022  has a second holding cavity  1023  which used for holding the driving pin  103 . The first elastic element  105  is connected to the end of the connecting part  1022  far away from the executing part  1021 , the first elastic element  105  is butted between the connecting part  1022  and the inner wall surface of the first holding cavity  1011 , and the first elastic element  105  exerts a force on the connecting part  1022  in the extending direction. When the driving pin  103  is engaged with the locking pin  102 , one end of the driving pin  103  close to the locking pin  102  is clamped to the second holding cavity  1023 , which belongs to the embedded connection and occupies less space. 
     In the present embodiment, a first angle is formed between the length direction of the connecting part  1022  and the height direction of the driving pin  103 , and the second holding cavity  1023  extends along the height direction of the driving pin  103 , so that the driving pin  103  moves in the height direction of the driving pin  103  relative to the locking pin  102 . 
     The driving pin  103  has a head end and a tail end along its height direction, the head end of the driving pin  103  is embedded in the second holding cavity  1023 , and the first electromagnetic induction component  104  is arranged in the tail end of the driving pin  103 . The inner wall surface of the second holding chamber  1023  is provided with a first inclined part  1024 , and the first end of the driving pin  103  is provided with a second inclined part  1032  adapted to the first inclined part  1024 . When the driving pin  103  is engaged with the locking pin  102 , the first inclined part  1024  is attached to the second inclined part  1032 ; when the driving pin  103  is separated from the locking pin  102 , the second inclined part  1032  moves downward relative to the first inclined part  1024 , and applies a force to the locking pin  102  along the retraction direction, so as to make the locking pin  102  in the retraction state. 
     In the present embodiment, the engagement of the first inclined part  1024  and the second inclined part  1032  are ingeniously used, when the driving pin  103  moves in a direction away from the locking pin  102 , the first inclined part  1024  slides relative to the second inclined part  1032 . The friction force applied by the first inclined part  1024  to the second inclined part  1032  can be decomposed into a component force along the retraction direction, and under the function of the component force, the locking pin  102  retracts back. 
     The inner wall surface of the second holding cavity  1023  is further provided with a concave part  1025 , and the head end of the driving pin  103  is provided with a convex part which is matched with the concave part  1025 . The inner wall surface of the second holding cavity  1023  is provided with two first inclined parts  1024 , and the two first inclined parts  1024  are relatively arranged on both sides of the concave part  1025 . In the present embodiment, the concave part  1025  can play a limiting role on the driving pin  103 , help to make the driving pin  103  reliably engage with the locking pin  102 , thus help to realize the stable extension of the locking pin  102 , and help to realize the reliable locking of the locking shaft. 
     The first electromagnetic induction component  104  is embedded in the tail end of the driving pin  103 . In this way, the first electromagnetic induction component  104  does not occupy additional space outside the driving pin  103 , which is beneficial to improve space utilization. In addition, it is also advantageous to protect the first electromagnetic induction component  104 . 
     In addition, the tail end of the driving pin  103  is sleeved of a second elastic element  106 , the second elastic element  106  exerts a force on the driving pin  103  in a direction close to the connecting part  1022 , wherein the force exerted by the second elastic element  106  on the driving pin  103  is greater than the gravity of the driving pin  103 . In this present embodiment, when the driving pin  103  is engaged with the locking pin  102 , the force applied by the second elastic element  106  to the driving pin  103  can prevent the driving pin  103  from falling under the action of gravity, thus further improving the reliability of the engagement of the driving pin  103  and the locking pin  102 . When the driving pin  103  is required to move towards the direction close to the locking pin  102 , the force applied by the second elastic element  106  to the driving pin  103  can overcome the gravity of the driving pin  103 , so that the driving pin  103  can move towards the direction close to the locking pin  102  more reliably. 
     The locking protection mechanism  10  further includes a second lower housing  107 , the second lower housing  107  is connected to the bottom of the first lower housing  101 , the second lower housing  107  has a third holding cavity  1071 , the third holding cavity  1071  is intercommunication with the first holding cavity  1011 , and the driving pin  103  is located in the third holding cavity  1071 . A second angle is formed between the central axis of the second lower housing  107  and the central axis of the first lower housing  101 , and the second angle is equal to the first angle. 
     In addition, the outer wall surface of the driving pin  103  is provided with a blocking part  1031  corresponding to both ends of the second elastic element  106 , and the second elastic element  106  is clamped between the two blocking parts  1031 . That is to say, in the present embodiment, the second elastic element  106  is integrally sleeved on the outer wall surface of the driving pin  103 , and the second elastic element  106  is a spring. The main function of the blocking part  1031  is to locate the second elastic element  106  to restrict the movement of the second elastic element  106  along the height direction of the driving pin  103 . 
     In addition, the locking protection mechanism  10  further includes an upper housing  108  which is pressed and detachably connected to the first lower housing  101 . The upper housing  108  can fix and protect the locking pin  102 , the driving pin  103 , etc. The upper housing  108  has a fourth holding cavity  1081 , a first sensor  1082  is arranged in the fourth holding cavity  1081 , and a second electromagnetic induction component  1026  is arranged on the executive part  1021 . Wherein, the first sensor  1082  acts on the second electromagnetic induction component  1026  to detect that the executive part  1021  is in an extended state. The fourth holding cavity  1081  is further provided with a second sensor  1083 , the second sensor  1083  acts on the second electromagnetic induction component  1026  to detect that the executive part  1021  is in a retracted state. Compared with the first sensor  1082 , the second sensor  1083  is closer to the driving pin  103 . Through the first sensor  1082 , the second sensor  1083  and the second electromagnetic induction component  1026  can reliably detect when the locking pin  102  is in the extended state and the retracted state, which is conducive to the unlocking and locking of the battery pack by the primary lock mechanism  20 . In addition, in the present embodiment, the first electromagnetic induction component  104  and the second electromagnetic induction component  1026  are both magnetic steel. 
     In addition, in the present embodiment, the locking protection mechanism  10  adopts the method of electromagnetic attraction of the driving pin  103  to realize the extension and retraction of the locking pin  102 , and the extension and retraction of the locking pin  102  are in the same linear direction. In other alternative embodiments, the extension and retraction of the locking pin  102  can be realized by other driving modes (non electromagnetic driving modes), the action path of the locking pin  102  can also be set as a curve, and other non locking pin  102  structures, such as crank mechanism and rocker mechanism, can be adopted to realize the switch between the first position and the second position of the locking protection mechanism. 
     Understand with reference to  FIG.  11    and  FIG.  19   , the power transfer device further includes a plurality of support structures  40 . The plurality of support structures  40  are fixed on one side of the battery pack holder  60  facing the battery pack, and the plurality of support structures  40  are used to provide a plurality of support points for supporting the battery pack. Specifically, the support structure  40  includes a supporting base  401 , the supporting base  401  provided with a supporting base  401  and a supporting groove  403  extending from the supporting opening  402 , the supporting opening  402  is used for a support part installed on the battery pack to enter the supporting groove  403 . The plurality of support structures  40  are distributed on both sides of the battery pack holder  60  in the length direction of the battery pack holder  60 , and the support structures  40  arranged on both sides of the battery pack holder  60  are one-to-one corresponding and relatively arranged. Both sides of the battery pack holder  60  in the length direction of the battery pack holder  60  are provided with a lock mechanism, and the support structure  40  and the lock mechanism on the same side are interval set. The support structure  40  can support the battery pack, facilitate the installation of the battery pack and the battery pack holder  60 , and improve the locking effect of the lock mechanism, so as to improve the power exchange reliability of the electric vehicle. 
     In addition, in the present embodiment, the battery pack holder  60  in  FIG.  10    is further provided with a power exchange sensor (not shown in the figure), which is used to sense the power transfer equipment and to control the disconnection of the electrical connection between the electrical connector of the vehicle side  50  and the electrical connector of the battery side. When the battery pack is removed from the battery pack holder  60  by the power transfer equipment, the power exchange sensor can disconnect the electric connection between the electrical connector of the vehicle side  50  and the electrical connector of the battery side, so as to protect the electric vehicle. 
     The embodiment further discloses an installation method of a power transfer device, which comprises the following steps: 
     Step 1, install the battery pack from the bottom of the battery pack holder along the height direction of the battery pack into the battery pack holder until the locking shaft rises in place in the lock mechanism along the height direction of the battery pack; 
     Step 2, move the battery pack forward along its length direction until the locking shaft reaches the locking point in the lock mechanism along the length direction of the battery pack. 
     According to the power transfer device in the present embodiment, when the locking shaft of the battery pack is locked in place in the lock mechanism, the electrical connector of the battery side can be reliably connected with the electrical connector of the vehicle side, so as to improve the reliability and power exchange efficiency of the electric vehicle using the power transfer device. 
     Although the specific embodiments of the invention have been described above, those skilled in the art will understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principle and essence of the invention. Therefore, the scope of protection of the invention is defined by the appended claims.