Abstract:
An assembly for mounting a sensor, which measures a running state of a vehicle, on the vehicle at a predetermined positional relationship to the vehicle. The assembly includes a control unit for controlling the vehicle based on a signal transmitted from the sensor and a circuit board. The assembly further includes a case to be fixed to the vehicle for housing the circuit board and a holding member for holding the sensor at an inclination relative to the circuit board. The holding member maintains the positional relationship between the sensor and the vehicle when the case is fixed to the vehicle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sensor, and more particularly to a mounting structure for a sensor that measures the running state of an industrial vehicle, such as a fork-lift truck. 
     2. Description of the Prior Art 
     Prior art fork-lift trucks have tiltable axles for improving riding quality and running stability. However, when a load on the fork is relatively heavy, when the vertical position of the load on the fork is relatively high, or when the fork-lift truck makes a high speed turn, the running stability of the fork-lift truck is decreased due to tilting motion of the axle. An apparatus for locking the axle to prevent the tilting motion of the axle relative to the body frame in these situations has been proposed. The apparatus includes a sensor for measuring the yaw rate or lateral acceleration (centrifugal force) of the vehicle. The apparatus further includes a lock mechanism for locking the tilting motion of the axle when the yaw rate or the lateral acceleration exceeds a predetermined value. 
     For example, the yaw rate sensor utilizes a piezoelectric vibrational gyroscope or a fiber-optic gyroscope. When the measured yaw rate or the lateral acceleration, which is calculated based on the measured yaw rate and the speed of the fork-lift truck, exceeds a predetermined value, the lock mechanism will be activated. The lock mechanism has dampers that are arranged between the body frame and the axle. When the dampers are locked, tilting of the axle is prohibited. As a result, the vehicle is stabilized. 
     In general, accuracy of the sensor is affected by the way the sensor is mounted. If the sensor is improperly mounted on the vehicle, the accuracy of the sensor will be low. In the case of a yaw rate sensor having a gyroscope, the axis of the gyroscope must be parallel to the vehicle&#39;s turning axis, which is vertical. That is, the axis of the sensor should be vertically fixed on the vehicle. In a case of the acceleration sensor, the direction of the acceleration to be measured should be parallel to the moving direction of the vehicle. 
     However, it is sometimes difficult to provide enough space for mounting the sensor, so the sensor is not always properly mounted. Moreover, typically, such sensors are not water-proof and dust-proof. Therefore, the additional space required for a water and dust proof structure would further limit the available mounting space. 
     One way to mount the sensor on the vehicle is to mount the sensor directly on the vehicle body. In this proposal, the sensor is covered by a water and dust proof cover, and a control unit is accommodated in a water and dust proof metal case. The control unit has an electric circuit for controlling the tilting motion of the axle. The sensor, which is mounted on the vehicle body, is electrically connected to the control unit, which is separated from the sensor, with a wire harness. 
     In this proposal, the sensor unit is relatively small, so that the attitude and position of the sensor unit on the vehicle are not substantially restricted. Therefore, the sensor can be mounted on the vehicle even if the mounting space is small. Furthermore, the axis of the sensor can be vertically fixed. However, since the harness that connects the sensor and the control unit is positioned outside of the cases, the harness is easily cut, so the electrical connection is unreliable. 
     Another way to mount the sensor on the vehicle is to put both the sensor and the control unit in a common case. In this instance, as shown in FIG. 6, a circuit board  41 , which has an electric circuit on it, is housed in the case  40  of the control unit. The sensor  42  is directly mounted on the board  41 . A terminal  43  is provided on the sensor  42 . The terminal  43  is soldered to an electrode (not shown) of the board  41 . The sensor  42  is thus electrically connected to the control unit. 
     In this instance, the sensor  42  is directly mounted on the board  41 , so the electrical connection is not exposed. However, the case  40  is relatively large, so the attitude and the location of the sensor  42  on the vehicle is restricted. Therefore, the operational axis of the sensor  42  may not be perfectly vertical when the sensor  42  is mounted on the vehicle. 
     Furthermore, the sensor  42  is relatively heavy in comparison with other circuitry parts, so the solder, which connects the terminal  43  and the electrode of the board, is susceptible to breakage due to vibrations. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an improved support assembly for a sensor that measures a running state of a vehicle. 
     Another objective of the present invention is to provide a sensor support assembly that achieves a more reliable electrical connection between the sensor and a circuit board. 
     Another objective is to provide a sensor support assembly that uses existing parts, thus reducing costs. 
     For achieving the objectives of the present invention, an assembly is provided for mounting a sensor that measures a running state of a vehicle on the vehicle. The sensor is mounted with a predetermined orientation. The assembly includes a control unit for controlling the vehicle based on a measured signal transmitted from the sensor. The control unit includes a circuit board. The assembly further includes a case to be fixed to the vehicle for housing the circuit board and a holding member for holding the sensor at an angle relative to the circuit board. The holding member maintains the orientation of the sensor with respect to the vehicle when the case is fixed to the vehicle. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objectives and advantages thereof, may best be understood by reference to the following description of the present preferred embodiments together with the accompanying drawings in which: 
     FIG. 1 is a longitudinal cross sectional view of a sensor mounting assembly in accordance with the present invention; 
     FIG. 2 is a cross-sectional view of the assembly of FIG. 1; 
     FIG.  3 ( a ) is a plan view of a bracket; 
     FIG.  3 ( b ) is a side view of the bracket of FIG.  3 ( a ); 
     FIG. 4 is a cross-sectional view like FIG. 1 of the assembly mounted on the vehicle; 
     FIG.  5 ( a ) is a longitudinal sectional view, showing another embodiment of the sensor mounting assembly; 
     FIG.  5 ( b ) is a longitudinal sectional view, showing further embodiment of the sensor mounting assembly; and 
     FIG. 6 is a longitudinal sectional view of a prior art sensor mounting structure. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described with reference to FIGS. 1 to  4 . 
     As shown in FIG. 1, a sensor mounting assembly  1  is protected by a water and dust proof case  2 . The case  2  is formed by, for example, aluminum alloy and is fixed to a vehicle. The case  2  includes a base  3 , which is fixed to the vehicle, and a cover  4 , which is fixed to the base  3 . An inner surface of the cover  4  and a recess  3   a  of the base  3  define a sensor accommodating space. First pedestals  5  and second pedestals  6  extend from the recess  3   a  and are integrally formed with the base  3 . The first and second pedestals  5  and  6  have the same length. Furthermore, the first and second pedestals  5  and  6  have a female threaded hole (not shown) at their distal ends for attaching a circuit board  8  to the pedestals  5  and  6 . The circuit board  8  is fixed to each of the first and second pedestals  5  and  6  by screws  7 ,  19  and  22 . 
     As shown in FIG. 2, the circuit board  8  includes first and second parts  9  and  10 . The first part  9  is supported on the first pedestals  5 . The first part  9  is preferably an existing circuit board, which was used in the prior art. The second part  10  is supported on the second pedestals  6  adjacent to the first part  9 . An electric circuit is provided on the first part  9 . The electric circuit controls a lock mechanism for locking the tilting motion of an axle of the vehicle. A connector  11  for electrically connecting the electric circuit to the lock mechanism is provided on the first part  9 . The second part  10  provides an area for mounting a sensor  13 . The sensor  13  is mounted on the second part  10  with a bracket  12  and spacers  20  and  23 . 
     The bracket  12  is formed by press molding a metal plate. As shown in FIGS.  3 ( a ) and  3 ( b ), the bracket  12  is bent. A plate  14  of the bracket  12  supports the sensor  13  on its top surface  14   a . Two holes  17  extend through the plate  14  for mounting the sensor  13  on the top surface  14   a  of the plate  14 . Two first mounting pieces  15  and one second mounting piece  16  are formed on the bracket  12  to fix the bracket  12  to the second part  10 . The first and second mounting pieces  15  and  16  are planar. The first mounting pieces  15  extend from first end of the plate  14  at a predetermined angle relative to the plate  14 . The first mounting pieces  15  are parallel with each other. The second mounting piece  16  extends from a second end, which is opposite to the first end, of the plate  14  at an equal but opposite angle to that of the first mounting pieces  15  relative to the plate  14  as shown in FIG.  3 ( b ). The mounting piece  16  extends in a direction that is opposite to that of the first mounting pieces  15 . Therefore, each first mounting piece  15  is parallel to and offset from the second mounting piece  16 . The first mounting pieces  15  and the second mounting piece  16  are separated by the plate  14 . 
     A through hole  18  is formed in each first mounting piece  15 . A screw  19  is inserted through each hole  18 , through a spacer  20  and through a hole in the second part  10 . Each screw  19  is then screwed into the threaded hole of the corresponding second pedestal  6 . Through holes  21  are formed in the second mounting piece  16 . A screw  22  is inserted through each hole  21 , through a spacer  23 , and through a hole in the second part  10 . Each screw  22  is then screwed into the threaded hole of the corresponding second pedestal  6 . Therefore, the plate  14  is fixed to the circuit board  8  while the top surface  14   a  of the plate  14  is inclined relative to the second part  10  at a predetermined angle. 
     The sensor  13  has a main body  24  and mounting ears  25 , which are formed on opposite sides of the main body  24 . A threaded hole  25   a  is formed in each mounting ear  25 . A screw  26  is inserted through each hole  17  from the rear surface  14   b  of the plate  14  to engage with the corresponding threaded hole  25   a  of the mounting ear  25 . The sensor  13  is thus fixed to the bracket  12 . An arrow S shown in FIG. 1 indicates the direction of an operational axis, which is defined in the sensor  13 . The sensor  13  measures the yaw rate based on a deflection from the operational axis. The operational axis extends parallel to the top surface  14   a  and is inclined relative to the rear surface of the base  3 . 
     Lead wires  27  are connected to an input/output terminal (not shown) of the sensor  13 . The connection between the input/output terminal of the sensor  13  and the lead wire  27  is sealed by synthetic resin. The lead wire  27  has a connector  28  at its distal end. The connector  28  is connected to a socket provided on the first part  9 . As a result, the sensor  13  is electrically connected to the electric circuit arranged on the first part  9 . 
     The cover  4 , shown in FIGS. 1 and 2, is fixed to the base  3 . The cover  4  has an opening  4   a . The connector  11  is accessible from outside of the case  2  through the opening  4   a . The opening  4   a  allows wires to extend between the connector  11  and an axle tilt control mechanism located outside of the assembly  1 . 
     In the first embodiment, the assembly  1  is fixed to the vehicle body while the top surface  14   a  of the assembly  1  is inclined at the predetermined angle, as shown in FIG.  4 . In this position, the operational axis of the sensor  13  is vertical (assuming the vehicle is level). 
     Functions and operation of the mounting structure of the sensor will now be described. 
     For example, as shown in FIG. 4, the assembly  1  can be fixed to a rear surface Pb of a front protector P of the. fork-lift truck. The rear surface Pb is inclined. The slope of the top surface  14   a  of the bracket  12  is defined based on the inclination of the rear surface Pb. When the assembly  1  is fixed to the rear surface Pb, the top surface  14   a  is vertical, and thus the axis of the sensor  13  is also vertical. Therefore, the sensor  13  can accurately measure the yaw rate of the vehicle while the vehicle is making a turn. The assembly  1  transmits a control signal to control the tilting motion of the axle based on the measured yaw rate. The lock mechanism is operated based on the control signal. Therefore, the tilting motion of the fork-lift truck is adequately controlled. 
     The mounting structure of the sensor in the vehicle in accordance with this embodiment provides following advantages. 
     (a) The sensor  13  is fixed to the case  2  with the second part  10 , the bracket  12  and the spacers  21  and  23 . These parts hold the sensor  13  at desired mounting attitude. Thus, the sensor  13  is fixed to the vehicle at the desired attitude. 
     (b) The first and second parts  9  and  10  are arranged on the circuit board  8 . The sensor  13  is fixed to the second part  10  by the bracket  12  and the spacers  21  and  23 . Therefore, the case  2  can be made thinner. As a result, there are fewer limitations on the mounting location. 
     (c) The bracket  12  is made with a simple metal plate, so the bracket  12  can be easily manufactured, for example, by press molding. 
     (d) Since the assembly  1  of the preferred embodiment incorporates a pre-existing circuit board part  9 , the cost of the assembly  1  is lower than if a new circuit board were designed. 
     (e) The present invention relates to the mounting structure of the sensor  13 , which measures the yaw rate while the vehicle is making a turn, so the yaw rate is measured accurately. The mounting structure is part of the apparatus for locking the axle of the fork-lift truck, so the axle of the fork-lift truck is controlled with high accuracy. 
     The present invention is not limited to the above embodiment of FIG.  1  and can be modified as follows. 
     The bracket  12  may be replaced with a bracket  30 , which has a V shaped cross section as shown in FIG.  5 ( a ). In this instance, the spacers  21  and  23  are not required, so the numbers of the parts and the manufacturing steps are reduced. In this embodiment, planar mounting pieces  15   a  and  16   a  lie in the same plane. 
     The bracket  12  or  30  need not be manufactured by press molding a metal plate. The bracket  12  or  30  can be manufactured by other means. 
     As shown in FIG.  5 ( b ), a bracket  31  having a triangular prism shape, which is produced by metal casting or metal forging, may be employed. In this instance, the spacers  21  and  23  are not required, so the numbers of the parts and manufacturing steps are reduced. 
     The bracket  12 ,  30 ,  31  can be manufactured from other than metal materials, such as synthetic resin or ceramics. 
     The bracket  12  can have a mechanism for changing the inclination of the sensor mounting surface of the bracket  12  relative to the case  2 . In this instance, the sensor  13  can be held by the same bracket  12  even if the mounting position of the case  2  on the vehicle is changed. 
     The first and second parts  9  and  10  can be integrated in the same board. That is, there may be only one circuit board. 
     The lead wire  27  can be soldered to the electrode terminal on the first part  9  instead of the input/output terminal of the sensor. Even in this construction, the possibility of cutting the wire is reduced, and the reliability of the connection is increased, since large forces caused by vibration of the sensor  13  are not applied to the soldered part. 
     The input/output terminal can be integrally formed on the sensor  13 , and the input/output terminal can be soldered to the second part  10 . 
     The present invention is not limited to the mounting structure of the sensor  13 , which measures the yaw rate. For example, the present invention can be applied to a mounting structure of an acceleration sensor, which measures the acceleration of the vehicle in the moving direction of the vehicle. A control apparatus controls the braking force or the engine speed based on the speed calculated from the measured acceleration. 
     The present invention is not limited to fork-lift trucks. The present invention can be applied to a mounting structure of a sensor  13  that measures the yaw rate of, for example, a shovel loader or a vehicle for high lift work. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.