JP2012131406A - Rear suspension for truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear suspension for a truck capable of achieving early detection of leaf spring breakage while allowing for detection of leaf spring breakage with a simple configuration.SOLUTION: In a rear suspension 20 for a truck wherein an axle 13 is elastically supported to a vehicle body frame 11 through a leaf spring 45, the leaf spring 45 includes a main spring 23 with both ends thereof supported to the vehicle body frame 11 and a helper spring 26 for receiving a load when the main spring 23 is deflected under load by a predetermined amount, and the helper spring 26 is supported so as to be able to touch or get spaced apart from helper brackets 27, 27 provided on the vehicle body, the helper bracket 27 is provided with a piezoelectric element 68 for detecting load when pressed by the helper spring 26.

Description

  The present invention relates to an improvement in a truck rear suspension.

  As a conventional rear suspension for trucks, one that performs load weight measurement using a load conversion element is known (for example, see Patent Document 1).

  According to FIG. 1 of Patent Document 1, both ends of a leaf spring 4 as a spring member constituting the suspension device 3 are attached to a vehicle body frame (not shown), and the axle 2 is attached to the leaf spring 4 with a connecting bracket 5. ing.

  According to FIGS. 3 (A) and 3 (B) of Patent Document 1, a mounting plate 11 is attached to the connection fitting 5 along the lower surface of the leaf spring 4. Between these, a piezoelectric element 12 as a load converting element is provided.

  When the load is loaded on the truck bed, as shown in FIG. 3B of Patent Document 1, the central portion of the leaf spring 4 bends upward, and accordingly, the attachment plate 11 and the lower surface of the leaf spring 4 The compressive load acting on the piezoelectric element 12 during the period increases, and a voltage corresponding to the compressive load is output.

JP-A-9-290680

With the piezoelectric element 12 of Patent Document 1, for example, it is possible to detect breakage of the leaf spring 4 when an overload acts on the leaf spring 4 from the axle side.
If the leaf spring 4 breaks, the load received by the leaf spring 4 changes, and this is detected as a change in the output voltage of the piezoelectric element 12.

  As a conventional truck rear suspension, as shown in FIG. 6 of the present specification, a leaf spring composed of a main spring and a helper spring is known.

  In FIG. 6, the leaf spring 100 includes a main spring 102 that supports the axle 101 and a helper spring 103 that is integrally attached to the upper portion of the main spring 102. Reference numeral 110 denotes a vehicle body frame, and 111 denotes a wheel attached to the axle 101.

  When the main spring 102 receives a larger upward load from the axle 101 side and moves upward, the helper spring 103 also moves together. The helper spring 103 has a helper bracket 105 with both ends attached to the vehicle body side, 106. As a result, the spring constant of the leaf spring 100 as a whole increases, and a larger load can be supported.

Similarly, when the piezoelectric element 12 of Patent Document 1 described above is provided on the main spring 102, breakage of the main spring 102 can be detected by the piezoelectric element 12.
However, in the technology in which the piezoelectric element as described above is provided on the leaf spring, the leaf spring always vibrates up and down while the truck is running, so that the piezoelectric element does not fall off due to this vibration or displacement. It is necessary to more firmly attach to the leaf spring side with a fastening member or the like. Further, the mounting is not easy, such as using a mounting plate for mounting the piezoelectric element, or welding the mounting plate to the coupling metal, and the cost increases.

  Furthermore, in the technique of Patent Document 1, if the leaf spring breaks, there is a high possibility that it will not be able to run immediately. However, in the conventional technique shown in FIG. It is conceivable that the voltage change at the piezoelectric element 12 provided on the main spring 102 side does not appear due to being caught by the helper brackets 105 and 106. In this case, traveling is continued with the main spring 102 broken, and it may be impossible to travel during the traveling.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a truck rear suspension that can detect a breakage of a leaf spring with a simple configuration and can detect the breakage of the leaf spring at an early stage.

  According to the present invention, the axle is elastically supported on the vehicle body frame via the leaf spring, and the leaf spring is bent by a predetermined amount when the main spring receives the load and the main spring is supported at both ends by the vehicle body frame. It is composed of a helper spring that receives a load at the time, and this helper spring is pressed against the helper bracket by the helper bracket in a truck rear suspension that is supported so as to be in contact with or separated from the helper bracket provided on the vehicle body. A truck rear suspension provided with a load detecting element for detecting a load is provided.

  When the main spring receives a load from the loading platform or the like and bends upward by a predetermined amount, the helper spring moves upward along with this, and the helper spring hits the helper bracket and receives the load from the loading platform or the like. As a result, a detection signal corresponding to the load is generated in the load detection element.

  For example, if the main spring breaks due to an overload acting on the main spring, the load from the loading platform etc. is received only by the helper spring and transmitted to the axle, and the load before the main spring breaks on the helper bracket side A larger load is applied. Therefore, since a detection signal is generated in the load conversion element due to the load change, it is possible to quickly detect the breakage of the main spring.

  Since the load detection element is provided on a helper bracket provided on the vehicle body side, that is, a leaf spring is interposed between the axle side and the vehicle body side, so that vibration transmitted from the axle side to the vehicle body side is attenuated, and even during traveling Since the part where the helper bracket is attached is a part where vibration and displacement are smaller than the axle and leaf spring itself, the mounting structure of the load detection element to the helper bracket can be simplified and the cost can be reduced. Can be reduced.

In the truck rear suspension of the present invention, the load detection element is preferably a piezoelectric element that generates power by being pressed by a helper spring.
The load change is detected as a voltage change signal by the piezoelectric element. Further, since the load detection element is a piezoelectric element that generates power by being pressed by a helper spring, a voltage change can be taken out as a detection signal without requiring an external power source.

Further, preferably, the piezoelectric element is embedded in a rubber attached at a position of contact with the helper spring in the helper bracket.
Since the piezoelectric element is covered and protected with rubber, there is no fear that the piezoelectric element will be exposed to dirt, rainwater, etc., or a stepping stone will hit the piezoelectric element, and deterioration against environmental changes is reduced.

In the rear suspension for a truck according to the present invention, the helper bracket is provided with a load detection element that detects the load by being pressed by the helper spring. Therefore, when the main spring breaks, the load detection element provided on the helper bracket The breakage of the main spring can be quickly detected immediately after that.
As a result, the breakage of the main spring can be detected at an early stage, and the inoperable state can be avoided by the helper spring.

  In addition, since the load detection element is provided on the helper bracket on the vehicle body side, the vibration and displacement are small compared to the axle and leaf spring itself, so the structure for mounting the load detection element to the helper bracket is simplified. And cost can be reduced.

1 is a side view showing a truck rear suspension according to the present invention. It is a perspective view which shows the helper bracket and detection body which concern on this invention. It is an operation view showing an operation of a truck rear suspension according to the present invention. It is a graph which shows the generated voltage characteristic of the piezoelectric element which concerns on this invention. It is a flowchart which shows the leaf spring breakage detection method which concerns on this invention. It is a side view which shows the rear suspension for the conventional trucks.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  As shown in FIG. 1, a truck rear suspension 20 for suspending a truck wheel 10 includes a front bracket 21 and a rear bracket assembly 22 attached to a vehicle body frame 11 of the truck, and the front bracket 21 and the rear bracket assembly. A main spring 23 composed of a leaf spring connected to a solid body 22, a helper spring 26 integrally attached to the upper portion of the main spring 23 by a fastening member 25, and a helper spring 26 when the helper spring 26 moves upward. 26 includes a pair of helper brackets 27 and 27 for restricting upward movement of both end portions of 26 and a breakage detecting device 32 for detecting breakage of the main spring 23.

The fastening member 25 includes a pair of U bolts 24, 24 hung on the main spring 23 and the helper spring 26, an axle housing support member 31 that supports the axle housing 14 and passes the U bolts 24, 24, and a U bolt And nuts 33 screwed into the respective tips of 24 and 24.
An axle 13 is rotatably housed inside the axle housing 14, hubs (not shown) are attached to both ends of the axle 13, and wheels 10 are attached to these hubs.

  The front bracket 21 is attached to the side surface of the body frame 11 with a plurality of bolts, and a front end portion 23a of the main spring 23 (a part that is wound and formed in a cylindrical shape) on a front support shaft 35 provided at the lower end portion of the front bracket 21. ) Are pivotably connected.

  The rear bracket assembly 22 has a rear bracket body 37 attached to a side surface of the vehicle body frame 11 with a plurality of bolts, and a rear support shaft 38 provided at the center of the rear bracket body 37 so that an upper end portion thereof is swingable. The link member 42 is connected to a lower pin 41 provided at the lower end portion and a rear end portion 23b of the main spring 23 is swingably connected.

  Each of the main spring 23 and the helper spring 26 is a member in which a plurality of steel plate springs are overlapped, and is set to a predetermined spring constant. The main spring 23 and the helper spring 26 constitute a leaf spring 45. It is a member.

  Such a two-stage leaf spring 45 is used to cope with a load that fluctuates greatly when there is no load on the loading platform and when the loading is loaded on the loading platform. 23 and only the main spring 23 and the helper spring 26 act to support the load under heavy load.

The helper bracket 27 is provided with a piezoelectric element at a portion that contacts the helper spring 26 (detector 62 described later in detail).
The piezoelectric element is compressed and generates electric power when the helper spring 26 hits the helper bracket 27.

The breakage detection device 32 includes a piezoelectric element, a controller 51, and a caution lamp 52. The controller 51 lights or blinks a caution lamp 52 provided near the driver's seat of the truck, for example, based on a voltage generated by power generation of the piezoelectric element. It is the control means to make.
If the caution lamp 52 is lit or flashing, the truck driver can notice that the main spring 23 is broken and can immediately stop the truck.

As shown in FIG. 2A, the helper bracket 27 includes a bracket body 61 and a detection body 62 attached to the bracket body 61.
The bracket body 61 includes a base plate 64 attached to the vehicle body frame 11 (see FIG. 1) and a side protrusion member 65 having a U-shaped cross section attached to the upper side of the base plate 64. A detection body 62 is attached to the lower surface of the member 65.
Here, a plurality of symbols 64a are bolt insertion holes through which the bolts for attaching the helper bracket 27 to the vehicle body frame 11 are passed, and 64b is a reinforcing rib provided vertically at the center of the base plate 64 for reinforcement.

  The side projecting member 65 includes a bottom wall 65a and a pair of opposing side walls 65b and 65c bent from the bottom wall 65a, and includes two bolt insertion holes (for mounting the detector 62 on the bottom wall 65a). (Not shown) is opened.

  As shown in FIG. 2B, the detection body 62 includes a flat upper plate 67, a rubber 71 attached to the lower surface of the upper plate 67, a piezoelectric element 68 embedded in the rubber 71, It consists of a pair of bolts 72, 72 attached to the upper surface of the upper plate 67.

  Since the piezoelectric element 68 is embedded in the rubber 71, the piezoelectric element 68 can be protected by the rubber 71, and there is no fear that the piezoelectric element 68 is exposed to dirt, rain water, or the like, or the stepping stone hits the piezoelectric element 68.

  The bolts 72 and 72 are respectively inserted into the bolt insertion holes of the bottom wall 65a described with reference to FIG. 2A, and nuts 73 are screwed into the ends of the bolts 72 and 72, so that the detection body 62 is placed on the bottom wall 65a. Mounted.

Next, the operation of the truck rear suspension 20 described above will be described.
When a heavy load is applied to the truck bed from the state shown in FIG. 1, the axle 13 is moved upward relative to the body frame 11 as shown by the white arrow as shown in FIG. The center portion bends upward, the helper spring 26 moves upward, and both end portions of the helper spring 26 hit the helper bracket 27.
As a result, both the main spring 23 and the helper spring 26 act on the heavy load, and the spring constant of the entire leaf spring 45 is increased to support the heavy load.

Changes in the voltage generated by the piezoelectric elements incorporated in the helper brackets 27 and 27 at this time are shown in FIG.
The vertical axis in FIG. 4 represents the voltage V generated by the piezoelectric element, and the horizontal axis represents time T.
From time T = 0 to time T1, the load is light, and only the main spring is acting. The generated voltage at this time is V = 0.

  Between the time T1 and the time T2, it is a heavy load state, and both the main spring 23 and the helper spring 26 as shown in FIG. 3 are acting. The generated voltage V at this time fluctuates due to transmission of vibration or the like from the road surface. An average voltage of the generated voltage V at this time is V1.

  For example, when the main spring of the running truck breaks at time T2, since most of the load is received by the helper spring, the pressing load by which the helper spring presses the piezoelectric element is further increased. The generation voltage V of V is increased to an average voltage V2. This average voltage V2 exceeds the generated voltage threshold value V3 for lighting or blinking the caution lamp, and the duration Tc in the state where the average voltage V2 exceeds the generated voltage threshold value V3 When it becomes longer than the threshold value δ, the caution lamp lights up or flashes to inform the driver that the main spring is broken.

A method for detecting breakage of the main spring will be described with reference to the flowchart of FIG. S1, S2,... Indicate step numbers.
In step S1, it is determined whether the helper spring is in contact with the helper bracket.
If the helper spring does not contact (NO), the process proceeds to step S1 again.
If the helper spring contacts (YES), the process proceeds to step S2.

In step S2, the piezoelectric element generates power.
In step S3, it is determined whether the generated voltage V is greater than the generated voltage threshold Vst.
If V ≦ Vst (NO), the process proceeds again to step S2.
If V> Vst (YES), the process proceeds to step S4.

In step S4, the timer is turned on. At this time, the duration of V> Vst is Tc = 0.
In step S5, it is determined whether or not the duration time Tc is greater than the time threshold value Tst.
If Tc ≦ Tst (NO), the process proceeds again to step S2.
If Tc> Tst (YES), the process proceeds to step S6.
In step S6, the caution lamp is turned on or blinked.

  As shown in FIGS. 1 and 3 to 5, in the present invention, the axle 13 is elastically supported on the vehicle body frame 11 via the leaf spring 45, and the leaf spring 45 is attached to the vehicle body frame 11 at both ends. The main spring 23 is supported and a helper spring 26 that receives a load when the main spring 23 receives a load from a loading platform or the like and bends a predetermined amount. The helper bracket 26 is provided on the vehicle body. In the track rear suspension 20 supported so as to be able to contact or be separated from the 27, 27, the helper bracket 27 is provided with a piezoelectric element 68 as a load detecting element that is pressed by the helper spring 26 and detects a load.

  Preferably, the load detection element is a piezoelectric element 68 that generates power by being pressed by the helper spring 26, and the piezoelectric element 68 is embedded in a rubber 71 that is attached to the helper bracket 27 at a position in contact with the helper spring 26. Yes.

  As described above, the helper bracket 27 is provided with the piezoelectric element 68 that is pressed by the helper spring 26 to detect the load. Therefore, when the main spring 23 breaks, the piezoelectric element 68 breaks the main spring 23. It can be detected immediately after that. Accordingly, the breakage of the main spring 23 can be detected at an early stage, and the state in which the truck cannot travel can be avoided.

  Further, since the piezoelectric element 68 is provided on the helper bracket 27 on the vehicle body frame 11 side, that is, the portion to which the helper bracket 27 is attached even during traveling has vibration and displacement compared to the axle housing 14 and the leaf spring 45. By being provided in a small part, the attachment of the piezoelectric element 68 can be made a simple structure, and the cost can be reduced.

  Further, since the piezoelectric element 68 can detect that the helper spring 26 hits the helper bracket 27, it is possible to quantitatively grasp the load on the rear suspension 20 due to the vehicle load, and adjust the vehicle load. Can be easily performed. As a result, overloading can be prevented, and deterioration of fuel consumption due to overloading can be prevented.

Since the piezoelectric element 68 generates power by a compressive load, it can output a voltage change as a detection signal without the need for an external power supply, and this can also reduce the cost for detecting breakage of the main spring 23. .
Further, since the pair of piezoelectric elements 68 and 68 are used in the truck rear suspension 20, the reliability of detection of breakage of the main spring 26 can be improved.

  In the present invention, a piezoelectric element is used as the load conversion element. However, the present invention is not limited to this, and for example, a resistance element such as a strain gauge is attached to the side protrusion member 65 shown in FIG. May be used.

  The piezoelectric element of the present invention is basically an element in which a piezoelectric body is sandwiched between two electrodes, and utilizes the piezoelectric effect that converts a force applied to the piezoelectric body into a voltage or converts a voltage into a force. Passive element.

As the piezoelectric body, quartz (SiO ₂ ), zinc oxide (ZnO), Rochelle salt (potassium tartrate-sodium) (KNaC ₄ H ₄ O ₆ ), lead zirconate titanate (PZT: Pb (Zr, Ti) O ₃ ), Lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), langasite (La ₃ Ga ₅ SiO ₁₄ ), aluminum nitride, tourmaline (tourmaline), Polyvinylidene fluoride (PVDF) is preferred.

  Further, in the embodiment shown in FIG. 2B, the rubber 71 in which the piezoelectric element 68 is embedded is attached to the lower surface of the upper plate 67. However, the present invention is not limited to this, and the piezoelectric element 68 is attached to the lower surface of the upper plate 67. The rubber 71 may be attached to the lower surface of the upper plate 67 so as to cover the piezoelectric element 68.

  The present invention is suitable for a rear suspension including a leaf spring.

DESCRIPTION OF SYMBOLS 11 Body frame 13 Axle 20 Rear suspension 23 for trucks Main spring 26 Helper spring 27 Helper bracket 32 Breakage detecting device 45 Leaf spring 62 Detector 68 Load detecting element (piezoelectric element)
71 Rubber

Claims (3)

When the axle is elastically supported on the body frame via a leaf spring, the leaf spring is supported by a main spring supported at both ends on the body frame side, and the main spring receives a load and is bent by a predetermined amount. In a rear suspension for a truck, which is configured of a helper spring that receives the load, and the helper spring is supported so as to be in contact with or separated from a helper bracket provided on the vehicle body frame,
A truck rear suspension, wherein the helper bracket is provided with a load detection element that is pressed by the helper spring to detect the load.   The truck rear suspension according to claim 1, wherein the load detection element is a piezoelectric element that generates power by being pressed by the helper spring.   3. The truck rear suspension according to claim 2, wherein the piezoelectric element is embedded in a rubber attached to the helper bracket at a position where the helper spring contacts the helper spring.

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