JP2015206591A - Vehicular weight estimation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in estimating a spring-burden load exerted to an air-spring.SOLUTION: An ascent-descent control part 20 executes ascent processing for lifting a structural body so that a vehicle height detected by a vehicle height sensor 13 reaches a reference vehicle height from below the aforementioned height, and descent processing for lowering the structural body so that a vehicle height detected by a vehicle height sensor 13 reaches the reference vehicle height from above the aforementioned height. A basic load computation part 19 computes a spring-burden basic load in an ascending direction by using basic load computation information and internal pressure detected by a pressure sensor 14 in the state of the structural body reaching the reference vehicle height by the ascent processing, and computes a spring-burden basic load in a descending direction by using basic load computation information and internal pressure detected by the pressure sensor 14 in the state of the structural body reaching the reference vehicle height by the descent processing. A spring-burden load computation part 23 calculates an average value of the spring-burden basic load in the ascending direction and the spring-burden basic load in the descending direction as a spring-burden load exerted to an air-spring.

Description

  The present invention relates to a vehicle weight estimation device in which a structure is elastically supported by an air spring so as to be movable up and down.

  Patent Document 1 discloses that the load-internal pressure characteristic of an air spring is represented by a linear approximation formula, and the load on the air spring can be calculated by substituting the measured internal pressure of the air spring into the linear approximation formula. . Patent Document 1 describes a method for correcting a design load-internal pressure characteristic according to the actual properties of an air spring.

JP 2011-240792 A

  The relationship between the internal pressure of the air spring (air spring) and the spring load (load on the air spring) is when the air spring is extended (when the structure supported by the air spring is raised) and when it is shortened (when the structure is lowered) Case). In other words, in the actual load-internal pressure characteristics, there is hysteresis when the air spring is extended and shortened (when the structure is raised and lowered), and the structure is raised to any one vertical position. The internal pressure of the air spring is different between the case and the case where the air spring is lowered.

  For this reason, the load calculated from the linear approximation formula as in Patent Document 1 includes an error due to hysteresis of the air spring, and it is difficult to improve the estimation accuracy of the spring load.

  In view of the above, an object of the present invention is to provide a vehicle weight estimation device capable of improving the accuracy of estimation of a spring-borne load borne by an air spring.

  In order to achieve the above object, the present invention is a weight estimation device mounted on a vehicle, comprising an internal pressure detection means, a vertical displacement detection means, a basic load calculation information storage means, a lift control means, a basic load calculation. Means and a spring load calculation means. The structure is elastically supported from below by an air spring, and moves up and down by expansion and contraction of the air spring by supplying and discharging compressed air.

  The internal pressure detecting means detects the internal pressure of the air spring. The vertical displacement detection means detects the height of the structure with respect to a predetermined reference height as the vertical displacement. The basic load calculation information storage means stores in advance a correspondence relationship between an arbitrary internal pressure of the air spring and a spring load basic load as basic load calculation information.

  The raising / lowering control means performs an ascending process and a descending process. In the ascending process, the elevation control means raises the structure by controlling the supply and discharge of compressed air to and from the air spring so that the vertical displacement detected by the vertical displacement detection means reaches the reference displacement from below the predetermined reference displacement. Let In the lowering process, the lifting control means lowers the structure by controlling the supply and discharge of compressed air to and from the air spring so that the vertical displacement detected by the vertical displacement detecting means reaches the reference displacement from above the reference displacement. Let

  The basic load calculation means uses the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the ascending process by the elevation control means, Calculate the spring load basic load in the upward direction. The basic load calculation means uses the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the lowering process by the elevating control means. Then, the spring load basic load in the downward direction is calculated. The spring load load calculating means calculates an average value of the upward spring load basic load and the downward spring load basic load calculated by the basic load calculation means as a spring load loaded by the air spring.

  The basic load calculation information is information that uniquely determines the spring load basic load based on the internal pressure of the air spring. The spring load basic load calculated using the basic load calculation information includes when the air spring is extended and shortened. Includes errors due to hysteresis (when the structure is rising and falling). Note that the basic load calculation information may be a linear approximation expression using the internal pressure of the air spring as a variable.

  Further, the vertical displacement detection means may sequentially detect the vertical displacement of the structure, and the elevation history storage means may store the vertical displacement detected by the vertical displacement detection means as the elevation history.

  In the above configuration, the internal pressure detecting means detects the internal pressure of the air spring, and the vertical displacement detecting means detects the vertical displacement of the structure.

  When the weight estimation process is started, the elevation control means executes the ascending process and raises the structure until the reference displacement is reached. The basic load calculation means uses the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the ascending process by the elevation control means, Calculate the spring load basic load in the upward direction. Further, the elevation control means performs a lowering process to lower the structure until reaching the reference displacement. The basic load calculation means uses the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the lowering process by the elevation control means, Calculate the spring load basic load in the downward direction. The ascending process by the elevating control means and the calculating process of the spring load basic load in the ascending direction by the basic load calculating means, and the descending process by the elevating control means and the calculating process of the spring load basic load in the descending direction by the basic load calculating means Any of these may be executed first.

  When the basic load calculation means calculates the spring load basic load in the upward direction and the downward direction, the spring load load calculation means calculates the average value of the spring load basic load in the upward direction and the spring load basic load in the downward direction ((increase Direction spring load basic load + downward direction spring load basic load) / 2) is calculated as a spring load loaded by the air spring.

  In this way, the basic load of the spring load calculated using the internal pressure of the air spring in the state where the structure has risen and reached the reference displacement, and the structure has been lowered and reached the reference displacement The average value of the spring load basic load in the downward direction calculated using the internal pressure of the air spring is calculated as the spring load that the air spring bears. And the estimation accuracy of the spring load can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the estimation precision of the spring burden load which an air spring bears can be improved.

It is the schematic diagram which looked at the vehicle concerning one embodiment of the present invention from back, (a) shows the state of the minimum vehicle height, and (b) shows the state raised from the minimum vehicle height to the standard vehicle height, respectively. FIGS. 2A and 2B are schematic views of a vehicle similar to FIG. 1, in which FIG. 1A shows a state in which the maximum vehicle height is reached, and FIG. It is a block diagram of a weight estimation apparatus. It is a flowchart of the weight estimation process which a weight estimation apparatus performs.

  Hereinafter, an embodiment in which the present invention is applied to a track will be described with reference to the drawings. In the following description, the front-rear direction means the front-rear direction of the vehicle, and the left-right direction means the left-right direction when facing the front of the vehicle.

  As shown in FIGS. 1 and 2, a vehicle (truck) 1 includes a body frame 2, a cab (not shown), a box-shaped loading platform 5, left and right front wheels (not shown), and left and right rear wheels 6. A front suspension (not shown), a rear suspension 7, and an ECU 10 (see FIG. 3).

  The body frame 2 has a pair of left and right side frames 3 (3L, 3R) extending substantially in parallel along the vehicle front-rear direction, and a plurality of linear shapes that are arranged at predetermined intervals in the vehicle front-rear direction and extend in the vehicle width direction. The cross frame 4 is provided. Each cross frame 4 is substantially orthogonal to the side frame 3, and both ends of the cross frame 4 are coupled to the left and right side frames 3L and 3R.

  The cab is disposed above the front part of the body frame 2, and the loading platform 5 is placed and fixed above the rear part of the body frame 2.

  The rear suspension 7 is composed of left and right air springs 8 (8L, 8R) each of which expands and contracts in the vertical direction by supplying and discharging compressed air, and supports the rear portion of the vehicle body frame 2. The left air spring 8L is interposed between the left side frame 3L and the axle (rear axle 9) of the rear wheel 6, and elastically supports the left side of the vehicle body frame 2 from below so that it can be raised and lowered. The right air spring 8R is interposed between the right side frame 3R and the rear axle 9, and elastically supports the right side of the vehicle body frame 2 from below so that it can be raised and lowered. The left and right sides of the vehicle body frame 2 (loading platform 5) are moved up and down by compressed air supply / discharge control with respect to the air spring 8. That is, the structure 11 composed of the vehicle body frame 2 and the structure supported by the vehicle body frame 2 (such as a loading object such as a loading platform 5 and a cab) is elastically supported from below by the air spring 8 to supply compressed air. And the air spring 8 is raised and lowered by the discharge.

  The left side frame 3L includes a left vehicle height sensor 12L that detects a vertical distance between the side frame 3L and the rear axle 9 (a vehicle height H on the rear left side of the structure 11) in the vicinity of the left air spring 8L. (See FIG. 3) is provided, and the right side frame 3R has a vertical distance between the side frame 3R and the rear axle 9 in the vicinity of the right air spring 8R (the vehicle height H on the rear right side of the structure 11). ) To detect a right vehicle height sensor 12R (see FIG. 3). Each distance in the vertical direction between the left and right side frames 3L, 3R and the rear axle 9 is the height (vertical displacement) of the structure 11 with respect to a predetermined reference height (in this embodiment, the height of the rear axle 9). The vehicle height sensors 12L and 12R function as vertical displacement detecting means for detecting the vertical displacement of the structure 11. Each of the vehicle height sensors 12L and 12R sequentially detects the left and right vehicle heights H of the structure 11, and outputs the detected vehicle height H to the ECU 10 (see FIG. 3).

  The left air spring 8L or an air pipe (not shown) that supplies compressed air to the left air spring 8L is provided with a left pressure sensor 14L (see FIG. 3) that detects the internal pressure of the left air spring 8L. A right pressure sensor 14R (see FIG. 3) for detecting the internal pressure of the right air spring 8R is provided in an air pipe (not shown) for supplying compressed air to the 8R or the right air spring 8R. Each of the pressure sensors 14L and 14R functions as an internal pressure detecting unit that detects the internal pressure of the air spring 8. The pressure sensors 14L and 14R sequentially detect the internal pressures of the left and right air springs 8L and 8R, and output the detected internal pressures to the ECU 10 (see FIG. 3).

  Although illustration and detailed description are omitted, the front suspension and related elements are also configured in the same manner as the rear suspension 7. That is, the front suspension is composed of left and right air springs that expand and contract in the vertical direction by supplying and discharging compressed air, and supports the front portion of the vehicle body frame 2. The left and right air springs are interposed between the left and right side frames 3L, 3R and the front wheel axle (front axle), and elastically support the left and right sides of the vehicle body frame 2 from below so as to be movable up and down. Left and right vehicle height sensors (not shown) detect the front left vehicle height H and the front right vehicle height H of the structure 11 in the vicinity of the left and right air springs, respectively, and output them to the ECU 10. The left and right pressure sensors detect the internal pressures of the left and right air springs, respectively, and output them to the ECU 10.

  The weight (sprung weight) of the structure 11 supported by the front suspension (air spring) and the rear suspension 7 (air spring 8) is a variable value (variation) that varies depending on the state (weight) of the bodywork or the load 12. Value). On the other hand, the weight (unsprung weight) of the structure (front and rear axles, wheels, etc.) of the vehicle 1 that is not supported by the front suspension and the rear suspension 7 is an invariable value (fixed value) determined by the specifications of the vehicle 1. ). Since the weight of the vehicle 1 is the sum of the sprung weight and the unsprung weight, the weight of the vehicle 1 (vehicle weight) can be estimated by estimating the sprung weight.

  The ECU 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), reads an air suspension control processing program stored in the ROM, and executes the air suspension control processing. As shown in FIG. 3, it functions as a vehicle height control unit 15. In addition, the ECU 10 functions as the weight estimation unit 16 by reading the weight estimation program stored in the ROM and executing the weight estimation process. Note that the air suspension control process and the weight estimation process are executed in the same manner for the left and right air springs of the front suspension and the left and right air springs 8 of the rear suspension 7, respectively. Will be mainly described, and the processing for the front suspension will be omitted as appropriate.

  The RAM functions as a temporary storage area for detection values and CPU calculation results detected by various sensors such as the vehicle height sensor 13 and the pressure sensor 14, and a storage area for various arithmetic expressions and various maps. Note that storage areas such as various arithmetic expressions and various maps may be set in the ROM, or may be set as part of various programs stored in the ROM.

  A display unit 24 and a weight estimation instruction switch 25 are provided in the vicinity of the driver's seat in the passenger compartment (for example, an instrument panel), and the display unit 24 and the weight estimation instruction switch 25 are each connected to the ECU 10. The display unit 24 has a display screen (not shown) for displaying the result of the weight estimation process by the weight estimation unit 16, and the weight estimation instruction switch 25 performs an input operation to instruct the start of the weight estimation process. We accept from the driver of.

  The vehicle height control unit 15 starts the air suspension control process when the vehicle 1 is started (power is turned on), and ends the air suspension control process when the vehicle 1 is stopped (power is turned off). In addition, during the execution of the air suspension control process, the vehicle height control unit 15 controls the supply and discharge of compressed air to and from the air spring 8 so that the left and right vehicle heights H of the vehicle body frame 2 become the predetermined standard vehicle height Hmid. To do. Specifically, the left air supply / exhaust valve 30L and the left and right vehicle exhaust valves 30L and 14R according to the air pressure detected by the pressure sensors 14L and 14R so that the left and right vehicle heights H detected by the left and right vehicle height sensors 12L and 12R become the standard vehicle height Hmid, respectively. A control signal is output to the right supply / exhaust valve 30R. The left supply / exhaust valve 30L and the right supply / exhaust valve 30R are electromagnetic valves that can open and close the compressed air supply line and the exhaust line for the left air spring 8L and the right air spring 8R. By outputting a control signal to the exhaust valve 30R, supply and discharge of compressed air to the left air spring 8L and the right air spring 8R are controlled.

  The weight estimation unit 16 includes a basic load calculation information storage unit (basic load calculation information storage unit) 18, a basic load calculation unit (basic load calculation unit) 19, a lift control unit (lift control unit) 20, and a spring load load calculation unit ( Spring load load calculating means) 23. The weight estimation unit 16 starts the weight estimation process prior to the air suspension control process by the vehicle height control unit 15 when the vehicle 1 is started (powered on). That is, the vehicle height control unit 15 waits for the weight estimation process by the weight estimation unit 16 to end and starts air suspension control. Further, the weight estimation unit 16 starts the weight estimation process when the weight estimation instruction switch 25 receives an input operation of a weight estimation process start instruction during execution of the air suspension control process by the vehicle height control unit 15. The vehicle height control unit 16 temporarily interrupts the air suspension control process while the weight estimation unit 16 is executing the weight estimation process, and resumes the air suspension control process after the weight estimation process is completed.

  The basic load calculation information storage unit 18 stores in advance a correspondence relationship between an arbitrary internal pressure P of the air spring 8 and the spring load basic load Fs as basic load calculation information. Since the load-internal pressure characteristic of the air spring 8 is represented by the following linear approximation formula (1), the linear approximation formula (1) is stored as basic load calculation information. The spring load basic load Fs is uniquely determined from the internal pressure P. The coefficient a and the intercept b in the formula (1) are constants determined according to the structure of the air spring 8.

    Fs = a × P + b (1)

  Since the left and right air springs 8L, 8R of the present embodiment have the same structure, the stored linear approximation formula is also common. In addition, the ascending / descending range of the structure 11 in the air suspension control process described above is set to a predetermined range (range between the minimum vehicle height Hmin and the maximum vehicle height Hmax) in which linear approximation of the load-internal pressure characteristic is established.

  Here, in the actual load-internal pressure characteristics, there is hysteresis when the air spring 8 is extended and shortened (when the structure 11 is raised and lowered), and the internal pressure P of the air spring 8 and the spring load (air) The relationship with the load on the spring 8 is that when the air spring 8 is extended (when the structure 11 is raised as shown in FIG. 1) and when it is shortened (when the structure 11 is lowered as shown in FIG. 2). ) And is different. That is, the case where the structure 11 rises and reaches an arbitrary vehicle height H (for example, the standard vehicle height Hmid) and the case where the structure 11 descends (for example, the case shown in FIG. 1 and the case shown in FIG. 2). Then, the internal pressure P of the air spring 8 is different.

  For this reason, the spring load basic load Fs calculated from the linear approximation formula (the above formula (1)) includes an error due to the hysteresis of the air spring 8.

  The raising / lowering control part 20 performs an ascending process and a descending process. In the ascending process, the elevating control unit 20 supplies compressed air to the air spring 8 so that the vehicle height H detected by the vehicle height sensor 13 reaches the reference vehicle height from below the predetermined reference vehicle height (reference displacement). The structure 11 is raised by controlling the discharge. In the lowering process, the lifting control unit 20 controls the supply and discharge of compressed air to the air spring 8 so that the vehicle height H detected by the vehicle height sensor 13 reaches the reference vehicle height from above the reference vehicle height. The structure 11 is lowered. In the present embodiment, the standard vehicle height Hmid is set as the reference vehicle height. In the ascending process, the elevating control unit 20 lowers the structure 11 to the minimum vehicle height Hmin and then raises it to the standard vehicle height Hmid. In the descending process, the elevating control unit 20 raises the structure 11 to the maximum vehicle height Hmax. Lower to high Hmid. The reference vehicle height may be set to other than the standard vehicle height Hmid. In the ascending process and descending process, all the air springs (left and right air springs of the front suspension and left and right air springs 8L and 8R of the rear suspension 7) are expanded and contracted, and all the vehicle height sensors 13 in the front and rear and right and left detect The vehicle height H to be lowered is lowered to the lowest vehicle height Hmin or raised to the highest vehicle height Hmax, and then raised or lowered to adjust to the standard vehicle height Hmid.

  The basic load calculation unit 19 targets all the air springs (the left and right air springs of the front suspension and the left and right air springs 8L and 8R of the rear suspension 7) as the target spring load basic load Fs ( U) and the spring-loaded basic load Fs (D) in the downward direction are calculated. The spring load basic load Fs (U) in the upward direction is the internal pressure P () detected by the pressure sensor 14 corresponding to each air spring 8 in a state where the structure 11 has reached the standard vehicle height Hmid by the upward processing by the upward / downward control unit 20. U) is calculated by substituting each into the linear approximation stored in the basic load calculation information storage unit 18. Further, the spring load basic load Fs (D) in the downward direction is the internal pressure detected by the pressure sensor 14 corresponding to each air spring 8 in a state where the structure 11 has reached the standard vehicle height Hmid by the lowering process by the lifting control unit 20. Calculation is performed by substituting P (D) into the linear approximation expressions stored in the basic load calculation information storage unit 18.

  The spring load load calculating unit 23 calculates the average value of the upward spring load basic load Fs (U) and the downward spring load basic load Fs (D) calculated by the basic load calculation unit 19 for each air spring. It is calculated as a spring load Fs (A) that the air spring bears. Specifically, the spring load basic load Fs (U) and the spring load basic load Fs (D) in the downward direction are substituted into the following equation (2) to calculate the spring load Fs (A). To do.

    Fs (A) = (Fs (U) + Fs (D)) / 2 (2)

  For all of the left and right air springs of the front suspension and the left and right air springs 8L and 8R of the rear suspension 7, the spring load calculation unit 23 calculates the spring load Fs (A) (four spring load front, left and right). Then, the weight estimation unit 16 calculates the sprung weight by adding the calculated four spring load loads, and adds the unsprung weight to the calculated sprung weight to obtain the vehicle weight (estimated value). calculate. In addition, the weight estimation unit 16 displays the calculated vehicle weight on the display screen of the display unit 24 and performs another process using the vehicle weight (for example, a system for determining the risk of rollover of the vehicle 1). In contrast, the calculated vehicle weight is provided.

  Next, the weight estimation process executed by the ECU 10 (weight estimation unit 16) will be described with reference to the flowchart of FIG. This process is started when the vehicle 1 is started (powered on) or when the weight estimation instruction switch 25 receives an input operation of a weight estimation process start instruction.

  When this process is started, the structure 11 (vehicle height H) is lowered so that the detection values from all the vehicle height sensors 13 reach the minimum vehicle height Hmin (step S1). Subsequently, the structure 11 is raised until the detection values from all the vehicle height sensors 13 become the standard vehicle height Hmid, and the vehicle height H is adjusted to the standard vehicle height Hmid (step S2). In this state, for each air spring 8, by substituting the internal pressure P (U) detected by the corresponding pressure sensor 14 into the linear approximation stored in the basic load calculation information storage unit 18, the spring load basic load in the upward direction Fs (U) is calculated (step S3).

  Next, the structure 11 (vehicle height H) is raised so that the detection values from all the vehicle height sensors 13 reach the minimum vehicle height Hmax (step S4). Subsequently, the structure 11 is lowered until the detection values from all the vehicle height sensors 13 become the standard vehicle height Hmid, and the vehicle height H is adjusted to the standard vehicle height Hmid (step S5). In this state, for each air spring 8, by substituting the internal pressure P (D) detected by the corresponding pressure sensor 14 into the linear approximate expression stored in the basic load calculation information storage unit 18, the spring load basic load in the downward direction is stored. Fs (D) is calculated (step S6).

  When the upward spring load basic load Fs (U) and the downward spring load basic load Fs (D) are calculated for all the air springs 8, the upward spring load load Fs (U) for each air spring 8 is calculated. ) And the spring load Fs (D) in the descending direction are averaged to calculate the spring load Fs (A) (step S7).

  When the spring load Fs (A) of all the air springs 8 is calculated, the sprung weight is calculated by adding the spring load Fs (A), and the unsprung weight is added to the calculated sprung weight. Thus, the vehicle weight (estimated value) is calculated (step S8), and the present process is terminated.

  Note that the execution order of the processing of step S1 to step S3 and the processing of step S4 to step S6 is arbitrary, the processing of step S4 to step S6 is executed first, and the processing of step S1 to step S3 is performed later. May be executed.

  As described above, in the present embodiment, the spring-loaded basic load in the upward direction calculated using the internal pressure P (U) of the air spring 8 in a state where the structure 11 is raised and reaches the standard vehicle height Hmid. Fs (U) and a spring load basic load Fs (D) in the downward direction calculated using the internal pressure P (D) of the air spring 8 in a state where the structure 11 is lowered and reaches the standard vehicle height Hmid. Is calculated as the spring load Fs (A) borne by the air spring 8, the influence of the error due to the hysteresis of the air spring 8 is reduced by a simple process, and the spring load Fs (A) is estimated. Accuracy can be improved.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the discussion and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it is needless to say that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

  For example, in the above embodiment, the air spring interposed between the axle and the vehicle body frame has been described. However, the structure supported by the air spring is not limited to the above embodiment, and other structures (for example, the cab and the vehicle body) It may be a cab in which the cab is elastically supported so as to be lifted and lowered from below by an air spring interposed between the frame and the frame.

  In the above embodiment, a full air suspension type vehicle in which both the front suspension and the rear suspension are configured by air springs has been described. However, the front suspension is configured by a metal spring such as a leaf suspension, and the rear suspension is configured by air. You may be comprised with the spring. In this case, the spring load on the front suspension side (front side) is stored as a fixed value, and the spring load on the rear suspension side (rear side) is estimated in the same manner as in the above embodiment, thereby estimating the vehicle weight. It can be carried out.

  The present invention can be widely applied to vehicles in which a structure is elastically supported by an air spring so as to be movable up and down.

1 Vehicle (truck)
2 Body frame 3, 3L, 3R Side frame 5 Loading platform 7 Rear suspension 8, 8L, 8R Air spring 9 Rear axle 10 ECU
11 Structure 12, 12L, 12R Vehicle height sensor (vertical displacement detection means)
14, 14L, 14R Pressure sensor (internal pressure detection means)
15 Vehicle height control unit 16 Weight estimation unit 18 Basic load calculation information storage unit (basic load calculation information storage means)
19 Basic load calculation unit (Basic load calculation means)
20 Lift control unit (lift control means)
23 Spring load calculation unit (spring load calculation unit)

Claims (1)

A weight estimation device mounted on a vehicle in which a structure is elastically supported from below by an air spring, and the structure is raised and lowered by expansion and contraction of the air spring by supply and discharge of compressed air,
An internal pressure detecting means for detecting an internal pressure of the air spring;
Vertical displacement detection means for detecting the height of the structure relative to a predetermined reference height as vertical displacement;
Basic load calculation information storage means for preliminarily storing a correspondence relationship between an arbitrary internal pressure of the air spring and a spring load basic load as basic load calculation information;
An ascending process for raising the structure so that the vertical displacement detected by the vertical displacement detecting means reaches the reference displacement from below a predetermined reference displacement by controlling supply and discharge of compressed air to and from the air spring; Elevating control means for performing a lowering process for lowering the structure so that the vertical displacement detected by the vertical displacement detecting means reaches the reference displacement from above the reference displacement;
Using the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the ascent process, the basic load of the spring in the ascent direction While calculating the load, using the basic load calculation information stored in the basic load calculation information storage means and the internal pressure detected by the internal pressure detection means in a state where the structure has reached the reference displacement by the descending process Basic load calculation means for calculating the spring load basic load in the downward direction;
Spring load load calculation means for calculating an average value of the spring load basic load in the upward direction and the spring load basic load in the downward direction calculated by the basic load calculation means as a spring load load borne by the air spring; A vehicle weight estimation apparatus.

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