An assisted leaf spring, passive leaf spring assembly and method of designing the same

Abstract

The application discloses an auxiliary spring leaf, a passive steel plate spring assembly and a design method thereof, and belongs to the technical field of automobiles. The auxiliary spring leaf is located between a main steel plate spring and a steel plate spring seat. The upper end of the auxiliary spring leaf comprises a cantilevered section and a pre-bent section. The middle part of the auxiliary spring leaf is provided with a bent section. The lower end of the auxiliary spring leaf comprises a tail section and a matching section. The cantilevered section, the pre-bent section, the bent section, the tail section and the matching section are sequentially connected. The two ends of the main steel plate spring are respectively pressed on the upper surfaces of the two cantilevered sections. The lower surfaces of the cantilevered sections are pressed on the upper end of the steel plate spring seat. The matching section is fixedly connected between the lower end of the steel plate spring seat and a drive axle. The contact points of the main steel plate spring and the auxiliary spring leaf continuously change from the ends to the middle, and the suspension stiffness also continuously changes, so that the impact force caused by the sudden change of the stiffness, such as the impact limiting, does not occur, and the riding comfort of passengers is beneficially ensured.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to an auxiliary spring, a passive leaf spring assembly, and a design method thereof. Background Technology

[0002] Commercial vehicle suspensions have long faced a structural contradiction: ride comfort requires lower suspension stiffness to attenuate vibrations transmitted from the road surface to the vehicle body; while load-bearing capacity requires higher suspension stiffness to prevent excessive deformation or even suspension breakdown when the vehicle is under heavy load.

[0003] Traditional leaf springs are designed with high stiffness to meet heavy-load requirements. Under no-load conditions, the suspension deflection frequency is too high, resulting in abnormal vehicle bumps, poor ride comfort, and poor tire contact with the ground. Some leaf springs use a main spring + auxiliary spring structure, which can achieve two levels of stiffness, but the stiffness has a sudden abrupt change, resulting in an uneven transition and failing to fundamentally solve the problem. Moreover, under heavy loads, the first-stage spring bears a large load, posing a high risk to reliability.

[0004] Air spring suspension achieves near-ideal adaptive stiffness changes with load by actively adjusting air pressure, resulting in superior ride comfort. However, its system is complex and costly, and it is susceptible to fatal failure risks such as airbag leakage and electronic control malfunctions, making its robustness insufficient for harsh operating conditions.

[0005] Therefore, the market urgently needs a new solution that can inherit the advantages of high reliability and low cost of traditional leaf springs, and can achieve adaptive and continuous stiffness adjustment like air springs. Summary of the Invention

[0006] The purpose of this invention is to provide an auxiliary reed, a passive leaf spring assembly and its design method. The passive leaf spring assembly does not require any external energy source, sensor or controller. It can automatically increase the suspension stiffness when the vehicle load increases through a purely mechanical structure, so as to achieve a balance between high ride comfort under no-load and high load-bearing capacity under full load throughout the entire load spectrum.

[0007] In a first aspect, the present invention describes an auxiliary spring located between the main leaf spring and the leaf spring seat. The auxiliary spring has an upper end including a cantilever section and a pre-bent section, a middle section having a bent section, and a lower end including a tail section and a mating section. The cantilever section, the pre-bent section, the bent section, the tail section, and the mating section are sequentially connected and integrally formed. The two ends of the main leaf spring press against the upper surfaces of the two cantilever sections respectively, and the lower surface of the cantilever section presses against the upper end of the leaf spring seat; the mating section is fixedly connected between the lower end of the leaf spring seat and the drive axle.

[0008] Preferably, the tail section and the mating section are parallel to the horizontal plane, and the angle of elevation formed by the extension line of the cantilever section and the horizontal plane is 3-10°.

[0009] Preferably, the thickness of the overhanging section gradually changes from 4-10mm to 10-16mm in the direction close to the pre-bending section; and the width gradually changes from 40-80mm to 80-120mm. The thickness of the pre-bending section gradually changes from 10-16mm to 6-12mm and the width gradually changes from 80-120mm to 40-80mm in the direction close to the bending section. The bending section has a thickness of 6-12mm and a width of 40-80mm; The tail section is 6-12mm thick and its width gradually changes from 40-80mm toward the mating section to the same width as the mating section. The thickness of the mating section is 6-12mm.

[0010] Preferably, the distance between the midpoint of the bent section and the center of the leaf spring seat is 260-360mm.

[0011] Preferably, the auxiliary reed is made of spring steel.

[0012] Secondly, the present invention also describes an auxiliary spring located between the main leaf spring and the leaf spring seat, the auxiliary spring including a cantilever section, the two ends of which are respectively connected to the lower end of the main leaf spring and the upper end of the leaf spring seat.

[0013] Preferably, the auxiliary reed is made of glass fiber material.

[0014] Thirdly, the present invention describes a passive leaf spring assembly, comprising: a main leaf spring, an auxiliary spring as described in any one of the claims, and a leaf spring seat; The main leaf spring is connected to the vehicle frame at its middle part. Both ends of the main leaf spring press against the upper surfaces of the overhang sections of the two auxiliary springs respectively. The lower surface of the overhang section abuts against the upper end face of the leaf spring seat. The mating section of the auxiliary spring is fixedly connected between the lower end of the leaf spring seat and the drive axle.

[0015] Fourthly, the present invention describes a design method for a passive leaf spring assembly, comprising the following steps: S1: Obtain the target offset frequency range and vehicle parameters of the vehicle under full load and no load conditions; S2: Based on the target off-frequency range and vehicle parameters under full load, determine the stiffness requirement of the suspension under full load, which serves as the target stiffness of the main leaf spring. Based on the target frequency range and vehicle parameters under no-load conditions, determine the total stiffness requirement of the vehicle's suspension under no-load conditions. S3. Determine the target stiffness of the auxiliary spring under no-load conditions based on the total stiffness requirements and the target stiffness of the main leaf spring. S4. Adjust the elevation angle of the cantilever section, as well as the width and thickness of the cantilever section, pre-bending section, bending section, tail section, and mating section, until the actual stiffness of the auxiliary spring in the no-load state reaches the target stiffness of the auxiliary spring in the no-load state.

[0016] Preferably, the vehicle parameters include the sprung mass of the vehicle under both unloaded and fully loaded conditions.

[0017] Compared with the prior art, the present invention has the following advantages: 1. When the vehicle is not carrying cargo, the vehicle load is low, and the contact point between the main leaf spring and the auxiliary leaf spring is at the end. At this time, the main leaf spring and the auxiliary leaf spring form a series spring system. The total stiffness is less than that of either spring, and the contact point is far away from the respective support points of the two springs, which lengthens the lever arm. The stiffness of both springs becomes smaller, further reducing the stiffness of the series spring system. This keeps the suspension at a low stiffness level, providing good ride comfort for the occupants.

[0018] 2. When the vehicle is fully loaded, the main leaf spring is subjected to a downward force from the frame, pressing against the auxiliary spring. The auxiliary spring is compressed and deformed. Due to its unique streamlined shape, the contact point between the main leaf spring and the auxiliary spring gradually approaches the contact point between the auxiliary spring and the leaf spring seat. The stiffness exhibited by the auxiliary spring gradually increases until it no longer exhibits spring action. At this point, the stiffness of the suspension system is equal to that of the main leaf spring, resulting in good load-bearing performance. The vehicle suspension stiffness designed in this invention can adaptively change with the vehicle's load, which is beneficial to passenger comfort and the vehicle's own load-bearing capacity.

[0019] 3. When the vehicle encounters an impact, the contact point between the main leaf spring and the auxiliary leaf spring will change continuously from the end to the middle, and the suspension stiffness will also change continuously. There will be no impact force caused by sudden stiffness changes such as hitting the limit stop, which helps to ensure the ride comfort of passengers.

[0020] 4. This invention is the first to achieve the function of smoothly adjusting suspension stiffness on a leaf spring without external energy or control, relying solely on the deformation caused by the load itself, using only the deformation of the leaf spring itself caused by changes in vehicle load as the sole input signal. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the present invention in its unloaded state; Figure 2 This is a schematic diagram of the invention under full load. Figure 3 This is a schematic diagram of the auxiliary reed of the present invention; Figure 4 This is a schematic diagram of the glass fiber auxiliary spring of the present invention; Figure 5 This is a schematic diagram of the downward-protruding auxiliary spring in the cantilever section of the present invention; In the picture: 1. Main leaf spring; 2. Auxiliary leaf spring; 3. Leaf spring seat; 4. Drive axle; 5. Chassis. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0026] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0027] Example 1 See Figure 1 , 2As shown in Figure 3, the present invention provides an auxiliary spring 2 located between the main leaf spring 1 and the leaf spring seat 3. The upper end of the auxiliary spring 2 includes a cantilever section and a pre-bent section, the middle part has a bent section, and the lower end includes a tail section and a mating section. The cantilever section, the pre-bent section, the bent section, the tail section and the mating section are connected in sequence. When the vehicle is unloaded or fully loaded, the two ends of the main leaf spring 1 press against the upper surfaces of the two overhang sections respectively, and the lower surface of the overhang section presses against the upper end of the leaf spring seat 3; the mating section is fixedly connected between the lower end of the leaf spring seat 3 and the drive axle 4.

[0028] Preferably, the tail section and the mating section are parallel to the horizontal plane, and the angle of elevation formed by the extension line of the cantilever section and the horizontal plane is 3-10°.

[0029] Preferably, the arc position of the auxiliary spring 2 is 280mm away from the center position of the leaf spring seat 3.

[0030] Preferably, the auxiliary spring 2 is a variable thickness spring with a unique streamlined shape. Its thickness is 12mm near the leaf spring seat 3 and 6mm at the bend. In specific embodiments, different streamlined shapes can be adjusted to meet different stiffness requirements.

[0031] Preferably, the overhanging section has a thickness that gradually decreases from 6mm to 12mm and a width that gradually decreases from 45mm to 90mm; the pre-bending section has a thickness that gradually decreases from 12mm to 8mm and a width that gradually decreases from 90mm to 45mm; the bending section has a thickness of 8mm and a width of 45mm; and the tail section has a thickness of 8mm and a width that gradually decreases to 170mm. A square root curve is recommended for the gradual change process.

[0032] Example 2 See Figure 1 , 2 As shown in Figure 3, this invention provides a passive leaf spring assembly, including a main leaf spring 1, an auxiliary leaf spring 2, and a leaf spring seat 3. The main leaf spring 1 is connected to the vehicle frame 5 in the middle, and its two ends press against the auxiliary leaf spring 2. The main leaf spring 1 is a linear spring with constant stiffness. The auxiliary leaf spring 2 has a "C"-shaped structure. The upper surface of the upper end of the auxiliary leaf spring 2 contacts the main leaf spring 1, and the lower surface of the upper end of the auxiliary leaf spring 2 contacts the upper surface of the leaf spring seat 3. The position of the contact point changes spontaneously with the load. The other end is fixed to the drive axle.

[0033] See Figure 1As shown, when the vehicle is lightly loaded, used only for passenger transport or carrying a small amount of cargo, the contact point between the main leaf spring 1 and the auxiliary leaf spring 2 is at the end. The main leaf spring 1 and the auxiliary leaf spring 2 form a series spring system with a total stiffness less than either spring alone. Furthermore, the contact point is far from the respective fulcrums of the two springs, lengthening the lever arm and reducing the stiffness of both springs. This further reduces the stiffness of the series spring system, keeping the suspension at a low stiffness level. At this time, the suspension system operates within the passenger comfort zone.

[0034] See Figure 2 As shown, when the vehicle is fully loaded with cargo, the main leaf spring 1 is subjected to a downward force from the vehicle frame, pressing against the auxiliary leaf spring 2. The auxiliary leaf spring 2 deforms under pressure, and due to its unique streamlined shape, the contact point between the main leaf spring 1 and the auxiliary leaf spring 2 gradually approaches the contact point between the auxiliary leaf spring 2 and the leaf spring seat 3. The stiffness exhibited by the auxiliary leaf spring 2 gradually increases until it no longer exhibits spring action, and the stiffness of the suspension system is equal to that of the main leaf spring. At this time, the supporting suspension system operates in the cargo-bearing area.

[0035] When a vehicle encounters an impact, the contact point between the main leaf spring 1 and the auxiliary leaf spring 2 changes continuously from the end to the middle, and the overall stiffness of the suspension also changes continuously and smoothly. This characteristic fundamentally avoids the abrupt change in stiffness and the rigid impact caused by the impact limiting block that occurs in the traditional main spring + auxiliary spring structure, effectively reducing the peak impact load transmitted to the vehicle body and occupants, and significantly improving ride comfort.

[0036] This invention designs a vehicle leaf spring suspension elastic component that can adaptively adjust the vehicle suspension stiffness according to different vehicle loads. When the vehicle load is light, the contact point between the main leaf spring and the auxiliary leaf spring is at the end, and the overall stiffness of the suspension system remains at a low level, providing good ride comfort for passengers. When the vehicle is fully loaded with heavy cargo, the contact point between the main leaf spring and the auxiliary leaf spring is close to the contact point between the adaptive variable stiffness auxiliary leaf spring and the leaf spring seat, and the overall stiffness of the suspension system is equal to the stiffness of the main leaf spring, resulting in higher stiffness and ensuring the vehicle's load-bearing capacity. When the vehicle is subjected to a large impact, the contact point between the main leaf spring and the adaptive variable stiffness auxiliary leaf spring changes continuously from the end to the middle, and the suspension stiffness changes continuously accordingly, preventing the impact force caused by sudden stiffness changes such as hitting the limit stop, thus ensuring passenger ride comfort.

[0037] This invention satisfies both the comfort requirements under low load conditions and the load-bearing requirements under high load conditions. The transition between the two states is continuous and smooth, without the impact force from collision limiters, which improves passenger comfort and reduces impact damage to the entire vehicle.

[0038] The passive leaf spring assembly of the present invention has a stiffness of 700 N / mm under a load of less than 25,000 N and a stiffness of 2400 N / mm under a load of more than 30,000 N, with a linear transition between 25,000 N and 30,000 N.

[0039] More preferably, the auxiliary spring 2 is fixed by having its lower end clamped between the leaf spring seat 3 and the drive axle 4, and then secured with bolts. Alternatively, the auxiliary spring 2 can also be fixed to the drive axle in other ways.

[0040] More preferably, the arc position of the auxiliary spring 2 is 280mm away from the center position of the leaf spring seat 3.

[0041] More preferably, the auxiliary spring 2 is a variable-thickness spring with a unique streamlined shape, having a thickness of 12mm near the leaf spring seat 3 and a thickness of 6mm at the bend. In specific embodiments, different streamlined shapes can be adjusted to adapt to different stiffness requirements.

[0042] More preferably, the portion of the auxiliary spring 2 extending outward from the outer side of the leaf spring seat 3 is straight, and the stiffness can also be adjusted by adjusting the shape.

[0043] More preferably, the opening of the auxiliary spring 2 faces outward, but it can also be adjusted to face inward.

[0044] More preferably, the auxiliary spring 2 is made of spring steel.

[0045] More preferably, the arc of the contact surface between the leaf spring seat 3 and the auxiliary spring 2 is symmetrical. In specific embodiments, other more complex asymmetrical structures can also be selected.

[0046] Example 3 See Figure 4 As shown, this embodiment of the invention provides an auxiliary spring 2, located between the main leaf spring 1 and the leaf spring seat 3. The auxiliary spring 2 includes a cantilever section, with its two ends connected to the lower end of the main leaf spring 1 and the upper end of the leaf spring seat 3, respectively.

[0047] The auxiliary reed 2 is made of glass fiber material.

[0048] When the auxiliary spring is made of other materials such as fiberglass, only the overhang section can be retained, and other unnecessary parts can be removed.

[0049] This solution is a simplified variation of Examples 1 and 2. When the auxiliary spring is made of non-metallic materials such as glass fiber, only the core functional part of the cantilever section can be retained, while other parts such as the pre-bending section, bending section, tail section and mating section can be removed to reduce manufacturing costs and process difficulty.

[0050] Example 4 See Figure 5 As shown, this embodiment of the invention provides an auxiliary spring 2. Based on embodiment 1, the overhang section is adjusted to a downwardly protruding arc shape, increasing the range of low stiffness sections, which is suitable for vehicles with a high unloaded load ratio.

[0051] Example 5 This invention also provides a design method for a passive leaf spring assembly with adaptive stiffness characteristics. The leaf spring assembly includes a leaf spring, an auxiliary spring, and a leaf spring seat. The method specifically includes the following steps: S1. Based on vehicle comfort requirements, obtain the target frequency offset range and vehicle parameters under full load and no load conditions; vehicle parameters include vehicle model and sprung mass under no load and full load conditions.

[0052] S2. Based on the target frequency range and vehicle parameters under full load, determine the stiffness requirement of the suspension under full load, which will be used as the target stiffness c of the main leaf spring. 主 From the formula Calculate c 主 , where f 满 For full-load suspension frequency offset, c 主 Target stiffness of main leaf spring, m 满 The sprung mass under full load; Based on the target frequency offset range and vehicle parameters under no-load conditions, determine the total stiffness requirement c of the vehicle's suspension under no-load conditions. 总 From the formula Calculate f 空 For full-load suspension frequency offset, c 总 For the total stiffness requirement, m 空 This refers to the sprung mass under no-load conditions. S3. Based on the total stiffness requirement and the target stiffness of the main leaf spring, determine the target stiffness c of the auxiliary spring under no-load conditions. 辅 From the formula for series springs calculate; S4. Adjust the elevation angle of the cantilever section, as well as the width and thickness of the cantilever section, pre-bending section, bending section, tail section, and mating section, until the actual stiffness of the auxiliary spring under no-load conditions reaches the target stiffness of the auxiliary spring under no-load conditions. If necessary, adjust the streamline shape of the leaf spring seat to match the deformation of the auxiliary spring.

[0053] For example, in Example 1, the stiffness of the auxiliary spring decreases by approximately 10% for every 10% increase in the pre-bending length; the stiffness increases by approximately 17% for every 10% increase in the thickness at the contact point between the leaf spring seat and the adaptive variable stiffness auxiliary spring; and the stiffness increases by approximately 13% for every 10% increase in the thickness of the bending section and beyond. Elevation angle: 3–10°.

[0054] S5. Sample installation, actual vehicle evaluation and adjustments, adjustments and optimizations based on subjective and objective evaluations; S6. Repeat steps S4-S5 above until the actual vehicle meets the requirements of passenger comfort and cargo capacity. S7. Freeze samples for mass production.

[0055] Compared to traditional leaf springs, this invention significantly reduces unloaded stiffness, resulting in a generational improvement in ride comfort and tire contact with the ground. Compared to traditional two-stage leaf springs, the stiffness transition is smooth and continuous, eliminating abrupt impacts and enhancing comfort. Compared to air spring suspensions, it retains the high strength, impact resistance, maintenance-free operation, and high reliability of leaf springs, completely avoiding the risks of air leaks, electronic control failures, and other issues that could render the vehicle immobile, while significantly reducing costs.

[0056] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An auxiliary spring (2) located between a main leaf spring (1) and a leaf spring seat (3), characterized in that, The auxiliary spring (2) has an upper section and a pre-bending section, a middle section and a bending section, and a lower section and a tail section and a mating section; the upper section, the pre-bending section, the bending section, the tail section and the mating section are connected in sequence and integrally formed; The two ends of the main leaf spring (1) press against the upper surfaces of the two cantilever sections respectively, and the lower surface of the cantilever section presses against the upper end of the leaf spring seat (3); the mating section is fixedly connected between the lower end of the leaf spring seat (3) and the drive axle (4).

2. The auxiliary reed (2) according to claim 1, characterized in that, The tail section and the mating section are parallel to the horizontal plane, and the extension line of the cantilever section forms an elevation angle of 3-10° with the horizontal plane.

3. The auxiliary reed (2) according to claim 1, characterized in that, The thickness of the overhanging section gradually changes from 4-10mm to 10-16mm in the direction close to the pre-bending section; the width gradually changes from 40-80mm to 80-120mm. The thickness of the pre-bending section gradually changes from 10-16mm to 6-12mm and the width gradually changes from 80-120mm to 40-80mm in the direction close to the bending section. The bending section has a thickness of 6-12mm and a width of 40-80mm; The tail section is 6-12mm thick and its width gradually changes from 40-80mm toward the mating section to the same width as the mating section. The thickness of the mating section is 6-12mm.

4. The auxiliary reed (2) according to claim 1, characterized in that, The distance between the midpoint of the bending section and the center of the leaf spring seat (3) is 260-360mm.

5. The auxiliary reed (2) according to claim 1, characterized in that, The auxiliary spring (2) is made of spring steel.

6. An auxiliary spring (2) located between the main leaf spring (1) and the leaf spring seat (3), characterized in that, The auxiliary spring (2) includes a cantilever section, the two ends of which are respectively connected to the lower end of the main leaf spring (1) and the upper end of the leaf spring seat (3).

7. The auxiliary reed (2) according to claim 6, characterized in that, The auxiliary reed (2) is made of glass fiber material.

8. A passive leaf spring assembly, characterized in that, include: The main leaf spring (1), the auxiliary spring (2) as described in any one of claims 1-5, and the leaf spring seat (3); The main leaf spring (1) is connected to the frame (5) at the middle. The two ends of the main leaf spring (1) are pressed on the upper surface of the overhang section of the two auxiliary springs (2). The lower surface of the overhang section abuts against the upper surface of the leaf spring seat (3). The mating section of the auxiliary spring (2) is fixedly connected between the lower end of the leaf spring seat (3) and the drive axle (4).

9. A design method for a passive leaf spring assembly as described in claim 8, characterized in that, Includes the following steps: S1: Obtain the target offset frequency range and vehicle parameters of the vehicle under full load and no load conditions; S2: Based on the target off-frequency range and vehicle parameters under full load, determine the stiffness requirement of the suspension under full load, which serves as the target stiffness of the main leaf spring. Based on the target frequency range and vehicle parameters under no-load conditions, determine the total stiffness requirement of the vehicle's suspension under no-load conditions. S3. Determine the target stiffness of the auxiliary spring under no-load conditions based on the total stiffness requirements and the target stiffness of the main leaf spring. S4. Adjust the elevation angle of the cantilever section, as well as the width and thickness of the cantilever section, pre-bending section, bending section, tail section, and mating section, until the actual stiffness of the auxiliary spring in the no-load state reaches the target stiffness of the auxiliary spring in the no-load state.

10. The design method of the passive leaf spring assembly according to claim 9, characterized in that, The vehicle parameters include the sprung mass of the vehicle under both unloaded and fully loaded conditions.

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