WO1999042801A1

WO1999042801A1 - Dynamometer

Info

Publication number: WO1999042801A1
Application number: PCT/CA1999/000166
Authority: WO
Inventors: Yvon Rancourt
Original assignee: Yvon Rancourt
Priority date: 1998-02-23
Filing date: 1999-02-23
Publication date: 1999-08-26
Also published as: CA2230202A1; AU2706799A

Abstract

A vehicle brake testing dynamometer comprising a rotatable surface simulation member (36) having an annular cylindrical surface. Friction band means (44) are mounted on the cylindrical surface, and motor means (20) for rotating the surface simulation member (36). A sub-frame (46) is mounted adjacent the surface simulation member (36). The sub-frame (46) mounts at least one wheel testing unit (100) wherein the wheel testing unit (100) includes a carriage (62) movable in a radial axis to and from the surface simulation member (36). The carriage (62) mounts an individual vehicle wheel suspension including a tire, a wheel hub, a brake, and suspension damping means (103) whereby the carriage (62) can move towards and away from the surface simulation member (36) to bring the tire in contact with the friction band means (44) on the surface simulation member (36) and tangentially thereto. Means are provided for varying the position of the carriage (62), the relative speed of the simulation member (36), and the application or release of the brakes in order to simulate virtual running and braking conditions of the vehicle wheel suspension.

Description

DYNAMOMETER

Technical Field

The present invention relates to a dynamometer, and more particularly, to a vehicle simulation brake-testing dynamometer for simulating and testing vehicle brakes.

Background Art

Typically, vehicle brakes have been tested on a dynamometer by mounting the hub and brakes of a wheel directly to the shaft and frame of a dynamometer. However, on a vehicle, the brakes are interdependent on the suspension system, brake booster, rotor, wheel, brake control system, and interface between road and tire with skid and traction variables. The brake torque variation is a non- stationary function and its frequency is a function of the rotational speed. Torque is significantly influenced by both rotor and lining physical characteristics, and these characteristics are influenced by increasing temperature. For instance, the term "brake roughness" is used to describe undesirable tactile vibration felt during the braking event . Brake squeal is a self-excited vibration, and it occurs when the exciting energy caused on the friction surface between the pad and rotor exceeds the damping energy.

In recent years, demands for an improved brake feel has increased besides the normal required performance of effectiveness and reliability. In particular, it has been found that various characteris- tics of a brake booster affects not only the pedaling reduction function but also the brake feel. An improvement in the operation responsiveness is also an important safety factor. A brake booster functions by generating a boosting force which is relative to the opera- - 2 -

tional force applied on the brake pedal and, therefore, generates a large output with small operational force.

In practice, the lack of exact knowledge about the behavior of wheel suspension dynamics and of the tire dynamics is a major problem for the evaluation of the slip and wheel speed respectively. These two are important signals for modern automotive brake control systems . The performance of these systems strongly depends on the quality of the evaluated wheel speed and the slip. Due to the horizontal motion or oscillations of the wheel hub, angular speed fluctuations can evolve affecting directly the measured wheel speed signal.

Disclosure of the Invention

It is an aim of the present invention to provide an improved brake evaluation system by simulating virtual real testing of the brakes.

It is a further aim of the present invention to measure vibration frequencies and squeal noise, temperatures, distribution of brake force, pressure and torque variation, deflections and strains, acceleration, air flow velocity and pressure in and around the brakes, rolling resistance and air dynamic drag as well as yaw rate velocity.

A construction in accordance with the present invention comprises a surface simulation member having an annular cylindrical surface, replaceable friction band means mountable on said cylindrical surface, and motor means for driving the simulation member, a sub- frame mounted adjacent the surface simu- lation member, the sub-frame mounting at least one wheel testing unit wherein the wheel testing unit includes a carriage movable in a radial axis to and from the simulation member, the carriage mounting an individual vehicle wheel suspension including the hub, the brake, and suspension damping means whereby the carriage can move towards and away from the simulation member to bring the vehicle wheel in contact with the - 3 -

friction surface on the simulation member and tangen- tially thereto, and means are provided for varying the position of the carriage, the relative speed of the simulation member, and the application or release of the brakes to simulate virtual running and braking conditions of the vehicle wheel .

It is noted that measurements of a naturally occurring squeal in the brakes can be recorded in order to determine the nature of rotor lining and back plate vibrations.

The utilization of brake torque variation measurement can be successfully employed as a means to benchmark various brake caliper/housing designs, compare lining material characteristics as well as provide means to assess the roll of the vehicle in brake roughness .

The present invention can also be used to determine a braking force distribution which provides a definition of the relative braking force exerted at each of the individual vehicle axles as a component of the total braking force. Also, the rolling resistance, which is a result of the deformation process occurring at the contact patch between the tire and the road surface, can be measured accurately. Furthermore, during car motion, especially during acceleration or braking, deflections of the flexibly mounted wheel suspension and of the tire disturbance can be measured accurately using the braking simulator of the present invention. Brief Description of the Drawings

Fig. 1 is a vertical fragmentary cross- section of an embodiment of the present invention;

Fig. 2 is a side elevation, partly in cross- section, showing the embodiment of Fig. 1; Fig. 3 is a perspective view of a detail shown in Fig. 1 but taken from a different angle; and - 4 -

Fig. 4 is an enlarged fragmentary top plan view of the detail shown in Fig. 3.

Mode For Carrying Out The Invention

Referring now to the drawings and especially to Figs. 1 and 2, there is shown a vehicle brake simulation dynamometer 10 which comprises a frame 12 on which the various elements which will be described are mounted. From one end of the frame 12, there is a cradle 14 pivoted on trunnions 16 mounted to the frame 12. A motor 20 is mounted to the cradle, which is allowed to oscillate about the axis of the trunnions 16. The motor 20 having a drive shaft is co-axial to the axis of trunnions 16.

The drive shaft 20a mounts a gear 24 while a large gear wheel 26 is fixedly mounted on shaft 28 which is journaled in bearings 30 and 32 on the frame

12. A timing belt 22 drives the gear wheel 26 as it passes over the gear 24 on drive shaft 20a.

The cradle suspension 14 for the motor 20 allows the measurement of torque response sensed by the wheel 26. The gear wheel 26 is fixed to the shaft 28.

Referring to Fig. 2, the surface simulation cylinder 36 is illustrated, mounted by means of hub 38 to the shaft 28. The wheel 36 includes a web 40 in a radial plane extending from the hub 38 and a wide circular cylindrical peripheral surface member 42. Replaceable friction bands 44 can be fitted on the surface 42. The bands 44 can be made of grit material or other friction simulated surfaces. A sub-frame 46 is mounted adjacent the wheel

36 and, as seen in the drawings, at least four radially extending ramps 48, 50, 52, and 54 are mounted to the sub-frame 46. The ramps are radial relative to the axis of the shaft 28. Carriages 56, 58, 60, and 62 are mounted for sliding movement on ramps 48, 50, 52, and 54 respectively. The carriages, which mount the vehicle wheels to be tested, as will be described, can move the - 5 -

vehicle wheels in radial axes such that the contact patch of the tire on the friction band 44 will be tangent to the surface thereof .

Fig. 3 shows a typical carriage 62 which includes a sliding table 64 mounted on a pair of tracks 66 and 68. A cylinder and piston (not shown) is mounted to the ramp 54 and to the carriage 62 in order to move the carriage 62 on the tracks 66 and 68. The cylinder and piston will respond to actuators controlled by a computer to which is provided the necessary simulation input so as to move the carriage 62 and the wheel assembly 100, towards and away from the surface 44.

Bearings 72 and 74 are mounted to the table 64, and a shaft 76 is journaled in the bearings 72 and 74. At one end of the shaft 76 is an arm 78 keyed to the shaft. The arm 78 is connected to a load cell 82 which will be used to measure various criteria of the wheel test .

A back plate 88 is mounted to flange 90 fixed to the shaft 76, and struts 84 are fixed to the flange 86 on the shaft 76 as well as to the back plate 88 and struts 84a support the bracket 92. The wheel assembly 100 is mounted to the back plate 88 and bracket 92. Any angular deflection applied to the wheel assembly 100, because of acceleration or deceleration of the simulation member 36 will be sensed by load cell 82 and recorded through the intermediary of shaft 76 and arm 78.

Referring to Fig. 4, the bracket 92 is fixedly mounted to the back plate 88 and the wheel assembly 100 is mounted thereto. As seen in Fig. 4, spring bracket 94 is mounted to the bracket 92 but without the spring. In its stead, two pivoting levers 96 and 98 connect the spring bracket 94 to the bracket 92 in order to permit lateral movement but not extensible or compression movement between the bracket 94 and bracket 92. - 6 -

A shock absorber 103 extends through the spring bracket 94 and is mounted at one end to the bracket 92 and at the other end to the conventional hub 99 mounting for the wheel 100. Various suspension pivoting links, such as at 106, represent other suspension elements of a typical vehicle wheel assembly 100.

Thus, when the brakes are being tested, the whole of the vehicle wheel assembly 100, including its suspension elements (normally mounted to the frame of the vehicle) are mounted to the bracket 92 and back plate 88 which in turn is moved in a reciprocal manner by means of carriage 62 on ramp 54. Thus, the tire on wheel 100 can be pressed against the friction surface 44 at different loads in order to simulate running conditions.

Referring back to Figs. 1 and 2 a ventilation duct system 120 is illustrated. This ventilation duct system serves two purposes . On the one hand it allows cooling air to dissipate the heat generated by the tires on the grit surface 44 and to carry away rubber particles which would be suspended in the air. Such rubber particles can be filtered at the outlet of exhaust duct 132.

On the other hand a wind effect can be created by the incoming air if it is pumped under pressure through separate ducts 124 and 128. This wind tunnel effect provides an air stream against the tires of the wheel assembly 100, 108, 110 and 112 and simulates the rushing air passing by the tires when the vehicle is traveling. Thus, duct plates 124a and 128a separate the stream of air to either side of the cylindrical members 36 and the air exhausted through opening 126 communicating with the exhaust duct 132 as shown in Fig. 2. A single wheel assembly 100 can be tested or it can be tested with the other three wheel assemblies 108, 110, and 112. As set up in the present embodiment, - 7 -

wheel assembly 100 represents a front wheel, for instance, a right front wheel, while wheel assembly 112 represents the right rear wheel . On the other side of the dynamometer, the left rear wheel 110 and left front wheel 108 are located. Thus, all four wheels of the vehicle can be tested under different running and braking conditions.

Referring to Fig. 2, there is shown a possible location of an operator sitting on a platform 114 mounted in the frame 12. The seat 120 and the brake pedal 118 as well as the control panel 116 would be mounted to simulate the position of the driver in a vehicle in order to experience the pedal-feel with respect to the wheel assembly 100. 108, 110 and 112 being tested on the cylindrical member 36. Thus, the brakes for a particular vehicle design may be adjusted and the design thereof may be enhanced by use of the present invention.

Claims

CLAIMS ;

1. A vehicle brake testing dynamometer comprising a rotatable surface simulation member having an annular cylindrical surface, friction band means mounted on said cylindrical surface, and motor means for rotating the surface simulation member, a sub- frame mounted adjacent the surface simulation member, the sub-frame mounting at least one wheel testing unit wherein the wheel testing unit includes a carriage movable in a radial axis to and from the surface simulation member, the carriage mounting an individual vehicle wheel suspension including a tire, a wheel hub, a brake, and suspension damping means whereby the carriage can move towards and away from the surface simulation member to bring the tire in contact with the friction band means on the surface simulation member and tangentially thereto, and means are provided for varying the position of the carriage, the relative speed of the simulation member, and the application or release of the brakes in order to simulate virtual running and braking conditions of the vehicle wheel suspension.

2. The vehicle brake testing dynamometer as defined in claim 1 wherein the friction band means is a replaceable flexible sheet containing grit.

3. The vehicle brake testing dynamometer as defined in claim 1 or 2 wherein the surface simulating member includes a hub fixed to a driven shaft, a web extending radially from the hub and a cylindrical rim having an annular peripheral surface on which the friction band means is mounted.

4. The vehicle brake testing dynamometer as defined in claim 1, 2 or 3 wherein there four vehicle testing units spaced apart about the periphery of the surface simulating member and each of the vehicle testing units are located about the surface simulating member with the respective carriage movable radially to and from the surface simulating member.

5. The vehicle brake testing dynamometer as defined in claim 4 wherein the sub frame includes a ramp with rails on which said carriage is meant to slide radially relative to said surface simulating member so that said tire comes into contact with said friction band and each said wheel testing unit includes a shaft journaled for rotation in bearings on said carriage and a bracket is mounted on the shaft for rotation therewith about an axis parallel to said driven shaft mounting said surface simulating member, the bracket mounting said suspension elements including said shock absorber, said brake and said tire.

6. The vehicle brake testing dynamometer as defined in claim 5 wherein an arm is fixed to the shaft for rotation therewith and the arm is connected to a load cell for measuring the torque experienced by the respective wheel-testing unit.

7. The vehicle brake testing dynamometer as defined in claim 1 wherein a ventilation housing surrounds the surface simulating member and said wheel testing unit such that air can be circulated pass the tires thereby simulating road airflow.

8. The vehicle brake testing dynamometer as defined in claim 7 wherein there are two pairs of wheel testing units one pair on either half sector of the surface simulating member and the ventilation housing includes a pair of ducts passing over said respective half sectors of said surface simulating member with one pair of said wheel testing units being surrounded by a respective duct. - 10 -

9. The vehicle brake testing dynamometer as defined in claim 8 wherein an exhaust duct communicates with a portion of the ventilation duct downstream of the wheel testing units.

10. The vehicle brake testing dynamometer as defined in claim 3, wherein the driven shaft is journaled in bearings and the shaft is driven by motor having a pulley mounting drive shaft suspended in a pivoting cradle having its pivot axis coincident with the pulley mounting drive shaft and a timing belt extends about the pulley of said pulley mounting drive shaft and a greater pulley mounted on said driven shaft such that the cradle will swing in response to a sudden surge on the driven shaft .