EP0991857B1 - Decelerator device mounted in the exhaust gas circuit of a vehicle equipped with a combustion engine - Google Patents

Abstract

A decelerator device for obtains constant and maximal decelerating power whatever the engine speed, by controlling the pressure of the gases upstream of the valve by balancing the efforts at the actuator cylinder rod. The decelerator device (1) includes a balancing device (25) incorporated in the actuator cylinder (9), cylinder rod (12) dissociated from the piston (11) and a calibrated spring member (26) mounted between them. When the valve (7) is closed and, based on a counter-pressure predetermined by the spring member calibration, the actuator rod (12) moves back by stroke C' which causes the valve (7) to open by an angle prop generating a leakage of the exhaust gases. Beyond the. threshold, the valve (7) reopening angle varies according the exhaust gas pressure thereby ensuring a constant and maximal counter-pressure whatever the engine speed. The invention is applicable to combustion engines and in particular to industrial vehicles.

Description

The present invention relates to a retarder device mounted in the exhaust gas circuit of a vehicle equipped with a combustion engine, comprising at least one valve provided with a movable shutter and a control cylinder for this shutter, this cylinder comprising a movable piston provided with a rod coupled to said movable shutter, and comprising at least one device for balancing the back pressure exerted by the shutter on the gases, this balancing device being arranged to come into action when the shutter (7) is in the closed position and from a predetermined back pressure threshold and to reopen the shutter (7) with a reopening degree I as soon as the back pressure reaches said threshold, so as to create an appropriate exhaust gas leakage rate to regulate this back pressure regardless of engine speed.

This type of retarder is well known in particular in the field of industrial vehicles equipped with a combustion engine. Given their high inertia, these vehicles require, in addition to their own braking system, a retarder device housed in the exhaust gas circuit, preferably between the engine and the silencer, and generally mounted at the outlet of the turbocharger. powered by the exhaust manifold. It is usually controlled by a pedal actuated by the driver's left foot to prevent the driver from disengaging at the same time. This retarder device generates a back pressure in the exhaust circuit. This back pressure is higher or lower depending on the position of the shutter and its degree of reopening. It has the effect of slowing down the engine and therefore of completing the braking of the vehicle. The higher the back pressure, the more effective the deceleration. However, this back pressure must be limited to the maximum set pressure allowable by the exhaust manifold, in order to avoid reopening of the intake valves. This back pressure naturally depends on the pressure of the exhaust gases exerted on the shutter which is an asymptotic function of the engine speed. Consequently, for each engine speed corresponds a level of back pressure and therefore a level of deceleration. We are currently trying to make this function constant and at most equal to the maximum admissible set pressure whatever the engine speed and at low speeds, in order to optimize the deceleration.

One of the techniques proposed is described in publication EP-A-536,284 in which an exhaust modulator device comprises, in a shutter flap, two leakage holes closed by leaf springs having different rigidities. When a first level of back pressure is reached, a first leaf spring opens a first leak hole and releases part of the exhaust gases. When a second level of back pressure is reached, the second leaf spring opens a second leak hole, thereby increasing the flow of exhaust gases. This device makes it possible to limit the back pressure but generates deceleration stages. It is therefore not optimal. In addition, the leaf springs are subjected to temperature constraints and the aggression of exhaust gases. As a result, their operation degrades over time, thus affecting their opening and closing performance. In fact, with the heat of the exhaust gases, the leaf springs will lose their stiffness and the holes will always remain open, thus reducing the back pressure and the efficiency of the deceleration. In addition, the modulation system being integrated into the shutter, it is impossible to offer it in after-sales to equip retarder devices already in operation.

Another technique is described in publication FR-A-2 481 367 which provides a device for balancing the back pressure mounted at the end of the cylinder rod and coupled to the shutter lever by a ball joint. This device is therefore arranged outside and overhanging. It is therefore subject to external aggressions from the engine environment, namely splashing water, mud, salt, oil, etc. In addition, it represents a non-negligible mass at the end of the rod, a source of premature wear of the jack and risk of breaking the rod, but also generating a considerable increase in the inertia of this rod, therefore opening times and closing the retarder. This device requires a specific adaptation part on the rod of the jack, the latter being guided in translation only over a very short range which can generate a risk of blockage.

The publication US-A-4,669,585 describes a technique similar to that above but adapted to a knife gate valve, whose overall height is much greater than that of a butterfly valve. The counterpressure balancing device comprises an opening in the shutter closed by a plate coupled to the end of an actuator rod which can slide in the piston against the action of a spring when the back pressure reaches a certain threshold. This plate offers the exhaust gas only a small contact surface, which reduces the efficiency of the retarder. In addition, this device is directly subjected to the attacks of exhaust gases and can, therefore, seize up or be damaged prematurely, which reduces the reliability of the device. This device is also complex and expensive to implement. It also undergoes parasitic forces, the back pressure acting perpendicular to the movement of said plate further reducing the efficiency and reliability of the device.

The object of the present invention is to improve current retarder devices by proposing a simple, compact backpressure balancing device, of a reduced cost, making it possible to obtain constant and maximum deceleration performance whatever the engine speed while guaranteeing reliability and operating stability over time, without risk of degradation due to aggression from exhaust gases and high temperature, protected from any aggression external to the engine (water splashes , sludge, salt, oil, etc.), and without affecting the inertia of the retarder and therefore the efficiency of opening and closing the shutter. Another aim is to be able to easily and at low cost equip the retarder devices already in service by an after-sales marketing.

This object is achieved by a retarder device as defined in the preamble and characterized in that the balancing device is integrated and housed in the control cylinder and disposed between the movable piston and the cylinder rod, said rod being arranged to be move a stroke C 'relative to said movable piston, this stroke C' corresponding to the degree of reopening I and being controlled by at least one calibrated spring member disposed between said movable piston and said rod.

Thus, the control of the gas pressure upstream of the shutter is achieved by balancing the forces at the level of the control cylinder. As a result, the pressure balancing function is delocalized from the retarder function and integrated into the cylinder, allowing the balancing device not to be exposed both to the aggression of the gases and to their high temperature existing in the exhaust system, and to the engine environment subjected to external aggressions (projections of various kinds) and thus ensure efficient and reliable long-term operation.

The piston can comprise a coaxial cavity and the rod can comprise a head housed in said cavity, the calibrated spring member being disposed in the cavity at the rear of the head.

Preferably, the piston consists of two assembled parts, the cavity extending inside the two parts.

Advantageously, the spring member is calibrated to a value such that it compresses from a force corresponding to said predetermined back pressure threshold.

The maximum stroke C ′ of the cylinder rod can be between 0 and 10 mm and is preferably equal to 5 mm.

In the preferred embodiment, the shutter is rotatable and the degree of reopening I is an angle α, the maximum value of which is between 0 and 20 ° and preferably equal to 10 °.

Advantageously, the cavity has a length at least equal to the sum of the length of the compressed calibrated spring member, the thickness of the head of the rod and the maximum stroke C ′ of the rod.

In the preferred embodiment, the axis of rotation A of the shutter is distinct from the axis of symmetry B of said shutter by an interval d, this interval d being between 0.5 and 5 mm.

Advantageously, the jack has two separate bearings, arranged to guide the rod axially, one bearing being provided in the piston and the other bearing in a fixed ring which closes the jacketing of the jack.

• la figure 1 représente une vue d'ensemble en perspective d'un dispositif ralentisseur selon l'invention monté à la sortie d'un turbocompresseur,
• la figure 2 est une vue en coupe axiale du dispositif ralentisseur selon l'invention, et
• les figures 3 à 5 sont des vues de dessus en coupe montrant le dispositif ralentisseur respectivement au repos - l'obturateur ouvert, au travail - l'obturateur fermé et en équilibre - l'obturateur légèrement ouvert.

The present invention and its advantages will be better understood in the following description of an embodiment given by way of nonlimiting example and with reference to the appended drawings, in which:

• FIG. 1 represents an overall perspective view of a retarder device according to the invention mounted at the outlet of a turbocharger,
• FIG. 2 is a view in axial section of the retarder device according to the invention, and
• Figures 3 to 5 are top views in section showing the retarder device respectively at rest - the shutter open, at work - the shutter closed and balanced - the shutter slightly open.

With reference to FIG. 1, the retarder device 1 according to the invention is conventionally mounted in the exhaust circuit of a generally industrial vehicle and equipped with a combustion engine, at the outlet of a turbocharger TC supplied by an EC exhaust manifold which recovers the gases from said engine (not shown).

With reference to FIG. 2, the retarder device 1 comprises a valve 2 controlled by a control member 3. The valve 2 comprises a body 4 defining a channel 5 for the passage of the exhaust gases in the direction of the arrows F and a bore 6 for a movable shutter 7 mounted in said body 4 transversely to said channel 5 intended to retain the gases upstream when it is in the closed position. The body 4 has at its ends two mounting flanges 4a, 4b intended to receive, upstream, a corresponding flange of the turbocharger TC and, downstream, a corresponding flange of the exhaust duct (not shown). Of course, depending on the type of retarder, the mounting flanges 4a, 4b can be replaced by any other equivalent device, such as clamps, etc. The movable shutter 7, which is shown. is a butterfly flap mounted on a shaft 8 of axis A, this shaft having an upper end which passes through said body 4 to be coupled to said control member 3. It will be noted that the axis A corresponding to the axis of rotation of the flap butterfly 7 is distinct from the axis of symmetry B of said flap and distant by an interval d which may vary from 0.5 to 5 mm depending on the size of the retarder. The reasons for this misalignment will be explained later. Of course, any other form of shutter is possible such as a bushel, a ball or a drawer. The body 4 of the valve 2 comprises a vacuum cellar 4 'which consists of a bent conduit produced by molding inside the body and located on the passage of the shaft 8. This conduit has a blind upstream end disposed near the shaft 8 and a downstream end opening into the channel 5 downstream of the shutter. It provides effective sealing of the retarder 1 between the shaft 8 and the body 4. In fact, when the shutter 7 is closed, if exhaust gases seep between these two parts, they are automatically diverted and evacuated by the duct 4 ', which by the difference in pressure between the upstream and downstream of the shutter acts as a vacuum cleaner, hence its name: vacuum cellar.

The control member 3 is a jack 9, which can be hydraulic, pneumatic or electric, arranged outside said body 4 and therefore not subject to exhaust gases. This jack 9 is mounted on a support 10 by a screw-nut system 9 'defining a fixed axis D and comprises an internal movable piston 11 (cf. Fig. 3 to 5) provided with an external rod 12 coupled to the shaft 8 of the shutter 7 by a ball joint 13 and a lever 14, the ball joint 13 defining an axis of articulation E. In top view (cf. Fig. 3 to 5), the points corresponding to axes A, D and E define a triangle which determines the opening and closing kinematics of the butterfly flap 7 as well as the lengths of the lever 14 and of the rod 12 of the jack. In no case should these points be aligned. The support 10 of the jack 9 is positioned on the body 4 of the valve 2 and a seal 10 'is provided around the shaft 8 to further avoid any risk of leakage of the exhaust gases outside the retarder 1.

The retarder device 1 is controlled by the driver of the industrial vehicle by means of a control pedal. In normal vehicle operation, the retarder device 1 is at rest, so the shutter 7 is open (see Fig. 3) letting the gases escape freely. During braking, the jack 9 is supplied with a pressurized fluid, the rod 12 extends and causes the shutter 7 to close (cf. FIG. 4) thus retaining the gases and generating a back pressure which causes the engine slowing down and therefore a decrease in vehicle speed. It should be noted that even in the closed position, the shutter 7 lets escape a reduced flow of exhaust gases to avoid any risk of blockage and dangerous overpressure for the equipment located upstream.

FIGS. 3 to 5 illustrate the different positions of the retarder device 1 in top view with the representation in section of the control jack 9.

Figure 3 shows the retarder device 1 in its rest position. The jack is not supplied, the piston 11 is located near the orifice 15 for supplying the pressurized fluid, the rod 12 is retracted and the shutter 7 is in the open position, that is to say oriented in parallel the flow of exhaust gases.

Figure 4 shows the retarder device 1 in its working position. The jack 9 is supplied with power, the piston 11 moves in one stroke C, the rod 12 comes out of the same stroke C, causing the shutter 7 to pivot a quarter turn. The shutter 7 is then in the closed position, that is to say oriented perpendicular to the flow of the exhaust gases and generating the back pressure. As explained above, the shutter 7 and the bore 6 of this shutter are arranged to allow a very small gas leak to escape. The piston 11 is mounted in the jacket of the jack 9 by an O-ring 16 ensuring sealing and on the rod 12 by a bearing 17. A fixed ring 18 closes the jacket of the jack 9 and guides the rod 12 in a bearing 19. This rod 12 is therefore guided axially at its two ends by the two bearings 17, 19, which are self-lubricated and which provide it with a sufficient guide surface to ensure a uniform movement, always in the axis and without risk of blockage. . Two superposed return springs 20, 21, placed in opposition and coaxial are provided between this fixed ring 18 and the piston 11 to return the piston 11 to the rest position as soon as the supply of the pressurized fluid stops. These two return springs 20, 21 can also be replaced by a single return spring or by any equivalent means, depending on the type of retarder. The piston 11 is limited in its stroke by a stop formed when the two bearings 17, 19 come into contact, the return springs 20, 21 being compressed. These return springs 20, 21 are determined so that by being compressed, their turns are never contiguous, in order to limit the fatigue of these springs and to prevent them from forming said stop on their own. These return springs 20, 21 are mounted and guided on corresponding shoulders 11 ', 11 "and 18', 18" provided respectively on the piston 11 and the fixed ring 18.

FIG. 5 represents the retarder device 1 in its equilibrium position. The jack 9 is always supplied with the pressurized fluid, the piston 11 is in the same position as that of FIG. 4 and the rod 12 is extended. However, the gas pressure upstream of the shutter 7 has increased beyond a back pressure threshold, which is at most equal to the maximum admissible back pressure value and which is determined by a balancing device 25 described below and authorizing partial reopening and limited to a degree of reopening I of the shutter 7 to create a greater gas leakage. In this configuration of the retarder device 1, whatever the engine speed, the shutter 7 is placed in an equilibrium position limited by its degree of reopening I ensuring a constant and maximum deceleration effect since it corresponds to the counter - predetermined set pressure which can be the maximum admissible back pressure by the CE exhaust manifold.

The balancing device 25 is integrated and housed in the cylinder 9. It comprises the rod 12 of the cylinder which is dissociated from the piston 11 and a calibrated spring member 26 interposed between the rod and the piston. The calibrated spring member 26 is, in this case, a compression spring but can be constituted by any other suitable spring element. A cavity 27 is provided coaxially in the piston 11 to receive said spring member 26 and the corresponding end of the rod 12 forming a head 28 with a diameter greater than that of the rod. The cavity 27 has a length at least equal to the sum of the length of the calibrated compressed spring member 26, the thickness of the head 28 of the rod and a stroke C 'corresponding to the recoil stroke of the rod 12. The integration of the balancing device 25 in the jack 9 requires the realization of the piston 11 in two parts 11a, 11b assembled by screwing or any other equivalent means such as for example crimping, the cavity 27 being provided for interior of the two parts.

In the normal position, the spring member 26 pushes the rod 12 which is stopped in translation by its head 28 while pressing on the bottom of the cavity 27. This spring member 26 is calibrated to resist a compressive force corresponding to the counter threshold -pressure predetermined at the shutter 7, equal to or less than the maximum permissible back pressure by the CE exhaust manifold. Beyond this threshold. the spring member 26 is compressed and allows the rod 12 of the stroke C ′ to retreat under the effect of the pressure of the exhaust gases exerted on the shutter 7. For this purpose. and as mentioned previously, the axis of rotation A of the shutter 7 is off-axis with respect to its axis of symmetry B, thus creating a torque allowing its reopening under the thrust force caused by the exhaust gases. The stroke C ′ of the rod 12 authorizes the reopening of the shutter 7 by a degree of reopening I, corresponding in this case, to an angle α, thus generating a greater leakage rate of the exhaust gases. The maximum stroke C ′ is delimited by the part 11a of the piston and the head 28 of the rod when this head 28 abuts at the bottom of the cavity 27.

Depending on the type of retarder, it can be between 0 and 10 mm and preferably equal to 5 mm, which corresponds to a maximum degree of reopening I whose maximum angle α is between 0 and 20 ° and preferably equal at 10 °.

Then, whatever the engine speed, this reopening angle α varies as a function of the exhaust gas pressure between its minimum and maximum values, 0 and 10 ° for example, which guarantees constant back pressure and at most equal to the maximum set pressure allowed by the CE exhaust manifold. This balancing device 25 therefore makes it possible to control the pressure of the gases upstream of the shutter by balancing the forces at the level of the rod 12 of the jack 9.

It is clear from this description that the invention makes it possible to improve current retarder devices by proposing a balancing device 25 simple, inexpensive, efficient, compact and incorporated in the control jack 9 which is delocalized with respect to the circuit. exhaust. The retarder and balancing functions are thus dissociated. As a result, the control cylinder 9 equipped with the balancing device 25 and the balancing device itself are neither subjected to high temperatures and to aggressions from the exhaust gases, nor to aggressions external to the engine. The balancing device 25 being integrated into the jack 9 does not generate any parasitic load on the rod of the jack which can have a negative influence on its reaction time when the shutter is opened and closed. In addition, it can be offered after-sales to equip existing retarder devices and can be set up very easily without the need to dismantle valve 2.

Claims (10)

1. Decelerator device (1) mounted in the exhaust gas circuit of a vehicle equipped with a combustion engine, comprising at least one valve (2) provided with a movable shutter (7) and an actuator cylinder (9) for this shutter, this cylinder comprising a movable piston (11) provided with a rod (12) coupled to said movable shutter (7), and comprising at least one device (25) for balancing the back pressure exerted by the shutter on the gas, this balancing device being designed to come into action when the shutter (7) is in the closed position and when a predetermined back pressure threshold is reached and reopen the shutter (7) to a degree of reopening I as soon as the back pressure reaches said threshold, so as to create a suitable exhaust gas leak rate in order to regulate this back pressure whatever the engine's speed, characterized in that the balancing device (25) is incorporated and located into the actuator cylinder (9) and arranged between the movable piston (11) and the rod (12) of the said cylinder, the said rod (12) being designed to move at a stroke C' in relation to the movable piston (11), this stroke C' corresponding to the degree of reopening I and being controlled by at least one calibrated spring device (26) arranged between the said movable piston (11) and the said rod (12).
2. Device according to claim 1, characterized in that the piston (11) comprises a coaxial cavity (27) and in that the rod (12) comprises a head (28) housed in said cavity, the calibrated spring device (26) being arranged in the cavity at the rear of the head.
3. Device according to claim 2, characterized in that the piston (11) is comprised of two assembled parts (11a, 11b), the cavity (27) extending inside the two parts.
4. Device according to claim 2, characterized in that the spring device (26) is calibrated to such a value that it is compressed when a force corresponding to said predetermined back pressure threshold is reached.
5. Device according to claim 1, characterized in that the maximum stroke C' of the cylinder's rod (12) is between 0 and 10 mm and equal to 5 mm.
6. Device according to claim 5, characterized in that the shutter (7) is rotary and in that the degree of reopening I is an angle α, the maximum value of which lies between 0 and 20° and is equal to 10°.
7. Device according to claim 2, characterized in that the length of the cavity (27) is at least equal to the sum of the length of the calibrated spring device (26) when compressed, the thickness of the rod's head (28) and the maximum stroke C' of the rod (12).
8. Device according to claim 6, characterized in that the axis of rotation (A) of the shutter (7) is distinct from the axis of symmetry (B) of said shutter by a gap (d).
9. Device according to claim 8, characterized in that the gap (d) is between 0.5 and 5 mm.
10. Device according to the any of the previous claims, characterized in that the cylinder (9) comprises two distinct bearings (17, 19), designed to guide the rod (12) axially, the bearing (17) being provided in the piston (11) and the bearing (19) in a fixed ring (18) which closes the cylinder's liner (9).