Hydraulic system, device for flushing a hydraulic system, method for flushing a hydraulic system and control circuit for controlling a hydraulic system

Abstract

Hydraulic system (100), comprising: a pump (104); a pump reservoir (106); a supply line (101) fluidly coupling a fluid tank (102) to the pump (104), wherein the supply line (101) is constructed to receive a fluid from the fluid tank (102); a valve (108) in fluid communication with the pump reservoir (106); a pressure line (103) fluidly coupling the pump reservoir (106) to the valve (108); a timing reservoir (110) having a flow opening (112; 212); and a return line (105; 205) designed to fluidly connect the pump reservoir (106) to the fluid tank (102) via the timing reservoir (110), wherein the hydraulic system (100) is adapted to switch between a normal state and a flushing state, wherein in the normal state: the pump (104) is switched on, a first part of the fluid from the fluid tank (102) is supplied via the pressure line (103) from the pump reservoir (106) to the valve (108) and a second part of the fluid from the pump reservoir (106) is supplied through the return line (105; 205) via the flow opening (112; 212) and the timing reservoir (110) to the fluid tank (102), and where in the flushing state: a first negative pressure is created at an outlet of the pump (104), the first negative pressure generating a second negative pressure in the pump reservoir (106), in the valve (108) and in the pressure line (103), the second negative pressure flushing the valve (108) and the pressure line (103) in a first time after the pump (104) is switched off, and a third negative pressure is created in the return line (105; 205), the third negative pressure drawing fluid from the return line (105; 205) via the timing reservoir (110) and the flow opening (112; 212) into the pump reservoir (106); the third negative pressure also drawing air from the fluid tank (102) into the pump reservoir (106) for a second time after the pump (104) is turned off, thereby purging the return line (105; 205); the second time being longer than the first time; the first negative pressure continuing to draw fluid into the fluid tank (102) and purge the pump reservoir (106) with the air for a third time after the return line (105; 205) has been purged; wherein flushing the pump reservoir (106) fills the valve (108), the pressure line (103) and the pump reservoir (106) with air to atmospheric pressure so that no fluid remains in the pump reservoir (106).

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to hydraulic systems for use with exhaust aftertreatment systems, more particularly to a hydraulic system, an apparatus for purging a hydraulic system, a method for purging a hydraulic system, and a control circuit for controlling a hydraulic system. BACKGROUND

[0002] Exhaust aftertreatment systems are used to capture and treat exhaust gas produced by internal combustion (IC) engines. Conventional exhaust aftertreatment systems include any number of different components to reduce the proportion of harmful exhaust emissions in the exhaust. For example, certain exhaust aftertreatment systems for diesel-powered internal combustion engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and NO2 in minor proportions) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3).

[0003] Generally, an exhaust reductant (e.g., a diesel emissions fluid such as urea) is injected into the aftertreatment system and mixed with the exhaust gas. The exhaust reductant may provide a source of ammonia to facilitate at least a partial reduction of the NOx gases contained in the exhaust gas. The byproducts of the reduction of the exhaust gas are then fluidly delivered to the catalyst included in the SCR aftertreatment system. The catalyst essentially decomposes all of the NOx gases into relatively harmless byproducts, which are exhausted from such prior art SCR aftertreatment systems.

[0004] Generally, hydraulic systems are used to pump the liquid exhaust reductant into the SCR system. In conventional hydraulic systems, the exhaust reductant (e.g., a diesel emissions fluid such as urea) can crystallize at the tip of dosers or nozzles designed to deliver the exhaust reductant into the SCR system. This impedes gas flow in a pressure line connected to the nozzle, resulting in significant negative pressure and a high vacuum. Immediately after completing a system purge, the high vacuum is relieved by drawing exhaust reductant from an exhaust reductant storage tank.

[0005] During purging, the system is filled with warm gas from the vehicle's exhaust system. In cold weather conditions, the warm purge gas cools after shutdown, resulting in a reduction in volume. This creates negative pressure after the system is shut down, drawing exhaust reductant from the storage tank into the pump. The exhaust reductant can freeze in the pump. The expansion of the frozen fluid can then lead to malfunctions and / or cracks in the pump.

[0006] WO 2014 / 149289 A1 relates to an air reintroduction device comprising a bypass valve that reduces the pressure in an accumulator storing reductant to less than an air supply pressure of an air supply. The device also comprises a metering valve that fills the accumulator with air from the air supply at the air supply pressure and a pump that pumps reductant into the accumulator.

[0007] DE 102011 076 429 A1 relates to a dosing system, in particular for an SCR catalyst of an internal combustion engine, comprising a dosing agent tank, a pump in which a reversal of the pumping direction can be effected by reversing the direction of rotation of the pump motor, which pump is connected to the dosing agent tank by means of an intake line, a first filter which has an ice pressure compensation element and which is connected to the pump by means of a connecting line, a dosing valve which is connected to the filter by means of a pressure line, a pressure sensor which is arranged in the pressure line, a return line which is connected to the pressure line at a first connection point and ends in the dosing agent tank, a first check valve which is arranged in the connecting line, a first throttle which is arranged between the pressure sensor and the first filter in the pressure line, a return line,which is connected to the connecting line at a second connection point between the pump and the first filter and to the pressure line at a third connection point between the pressure sensor and the first throttle, and a second check valve which is arranged in the return line. SUMMARY

[0008] Embodiments described herein generally relate to hydraulic systems for use with exhaust aftertreatment systems. More particularly, various embodiments relate to exhaust reductant delivery systems that include a timing reservoir and a flow orifice and are configured to facilitate purging of a pressure line, a return line, and a pump reservoir of the exhaust reductant delivery system upon system shutdown. Purging is intended to ensure that no exhaust reductant remains in a pump reservoir after the system is shut down. In certain embodiments, the flow orifice is configured to facilitate bidirectional flow of the exhaust reductant.

[0009] In a first set of embodiments, a hydraulic system includes a fluid tank containing a fluid, a pump, and a pump reservoir. A supply line fluidly couples the fluid tank to the pump. A valve is in fluid communication with the pump reservoir. A pressure line fluidly couples the pump reservoir to the valve. The hydraulic system also includes a timing reservoir including a flow port and a return line fluidly coupling the pump reservoir to the fluid tank via the timing reservoir.

[0010] The hydraulic system is designed to alternate between a normal state and a flushing state. In the normal state, the pump is turned on and a first portion of fluid is delivered from the pump reservoir via the pressure line to the valve. A second portion of fluid is delivered from the pump reservoir through the return line via the flow orifice and the timing reservoir to the fluid tank. In the flushing state, a first negative pressure develops at an outlet of the pump. The first negative pressure creates a second negative pressure in the pump reservoir, the valve, and the pressure line. The second negative pressure flushes the valve and the pressure line for an initial time after the pump is turned off. Furthermore, a third negative pressure develops in the return line. The third negative pressure draws fluid from the return line via the timing reservoir and the flow orifice into the pump reservoir.The third negative pressure continues to draw air from the fluid tank into the pump reservoir for a second time from the time the pump is turned off, which is longer than the first time, so that the return line is flushed. The first negative pressure continues to draw fluid from the pump reservoir into the fluid tank for a third time after the return line is flushed, and the pump reservoir is flushed with air. By flushing the pump reservoir, the valve, the pressure line, and the pump reservoir are filled with air to atmospheric pressure so that no fluid remains in the pump reservoir. In certain embodiments, at least one of the timing reservoir, the flow orifice, and the return line is configured so that the second time is longer than the first time.

[0011] In a second set of embodiments, an apparatus for flushing a hydraulic system comprises a fluid tank containing a fluid, a pump, a pump reservoir, a supply line fluidly coupling the fluid tank to the pump, a valve in fluid communication with the pump reservoir, and a pressure line fluidly coupling the pump reservoir to the valve. The apparatus comprises a timing reservoir including a flow opening. A return line fluidly couples the pump reservoir to the fluid tank via the timing reservoir. The apparatus is configured to enable the hydraulic system to transition between a normal state and a flush state. In the normal state, the pump is switched on, and a first portion of fluid is delivered from the pump reservoir to the valve via the pressure line.A second portion of fluid is delivered from the pump reservoir through the return line, via the flow orifice, and the timing reservoir to the tank. In the purge state, a first negative pressure develops at an outlet of the pump. The first negative pressure creates a second negative pressure in the pump reservoir, valve, and pressure line. The second negative pressure purges the valve and pressure line for a first time after the pump is turned off. A third negative pressure develops in the return line. The third negative pressure draws fluid from the return line, via the timing reservoir and flow orifice, into the pump reservoir. The third negative pressure continues to draw air from the fluid tank into the pump reservoir for a second time after the pump is turned off, thus purging the return line.The first negative pressure continues to draw fluid into the fluid tank for a third time after the return line is flushed, and the pump reservoir is flushed with air. Flushing the pump reservoir fills the valve, pressure line, and pump reservoir with air to atmospheric pressure, leaving no fluid in the pump reservoir. At least one of the timing reservoir, flow port, and return line is designed so that the second time is longer than the first time.

[0012] In a third set of embodiments, a method for flushing a hydraulic system including a fluid tank, a pump, a pump reservoir, a supply line fluidly coupling the fluid tank to the pump, a valve in fluid communication with the pump reservoir, a pressure line fluidly coupling the pump reservoir to the valve, a return line, a timing reservoir, and a flow orifice comprises activating the pump to operate the hydraulic system in a normal state. The pump reservoir is fluidly coupled to the fluid tank through the timing reservoir and the flow orifice via the return line. A first portion of fluid is delivered from the pump reservoir to the valve via the pressure line. A second portion of fluid is delivered from the pump reservoir to the tank through the return line via the flow orifice and the timing reservoir.The pump is deactivated to operate the hydraulic system in a purge condition in which a first negative pressure develops at an outlet of the pump. The first negative pressure creates a second negative pressure in the pump reservoir, valve, and discharge line. The second negative pressure purges the valve and discharge line for a first time after the pump is deactivated. A third negative pressure develops in the return line. The third negative pressure draws fluid from the return line through the timing reservoir and flow orifice into the pump reservoir. The third negative pressure continues to draw air from the fluid tank into the pump reservoir for a second time from the pump is deactivated, which is longer than the first time, thus purging the return line.After flushing the return line, the first negative pressure continues to draw fluid into the fluid tank for a third period of time, flushing the pump reservoir with air. Flushing the pump reservoir fills the valve, pressure line, and pump reservoir with air to atmospheric pressure, so no fluid remains in the pump reservoir.

[0013] In a fourth set of embodiments, a control device for controlling the hydraulic system to enable flushing thereof comprises a control device, wherein the hydraulic system comprises a fluid tank containing a fluid, a pump, a pump reservoir, a supply line fluidly coupling the fluid tank to the pump, a valve in fluid communication with the pump reservoir, a pressure line fluidly coupling the pump reservoir to the valve, a return line, a timing reservoir, and a flow opening. The control device is configured to be operatively connected to the hydraulic system and to control the operation thereof to enable the hydraulic system to transition between a normal state and a flushing state. In the normal state, the control device activates the pump so that a first portion of the fluid is delivered from the pump reservoir to the valve via the pressure line.A second portion of fluid is delivered from the pump reservoir through the return line, via the flow orifice, and the timing reservoir to the tank. In the purge state, the controller deactivates the pump, causing a first negative pressure to develop at an outlet of the pump. The first negative pressure creates a second negative pressure in the pump reservoir, valve, and pressure line. The second negative pressure purges the valve and pressure line for a first time after the pump is turned off. Furthermore, a third negative pressure develops in the return line. The third negative pressure draws fluid from the return line, via the timing reservoir and flow orifice, into the pump reservoir. The third negative pressure continues to draw air from the fluid tank into the pump reservoir for a second time after the pump is turned off, purging the return line.The first negative pressure continues to draw fluid into the fluid tank and flush the pump reservoir for a third time after flushing the return line. Flushing the pump reservoir fills the valve, pressure line, and pump reservoir with air to atmospheric pressure, so no fluid remains in the pump reservoir.

[0014] It should be understood that all combinations of the foregoing concepts and other concepts discussed in more detail below (provided these concepts are not mutually incompatible) are intended to be part of the inventive subject matter disclosed herein. In particular, all combinations of the claimed subject matter listed at the end of this disclosure are intended to be part of the inventive subject matter disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing and other features of the present disclosure will become more apparent from the following description and appended claims, which should be read in conjunction with the accompanying drawings. While these drawings merely illustrate several embodiments in accordance with the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described in greater detail and particularity using the accompanying drawings. Fig. 1 is a schematic diagram of an embodiment of a hydraulic system in a normal state. Fig. 2 is a schematic sketch of the hydraulic system of Fig. 1 in a flushing state in which the pressure line is flushed. Fig. 3 is a schematic sketch of the hydraulic system of Fig. 1 in the flushing state, in which the return line is flushed. Fig. 4 is a cross-sectional view of one embodiment of a return port for use in the system of Fig. 1, wherein the return port has a check valve which is removed before the return port is introduced into the hydraulic system of Fig. 1 is inserted. Fig. Figure 5 is an illustration of another embodiment of a return line for use in the system of Fig. 1, wherein the return line is arranged in a racetrack configuration to enable flushing of a pressure line before flushing the return line. Fig. 6 is a graph of pressure curves after a pump shutdown of a pressure line included in an exemplary hydraulic system similar to the hydraulic system of Fig. 1 is largely similar, which has the return connection of Fig. 4 with and without check valve included. Fig. 7A is a graph of a pressure profile after shutting down a pump of a pressure line of a hydraulic system including a return port with a check valve and a clogged nozzle, and Fig. Figure 7B is a graph of a pressure profile when the pressure line pump of the hydraulic system of Fig. 7A, but the check valve has been removed from the return connection. Fig. Figure 8 is a schematic flow diagram of an example method for flushing a hydraulic system.

[0016] Throughout the following detailed description, reference is made to the accompanying drawings. In the drawings, like symbols normally identify like components unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It is contemplated that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, may be arranged, substituted, combined, and designed in many different configurations, all of which are expressly contemplated and constitute a part of this disclosure. DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0017] Embodiments described herein generally relate to hydraulic systems, and more particularly, to exhaust reductant delivery systems having a timing reservoir and a flow orifice configured to facilitate purging of a pressure line, a return line, and a pump reservoir of the exhaust reductant delivery system upon system shutdown. Purging is intended to ensure that no exhaust reductant remains in a pump reservoir after the system is shut down. In certain embodiments, the flow orifice is configured to facilitate bidirectional flow of the exhaust reductant.

[0018] Specific embodiments described herein offer a number of advantages, such as: (1) a pressure line, a return line, and a pump reservoir of a hydraulic system are filled with air to atmospheric pressure; (2) any negative pressure is prevented from remaining in the pump reservoir after the hydraulic system has been shut down, thereby preventing any fluid (e.g.exhaust gas reductant) is drawn into the pump reservoir to prevent the fluid from crystallizing and prevent pump malfunction; (3) provide desired flushing characteristics by removing the check valve from the return port, providing a timing reservoir, and / or adjusting a length of the return line without the use of complex algorithms or electronic controls, and (4) enable conversion of conventional hydraulic systems into the hydraulic systems described herein with only minimal modifications.

[0019] Fig. 1-3 are schematic block diagrams of a hydraulic system 100 for delivering metered amounts of fluid in various operating conditions. In certain embodiments, the hydraulic system 100 may include an exhaust reductant delivery system configured to deliver metered amounts of the exhaust reductant to an aftertreatment system (not shown). The hydraulic system 100 includes a fluid tank 102, a pump 104, a pump reservoir 106, a valve 108, and a timing reservoir 110 including a flow orifice 112.

[0020] The fluid tank 102 is configured to store a volume of fluid. In certain embodiments, the hydraulic system 100 may include an exhaust reductant delivery system. In such embodiments, the fluid tank 102 stores a volume of an exhaust reductant formulated to facilitate reduction of a fluid flowing through the aftertreatment system. For example, the exhaust gas may include diesel exhaust, and the exhaust reductant may include a diesel emission fluid. Such diesel emission fluids may include an ammonia source, such as an aqueous urea solution (e.g., the diesel emission fluid available under the tradename ADBLUE®).

[0021] The pump 104 is fluidically (also referred to as flow-related) coupled to the tank 102 via a supply line 101. The pump 104 is the main drive, designed to pump the fluid through a hydraulic circuit of the hydraulic system 100. The pump 104 includes a pump reservoir 106. The pump reservoir 106 acts as an intermediate storage device for the fluid and enables controlled metering of the fluid into the valve 108.

[0022] The valve 108 is in fluid communication with the pump reservoir 106 via a pressure line 103. The valve 108 includes a one-way valve. In certain embodiments, the valve 108 may be included in an injector or doser configured to deliver an exhaust reductant (e.g., urea) to an aftertreatment system. In such embodiments, the injector may also include a nozzle or doser tip (not shown) configured to deliver the exhaust reductant to the aftertreatment system.

[0023] The hydraulic system 100 also includes a timing reservoir 110 that includes a flow opening 112. A return line 105 fluidly couples the pump reservoir 106 to the fluid tank 102 via the timing reservoir 110. In some embodiments, the return line 105 has a length (e.g., at least 1.25 meters) sufficient to allow the return line 105 to serve as the timing reservoir 110. In such embodiments, a return port that includes the flow opening 112 may be included in the hydraulic system 100 to fluidly couple the return line 105 to the pump reservoir 106. In this way, the hydraulic system 100 forms a closed hydraulic circuit. Furthermore, one end of the return line 105, which is coupled to the fluid tank 102, is arranged within the fluid tank 102 so as to be positioned above a surface of the fluid contained in the fluid tank 102.

[0024] In certain embodiments, the flow opening 112 does not include a check valve, so that the flow opening 112 allows bidirectional flow between the pump reservoir 106 and the fluid tank 102. For example, Fig. 4 is a cross-sectional view of a return port 211 that may be included in hydraulic system 100. Return port 211 includes a flow opening 212 and a check valve assembly, indicated by arrow D, that is removed from return port 211 before return port 211 is integrated into hydraulic system 100. In this manner, return port 211, and thus flow opening 212, may enable bidirectional flow between pump reservoir 106 and fluid tank 102.

[0025] The hydraulic system 100 is designed to switch between a normal state and a flush state. Fig. Figure 1 shows the hydraulic system operating in the normal state. In the normal state, pump 104 is turned on, and fluid is pumped by pump 104 from fluid tank 102 into pump reservoir 106. A first portion of the fluid is delivered from pump reservoir 106 via pressure line 103 to valve 108. For example, the first portion of the fluid may include a metered amount of an exhaust gas reductant to be delivered to the aftertreatment system through pressure line 103 and valve 108.

[0026] A second portion of the fluid is delivered through the return line 105 via the flow opening 112 and the timing reservoir 110 to the fluid tank 102, as indicated by arrow A in Fig. 1. The second portion of the fluid is significantly smaller than the first portion of the fluid. For example, the second portion of the fluid may include an excess amount of exhaust reductant remaining in the pump reservoir 106 after the first portion of the exhaust reductant has been delivered to the aftertreatment system through the valve 108. The second portion of the fluid is delivered back to the fluid tank 102 through the return line 105 to prevent any excess exhaust reductant from remaining in the pump reservoir 106.

[0027] When the hydraulic system 100 enters the flushing state, a first negative pressure develops in the pump 104 and thus at an outlet thereof. The first negative pressure creates a second negative pressure in the pump reservoir 106, the valve 108, and the pressure line 103. The second negative pressure flushes the valve 108 and the pressure line 103 for a first period of time. As the negative pressure develops, fluid is subsequently drawn from the pump 104 via the supply line 101 to the fluid tank 102. The first negative pressure results in the second negative pressure in the pump reservoir 106, the pressure line 103, and the valve 108. The second negative pressure in the pressure line 103 serves to draw the fluid into the pump reservoir 106 and flush the valve 108 and the pressure line 103, as indicated by arrow B in Fig. 2 is shown.

[0028] A third negative pressure develops in the return line, for example, due to the second negative pressure in the pump reservoir 106. The third negative pressure draws the exhaust reductant from the return line 105 via the timing reservoir 110 and the flow orifice 112 into the pump reservoir 106. When the remainder of the fluid has been drawn from the timing reservoir 110 and the flow orifice 112 into the pump reservoir 106, the third negative pressure continues to draw air from the fluid tank 102 into the pump reservoir 106. This purges the return line 105 for a second period of time. At least one of the timing reservoir 110, the flow orifice 112, and the return line 105 is configured such that the second period of time is greater than the first period of time, as described herein.In other words, the flushing of the pressure line 103 and the return line 105 starts at the same time, but the pressure line 103 is flushed first within the first time period, while the return line 105 continues to be flushed until the end of the second time period after the pressure line 103 has been flushed.

[0029] In some embodiments, the timing reservoir 110 is configured to hold a volume of fluid to enable flushing of the return line 105 after the pressure line 103 has been flushed. In such embodiments, the timing reservoir 110 serves as a hydraulic timing device to provide a delay in flushing of the return line 105 relative to the pressure line 103. In other embodiments, the flow opening 112 may have a diameter configured to enable flushing of the return line 105 after the pressure line 103 has been flushed. The diameter of the flow opening, the volume of the timing reservoir 110, and the viscosity of the fluid may enable timing of the flushing of the return line 105 such that the return line 105 is flushed after the pressure line 103 has been flushed.For example, the second negative pressure in the pressure line 103 and in the valve 108 may change from a relatively low value to a relatively high value when the last remaining fluid has been drawn through the flow opening 112 into the pump reservoir 106 and the less viscous air flows through the flow opening 112 (as described in more detail herein with reference to FIG. Fig. 6).

[0030] In still other embodiments, the return line 105 may be configured to have a length that allows a sufficient volume of fluid to be accommodated in the return line 105 to allow the pressure line 103 to be purged before the return line 105. For example, the length may be such that the return line 105 is purged after the pressure line 103 regardless of whether a nozzle or doser tip for delivering the exhaust reductant system to the aftertreatment system is permeable or blocked with deposited exhaust reductant. Fig. 5 shows an example of a return line 205 that can be used in hydraulic system 100. The return line 205 is arranged in a racetrack configuration so that the return line 205 can be compactly positioned within a hydraulic system (e.g., hydraulic system 100). To ensure that the emptying sequence is maintained, the volume of the timing reservoir 110 is designed to accommodate emptying of the pressure line while limiting gas entry from the doser / nozzle. The ratio between the volume of the return line 105 and the pressure line 103 is inversely proportional to the diameter of the flow orifice 112. In a specific embodiment, this ratio is in the range of 30-35% (including all intermediate ranges and values) (e.g., 33%). The volume of the return line 105 can be influenced by changing the length or diameter of the line.

[0031] After flushing the return line 105, the first pressure continues to draw fluid from the pump reservoir 106 into the fluid tank 102 to flush the pump reservoir with air for a third period of time after the return line 105 has been flushed. Flushing the pump reservoir 106 with air from the fluid tank 102 fills the valve 108, the pressure line 103, and the pump reservoir 106 with air to atmospheric pressure, so that no fluid remains in the pump reservoir 106. In other words, the hydraulic system 100 is calibrated such that the pressure line 103 is flushed before the return line 105, and such that after the return line 105 is flushed, there is sufficient negative pressure (e.g., the first negative pressure) in the hydraulic system 100 so that the flushing of the pump reservoir 106 can continue until no more fluid remains in the pump reservoir 106.Flushing the pump reservoir 106 with the air from the fluid tank 102 equalizes the pressure in the system to near ambient pressure so that no negative pressure remains in the system to draw fluid from the fluid tank 102 into the pump reservoir 106 after the pump 104 is turned off.

[0032] In this way, no fluid remains in the pump reservoir 108 after the pump is shut down. Thus, there is no opportunity for the fluid to freeze in the pump reservoir 106 under cold conditions, thereby eliminating pump malfunctions and failures. In certain embodiments, the pumping duration is adjusted to account for flushing the return line 105 prior to the pressure line 103.

[0033] Fig. 6 includes graphs of pressure profiles in the pressure line included in a hydraulic system when switching off the pump included in the hydraulic system. The hydraulic system can be the hydraulic system of Fig. 1-3 are essentially similar. The hydraulic system was used to pump diesel emission fluid. The hydraulic system includes the return connection of Fig. 4 with a flow opening with and without a check valve. The pressure profiles of the pressure line for the hydraulic system including the return port with a check valve and an open doser (i.e., an injector nozzle) and the hydraulic system including the return port without a check valve and an open doser (i.e., not clogged with diesel exhaust fluid deposits) are similar. However, the pressure in the pressure line included in the hydraulic system including the return port without the check valve reaches equilibrium near atmospheric pressure much more quickly after an initial negative pressure than in the system with the return port including the check valve.

[0034] If the check valve is present and the dosing device is clogged, the pressure in the discharge line drops to a significant negative pressure of -50 kPa, as can be seen from Fig. 6, and remains at this pressure for an extended period of time, even after the pump has been shut down. This prolonged negative pressure causes the exhaust reductant to be drawn into the pump reservoir after the pump has been shut down, which is harmful, as described herein.

[0035] If the check valve is missing and the dosing device is clogged, negative pressure is generated in the discharge line until time T1. This time is influenced by the pressure differential across the flow orifice, the size (e.g., diameter) of the flow orifice, and / or the viscosity of the fluid flowing through the flow orifice. In this way, the timing reservoir and the flow orifice can be used as a timing device to allow the discharge line to be flushed before the return line. Time T1 is sufficient to flush the discharge line and corresponds to the time until the last residue of diesel exhaust fluid has been drawn into the pump reservoir. At this time, the less viscous air drawn from the tank flows through the flow orifice, allowing the negative pressure in the discharge line to rise close to ambient pressure (from -50 kPa to -10 kPa).In other words, time T1 represents a change in an operating state of the hydraulic system, with the system's hydraulic circuit before T1 primarily flushing the discharge line, and the hydraulic circuit after T1 primarily flushing the pump assembly. After the pump is shut off, the flow orifice continues to draw air, effectively filling the pump reservoir and discharge line with air to ambient pressure, preventing any negative pressure in these components that could otherwise draw the exhaust reductant back into the pump reservoir.

[0036] Fig. 7A and Fig. 7B show in more detail various pressure profiles of a pressure line in different operating states of a hydraulic system including the timing reservoir and the flow orifice with and without the check valve. Fig. Figure 7A shows the pressure profiles under various operating conditions of the hydraulic system, which has the flow port with the check valve and where the dosing device is clogged. Once the pump is shut down, a significant negative pressure develops in the discharge line. This negative pressure (approximately -50 kPa) is maintained for an extended period after the pump is shut down, forcing a return flow of the exhaust reductant from the tank to the pump reservoir.

[0037] Conversely, if the check valve is removed from the flow orifice and the doser is clogged, a negative pressure (approximately -50 kPa) develops in the discharge line until the discharge line has been flushed, when the pump is turned off. The discharge line is completely flushed until time T1. The return line continues to flush until time T2, beyond the flushing of the discharge line. The pressure is reduced to approximately (-10 kPa) by time T3, while the pump reservoir continues to be flushed. At time T4, the system is completely flushed, and the pressure in the system rises to near atmospheric pressure.

[0038] Fig.8 is a schematic flow diagram of an example method 300 for flushing a hydraulic system (e.g., hydraulic system 100). The hydraulic system includes a fluid tank (e.g., fluid tank 102), a pump (e.g., pump 104), a pump reservoir (e.g., pump reservoir 106), a supply line (e.g., supply line 101) fluidly coupling the fluid tank to the pump, a valve (e.g., valve 108) in fluid communication with the pump reservoir, and a pressure line (e.g., pressure line 103) fluidly coupling the pump reservoir to the valve.

[0039] The method 300 includes providing a timing reservoir including a flow opening at 302. The pump reservoir is fluidly coupled to the fluid tank at 304 through the timing reservoir via a return line. For example, the timing reservoir 110 is provided, including the flow opening 112 / 212. The pump reservoir 106 is fluidly coupled to the fluid tank 102 through the timing reservoir 110 via the return line 105 / 205.

[0040] The pump is activated at 306 to operate the hydraulic system in a normal state. In the normal state, a first portion of fluid is delivered from the pump reservoir to the valve via the pressure line. Furthermore, a second portion of fluid is delivered from the pump reservoir to the tank through the return line via the flow orifice and the timing reservoir.

[0041] The pump is deactivated at 308 to operate the hydraulic system in a purge state. In the purge state, a first negative pressure develops in the pump and in a line connecting the pump to the pump reservoir. In some embodiments, a direction of rotation of the pump may be reversed to create the first negative pressure or otherwise increase an absolute value of the first negative pressure. The first negative pressure creates a second negative pressure in the pump reservoir, the valve, and the pressure line. The second negative pressure purges the valve and purges the pressure line for a first time after the pump is deactivated, as described above.

[0042] A third negative pressure develops in the return line. This third negative pressure draws exhaust reductant from the return line through the timing reservoir and flow orifice into the pump reservoir. This third negative pressure continues to draw air from the fluid tank into the pump reservoir for a second time after the pump is turned off, purging the return line. The first negative pressure continues to draw fluid into the fluid tank for a third time to purge the pump reservoir with air after the return line has been purged. Purging the pump reservoir fills the valve, discharge line, and pump reservoir with air to atmospheric pressure, leaving no fluid in the pump reservoir.

[0043] The timing reservoir (e.g., timing reservoir 110), the flow opening (e.g., flow opening 112 / 212), and / or the return line (e.g., return line 105 / 205) are configured such that the second time is longer than the first time. For example, the timing reservoir may be configured to hold a volume of fluid to enable flushing of the return line during the second time.

[0044] In some embodiments, the flow opening has a diameter configured to enable flushing of the return line during the second time. The flow opening may enable bidirectional fluid flow. For example, the flow opening may not have a check valve, allowing fluid to flow back and forth between the fluid tank and the pump reservoir.

[0045] In some embodiments, the pressure line has a first length and the return line has a second length that is greater than the first length. The second length may be configured to enable flushing of the return line during the second time. For example, a ratio between a return line volume of the return line and a pressure line volume of the pressure line is in the range of 30% to 35%, including all ranges and values ​​therebetween. Furthermore, an end of the return line connected to the fluid tank may be disposed within the fluid tank such that it is positioned above a surface of the fluid contained in the fluid tank.

[0046] Each of the operations included in method 300 or any other method described herein may be performed by a control circuit, which may, for example, comprise a controller. The control circuit may be operatively coupled to the hydraulic system 100 or any other hydraulic system described herein to control its operation, for example, to enable flushing thereof as described herein. The controller may comprise a memory, for example, a non-transitory computer-readable medium, storing instructions or algorithms corresponding to the operations of method 300. The controller may also include a processor for interpreting and executing the instructions or algorithms stored in the memory. The controller may also comprise a sensor (e.g., for sensing various parameters of the hydraulic system) and / or a transceiver (e.g.,for transmitting communication signals to the hydraulic system (e.g., pump 104 of hydraulic system 100). In various embodiments, the control device may also include one or more circuits to control the operation of the pump or other components included in the hydraulic system.

[0047] As used herein, the singular forms "a" and "the" include the plural forms unless the context expressly indicates otherwise. Thus, for example, the term "an element" shall mean a single element or a combination of elements, and "a material" shall mean one or more materials or a combination thereof.

[0048] As used herein, the terms "about" and "approximately" generally mean plus or minus 10% of the stated value. For example, "about 0.5" would include the values ​​0.45 and 0.55, "about 10" would include 9 to 11, and "about 1000" would include 900 to 1100.

[0049] The terms "coupled," "connected," and the like, as used herein, mean the direct or indirect connection of two elements to one another. This connection can be stationary (e.g., permanent) or movable (e.g., removable or detachable). This connection can be achieved by the two elements, or the two elements and any other intermediate elements, being integrally formed as a unitary body, or by the two elements, or the two elements and any other intermediate elements, being fastened to one another.

[0050] It should be understood that the construction and arrangement of the various exemplary embodiments are for illustrative purposes only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art will readily appreciate upon reading this disclosure that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and portions of the various elements, values ​​of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Other substitutions, modifications, changes, and omissions may also be made in the construction, operating conditions, and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

[0051] Throughout this specification, reference to "one embodiment" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. When the phrases "in an embodiment" and similar language appear in this specification, such reference is not necessarily always referring to one and the same embodiment. Likewise, use of the term "implementation" means an implementation that has a particular feature, structure, or characteristic described in connection with one or more embodiments of the present disclosure; however, in the absence of an explicit correlation to indicate otherwise, an implementation may be associated with one or more embodiments.

[0052] Although this specification contains many specific embodiment details, these should not be considered limitations on the scope of all inventions or the claims, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.In addition, although the foregoing features may be described as functioning in certain combinations and may also be initially claimed as such, in some cases one or more features from a claimed combination may be singled out from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claims

[1] Hydraulic system (100), comprising: a pump (104); a pump reservoir (106); a supply line (101) fluidly coupling a fluid tank (102) to the pump (104), wherein the supply line (101) is constructed to receive a fluid from the fluid tank (102); a valve (108) in fluid communication with the pump reservoir (106); a pressure line (103) fluidly coupling the pump reservoir (106) to the valve (108); a timing reservoir (110) having a flow opening (112; 212); and a return line (105; 205) designed to fluidly connect the pump reservoir (106) to the fluid tank (102) via the timing reservoir (110), wherein the hydraulic system (100) is adapted to switch between a normal state and a flushing state, wherein in the normal state: the pump (104) is switched on, a first part of the fluid from the fluid tank (102) is supplied via the pressure line (103) from the pump reservoir (106) to the valve (108) and a second part of the fluid from the pump reservoir (106) is supplied through the return line (105; 205) via the flow opening (112; 212) and the timing reservoir (110) to the fluid tank (102), and where in the flushing state: a first negative pressure is created at an outlet of the pump (104), the first negative pressure generating a second negative pressure in the pump reservoir (106), in the valve (108) and in the pressure line (103), the second negative pressure flushing the valve (108) and the pressure line (103) in a first time after the pump (104) is switched off, and a third negative pressure is created in the return line (105; 205), the third negative pressure drawing fluid from the return line (105; 205) via the timing reservoir (110) and the flow opening (112; 212) into the pump reservoir (106); the third negative pressure also drawing air from the fluid tank (102) into the pump reservoir (106) for a second time after the pump (104) is turned off, thereby purging the return line (105; 205); the second time being longer than the first time; the first negative pressure continuing to draw fluid into the fluid tank (102) and purge the pump reservoir (106) with the air for a third time after the return line (105; 205) has been purged; wherein flushing the pump reservoir (106) fills the valve (108), the pressure line (103) and the pump reservoir (106) with air to atmospheric pressure so that no fluid remains in the pump reservoir (106). [2] The hydraulic system (100) of claim 1, wherein at least one of the following: the timing reservoir (110), the flow port (112; 212), and the return line (105; 205) is or are configured to cause the second time to be longer than the first time. [3] The hydraulic system (100) of claim 2, wherein the timing reservoir (110) is configured to hold a volume of fluid to enable flushing of the return line (105; 205) in the second time. [4] The hydraulic system (100) of claim 3, wherein the flow opening (112; 212) has a diameter configured to allow flushing of the return line (105; 205) in the second time. [5] The hydraulic system (100) of claim 3, wherein the flow opening (112; 212) does not have a check valve, so that the flow opening (112; 212) allows bidirectional flow of fluid between the pump reservoir (106) and the fluid tank (102). [6] The hydraulic system (100) of claim 1, wherein the fluid is an exhaust gas reducing agent. [7] The hydraulic system (100) of claim 1, wherein the fluid comprises a diesel emissions fluid. [8] The hydraulic system (100) of claim 2, wherein the pressure line (103) has a first length and the return line (105; 205) has a second length greater than the first length, the second length being configured to enable flushing of the return line (105; 205) in the second time. [9] Hydraulic system (100) according to claim 8, wherein a ratio between a return line volume of the return line (105; 205) and a pressure line volume of the pressure line (103) is in the range of 30% to 35% inclusive. [10] A device for flushing a hydraulic system (100), comprising a fluid tank (102) containing a fluid, a pump (104), a pump reservoir (106), a supply line (101) fluidly coupling the fluid tank (102) to the pump (104), a valve (108) fluidly connected to the pump reservoir (106), and a pressure line (103) fluidly coupling the pump reservoir (106) to the valve (108), the device comprising: a timing reservoir (110) having a flow opening (112; 212); and a return line (105; 205) fluidly coupling the pump reservoir (106) to the fluid tank (102) via the timing reservoir (110), wherein the device is designed to enable the hydraulic system (100) to change between a normal state and a flushing state, wherein in the normal state: the pump (104) is switched on, a first portion of the fluid is delivered from the pump reservoir (106) via the pressure line (103) to the valve (108) and a second portion of the fluid is delivered from the pump reservoir (106) through the return line (105; 205) via the flow opening (112; 212) and the timing reservoir (110) to the tank (102), and where in the flushing state: a first negative pressure is created at an outlet of the pump (104), the first negative pressure generating a second negative pressure in the pump reservoir (106), in the valve (108) and in the pressure line (103), the second negative pressure flushing the valve (108) and the pressure line (103) in a first time after the pump (104) is switched off, and a third negative pressure is created in the return line (105; 205), the third negative pressure drawing the fluid from the return line (105; 205) via the timing reservoir (110) and the flow opening (112; 212) into the pump reservoir (106), the third negative pressure also drawing air from the fluid tank (102) into the pump reservoir (106) in a second time from the switching off of the pump (104), so that the return line (105; 205) is flushed, the first negative pressure continuing to draw the fluid into the fluid tank (102) for a third time after the flushing of the pump reservoir (106) and flushing the pump reservoir (106) with the air, the flushing of the pump reservoir (106) closing the valve (108), the pressure line (103) and the Pump reservoir (106) is filled with air to atmospheric pressure so that no fluid remains in the pump reservoir (106), wherein at least one of the following: the timing reservoir (110), the flow opening (112; 212) and the return line (105; 205) is configured such that the second time is longer than the first time. [11] The apparatus of claim 10, wherein the timing reservoir (110) is configured to hold a volume of fluid to enable flushing of the return line (105; 205) in the second time. [12] The device of claim 11, wherein the flow opening (112; 212) has a diameter designed to enable flushing of the return line (105; 205) in the second time. [13] The device of claim 11, wherein the flow opening (112; 212) does not have a check valve, so that the flow opening (112; 212) allows bidirectional flow of the fluid between the pump reservoir (106) and the fluid tank (102). [14] The apparatus of claim 10, wherein the fluid is an exhaust gas reducing agent. [15] The apparatus of claim 10, wherein the fluid comprises a diesel emission fluid. [16] The apparatus of claim 10, wherein the pressure line (103) has a first length and the return line (105; 205) has a second length greater than the first length, the second length being configured to enable flushing of the return line (105; 205) in the second time. [17] Apparatus according to claim 16, wherein a ratio between a return line volume of the return line (105; 205) and a pressure line volume of the pressure line (103) is in the range of 30% to 35% inclusive. [18] The apparatus of claim 10, wherein one end of the return line (105; 205) connected to the fluid tank (102) is disposed within the fluid tank (102) so as to be positioned above a surface of the fluid contained in the fluid tank (102). [19] A method (300) for flushing a hydraulic system (100), comprising a fluid tank (102), a pump (104), a pump reservoir (106), a supply line (101) fluidly coupling the fluid tank (102) to the pump (104), a valve (108) in fluid communication with the pump reservoir (106), a pressure line (103) fluidly coupling the pump reservoir (106) to the valve (108), a return line (105; 205), a timing reservoir (110), and a flow opening (112; 212), the method (300) comprising: Activating the pump (104) to operate the hydraulic system (100) in a normal state, wherein the pump reservoir (106) is in fluid communication with the fluid tank (102) through the timing reservoir (110) and the flow opening (112; 212) via the return line (105; 205), wherein a first portion of the fluid is delivered from the pump reservoir (106) to the valve (108) via the pressure line (103), and wherein a second portion of the fluid is delivered from the pump reservoir (106) to the tank (102) through the return line (105; 205) via the flow opening (112; 212) and the timing reservoir (110); and Deactivating the pump (104) to operate the hydraulic system (100) in a flushing state, wherein a first negative pressure develops at an outlet of the pump (104), the first negative pressure creates a second negative pressure in the pump reservoir (106), the valve (108) and the pressure line (103), the second negative pressure flushing the valve (108) and the pressure line (103) in a first time from the deactivation of the pump (104), and a third negative pressure develops in the return line (105; 205), the third negative pressure flushing the fluid from the return line (105; 205) via the timing reservoir (110) and the flow opening (112; 212) into the pump reservoir (106), wherein the third negative pressure also draws air from the fluid tank (102) into the pump reservoir (106) in a second time from the switching off of the pump (104) so ​​that the return line (105; 205) is flushed, the second time being longer than the first time, the first negative pressure continuing to draw the fluid into the fluid tank (102) and flushing the pump reservoir (106) with the air for a third time after flushing the return line (105; 205), wherein the flushing of the pump reservoir (106) vents the valve (108), the pressure line (103) and the pump reservoir (106) to atmospheric pressure so that no fluid in the pump reservoir (106) remains. [20] The method (300) of claim 19, wherein at least one of the timing reservoir (110), the flow opening (112; 212) and the return line (105; 205) is configured such that the second time is longer than the first time. [21] The method (300) of claim 20, further comprising: Reversing a flow of the pump (104) to create the first negative pressure at the outlet of the pump (104). [22] The method (300) of claim 20, wherein the timing reservoir (110) is configured to hold a volume of fluid to enable flushing of the return line (105; 205) in the second time. [23] The method (300) of claim 20, wherein the flow opening (112; 212) has a diameter configured to enable flushing of the return line (105; 205) in the second time. [24] The method (300) of claim 23, wherein the flow opening (112; 212) does not have a check valve, such that the flow opening (112; 212) allows bidirectional flow of the fluid between the pump reservoir (106) and the fluid tank (102). [25] The method (300) of claim 20, wherein the pressure line (103) has a first length and the return line (105; 205) has a second length greater than the first length, the second length being configured to enable flushing of the return line (105; 205) in the second time. [26] A control circuit for controlling a hydraulic system (100) to enable its flushing, the hydraulic system (100) comprising a fluid tank (102) containing a fluid, a pump (104), a pump reservoir (106), a supply line (101) fluidly coupling the fluid tank (102) to the pump (104), a valve (108) in fluid communication with the pump reservoir (106), a pressure line (103) fluidly coupling the pump reservoir (106) to the valve (108), a return line (105; 205), a timing reservoir (110), and a flow opening (112; 212), the control circuit comprising: a control device adapted to be operatively coupled to the hydraulic system (100), the control device further adapted to control the operation of the hydraulic system (100) such that a change of the hydraulic system (100) between a normal state and a flushing state is possible, where in normal condition: the control device activates the pump (104) so ​​that a first part of the fluid is delivered from the pump reservoir (106) via the pressure line (103) to the valve (108) and a second part of the fluid is delivered from the pump reservoir (106) through the return line (105; 205) via the flow opening (112; 212) and the timing reservoir (110) to the tank (102), and where in the flushing state: the control device deactivates the pump (104) so ​​that a first negative pressure develops at an outlet of the pump (104), the first negative pressure generating a second negative pressure in the pump reservoir (106), the valve (108) and the pressure line (103), the second negative pressure flushing the valve (108) and the pressure line (103) in a first time from the switching off of the pump (104), and a third negative pressure is created in the return line (105; 205), the third negative pressure drawing the fluid from the return line (105; 205) via the timing reservoir (110) and the flow opening (112; 212) into the pump reservoir (106), the third negative pressure also drawing air from the fluid tank (102) into the pump reservoir (106) in a second time from the switching off of the pump (104), so that the return line (105; 205) is flushed, the first negative pressure continuing to draw the fluid into the fluid tank (102) and flushing the pump reservoir (106) with the air for a third time after the flushing of the return line (105; 205), the flushing of the pump reservoir (106) closing the valve (108), the pressure line (103) and the pump reservoir (106) is vented to atmospheric pressure so that no fluid remains in the pump reservoir (106).

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