# US 10,502,108 B2 · Exhaust gas purification system for construction machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,108 B2 - Document ID: US10502108B2 - Status: Granted - Kind: B2 - Application number: 16/080,368 - Filed: 2017-03-10 - Published: 2019-01-24 - Granted: 2019-12-10 - Earliest claimed: 2016-08-02 - Assignees: Hitachi Construction Machinery Co., Ltd. - Applicants: Hitachi Construction Machinery Co., Ltd. - Inventors: Masatoshi Sakurai - Web page: https://patentgrep.com/patent/US10502108B2 ## CPC - F01N 3/04: using liquids - B01D 53/90: Injecting reactants - B01D 53/94: by catalytic processes - B01D 53/9409: {Nitrogen oxides} - E02F 9/00: Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00 (laying-out or take-up devices for trailing electric cables B66C) - E02F 9/0883: {Tanks, e.g. oil tank, urea tank, fuel tank (for vehicles in general B60K15/00)} - F01N 3/08: for rendering innocuous (using electric or electrostatic separators F01N3/01; chemical aspects B01D53/92) - F01N 3/0814: {combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts} - B01D 2251/2067: Urea - E02F 3/32: working downwardly and towards the machine, e.g. with backhoes - E02F 9/2025: {Particular purposes of control systems not otherwise provided for (E02F3/16, E02F3/26, sub-groups of E02F3/43, E02F3/651, sub-groups of E02F3/84, E02F3/907, E02F5/145 take precedence)} - F01N 2260/024: using a liquid - F01N 2570/14: Nitrogen oxides - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) ## Abstract An exhaust gas purification system for a construction machine prevents deterioration of an aqueous urea solution remaining in a conduit of an aqueous urea solution replenishing circuit after replenishment. An aqueous urea solution return circuit returns, to an aqueous urea solution tank, an excessive aqueous urea solution that has not been injected from an aqueous urea solution injection device into the exhaust gas, and is provided with a first return conduit that connects the aqueous urea solution injection device to the aqueous urea solution tank and a second return conduit that connects the aqueous urea solution injection device to a conduit of an aqueous urea solution replenishing circuit. An injection valve opening pressure of a first check valve provided in the first return conduit is set higher than an injection valve opening pressure of a second check valve provided in the second return conduit. ## Claims ### Claim 1 An exhaust gas purification system for a construction machine, comprising: an aqueous urea solution tank that is disposed in an upper swing structure of the construction machine; an aqueous urea solution injection device that injects an aqueous urea solution into exhaust gas from an engine; and an aqueous urea solution supply circuit in which an aqueous urea solution pump for supplying the aqueous urea solution from the aqueous urea solution tank to the aqueous urea solution injection device is disposed, wherein the exhaust gas purification system for the construction machine comprises: an aqueous urea solution coupler that is provided at a lower position than a position of the aqueous urea solution tank and that is disposed outside of the construction machine; an aqueous urea solution replenishing circuit that replenishes the aqueous urea solution tank with the aqueous urea solution through the aqueous urea solution coupler; and an aqueous urea solution return circuit that returns, to the aqueous urea solution tank, an excessive aqueous urea solution that has not been injected from the aqueous urea solution injection device into the exhaust gas, the aqueous urea solution return circuit includes: a first return conduit that connects the aqueous urea solution injection device to the aqueous urea solution tank; a second return conduit that connects the aqueous urea solution injection device to the aqueous urea solution replenishing circuit; a first check valve that is disposed in the first return conduit and that prevents a back flow of the aqueous urea solution; and a second check valve that is disposed in the second return conduit and that prevents the back flow of the aqueous urea solution, and an injection valve opening pressure of the first check valve is set higher than an injection valve opening pressure of the second check valve. ### Claim 2 (depends on 1) The exhaust gas purification system for the construction machine according to claim 1, wherein the aqueous urea solution replenishing circuit includes: an aqueous urea solution replenishing conduit that connects the aqueous urea solution tank to the aqueous urea solution coupler; and a solenoid valve provided in the aqueous urea solution replenishing conduit, and the exhaust gas purification system for the construction machine further comprises: an aqueous urea solution replenishing switch that instructs that aqueous urea solution replenishing work for replenishing the aqueous urea solution tank with the aqueous urea solution is underway; a water level sensor that detects a water level of the aqueous urea solution tank; and a controller that determines whether the aqueous urea solution replenishing work is underway and whether the aqueous urea solution tank has turned into a full water level state on the basis of signals from the aqueous urea solution replenishing switch and the water level sensor, that controls the solenoid valve to be closed in a case in which the aqueous urea solution replenishing work is underway and in which the aqueous urea solution tank has turned into the full water level state, and that controls the solenoid valve to be opened after end of the aqueous urea solution replenishing work. ### Claim 3 (depends on 1) The exhaust gas purification system for the construction machine according to claim 1, further comprising: a water level sensor that detects a water level of the aqueous urea solution tank; and an aqueous urea solution replenishing lamp that notifies an operator that the aqueous urea solution tank has turned into the full water level state; and a controller that controls the aqueous urea solution replenishing lamp to be lit up in a case in which the aqueous urea solution tank has turned into the full water level on the basis of a signal from the water level sensor.