Variable compression device and engine system
A variable compression device includes a piston rod, a first fluid chamber configured to move the piston rod in a direction in which a compression ratio is increased by supplying a pressurized working fluid thereto, a regulation member configured to regulate movement of the piston rod in a direction in which a compression ratio is increased, a second fluid chamber provided between the piston rod and the regulation member and configured to store the working fluid, a supply flow path configured to guide the working fluid supplied to the second fluid chamber, a discharge flow path configured to guide the working fluid discharged from the second fluid chamber, and a flow rate regulation unit provided in the discharge flow path and configured to regulate a flow of the working fluid when the piston rod approaches the regulation member.
1. A variable compression device that is configured to change a compression ratio in a combustion chamber of an engine, the variable compression device comprising:
a piston rod;
a first fluid chamber which is configured to move the piston rod in a direction in which a compression ratio is increased by supplying a pressurized working fluid thereto;
a regulation member which is configured to regulate movement of the piston rod in a direction in which a compression ratio is increased;
a second fluid chamber which is provided between the piston rod and the regulation member and is configured to store the working fluid;
a supply flow path which is configured to guide the working fluid supplied to the second fluid chamber;
a discharge flow path which is configured to guide the working fluid discharged from the second fluid chamber, a portion of the discharge flow path being formed in the regulation member; and
a flow rate regulation unit which is provided in the discharge flow path and is configured to regulate a flow of the working fluid when the piston rod approaches the regulation member.
2. The variable compression device according to claim 1 , wherein the flow rate regulation unit includes a weight member which is movable together with the piston rod, and a valve which is moved in a valve closing direction by movement of the weight member.
3. The variable compression device according to claim 2 , wherein the flow rate regulation unit includes a biasing member that is configured to bias the weight member in a valve opening direction.
4. The variable compression device according to claim 1 , wherein a portion of the working fluid supplied to the first fluid chamber is supplied to the second fluid chamber.
5. The variable compression device according to claim 1 , further comprising:
a fluid chamber forming member which forms a portion of the first fluid chamber; and
an absorption member which is fixed to the regulation member or the piston rod, and is configured to absorb collision energy between the regulation member and the piston rod by elastic deformation.
6. The variable compression device according to claim 5 , further comprising:
a fixing member which is configured to fix the regulation member to the fluid chamber forming member,
wherein the fixing member includes a shaft portion which is inserted into the regulation member and the fluid chamber forming member, and a head portion which is fixed to the shaft portion and is disposed separately from the regulation member, and
the absorption member is provided between the regulation member and the head portion.
7. The variable compression device according to claim 5 , wherein the absorption member is provided between the regulation member and the piston rod.
8. The variable compression device according to claim 7 , wherein the regulation member includes a concave portion to which the absorption member is fitted.
9. An engine system comprising the variable compression device according to claim 1 .