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We study constraints on f(R) dark energy models from solar system experimentscombined with experiments on the violation of equivalence principle. When themass of an equivalent scalar field degree of freedom is heavy in a region withhigh density, a spherically symmetric body has a thin-shell so that aneffective coupling of the fifth force is suppressed through a chameleonmechanism. We place experimental bounds on the cosmologically viable modelsrecently proposed in literature which have an asymptotic form f(R)=R-lambda R_c[1-(R_c/R)^{2n}] in the regime R >> R_c. From the solar-system constraints onthe post-Newtonian parameter gamma, we derive the bound n>0.5, whereas theconstraints from the violations of weak and strong equivalence principles givethe bound n>0.9. This allows a possibility to find the deviation from theLambdaCDM cosmological model. For the model f(R)=R-lambda R_c(R/R_c)^p with0<p<1 the severest constraint is found to be p<10^{-10}, which shows that thismodel is hardly distinguishable from the LambdaCDM cosmology.

Solar system and equivalence principle constraints on f(R) gravity by chameleon approach